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Gasification kinetics of western Canadian coals Yang, Yongxin 1991

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GASIFICATION KINETICS OF W E S T E R N C A N A D I A N C O A L S By Yongxin Yang B. Eng. Hunan University A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in THE FACULTY OF GRADUATE STUDIES CHEMICAL ENGINEERING We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA August, 1991 0 Yongxin Yang, 1991 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. The University of British Columbia Vancouver, Canada Department Date DE-6 (2/88) Abstract The gasification reactivities of eight types of Western Canadian coals ranking from bitu-minous to lignite were investigated. The chars derived from these coals under the same pyrolysis conditions were gasified with steam in a stirred-bed reactor, and the product gas was analysied on a gas chromatograph. The partial pressure of steam was 0.3 atm for all runs; temperature varied from 870-930°C; and particle diameter from 1.13-1.53 mm. BET surface areas of the chars were measured using iV2- Scanning electron microscopy was employed to observe the surface structure of the char. The carbon conversion versus time curves are generally S-Shaped except for the least reactive coal chars. It is evident that the reactivity of a char increases as the rank of its parent coal decreases. This relationship was indicated by correlations of the time to reach 50% conversion with the carbon contents and fuel ratios of the original coals. The influence of catalytic species, such as CaO, MgO etc. in the mineral matter of the coal on reactivity of was also shown. The maximum rate for each run was observed to he between 10-25% carbon conversion. The random pore and random capillary models were found to be not suitable to represent the experimental data of this work, whereas the modified volumetric model (MVM) was capable to do so up to X = 0.78, especially for results of less reactive coal chars. The rate constant k evaluated from the MVM was closely related to BET surface area and moisture holding capacity of the char. The temperature dependence was not investigated in detail, but appeared similar for the four chars tested, which suggests that the gasification mechanism for each coal are similar. The fitting of Fung and Kim's correlation to the experimental data gave a good result ii with the correlation coefficient of 0.87-0.88. A correlation proposed by Sakata et al. was proved to predict the reactivities of these chars reasonably well. However, the rate constants measured by Sakata are 2.7-5.5 times as high as the values obtained in this work. By normalizing time with the time to reach fifty percent conversion a unified conver-sion function was obtained for all the present results up to about 70% percent conversion. in Table of Contents Abstract ii List of Tables viii List of Figures xii Nomenclature xvi Acknowledgement xx 1 Introduction 1 1.1 History and Motives of Coal Gasification 1 1.2 Basic Aspects about Coal Gasification Process 3 1.3 Background of Kinetic Study 5 1.4 Approach and Objectives 7 2 Literature Review 9 2.1 Coal Characteristics 9 2.1.1 Classification 9 2.1.2 Organic Chemical Structure 11 2.1.3 Pore Structure 14 2.2 The Kinetics of Char Gasification 20 2.2.1 General Remarks 20 2.2.2 Surface Mechanism for Char-Steam Reaction 22 iv 2.2.3 Mass Transfer 25 2.3 Modeling for Solid-Gas Reaction 29 2.3.1 Basic Modeling Concepts 29 2.3.2 Model Review 32 2.3.3 Correlations for Char Gasification 41 3 Experimental Apparatus and Procedure 46 3.1 The Apparatus for Gasification 46 3.1.1 The Reactant Generating and Transport Facility 46 3.1.2 The Gasifier 48 3.1.3 The Product Gas Handling Facility 51 3.1.4 The Control Panel ' 53 3.2 Experimental Techniques 55 3.2.1 The preparation of chars 56 3.2.2 Gasification 57 3.2.3 Product Gas Analysis 58 3.2.4 BET Surface Area Measurement 60 3.2.5 Scanning Electron Microscopy (SEM) 61 4 Experimental Results and Discussion 62 4.1 Introduction 62 4.2 Characterization of The Coal Samples 63 4.3 Analysis of Chars 66 4.3.1 Chemical Composition of Char 68 4.3.2 BET Surface Area 68 4.3.3 SEM Examination 69 4.4 Gasification Experiments on the Different Types of Coal 76 v 4.4.1 Results 76 4.4.2 Discussion 81 4.5 Experiments at Different Temperatures 86 4.5.1 Results 86 4.5.2 Discussion 90 4.6 Experiments with Different Particle Sizes 91 4.6.1 Results 91 4.6.2 Discussion 91 5 Model Testing 95 5.1 Introduction 95 5.2 Testing of The Random Capillary and Random Pore Models 96 5.2.1 The Model Expressions 96 5.2.2 Testing Results and Discussion 99 5.3 Testing of The Modified Volumetric Model 102 5.3.1 The Model Expression 102 5.3.2 Testing Results and Discussion 106 5.4 Correlating the Reactivity of Char 126 5.5 Unification of Coal Gasification Data 129 6 Conclusion and Future Work 136 6.1 Conclusion 136 6.2 Recommendation for Future Work 139 Bibliography 141 Appendices 151 vi A Calculation for Steam Partial Pressure 151 B The Algorithm for Computing Carbon Conversion X 153 C Calibration of G C 156 D Evaluation of External Mass Transfer Rate 160 E Ash Composition Data 163 F Experimental Conditions and Results 165 v i i List of Tables 1.1 The Coals Studied in This Work 7 2.1 Summary of Proposed Models 12 2.2 Moisture-holding Capacity for the Coals/Char (g/g of db) 20 3.1 GC Operation Conditions 59 4.1 Ultimate Analysis for the Coals Employed 63 4.2 Proximate Analysis for the Coals Employed 64 4.3 Mineral Matter Content of The Coals 65 4.4 The Catalytic Metal Oxides Composition of Ash (wt% db) 66 4.5 Composition of Chars (wt% As Received) 68 4.6 Surface Area of Chars (m2/g) 69 5.1 Summary of The Fitting Results 109 5.2 Activation Energies and Frequency Factors for The Chars 117 5.3 Operating Conditions of Both TGA and SBR 120 5.4 Comparison of Steam Gasification Results Measured by Sakata et al and This Research for Eight Kind of Canadian Coals 121 5.5 The Linear Regression Results 122 5.6 Average Reactivity for Each Run (dp = 0.85 — 1.40mm) 134 C.l Composition of Gas Mixtures 156 C.2 Response Factor 157 vm E. l The Metal Oxides Composition of Ash (wt%) . 164 F. l Summary of Operating Conditions and Results for All Gasification Runs 166 F.2 R U N # 31 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results 167 F.3 R U N # 32 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results 168 F.4 R U N # 33 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results 169 F.5 R U N # 36 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results 170 F.6 R U N # 37 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results 171 F.7 R U N # 43 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results 172 F.8 R U N # 44 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results: 173 ix F.9 R U N # 45 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results 174 F.10 R U N # 47 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results 175 F . l l R U N # 49 (a) Composition of Products Gas, (b) Converted C, H, O and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results. 176 F.12 R U N # 51 (a) Composition of Products Gas, (b) Converted C, H, O and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results 177 F.13 R U N # 54 (a) Composition of Products Gas, (b) Converted C, H, O and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results 178 F.14 R U N # 55 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results 179 F.15 R U N # 57 (a) Composition of Products Gas, (b) Converted C, H, O and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results 180 F.16 R U N # 58 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results 181 x F.17 R U N # 59 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results 182 F.18 R U N # 60 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results 183 F.19 R U N # 62 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results 184 F.20 R U N # 64 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results 185 F.21 R U N # 65 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results 186 F.22 Carbon Conversion Predicted by The MVM for Each Run 187 F.23 A Demonstration of Experimental Reproducibility 191 x i List of Figures 1.1 Applications of Coal Gasification 2 2.1 Basic Chemical Structure in Coal: (a) polynuclear aromatic (b - basal carbon, e - edge carbon), (b) hydroaromatic, (c) arenes, (d) methylene bridge, (e) substituted aromatics, (f) heterocyclics 11 2.2 Model Structure Proposed by Wiser 13 2.3 The Three Ideal Zones Representing the Change of Reaction Rate of a Porous Char with Temperature 21 2.4 Rate-conversion Curves According to the Model of Simons and Co-worker 37 2.5 Development of the reaction surface with conversion according to the ran-dom pore model, compared with grain model (n = 2/3) and Petersen model for e0 = 0.26, L0 = 3.14 x 106 cm/cm3, S0 = 2.425 cm2/cm3. . . . 38 3.1 Flow Sheet of The Gasification System for This Study 47 3.2 Calibration Curve for Nitrogen Rotamenter 49 3.3 Calibration Curve for Water Rotamenter 50 3.4 Engineering Drawing of The Cooling Section of The Gasifier 52 3.5 Mechanical Structure of The Stirrer Head 53 3.6 Engineering Drawing of the Gasifier and Its Live Flange 54 4.1 Mass Loss% versus Carbon Content of Parent Coal 67 4.2 Surface Area versus Carbon Content of Parent Coal 67 xii 4.3 SEM Photomicrographs for Three Kinds of Chars at Low Magnification (1-Costello, 2-0bed Mountain, 3-Gregg River) 70 4.4 SEM Photomicrographs for Three Kinds of Chars at Medium Magnifica-tion (1-Costello, 2-Obed Mountain, 3-Gregg River) 72 4.5 SEM Photomicrographs for Three Kinds of Chars at High Magnification (1-Costello, 2-Obed Mountain, 3-Gregg River) 74 4.6 Carbon Conversion versus Time for Runs of the Eight Chars. Temperature =930°C 77 4.7 Change of Rate with Carbon Conversion for Eight Chars. Temperature=930 °C. 79 4.8 The Relationship between Half-life and Fuel Ratio 80 4.9 The Relationship between Half-life and Carbon Content of Parent Coal. . 81 4.10 The Relationship between Oxygen Content of Coals and Carbon Content of Parent Coal 82 4.11 The Relationship between Half-life and CaO + MgO content 84 4.12 The Relationship between Half-life and CaO + MgO +Na20 + K20 content. 84 4.13 Effect of Gasification Temperature on C Conversion of Costello Coal. . . 87 4.14 Effect of Gasification Temperature on the Rate of C Conversion of Costello Coal 87 4.15 Effect of Gasification Temperature on C Conversion of Obed Mountain Coal. 88 4.16 Effect of Gasification Temperature on the Rate of C Conversion of Obed Mountain Coal 88 4.17 Effect of Gasification Temperature on C Conversion of Gregg River Coal. 89 4.18 Effect of Gasification Temperature on the Rate of C Conversion of Gregg River Coal 89 4.19 Effect of Particle Size on C Conversion of Obed Mountain Coal 92 c 4.20 Effect of Particle Size on C Conversion of Highvale Coal 93 xiii 5.1 The Applicability Check of RCM and RPM to The Rate Data of The Chars Listed (a) 100 5.2 The Applicability Check of RCM and RPM to The Rate Data of The Chars Listed (b) 101 5.3 The Applicability Check of MVM to The Rate Data of The Chars Listed (a) 107 5.4 The Applicability Check of MVM to The Rate Data of The Chars Listed (b) 108 5.5 Comparison between Measured X-t and Predicted by The MVM for Runs at Temperature = 870°C (a) I l l 5.6 Comparison between Measured X-t and Predicted by The MVM for Runs at Temperature = 870°C (b) 112 5.7 Comparison between Measured X-t and Predicted by The MVM for Runs at Temperature = 930°C (a) 113 5.8 Comparison between Measured X-t and Predicted by The MVM for Runs at Temperature = 930°C (b) 114 5.9 Comparison between Measured dX/dt vs. X and Predicted by The MVM for Runs at Temperature = 930°C (a) 115 5.10 Comparison between Measured dX/dt vs. X and Predicted by The MVM for Runs at Temperature = 930°C (b) 116 5.11 Arrhenius-type Plot of Mean Rate Constant by The MVM for The Chars 118 5.12 The Relation between Mean Rate Constant Both Measured by TGA & SBR at 870° and Initial Surface Area of The Chars 123 5.13 The Relation between Mean Rate Constant Both Measured by TGA & SBR at 870° and Moisture-holding Capacity of The Chars 124 x i v 5.14 Relation between Reactivity of The Chars and Carbon Content of Parent Coal. Temperature = 930°C 128 5.15 Validity of The Correlation for Steam Gasification Reactivity of The Coals Tested in This Study, for Temperature= 930°C 130 5.16 Unification of Coal Gasification Data from This Research 133 5.17 Reactivity Comparison between Measured at X = 0.5 and Estimated by Using Unification Results 135 xv Nomenclat x v i A a constant in Eq'ns 5.3 & 5.4 Ao Avogadro's Number, 6.023 xlO 2 3 Aa apparent frequency factor 1/min At true frequency factor 1/min B a constant in Eq'n 5.3 &; 5.4 Bo, Bi moments of probability desity in RCM Bo Boltzmann constant C local reactant gas concentration mo//m3, g C constant related to the heat of adsorption and liquefaction of the gas cb concentration of reactant gas in the bulk phase mol/m3,g Cdaf carbon content on dry ash free basis c> local concentration for gas i g/m3 concentration of reactant gas at external surface mol/m3 [Ct] active site concentration sites/m2 D diffusivity m2 / s Dh2 binary diffusion coefficient of reactant gas (1) and inert gas (2) m2 / s Da activated diffusivity m2/s D°a activated diffusion constant De effective diffusivity m2 / s Dk Knudsen diffusivity m? / s Dm Molecular diffusivity m2 / s Ea apparent activation energy kJ/mol Et true activation energy kJ/mol AH enthalpy kJ/mol J molar flux from bulk phase to partical surface mol/s • m KT total rate constant for Johnson's model U initial length of overlapped system per unit volume M molecular weight g/mol Mc mass of carbon atom gj atom N{ the mole number of i component mol {Nc)chaT the moles of carbon in initial char mol (Nc)rec the moles of carbon in receiver at end of gasification mol P pressure atm Po satuation pressure of the adsorbate at the temperature of adsorption atm Q activation energy of diffusion kJ/mol R correlation coefficient R global intrinsic surface rate g/m2 • s Rb global intrinsic surface rate evaluated with C = Cb g/m2 • s xvn Rm overall char reactivity on a mass basis g/s • g (Re)p Reynolds Number based on particle diameter Ru average reactivity for a unification curve Rc average reactivity for a particular run 1/s S specific surface area of particle M2/g So initial surface area of particle M2/g Sc Schmidt Number Sh Sherwood Number T gasification temperature K,° C, °R Tp pretreatment temperature °R V total volume of gas adsorbed m 3 Vo molar volume of the adsorbate at T= 273.15.ff and P= latm l/mol Vm volume of gas needed to cover entire adsorbent surface with a complete monolayer. m2 Var variance W the sample weight at a given time g Wo the initial sample weight of char (daf) g X carbon conversion based on mol of element carbon Xb base-carbon (nonvolatile carbon in raw coal) conversion Xf carbon conversion on mass of fixed carbon Xin{ the value of carbon conversion at inflection point Z distance along the pore m a, b constants in MVM ai,a2 coefficients in Eq'ns 5.34, 5.35 b a constant in MVM d pore diameter m dp particle diameter mm dm molecular diameter m fo reactivity factor fi relative reactivity factor k rate constant 1/min k0 pre-exponential factor in Eq'n 2.36 g/m2 • s k0.5 rate constant at Xf = 0.5 1/s ki a constant in Eq'n 5.13 k intrinsic rate constant on a site basis 1/s • (g/ma)m k mean rate constant 1/s kb overall rate constant on a mass basis g/g • s • (g/m3)n km external mass transfer coefficient m/s ks intrinsic rate constant on a area basis g/s • (g/m3)™ • m2 x v i n k(t) rate constant, a founction of reaction time 1/s k(X) rate constant, a founction of conversion 1/Pan • s k(X) rate constant for surface reaction g/m2 • s • Pa" I mean free path= Bo T/A.Ud^P m m true reaction order n apparent reaction order Vi partial pressire for gas i atm, Pa tinf the time needed to reach inflection point min tl/2 half-life (at X = 0.5) min, s U gas velocity mj s V reaction velocity in RCM w mean molecular speed= (8Bo T/TM)0-5 m/s a kinetic parameter in Johnson's model a molecular cross-section area of adsorbate m2 n moisture-holding capacity g/g V effectiveness factor V- pore structure parameter in RPM i> = 5&T * RCM i> pore structure parameter for the master curve e porocity of particle eo initial porocity of particle viscosity of gas kg/m • s P the intrinsic site conversion rate sites/m2 • s Pg density of reactant gas kg/m3 T dimensionless time= t/ti/2 xix Acknowledgement First of all, I wish to express my gratitude to Dr. A.P. Watkinson for his enthusiastic supervision thoughout the course of this work. I gratefully acknowledge that this research was funded in part by a grant from the Energy, Mines and Resources Research Agreement Program. Thanks are also due to the people of Department of Chemical Engineering who have given me assistance for completion of this research. I would like to dedicate this work to my husband Chao Xu, and my parents back in China, for their encouragement, understanding and patience. xx Chapter 1 Introduction 1.1 History and Motives of Coal Gasification The world coal reserves constitute an important source of energy and base chemicals, which account for approximately 83% of all primary energy sources. However coal con-tributes only 34% to the world-wide consumption of fossil energy sources [1]. One effective way of utilizing coal is via coal conversion processes e.g. gasification or liquefaction, by which the solid fuel coal is converted into clean, fuel-rich gaseous or liquid forms. Among the different coal conversion processes, gasification offers special advantages: it is eco-nomic being 60-80% efficient for electricity generation [2]; the nature of gaseous product makes it easy to transport in piplines, it is not expensive or difficult to remove the sul-phur species formed during gasification from the sulphur present in the coal, so that high level enviromental regulations can be met. Gasification of coal has been practiced commercially for nearly 200 years, beginning in 1780 when the Italian priest and scientist Felice Fontana, the father of gasification, for first time noted: "If one quenches glowing coal with distilled water, one obtains ignitable air" [3]. This invention was used within a short time. In the following years, numerous technical advances with regard to this process have been made. In the first half of 20th century, coal was used as the principal source of energy for industry and cities alike. However, the 1940's boom in the production of petroleum and natural gas as well as the 1960's emergance of nuclear power had made coal utilization less significant than 1 Chapter 1. Introduction 2 Coal Heat (allotherrnal) or Lean gas Steam Synthesis gas Gasification Combustion Rower station Chemicals industry Ore Gas supply reduction systems Heating Electricity NH 3 Methanol Petrol Crude iron Heating Figure 1.1: Applications of Coal Gasification ever before. In the mid-1970s, a sharply renewed interest in the world's abundant coal resources was evident with concern over the oil crisis and dwindling supplies of natural gas. The importance of coal for political, economical and energy preservation reasons was acknowledged again. Coal offers the best short term solution to substitute natural gas and oil, while other forms of energy, such as nuclear and solar energy, will be required in the long term. As shown in Figure 1.1, apart from the production of energy in the form of electricity or gaseous fuel, coal gasification has other contributions. The product gas mixture, which contains hydrogen and carbon monoxide, can serve as reducing agents for the direct processing of ores. Alternatively, by purification and conversion of this gas mixture, a synthesis gas can be obtained, which is used as chemical feed stock for production of ammonia, methane, methanol and other chemicals. Several commercial gasification processes are in use in the world, particularly in Eu-rope, South Africa [4] and Japan [5]. In the United States, major gasification projects Chapter 1. Introduction 3 are under way. Recently, the integrated gasification combined cycle process has emerged as one of the most promising new technologies for coal-based electrical power generation. Key process types for gasification are fixed bed, fluidized bed, spouted bed, entrained bed and molten bath. Each of them has its own special features, which have been reviewed by Hebden and Stroud [4]. 1.2 Basic Aspects about Coal Gasification Process Coal gasification is a process by which the conversion of solid coal into gaseous con-stituents can be brought about. In theory, two basic steps are involved: the breaking and releasing of the heavy hydrocarbon molecules into lighter molecules, and enrichment of hydrogen to increase the H/C ratio, as coal has relatively low hydrogen content in comparison with other conventional gaseous fuels. The first step corresponds to pyrolysis (thermal decomposition or devolatilization), which occurs upon heating to temperatures above 400°C in an inert-gas atmosphere. Through pyrolysis, coal undergoes a series of complex physical and chemical changes, and as a result, gaseous and liquid volatile matter and char are produced. Coal ^1 Solid(char) + Liquid{tar) + Gases(CO, H2, CH4, C02-- ) The char so formed consists mostly of carbon and ash, along with small amounts of hydrogen, oxygen, nitrogen and sulfur. The amount and composition of these pyrolysis products, though primarily dependent on the type of coal, are greatly affected by the tem-perature, heating rate, pressure, residence time, particle size and gaseous environment. These factors are also found to influence the physical structure of chars. The latter step is achieved with or without a catalyst by subjecting the coal char to a reaction with a gasifying agent—hydrogen, steam, oxygen or carbon dioxide, or a mixture of these, where steam and hydrogen are hydrogen donors. This is so-called coal Chapter 1. Introduction 4 char gasification, which yields a gaseous product stream that is suitable for use either as a source of energy or as a raw material for synthesis of chemicals, and leaves an ash residue. Char + Gasifying agent Gases(H2, CO, CH4, CO 2 • • •) + Solid residue (ash) Depending on the desired gaseous product, a certain gasifying agent or mixture is used. This study deals with the subject of non-catalytic steam gasification. For this type of gasification system, the principal reactions which are considered to take place are listed below. AH = +136 kJ/mol (1) AH = -34.6 kJ/mol (2) AH = +171 kJ/mol (3) AH = -89.9 kJ/mol (4) Note, all AH values are for a temperature of 1000 K and atmospheric pressure [2]. Reaction (1), the heterogeneous steam-carbon reaction, is significant at temperatures above 870°C. The products of this reaction, in turn, can participate in further reactions to some extent depending on the operating conditions. Reaction (2) (3) (4) are such reactions. C O 2 production is usually small because the equilibrium constant for Reaction (2) is two orders of magnitude below that for Reaction (1). Equilibrium for the formation of methane is not favored at atmospheric pressure, so the amount of C O 2 and C H 4 will be minimal. The above heats of reaction suggest that the overall steam-carbon gasification is endothermic, therefore some means is required for adding heat to the system to maintain the reaction temperature. This is usually done by addition of air or oxygen. C + H2O —> C O + H2 CO + H20 - C02 + H2 C + C02~^ 2C0 C + 2H2 — • CHi Chapter 1. Introduction 5 1.3 Background of Kinetic Study With emphasis on greater and effecient utilization of coal, since 1973 there has arisen a pressing need for improvement of existing and development of new processes for coal gasification. The design of any coal conversion processes depends in part on coal reac-tivity. As char gasification is much slower compared to the initial pyrolysis of coal, it usually controls the overall residence time required in the conversion process. Knowledge about chemical kinetics of this step is therefore essential for optimal design and control of this process. The nature of char gasification poses special features for its kinetics. • Coal is a heterogeneous material consisting of maceral and mineral constituents. The exact content and elemental composition varies from coal to coal. It is also well known that the rate of reaction or reactivity of coal strongly depends not only on the nature of coal but also on how the chars are prepared. This implies that one can not completely characterize coal by physical measurements or properties. Furthermore, although the kinetic description for gasification process can apply to more than one coal, the kinetic parameters such as the rate constant will have to be determined for every coal individually, until a sufficient knowledge has been developed to put the reaction kinetics on a sound fundamental basis. • In the course of char gasification, pore growth, pore coalescence and thermal an-nealing may occur. This means that the surface area, which is exposed to reactive gas; the porosity, which governs the local gas concentration; and the active sites, which determine the intrinsic reactivity, are all changing continuously as the reac-tion proceeds. These paramters are believed to be the major controlling factors for reactivities of chars [6]. Thus the kinetics of char gasification will be influenced by these variations. As well, a criterion is required, with which a measure of reactivity for chars can be determined and compared. Chapter 1. Introduction 6 Coal researchers over much of the world have contributed to the understanding of coal gasification processes, and publications on this subject are numerous. Several reviews [6, 7, 8, 9, 10] have appeared, in which a consensus has been reached on the controlling factors for gasification under a given set of conditions. These are: intrinsic reactivity of char, catalytic effect of mineral impurities and pore structure of char. Nevertheless, the kinetics regarding the char gasification is still not fully understood, as the role of these factors can not be predicted a priori and many problems remain to be solved. The performance of Canadian coals in gasification processes has becomes important both for domestic power production and coal exports. Aimed at providing measures of reactivity for Canadian coals, a considerable amount of research work has been done by coal researchers in Canada and in Japan, since Japan is the largest market for Western Canadian coals. So far this task has only been fulfilled in part by studies in spouted and fluidized bed pilot gasifiers [11, 12], and in smaller scale gasifier such as a 100 g laboratory fixed bed [13, 14, 15], and a thermobalance reactor [16, 17, 18]. While these studies are very useful to outline trends of coal gasification reactivity with chemical composition, for instance, the role of carbon content and of CaO & MgO contents which are found to have catalytic effects on coal gasification, other studies [19, 20] elucidate the effect on reactivity by some physical properties i.e. surface area and pore structure. A correlation between the reactivity of char and the carbon content of the parent coal for air gasification was presented by Fung and Kim [17]. Another correlation between the reactivity and carbon content and some operating variables was proposed by Kwon et al. [16]. Most of these studies suffer from short reaction times leading to incomplete carbon conversion, reactivity measurements made with oxygen where large temperature fluctuations occur, and use of milligram quantities of coal whose compositions may not be representative. The rate constants have usually been calculated over the initial linear portion of the carbon-conversion curve only [17, 14, 13], or in other cases [15, 16], using Chapter 1. Introduction 7 Table 1.1: The Coals Studied in This Work Byron Creek Quinsam Hat Creek Obed Mountain Highvale Gregg River Costello B.C. bituminous B.C. bituminous B.C. sub-bituminous Alberta foothills sub-bituminous Alberta plains sub-bituminous Alberta mountains bituminous Saskatchewan lignite the shrinking core model which is not sufficiently flexible to fit most gasification kinetics. Sakata et al [18, 21] have assessed the reactivities of a number of Canadian coals by thermogravimetric analysis (TGA), and developed a general correlation to estimate the gasification reactivity of char from conveniently measured properties of the parent coal i.e., fixed carbon content and moisture holding capacity. The reactivity is represented in terms of average rate constant assuming the conversion-time curve to follow that of the modified volumetric model (MVM) proposed by Kasaoka et al. [22]. The MVM has the virtue of being able to fit S-shaped carbon conversion-time curves, thus accounting for a rate maximum at an intermediate conversion. 1.4 Approach and Objectives In an attempt to provide further kinetic information on the gasification of Canadian Coal, and mitigate the deficiencies of previous work to some extent, this research was carried out in a stirred-bed gasification unit using a quantity of coal which is 1000-2000 times larger than that typically used in TGA studies, and allowing a sufficiently long reaction time in order to achieve complete carbon conversion. The particle size is chosen in a range typical of fluid bed gasifiers i.e. 1 mm.The gasifying agent is steam. Table 1.1 lists seven types of Western Canadian coals eventually covered in this work. Chapter 1. Introduction 8 These coals include only one (Byron Creek) that was tested in the work of Fung et al. [14, 13]. During the course of this work a study of CO2 gasification kinetics of Obed Mountain and Highvale coal chars was published [23]. All these coals are also being evaluated in Japan by Sakata's research group at Okayama University as part of a Canada-Japan Joint Academic Research Program on Coal Conversion. The main objectives of this research are: 1. To provide a measure of the gasification reactivity under the given reaction condi-tion for the eight types of coals.1 2. To relate the char gasification reactivity to coal rank or composition, and gasifica-tion temperature. 3. To test existing models and correlations for char gasification. 4. To compare the obtained reactivities with those evaluated by the Okayama Uni-versity group in Japan. 5. To couple reactivity measurements with initial BET surface area and the moisture holding capacity of char. xThe Byron Creek coal sample was tested in the form of a high-ash plant reject, as well as a product coal. Chapter 2 Literature Review 2.1 Coal Characteristics 2.1.1 Classification It has long been recognized that coal, as a fossil fuel, is heterogeneous in appearance as well as in composition. Its formation has occurred over long time periods, from plant masses via biochemical and geochemical processes, under high pressure of overburden and at elevated temperature. Differences in plant materials and in their extent of decay influence the nature of coal. Efforts have been made to classify the almost limitless number of coals into a broad classification by these two parameters. The coal formation process of a continuous evolution and degradation of the parent plant material towards a pure carbon or graphite structure is called coalification. Coal rank classification is based upon the degree of this process, i.e., rank is a measure of maturity of the coal as a whole in the coalification process. Coal rank thus depends on knowledge of a coal's proximate and ultimate analysis. Proximate analysis parallels carbonization; ultimate analysis indicates elemental composition. Typically, as rank increases, %C and calorific value (CV) increase while volatile matter (VM), %H, %0 and moisture content decrease. The original North American standard for classification of coal by rank published in 1939 is ASTM D388 (American Society of Testing Materials). Since then, it has been revised several times. The measurement conditions and techniques are also standardized in ASTM. 9 Chapter 2. Literature Review 10 Ash obtained upon coal incineration is different in chemical composition and is lower in weight than the mineral matter originally present in the coal. Several empirical for-mulas [24] have been developed for calculation of the mineral content mainly from ash content. One of the best known is the Parr formula [25] as follow: % Mineral Matter = 1.08 • %Ash + 0.55 • %Sulfur (2.1) Although the Parr formula is based on pyritic sulfur, the total sulfur is often used instead. Another simplified formula is provided by the ASTM classification system, when the highest accuracy is not required. % Mineral Matter = 1.1 • %Ash + 0.1 • %Sulfur (2.2) Another classification based on petrographic analysis emphasizes the compositional description of coal as a rock material. It is based on variations in visual characteristics as derived from degradation of different parts of the parent material. The constituents of coal are classified microscpically by observing transmitted light through thin coal section [26] or measuring the reflectance on a polished surface [27]. Macerals or organic counterparts of minerals are considered the fundamental constituents of coal. Having origins in the different botanic components, they are grouped into vitrinite, exinite and inertinite. Maceral carbon content (%C wt) increases in the order: Exinite, vitrinite, inertinite [28]. These three macerals showed different behaviors during coal pyrolysis [26, 29], which indicated the strong influence that petrographic constituent's may exert on coal conversion processes. More meaningful correlations between petrographic composition and coal reactivity await further investigation. Chapter 2. Literature Review 11 Figure 2.1: Basic Chemical Structure in Coal: (a) polynuclear aromatic (b - basal carbon, e - edge carbon), (b) hydroaromatic, (c) arenes, (d) methylene bridge, (e) substituted aromatics, (f) heterocyclics. 2.1.2 Organic Chemical Structure The starting plant material which ultimately forms coal is heterogenous, and as a result of combining with the natural variation in geological processes, the heterogeneity of coal is amplified. Unlike a conventional polymer, coal is an extremely complex polymeric solid with no repeating monomeric units, and is composed of variously substituted condensed polynuclear systems. As shown in Figure 2.1, the fundamental structures in coal are polynuclear aromatic, hydroaromatic, heterocyclics etc.. The hydroxyl (-0H), carboxyl (-COOH), and car-bonyl (=C0) forms are the major oxygen containing functional groups; hydroaromatic and aliphatic structure (Fig2.1 (c, d)) account for most of the hydrogen content. Possible structure models that represent statistically averaged composition data have Chapter 2. Literature Review 12 Table 2.1: Summary of Proposed Models Functional Groups Bridges Aromatic Ring Size Hydroaromatics 0-H, COOH, > O, C=0, >N:,>N-H ether, methylene, - 0 -C , hydrogen bonds 1-5 Dihydroanthracene, 9, 10 dihydrophenanthrene been proposed in three types • The aliphatic/polyadmantane model [30]. • The aromatic/hydroaromatic model [31]. • The molecular sieve model [32]. The model of Wiser [31], as illustrated in Figure 2.2 is based on small aromatic rings linked together by a wide variety of bridges, for example, ether and methylene. Although the models show marked differences in structure, there is substantial agreement on the composition of coal in terms of functional groups, heteroatom content, bridge, and heteroaromatic, aromatic and hydroaromatic structures. This structural information has been summarised by Thomas [33] in Table 2.1. The general picture [33] is that the functional group in coal are mainly situated on small aromatic structures held together by various type of bridges or hydroaromatic structures. The aliphatic part of coal is usually considered to be side chains or involved in bridges. Char, which results from devolatilization, is characterized by highly carbon-rich, polynuclear aromatic structures. Its e carbon atoms are at least an order of magni-tude more reactive than b carbon atoms due to the availability of unsaturated chemical bonds and the higher frequency of inorganic impurities at crystallite edges [34]. Cartz and Hirsch's [35] X-ray scattering work implies that maturation of coal, or higher rank, is Chapter 2. Literature Review 13 Figure 2.2: Model Structure Proposed by Wiser (31) Chapter 2. Literature Review 14 associated with a loss in aliphatic and hydroaromatic forms or with lamellae orientation and thus reduced porosity. The relative proportion of the substituent and the polynuclear systems also varies with coal type. This kind of information on structure of coals has not been related to coal reaction significantly to date, however, increased attention is now being given to structural effects. 2.1.3 Pore Structure Coals and chars exhibit complex and unique pore structure. As has been shown by Anderson et al. [36], Gan et al. [37] and others, coals contain a polymodal pore size distribution. Chars, which originates from coals by pyrolysis in an inert atmosphere, retain a wide distribution of pore sizes, though to some extent a change in the mean pore size of this distribution has occurred depending on a number of variables. Simons and Finson [38] state that the pore system in chars resembles an ordinary tree system, in which small branches feed into increasingly larger pores until eventually all lead into main trunks. The pore structure of coals and chars is divided into three broad pore ranges in diameter by IUPAC definition [39] • Micropores < 20A • Mesopores 20-500 A • Macropores > 500A This classification suggests pores are cylindrical, however, electron microscopy indi-cates the existing of cylindrical and conical pores, as well as flat cavities [40]. Thus the concept of pore diameter only approximates the overall pore structure. In a coal or char sample, mesopores and macropores represent physical cracks rather than chemical structure, while micropores reflect weak crosslinking among condensed Chapter 2. Literature Review 15 aromatic/hydroaromatic cluster. The macropores act as transport pores affecting the rate of diffusion into mesopores and micropores. The mesopores branch off the macropores and lead to the micropores which constitute the major part of the internal surface area. It was also found in many studies [37, 40, 26] that macropores dominate in low rank coals while micropores are characteristics of high rank coals. Pyrolysis takes place during the heat-up which precedes most coal conversion pro-cesses. As been pointed out in the literature [7, 9, 41] the pore structure undergoes little change until devolatilization begins (T>350 400°C). Coals lose volatile matter from aromatic/hydromatic layers and pass through a softening or plastic stage more or less like a thermoplastic organic before solidifying into a coke or char. The behaviour of softening, which does not occur to a significant extent with low or very high rank coals, is thought to be largely dependent on the concentration and thermal stability of crosslinking groups Hence, the exact structure of a char produced from a given coal will be a balance be-tween the thermosetting due to liberation of volatiles which results in the generation of porosity, and the thermal breakage of crosslinks which causes loss of microporosity that existed in the original coals. This balance, in turn, depends on carbonization conditions and the nature of the coal. Numerous investigations in respect to coal pore structure change due to pyrolysis have been conducted [42, 43, 44]. The consensus in these results is that surface area increases most for high heating rates, low final temperatures and for thermosetting (non-caking) coal. Knowledge about the pore structure of a char is useful in char gasification studies, since the pores influence diffusion within the char particles, and hence the reaction rates. Chars from coals of different rank would be expected to exhibit differing degree of resis-tance to internal mass-transfer effects during gasification. The results of Gan el at. [37] show that lower-rank coals tend to have a greater percentage of pore volume in larger pores than do higher rank coals.. It can be expected that chars derived from lower rank Chapter 2. Literature Review 16 coals would have a larger feeder pore system and be less limited with respect to mass transport during their gasification. The pore structure of coal is generally characterized by surface area, pore size dis-tribution, and porosity of the particle. These factors can be studied via a variety of methods. In this work, only the surface areas of the chars were measured, and scanning electron microscopy was used for studying the appearance of the chars. Moisture-holding capacity was determined by gasification workers at the University of Okayama in Japan. The theories for these methods are given below. B E T Surface Area Measurement The theory of multimolecular adsorption postulated by Brunauer, Emmett and Teller in 1938 [45] is known as the BET adsorption isotherm theory. Essentially, it is developed and extended from the Langmuir's isotherm [46] which is the first fundamental theory of adsorption of gases on solids based on the assumption of uniform, monomolecular layer chemisorption. However, in many instances, the Langmuir isotherm can not give a satis-factory explanation of observed results, especially when the adsorption isotherm denotes the characteristic of physical adsorption. The BET equation is derived from the same kinetic picture of condensation and vaporization of gas molecules and the assumption that in physical adsorption the forces of condensation predominate, thus adsorption can be in multimolecular layers. As well, the heat of vaporization is assumed to be the same for all layers following the first and is equal to the heat of vaporization for the bulk liquid. The BET adsorption theory is expressed by the equation below: V = VmCP (2.3) (P - P0)[l + (C- 1)(P/P„)] Where: V - Total volume of the gas adsorbed. Chapter 2. Literature Review 17 Vm - Volumn of the gas needed to cover entire adsorbent surface with a complete monolayer. C - A constant related to the heat of adsorption and liquefaction of the gas. P - Pressure of an adsorbate gas. Po _ Saturation pressure of the adsorbate at the temperature of adsorption. An important application of BET adsorption theory is to determine the surface area of a solid, which can be done either by the multipoint method or the single point method. Rearranging the above equation, gives: 1 (C-I)P + +-7^r-rT (2-4) V(Po-P) VmC VmC Po This is the form by which the BET multipoint method can be applied. Both P/V(P0 — P) and P/Po are obtained from experimental data, and the former is plotted against the latter. A linear correlation is expected if the relative pressure P/Po ranges from 0.05-0.35. From the plot C — 1 slope = — (2.5) vmc intercept = r (2.6) vmc From the slope and the intercept, the values of C and Vm can be easily evaluated. Ultimately, the surface area of the solid is determined using the equation below. S = V-=gL (2.7) VO Where: A 0 - Avogadro's number, 6.023xlO23. a - Molecular cross-section area of adsorbate. Chapter 2. Literature Review 18 V 0 - Molar volume of the adsorbate, 22.4 l/mol, at T = 273.IbK and P = latm. If C >^ 1, and the relative pressure is in the region of 0.05-0.35, Equation 2.4 can be simplified to the following form. Vm = V(l-£-) (2.8) •M) Only one point is needed in order to calculate Vm. This is called the single point method. Having the value of Vm, the calculation of the surface area of a solid is the same as that with the multipoint method. When specific surface area is wanted, the surface area must be divided by the weight of the solid. The most widely used adsorbate for measuring surface area of coal or char by the BET method is N2 at a temperature of 77 K with an molecular cross-section area of 16.2A2 per molecule. Some investigators use C02 at a temperature of 195K [20, 47], which usually gives a higher value of the surface area for the same coal or char analysed by N2. The explanation for this phenomenon can be found in the literature [48, 49, 50, 20]. • The penetration of a gas through capillaries of diameter less than 5A is by activated diffusion (Da oc e~Q/RT). C02 at 195K has higher diffusion rate than N2 at 77K, and because polar C02 can interact with coals/chars surface, C02 is more accessible than N2 to tiny micropores. • Some pores at 77K may shrink to such an extent that they are no longer accessible to iV2 molecules. The assumptions employed in the derivation of the BET isotherm have been criticized with respect to (1) the equal heat of vaporization at the liquid state and at all layers Chapter 2. Literature Review 19 except the first, and (2) the failure to consider interactions between adsorbed molecules in the horizontal direction. Modifications of the theory have subsequently been made by Anderson et al. [51], and Keenan [52], nevertheless it is still an efficient and simple method to determine the surface area of a solid for many cases. Whether the BET surface area of coal chars represents the area participating in the gasification reaction is another matter. Moisture-holding Capacity The moisture-holding capacity Q, [21] has units of g H2O per g of dry solid. A coal/char sample is previously dried for 25 h at 110°C, and then is exposed to moist air equilibrated at 30°C for 60 or 90 h. The value of Q is measured by determing the weight increase. The moisture-holding capacity is considered to correspond to the specific micropore volume filled with moisture. It is useful index of pore structure in relation to coal gasification. Table 2.2 contains the Q, values supplied by Okayama University for the coals/chars used in this research. Comparing values for both chars and coals, it is noticeable that for low rank coals, the moisture holding capacity of their chars are lower than that of the parent coals, however for high rank coals it is just the opposite. In addition, Costello coal has the highest value of fi, Gregg River coal holds the lowest value. A similar trend was also found in the unreported results of the gasification group in Okayama University for chars prepared at 1000°C for 7 min. One would expect, among these coal chars, the highest reaction rate for Costello char and the lowest one for Gregg River char if Q is an important index for gasification process. Chapter 2. Literature Review 20 Table 2.2: Moisture-holding Capacity for the Coals/Char (g/g of db) fi CT HV HC OM QS BC(1) BC(2) GR Coal 0.170 0.137 0.130 0.103 0.072 0.024 0.028 0.016 Char 0.129 0.129 0.103 0.101 0.095 0.036 0.035 0.031 2.2 The Kinet ics of Char Gasification 2.2.1 General Remarks The kinetics of coal gasification has been extensively investigated. Attention is often focused on char gasification, since the reaction rate of this process is much slower than the rate of pyrolysis. Furthermore, reactor design criteria and sizing of commercial gasifiers are largely dependent on coal-char reactivity. Char gasification is essentially a heterogenous reaction. In general, this type of reac-tion occurs by way of a series of diffusional and chemical steps [53] as follows: 1. Transport of reactants from the bulk stream to the particle surface. 2. Transport of reactants within the pores. 3. Adsorption of reactant on an active site. 4. Surface chemical reaction between adsorbed molecules or atoms with each other or with carbon. 5. Desorption of products. 6. Transport of the products within the pores. 7. Transport of the products from the particle surface to the bulk stream. Chapter 2. Literature Review 21 Figure 2.3: The Three Ideal Zones Representing the Change of Reaction- Rate of a Porous Char with Temperature The relative importance of each step in regard to resistance contribution to total re-sistance determines a rate controlling step. Several investigators, such as Walker et al. [6] Gray et al. [54] and Smith [55] have postulated the idealized three temperature zones or regimes by which the rate controlling step can be distinguished. Figure 2.3, according to Walker et al., demonstrates these zones graphically and shows the theoretical depen-dence of effectiveness factor T/ and apparent activation energy Ea on the temperature. In the low-temperature Zone I, chemical reaction is the rate controlling step. Intermediate-temperature Zone II is characterized by control jointly due to chemical and pore diffusion. Chapter 2. Literature Review 22 Zone III, which occurs at high temperature, is the bulk mass-transfer control regime. The intermediate Zones a and b represent transitions between the ideal cases. A more detailed discussion for this zone division is also given by Walker et al. [6] and other literature [7, 54, 8]. A study of overall kinetics of char gasification must necessarily consider both diffu-sional and chemical kinetic effects. The former depends on gas concentration gradient, flow rate of gas near the external surface and in the pores; the latter depends on the external and pore surface interaction with the gas. 2.2.2 Surface Mechan i sm for Char-Steam Reaction Fundamental research on the intrinsic chemical reaction for the carbon-steam reaction is essential to develop a kinetic model. Considerable work directed toward a basic un-derstanding of the reaction kinetics has been reported in literature. Though there are many inconsistencies in work related to the mechanism of this reaction, it is generally agreed that carbon-gas reactions follow a Langmuir-type rate equation over limited tem-perature ranges. Certain reactants and products inhibit the reaction rate as conversion proceeds, and the order of the reaction may vary between zero and unity, depending on the temperature and reactant partial pressure. A basic assumption common to interpretation of intrinsic carbon-gas reactions is the existence of active carbon free sites distributed throughout the carbon structure. For char, these active sites can be attributed to: (1) carbon edges or dislocations; (2) inorganic impurities; and (3) oxygen and hydrogen functional groups. Such sites provide unpaired electrons in various types of carbons, which induce electron transfer causing reacting gas constituent-carbon bonding or chemisorption to form surface-complexes. This bonding must be stronger than the carbon bonds in the lattice so that carbon atoms will be hberated in the form of reaction products. Chapter 2. Literature Review 23 The reaction between steam and carbon is one of the most important reactions in industrial processes, but its actual mechanism is still not fully understood. The major difficulties arise from the fact the at least four simultaneous reactions may occur each of which may affect the course of the others: C + H20 — > CO + H2 (1) CO + H20 ^ C02 + H2 (2) C + C02 — > ICO (3) C + 2H2^ CHA (4) The principal mechanistic studies of the carbon-steam reaction have been reported by Walker et al. [6] There seems to be general accord that the primary products of steam reaction with carbon are CO and H2, whereas C02 is a secondary product arising through the water-gas shift reaction. A simple oxygen exchange mechanism, without consideration of the water-gas reac-tion, is favored by Walker et al. [6], and Ergun and Mentser [10]. It comprises two elementary steps: Reversible oxygen exchange between active sites and steam, Cf + H2O^C{0) + H2 (1) Decomposition of surface oxides: C(0) — • CO +nCf (2) Where, n denotes that an average of n active centers must be generated for each carbon atom gasified. A second mechanism suggested by Gadsby et al. [56] and Long and Sykes [57] is as follows: Cf + H2O^C{0) + H2 (1) C{0) ^ CO +nCf (2) Chapter 2. Literature Review 24 H2 + Cf^C{H2) (3) Note here, the oxygen exchange reaction is assumed to be irreversible. Although the rapidity of hydrogen adsorption can not be dismissed, the first mecha-nism is generally preferred [7]. According to these mechanisms, an expression for the intrinsic reaction rate may be For these two mechanisms, the rate equation differs in the functional relation of elementary constants which combine as the rate constants such as a, b, k. Thus, the equation denotes that H2 inhibits gasification of carbon by steam based on either mechanism. In the first mechanism, the inhibition is caused by the reaction of a portion of the chemisorbed oxygen with gaseous H2 to produce H20, and in the second mechanism, by chemisorption of hydrogen on active sites. The analysis of order of the carbon-steam reaction as deduced from Langmuir-Hinshlwood rate Equation 2.9 has been given by several investigators [6, 8, 10]. Orders ranging from one to unity are expected, depending upon temperature, pressure, type of coal char and other factors. It has been shown that the constants a and b in the rate expression de-crease exponentially with temperature following the Arrhenius equation Ae~E/RT, where the value of E normally has a negative sign. When the term a pu2 is low enough that a PH2 <C 1 in the Equation 2.9, the kinetic of reaction can be either first order or zero order with respect to the magnitude of the term bpH2o, accordingly as this term is much less than or much greater than unity. The reaction order will be the first order if this term bpH2o <C 1. Both inequalities can be satisfied at low temperatures and low steam partial pressures, at which small amounts of CO are formed. These inequalities still hold written R = kpH2o (2.9) 1 + apH2 + bpH2o Chapter 2. Literature Review 25 at high pressures and at high temperatures, it is a case at 1370°C or above [58], where a and b decrease to small or negligible values. On the other hand, zero-order kinetics is indicated if this term bvn2o ^ 1) this condition is fulfilled at low temperature and at high steam partial pressure. Under conditions where all terms in the denominator are significant, a fractional order with respect to steam may be expected. Equation 2.9 successfully correlates some existing experimental data for the char-steam reaction [6, 8]. In more detail, this mechanism has been studied by Long and Sykes [57]. They proposed that steam dissociation occurs at the carbon surface into hydroxyl radicals and hydrogen atoms, which are rapidly chemisorbed at adjacent active sites. This is followed by a surface reaction involving hydrogen interchange. Therefore a further breakdown of the steps in the second mechanism may be written as: 2Cf+H20—>C(H) + C(0H) (1) C(H) + C{OH) —• C(H2) + C{0) (2) C{H2) ^Cf + H2 (3) C{0) — > CO + Cf (4) If allowance is made for the water-gas shift reaction [59] one more elementary step will be add to the first mechanism, that is reversible oxygen exchange between surface oxides and CO. C(0) + CO ^ C02 + Cf (3) Therefore, the Langmuir-Hinshelwood rate equation derived for carbon-steam reac-tion takes a more complicated form to adequately represent the kinetic data. 2.2.3 Mass Transfer It is obvious that transport processes may influence the overall reaction rate to a certain extent depending on various experimental parameters. In the case of large and porous Chapter 2. Literature Review 26 particles and low gas flow rate near the external surface, both external surface and inter-nal diffusion become important, and difFusional resistance may even overwhelm intrinsic chemical reaction. Thus the diffusional effects on reaction rate can not be always ne-glected. The discussions below are relevant to difFusional phenomena described as steps 1, 2, 6, 7 in section 2.2.1. External Mass Transfer A universal approach to model external mass transfer is to use a simple integrated form of Fick's law, i.e. J = km{Cb-C.) (2.10) Where: J - mol flux from bulk phase to particle surface (mol/s • m2). km - external mass transfer coefficient (m/s). Cb - concentration of reactant gas in the bulk phase (mol/m3). Ca - concentration of reactant gas at external surface (mol/m3). The mass transfer coefficient km can be obtained from a Sherwood Number correla-tion. For an isolated sphere with fluid flowing past it, S h = ^pV = 2 + 0Q^Reyj2Sci/3 ( 2 n ) "1,2 Where: dp - particle diameter (m). y - fraction of non-diffusion species. D 1 | 2 - binary diffusion coefficient of reactant gas and inert gas(m2/s). Chapter 2. Literature Review 27 (Re)P - Reynolds Number based on particle diameter = dpupg/p, where, u is the velocity of the gas, p is gas viscosity and pg the density of reactant gas. Sc - Schmidt Number = p,/pgDii2-It can be concluded that mass transfer coefficient is a function of properties of gas phase, gas flow rate and the particle diameter. Pore Diffusion For diffusion inside a pore Fick's law can be expressed as: J = -D§ (2.12) Where: D - diffusivity (m2/s). C - local gas concentration in the pore (mo!/m3). Z - distance along the pore (ra). Different diffusion modes are applied based on pore diameter. Molecular diffusion refers to the gas-gas collision mode, while Knudsen diffusion is known as gas-wall collisions, when pore size is small compared to mean free path of the gas. Diffusivities for both modes may be calculated using the following formulas: Dm = Uw (2.13) where: Dm - diffusivity of molecular diffusion (m2/s) I - mean free path = BoT/AA4d2m P (m). Chapter 2. Literature Review 28 w - mean molecular speed = (8BOT/TT M ) 0 5 (m/s). Bo - Boltzmann constant T - temperature P - pressure dm - molecular diamter M - molecular weight Dk = ^dw (2.14) Where: Dk - diffusivity of Knudsen diffusion (m2/s) d - pore diameter In the transition region between molecular and Knusen diffusion, the effective diffu-sivity De is obtained by the semi-empirical relation: When the pore size is in the order of magnitude of the molecules themselves, the so-called "configurational" diffusion takes place, which is a thermally activated diffusion process: Da = D°aexp(-Q/RT) (2.16) Where: Da - diffusivity of activated diffusion (m2/s) D°a - a constant Q - activation energy of diffusion Chapter 2. Literature Review 29 From these formulas, it is seen that Dm varies as T 1 ' 5 and P~l, D*. is function of T05 and linear with dp, Da is a strong function of T, but its value is small and is usually neglected. Hence, the mass transport coefficient, as metioned above, has a temperature dependence only to the power of < 1. On the contrary, the chemical reaction rate or more precisely the rate constant of the surface reaction increases exponentially with temperature according to the Arrhenius equation: k3 = ktexp(-E/RT) (2.17) Therefore, diffusion limitations of the overall rate happen mainly at high temperature. 2.3 Modeling for Solid-Gas Reaction 2.3.1 Basic Modeling Concepts The overall chemical kinetics of heterogeneous char reaction is usually measured via the char reactivity of the form [60, 61]: l_dW _ 1 dXf m ~ "Wo^T ~ ~(l-Xf) ~dT ( 8 ) or Rn = kbC£ (2.19) o - l Wo W n - W andXf = — (2.20) where: WQ - the initial sample weight of char (daf) dWjdt - the rate of weight loss during gasification Rm - overall char reactivity (g/s • g). Ci - the bulk concentration of gas (g/m3). kb - overall rate constant (g/g • s • (g/m3)n). Chapter 2. Literature Review 30 n - apparent reaction order. W - the sample weight at a given time Xf - carbon conversion based on the mass of fixed carbon. Two fundamental processes considered in the previous section i.e. mass transfer including external and pore diffusion, and surface interaction, must be accounted for and properly coupled into the overall kinetics. The global intrinsic surface rate R for any heterogeneous char reaction is given by [7] R = Mcp([Ct],CuT) (g/m2-s) (2.21) Where: Mc - mass of carbon atom (g/atom). p - the intrinsic site conversion rate. [Ct] - active site concentration (sites/m2). Ci - the local gaseous compositions (g/m3). T - reaction temperature. For narrow ranges of gaseous concentration and temperature, the complex Langmuir-Hinshelwood expression may be approximated for p by neglecting product inhibition, p = k[Ct]C m (C - sites/m2 • s) (2.22) where: k - intrinsic rate constant on a site basis (1/s • (g/m3)m). C - local reactant gas concentration (g/m3). m - the true reaction order. Chapter 2. Literature Review 31 Thus, the global intrinsic rate becomes: R = ka (g/m2-s) (2.23) ks = Mck[Ct] (2.24) wnere: ka - the intrinsic rate constant on area basis (g/m2 • s • (g/m3)m). Considering mass transfer effects, the overall char reactivity Rm is expressed as follows for isothermal condition. Rm=vS-Rb (2-25) Where: rj - the effectiveness factor (< 1). S - total surface area (m2/g). Rb - R evaluated with C = Cb-The effectiveness factor is defined as the true carbon consumption rate over the maximum value of rate in the absence of mass transport limitation. This concept is a simple method of considering the continuous change in local gas concentration resulting from mass transfer resistance. Combining Equations 2.22, 2.23 & 2.24, we have: Rm=vSMc{Ct]kCbm (2.26) Comparing to Equation 2.19 h=vSMc[Ct}k (2.27) Chapter 2. Literature Review 32 Therefore, kf,, the apparent rate coefficient is given by, Ea kh = kaexp(-^) and ktj the true rate coefficient is given by, E k3 = ktexp( — ——) (on area basis) RT where: Ea,Et - the apparent and true activation energies. ka,kt - the apparent and true frequency factors. These reactivity expressions are meaningful in terms of interpretation of fundamental gasification kinetics for chars. Equation 2.24 indicates that the char reactivity is pro-portional not just to total surface area (TSA), but more precisely to active surface area (ASA) [62, 63] i.e. [Ct]5. The dependence on the degree of gas penetration (77) is also obvious. It implies, as pointed out [41], that the reactivity of a char sample is primarily determined by (1) concentration of active sites; (2) accessibility of reactive gases to the active sites; and (3) concentration and dispersion of inorganic species present which act as specific carbon gasification catalysts. Since these factors are not readily measurable, application of such rate forms as Equation 2.26, are often merely curve-fitting excercises, and thus can not apply directly to the process. They are valuable, however as conceptual models of the reaction. r 2.3.2 Model Review For practical purposes, numerous kinetic investigations have been conducted in order to develop models for coal char gasification process. So far, a substantial body of literature (2.28) (2.29) Chapter 2. Literature Review 33 has been obtained. In this section, a brief review will be given to a number of models, which will include main assumptions, special features and comparison with others. The most simplistic macroscopic approach to modeling gas-solid reaction is the clas-sical unreacted shrinking core model [64, 65]. This model depicts reaction as taking place along a symmetrical front that recedes towards the center of particle leaving behind an ash layer. Three possible processes may be involved: gas film mass transfer, pore dif-fusion, and chemical reaction on the surface, any of which can become rate controlling. Therefore, the particle reactivity is expressed on an external surface area basis, its overall rate coefficient reflects three basic resistances. Its application has been made to the reaction kinetics of coal char gasification. Ev-idence from a wide variety of situations indicate that this model approximates reality reasonably well. Fung and Kim reported [17, 14, 16] their experimantal results of a number of Canadian coal chars gasified with steam and with carbon dioxide were well represented by this model. Osafune and Marsh [66] interpreted the char-carbon dioxide gasification data in terms of this model, and found it was applicable especially at lower levels of conversion. According to the assumptions made to develop this model, it is most suitable for (1) fast chemical reaction, (2) nonporous particle heterogeneous reaction. In spite of these restrictions, it is still the best simple representation for the majority of gas-solid reactions [67, 68]. However, there are some cases of reactions unlike that described above, where gaseous reactant can diffuse throughout a particle uniformly, and the reaction between solid and gas may be viewed as occurring homogeneously throughout the particle, thus the solid is converted continuously and progressively. This is the picture visualized by homogeneous model [69]. Both above models are idealized models. Examination of the available evidence shows Chapter 2. Literature Review 34 that the reaction may occur along a diffusion front rather along a sharp interface between ash and fresh solid, thus giving behavior intermediate between the shrinking core and the homogeneous models. For this problem, a general model has been proposed by Wen [67], Ishida and Wen [68]. From the general model view point, the period of reaction is divided into two stages. At the beginning, a reactant gas concentration gradient from core to bulk gas exists due to mass transfer resistances. After a certain time, the solid reactant near the surface is completely exhausted to form an ash zone, or diffusion zone, and an inner zone, where the reaction still take places. The time at which two zones appears is the boundary for two stages division. This model, as its name implies, is a more versatile model. In a majority of char gasifications studies the conditions give rise to the intermediate reaction scheme mentioned above [7]. One of the alternatives of extension to the shrinking core model is the grain model [70, 71, 72, 73]. In this model, the solid body is considered to consist of a distributed sizes of grains, with the centers of adjacent grains being spaced apart by a certain distance. Each grain reacts with gas according to the shrinking core model. However, unlike the shrinking core model where no explicit allowance is made for the effect of structural parameters, the grain model incorporates these parameters, such as the porosity, the grain size, the grain size distribution, and allows the quantitative assessment of the role played by these factors in determining the overall reaction rate. This model has been found to be able to predict the reaction of porous nickel oxide pellets with hydrogen within a temperature range [71], and of sulphation of lime [74]. While the foregoing models achieve apparent success in some circumstances, one may find a serious common limitation of them, namely the neglect of structural changes as reaction proceeds. Such changes are likely to occur in a number of cases. Hence, these models can not predict a maximum rate at intermediate conversion. Park and Levenspiel [75] introduced a distinctly different kind of model to account for Chapter 2. Literature Review 35 sigmoidal shaped conversion-time behavior, which none of the earlier models could. It is called the crackling core model. According to this model, an initially nonporous pellet transforms progressively from outside in, by "crackling", to form a grainy pellet, which then reacts away following the shrinking core model. Crackling, which is the formation of grainy intermediate, may occur by either physical or chemical action. Although the general conversion-time expressions of this model are algebraic, the model is of limited use, because two parameters are ususally unknown, for which tedious trial and error fitting must be used with experimental data of conversion-time. Another approach made by Kasaoka et al. [22] is to modify the volumetric or hom-geneous model, so that the modified volumetric model (MVM) is able to represent conversion-time curve having either a sigmoidal or nonsigmoidal character. It only con-tains two constants which are easy to obtain by using a fitting method. Further details will be given in Chapter 5. Appropriate allowance in models for the effect of structural changes during reaction would be desirable for direct interpretation of a given set of experimental data. Petersen's pore model [76] was the first attempt to account for changes in pore ge-ometry. He has used the very strong assumptions of uniform cylindrical pores and no intersection of reaction surfaces as they grow, which is the dominant factor after the initial stages of gasification. As well, the reaction scheme studied is limited to reaction in which all the products are gaseous. The single pore model derived by Ramachandran and Smith [77] provides a simple means of accounting for structural changes that occur during reaction by focusing at-tention on one pore. Its assumptions are similar to those of the pore model, but the reaction scheme is close to char gasification. The main advantage of this model is that the only two parameters required can be evaluated without complex computation. This model, particularly, seems valuble for predicting maximum conversions less than 100%. Chapter 2. Literature Review 36 Because of the assumption of uniform original radius for the solid, and no intersection of new reaction surfaces during reaction, its application is difficult with coal char, for which the pore size distribution extends over a broad range and new surface intersection does happen. Hashimoto and Silveston [78, 79] adopted a population balance technique to account for pore size distribution and coalescence of pores as they grow due to reaction. This approach, based on consideriation of pore size growth, initiation of new pores, and coales-cence of adjacent pores, makes available a detailed model for describing the development of specific area, volume, porosity, and mean pore radius of a solid with extent of gasifica-tion. It is especially useful in predicting the degree of gasification required to maximize the surface area in a solid. The model provides good agreement with the burn off data of Kawahata and Walker [80]. However, it suffers the ultimate fate of all moment meth-ods: that is, the necessity for a closure approximation involving adjustable parameters which must be obtained empirically. On the other hand, it is restricted to the reaction scheme of entirely gaseous products with no residue, which is not a case for coal char-gasification. A quantitative description of pore size distribution function, pore branching and pore combination is not given, but the details of these phenomena are buried within the adjustable parameters. A pore structural model for coal char introduced by Simons and Finson [38], and Simons [81] has improved and expanded the Hashimoto and Silveston approach to include the consideration of pore branching and pore combination. The pore size distribution function is determined, and it is the "order one" function of parent coal, char preparation and the char gasification processes. The pores are assumed to be cylindrical tubes, each pore that reaches the exterior surface of the char particle is depicted as the trunk of a tree. Each tree trunk of radius rt is associated with an internal structure whose surface area is proportional to rf. Chapter 2. Literature Review 37 1.0 0 0 0.2 0.4 0.6 Conversion X 0.8 1.0 Figure 2.4: Rate-conversion Curves According to the Model of Simons and Co-worker The significance of the pore tree becomes evident in constructing a char gasification model which is shown by Simons [82], and Lewis and Simons [83]. The effects of Knudsen diffusion, molecular diffusion, and both adsorption and desorption kinetics are included. The gasification rate is obtained analytically, and is integrated over the pore distribution function for total gasification rate. Several empirical relations, however, are used to relate the important physical properties of chars to the fundamental pore statistics.lt has been anticipated that the most critical element of the model is knowledge of the fundamental rate constant. Some existing models are recovered in the extreme limits of kinetic and diffusion control, for instance, shrinking core and grain pellet model, which corresponds to n = 2/3 in Figure 2.4. This figure demonstrates the rate-conversion curves at different initial porosities eo, which are cited from literature [84]. As shown in this figure, the maximum values of rate appear below e0 < 0.33. The testing and verification with oxidation data has also been given by the same authors [83]. Chapter 2. Literature Review 38 1.6 Conversion Figure 2.5: Development of the reaction surface with conversion according to the random pore model, compared with grain model (n = 2/3) and Petersen model for e0 = 0.26, L0 = 3.14 x 106 cm/cm3, S0 = 2.425 cm2/cm3. Chapter 2. Literature Review 39 The random capillary model of Gavalas [85] considers the porous structure of char as a set of straight cylindrical capillaries which intersect each other and partially overlap. A single probability-density function, weakly related but not identical to the customary pore size distribution, is derived to characterize the porous solid, such as the number of pore intersections and the evolution of pore volume and surface area during reaction. The pore size distribution is, however, characterized only by two moments. Hence, a bimodal type distribution can not be accounted for satisfactorily. An application to char gasification by oxygen or other gases has been considered under two assumptions: no diffusion limitation; no dependence of the intrinsic surface reaction rate on conversion. An expression is obtained for the conversion-time curve. The data from Dutta and co-workers [86, 87] have been used to test its validity of this model. Results show that much of the data, especially for the oxygen reaction and the lower temperatures, support this model. Deviations were observed at the higher temperature and for carbon dioxide reaction, indicating diffusion limitations or changes in specific activity of the mineral catalysts as expected. A random pore model, developed by Bhatia and Perlmutter [88, 89], allows for ar-bitrary pore size distributions in the reaction solid. It accounts for the random overlap of parallel pores as they grow by correlating them to the nonoverlapped pore volume, extending a theory originated by Avrami [90]. The significant features of this model are that (1) no assumption is needed as to the actual shapes of pores; (2) only one pore structure parameter is required to predict the solid reactivity. It is also capable of show-ing a maximum in reaction rate as well as a monotonically decreasing char reactivity as a function of conversion. The former behavior is expected to occur at the conversion level less than 0.39, when the structure parameter is 2 < ip < oo. These phenomena are all graphed in Figure 2.5. One other important function of this model is its ability to predict the surface area at any given conversion as a function of initial pore structure Chapter 2. Literature Review 40 parameter. Moreover, transport effects can be included. In this case the predicted sur-face area maximum would shift to correspondingly lower conversion. Other models arise as special cases of this model as demonstrated in Figure 2.5. It is simple, very easy to apply, allowing for separate treatment of the distributions. For this model, reasonable fit to the data has been achieved by several authors [88, 90, 91]. The problem of bimodal pore size distribution has been considered by Zygourakis et al. [92]. The pore structure of char is visualized to consist of two types of entities: the large spherical cavities and the cylindrical micropores. However, the coalescence of pores was accounted for by introducing two adjustable parameters. Also, the effect of the nonsymmetric shape of the pores, as well as the effect of the ash content on the reaction rate, were neglected. It requires the solution of a differential equation for pore size distribution, which increases substantially the complexity of this approach. The model of Srinivas and Amundson [93] simplifies the probabilistic model of Zy-gourakis et al. [92] by assuming a unimodal distribution of cylindrical micropores and that the existing macropores do not change. Various simplifications render the dimen-tionless moment equations analytically solvable which decreases the number of necessary computations. More recently, a different approach has been used to model the porous structure of a solid during reaction in kinetic controlling regime by Ballal and Zygourakis [94]. The models can treat porous solids having micro- and macropores of different shapes and exhibiting widely ranging pore size distributions. The effect of ash content of chars is considered. Pores are visualized as the results of overlapping and intersecting of cylin-drical cavities of different cross-section shapes parallel and perpendicularly. The model parameters can be obtained from measurable physical properties of the unreacted solid except for an adjustable parameter that make this model difficult to apply. Chapter 2. Literature Review 41 2.3.3 Correlations for Char Gasification In addition to these models, there are many semi- or empirical correlations available corresponding to certain situations, in which some of parameters have little physical significance. The following rate law is'sometime used for char gasification [95, 84]: ^ = * ( 1 - X , ) n (2.30) For the case of n = 1, the rate law gives, dXL = k(l-Xf) (2.31) dt k ~ [ dt}° Highly porous char (e > 0.6), produced at normal pressure with fast heating, follows this relation. Juntgen [96] achieved a rather good fit of experimental data of coal and low temperature char gasification with steam at 1 MPa and 810°C by Equation 2.30. Adschiri et al. [97] found the surface area S of this kind of char decreases linearly with increasing conversion in char-carbon dioxide gasification at normal pressure. 4-=l-Xf (2-32) <->0 This explains Equation 2.29, since the gasification rate is linearly proportion to the surface area during gasification. An exponent ra = 2/3 corresponds to the shrinking core model or the grainy pellet model. These are all as the special cases shown in Figure 2.4 and 2.5. Johnson [60] studied coal char gasification in gases containing steam and hydrogen, by assuming three main reactions: H20 + C^CO + H2 (1) Chapter 2. Literature Review 42 2H2 + C ^ CH4 (2) H2 + H20 + 2C ^ CO + CHA (3) The coal char reaction rate is expressed by the relationship: ~ = hKT{l-Xhyl*exV(-aXl) (2.33) and KT = K1+K2 + K3 (2.34) h = / 0ezp(8467)(l/T p-1/T) (2.35) where: Xf, - base-carbon (nonvolatile carbon in raw coal) conversion. KT - total rate constant for the three reactions, depending on temperature, pressure and gas composition. /o - reactivity factor for coal char gasification, depending on the inherent nature of the coal char. JL - relative reactivity factor, depending on the particular coal char and on the pretreatment temperature used for pyrolysis. a - kinetic parameter defined as a function of pressure and gas composition. T - gasification temperature (°R)-Tp - pretreatment temperature (°R)-when Tp < T, then /z, = /o-Johnson pointed out, for tests conducted in pure hydrogen, the value of a is 0.97, thus the term (1 — Xf,)2/3exp(0.97Xb2) is approximately equal to (1 — X^) over nearly a complete range of Xb. For this case: ^ = fLKT(l - Xb) (2.36) Chapter 2. Literature Review 43 This is in the same form as Equation 2.29. Adschiri and Furusawa [98] found the gasification rate per unit surface area remains mostly constant over the higher conversion range (Xf > 0.4) for the chars prepared at various heating rates under atmospheric pressure over the range of temperature pertinent to the fluidized bed gasifier (850-1200°C). Therefore, they formulated the following rate expression from their experimental data, = k0 exP(-E/RT) P i (2.37) This correlation denotes the close relationship of BET surface area and gasification re-activities of chars. For steam gasification [99], dX*Jdt = 0.0103 exp(-200, 000/RT) pH2o (2.38) For carbon dioxide gasification, dX*ldt = 1.7 x 10~5 exp(-140, 000/RT) pCo2 (2.39) When e > 0.6, substitute Equation 2.30 into Equation 2.36, and use the relation of initial surface area and the carbon content of parent coal, So = 2590 — 27.7C, the following equation is obtained: dXf/dt = fco(2590 - 27.7C)(1 - Xf) exp(-E/RT) P i (2.40) Thus the gasification rate, for this type of char over the given temperature and pres-sure range, can be estimated using only the gasification conditions (temperature, partial pressure of carbon dioxide or steam) and the carbon content in coal. Chapter 2. Literature Review 44 Kasaoka et al. [21] reported that fairly good correlation held between mean rate constant k reactivity and the moisture holding capacity fi and fixed carbon FC, where k is used as a criterion to evaluate and compare quantitatively various effects on gasification reactivity. *<*,) = ^ ( , « ) &(0.5) = k = ax (FCf2 fia3 (2.42) The term FC accounts for the variation in intrinsic reactivities among the parent coals; 17 is a useful index of micropore volume for char. It has been tested to be valid at many gasification circumstances [21, 100, 18]. Fung and Kim [17] define the char reactivity as: whereWo is the weight of the dry-ash-free initial char and dW/dt is the average rate of weight loss up to 10 % wt conversion. They proposed a correlation between the reactivity of char and carbon content (C wt% daf) of parent coal for air gasification: Rm = 13831 eajp(-0.12 C) (2.44) It has been found that the correlation coefficient is 0.81 in the carbon content range of 63.3 < C < 93.5%, and in the reactivity range of 0.2-4.0 mg/h • mg by using their own data and those of Walker et al. [101]. The same investigators [16] derived another correlation with C (wt% daf) of parent coal, particle size dv (cm), partial pressure of C02 pCo2 a n d reaction temperature T for char-carbon dioxide gasification based on their combined studies [102, 103, 104]. Rm = 85900 d;0'3 C 1 4 - 4 P c Q 2 exp(-18430/T) (2.45) Chapter 2. Literature Review 45 A correlation coefficient of 0.853 was reported for the ranges 2.2xl0~3 < dp < 2.2 cm, 0.7 < C < 1.0, 0.2 < pC02 < 1.0 atm and 974 < T < 1373 K. The expponent on the carbon content is difficult to justify by any theory. This section has presented various existing models and correlations of reaction kinetics from the literature. The discussion shows that not many of them appear suitable to apply in this study. A few are selected to be tested, for which, the details of the theory, the derivation and the application to the present study will be given in Chapter 5. Chapter 3 Experimental Apparatus and Procedure 3.1 The Apparatus for Gasification All the experiments for this study were carried out in a gasification system which was installed in the coal laboratory of this department. The apparatus was constructed previously by Nguyen [74] for the study of oil sand cokes gasification, and after minor modifications, was used for this research. As illustrated schematically in Figure 3.1, the equipment includes a reactant generat-ing and transport facility, a gasifier, a product gas handling facility and a control panel. The detailed description for each of them can be found in Nguyen's Ph.D thesis [74]. This section gives a brief outline of this system with an emphasis on the modified parts. 3.1.1 The Reactant Generating and Transport Facility This unit consists of a nitrogen cylinder, water container, a pump, a preheater which serves as a boiler, and two flowmeters with needle valves for water and nitrogen respec-tively. The water container is a plexiglass cylinder having a diamenter of 30 cm and a volume of 12 liters. A Masterflex pump was used to take distilled water from the container, pump it through a Porter rotameter, and then into the preheater. The flowrate of water was controlled by the needle valve. A Union Carbide nitrogen cylinder (K size) was utilized to supply nitrogen for system. 46 Chapter 3. Experimental Apparatus and Procedure 47 Chapter 3. Experimental Apparatus and Procedure 48 Nitrogen pressure was controlled by a two-stage regulator, and flowrate by the needle valve upstream of the Brooks rotameter. Both rotameters mentioned above were calibrated before this research started, and recalibrated after some runs had been done. The water flowmeter was also cleaned in order to remove scale which might have built up inside the tube. Figures 3.2 and 3.3 give the calibration curves for the Porter rotameter and the Brooks rotameter respectively. The preheater was constructed of 96.5 cm long, schedule 40 pipe of 316 stainless steel having an inside diameter of 7.8 cm and a 0.3 cm wall thickness. It was electrically heated by two full vestibule, 2.54 cm thick, 70 cm long, semicylindrical Watlow ceramic fiber heaters of 4.8 kW/2 phase/240 volts; and insulated by a 2.54 cm thick ceramic fiber blanket. To retain the heat and to increase surface area for heat transfer, the preheater was completely packed with 1.27 cm ceramic Raschig rings. On the top of the packing a stainless steel distributor was placed. The pressure in the preheater was indicated by a Bourdon pressure gauge while the temperature near the exit of the preheater was measured by a thermocouple. 3.1.2 The Gasifier The gasifier is the principal component of the system. Its shell is identical with that of preheater, however unlike the preheater, only the lower section of it was packed with 1.27 cm Raschig ceramic rings to retain heat and to increase heat transfer area, while the internal volume of upper section was occupied by a reaction chamber. The reaction chamber was a 40.6 cm long, schedule 40 pipe of 316 stainless steel having an inside diameter of 6.3 cm. The bottom of it was a gas distributor of 5% open area made of Mundt perforated plate of 508 fim diameter openings, which enabled steam to pass through, yet were small enough to keep the solid within. This chamber was fitted inside the gasifier shell and hung on the top flange of unit which was just beneath the Chapter 3. Experimental Apparatus and Procedure 49 17.5 -r 15-2.5 | i i 'i i j i i i i | i i i i j i i i i j i i i i | i i • 0 5 10 15 20 25 30 35 Rotameter Setting Figure 3.2: Calibration Curve for Nitrogen Rotamenter Chapter 3. Experimental Apparatus and Procedure 50 0.5 | I I I I I I I I I j I I I I I I I I I | I I I I I I I I I | I I I I I I I I I | I I I I I I I I I | I I I I I I I I I | I I I M ! I I I 5 6 7 8 9 10 11 12 R o t a m e t e r S e t t i n g Figure 3.3: Calibration Curve for Water Rotamenter Chapter 3. Experimental Apparatus and Procedure 51 cooling section. The cooling section was 9.53 cm in length, fabricated from the same stainless steel pipe as for the gasifier, with a stirrer on the position of its central line. A gland-nut packed the asbestos wire packing inwards for keeping the product gas from leaking out to atmosphere and the stirrer shaft vertically aligned. Cooling water which entered this section from the lower inlet and left from the upper outlet, served to protect the stirrer and the gland-nut from thermal expansion. Figure 3.4 is a sketch of cooling section. A thick-walled, 316 stainless steel tube, 9.5 mm OD, 6.2 mm ID was employed as the stirrer shaft. Its head was made of tungsten carbide. The mechanical structure of the head is shown in Figure 3.5. The stirrer was driven by a GKH 1/20 HP high torque motor through a sprocket and chain system. The speed of the stirrer was adjustable using the motor control unit. Temperature of the reaction zone can be measured by means of an Omega slip-ring assembly model SR-2 equipped with a thermocouple 81.3 cm long, inserted in the hollow shaft. This thermocouple was wired to the gasifier PID temperature controller. The control action was taken by gasifier heater, which was the same as preheater heater. The connection between the gasifier and the product gas handling facility was made by specially designed five flanges, which, together with the gasifier, are illustrated in Figure 3.6. Thomson spiral wound high-temperature gaskets rated at 150 psi with asbestos filler were used between any two flanges across the gasifier. 3.1.3 The Product Gas Handling Facility A cyclone of 5.04 cm diamenter and capable of removing particles down to dp 50-30 pm was immediately downstream of the gasifier to catch the majority of particles from the product gas. These particles were collected in a receiver which was attached to the Chapter 3. Experimental Apparatus and Procedure 52 a.To. *f- IS.24 COOLING SECTION WATCKIAL at s.s MEASURES M« QU/WiTYORKREP:! Figure 3.4: Engineering Drawing of The CooUng Section of The Gasifier(74) Chapter 3. Experimental Apparatus and Procedure 53 Figure 3.5: Mechanical Structure of The Stirrer Head bottom of the cyclone. Immediately after this cyclone was a water jacketted condenser operated using city water to condense water vapour which was contained in the product gas. The accumulated liquid was vented from the condenser bottom. Three glass wool filters and a coil cooler in an ice bath were subsequently used for further temperature reduction and fine particle capture before the gas mixture was discharged by a fan. The filters were 30 cm long and 8.5 cm ID plexiglass tubes. A sample port was located just after a dryer and before the third filter. That dryer is a glass tube filled with Magnesium perchlorate , which worked as the final device to get moisture captured before the gas sample was taken for analysis. 3.1.4 The Control Panel The control panel is the same as the one used by Nguyen [74]. The major features of the control panel were the power supply switches, the gasifier and preheater temperature 3. Experimental Apparatus and Procedure Figure 3.6: Engineering Drawing of the Gasifier and Its Live Flange (74) Chapter 3. Experimental Apparatus and Procedure 55 controllers, the system temperature indicator with a selector switch, the stirrer controller, the pump switch and the manometer. The power supply switches for main power and each electrical device were on/off switches and by means of the corresponding lights give a visual indication of power supply. A Thermo Electric model 940 controller was equipped for the gasifier. It operated on the PI(Fixed) control mode-proportional automatic reset, having 1°C resolution for setpoint and ±2°C controller accuracy in indication. The preheater controller belonged to series 100 of Thermo Electric model 32106-00. It had a fixed proportional band spanning 3% of full scale, and both setpoint and indication accuracy spanning 1% of full scale. The temperatures across the apparatus were taken by 8 thermocouples which all connected to the rotary selector switch and to a Elph centigrade digital temperature indicator. All the thermocouples were Chromel-Alumel type K, sheathed in Inconel, 4.8 mm OD of various lengths. The on/off, the speed and the rotation direction of the stirrer were controlled by a Series S Motor Controller. In a similar manner, the on/off, the speed and the rotation direction of the motor which drove the water pump were controlled. by a Masterflex Controller. Six pressure taps were placed in different parts of the apparatus and linked directly to the manometers by copper tubing. The pressures were indicated by either a mercury or a water manometer, using a three-way ball valve mounted on the panel. 3.2 Experimental Techniques The kinetic experiments for char gasification in steam were conducted in the stirred-bed reactor. The chars were derived from eight diverse coals, and their structural properties Chapter 3. Experimental Apparatus and Procedure 56 were examined by BET surface area measurement and by scanning electron microscopy. Semi-batch experiments were carried out in which pre-weighed samples of char were gasified in a continuous stream of 30% steam, 70% nitrogen by volume. Pressures were essentially atmospheric, and temperature was in the range of 870-930°C. Product gas samples taken from the reactor at different times were analyzed for H2, CO, C02, CH4 and N2 content by gas chromatogragh and the carbon conversion calculated. The exper-imental techniques that were involved in this research are described in detail below. 3.2.1 The preparation of chars The chars were prepared from eight types of coals using both mechanical and chemical methods. The char from each coal was prepared in the same way so that the obtained chars were comparable without the influence from their preparation. To meet the particle size requirements of this research, the coals were first crushed in Baun jaw crusher, the opening of which was adjusted approximately to the size demanded prior to crushing, The crushed coal particles were then sieved on the Gibson sieving machine. Each sample, a full screen tray of particles, was vibrated for 20 min before the sample was taken between two screen apertures, which were 1.40 mm and 1.65 mm for one size fraction, 0.85 mm and 1.40 mm for another case. These samples were sealed in plastic bags for later use. Char is the solid residue from coal pyrolysis, which occurs upon heating of the coal. The pyrolysis for char preparation was done in the stirred-bed gasifier as described as above. A 200 g coal sample as received was loaded into the reaction chamber. The temperature of the preheater was preset for 750°C, and the reaction zone temperature of the gasifier for 930°C. Nitrogen flowed through system at a rate of 7.5 l/min, at room temperature, and the speed of the stirrer was fixed at 26 rpm. Under these conditions, the heaters for the preheater and the gasifier were turned on, as well as all the controllers. Chapter 3. Experimental Apparatus and Procedure 57 A gas sample was then taken from the sample port every 12 min and analyzed on the GC. At about 60 min, the reaction zone temperature reached the preset value. By a time of 120 min, there was little CO, C02, CHA, H2 detected on the GC. This meant that the evolution of volatile matters from the coals was almost finished, and the pyrolysis was assumed to be complete. The chars produced were to be used either for char characterization or for gasification. For the first case, at 120 min of pyrolysis, the heaters were shut off, the stirrer speed was lowered, and the flow rate of N2 was reduced to the minimum level to drive heat out of system. Once the reaction zone temperature reached room temperature, the whole system was switched off, and the char sample was taken from the reaction chamber, and the fines collected from the cyclone receiver. They were weighed and made ready for analysis by various means in order to determine the initial conditions of the chars for subsequent gasification. These results are given in the next chapter. One such run to characterize the char was needed for each type of coal. For the case of the gasification experiments, the char was left inside the reactor after the pyrolysis, and the reaction zone temperature of gasifier was reset for subsequent reaction. 3.2.2 Gasification In this research, all the gasification experiments were operated following the pyrolysis process. At the end of pyrolysis, the set point for the reaction zone temperature was changed to the desired value. Once this value was reached, the water pump was turned on, a flow of distilled water injected into the preheater, where the water vaporized on the large surface of packing to superheated steam, which, mixing with heated N2, entered the conical section at the bottom of gasifier, and flowed upward into the reaction chamber through the lower section of packing and the distributor. Inside the reaction chamber, the reactant gas steam contacted solid char at the desired gasification temperature, and Chapter 3. Experimental Apparatus and Procedure 58 a series of consecutive and parallel gasification reactions took place. In the present case, the gasification occurred at atmospheric pressure, and the steam partial pressure was kept at 0.3aim. In order to do so, the flowrates of water and N2 were monitored to 2.4 ml/min (9.8 setting) and 7.5 l/min (11.6 setting) respectively, with N2 pressure set at 15 psi via the regulator. For this calculation refer to Appendix A. The gaseous products left the reaction chamber, passed through the cyclone, the condenser, the filter and the coil pipe condenser before the sample of gaseous mixture was taken by means of a syringe. The time interval for sampling was varied depending on the reactivity of the char and the stage of gasification. The gas samples were analyzed on the GC. The next subsection of this chapter deals with this subject in detail. The concentrations of each gaseous component determined, together with the total gas flowrate at each interval, were used to calculate the moles of carbon converted, which, in turn, made it possible to compute the fractional carbon conversion. The sample calculation is arranged in Appendix B and the results are stored in Appendix F. Since the steam gasification is highly endothermic, the necessary heat was supplied by the gasifier heater. The stirrer was installed to create better mixing and more uniform temperature. The controller enabled the reaction temperature always to be held near the set point, as well the temperature at each designated point in this system were recorded. 3.2.3 Product Gas Analysis A knowledge of the concentrations for N2> H2, C02, CH4, CO species in the product gas is essential to evaluate carbon conversion at different stages of gasification. In order to obtain these data, the analysis was done on a Varian VISTA 64 Gas Chromatogra-phy system, which is a VISTA 6000 Gas Chromatograph controlled by a VISTA 401. Having its own keyboard and CRT display, the microprocessor VISTA 6000 does its chromatographic functions in accordance with the operating parameters inputted from Chapter 3. Experimental Apparatus and Procedure 59 Table 3.1: GC Operation Conditions Column Temperature TCD Filament temperature TCD Temperature TCD Sensitivity Range Column A Flowrate Column B Flowrate Carrier Gas Inlet Pressure 50°C 280°C7 220°C7 0.05 2 0ml I min (200 s etting) 20ml/min(l90setting) 80 psig the keyboard. The VISTA 401 is a data station providing data handling and automation capabilities. For this specific analysis, the GC was equipped with a Porapak N column(A) 3.65 m long, 3 mm in diameter; and a molecular sieve 5A column(B) 2.8 m long, 3 mm in diameter. With the columns in series, H2, N2, CO, CH4 were analysed; while with bypassing of column B, C02 was detected. The thermal conductivity detector (TCD) was used with U.H.P grade Argon as the carrier gas. The operating conditions are listed in Table 3.1. Calibration for this GC was done using six special gas mixtures, The results were stored in the peak table of the data station and further used to identify peaks and calculate the composition of given samples. The details are given in Appendix C, as well as the Method designed for VISTA 401. At the beginning of each run, calibration was checked by using one of the standard gas mixture containing 75.04% iV2, 10.00% H2, 6.99% C02,4.99% CO, 2.98% CHA. Modifications were performed to maintain the accuracy of the analysis if the tolerance window was exceeded. The results are expressed in mole fraction of dry gas, and are compiled in Appendix F. In the same Appendix the reproducibility of the experiment is also shown by comparing the results from two identical runs. Chapter 3. Experimental Apparatus and Procedure 60 3.2.4 B E T Surface Area Measurement The surface area of each char was determined by employing a Micromeritics Surface Analyser based on BET theory as introduced in Section 2.1.3. The results for chars derived from eight coals are listed in Table 4.2. The machine was calibrated by using 1.0 ml N2 with an error ±0.02m 2 before each measurment. A gas mixture of 30% N2 and 70% He was used under a pressure 775 mmHg. Nitrogen acted as the adsorbate while He was the carrier gas. Using the short-pass mode of the system, the digital readout displays the computed single point BET surface area in units of m 2. Sample tube of the model P/N 230-61004-00 were filled with the known weight of chars. Before the surface areas were measured, the tubes were placed at the desorption station to drive any possible water out of the pores, as potentially the water could occupy a certain amount of pore surface area and in turn lower the measured total surface area for the chars. The measurement readily started after the samples were dried and conditioned by N2 gas at the temperature of 250°C for 2 hours. A sample tube was removed from the desorption station and placed at the test station. The adsorption began when the tube was immersed in liquid nitrogen. The reading kept increasing until equilibrium was reached, this final reading was the surface area of this sample measured by N2 adsorption. Another value of surface area for the same char was also obtained subsequently by removing the liquid N2 through the N2 desorption process. The average of these two values was used to calculate the specific surface area based on the mass of dry solid which was determined immediately after desorption finished. This test was repeated once for every char, and the average values are reported in Table 4.2. Chapter 3. Experimental Apparatus and Procedure 61 3.2.5 Scanning Electron Microscopy ( S E M ) A Hitachi S-570 SEM was used to examine the surface structure of the chars which were to be gasified in this research. Prior to examination, the samples were mounted on a base with a conductive graphite glue, and coated with a conductive carbon layer to prevent from corona due to the charge building up on the refractive surface of sample particles. The experiments were operated in vacuo below 10~4 mbar and at voltage of 20 kV. The eight kinds of chars were examined at various magnifications, and the photomicrographs were taken at magnifications of 50, 300, and 1000 times. These photomicrographs are displayed and discussed in Section 4.2.3. Chapter 4 Experimental Results and Discussion 4.1 Introduction The experimental results of this research are presented in this chapter. The consequent discussion is also given for the performance of each coal under different conditions. The interpretation of results in terms of kinetic models will be given in Chapter 5. The experiments were carried out to investigate the effect of coal type, gasification temperature and particle size on the reactivity of chars which were derived from eight types of parent coals ranking from bituminous to lignite which are characterized in the next section. BET surface area measurements and scanning electron microscopy were employed to determine the surface area and to observe the structure of each char respec-tively. In addition, the initial chemical composition of each char was also determined by elemental analysis. In this study, the fractional carbon conversion during the gasification stage is defined as following: X = NfC° + N c 0 % + " C E t x 100% (4.1) Where the carbon conversion X is expressed as the ratio of the moles of cumulative carbon converted into the various gases to the moles of carbon in initial chars excluding the moles of carbon found in the receiver at the end of gasification. The latter was calculated by burning the fine particles from the receiver. It is assumed that these particles only contain ash and carbon. Results are shown in Appendix F, where it is seem that the 62 Chapter 4. Experimental Results and Discussion 63 Table 4.1: Ultimate Analysis for the Coals Employed Coal Site Rank wt% daf wt% c H N S Odiff H20 CT Costello Sask. Lignite 72.81 4.76 1.30 0.67 20.46 30.24 HC Hat Creek B.C. Subbituminous 65.60 5.30 1.59 1.07 26.44 19.04 HV Highvale Alta. Subbituminous 73.12 4.85 0.99 0.20 20.84 15.99 OM Obed Mountain Alta. Subbituminous 76.82 5.51 1.74 0.49 15.44 10.97 QS Quinsam B.C. Bituminous 79.19 5.57 1.14 0.48 13.62 3.83 BC 1 Byron Creek (Plant Reject) B.C. Bituminous 78.52 5.31 1.31 0.31 14.55 2.44 BC 2 Byron Creek (Clean WCC) B.C. Bituminous 86.63 5.09 1.38 0.27 6.63 7.33 GR Gregg River Alta. Bituminous 89.81 5.02 1.29 0.31 3.56 1.78 Ow = m-(C + H + N + S) wt% - The values are given on the as received basis. wt% daf - The values are given on the dry ash free basis. correction is small A summary of operating conditions and results for all the gasification runs performed in this work are presented in Appendix F. 4.2 Characterization of The Coal Samples Eight different Western Canadian coals were studied in this work. Their proximate and ultimate analysis have been determined, and the results and corresponding rank classification in accordance with ASTM D388 are summarized in Tables 4.1. &; 4.2. It can be seen in Tables 4.1 &; 4.2 that the composition of these coals vary greatly. On the dry and ash free basis, carbon content covers a range of 65.60% to 89.81%. Oxygen contents (by difference) from 3.56% up to 26.44% were observed. Hydrogen contents were all around 5.00%. Sulfur level is commonly very low for Western Canadian coal. Sulphur content are between 0.20-0.67% except for Hat Creek coal which has a value of 1.07%. Chapter 4. Experimental Results and Discussion 64 Table 4.2: Proximate Analysis for the Coals Employed Coal Site Rank wt% db CV FR FC VM Ash Btu/Lb CT Costello Sask. Lignite 44.08 41.12 14.80 23886 1.07 HC Hat Creek B.C. Subbituminous 32.15 36.90 30.95 16866 0.87 HV Highvale Alta. Subbituminous 51.72 35.96 12.32 24458 1.44 OM Obed Mountain Alta. Subbituminous 48.66 34.13 17.21 25658 1.43 QS Quinsam B.C. Bituminous 51.10 37.33 11.57 28235 1.37 BC Byron Creek B.C. Bituminous 35.29 21.65 43.06 17301 1.63 1 (Plant Reject) BC Byron Creek B.C. Bituminous 62.14 24.55 13.31 30079 2.53 2 (Clean WCC) GR Gregg River Alta. Bituminous 66.24 22.80 10.96 32220 2.91 FC - Fixed Carbon VM -- Volatile Matter FR -Fuel Ratio (FC/VM) CV --Calorific Value measured on the dry basis. Chapter 4. Experimental Results and Discussion 65 Table 4.3: Mineral Matter Content of The Coals Coal BC(l) EC OM BC{2) QS GR CT HV wt% 45.46 27.39 16.75 13.44 12.25 11.77 11.37 11.26 Moisture (as received basis) ranged from 1.78% to 30.24%. On a dry basis, ash content as high as 43.06% was reached in Byron Creek (1) coal, which was a plant reject coal, but about 10-15% was more typical for normal production. BC (1) coal contained the lowest volatile matter, at 21.65%, while Costello contained the highest value of 41.12%. Fixed Carbon (FC) varied from 32.15% to 66.24%. Fuel Ratio, which is defined as fixed carbon/volatile matter, as an alternative for identifying coal type, was in the range of 0.87-2.91. The letters in the first column of this table will be used to identify the coal samples in this thesis. Table 4.3 is a list of the mineral matter content approximated with the Parr formula (Equation 2.1) for the coals employed in this research. Hat Creek coal contains the highest amount of mineral matter except for the Byron Creek (1) which is a plant reject. Analysis in regards to the chemical composition of these minerals was not performed for these coals in this study, nevertheless, the information in the databank of Western Canadian coal [105] and the analysis results of Sakata et al.[106] are quoted in Appendix E. No values for Gregg River were found. The composition of some oxides, which are considered to be catalysts for gasification, are fisted in Table 4.4. The last two columns of it represent the weight percent of CaO, MgO and all the catalytic oxides in these coals respectively. These values will be discussed further in Section 4.4.2. Chapter 4. Experimental Results and Discussion 66 Table 4.4: The Catalytic Metal Oxides Composition of Ash (wt% db) Coal BC(1) RC OM BC (2) QS* CT* HV CaO 7.07 3.22 6.82 4.25 31.10 14.97 10.88 MgO 1.09 1.93 1.30 0.88 0.21 3.42 0.96 Subsum 8.16 5.15 8.12 5.13 31.31 18.39 11.84 Na20 0.23 0.16 0.05 0.90 0.10 10.47 2.18 K20 0.75 0.68 0.63 0.50 0.13 0.85 0.60 Sum 9.14 5.99 8.80 6.53 31.54 29.71 14.62 Subsumx Ash@ 3.51 1.59 1.40 0.68 3.62 2.72 1.46 Sum x Ash@ 3.94 1.85 1.51 0.87 3.65 4.40 1.80 * - from [105]; o ;hers from Saka ,a [106] . @ - Ash content (wt% db) of coals as given in Table 4.2 4.3 Analysis of Chars The preparation of chars from their parent coals has been described in detail in Chapter 2. The chars obtained at the end of pyrolysis appeared to be completely devolatilized, since pyrolysis times were long enough so that no further evolution of CO, C02, CH4, or H2 could be detected on the gas chromatograph. Figure 4.1 shows the relation between mass loss from devolatilization and carbon content for each coal. Mass loss was calculated by first subtracting the weight of char collected in the reaction chamber from initial coal input calculated on a dry basis, and then expressed on a dry ash free basis. It can be seen that the mass loss % decreases as the carbon content or the rank of parent coal increases, which has been observed for other Canadian coals by Fung [17]. The chars which were formed under the same pyrolysis conditions are readily distinguished from one another in terms of chemical composition, surface area, and structures because of the great influence of their parent coal. Chapter 4. Experimental Results and Discussion 100 0 j i i i i \ i i i i | i i i i [ i i i i [ i i i i 50 60 70 80 90 100 C C o n + e n t o f C o a l ( d a f . w t % ) Figure 4.1: Mass Loss% versus Carbon Content of Parent Coal 160 C C o n t e n t of C o a l ( d a f . w t % ) Figure 4.2: Surface Area versus Carbon Content of Parent Coal Chapter 4. Experimental Results and Discussion 68 Table 4.5: Composition of Chars (wt% As Received) Composition CT HC HV OM QS GR BC[1] BC[2] c 74.07 57.32 69.31 77.19 84.07 85.98 48.85 77.82 H 0.31 0.21 0.62 0.37 0.26 0.32 0.20 0.29 N 0.90 1.05 1.15 0.63 1.38 1.28 0.79 1.14 ASH 20.87 43.42 24.04 23.02 14.73 13.56 50.68 17.32 £ 96.15 102.00 95.12 101.21 100.44 101.14 100.52 96.57 {Nc)char (mole) 5.35 4.73 6.84 6.96 8.60 9.73 6.19 9.39 4.3.1 Chemical Composition of Char Eight Canadian coals were pyrolyzed under the conditions described previously, and the chars were ground for microanalysis using mortar and pestle. The results are shown in Table 4.5. These values are averages of duplicate analysis results for each char sample. The deviation of the sums from 100% presumably reflects the accuracy of the sampling and the analysis, as well as the possible presence of traces of oxygen and sulphur.By comparing the data with analyses of their parent coals, the increase in carbon content and decrease in hydrogen content during pyrolysis for all the chars are evident. These changes arise from elimination of oxygen species and hydrocarbons during pyrolysis. The number of carbon mole, listed in the last row, is used as the initial value for calculating carbon conversion during subsequent gasification. 4.3.2 B E T Surface Area The surface area of each char was measured according to the procedure given in Chapter 3 for the single point BET isotherm method. The results were then converted to per unit mass of dry char. Eight samples of coal char were measured for their surface areas. There was a wide Chapter 4. Experimental Results and Discussion 69 Table 4.6: Surface Area of Chars (m2/g) Char BC[2] GR BC 1 OM QS HC CT HV Result 0.51 0.80 2.74 5.82 6.79 54.33 92.37 151.75 range among these values. The maximum value (151.75 m2/g) is about 300 times the minimum (0.51 m2/g). Table 4.6 lists the average of duplicate measurements of the surface area of each coal char. The surface area changes from one rank to another rank, and is shown as a function of C content of the parent coal in Figure 4.2. Even though the data are widely scattered, in general the surface area declines sharply as the C content or rank increases until a Cdaf — 80 %, beyond which, the curve levels off. This behaviour of surface area of char was also reported by other investigators [19, 20]. 4.3.3 S E M Examination Scanning electron microscopy (SEM) was employed to examine the surface structure of each char. Three magnifications, x50, x300, and xlOOO, were used for taking photomi-crographs of typical areas on each sample. The combination of all results provided visual information about particle shape, surface structure, and details of the specific surface for the different chars. For each magnification, three photomicrographs are presented as typical ones for bituminous, subituminous and lignite coals. As shown in Figure 4.3 (1, 2 and 3), all the particles are irregular but similar in shape, having some cracks on the surface except for the chars from bituminous coal. The latter samples came from big lumps which were formed due to swelling and agglomerating during pyrolysis, and had to be crushed before gasification These pictures also illustrate the close average size of different samples and the narrow size distributions of particles for each sample. However, bituminous coal char particles showed fine average size and much wider size distribution. 1 2 Figure 4.3: SEM Photomicrographs for Three Kinds of Chars at Low Magnification (1-Costello, 2-Obed Mountain, 3-Gregg River). Chapter 4. Experimental Results and Discussion 72 Chapter 4. Experimental Results and Discussion 75 Chapter 4. Experimental Results and Discussion 76 Examination of medium and high magnification photos in Figures 4.4 &: 4.5, indicates that the chars of the bituminous coal have smooth surfaces, and possess numerous macro-pores. The chars which derived from subbituminous coal and lignite appear to be very rough on the surface, which is full of interstices, layers and cracks to different degrees for the different samples. Furthermore, the high magnification photos support the above evidence by demonstrating an even clearer view of the unconsolidated structure of these char particles. 4.4 Gasification Experiments on the Different Types of Coa l 4.4.1 Results This research covered eight coals from Western Canada, whose proximate and ultimate analysis results are listed in Section 4.2. According to these analyses and the corre-sponding chemical composition and surface analysis results obtained for their chars, it is apparent that they varied significantly from one to another with regard to their chemical and physical properties. Consequently, although gasified under the same conditions, the chars exhibited different behaviour in gasification depending on the nature of the parent coal. To study the effect of the type of coal on its reactivity, the coal particle size and the steam partial pressure were kept unchanged at 0.85-1.40 mm and 0.3 atm respectively for all experiments. The temperature was set at levels between 870°C and 930°C. In this section only the results at a temperature of 930°C are presented. Figure 4.6 is conversion-time plot for the eight types of coals gasified under the same conditions at 930°C. In this plot, each special line which connects symbols is drawn by applying Root-Mean-Square minimization to the experimental data using TE11AGRAF software. These curves are similar in shape, and generally include two different regions. IS X c o 'co > C o o c o _Q v. O o 110' 100-90-8.0-70-60-i 50-40-30-20-10-0 .0" -Di e ' JO • / j a ^ 3EE Legend • QM RUN 60 V QS RUN 44 • GR RUN 59 • HC RUN 58 M. CT RUN 55 U HV_RUN_6_5_ ta BC1RUN 47. 0 BC2RUN 49 i i i l i i i i l i 50 100 150 1 I11' ' i M 1 1 1 1 ! 1 200 250 300 Time t (min) 350 400 450 500 8 3 So ft c S3 o e tn tn o Figure 4.6: Carbon Conversion versus Time for Runs of the Eight Chars. Temperature =930°C. -4 Chapter 4. Experimental Results and Discussion 78 The first region of curves is sigmoidal with an inflection point between 10% and 25% carbon conversion; and the second one is asymptotic. Wide differences in conversion for the different chars are evident. At a time of 50 min, Costello coal reaches a carbon conversion 67%, while other, e.g. Gregg River, attain a much lower carbon conversion of 5%. However, this fact does not imply that Costello achieves the highest conversion for the whole period of gasification. As reaction proceeds, some curves overlap, which changes the relative reactivities for some coal chars. Of the coals tested Obed Mountain coal reaches the highest carbon conversion. These curves then become asymptotic, where reaction gradually terminates. For the least reactive coals, because the reaction times were not long enough for them to reach the second region of the conversion-time curve, these curves are almost linear over the gasification period. Figure 4.7 demonstrates changes of reaction rate with carbon conversion for each coal char. As was expected by the shape of conversion-time curve and existence of the inflection points, rates go through a maximum. UBC subroutine DSPLFT and DSPLN were chosen to generate the rate of carbon conversion by first fitting a cubic spline function to a set of conversion-time data and then taking the first derivative to get the rate data. It can be seen from this figure, that gasification started at a relatively low rate, and as carbon conversion increased, the rate at first increased. After a maximum was approached, the rate decreased below the initial value and ultimately to almost zero. Though all curves present this trend, big differences still exist. Costello char always has the highest reaction rate in steam gasification up to 85% carbon conversion. This rate maximum for Costello char is about ten times the lowest maximum rate which was for Gregg River char. The three subbituminous chars, Highvale, Obed Mountain and Hat Creek, have similar reaction rates. This figure also illustrates that the lower the maximum rate is, the flatter is the curve of rate versus conversion. The half-life, i.e. the time to reach 50% conversion, being a measure of the inverse Legend • OM RUN 60 V QS RUN 44 • GR RUNJ59 • HC RUN 58 CT RUN 55 HV RUN 65 BC1RUN 47 0 BC2RUN 49 •ia ia ta is 1*2 N \ 20 30 40 50 60 70 Conversion (%) 80 90 100 110 Figure 4.7: Change of Rate with Carbon Conversion for Eight Chars. Temperature=930°C. Chapter 4. Experimental Results and Discussion 80 400 \j —|—i—i—i i j i i—i—i—|——i—r—i—r—j—i—i—i—i—|—i—i—i—i— 0.5 1 1.5 2 2.5 3 Fuel Ratio (fixC/VM) Figure 4.8: The Relationship between Half-life and Fuel Ratio. of the initial rate, is plotted against the fuel ratio of the coal in Figure 4.8 The fuel ratio is defined as the ratio of fixed carbon to volatile matter, and has been used as a rough correlating parameter for reactivity. Very high fuel ratios correspond to high rank coal such as anthracite, whereas lignites with low fixed carbon content would have low fuel ratios. Therefore this figure is another indirect way to relate the reactivity of chars to their rank. Fuel ratios for the coals studied in this research range from 0.87-2.91. It is obvious that the half-life rapidly decreases with increase of fuel ratio. Within the fuel ratio range of this work, lower fuel ratio coal tends to have higher reactivity as is expected. Figure 4.9 reveals the relation between half-life and the carbon content of parent coal. It indicates higher carbon content of coal leads to lower reactivity of its char, or in other words, char from lower rank coal has higher reactivity. Chapter 4. Experimental Results and Discussion 81 c o TJ D CD M — O CD D 400 320-240 160-80-i I i i i i i 50 62 74 86 98 110 C C o n t e n t o f C o a l ( d a f . w t % ) Figure 4.9: The Relationship between Half-life and Carbon Content of Parent Coal. 4.4.2 Discussion These experimental results suggest that of the coals in this investigation Costello coal char is most reactive and Gregg River is least reactive as shown in Figures 4.6 & 4.7. The increase of the reactivity for these chars as judged by time to reach a given conversion is in the order of GR, BC(2), BC(1), QS, HC, 0 M , HV, C T , or in terms of rank, reactivity increases in the order of bituminous, subbituminous and lignite. This is generally true until about 85% carbon conversion was reached, above which, overlapping of curves can be observed, and the rate of gasification for HC and C T became negligible before 100% carbon conversion was obtained. This unexpected achievement of an asymptotic conversion of less than 100% might have been caused by experimental limitations, such as the carrying over of fines without being caught by cyclone, or less likely the release of carbon containing compounds that were not detected on G C . Figure 4.6 indicates that the gasification of O M char ended up with carbon conversion higher than 100%, which must have resulted from experimental errors, such as an overestimation of the fines from Chapter 4. Experimental Results and Discussion 82 50 62 74 86 98 110 C C o n t e n t o f C o a l ( d a f . w t % ) Figure 4.10: The Relationship between Oxygen Content of Coals and Carbon Content of Parent Coal. the cyclone due to the adsorption of moisture, tar or any volatile matters other than carbon. These errors, in consequence, affect carbon conversion calculation by increasing the moles of carbon found in the receiver. It is generally accepted that char reactivity increases as the rank of the parent coal decreases [17, 14, 7, 5]. Figures 4.8, 4.9 where the reactivity is expressed in terms of half-life, are indications of this relationship. It has been the consensus for a large number of investigators [7] that the gasification of coal char is controlled mainly by intrinsic reactivity of char, catalytic effect of mineral impurities and pore structure. Furthermore, the intrinsic reactivity is primarily determined by the concentration of carbon edges and defects, as well as oxygen and hydrogen content. Many studies have suggested that these factors prevail for lower rank coals [19]. The results of this investigation reinforce this conclusion. Figure 4.10, as an example, is a plot of oxygen content of the parent coals which were taken from the ultimate analysis results, as function of carbon content of parent coals. It clearly shows that the oxygen content declines as the carbon content Chapter 4. Experimental Results and Discussion 83 of the coal increases. This phenomenon has also been reported elsewhere [86, 87]. The relation between surface area of each coal char and carbon content (Figure 4.2) was discussed in Section 4.2.2. This is also a demonstration that the chars derived from lower rank coal have higher surface areas, and this dependence of surface area on coal rank becomes smaller above Cdaf > 80%. This general trend of surface area changing with Cdaf is similar to that reported by previous work on other coals [19, 29]. For the coals used in this study, their mineral matter contents, which were calculated using Parr formula, are listed in Table 4.3. Although there is no correlation being found between coal rank and mineral content in weight, it has been proven [17, 101, 107, 108, 109] that some components of mineral matter, such as metal oxides CaO, MgO, Na20, K20, may promote the reactivity more or less as catalysts, or as the physical diluent reducing the agglomeration tendency which leads to higher overall surface area [110]. The catalytic activity of CaO and MgO are of prime interest. The reactivity of various Canadian and US chars were found to correlate well with the amount of CaO and MgO [17]. In the absence of specific analyses of ash constituents in this work, the data from the Databank of Western Canadian Coals [105] and Sakata et al. [106] are adopted in Table 4.4. Figures 4.11 &; 4.12 show an attempt to relate the char reactivities to their CaO, MgO content and CaO, MgO, Na20, K20 content in the coals, excluding Byron Creek plant reject. It seems that the half-life of char can not be correlated solely with the amount of these oxides, since the data points scatter to a considerable degree, especially for Quinsam coal char. The scatter of the data may be an indication that the catalytic activity is not only controlled by the amount, but may also depend on dispersion of these oxides in coals and their state as well as other factors. The conclusion drawn by Miura et al. [5] based on their review is that such minerals in their active form are rarely involved naturally in high rank coals. It is well established that coal rank does influence reactivity in gasification, which has been confirmed by this research. Chapter 4. Experimental Results and Discussion 84 Figure 4.11: The Relationship between Half-life and CaO + MgO content. _^ 300 All Oxides in The Coals (wt% db) Figure 4.12: The Relationship between Half-life and CaO + MgO + Na20 + K20 content. Chapter 4. Experimental Results and Discussion 85 Half-life, as a measure of the reactivity for coal char, correlates well with the fuel ratio. Figure 4.8 illustrates that the gasification reactivity varied strongly and almost linearly with the fuel ratio. This accords with Kasaoka's et al. [22] result, which covered a rather wider range fuel ratio. The present case represents one side of their curve, where fuel ratio < 3. As suggested by Dutta et al. [86], therefore the fuel ratio is a convenient and useful factor for empirical correlation of the reactivity of coal char. As has been mentioned above, in accordance with its definition, low rank coals will have low fuel ratios while high rank coals high fuel ratios. This empirical parameter, while useful, provides little of fundamental significance however. It has been widely recognized [14, 111, 112, 113, 86] that inflection points exist in plots of conversion versus time of some coals. These points correspond to the rate maxima. The values of carbon conversion, at which the inflection points occur, have been successfully predicted by a few authors [22, 75, 76, 88] employing models as mentioned in section 2.3.2. For example, the random pore model predicts that the maximum value always appears at carbon conversion no higher than 39%. Some other ranges are also given by others depending on their model assumptions. In this work the inflection points lie between 10 - 25% carbon conversion as shown in Figure 4.7. Typical ranges, for occurance of a maximum in the reaction rate are 10-40% by Dutta &; Wen [86], 20-65% by Young et al. [112] and 10-50% by Adschiri et al. [111]. The variation was usually attributed to differences in gasification conditions, and in the types of coal studied. So far the essential nature of the inflection point in a conversion-time curve is not very clear. In a sense, it is the result of the fairly complicated overall effect exerted by the changes in the chemical structure, in the surface area, and in the physical structure during the process of gasification. It does not always correspond to the maximum in the surface area, for example. Chapter 4. Experimental Results and Discussion 86 4.5 Experiments at Different Temperatures 4.5.1 Results The influence of temperature on reaction rate was tested for the eight chars. For most chars two temperatures 870°C and 930°C were used. Whereas for two of the chars, experiments were also done at 900°C. Other reaction conditions, such as, 0.85-1.40 mm particle diameter, 0.3 atm steam partial pressure, were held constant for each run. In consequence, the differences of conversion which appear in the experimental results arise solely from the temperature variation. For demonstration, one char was chosen from each rank of coal char to use as a representative sample. Three sets of experimental results are displayed in Figures 4.13-4.18. These are plots of conversion against gasification time, and the corresponding rate vs. carbon conversion, which are generated using the same method as for Figures 4.6 &i 4.7. As was described in the previous section, the conversion-time curves encompass the sigmoidal and the asymptotic regions with an inflection point, which leads to the rate maxima for rate-conversion curves. From Figures 4.13, 4.15 & 4.17, it can be seen that, in general, as expected, steam gasification at higher temperatures attained higher conversion than at lower temperature for the same time. However, this did not always hold throughout the whole reaction. High temperatures resulted in more rapid attainment of the asymptote than for the experimets at low temperatures. Finally, when both curves approached the asymptotic region, the conversion value for high temperatures was for some reason lower than in the case of the low temperature runs. The rate maxima, as expected from conversion-time curves, occur in the rate-conversion curves of Figures 4.14, 4.16 & 4.18. The maximum values are higher at high temper-atures than at the low temperatures; and usually higher temperature runs have higher reaction rates compared to lower temperature runs. However, as conversion increases, Chapter 4. Experimental Results and Discussion 87 X c _o *w > c o CJ o _Q i _ D O 100 80H 60 H 40 20 H .-^•-v—v--v- -V •y V it If / 50 Legend • 930°C RUN 55 V 870° C RUN 51 100 150 200 T i m e t ( m i n ) i i i i i i i i i i 250 300 Figure 4.13: Effect of Gasification Temperature on C Conversion of Costello Coal. o >S 5 X ^.75-1.5 -. 1.25 ^  1-4 0.75^ 0.5-0.25^ 0-/ Legend • 930° C RUN 55 V 870° C RUN 51 X \ 20 I i i i i I i i i i I i i 40 60 80 100 Carbon Conversion X (%) Figure 4.14: Effect of Gasification Temperature on the Rate of C Conversion of Costello Coal. Chapter 4. Experimental Results and Discussion 88 X c o i _ > c o O c o X) i _ D O 110 100 90 80 70 H 60 50-40-30-20 10H / /V / v V v-Legend • 930° C RUN 60 V 870° C RUN 62 i I i i i i l i i i i l i i i i I i i 50 100 150 200 Time t (min) 250 300 Figure 4.15: Effect of Gasification Temperature on C Conversion of Obed Mountain Coal. 1.5-r c 1 1 2 0.9-1 " O 0.6 X • ' cu 0.3 V 1 X Legend • 930° C RUN 60 V 870° C RUN 62 i 1 20 40 60 80 100 Carbon Conversion X(%) Figure 4.16: Effect of Gasification Temperature on the Rate of C Conversion of Obed Mountain Coal. Chapter 4. Experimental Results and Discussion 89 100 X 80 c q 60 H > c O AO-A o c o JQ o o 20-o»V>; o Legend • 930° C RUN 59 V 870° C RUN 57 i i l i i i i l i i i i l i i i i I i 100 200 300 400 T i m e t ( m i n ) 500 Figure 4.17: Effect of Gasification Temperature on C Conversion of Gregg River Coal. o X "a DC 0.4 0.3 0.2-0.1, Legend • 930° C RUN 59 V 870° C RUN 57 o.o- ^ r 20 40 60 80 C a r b o n C o n v e r s i o n X (%) 100 Figure 4.18: Effect of Gasification Temperature on the Rate of C Conversion of Gregg River Coal. Chapter 4. Experimental Results and Discussion 90 the difference gets smaller and smaller. Eventually, the rates from lower temperature runs exceed the values of high temperature runs. 4.5.2 Discussion It is evident that temperature does affect reactivities of all types of chars studied in this work, i.e., those derived from lignite, subbituminous and bituminous coals. The extent of this effect varied for the different coal chars and from time to time during the gasification period. According to the results from this research, the conclusion can be drawn that the influence of gasification temperature becomes stronger as coal rank decreases. On the other hand, for all types of coals, with the increase of reaction time or conversion, the sensitivity to the temperature over the range used first increases, then decreases in the region of the asymptote, and even higher ultimate conversions were reached at lower reaction temperature with the highly reactive coals. The reason for this finding is not clear. Some possible explanations are given below. The phenomenon may be attributed to the change of reaction control regime. Usually at low conversions, the rate of gasification is controlled by chemical reaction, thus the gasification temperature is an important factor. However at high conversions, the diffusion resistance to steam passing through the layer of ash and the film of gas to reach the unreacted carbon may increase, consequently the effect of reaction temperature becomes less important than before, which was also deduced by Furimsky [15] from his study of lignite gasification over a wide temperature range. Furthermore, provided the structure generated at higher temperature is more resistant to diffusion, a lower final conversion could result. Another reason might be that free active sites disappear spontaneously by thermal healing or annealing of the surface. The experimental study made by Duval [114] has given strong evidence for the occurrance of this thermal process at high temperature. The effect of thermal annealing increases with temperature and depends on the lifetime of active sites. Chapter 4. Experimental Results and Discussion 91 This hypothesis could explain why a low rate is obtained in the final stage for the high temperature runs. The temperature effect will be discussed further in Section 5.3.2. 4.6 Experiments with Different Particle Sizes 4.6.1 Results The particle size effect on reactivity was tested only for two types of coal chars at a steam partial pressure 0.3 atm and at temperatures of 870°C & 930°C respectively. Two different particle diameters used for this purpose were 0.85-1.40 mm & 1.40-1.65 mm. The work in this thesis was not primarily aimed at studying particle size effects, therefore the samples were not of fairly wide size distribution, and the mean values not markedly different. The results for different particle sizes were put in a single figure for comparison. Figures 4.19 & 4.20 constructed as for Figure 4.6 are results from Obed Montain and Highvale chars. Both figures show that over the narrow range tested, there are no significant differences in carbon conversion for runs with different particle sizes where other reaction conditions are held constant. Nevertheless slightly higher conversions were obtained with the smaller particle size chars. Less than ±7% differences in conversion were found in the results of the two particle sizes. These differences may not be significant, given the experimental errors. 4.6.2 Discussion Figure 4.19 &: 4.20 clearly show that no significant differences was observed in carbon conversion for the two types of coal chars which were gasified using average particle diameter 1.13 mm L 1.53 mm at 930°C & 870°C. Kasaoka et al. [115] have also conducted some experiments by TGA with char particle size of 0.5 mm & 2.0 mm at temperatures less than 1, 000°C, and found virtually no difference in the rate of gasification. The results 110 T 100 90 80 70' 60-5 0 -40-; 30^ 20 -10 0 D - Or =  D O Legend • dr=1.13mm, 930° C RUN 60 V d=1,13mm, 870° C RUN 62 • d =1.53mm, 930° C RUN 43 —p — — -— _ _ _ _ _ _ _ _w d„-1.53mm, 870° C RUN 37 40 80 120 160 200 240 T i m e t ( m i n ) 280 320 360 400 8 I 3. El CO a a. CO o a CO 2. o _ Figure 4.19: Effect of Particle Size on C Conversion of Obed Mountain Coal. C O to EL* 0 -0 Legend • dr=1.53mm, 870° C RUN 32 V dr=1.53mm, 930° C RUN 31 0 d^=U3mm,_930^ C_RUN_65 • dr=1.13mm, 870° C RUN 64 100 125 150 Time t (min) ' i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 175 200 225 250 275 300 325 350 "a s s. 3 fa 8 c to O c cn a. o Figure 4.20: Effect of Particle Size on C Conversion of Highvale Coal. CO CO Chapter 4. Experimental Results and Discussion 94 suggest that for temperatures below 1,000°C, the resistance to intraparticle diffusion can be negligible, and possibly chemical reaction is the rate controlling step. However, the present work is insufficient to draw a similar conclusion, because little change in carbon conversions was noted from the small change in particle size of 0.40 mm. Chapter 5 Model Testing 5.1 Introduction In Chapter 2, some popular models and correlations postulated for solid-gas reactions, especially for non-catalytic char-gas reaction, have been reviewed. The applicability of these models and correlations was considered, given the limitation of reaction schemes, the behavior of conversion-time curve represented, and computation method involved. As well, considering the required information about physical properties and their changes during the reaction, the models and correlations given below were selected to test the experimental data of this research. Equation 5.1, a generalization of the uniform reaction porous particle model, was adopted by Nguyen and Watkinson [116] to represent the main features of the char-steam gasification reactions. ~=k(X)(l-X)pl20 (5.1) where, the n-th order dependence on the steam partial pressure is used to approximate the fundamental Langmuir-Hinshelwood expression as given by Equation 2.9. The reaction order corresponding to steam based on this mechanism expression has been discussed in Section 2.2.2. In general, ignoring the inhibiting effect oiH2, the rate with respect to C02 partial pressure is approximately first order at low pressure but approaches zero order at high pressure [6]. The rate of gasification at pressure up to 30.3 kPa appears to be first 95 Chapter 5. Model Testing 96 order in PH2O, whereas at PH2O > 30.3 kPa, n ~ 0.4 [116]. As all the experiments in this work were carried out at steam partial pressure of 30.3 kPa, n in the above equation would be equal to 1 for following model testing. The reaction rate constant k is lumped into k(X), a function of conversion. The nature of the function differs depending on the model used, but usually the surface area available for reaction appears as one of the parameters. In a alternate rate expression surface area appears explicitly: ^=k(X)S(X)pnH20 (5.2) The random capillary model (RCM) [85], the random pore model (RPM) [88, 89] and modified volumetric model (MVM) [22] all are a form of Equation 5.1 with the rate constant expression: k{X) = [A - B • ln(l - X)]m (5.3) Integrating Equation 5.1 with Equation 5.3 gives 1 — X = exp A~^ - (A + B(l - m)t)~' (5-4). B Each parameter A, B, m is different corresponding to these three models, which will be shown in the following section. 5.2 Testing of The Random Capillary and Random Pore Models 5.2.1 The Model Expressions The Random Capillary Model (RCM) is a mathmatical model for reaction of porous solids, in which it is not necessary to elaborate the random nature of the capillary struc-ture. However, the number of intersections, length of pore segments, evolution of pore Chapter 5. Model Testing 97 volume and surface area are exactly and consistently derived from a single probability-density function. An application to char gasification was considered under two assump-tions: no diffusional limitations and no dependence of the intrinsic surface reaction rate on conversion. The following expressions were derived: ~ = 4ir(B1v)2(l-X)[l-4,ln(l-X)]1?2 (5.5) where ib = — (5-6) andX = 1 - exp[2Tr(B0v2t2,+ 2Bivt)} (5.7) which in the linearized form: ln(l-X) = Mt + Nt2 (5.8) where M = 2TTB0V2 and N = AivBiV B0, Bi - moments of probability density v - reaction velocity M, and N can be easily obtained by fitting the measured X vs t data to Equation 5.8 with the least square curve fitting method. Consequently, the conversions at given time are predicted. Moreover, inserting the values of these two parameters into Equation 5.5, the reaction rates will be evaluated for any conversion level. Likewise, the Random Pore Molde (RPM) [88, 89], developed by using statistical methods, considers that the reaction surfaces within the solid arise from the overlap-ping of a random set of cylinders. This model utilizes a pore structure parameter ip to characterize solid reactivity, when an arbitriary pore size distribution exists. The value of this pore structure parameter can be determined either from direct measurements on the initial pore structure of the char or extracted from an appropriate fit of the kinetic Chapter 5. Model Testing 98 reaction data to the RPM. The model expresses reaction rate as: dX _ kaCn{l-X) dt 1 — £ 0 [1 - il>ln{\ - X)] 1/2 (5.9) where the structure parameter is defined as: (5.10) Rearranging Equation 5.9 into the form, dX/dt 2 _ ka Cn Si 1-X* ~ L l - e 0 fc8 C n 5, 1 - e0 -}2ln(l - X) (5.11) where Ais - intrinsic reaction rate constant. C - local concentration of reactant gas. 5"o - initial surface area of solid per unit volume. L0 - initial total length of overlapped system per unit volume. e0 ~ initial porosity. i/> - pore structure parameter. By plotting this linear equation one can obtain the intrinsic reaction rate constant k from the intercept at X — 0, and the pore structure parameter ip from the ratio of slope to intercept. The relation between conversion and time can be found for this model by numerical integration of Equation 5.9. The surface area at any given conversion can be approxi-mated based on its initial value: S = 50(1 - X)[l - ipln(l - X))112 (5.12) Chapter 5. Model Testing 99 It is evident that both models share some common features, so that their rate expres-sions can be written in the general form as indicated in Equation 5.1 and Equation 5.3. After combination and rearranging, ~kx[A-B- ln(l - X)}m (5.13) 1 — X where A, B and kx are all constants with different values for the RPM and the RCM, But m for both models are the same value of 1/2. This equation can also represent the MVM when A = 0 and B and m are constants. 5.2.2 Testing Results and Discussion Before the actual testing of conversion-time data was undertaken, Equation 5.13 was used to assess if the RPM and PCM models are suitable for presenting the experimental results of this research. For this purpose, both sides of Equation 5.13 were squared, for m = 1/2, which yielded, tdX/tiy = k2 • A - k-1 • B • ln(l - X) (5.14) 1 — X This equation implies that the plot of [(dX/dt)/(l — X)]2 against ln(l — X) would give a straight line if these models are applicable to the situation. Figures 5.1 &; 5.2 are such plots with the results of eight different chars gasified at temperature 930°C of this research. The results at this temperature and at 870°C are all listed in Appendix F. As demonstrated, the plots show maxima at a certain level of — ln(l — X) instead of being straight lines. Most of maxima lie between — ln{l — X) of 1.181-1.557 corresponding to X of 0.693-0.789 except for least reactive chars such as Gregg River and Byron Creek (2), and Obed Mountain in which some conversion data which were over 100% were not used. Thus it is concluded that the random capillary and random pore models can not used to interpret the experimental rate data of this research, even though fits of the Figure 5.1: Listed (a). The Applicability Check of RCM and RPM to The Rate Data of The Chars o o I o X ru 14' 12-10-8-6-X 2, 4-1 2-J2 S / / / / i / / \ \ \ \ \ \ \ 2 Bio. Legend • OM RUN 60 V HC RUN 58 • CJ RjJ N 55 • HV RUN 65 •Ln(l-X) tn 5' on Figure 5.2: The Applicability Check of RCM and RPM to The Rate Data of The Chars Listed (b). Chapter 5. Model Testing 102 conversion-time data by Equation 5.8 might give high correlation coefficients as observed by Nguyen [74] and Sue and Perlmutter [113]. Their results are consistent with this work with respect to the failure of the RPM and RPM to predict the reaction dependance on conversion. For the similar type of plot, Nguyen found the linear relationship only at carbon conversions smaller than approximately 20%, while others found rate data up to 60% conversion gave straight fines in this type of plots. In the present research, the plots are essentially linear up to about — ln(l — X) = 1, or X = 0.63, but clearly deviate at higher conversions. There are several factors wich may be responsible for the failure in predicting rate data by these two models at high conversion levels. First, it is possible that particles disintegrate at high conversion; if so, the models become inapplicable. Furthermore, relatively small deviations in dX/dt at high conversion are magnified more than 20-fold in the calculation of [(dX/dt)/(1 — X)]2. The good agreement between measured and predicted conversion-time data by the models is due to the use of curve fitting, by which the deviations from the models can probably be absorbed in the fitting parameters. In the present work no further effort has been made to extract the parameters of interest for representing the whole stage only from the linear portion of the curves. If this was done, the models with these fitted parameters would fail to predict the rate data at higher conversion as indicated by Nguyen [74]. 5.3 Testing of The Modified Volumetric Model 5.3.1 The Model Expression An empirical model, introduced by Kasaoka et al. [22, 115], and refered to as the modified volumetric model (MVM), represents the relationship between the fractional gasification Xf and the gasification time t by using a simple two-constant integral rate expression, the model can accomodate the sigmoidal character of conversion-time curve, that is the Chapter 5. Model Testing 103 presence of the maximum in the rate of gasification curve. In this model, the fractional conversion is defined as the fractional weight loss during the gasification standardized by the initial fixed-carbon content on a dry and ash free basis. Wn-W x ' = -lvT ( 5 1 5 ) Note, the X used for this research is the fractional element carbon loss. By this model, the gasification rate (dXf/dt) is assumed to be directly proportional to the fraction of unreacted char (1 — Xf), and the rate constant incorporated into a function which varies with the gasification time and thus with Xf. Then, d^=k(t)(l-Xf) (5.16) This is the same as the general model Equation 5.2 with the exception of including the effect of partial pressure of gasifying agent into rate constant, which gives, upon integration, Xf = 1- exp[- f k(t)dt] (5.17) Jo The relation between the fractional gasification and reaction time is expressed as the two-constant equation below, Xf = 1 - exp(-atb) (5.18) where, a and b are two constants. This expression is the form expressed by the general model of Equation 5.4 with A = 0, and B, m as parameters. Comparing Equations 5.17 and 5.18, it can be seen that the variation of rate constant with reaction time follows the functional expression: k(t) = abtb-1 (5.19) Chapter 5. Model Testing 104 or, as the function of fractional gasification, k(Xf) = al/bb[-ln{l - Xf)}(b-lVb (5.20) which can be derived from the general expression of k(X) in Equation 5.3 by letting A = 0. B = allbb and m = {b - l)/b. Linearizing Equation 5.18, we have, M = ln(a) + bN (5.21) where: M = ln[-ln{l-Xf)} (5.22) N = ln(t) (5.23) Thus, the calculation of the constants a and b is a simple matter by means of least square method after substituting experimental X-t data into Equation 5.21. Analysis of Equation 5.18 reveals that when 6=1, this equation becomes Xf = 1 - exp(-at) (5.24) It is identical to the expression for carbon conversion-time in the volumetric or homo-geneous model for chemical reaction control [69], with a being the rate constant. When 0 < b < 1, irrespective of the constant a, there is no sigmoidal character in theXf — t curve, and subsequently the rate of gasification decreases monotonically as gasification progresses. However, when b > 1, the Xf — t curve exhibits sigmoidal character (S-shape), hence the reaction rate reaches a maximum value at some time during the course of the reaction, which could occur at any value of fractional gasification over the entire range from 0 to 1. This value and the corresponding time i.e. inflection point are given by the Chapter 5. Model Testing 105 equations: tinf = [{b-l)lab}l'h (5.25) Xinf = l-exp[-(b-l)/b] (5.26) Therefore, the MVM is more flexible in application than the RCM and RPM with regard to this aspect, because both RCM and RPM only predict the maximum rates appearing within the certain range, i.e. 1 < X < 0.393 as mentioned in Chapter 2. Moreover, based on the theoretical and empirical comparisons with the RPM, Kasaoka et al. [115] stated that the constant b is related to the physical structure of chars while a is considered to be more closely related to the intrinsic chemical reactivity of chars. The mean rate constant k can be calculated from the definition: rl />0.99 k= / k(Xf)dXf= / k{Xf)dXf (5.27) JO JO.Ol It has been found [115] that the value of k is fairly close to the rate constant at Xf = 0.5. Thus with reasonable accuracy the rate constant can be approximated by inserting Xf = 0.5 into Equation 5.20, k = fco.s = a(1/6'6[/n2](b-1)/b (5.28) At any instant time, the reaction rate is readily determined by using the rate expres-sion below if the two constants are known. This equation is obtained by substituting Equation 5.19 into Equation 5.16, d^l=abtb^{\-Xf) (5.29) dt or by substituting Equation 5.20 into Equation 5.16, ^ = a}'bb[-ln(l - Xf^-^il - Xf) (5.30) dt Chapter 5. Model Testing 106 5.3.2 Testing Results and Discussion Applicability Check Equation 5.30 can also be presented by a general form of rate expression by letting A — 0. B = allbb and rn — {b — \)/b in Equation 5.13. = J n ( l - X ) p (5.31) When it is linearized, the following form is given, ln^XJ_di^ = ln,kiBj + m . _ x)} (5.32) 1 — X Thus if a log-log plot of [(dX/dt)/(l — X)] vs — ln{l — X) gives a straight line, this equation can be applied to this set of data, which means the MVM is applicable for this case. Such a plot was illustrated in Figures 5.3 & 5.4 based on the experimental results at termperature 930°. As clearly demonstrated by these two figures, for each run the curve is straight up to — ln(l — X) = 1.5 i.e. X = 0.78, and then steeply drops down. This behavior is a indication of the applicability of the MVM to this research results up to carbon conversion of 0.78. The plots for results at 870°, not shown here, are similar. Results Presentation and Discussion The kinetic measurements from this research work all have been tested against the MVM. The conversion-time data for each run were fitted into the linear form oiXf — t relation i.e. Equation 5.21 by using the fitting program provided by Dr. Sakata. Constants a,b were evaluated based on the fitting, and the mean rate constants k were also calculated, which are tabulated in Table 5.1. Also, for each given time the predicted conversion was given. The corresponding rate value at each point was obtained according to Equation 5.30. Figures 5.5 & 5.6 are plots of conversion-time both measured and predicted for runs Legend • QS RUN 44 V GR RUN 59 • BC1 RUN 47 X BC2 RUN 49 .01 0.1 1 10 -Ln(l-X) Figure 5.3: The Applicability Check of MVM to The Rate Data of The Chars Listed (a). CN I o X "U. 10i X 0.1 o.oH 0.01 Legend • OM RUN 60 V HC RUN 58 • CT RUN 55 • HV RUN 65 i i' i i111 i'i 0.1 •Ln(l-X) V V V V —7 10 8 •8 c-v n o a. 5' Figure 5.4: The Applicability Check of MVM to The Rate Data of The Chars Listed (b). o oo Chapter 5. Model Testing 109 Table 5.1: Summary of The Fitting Results Coal T a b k R Costello 870°C 4.807xl0"3 1.228 1.484xl0-2 0.987 930°C 6.821 xlO" 3 1.261 2.238xl0"2 0.985 Highvale 870°C 2.678xl0"3 1.271 1.114xl0-2 0.998 930°C 2.823 xlO" 3 1.374 1.734X10"2 0.995 Obed Mountain 870°<7 1.297xl0-3 1.444 1.293xl0-2 0.999 *930°(7 1.283 x l O - 3 1.585 2.076xl0-2 0.998 Hat Creek 870°C 1.965xl0-3 1.302 9.960 xlO" 3 0.995 930°(7 5.212xl0"3 1.172 1.250xl0-2 0.986 Quinsam 870°C 8.378xl0"4 1.318 5.580xl0-3 0.999 930°C 1.075xl0"3 1.372 8.523xl0-3 0.998 Byron Creek(l) 930°C 6.954 xlO" 4 1.343 5.446 xlO" 3 0.999 Byron Creek(2) 930°C 3.958 xlO" 4 1.349 3.680xl0"3 0.999 Gregg River 870°C 3.263xl0-4 1.288 2.332 x l O - 3 0.998 930°C 3.307xl0-4 1.293 2.415xl0"3 0.999 For runs with the particle size Dp = 0.85-1.40 mm. * - Only part of data were used for fitting due to conversion exceeding 100% T - Gasification temperature °C. k - Mean rate constant (min - 1). Chapter 5. Model Testing 110 at temperature 870°C, and Figures 5.7 & 5.8 are for runs at temperature 930°C. The rate data versus carbon conversion together with measured value for temperature 930°C are demonstrated in Figures 5.9 & 5.10. The predicted conversion and rate data are all tabulated in Appendix F. In Table 5.1, it can be seen that the fitting of the experimental data of this research to the MVM gave high correlation coefficient R, definded as, R_ 2/ SSR NY.Xiyi-Y.XiY.yi 1 S S T 0 ^/[NYx2 - (Yxi¥}[NYy? - (Yyi)2} . where, N-the number of data point, ^-dependent variable, Si-independent variable, i = 1, 2,... N. For the same coal char, the low temperature runs gave higher R, and at the same temperature, the runs of less reactive char yielded higher R values. These findings are also graphically demonstrated in Figures 5.5-5.8. From these figures, it is shown that the experimental data of this work can generally be fitted by the MVM except for the relative reactively coal chars, such as Hat Creek, Costello chars, at high conversion as predicted by Figures 5.3 & 5.4, and at favourable reaction conditions, in which case the deviations from the MVM prediction are exhibited. By taking a close look at where the deviations arise, it is clear that in these regions the shape of curves levels off so suddenly that the MVM usually fails to predict this behavior. Table 5.1 contains all the values of a and b for different runs of this study. As it shows, all values of the constant b are larger than 1, which implies, according to the MVM, the conversion-time curve must have sigmoidal character, and the rate will reach the maximum at certain level of conversion between 0 and 1. As predicted by the model, the experimental results do have such a character which has been extensively studied in Chapter 4. Figures 5.9 & 5.10 show the comparison between measured and predicted rate. It is obvious that the maxima occur at the intermediate conversion on both curves. In general, the model predicts the experimental results of the present study adequately, Reaction Time (min) Figure 5.5: Comparison between Measured X-t and Predicted by The MVM for Runs at Temperature = 870°C (a) Reaction Time (min) Figure 5.6: Comparison between Measured X-t and Predicted by The MVM for Runs at Temperature = 870°C (b) Chapter 5. Model Testing (%) X UOISJ9AU03 uoqjDQ 2--* 1a Legend OM Fitted QS Fitted GR F_tted_ CT Fitted OM RUN 60 & QS RUN 44 GR RUN 59 CT RUN 55 150 200 250 300 350 400 450 Reaction Time t (min) 500 550 600 Figure 5.8: Comparison between Measured X-t and Predicted by The MVM for Runs at Temperature = 930°C (b) C N o X £ "o 1.25 1-0.75-0.5 0 0.25 0 + • V • • • • Legend • GR RUN 59 V HC RUN 58 • HV RUN 65 • BC1 RUN 47 GR by MVM dC...by_MVM HV__by_MVM BC1 by MVM V 1 " D 10 20 30 40 50 60 Conversion (%) 70 80 90 100 8 fa n fl? 5' Figure 5.9: Comparison between Measured dX/dt vs. X and Predicted by The MVM for Runs at Temperature = 930°C (a) 1.75 1.25-0.75-Legend • OM RUN 60 V QS RUN 44 • CJ RUN_55. • BC2 RUN 49 QS by MVM CT_bv_MVM; BC2 by MVM 0.25 0 + „ , S 10 20 30 40 50 60 70 80 90 100 110 Conversion (%) Figure 5.10: Comparison between Measured dX/dt vs. X and Predicted by The MVM for Runs at Temperature = 930°C (b) Chapter 5. Model Testing 117 Table 5.2: Activation Energies and Frequency Factors for The Chars Char OM QS HC HV CT GR E (kJ/mol) 89 80 43 79 78 7 Aa (min-1) 159 25 1 48 52 0.005 especially for those relatively less reactive chars gasified with steam. For more reactive chars, even though the shapes of corresponding curves are similar, the predicted values are always lower than experimental results, and the maxima appear earlier. Combining all the findings in the testing of models, a conclusion can be drawn that the MVM is best suitable for representing steam gasification results of relatively less reactive coal char for conversion-time and rate-converaion data, and before conversion-time curves levels off. One thing which should be kept in mind is that the Xj defined by this model has a little difference with the X used in this experimental data, as indicated in Section 5.3.1. Figure 5.11 is an Arrhenius.-type plot showing the mean rate constants, calculated by the MVM, as function of reciprocal reaction temperature for all runs of this work. Data for only two different gasification temperatures are available for most of chars, thus the fines were constructed through only these two points, and hence the parameters from these lines have very little meaning. Nevertheless, following the Arrhenius Equation, k = Aa-exp(-E/RT) (5.33) the approximate activation energies E and frequency factors Aa for all types of chars tested in this research were obtained by calculating the slopes and the intercepts of the straight fines which correspond to different kinds of coal chars respectively. The results of such work are presented in Table 5.2. Although the accuracy of the values in Table 5.2 might be highly questionable because of using two points to generate the straight fines they can at least provide a rough guide about the order of magnitude of Chapter 5. Model Testing 118 c o V) c o o ~o Ql c o <D 0.001 0.01-82.0 84.0 86.0 88.0 1/T (K-) 90.0 92.0_ *10" 5 Figure 5.11: Arrhenius-type Plot of Mean Rate Constant by The MVM for The Chars Chapter 5. Model Testing 119 temperature effects. As reported in the table, for four of the chars, the activation energy is 82±7 kJ/mol, whereas for Hat Creek char it is 43 kJ/mol and for Gregg River char the value is extremely low i.e. 7 kJ/mol for some unknown reasons. The fact of close gasification activation energies of four of these chars strongly suggests that the gasification mechanisms are quite similar. The activation energy of the order of 209 kJ/mol or more has been indicated for chemical reaction controlling gasification reaction by many previous investigators through reviewing numerous research results [8, 10], whereas it is of the order of 20 kJ/mol or less for diffusion controlling reaction. Most of the values given in above table are in between, which may means that the activation energies are not only attributed to chemical reaction, but also to diffusion processes. On the other hand, Figure 5.11 illustrates that the differences in reactivity of these chars are associated more with frequency factors than with activation energies, since the difference among these frequency factors are significant comparing with that of activation energies. In general, the higher is the rank of the parent coal, the weaker is the dependency of the rate constant on the reaction temperature. This finding is consistent with experimental results presented in Section 4.4. Equation 5.33 gives the theoretical explanation for this phenomenon. Comparison with Sakata's Results Sakata and co-workers at Okayama university in Japan have investigated the reactivity of the same types of coal samples by a thermo gravimetric analysis (TGA) method. Their sample chars were prepared by pyrolyzing the coal in a nitrogen stream for 7 min at temperature 1000°C. These coal chars were then gasified with a H20 (24%)-N2 mixture at 850°C and other temperatures, using 100 mg char sample for each run and mean particle size 1.0 mm. Another set of experiments was also performed by them using TGA at the temperature of 870°C using the chars prepared by this research. The Chapter 5. Model Testing 120 Table 5.3: Operating Conditions of Both TGA and SBR Method TGA SBR Pyrolysis Temperature (°C) 1000 930 Pyrolysis Time (min) 7 120 Sample Weight (g) 0.1 200 Gasification Temperature (°C) 850, 870 870 Partial Pressure P f f 2o (kPa) 24.3 30.3 Mean Particle Diameter D p (mm) 1 1.13 Mean Bed Height (cm) N/A 10 reactivities of the coal chars are represented by the mean rate constant k according to the MVM. The comparison of operating conditions of Sakata's and this research are detailed in Table 5.3. The main difference between these two investigations is the type of reactor employed. In this study, the experiments were carried out in the stirred-bed reactor (SBR). Table 5.4 compiles both results of this research and Sakata's together for comparison. It reveals that the k by TGA are up to 5.5 times as high as the values obtained by SBR, and the chars are essentially similar as is shown by the moisture holding capacities which are very close for the same coal chars. The value of fi were all measured by Sakata et al. [106]. The mean rate constant, as a measure of reactivity, can be correlated respectively to the initial surface areas and moisture-holding capacities of the chars by the following form of correlations, k = oi • S£2 (5.34) k = _! • fia2 (5.35) Sakata et al. [106] has no surface area data on their own chars, therefore, the data from this research were used to derive the correlation. The program POLYMATH was employed to fit all the experimental results to the above power law expression, which Chapter 5. Model Testing 121 Table 5.4: Comparison of Steam Gasification Results Measured by Sakata et al and This Research for Eight Kind of Canadian Coals Coal Sakata et al. This Research A;(TGA) / fc(SBR) n [g/S-db] Jfe(TGA)* [g/g (char.daf) • min -1] [g/g-db] fc(SBR) [min-1] Costello 0.143 0.14100 0.0784 0.129 0.0148 5.3 Obed Mountain 0.107 0.04950 0.0548 0.101 0.0129 4.2 Highvale 0.119 0.07980 0.0630 0.129 0.0111 5.5 Hat Creek 0.123 0.04450 0.0336 0.103 0.0100 3.4 Quinsam 0.100 0.00975 0.0199 0.095 0.0056 3.6 Byron Creek(l) 0.040 0.00955 0.0103 0.036 - -Byron Creek(2) 0.037 0.00900 0.0097 0.035 - -Gregg River 0.050 0.00442 0.0062 0.031 0.0023 2.7 * - The values of k(TGA) in the rig] samples prepared by UBC, by which it side column were obtained using ' values the ratio of two ks was calcu ,he char lated. are linearized form of the above correlations. By linear regression, coefficients for each correlation were calculated. The evaluation of these curve fits are given in terms of the variance, defined by: N Var. = ^[(yi)Meas - (y(xi))PTed]2/[N - (n + 1)] »=i where, y-dependent variable, x-independent variable, N-the number of data points, n-degree of polynomial. The variance is a measure of the error distribution. As well the correlation coefficient were also calculated. Table 5.5 collects all these numbers together. Substituting the coefficients into Equation 5.34 and 5.35, the correlations for each case are obtained. As is indicated in this table, the correlation coefficients for the rate constant and moisture-holding capacity data are a little higher than the values for rate constant and the initial surface area data. It seems that the reactivities of tested chars are more closely related to their moisture-holding capacity than to their initial surface area. The former is a measure of micropore volume, while the latter is a indication of surface Chapter 5. Model Testing 122 Table 5.5: The Linear Regression Results Mean Rate Constant fc (TGA) k (TGA)* k (SBR) 1.7346 - 0.1508 n a-2 1.6584 - 1.2133 Var. 0.1448 - 0.0852 R 0.9327 - 0.9277 - 43.276 -a2 - 3.1573 -Var. - 0.4617 -R - 0.8871 -d! 0.0107 0.0064 0.0037 So 0.3900 3.1573 0.2774 Var. 0.3451 • 0.5221 0.2200 R 0.8314 0.8712 0.8001 * - The values measured or evaluated for the chars prepared by Sakata et al. of larger pores. Slight differences can be found between the correlation coefficients of Sakata's data and data from this research for the same equation. Usually, the data of this work gives a slightly lower correlation coefficient than does Sakata's data. The reactivities measured in present work are always lower compared to Sakata's results at any value of the independent variable fl or 50, even though the data from both sources look similar in the way they scatter around the regression lines. This behavior, accompanied by the results calculated using the derived correlations, is illustrated in Figures 5.12 &; 5.13. According to the table and these two figures, it appears that the correlations represented by Equations 5.34 &; 5.35 are valid for either research results with different correlation coefficients as listed in Table 5.5. Based on the data reported in Table 5.4, an important point can be found, that is, = — = 12.6 (5.36) V ^ i J ^ 0.0062 k ' Chapter 5. Model Testing 123 0.1 0.01H 0 .00H 0.1 i I I I I I I I 1 Trm 10 Legend Eq'n 5.34 Eg_'n.5^ 34 # Japan • UBC 100 i I I I I I I I ! 1000 s0 (m-yg) Figure 5.12: The Relation between Mean Rate Constant Both Measured by TGA & SBR at 870° and Initial Surface Area of The Chars Chapter 5. Model Testing 124 0.1 0.01-0.00H 0.01 / / / Legend E^'n 5,35 Eq'n 5.35 • Japan • UBC i i I I I I 0.1 ft (g/g.db) Figure 5.13: The Relation between Mean Rate Constant Both Measured by TGA &: SBR at 870° and Moisture-holding Capacity of The Chars Chapter 5. Model Testing 125 ( k. 'max jmin ) SBR 0.0148 0.0023 = 6.4 (5.37) The ratio of maximum to minimum rate constants for TGA is twice as high as the ratio for the SBR. This point implies that some effects other than chemical reaction may have the range 820-930°C are 153 kJ/mol for OM and 107 kJ/mol for CT. It is quite clear that the activation energies for the case of the SBR which are shown in Table 5.2 are lower than those derived for TGA. The lower activation energies with SBR data supports the above deduction about other resistances effects on the reactivities of chars. The discrepancy between the two investigations may arise from either external mass transfer resistance or pore diffusion resistance, or both. Kwon et al. [16] found decreasing reactivity of char with increasing sample weight attributed to the mass transfer resistance of reactant gas within the bed. Calculations of the external mass transfer rate from correlations for this stirred bed (Appendix D) show that the external mass transfer resistance is negligible. Under mass transfer control, the rate would be the same for all coals, whereas by experiment it varies over a factor of 6.4 from least reactive to the most reactive coal. Since the moisture holding capacities are essentially the same for chars prepared in the SBR and the TGA, the internal diffusional resistance should be about the same for particles reacted in both reactors. Another possible reason for the discrepancy is that the temperature reading in the rotating thermocouple within the bed were too high. For char from Obed Mountain coal, assuming an activation energy of 153 kJ/mol and that the temperature of Sakata's results (870°C) is correct, a rate constant a factor of 4.2 lower than his value would occur at a temperature of 776°C i.e. at a temperature some 95°C lower. Separate tests of the accuracy of the bed thermocouple temperature were made by cross-checking temperatures in a muffle furnace with a new sheathed thermocouple, and it was found that the two influenced the reactivities of the chars. Activation energies calculated with k (TGA) over Chapter 5. Model Testing 126 thermocouples readings are within ±10°C difference. Thus the lower rate constants of the present work are not due to a large temperature arror of 100°C. The difference in results need to be further studied. Section 6.2 concerning future work contains some suggestions. 5.4 Correlating the Reactivity of Char In the above section, for comparing the present experimental results with those of Sakata et al, the reactivities of the chars tested in this work in terms of mean rate constant have been correlated to two of their properties i.e. moisture-holding capacity and initial surface area, the results of which have been presented and discussed. In this section further effort is made to correlate the reactivities of the chars to the properties of their parent coals and the operating variables. It has been agreed among coal researchers [8, 6, 114, 9] and supported by this study, that the rate of gasification for a char depends on the type/rank of parent coal, when the chars are prepared under the same operating conditions. This dependence has been shown graphically in Figure 4.18 by plotting half-life against carbon content of parent coal. Owing to the variation of gasification rate with the extent of reaction, a rate must be properly chosen to represent char reactivity in the same way for all chars. The rate at X = 0.5 of each char is selected for this purpose, which is correlated to the carbon content of parent coal as shown below: T = 930' T = 870 (5.38) (5.39) These equations were obtained by fitting the experimental (dX/dt)x=o.5 of gasification Chapter 5. Model Testing 127 experiments at the temperature of 930°C and 870°C into the linear form of above equa-tions respectively. The coefficients were readily determined after linear regression using POLYMATH. These curve fits give a variance of 0.2730 for 930°C and 0.2021 for 870°C. The correlation coefficient of these two sets of data is 0.8829 at 930°C, and 0.8673 at 870°C. A similar equation, with different coefficients to describe the relation between the reactivity of the char and carbon content of the parent coal, has been presented by Fung and Kim [17], which is introduced in Section 2.3.3. That correlation is believed to be more general for char-air gasification, as it was developed based on a large amount of gasification data, which covers more varieties of coal chars and a wider range of operating variables such as reaction temperature, particle size etc. , while the two correlations resulting from this present experimental data is relatively more specific. Figure 5.14 shows the case of 930° as an example to demonstrate this relationship by plotting experimental data and fitted results together. Because the reactivity of char is a function of several factors with different functional relations, a correlation containing four independent variables was proposed by Fung and Kim [16]. As expressed in Equation 2.41 these variables are particle size, carbon content of parent coal, partial pressure of CO 2 and reaction temperature. By using the experimental results of this work, a correlation taking operating temperature as the second rate effect factor in addition to carbon content of coal is obtained, which was solved by applying multiple variables linear regression method facilitated in POLYMATH software. The variance of 0.262 is given by the program. As shown in the equation the activation energy is 51.2 kJ/mol, which is little lower than the average of the activation energies 64 kJ/mol reported in Table 5.2. The reason for this difference might be the presence of = 8.58 C, 51,200 RT ) (5.40) Chapter 5. Model Testing 128 0.1-0 .0H o II X 33 X o.ooH 0.0001-Lege'nd FITTED • CT o HV • HC • QS OM o GR V BC(2) ' ' I ' l l 50 60 70 80 C . ( w t % ) o f P a r e n t C o a l 90 I I I I 100 Figure 5.14: Relation between Reactivity of The Chars and Carbon Content of Parent Coal. Temperature = 930° C Chapter 5. Model Testing 129 BC (2) data in the fitting of the carbon effect but not in the activation energy calculation, and its value of activation energy is probably lower than the average. Sakata et al. [21] has presented a concept to correlate the gasification reactivity of char with two properties of the parent coal which, as shown by Equation 2.39 in Section 2.3.3, are fixed carbon (FC), a chemical composition, and moisture-holding capacity, a physical structure parameter. This correlation has been extensively applied to many gasification systems with wide range of world coals including Canadian coals, by which its validity was confirmed. Multiple regression analysis of k with fixed carbon content (FC)di, and the moisture-holding capacity fi^b °f the coals of this research was found to give a correlation for temperature 930° as below, with variance=0.087. k = 0.221(F(7)-° of (5-41) Figure 5.15 is a plot of experimental k calculated by the MVM for present data versus estimated k by the above correlation. These two sets of data are fairly close for the relative higher rank coals, small deviation occurs as the rank decreases. The behavior that the experimental k are remarkablely higher than estimated value for low rank coal as observed by Sakata and Watkinson [18], however,is not obvious in this figure. Possibly it is due to the different gasification systems used, in which the reaction mechanisms are not the same. This figure suggests that the derived correlation can predict the reactivities of the chars reasonably well. 5.5 Unification of Coal Gasification Data It has been noted from many other previous studies and in this work, that although there are major differences in char reactivity as the rank of the parent coal, from which chars are produced, and other operating conditions are changed, the shapes of the conversion-time plots appeare to be quite similar. Therefore, it should be possible to normalize Chapter 5. Model Testing 130 Figure 5.15: Validity of The Correlation for Steam Gasification Reactivity of The Coals Tested in This Study, for Temperature= 930°C Chapter 5. Model Testing 131 all reactivity plots into a single curve. Such an approach through various normalizing parameters such as half-life [117], initial reactivity [118], reactivity at X = 0.5 [119], or surface area [120] has been reported in literature. Among these parameters, half-life is most popular one, as it is directly obtained from experimental data and is therefore relatively accurate and convenient to use. By contrast, the other parameters are evalu-ated by fitting a model to conversion-time data, estimated from slopes or measured at several levels of conversion, and inevitably, there are usually errors assosiated with these parameters. Mahajan et al. [117] proposed an approach by using half-life ti/2 as the normalizing parameter to unify char gasification curves in form of X-t for different temperatures, pressures, gasifying agents, and chars, into a single curve when conversion is plotted against dimensionless time r (t/ti/2). A cubic form of equation, X = AT + BT2 + CT3 (5.42) was used to correlate their X-t data up to X = 0.7 for four gasifying agents separately. Kasaoka et al. [22, 114], using the same approach, unified their data successfully, and fitted the MVM to all their experimetal data. A good approximation up to high con-version was obtained. Raghunathan and Yang [121] normalized their data at different temperatures for each of the six chars and the data from Schmal et al.[122], from Chin et al.[118] by half-life, which obtained good correlations for the empirical equation, X = 1 - [1- A(l - B j i f / * 1 - * ) (5.43) Each of these three sets of data are unified by plotting experimatal X-r. The results of this work offers further evidence that the experimental data of X-t can be unified by using half-life as the normalizing parameter. According to the findings in the literature, it seems feasible that a master curve can, with reasonable accuracy, approximate all X-r data of coal gasification up to high Chapter 5. Model Testing 132 conversion range. Raghunathan and Yang [121] based on the random pore model have derived the following expression for the unification curve: For the specific ip, the above equations are possible representations of the master curve. About 110 gasification data curves found in the literature were used by Raghunathan and Yang [121] in order to achieve the master curve. The best fit gives tp = tp — 2.7. With this value of ip, the relationship between X and r expressed by Equation 5.44 & 5.45 is shown in Figure 5.16 as the master curve. Conversion-time data measured in this study for eight types of chars and at two different temperatures are first normalized by half-life, and then plotted in Figure 5.16 as conversion versus time. As expected, unified experimental data for each run shown as discrete points in this figure are close to each other, and lie near the master curve until high conversion, where the scatter of points becomes obvious. Therefore, a fairly good unified result for the present research data was obtained with a single curve calculated by Equation 5.44 as the master curve to approximate all X versus t data of the coal gasification, which strongly supports the unification theory proposed by several coal researchers mentioned above. The extension of this unification approach [121] leads to a development of a new way for characterization of coal gasification reaction, that is by reactivity index Rc, which is defined as It is the average reactivity for a particular gasification run. Similarly, a useful quantity for a unification curve is, X = 1 - exp[-p(r +pipT2/A)} _ (1 +ipin2)1'2 - 1 (5.44) (5.45) (5.46) (5.47) o Normalized Time Figure 5.16: Unification of Coal Gasification Data from This Research co Chapter 5. Model Testing 134 Table 5.6: Average Reactivity for Each Run (dp = 0.85 — 1.40mm) Char OM QS HC HV CT BC(1) BC(2) GR t\/2 870°C 78.65 163.56 83.49 75.59 52.50 182.62 292.63 409.04 (min) 930°C 54.60 107.11 58.30 52.10 36.95 - - 379.40 Rc 870°C 4.83 2.32 4.55 5.03 7.24 2.08 1.29 0.93 (10"3 mm"1) 930°C 6.96 3.55 6.52 7.29 10.28 - - 1.00 and therefore, Rc = -—— (5.48) h/2 This equation states that the average reactivity Rc for each run is inversely proportional to its half-Me with Ru as the proportionality constant. The value of Ru calculated from the correlations reported in the literature [118, 121, 119, 122] according to Equation 5.47 were found to be very close, and assumed to be 0.38 for all the curves. With this value the reactivity index is easily evaluated, and it truly reflects the experimental data. By this method the reactivity index for each run of this research was calculated and listed in Table 5.6. Its comparison with the rate at X = 0.5 from measured data is illustrated in Figure 5.17. It is quite obvious that the average reactivities estimated by Equation 5.47 are always a little lower than those at X = 0.5 taken from the experimental data. This difference may be attributed to the determination of Ru, since it is the average value of several calculation results. For this present case it is possible for i2u to be higher than the average reactivities measured. Chapter 5. Model Testing 135 Figure 5.17: Reactivity Comparison between Measured at X — 0.5 and Estimated by Using Unification Results Chapter 6 Conclusion and Future W o r k 6.1 Conclus ion The performance of eight Western Canadian coal chars in the steam-gasification reaction with steam partial pressure 0.3 atm, at temperatures of 870°C, 900°C and 930°C, and for the particle diameters of 1.13 mm, and 1.15 mm, was investigated. The results were analyzed via several models. The principal conclusions drawn from this present work are: • In general, the initial char surface area declines sharply as the carbon content i.e. the rank, increases until a C^af = 80%, beyond which, the effect of rank on surface area is minimal. • The micrographs show that the chars of the bituminous coal have smooth surfaces, and possess a number of macropores. The chars derived from subbituminous coal and lignite appear to be very rough on the surface, which is full of interstices, layers and cracks. • Of the coal chars studied, Costello char is most reactive while Gregg River char is least reactive. The increase of the reactivity for these chars is in the order of Gregg River, Byron Creek (2), Byron Creek (1), Quinsam, Hat Creek, Obed Mountain, Highvale, Costello, that is, as the rank of the parent coal decreases. • The half-life, as a measure of the inverse of the reactivity of coal char, correlates well with fuel ratio and carbon content of the parent coal respectively, where the 136 er 6. Conclusion and Future Work 137 fuel ratio and carbon content both correspond to coal rank. The results serve as the indication of char reactivity increasing with decreasing of coal rank. The carbon conversion-time curves of this research results are sigmoidal first and then become asymptotic at high conversion, with an inflection point between 10% and 25% carbon conversion. The inflection points lead to the occurence of rate maxima in rate-carbon conversion curves. The reactivity of char in terms of inverse of half-life of reaction can be correlated adequately with the sum amount of the mineral matter contents such as CaO + MgO, and CaO + MgO + Na20 + K20. The scattered behavior of these relations indicate that the catalytic activity is not only controlled by the amount, but may depend on the dispersion of these oxides in coals and their state, as well as other factors. The influence of gasification temperature on the reactivity of char becomes stronger as coal rank decreases. On the other hand, for each type of coal, with the increase of reaction time or conversion, the sensitivity to the temperature over the range used first increases, then decreases in the region of the asymptote, and even higher conversion were resulted in by lower reaction temperature. The small change from 1.13 to 1.53 mm in average particle diameter results in little change to carbon conversion for Obed Mountain and Highvale coal chars. The random capillary and random pore models were not applicable to the rate data from this research. The modified volumetric model is applicable to this research result up to carbon conversion of 0.78. Thus the MVM can predict the experimental data of this work er 6. Conclusion and Future Work 138 adequately, for the relative less reactive coal chars and for the reactive chars at low and medium conversion or and under unfavorable reaction conditions. However, the MVM fails to represent a conversion-time curve with high degree curvature, for instance, the sudden leveling off of conversion-time curves or those with a sharp maximum in reaction rate. Activation energies can not be reliably determined because of the limited exper-imentation. Nevertheless, rough guides for their order of magnitude were deter-mined. The fact of close temperature dependence for four chars suggests that the gasification mechanisms are similar. The small temperature effect implies diffu-sional processes may be influencing the chemical reaction rate. In general, the higher is the rank of the parent coal, the weaker is the dependency of the rate constant on the reaction temperature. Comparison of the results of this study with those of Sakata's TGA experiment reveals that the mean rate constants calculated by the MVM from Sakata's research are between 2.7-5.5 times as high as the values obtained in this work. These rate constants can be correlated respectively to the initial surface areas and moisture holding capacities of their chars following the power law expressions: fc = a i • 5QJ & = o i • fi"2, which gives the correlation coefficients R between 0.80 to 0.93. It seems that for both cases the reactivities of the chars are a little more closely related to the latter than to the former. That the ratio of maximum to minimum mean rate constants for the TGA work is twice as high as that for the present work suggests that some effects other than chemical reaction may have influenced the reactivities of the chars, which supports the deductions made from the temperature effect studies. Chapter 6. Conclusion and Future Work 139 • The reactivities of the chars, expressed by the rate at X = 0.5, are fairly well correlated to the carbon contents of the parent coals as an exponential function with correlation coefficients of 0.88 and 0.87 for two temperature data, and to gasification temperature in addition to carbon content, f d X \ n r c „ 7 43 , 51,200, giving a variance of 0.262. The result of the comparing fc values calculated based on the experimental data with those predicted using the form of Sakata's correlation, fc = o.22i( JPC)-° af en°co8f (variance:0.087) shows that this correlation can predict the reactivities of the chars reasonably well with small deviation for low rank coal chars. • A unified conversion-dimensionless time curve was obtained, Data He near the mas-ter curve until high conversion, which offers further evidence to support the unifi-cation theory proposed by other coal researchers. The average reactivity Rc as a reactivity index which was developed from the unification approach was calculated and found to be lower than the value of the rate at X = 0.5 for each run. 6.2 Recommendation for Future Work In this study, only two gasification temperatures (870°C &; 930°C) were used to determine its effect on char reactivity. The activation energy of reaction is therefore still uncertain. A wider range of gasification temperature is recommended for further runs, in which temperature zones for chemical reaction domination and diffusion resistence domination would covered. Chapter 6. Conclusion and Future Work 140 In order to explain the discrepancy between the results of this work and Sakata's, a clearer picture about the gasification carried out in this research is neccesary. Investigat-ing the effects of steam flow rate and concentration on the reaction rate could be useful. These results will provide information on the importance of the role of the external mass transfer process. The relative importance of pore diffusion resistance is another aspect, which is obscure in this study. A set of gasification runs with various particle diameters for chars should conducted to verify the influence exerted by changes in particle size, since particle size is an effective factor for pore diffusion. The stirrer head (with mixing arms in different directions) as shown in Fig 3.5 is shorter than the bed height (10 cm). It needs to be impoved to ensure the completely backmixed reaction condition. Experiments with shallower beds may be useful. Measuring the surface area at different stages of reaction, although tedious, is desire-able, so that one can keep track of the change of rate with the surface area. These recommendations are to supplement and expand the scope of the present re-search. It has been found that investigation of one problem may pose several new prob-lems. We are far from a full understanding of the mystery of coal char gasification kinetics, which is still a challenge for scientists all over the world. Bibliography [1] van Heek, K.H., General Aspects and Engineering Principles for Technical Appli-cation of Coal Gasification, Carbon and Coal Gasification, J.l. Figueirdo and J.A. 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Appendix A Calculation for Steam Partial Pressure In order to achieve desired operating conditions for gasification of this study, the following calculation is necessary for determining the inlet conditions of nitrogen and water. Operating Conditions: Protai = 1 aim = 14.696 psi PH2O — 0.3 atm The flowrate of nitrogen is set to 7.5 1/min, and nitrogen temperature is 20°C. So (Tjv2)»njet = 273.15 + 20 = 293.15 K. Under this condition, the N2 molar flowrate is, , m \ 22.4 293.15 x 22.4 n n n , . N , A l N n N 2 = (TNI)IN • = 273T5 = °' 3 1 2 ( m o / / m m ) (A-1) The water molar flowrate UH2O is subsequently determined, n m o = 0.3 (A.2) nH2o + n N 2 0 3 0 3 nH2o = j j j njv2 = — x 0.312 = 0.134 (mol/min) (A.3) At the average reaction temperature of T = 900 + 273.15 = 1173.15 K, and P^2 — (1 — 0.3) atm, the nitrogen volume flowrate is TIN RT N2 PN2 0.312 x 0.08206 x 1173.15 0.7 42.908 (l/min) (A.4) 151 Appendix A. Calculation for Steam Partial Pressure 152 The pressure drop from nitrogen inlet to the reactor p measured by Nguyen [28] is 2.5 cm H2C1, which is p _ 2.5(cm H20) 1033.3(cm H20) = 0.0024(p«) (A.5) Therefore the nitrogen pressure at inlet should be set as, IT, \ _ PN2 VN2 (TN2)in , \^N2 Unlet - 7r7T7 r f 1 VN2 0.7 x 42.908 x 298.15 = + 0.0024 1173.15x7.5 = 1.020(qftn) = 14.991(pai) = 15(pai) (A.6) Since nH2o — 0.134 (mol/min), so WH2O = 0.134 x 18 = 2.412 (g/min). At temper-ature of 20°C, the density of water pn2o — 0.998 (g/ml), thus the inlet volume flowrate of water (Vu2o)iniet c a n be calculated, {VH2o)iniet = 2.412/0.998 = 2J17 (ml/min) (A.7) A p p e n d i x B The Algo r i t hm for Comput ing Carbon Conversion X The calculation of carbon conversion is essential for kinetic study of coal gasification. The algorithm for it is introduced below. The computing program is not attached as it is rather simple. (1) .N2 Flow Rate RN2 (mol/min) Nitrogen flow rate was fixed to 7.50 1/min (11.6 setting) for all the runs. As the nitrogen temperature varied with room temperature all the time, the mole flow rate was calculated based on the temperature of N2 TN2 using the equation: 22.4 R n> = T n> " 27315 (2) .Total Molar Gas Flow Rate R T (mol/min) The off gas of gasification system is assumed to be composed of nitrogen, hydeogen, carbon monoxide, carbon dioxide and methane (dry basis). For nitrogen, RN2 _ mole(N2)% ~R~T~ ~ 100% Therefore, (B.2) RN2 x 100% = mole(N2)% ( B 3 ) (3).Total Moles of Carbon Converted at Each Interval (mole) Carbon moles flow rate at time interval i is {Rc)i = (Rr)i Yl(Ci)i (B.4) 3 = 1 153 Appendix B. The Algorithm for Computing Carbon Conversion X 154 where j = 1,2,3 and conrrespond to CO, C02, CE\\. Cj stands for the concentration of these gas components in the off gas. i = 1,2,.. .n, is the counter for time interval. Converted carbon moles between interval i and i + 1 is N, fi+1fi{t)dt (B.5) Where /;(£) is determined using a set of data points (ti, (Rc)i), (t2, (#0)2) • • • (^n, {Rc)n) by means of cubic spline. As the result of spline, at any given time t the value of this function is given by the following equation: fi(t) = (Rc)i + <fc(A*) + r ;(At)2 + st(Atf (B.6) Where At. = t — Thus for any time interval the mole number of carbon converted can be calculated as shown below. No = £ + 1 fi(t)dt = (RcUAt), + f (Ar.)? + ^(AO? + ~(At)f (B.7) Where (A£)» = U+i — U. By summation the total mole of carbon converted is obtained, (Nc)T = £ f(t)dt = ^[(RcUAt), + | ( A 0 , 2 + ^ (AO? + (At)?] (B.8) (4).Total Carbon Conversion at the end of each interval X. As is indicated at the beginning of Chapter 4, carbon conversion is defined as Because the molar flow rate of carbon in off gas exhibits a sharp peak in the early stage of gasification and then it decreases slowly to lower value, the data with this kind of behavior can not be fitted by splines. Therefore, the data points after the maximum have been reached were splined, and the result was used to determine X as described Appendix B. The Algorithm for Computing Carbon Conversion X 155 above, while for first few points the trapezoid rule was applied, by which rule, between intervel i and i+1 Nc = fi(t)dt = ^{{Rc)i + (flcWi) (B.10) Therefore, ( J V c )T = / /(0* = E [ L y t ( ( i 2 c ) i + ( i 2 c ) i + l ) ] ( B - U ) 1 n — 1 Besides this difference, the calculation for X is the same as mentioned above. For other elements such as O&zH, the converted moles were calculated using the same way. Appendix C Calibration of G C The calibration was done in the "calibration mode" using samples of known composition. Six gas mixtures were employed under the identical instrumental conditions that would be used for sample analysis. Their compositions are given in Table C.l . The VISTA 401 has only a single point calibration function. This means in effect that the calibration of percentage volume versus peak area is a straight line joining the origin to the one point. Hence the % composition is defined as: Composition (volume or mole%) = Peak area x Response Factor (C.l) Because the composition of No.1 mixture was close to that of product gas, this mixture was selected as a standard gas for developing the Peak Table while others worked as references to judge how adequate is the single point calibration. Table C.2 summarizes response factors of each component in various gas mixtures and error bands about their averages. The number marked with * were not taken into account Table C.l: Composition of Gas Mixtures NO. H2 N2 CO CH4 C02 o2 1 10.00 75.04 4.99 2.98 6.99 2 56.421 1.66 5.45 11.19 24.6 3 35 15 30 2 18 4 86.421 0.498 10.000 3.080 5 86.030 1.000 10.000 2.970 6 6.667 83.333 3.333 2.000 4.667 156 Appendix C. Calibration of GC 157 Table C.2: Response Factor NO. H2 ^ 2 CO CH4 C02 1 0.066 0.796 1.071 0.233 0.132 2 0.079* 0.731* 0.826 0.222* 0.267* 3 0.072* 0.772* 0.854* 0.186* 0.246* 4 0.797 0.243 0.148* 5 0.792 0.886 0.154* 6 0.070 0.806 1.105 0.242 0.082 Error (±%) 3 1 15 2.6 23 for the average calculation, since the corresponding concentrations were far beyond the values in product gas, and the response factor of CH4 in No.3 gas deviated from main trend too much. In the gasification tests the CO2 concentration is often below that of any of the gas mixture of Table C.l . therefore, gas mixture No.6 with the lowest GO2 concentration was used to obtain the response factor for CO2- In addition the individual response factor for CO scattered to the high degree as shown above, and their average of them was calculated for the Peak Table. Values for other gases all fall within the error band of ±3%, which was considered to be acceptable. All the values in Table C.2 are the averages of the response factors from three injections. Quite often, for many reasons, such as the presence of high-boiling residues or of water remaining in the column, the stationary phase bled away. Therefore recalibration with gas No.6 became necessary each time before the actual analysis began to check whether or not the old calibration needed to be updated. This tedious procedure was considered necessary to minimize experimental errors. Following is the method AB used by VISTA 401 for the research. The Peak Table included is the one used for that particular run when this copy of method was printed. Appendix C. Calibration of GC 158 SINGLE CHANNEL METHOD: AB 8 :34 19 JUN 90 SECTION l : BASIC PAGE 1 ANALYSIS PARAMETERS CHANNEL: 3 CALCULATION: ES A R E A / H T : A STOP TIME: 5 . 5 0 NUMB EXPECTED PKS: 40 EQUILIBRATION T IME: 0 UNRETAI NED PK TIME: 0 .00 UN I DENT PK FACTOR: 0 .000000 S L I C E WIDTH: 10 PAGE 2 SAMPLE PARAMETERS RUN T Y P E : A SAMPLE ID: NO 10 DIVISOR: F. 000000 AMT STD: 1.000000 MLTPLR: 1.000000 PAGE 3 REPORT INSTRUCTIONS WHERE TO REPORT: R C O P I E S : 1 T I T L E : GASIFICATION HV H RUN #68 FORMAT: N DECIMAL P L A C E : 3 RESULT UNITS: M0L?6 REPORT UN I DENT PKS: Y REPORT INSTRUMENT CONDITIONS: N PAGE 4 PLOT INSTRUCTIONS P L O T : Y ZERO O F F S E T : 5 ANNOTATION RETENTION T IME: Y PLOT CONTROL: Y TIME T ICKS: Y TIME EVENTS: N PK START/END: N PAGE 5 CHART SPEED PAGES OR CM/MIN: C INIT VALUE: 1 .0 PAGE 6 PLOT ATTEN INIT PLOT ATTEN: 64 Appendix C. Calibration of GC 159 SECTION 2: TIME EVENTS PAGE 1 L I N E * TIME EVENT VALUE 1 0 . 0 0 PR i0 2 0 .00 SN 2 3 0 .00 1% 5 .0 4 0 .00 WI 4 SECTION 3: PEAK TABLE PAGE 1 STD PK#: 0 R E L A T I V E RETEN PK#: 0 RESOLUTION PKtt: 0 RESOLUTION MINIMUM: 0 . 0 FACT/6: 5 . 0 IDENTIFICATION TIME WINDOWS REF %: 10 MIN: NON REF %: 5 MIN: 0. 00 0 .00 PAGE 2 PK# TIME NAME 1 1.60 H2 2 2 . 0 ? N2 3 2 .54 CO 4 3 . 1 7 CH4 5 5 .10 C02 FACTOR 0 .085000 0 .970000 7 5 . 0 0 0 0 0 0 .972543 5 . 0 0 0 0 0 0 0 .286000 0 .920000 AMOUNT REF GR# MUST LO MUST HI 10 .00000 0 .000000 0 . 0 0 0 0 0 0 0 .000000 0 . 0 0 0 0 0 0 0 .000000 0 . 0 0 0 0 0 0 3 . 0 0 0 0 0 0 0 .000000 0 . 0 0 0 0 0 0 7 .000000 0 .000000 0 .000000 Appendix D Evaluation of External Mass Transfer Rate Basic parameters for the calculation (1-steam, 2-nitrogen): Molecular Weight MA = 18, M 2 = 28 Reaction Temperature T = 273 + 870 = 1143 K Particle Diameter dp = 0.113 cm Reaction Chamber Diameter(i.d.) D = 6.3 cm Bed Height H = 10 cm Molar Flow Rate nx = 0.134 mol/min, n2 = 0.312 mol/min Assuming: Bed Porosity e = 0.5 Fraction of non — dif fusion species y = 0.7 The calculation of mass transfer coefficient km is based on Sherwood Number correlation (Equation 2.11): S h ^Kndpy = z 2 + 0.6Z(RE)1J2Sc1'3 ( D . l ) ^1,2 where: 1. Z)i ]2-Binary diffusion coefficient. According to Fuller, Schettler, and Gidding's rela-tion: D _ 10- 3T 1- 7 5[(M 1 + M 2 ) / ( M 1 M 2 ) ] 1 / 2 p t[(sWi / 3 + (^) 2 / 3 ] 2 160 Appendix D. Evaluation of External Mass Transfer Rate From Table 2.IB [123], (Si/)i = 12.7, (Si/)2 = 17.9. Therefore, 1CT3 x 1U31-75[(18 + 28)/(18 x 28)]1/2  1 , 2 ~ l ^ J 1 / 3 + 17.91/3]2 = 2.77 cm?js 2. Sc-Schmidt Number= —£—, For the gas mixture at 870°C, the viscosity, pi = 0.041 cp, p2 — 0.044 0.3/xxMi72 + 0.7p2M2/2  1 1 ~ 0.3M a 1 / 2 + 0.7M 2 1 / 2 = 0.043 cp = 4.3 x 10 - 4 g/cm • s The average molecular weight, Mc = 0.3M1 + 0.7M2 = 0.3x18 + 0.7x28 = 25 g/mol Thus, the density for this mixture, P = 1 x 25 0.08206(273 + 870) 0.267 g/mol = 2.67 x 10"4 g/cm3 Therefore Sc = 4.3 x 10"4 = 0.58 2.67 x 10-4 x 2.77 3. (#e)p-Reynolds Number= ^ The volumetric flowrate of the gas mixture is: _ ( n i + n2)RT PT (0.134 + 0.312) x 0.08206(273 + 870) 1 = 41.83 l/min = 0.0418 m3/min Appendix D. Evaluation of External Mass Transfer Rate 162 So, the velocity of the gas is: V 0.0418 u TT(D/2)2 3.14[(6.3 X 10_2)/2]2 13.42 m/min = 22.4 cm/s (D.9) The Reynolds Number is evaluated, 0.113 x 22.4 x 2.67 x IO"4 1 _ (Re)p = : = 1-57 (D.10) v , p 4.3 x 10-4 v ; Thus, the external mass transfer coefficient is ready to be calculated, kmdpy Therefore, 2 + 0.63 x 0.581/3 x 1.571/2 = 2.66 (D.ll) 2.66£> 1 2 2.66 x 2.77 ( / T % , *- = ^ f = Un^T7 =9315 <ai2> The external mass transfer rate is evaluated using the equation below, Rate CH2o (D.13) Where, The total surface area : ar = —-—; X H (D.14) dp 4 v ; 6(1 - 0.5)3.14 x 6.32 1 r t = - i x 10 0.113 4 = 8271.6cm2 The concentration of steam : CH20 — T^ p; (D.15) RT 0.3 0.08206 x 1143 = 0.0032 mol/l = 3.2 x 10"6 mol/cm3 External mass transfer rate: Rate = 93.15 x 8271.6 x 3.2 x 10 - 6 = 2.47 mol/s = 148.2 mol/min (D.16) Appendix E Ash Composition Data The following oxides composition data for the coals studied in this work are taken from a databank[105] and the analysis results of Sakata et al. [106]. No data is availible for Gregg River coal. In this table the values for Costello and Quinsam Coals are from the first source [105], while the others are all from Sakata et al. [106]. The sums of these oxides can not be 100—the experiment and some unreported constituents. 163 Appendix E. Ash Composition Data Table E.l: The Metal Oxides Composition of Ash (wt%) Coal BC (1) HC OM BC (2) QS CT HV Acidic Si02 53.68 46.61 59.59 51.10 29.03 32.80 54.18 Al2Oz 31.91 32.23 23.74 33.59 22.48 17.20 24.92 Ti02 1.66 1.26 0.68 2.18 1.41 0.55 0.57 Basic Fe203 1.88 12.30 3.22 2.26 6.19 5.25 3.08 CaO 7.07 3.22 6.82 4.25 31.10 14.97 10.88 MgO 1.09 1.93 1.30 0.88 0.21 3.42 0.96 Na20 0.23 0.16 0.05 0.90 0.10 10.47 2.18 K20 0.75 0.68 0.63 0.50 0.13 0.85 0.60 Miscellaneous P2O, 0.10 0.31 0.05 1.03 0.71 0.00 0.11 Appendix F Experimental Conditions and Results In this research, eight Western Canada coals were subjected to gasification with steam under various operating conditions for kinetic study. A summary of experiment work, including operating conditions employed and corresponding results, are made as shown in Table F. l . The raw data about products gas composition for all the runs at different time inter-vals are given in Table F.2 (a)-F.21 (a), which were measured by GC. The composition of nitrogen is not included in this table, it can be calculated by difference. Table F.2 (b)-F.21 (b) compiles the data from each run as to the moles of element converted during reaction as well as the carbon conversion. Carbon conversion was worked out based on the data in Table F.2 (a)-F.21 (a) according to Equation 4.1 as detailed in Appendix B. UBC subroutine DSPLFT was used to find the spline function for carbon conversion-time data. By the spline result, reaction rate of each gasification run was determined by taking the first derivative of it employing UBC subroutine DSPLN. The RPM, RCM and MVM were checked for their feasibility to the present research results. Also the MVM was used to predict the reaction rate. All the results of these work are compiled into Table F.2 (c)-F.21 (c). The fitted conversion data by the MVM are listed in Table F.22. The reproducibility of experiment is demonstrated in Table F.23, which is the results of two identical runs. 165 Appendix F. Experimental Conditions and Results 166 Table F.l: Summary of Operating Conditions and Results for All Gasification Runs Coal {Nc)char Dp Run T {Nc)net Maximum Rx=0.5 (mole) (mm) (No) ( ° C ) (mole) t (min) X (mole%) (min'1) Costello 5.35 0.85-1.40 51 870 5.112 275 96.278 0.956 55 930 4.488 150 93.205 1.398 6.34 0.85-1.40 64 870 5.747 291 97.602 0.529 65 930 6.257 202 96.641 1.005 Highvale 32 870 6.713 325 95.359 0.569 6.84 1.40-1.65 31 930 6.707 160 90.905 1.098 33 900 6.694 195 97.304 0.857 6.94 0.85-1.40 62 870 6.505 259 98.157 0.605 60 930 5.975 270 105.488 0.890 Obed Mountain 37 870 6.490 390 98.326 0.635 6.96 1.40-1.65 43 930 6.463 300 103.759 0.751 36 900 6.258 305 103.675 0.797 Hat Creek 4.73 0.85-1.40 54 870 4.488 300 91.788 0.627 58 930 4.347 223 86.732 0.807 Quinsam 8.60 0.85-1.40 45 870 7.90 465 91.497 0.284 44 930 7.835 380 95.189 0.409 Byron Creek(l) 6.19 0.60-1.65 47 930 5.598 390 89.448 0.284 Byron Creek(2) 9.37 0.60-1.65 49 930 7.840 437 67.490 0.145 Gregg River 9.73 0.85-1.40 57 870 8.349 493 58.020 0.097 11.10 0.85-1.40 59 930 10.036 484 59.560 0.102 Appendix F. Experimental Conditions and Results 167 Ta.ble F.2: R U N # 31 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results. N O . t H2 CO CH4 C02 (min) (mole %) 1 0 . 0. .464 0 .084 0. .000 0 . 046 2 5 . 6. .859 S .982 0. .062 0 . 075 3 1 5 . 20. .194 14 .746 0. .182 2 . 587 4 3 0 . 19. .654 13 .824 0. .293 2 . 802 5 4 5 . 18. .612 12 .673 0. .175 2 . 816 6 6 0 . 17. .872 11 .157 0. .155 3 . 282 7 7 5 . 15. .906 8 .341 0. .134 3 . 572 8 9 0 . 12. .911 4 .333 0. .068 3 . 718 9 105 . 6. .362 0 .746 0. .020 2 . 439 10 120 . 2. .551 0 .114 0. .009 1. 028 11 1 3 0 . 1. .605 0 .051 0. .000 0 . 641 12 1 4 0 . 1. .071 0 .040 0. .000 0 . 400 13 150 . 0. .638 0 .000 0. .000 0 . 196 14 160 . 0. .541 0 .000 0. .000 0 . 139 t C CONVERTED H O X (min) (mole) (mole) (mole) (mole%) 0 . 0 .000 0 .000 0. .000 0 .000 5 . 0 .0S5 0 .131 0. .056 0 .824 15 . 0. .598 1 .398 0. .658 8 .916 3 0 . 1. .878 4 .436 2. .121 2 7 . 9 9 7 4 5 . 3. .046 7 . 2 4 6 3, .472 4 5 . 4 1 8 6 0 . 4 .102 9 . 8 3 5 4. .729 6 1 . 1 6 6 7 5 . 5. .000 1 2 . 1 3 7 5. .845 74 .551 9 0 . 5. .631 • 13 .968 6. .698 8 3 . 9 5 3 1 0 5 . 5. .941 15 .057 7. .182 8 8 . 5 8 6 1 2 0 . 6. .037 1 5 . 4 6 5 7. .359 9 0 . 0 0 3 1 3 0 . 6. .065 1 5 . 5 9 5 7. .413 9 0 . 4 3 0 1 4 0 . 6. .083 15 .678 7. .447 9 0 . 6 9 3 150 . 6. .093 15 .731 7. .466 9 0 . 8 3 9 160 . 6. .097 1 5 . 7 6 5 7. .475 9 0 . 9 0 5 TOTAL CONVERTED ( g ) : C - 73 .225 H - 15 .765 0 - 1 1 9 . 5 9 7 t X d X / d t * d X / d t TY TX (min) (raol%) ( 1 / m i n ) ( 1 / m i n ) ( 1 / m i n ) 0 . 0 .000 0 .354 0 .000 0 . 1 2 5 0 .000 6. 2 .259 0 .520 0 . 4 5 5 0 . 2 8 3 0 .023 1 1 . 5 .921 0 .802 0 .671 0 . 7 2 6 0 .061 1 7 . 11 .038 1 . 045 0 .814 1 .380 0 .117 2 2 . 17 .291 1 . 2 0 5 0 .903 2 .124 0 .190 2 8 . 24 .158 1 .267 0 .950 2 .791 0 .277 3 3 . 31 .105 1 .244 0 . 965 3 . 259 0 .373 3 9 . 37 .858 1 .202 0 . 957 3 .744 0 .476 44 . 44 .355 1 .151 0 .930 4 .280 0 .S86 5 0 . 50 .547 1 .093 0 . 889 4 .887 0 .704 5 5 . 56 .416 1 .034 0 .836 5 . 6 2 9 0 .830 6 1 . 61 .955 0 .973 0 .774 6 . 547 0 .966 6 6 . 67 .139 0 .904 0 . 7 0 5 7 .562 1 .113 7 2 . 71 .899 0 .819 0 . 6 3 3 8 .504 1 .269 7 7 . 76 .156 0 .722 0 .562 9 .158 1 .434 8 3 . 79 .846 0 . 615 0 . 4 9 6 9 . 309 1 .602 88 . 82 .927 0 .501 0 . 437 8 .598 1 .768 94 . 85 .363 0 .384 0 . 389 6 .881 1 .922 9 9 . 87 .190 0 .281 0 .353 4 . 8 0 5 2 . 0 S 5 105 . 88 .488 0 .192 0 .328 2 . 789 2 .162 110 . 89 .344 0 .122 0 . 3 1 3 1 . 3 0 5 2 .239 116 . 89 .872 0 .073 0 . 307 0 .522 2 .290 121 . 90 .192 0 .046 0 . 305 0 .221 2 .322 1 2 7 . 90 .401 0 .031 0 .307 0 . 1 0 5 2 .344 132 . 90 .549 0 . 0 2 3 0 . 311 0 . 061 2 .359 138 . 90 .663 0 .018 0 . 3 1 5 0 . 038 2 .371 1 4 3 . , 90 .752 0 .014 0 . 3 1 9 0 . 0 2 3 2 .381 1 4 9 . 90 .821 0 .011 0 .324 0 . 014 2 .388 154 . 90 .874 0 . 009 0 . 3 3 0 0 . 0 0 9 2 .394 1 6 0 . 90 .919 0 .008 0 . 3 3 5 0 . 0 0 7 2 . 399 N O T E : t - R e a c t i o n t i m e e v e n l y d i v i d e d i n t o 30 i n t e r v a l s . X - C a r b o n c o n v e r s i o n r e s u l t i n g f r o m UBC s u b r o u t i n e D S P L F T . d X / d t - R a t e c a l c u l a t e d u s i n g UBC s u b r o u t i n e D S P L N . * d X / d t - R a t e c a l c u l a t e d u s i n g t h e MVM(xlOO) TY • ( ( d X / d t ) / ( l - X ) ] * * 2 T X « - L n ( l - X ) Appendix F. Experimental Conditions and Results 168 Table F.3: R U N # 32 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results. NO . t H2 CO CH4 C02 (min) (mole %) 1 0. 0.196 0.025 0.000 0.069 2 5. 4.597 4.727 0.057 0.381 3 16. 16.834 7.174 0.139 4.644 4 25. 16.335 6.425 0.145 4.717 S 40. 15.536 6.529 0.164 5.636 6 55. 15.860 6.162 0.124 4.657 7 70. 12.967 5.082 0.106 4.500 8 85. r3.695 4.718 0.102 4.5SS 9 100. 13*. 112 3.443 0.081 4.661 10 115. 11.106 2.402 0.073 4.145 11 130. 9.816 1.83S 0.0S2 3.866 12 145. 7.931' 1.483 0.079 3.384 13 160. 6.317 0.895 0.025 3.30B 14 176. S.971 0.693 0.021 2.884 15 190. S.292 0.387 0.014 2.378 16 205. 4.685 0.304 0.012 2.065 17 225. 2.910 0.197 0.011 1.742 18 245. 3.049 0.159 0.009 1.619 19 265. 2.112 0.072 0.005 1.018 20 295. 1.248 0.020 0.000 0.596 21 325. 0.802 0.000 0.000 0.303 t CONVERTED X C H O (min) (mole) (mole) (mole) (mole%) 0. 0.000 0.000 0.000 0.000 5. 0.045 0.084 0.048 0.671 16. 0.429 1.081 0.546 6.387 25. 0.873 2.391 1.162 12.998 40. 1.633 4.464 2.251 24.332 55. 2.391 6.538 3.334 35.620 70. 3.022 8.346 4.235 45.010 85. 3.594 9.950 5.073 53.S42 100. 4.126 11.605 5.878 61.463 115. 4.S52 13.022 6.555 67,810 130. 4.894 14.199 7.117 72.910 145. 5.185 15.182 7.600 77.239 160. 5.425 15.933 8.013 80.818 176. 5.642 16.610 8.401 84.045 190. 5.793 17.151 8.676 86.301 205. 5.922 17.659 8.915 88.209 225. 6.063 18.157 9.180 90.322 245. 6.186 18.539 9.412 92.147 265. 6.280 18.886 9.593 93.S57 295. 6.356 19.187 9.740 94.677 325. 6.401 19.382 9.830 95.359 t X d X / d t *dX/dt TY TX (min) (mol%) (1/min) (1/min) (1/min) 0. 0.000 0.139 0.000 0.019 0 .000 11. 3.316 0.507 0.459 0.275 0 .034 22. 10.533 0.739 0.549 0.683 0 .111 34. 19.181 0.788 0.S76 0.951 0 .213 45. 27.922 0.761 0.571 1.116 0 .327 56. 36.089 0.690 O.5S0 1.164 0 .448 67. 43.389 0.618 0.521 1.191 0 .569 78. 50.025 0.569 0.487 1.294 0 .694 90. 56.166 0.527 0.448 1.446 0 .825 101. 61.761 0.467 0.408 1.494 0 .961 112. 66.619 0.400 0.371 1.437 1 .097 123. 70.757 0.341 0.336 1.3S7 1 .230 134. 74.314 0.296 0.305 1.330 1 .359 146. 77.422 0.259 0.276 1.319 1 .488 157. 80.146 0.228 0.250 1.314 1 .617 168. 82.537 0.199 0.225 1.301 1 .745 179. 84.606 0.170 0.203 1.220 1 .871 191. 86.357 0.143 0.184 1.098 1 .992 202. 87.832 0.122 0.168 1.001 2 .106 213. 89.113 0.108 0.153 0.979 2 .218 224. 90.263 0.098 0.140 1.017 2 .329 235. 91.321 0.090 0.127 1.077 2 .444 247. 92.272 0.079 0.115 1.055 2 .560 258. 93.089 0.066 0.104 0.909 2 .672 269. 93.739 0.050 0.096 0.638 2 .771 280. 94.223 0.037 0.090 0.412 2 .851 291. 94.587 0.029 0.086 0.280 2 .916 303. 94.880 0.024 0.082 0.221 2 .972 314. 95.133 0.021 0.079 0.193 . 3 .023 32S. 95.366 0.020 0.076 0.196 3 .072 NOTE: t - Reaction time evenly divided into 30 intervals. X - Carbon conversion resulting from UBC subroutine DSPLFT. dX/dt - Rate calculated using UBC subroutine DSPLN. *dX/dt - Rate calculated using the MVM(xlOO). TY - I(dX/dt)/(l-XJ] **2 TX - -Ln(l-X) TOTAL CONVERTED (g) : C - 76.881 H - 19.382 O -157.282 Appendix F. Experimental Conditions and Results 169 Table F.4: RUN# 33 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Resvdts. NO. t H2 CO CH4 C02 (min) (mole %) 1 0. 0 .131 0 .031 0, .004 0 .000 2 6. 21 .546 12. .873 0. .221 3 .691 3 11. 17 .327 11. .563 0. .506 3 .189 4 20. 18 .090 11, .097 0. .140 3 .470 s 35. 15 .286 10, .591 0. .154 4 .589 6 50. 16 .360 8, .781 0. .160 3 .340 7 65. 15 .864 8. .369 0. .386 4 .027 8 80. 15. .493 6. .276 0. .096 4 .217 9 96. 12. .891 4. .223 0. .087 3 .883 10 110. 10, .973 2. .989 0. .070 3 .807 11 126. 8. .714 1. .834 0. .045 3 .325 12 140. 5. .473 0. .555 0. .016 2 .270 13 155. 2. .499 0. .008 0. .008 1 .030 14 175. 1. .191 0. .013 0. .002 0 .704 15 195. 0. .637 0. .000 0. 000 0 .263 t CONVERTED X C H O (min) (mole) (mole) (mole) (mole%) 0. 0.000 0.000 0.000 0.000 6. 0.253 0.665 0.306 3.784 11. 0.634 1.614 0.758 9.471 20. 1.241 3.098 1.483 18.541 35. 2.285 5.457 2.805 34.128 50. 3.193 7.543 3.966 47.700 65. 4.003 9.737 4.989 59.795 80. 4.768 11.825 6.009 71.232 96. 5.372 13.703 6.871 80.252 110. 5.776 14.999 7.477 86.280 126. 6.137 16.187 8.049 91.677 140. 6.335 16.894 8.385 94.644 155. 6.426 17.278 8.554 95.991 175. 6.474 17.488 8.651 96.709 195. 6.514 17.612 8.728 97.304 t X dX/dt *dX/dt TY TX (min) (mol%) (1/min) (1/min) (1/min) 0. 0.000 0.636 0 .000 0 .405 0 .000 7. 4.668 0.808 0 .895 0 .717 0 .048 13. 10.856 1.004 1 .047 1 .269 0 .115 20. 17.900 1.073 1 .100 1 .707 0 .197 27. 25.121 1.069 1 .101 2 .037 0 .289 34. 32.184 1.026 1 .072 2 .288 0 .388 40. 38.857 0.959 1 .025 2 .461 0 .492 47. 45.102 0.900 0 .968 2 .687 0 .600 54. 50.976 0.848 0 .903 2 .995 0 .713 61. 56.529 0.805 0 .831 3 .426 0 .833 67. 61.813 0.767 0 .756 4 .037 0 .963 74. 66.817 0.718 0 .677 4 .686 1 .103 81. 71.435 0.652 0 .600 5 .218 1 .253 87. 75.585 0.583 0 .526 5 .693 1 .410 94. 79.280 0.517 0 .457 6 .233 1 .574 101. 82.553 0.457 0 .394 6 .868 1 .746 108. 85.444 0.404 0 .335 7 .698 1 .927 114. 87.996 0.355 0 .282 8 .756 2 .120 121. 90.214 0.304 0 .234 9 .634 2 .324 128. 92.074 0.249 0 .193 9 .873 2 .535 134. 93.564 0.194 0 .159 9 .119 2 .743 141. 94.690 0.141 0 .134 7 .062 2 .936 148. 95.482 0.097 0 .115 4 .570 3 .097 155. 96.017 0.065 0 .103 2 .629 3 .223 161. 96.375 0.043 0 .095 1 .420 3 .317 168. 96.617 0.030 0 .090 0 .795 3 .386 175. 96.799 0.025 0 .086 0 .632 3 .442 182. 96.969 0.025 0 .083 0 .689 3 .496 188. 97.138 0.025 0 .079 0 .761 3 .554 195. 97.305 0.025 0 .075 0 .855 3 .614 NOTE: t - Reaction time evenly divided into 30 intervals. X - Carbon conversion resulting from UBC subroutine DSPLFT. dX/dt - Rate calculated using UBC subroutine DSPLN. *dX/dt - Rate calculated using the MVM(xlOO). TY - {(dX/dt)/(l-X)]**2 TX - -Ln(l-X) TOTAL CONVERTED (g): C - 78.228 H - 17.612 O -139.649 Appendix F. Experimental Conditions and Results 170 Table F.5: R U N # 36 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibihty Check and The Model Testing Results. NO . t H2 CO CH4 C02 (min) (mole %) 1 0. 0.086 0.027 0.000 0.000 2 10. 14.114 8.416 0.165 3.866 3 20. 14.722 8.953 0.167 3.682 4 35. 15.569 9.879 0.219 3.654 5 50. 13.693 8.713 0.181 2.673 6 70. 14.204 8.374 0.-224 3.591 7 90. T3.667 6.198 0.153 3.928 8 110. 12.S71 4.325 0.13S 3.834 9 130. 8.740 2.425 0.083 3.113 10 155. 4.884 1.731 0.049 1.504 11 185. 2.197 1.136 0.022 0.475 12 215. 0.907 0.422 0.004 0.192 13 245. 0.437 0.155 0.000 0.197 14 275. 0.244 0.0S4 0.000 0.081 15 305. 0.256 0.017 0.000 0.075 t CONVERTED X C H O (min) (mole) (mole) (mole) (mole%) 0. 0.000 0.000 0.000 0.000 10. 0.265 0.616 0.343 4.231 20. 0.805 1.878 1.038 12.8S9 35. 1.673 3.910 2.133 26.737 50. 2.459 5.793 3.097 39.299 70. 3.458 8.197 4.337 55.260 90. 4.413 10.607 5.596 70.515 110. S.161 12.790 6.647 82.463 ' 130. S.693 14.468 7.440 90.970 155. 6.073 15.654 8.018 97.039 185. 6.312 16.348 8.343 100.860 215. 6.414 16.633 8.472 102.493 245. 6.457 16.753 8.533 103.174 275. 6.480 16.814 8.569 103.542 305. 6.488 16.858 8.583 103.675 t X dX/dt *dX/dt TY TX (min) (mol%) (1/min) <1/min) (1/min) 0. 0.000 0.384 0.000 0.148 0 .000 11. 4.874 0.621 0.658 0.426 0 .050 21. 13.116 0.893 0.882 1.055 0 .141 32. 22.893 0.942 0.980 1.492 0 .260 42. 32.496 0.880 1.006 1.701 0 .393 53. 41.473 0.830 0.987 2.011 0 .536 63. 50.013 0.797 0.932 ' 2.540 0 .693 74. 58.283 0.776 0.848 3.463 0 .874 84. 66.236 0.730 0.739 4.671 1 .086 95. 73.505 0.648 0.619 5.991 1 .328 105. 79.849 0.557 0.499 7.643 1 .602 116. 85.207 0.462 0.386 9.744 1 .911 126. 89.571 0.369 0.286 12.496 2 .261 137. 92.980 0.282 0.201 16.149 2 .656 147. 95.574 0.215 0.132 23.520 3 .118 158. 97.565 0.167 0.075 46.968 3 .715 168. 99.117 0.129 0.028 214.090 4 .729 179. 100.306 0.098 189. 101.199 0.073 200. 101.858 0.053 210. 102.335 0.038-221. 102.682 0.028 231. 102.940 0.021 242. 103.135 0.016 252. 103.293 0.014 263. 103.424 0.011 273. 103.525 0.008 284. 103.595 0.005 294. 103.643 0.004 305. 103.679 0.003 NOTE: t - Reaction time evenly divided into 30 intervals. X - Carbon conversion resulting from UBC subroutine DSPLFT. dX/dt - Rate calculated using UBC subroutine DSPLN. *dx/dt - Rate calculated using the HVM(xlOO). TY - (<dX/dt)/(l-X)]**2 TX - -Ln(l-X) TOTAL CONVERTED (g) : C - 77.921 H - 16.858 O -137.327 Appendix F. Experimental Conditions and Results 171 Table F.6: R U N # 37 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results. N O . t H2 C O CH4 C 0 2 (min) (mole %) 1 0. 0. .191 0 .003 0. 000 0 .024 2 10. 12. .418 4 .888 0. 102 3 .768 3 25. 13. .063 6 .625 0. 137 3 .811 4 45. 14. .236 7 .087 0. 173 4 .203 5 65. 13. .496 6 .145 0. 156 4 .249 6 85. 14, .429 5 .047 0. 146 4 .784 7 105. 12, .333 3 .868 0. 123 4 .673 8 125. 10, .776 3 .010 0. 109 3 .915 9 150. 8, .107 1 .924 0. 072 3 .141 10 180. 4. .535 1 .266 0. 047 1 .694 11 213. 2, .569 1 .101 0. 028 1 .029 12 240. 1, .587 0 .813 0. 016 0 .549 13 270. 0. .934 0 .463 0. 007 0 .215 14 301. 0, .647 0 .251 0. 004 0 .171 15 330. 0 .353 0 .138 0. 001 0 .084 16 360. 0 .343 0 .069 0. ,000 0 .038 17 390. 0 .172 0 .030 0. .003 0 .051 t CONVERTED X C H O (min) (mole) (mole) (mole) (mole%) 0. 0.000 0.000 0.000 0.000 10. 0.173 0.504 0.246 2.668 25. 0.755 2.065 1.048 11.634 45. 1.665 4.371 2.277 25.658 65. 2.565 6.645 3.503 39.522 85. 3.411 9.016 4.710 52.562 105. 4.169 11.243 5.844 64.232 125. 4.774 13.051 6.772 73.559 150. 5.335 14.847 7.651 82.207 180. 5.753 16.173 8.315 88.639 213. 6.026 16.932 8.725 92.850 240. 6.182 17.299 8.949 95.256 270. 6.277 17.535 9.076 96.716 301. 6.329 17.690 9.146 97.521 330. 6.359 17.780 9.187 97.974 360. 6.373 17.842 9.207 98.198 390. 6.381 17.898 9.219 98.326 t X dX/dt *dX/dt TY TX (min) (mol%) (1/min) (1/min) (1/min) 0. 0 .000 0.210 0, .000 0 .044 0 .000 13. 4 .172 0.488 0, .524 0 .259 0 .043 27. 12 .487 0.695 0. .622 0 .630 0 .133 40. 22 .144 0.729 0. .646 0 .876 0 .250 54. 31 .798 0.703 0. .631 1 .063 0 .383 67. 41 .055 0.673 0. .594 1 .305 0 .529 81. 49 .873 0.636 0. .541 1 .612 0 .691 94. 58 .116 0.586 0. .479 1 .958 0 .870 108. 65 .526 • 0.512 0. .415 2 .209 1 .065 121. 71 .885 0.434 0. .354 2 .385 1 .269 134. 77 .225 0.361 0. .299 2 .507 1 .480 148.. 81 .598 0.290 0. .250 2 .487 1 .693 161. 85 .060 0.227 0. .210 2 .308 1 .901 175. 87 .767 0.178 0. .177 2 .115 2 .101 188. 89 .908 0.142 0. .150 1 .991 2 .293 202. 91 .641 0.117 0. .128 1 .957 2 .482 215. 93 .096 0.101 0. .108 2 .142 2 .673 229. 94 .356 0.086 0. .091 2 .299 2 .875 242. 95 .378 0.066 0. .076 2 .019 3, .074 256. 96 .134 0.048 0. .065 1 .522 3, .253 269. 96 .685 0.035 0. .057 1 .129 3, .407 282. 97 .101 0.027 0. .050 0 .865 3, .541 296. 97 .421 0.021 0. .046 0 .670 3 .658 309. 97 .678 0.017 0. .042 0 .548 3 .763 323. 97 .883 0.013 0. .039 0 .393 3 .855 336. 98 .035 0.009 0. .036 0 .226 3, .930 350. 98 .140 0.006 0. .035 0 .121 3 .984 363. 98 .215 0.005 0. .034 0 .075 4 .026 377. 98 .275 0.004 0. .033 0 .056 4. .060 390. 98 .327 0.004 0. .033 0 .052 4 .091 NOTE: t - Reaction time evenly divided into 30 intervals. X - Carbon conversion resulting from UBC subroutine DSPLFT. dX/dt - Rate calculated using UBC subroutine DSPLN. *dX/dt - Rate calculated using the MVM(xlOO). TY « [(dX/dt)/(1-X)]**2 TX - -Ln(l-X) T O T A L C O N V E R T E D (g ) : C - 76.640 H - 17.898 O -147.499 Appendix F. Experimental Conditions and Results 172 Table F.7: R U N # 43 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results. NO . t (min) H2 CO . CH4 (mole %) C02 1 0. 0.196 0.034 0.000 0.062 2 8. 18.914 8.038 0.120 4.498 3 23. 17.444 9.844 0.141 3.954 4 35. 16.500 9.400 0.143 3.653 5 47. 15.800 9.000 0.146 3.485 6 62. 14.558 7.717 0.131 3.409 7 76. 12.691 6.718 0.127 3.295 8 91. 12.613 5.763 0.115 3.486 9 121. 11.212 3.851 0.112 3.790 10 136. 9.317 2.749 0.088 3.422 11 159. 6.424 1.607 0.080 2.059 12 179. 2.947 1.034 0.032 0.731 13 199. 1.407 0.630 0.015 0.379 14 229. 0.981 0.399 0.010 0.198 15 259. 0.497 0.182 0.000 0.000 16 289. 0.259 0.057 0.000 0.000 17 300. 0.223 0.037 0.000 0.000 t C CONVERTED H 0 X (min) (mole) (mole) (mole) (mole%) 0. 0.000 0.000 0.000 0. .000 8. 0.230 0.699 0.310 3. .565 23. 1.132 3.200 1.490 17. .520 35. 1.855 5.042 2.409 28. .709 47. 2.534 6.765 3.266 39. .205 62. 3.299 8.752 4.243 51. .052 76. 3.910 10.336 5.038 60. .502 91. 4.492 11.864 5.813 69, .499 121. 5.509 14.792 7.253 85. .242 136. 5.905 15.972 7.848 91, .371 159. 6.316 17.300 8.482 97, .725 179. 6.498 17.942 8.751 100 .539 199. 6.583 18.203 8.866 101 .853 229. 6.659 18.424 8.969 103 .031 259. 6.695 18.567 9.013 103 .592 289. 6.704 18.632 9.021 103 .733 300. 6.706 18.648 9.023 103 .759 t X dX/dt *dX/dt TY TX (min) (mol%) (1/min) (1/min) (1/min) 0. 0.000 0.433 0 .000 0 .187 0 .000 10. 5.404 0.686 0. .724 0 .526 0 .056 21. 13.982 0.932 0. .918 1 .175 0 .151 31. 23.962 0.975 0. .986 1 .645 0 .274 41. 33.801 0.918 0. .986 1 .921 0 .413 52. 42.843 0.828 0. .947 2 .101 0 .559 62. 50.954 0.741 0. .887 2 .281 0 .712 72. 58.218 0.667 0. .814 2 .548 0 .873 83. 64.822 0.613 0. .731 3 .033 1 .045 93. 70.941 0.572 0. .639 3 .879 1 .236 103. 76.656 0.531 0. .540 5 .182 1 .455 114. 81.910 0.483 0. .438 7 .128 1 .710 124. 86.623 0.427 0. .338 10 .185 2 .012 134. 90.713 0.362 0. .243 15 .229 2 .377 145. 94.103 0.293 0. ,160 24 .703 2, .831 155. 96.785 0.226 0. .090 49 .354 3, .437 166. 98.788 0.163 0. ,0'35 180 .935 4. .413 176. 100.205 0.113 -0. ,006 186. 101.176 0.077 -.0. ,036 197. 101.842 0.054 -0. ,058 207. 102.337 0.042 -0. 075 217. 102.720 0.033 -0. .090 228. 103.020 0.026 -0. ,102 238. 103.257 0.020 -0. ,112 248: 103.442 0.015 -0. ,121 259. 103.575 0.010 -0. ,128-269. 103.661 0.006 -0. ,134 279. 103.712 0.004 -0. ,138-290. 103.743 0.002 -0. 142 300. 103.766 0.002 -0. ,145-NOTE: t - Reaction time evenly divided into 30 intervals. X - Carbon conversion resulting from UBC subroutine DSPLFT. dX/dt - Rate calculated using UBC subroutine DSPLN. *dX/dt - Rate calculated using the MVM (xlOO). TY - I(dX/dt)/(l-X)]**2 TX - -Ln(l-X) TOTAL CONVERTED (g): C - 80.538 H - 18.648 O -144.364 Appendix F. Experimental Conditions and Results 173 Table F.8: R U N # 44 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results. NO. t (min) H2 CO (mole CH4 %) C02 t (min) X (mol%) dx/dt (1/min) *dX/dt (1/min) TY (1/min) TX 1 0 0.294 0.077 0.002 0.000 0. 0.000 0.222 0.000 0.049 0.000 2 10 10.467 4.521 0.110 3.819 13. 3.548 0.359 0.370 0.138 0.036 3 20 13.202 5.163 0.169 4.556 26. 9.209 0.487 0.451 0.288 0.097 4 50 11.482 6.152 0.183 3.977 39. 16.043 0.546 0.485 0.423 0.175 5 88 12.848 5.334 0.179 3.944 52. 23.269 0.548 0.494 0.510 0.265 6 104 10.935 4.283 0.175 4.062 66. 30.314 0.526 0.487 0.570 0.361 7 120 8.402 3.748 0.155 3.679 79. 37.022 0.497 0.471 0.622 0.462 -.8 135 10.997 3.889 0.152 3.661 92. 43.296 0.460 0.449 0.657 0.567 9 150 9.039 3.010 0.122 3.258 105. 49.035 0.415 0.424 0.663 0.674 10 170 8.878 2.993 0.135 3.425 118. 54.212 0.379 0.398 0.684 0.781 11 190 8.055 2.775 0.121 2.945 131. 59.026 0.356 0.371 0.755 0.892 12 210 6.750 2.373 0.092 2.314 144. 63.533 0.331 0.342 0.826 1.009 13 235 4.802 1.814 0.067 1.580 157. 67.709 0.307 0.313 0.905 1.130 14 260 3.453 •1.413 0.044 1.145 170. 71.641 0.295 0.283 1.083 1.260 15 290 2.735 1.075 0.030 0.789 183. 75.432 0.281 0.252 1.305 1.404 16 320 1.260 0.460 0.011 0.334 197. 78.926 0.251 0.222 1.416 1.557 17 350 0.596 0.165 0.007 0.199 210. 81.984 0.215 0.194 1.427 1.714 18 380 0.238 0.033 0.000 0.000 223. 84.567 0.180 0.170 1.359 1.869 236. 86.720 0.150 0.149 1.268 2.019 249. 88.514 0.125 0.132 1.192 2.164 262. 90.039 0.109 0.117 1.188 2.307 275. 91.364 0.093 0.103 1.168 2.449 288. 92.479 0.077 0.091 1.039 2.587 301. 93.369 0.059 0.082 0.801 2.713 314. 94.038 0.043 0.075 0.517 2.820 t CONVERTED X 328. 94.497 0.028 0.070 0.256 2.900 c H 0 341. 94.788 0.017 0.067 0.110 2.954 (min) (mole) (mole) (mole) (mole%) 354. 94.971 0.011 0.066 0.051 2.990 367. 95.098 0.008 0.065 0.028 3.015 0 0 .000 0 .000 0. 000 0.000 380. 95.197 0.007 0.065 0.023 3.036 10 0 .163 0 .418 0. 234 2.076 20 0 .523 1 .372 0. 753 6.679 NOTE: 50 1 .734 4 .251 2. 447 22.136 t - Reaction time evenly divided into 30 88 3 .256 8 .139 4. 530 41.560 intervals. 104 3 .824 9 .707 5. 341 48.805 X - Carbon conversion resulting from UBC 120 4 .302 10 .865 6. 041 54.901 subroutine DSPLFT. 135 4 .734 11 .995 6. 671 60.422 dX/dt - Rate calculated using UBC subroutine 150 5 .132 13 .180 7. 256 65.504 DSPLN. 170 5 .596 14 .486 7. 953 71.419 *dx/dt - Rate calculated using the MVM(xlOO). 190 6 .055 15 .778 8. 638 77.280 TY - [(dX/dt)/(l-X)]*«2 210 6 .432 16 .861 9. 194 82.092 TX - -Ln(l-X) 235 6 .785 17 .883 9. 707 86.600 260 7 .034 18 .575 10. 063 89.778 290 7 .257 19 .199 10. 378 92.618 320 7 .386 19 .595 10. 558 94.271 350 7 .437 19 .758 10. 631 94.915 380 • 7 .458 19 .841 10. 664 95.189 TOTAL CONVERTED (g): C - 89.571 H - 19.841 O -170.625 Appendix F. Experimented Conditions and Results 174 Table F.9: R U N # 45 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results. NO . t H2 CO CH4 C02 (min) (mole %) 1 0. 0.194 0.057 0.019 0.000 2 10. 9.958 2.552 0.092 3.834 3 40. 10.944 3.311 0.1S9 4.208 4 71. 8.579 2.488 0.149 3.834 5 105. 9.441 2.520 0.151 3.834 6 130. 9.979 2.661 0.157 3.954 7 190. 9.099 2.414 0.137 3.564 8 220. 6.972 1.910 0.106 2.684 9 250. 5.804 1.636 0.088 2.128 10 282. 5.167 1.607 0.077 1.895 11 310. 3.836 1.281 0.053 1.332 12 345. 3.612 1.319 0.050 1.211 13 405. 2.136 0.879 0.029 0.646 14 465. 1.200 0.300 0.010 0.309 t CONVERTED X C H O (min) (mole) (mole) (mole) (mole%) 0. 0. .000 0 .000 0 .000 0. .000 10. 0. .121 0 .382 0 .190 1. .530 40. 0. .917 2 .788 1 .424 11. .607 71. 1. .712 5 .006 2 .657 21. .671 105. 2. .507 7 .286 3 .906 31, .738 130. 3. .121 9 .143 4 .865 39, .504 190. 4. .603 13 .673 7 .179 58, .272 220. 5. .185 15 .451 8 .084 65 .630 250. 5. .619 16 .790 8 .752 71, .123 282. 6. .027 18 .033 9 .372 76 .291 310. 6. .319 18 .898 9 .809 79 .992 345. 6. .614 19 .759 10 .240 83 .722 405. 7, .042 20 .972 10 .852 89 .138 465. 7, .228 21 .546 11 .112 91 .497 TOTAL CONVERTED (g) : C - 86.812 H - 21.546 O -177.785 t , X dX/dt *dX/dt TY TX (min) (mol%) (1/min) (1/min) (1/min) 0. 0.000 0.177 0.000 0.031 0 .000 16. 3.476 0.280 0.258 0.084 0 .035 32. 8.681 0.352 0.304 0.149 0 .091 48. 14.265 0.337 0.324 0.154 0 .154 64. 19.486 0.316 0.334 0.154 0 .217 80. 24.440 0.303 0.336 0.161 0 .280 96. 29.272 0.301 0.334 0.181 0 .346 112. 34.143 0.308 0.326 0.218 0 .418 128. 39.137 0.315 0.315 0.268 0 .497 144. 44.236 0.319 0.299 0.327 0 .584 160. 49.313 0.313 0.281 0.380 0 .679 176. 54.207 0.296 0.262 0.418 0 .781 192. 58.756 0.270 0.243 0.428 0 .886 208. 62.837 0.239 0.224 0.415 0 .990 224. 66.427 0.209 0.207 0.386 1 .091 241. 69.561 0.184 0.192 0.364 1 .189 257. 72.359 0.166 0.178 0.362 1 .286 273. 74.903 0.151 0.165 0.363 1 .382 289. 77.212 0.137 0.152 0.362 1 .479 305. 79.309 0.125 0.141 0.362 1 .575 321. 81.215 0.114 0.130 0.366 1 .672 337. 82.969 0.106 0.120 0.385 1 .770 353.. 84.616 0.1.00. 0.110 0.421 1 .872. 369. 86.156 0.092 0.100 0.440 1 .977 385. 87.546 0.081 0.091 0.422 2 .083 401. 88.736 0.067 0.084 0.354 2 .184 417. 89.688 0.052 0.078 0.256 2 .272 433. 90.432 0.041 0.073 0.187 2 .347 449. 91.039 0.035 0.069 0.152 2 .412 465. 91.576 0.033 0.066 0.151 2 .474 N O T E : t - Reaction time evenly divided into 30 intervals. X - Carbon conversion resulting from UBC subroutine DSPLFT. dX/dt - Rate calculated using UBC subroutine DSPLN. *dX/dt - Rate calculated using the MVM(xlOO) . TY « [(dX/dt)/(l-X)]**2 TX = -Ln(l-X) Appendix F. Experimental Conditions and Results 175 Table F.10: R U N # 47 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results. NO. t H2 CO CH4 C02 (mini (mole %) 1 0. 0 .117 0 .038 0. .010 0. .000 2 10. 8 .626 1 .487 0 .061 2. .834 3 22. 8 .741 1 .739 0. .034 3. .290 4 54. 6 .970 1 .287 0, .078 2. .974 5 74. 5 .783 1 .163 0. .080 2. .812 6 94. 6 .931 1 .408 0. .097 3. .133 7 116. 6 .994 1 .263 0. .109 3. .165 8 171. 7 .442 1 .252 0. .104 3. .057 9 210. 7 .239 1 .467 0, .107 3. .016 10 270. 5 .803 0 .935 0. .089 2. .411 11 330. 4 .009 0 .648 0. .058 1. .652 12 390. 1 .619 0 .270 0, .020 0. .665 t CONVERTED X C H 0 (min) (mole) (mole) (mole) (mole%) 0. 0.000 0.000 0.000 0.000 10. 0.079 0.316 0.128 1.407 22. 0.282 1.070 0.460 5.031 54. 0.825 2.959 1.359 14.740 74. 1.110 3.838 1.836 19.831 94. 1.411 4.737 2.337 25.209 116. 1.770 5.860 2.933 31.618 171. 2.614 8.692 4.352 46.691 210. 3.237 10.785 5.379 57.820 270. 4.091 13.612 6.786 73.084 330. 4.671 15.662 7.763 83.442 390. 5.007 16.820 8.323 89.448 TOTAL CONVERTED (g): C - 60.137 H - 16.820 0 -133.167 t X dX/dt *dX/dt TY TX (min) (mol%) (1/min) (1/min) (1/min) 0. 0.000 0.159 0 .000 0 .025 0 .000 13. 2.478 0.229 0 .222 0 .055 0 .025 27. 6.039 0.290 0 .271 0 .095 0 .062 40. 10.112 0.310 0 .298 0 .119 0 .107 54. 14.231 0.297 0 .314 0 .120 0 .154 67. 18.064 0.276 0 .324 0 .113 0 .199 81. 21.728 0.271 0 .330 0 .120 0 .245 94. 25.399 0.276 0 .331 0 .137 0 .293 108. 29.157 0.281 0 .329 0 .157 0 .345 121. . 32.923 0.278 0 .325 0 .172 0 .399 134. 36.642 0.275 0 .318 0 .189 0 .456 148. 40.344 0.275 0 .309 0 .213 0 .517 161. 44.062 0.278 0 .299 0 .247 0 .581 175. 47.832 0.283 0 .286 0 .294 0 .651 188. 51.655 0.285 0 .272 0 .348 0 .727 202. 55.480 0.283 0 .257 0 .404 0 .809 215. 59.250 0.277 0 .240 0 .462 0 .898 229. 62.912 0.267 0 .223 0 .519 0 .992 242. 66.424 0.254 0 .206 0 .574 1 .091 256. 69.743 0.239 0 .189 0 .621 1 .195 269. 72.825 0.219 0 .173 0 .652 1 .303 282. 75.635 0.199 0 .158. 0 .66S 1 .412 296. 7.8.170 0.178 0 .144 .0 .667 1 .522 309. 80.435 0.159 0 .131 0 .657 1 .631 323. 82.437 0.139 0 .119 0 .629 1 .739 336. 84.185 0.121 0 .109 0 .585 1 .844 350. 85.708 0.106 0 .100 0 .553 1 .945 363. 87.061 0.096 0 .091 0 .547 2 .045 377. 88.301 0.089 0 .084 0 .584 2 .146 390. 89.485 0.087 0 .076 0 .690 2 .252 NOTE: t - Reaction time evenly divided into 30 intervals. X - Carbon conversion resulting from UBC subroutine DSPLFT. dX/dt - Rate calculated using UBC subroutine DSPLN. *dX/dt - Rate calculated using the MVMU100) . TY = [(dX/dt)/(1-X)] **2 TX •= -Ln(l-X) Appendix F. Experimental Conditions and Results 176 Table F . l l : R U N # 49 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results. NO . t H2 CO CH4 C02 (min) (mole %) 1 0. 0.165 0.025 0.010 0.000 2 12. 6.504 1.102 0.023 1.605 3 23. 5.855 1.143 0.056 2.471 4 35. 5.981 1.408 0.083 2.808 S 51. 7.643 1.572 0.116 3.009 6 81. 8.686 2.185 0.124 2.746 7 130. 6.072 1.905 0.101 2.062 8 197. 5.038 1.847 0.087 1.734 9 257. 4.397 1.932 0.089 1.706 10 317. 3.844 1.654 0.074 1.357 11 377. 3.657 1.576 0.067 1.099 12 437. 3.212 1.464 0.046 0.956 t CONVERTED X C H O (min) (mole) (mole) (mole) (mole%) 0. 0.000 0.000 0.000 0.000 12. 0.057 0.275 0.089 0.721 23. 0.177 0.745 0.284 2.256 35. 0.341 1.245 0.555 4.352 51. 0.593 2.030 0.963 7.559 81. 1.114 3.826 1.779 14.205 130. 1.889 6.379 2.942 24.092 197. 2.754 8.943 4.208 35.126 257. 3.510 10.935 5.298 44.776 317. 4.200 12.645 6.282 53.574 377. 4.773 14.188 7.083 60.883 437. 5.291 15.615 7.791 67.490 TOTAL CONVERTED (g): C - 63.547 H - 15.615 O -124.655 t X dX/dt *dX/dt TY TX (min) (mol%) (1/min) (1/min) (1/min) 0. 0.000 0.083 0.000 0.007 0 .000 15. 1.413 0.114 0.136 0.013 0 .014 30. 3.523 0.166 0.169 0.029 0 .036 45. 6.320 0.202 0.189 0.047 0 .065 60. 9.518 0.219 0.202 0.059 0 .100 75. 12.862 0.222 0.210 0.065 0 .138 90. 16.146 0.213 0.216 0.065 0 .176 105. 19.285 0.203 0.219 0.064 0 .214 121. 22.280 0.194 0.221 0.062 0 .252 136. 25.135 0.185 0.222 0.061 0 .289 151. 27.860 0.177 0.222 0.060 0 .327 166. 30.470 0.170 0.221 0.060 0 .363 181. 32.982 0.164 0.220 0.060 0 .400 196. 35.414 0.159 0.218 0.061 0 .437 211. 37.783 0.155 0.215 0.062 0 .475 226. 40.104 0.153 0.212 0.065 0 .513 241. 42.395 0.151 0.209 0.069 0 .552 256. 44.672 0.151 0.205 0.075 0 .592 271. 46.946 0.150 0.200 0.080 0 .634 286. 49.193 0.147 0.195 0.084 0 .677 301. 51.380 0.142 0.190 0.086 0 .721 316. 53.476 0.135 0.185 0.085 0 .765 332. 55.456 0.128 0.180 0.082 0 .809 347. 57.331 0.121 0.175 0.081 0 .852 362. 59.124 0.117 0.171 0.082 0 .895 377. 60.857 0.113 0.166 0.084 0 .938 392. 62.550 0.111 0.161 0.088 0 .982 407. 64.214 0.110 0.156 0.094 1 .028 422. 65.859 0.109 0.150 0.101 1 .075 437. 67.494 0.108 0.145 0.111 1 .124 NOTE: t - Reaction time evenly divided into 30 intervals. X - Carbon conversion resulting from UBC subroutine DSPLFT. dX/dt - Rate calculated using UBC subroutine DSPLN. *dX/dt - Rate calculated using the MVM(xlOO). TY = I(dX/dt)/(l-X)]**2 TX •= -Ln(l-X) Appendix F. Experimental Conditions and Results 177 Table F.12: R U N # 51 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results. NO. t H2 CO CH4 C02 (rain) (mole %) 1 0. 0 .078 0. .000 0. 009 0. .095 2 12. 17 .967 9, .931 0. 124 3. .841 3 27. 14 .768 8, .229 0. 100 3. .976 4 42. 15 .658 7. .732 0. 095 4. .964 5 57. 12 .722 5 .385 0. 075 6. .112 6 73. 11 .737 4 .023 0. 054 3. .775 7 102. 10 .154 2. .391 0. 045 3. .728 8 122. 6 .559 1. .122 0. 026 2. .707 9 147. 2 .921 0, .250 0. 021 1. .527 10 172. 1 .488 0, .095 0. 008 0. .641 11 205. 0 .903 0. .082 0. 032 0. .422 12 235. 0 .502 0. .026 0. 005 0. .182 13 275. 0 .390 0. .021 0. 000 0. .000 t CONVERTED X C H 0 (min) (mole) (mole) (mole) (mole%) 0. 0.000 0.000 0.000 0.000 12. 0.379 0.991 0.481 7.405 27. 1.204 3.044 1.546 23.555 42. 2.008 5.034 2.625 39.273 57. 2.791 6.867 3.762 54.604 73. 3.404 8.392 4.692 66.589 102. 4.132 10.862 5.785 80.825 122. 4.498 12.080 6.387 87.982 147. 4.721 12.845 6.779 92.352 172. 4.817 13.178 6.958 94.227 205. 4.878 13.424 7.066 95.414 235. 4.914 13.562 7.130 96.136 275. 4.922 13.654 7.145 96.278 TOTAL CONVERTED (g): C - 59.110 H - 13.654 0 -114.323 t X dX/dt *dX/dt TY TX (min) (mol%) (1/min) (1/min) (1/min) 0. 0 .000 0 .609 0 .000 0 .370 0 .000 9. 6 .179 0 .738 0 .925 0 .618 0 .064 19. 14 .524 1 .003 0 .987 1 .378 0 .157 28. 24 .611 1 .094 0 .955 2 .104 0 .283 38. 34 .975 1 .084 0 .879 2 .782 0 .430 47. 45 .022 1 .024 0 .782 3 .472 0 .598 57. 54 .187 0 .897 0 .680 3 .832 0 .781 66. 61 .949 0.744 0 .585 3 .819 0 .966 76. 68 .355 0 .611 0 .501 3 .729 1 .151 85. 73 .629 0 .506 0 .429 3 .688 1 .333 95. 78 .055 0 .432 0 .366 3 .876 1 .517 104. 81 .918 0 .386 0 .308 4 .S66 1 .710 114. 85 .350 0 .334 0 .255 5 .190 1 .921 123. 88 .178 0 .259 0 .209 4 .818 2 .135 133. 90 .285 0 .188 0 .175 3 .737 2 .332 142. 91 .794 0 .133 0 .150 2 .639 2 .500 152. 92 .867 0 .095 0 .132 1 .781 2 .640 161. 93 .633 0 .068 0 .120 1 .146 2 .754 171. 94 .192 0 .051 0 .111 0 .780 2 .846 180. 94 .630 0 .042 0 .104 0 .597 2 .924 190. 94 .984 0 .033 0 .098 0 .444 2 .993 199. 95 .269 0 .027 0 .093 0 .326 3 .051 209. 95 .501 0 .022 0 .090 0 .242 3 .101 218. 95 .691 0 .018 0 .087 0 .176 3 .145 228. 95 .846 0 .015 0 .085 0 .123 3 .181 237. 95 .970 0 .012 0 .083 0 .084 3 .211 247. 96 .069 0 .009 0 .081 0 .057 3 .236 256. 96 .150 0 .008 0 .080 0 .041 3 .257 266. 96 .218 0 .007 0 .080 0 .032 3 .275 275. 96 .280 0 .006 0 .079 0 .030 3 .292 NOTE: t - Reaction time evenly divided into 30 intervals. X - Carbon conversion resulting from UBC subroutine DSPLFT. dX/dt - Rate calculated using UBC subroutine DSPLN. *dX/dt - Rate calculated using the MVM(xlOO). TY « [(dX/dt)/(1-X)]**2 TX « -Ln(l-X) Appendix F. Experimental Conditions and Results 178 Table F.13: R U N # 54 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results. NO. t H2 CO CH4 C02 (min) (mole %) 1 0. 0.067 0 .000 0 .000 0. .000 2 7. 14.893 3 .751 0 .097 2. .470 3 15. 11.129 3 .347 0 .088 3. .717 4 25. 10.603 3 .581 0 .099 3. .439 5 40. 10.700 3 .836 0 .111 3. .765 6 81. 11.421 3 .250 0 .122 3. .783 7 100. 11.222 2 .900 0 .125 4. .063 8 125. 5.465 1 .252 0 .051 2. .759 9 150. 4.299 1 .032 0 .043 1. .910 10 177. 3.200 0 .792 0 .029 1. .195 11 208. 2.043 0 .667 0 .023 0. .814 12 238. 1.207 0 .404 0 .009 0. .369 13 269. 0.827 0 .275 0 .006 0. .265 14 300. 0.509 0 .164 0 .000 0. .063 t CONVERTED X C H 0 (min) (mole) (mole) (mole) (mole%) 0. 0.000 0.000 0.000 0.000 7. 0.087 0.416 0.119 1.950 15. 0.297 1.207 0.427 6.670 25. 0.566 2.023 0.830 12.721 40. 0.984 3.257 1.441 22.101 81. 2.158 6.728 3.194 48.461 100. 2.680 8.440 3.993 60.184 125. 3.197 10.017 4.821 71.795 150. 3.477 10.786 5.287 78.089 177. 3.702 11.488 5.647 83.139 208. 3.875 12.013 5.916 87.029 238. 3.985 12.325 6.080 89.483 269. 4.046 12.519 6.169 90.852 300. 4.087 12.654 6.229 91.788 TOTAL CONVERTED (g): C - 49.089 H - 12.654 0 - 99.665 t X dX/dt *dX/dt TY TX (min) (mol%) (1/min) (1/min) (1/min) 0. 0 .000 0.282 0.000 0.079 0 .000 10. 3 .664 0.475 0.499 0.244 0 .037 21. 9 .467 0.620 0.578 0.469 0 .099 31. 16 .104 0.654 0.606 0.607 0 .176 41. 22 .914 0.660 0.607 0.732 0 .260 52. 29 .721 0.656 0.592 0.871 0 .353 62. 36 .477 0.650 0.565 1.046 0. .454 72. 43 .156 0.641 0.530 1.272 0 .565 83. 49 .730 0.629 0.488 1.566 0 .688 93. 56 .091 0.596 0.442 1.839 0 .823 103. 61 .943 0.531 0.395 1.950 0 .966 114. 67 .040 0.452 0.352 1.882 1 .110 124. 71 .260 0.362 0.315 1.587 1 .247 134. 74 .549 0.279 0.286 1.198 1 .368 145. 77 .128 0.225 0.263 0.969 1 .475 155. 79 .305 0.198 0.243 0.919 1 .575 166. 81 .243 0.176 0.225 0.884 1 .674 176. 82 .959 0.156 0.208 0.833 1 .770 186. 84 .465 0.136 0.193 0.767 1 .862 197. 85 .781 0.119 0.179 0.696 1 .951 207. 86 .926 0.103 0.167 0.621 2 .035 217. 87 .917 0.089 0.157 0.539 2 .113 228. 88 .762 0.075 0.148 0.441 2 .186 238. 89 .462 0.061 0.141 0.333 2 .250 248. 90 .026 0.049 0.135 0.239 2 .305 259. 90 .481 0.040 0.130 0.175 2 .352 269. 90 .861 0.034 0.127 0.140 2 .393 279. 91 .196 0.031 0.123 0.122 2 .430 290. 91 .503 0.029 0.120 0.115 2 .465 300. 91 .795 0.028 0.118 0.117 2 .500 NOTE: t - Reaction time evenly divided into 30 intervals. X - Carbon conversion resulting from UBC subroutine DSPLFT. dX/dt - Rate calculated using UBC subroutine DSPLN. *dX/dt - Rate calculated using the MVM(xlOO). TY * t(dX/dt)/(l-X)]**2 TX •= -Ln(l-X) Appendix F. Experimental Conditions and Results 179 Table F.14: R U N # 55 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results. NO. t H2 CO CH4 C02 (rain) (mole %) 1, 0. 0 .090 0. .000 0. .000 0.000 2 10. 17, .894 16. .538 0. .092 1.240 3 23. 13. .895 13. .449 0. .069 1.205 4 36. 14. .454 11. .811 0. .085 2.854 5 48. 14. .894 8. .537 0. .085 3.716 6 63. 9. .807 4. .733 0. .053 3.884 7 79. 7. .721 1. .249 0. .040 2.847 8 99. 2. .434 0. .187 0. .015 1.049 9 119. 0. .952 0. .055 0. .000 0.347 10 150. 0. .268 0. .031 0. .000 1.123 t CONVERTED X C H O (min) (mole) (mole) (mole) (mole%) 0. 0.000 0.000 0.000 0.000 10. 0.430 0.872 0.457 9.571 23. 1.354 2.692 1.434 30.165 36. 2.187 4.282 2.377 48.739 48. 2.899 5.852 3.258 64.601 63. 3.538 7.389 4.127 78.825 79. 3.908 8.393 4.695 87.073 99. 4.072 9.108 4.987 90.736 119. 4.117 9.271 5.068 91.723 150. 4.183 9.458 5.193 93.205 TOTAL CONVERTED (g): C - 50.238 H - 9.458 O - 83.088 t X dX/dt *dX/dt TY TX (min) (mol%) (1/min) (1/min) (1/min) 0. 0.000 0.860 0.000 0.739 0.000 5. 4.612 0.955 1.260 1.003 0.047 10. 10.211 1.241 1.421 1.910 0.108 16. 17.404 1.512 1.453 3.349 0.191 21. 25.550 1.609 1.412 4.671 0.295 26. 33.775 1.559 1.331 5.541 0.412 31. 41.656 1.488 1.230 6.502 0.539 36. 49.158 1.412 1.116 7.716 0.676 41. 56.236 1.320 0.995 9.096 0.826 47. 62.764 1.200 0.873 10.380 0.988 52. 68.606 1.058 0.756 11.352 1.159 57. 73.699 0.911 0.650 11.993 1.336 62. 78.021 0.760 0.555 11.952 1.515 67. 81.562 0.612 0.476 11.006 1.691 72. 84.377 0.480 0.411 9.422 1.856 78. 86.551 0.364 0.360 7.316 2.006 83. 88.170 0.266 0.322 5.046 2.135 88. 89.337 0.189 0.295 3.147 2.238 93. 90.164 0.134 0.276 1.862 2.319 98. 90.763 0.101 0.263 1.194 2.382 103. 91.235 0.082 0.253 0.885 2.434 109. 91.621 0.067 0.245 0.646 2.479 114. 91.937 0.055 0.239 0.473 2.518 119. 92.200 0.047 0.234 0.359 2.551 124. 92.425 0.040 0.229 0.282 2.580 129. 92.619 0.035 0.226 0.224 2.606 134. 92.788 0.031 0.223 0.182 2.629 140. 92.940 0.028 0.220 0.156 2.651 145. 93.079 0.026 0.218 0.142 2.671 150. 93.211 0.025 0.216 0.141 2.690 NOTE: t - Reaction time evenly divided into 30 intervals. X - Carbon conversion resulting from UBC subroutine DSPLFT. dX/dt - Rate calculated using UBC subroutine DSPLN. *dX/dt - Rate calculated using the MVM(xlOO). TY - KdX/dt)/(1-X)]**2 TX •= -Ln(l-X) Appendix F. Experimental Conditions and Results 180 Table F.15: R U N # 57 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results. NO . t H2 CO CH4 C02 (min) (mole %) 1 0. 0.353 0.121 0.000 0.000 2 10. 5.440 0.888 0.023 1.599 3 31. 4.835 0.993 0.048 2.134 4 51. 5.075 0.985 0.057 2.000 5 81. 5.134 1.275 0.063 2.390 6 126. 5.553 1.528 0.077 2.114 7 162. 4.877 1.478 0.075 1.919 8 207. 4.902 1.533 0.089 1.808 9 267. 3.873 1.352 0.073 1.421 10 327. 3.553 1.322 0.065 1.177 11 433. 3.364 1.407 0.065 1.043 12 493. 2.808 1.289 0.052 0.873 t CONVERTED X C H 0 (min) (mole) (mole) (mole) (mole%) 0. 0.000 0.000 0.000 0.000 10. 0.044 0.195 0.070 0.526 31. 0.244 0.927 0.399 2.919 51. 0.452 1.605 0.742 5.415 81. 0.794 2.661 1.300 9.511 126. 1.373 4.410 2.212 16.439 162. 1.809 5.710 2.883 21.662 207. 2.331 7.232 3.675 27.915 267. 2.964 9.079 4.618 35.506 327. 3.490 10.566 5.382 41.800 433. 4.374 13.093 6.627 52.395 493. 4.844 14.366 7.276 58.020 TOTAL CONVERTED (g): C - 58.177 H - 14.366 O -116.409 t X dX/dt *dX/dt TY TX (min) (mol%) (1/min) (1/min) (1/min) 0. 0.000 0 .090 0.000 0.008 0 .000 17. 1.594 0 .100 0.094 0.010 0 .016 34. 3.413 0 .114 0.112 0.014 0 .035 51. 5.465 0 .127 0.123 0.018 0 .056 68. 7.720 0 .138 0.131 0.022 0 .080 85. 10.131 0 .146 0.136 0.026 0 .107 102. 12.650 0 .150 0.139 0.030 0 .135 119. 15.219 0 .151 0.141 0.032 0 .165 136. 17.783 0 .150 0.142 0.033 0 .196 153. 20.307 0 .147 0.143 0.034 0 .227 170. 22.776 0 .143 0.142 0.034 0 .258 187. 25.178 0 .139 0.142 0.035 0 .290 204. 27.507 0 .135 0.141 0.035 0 .322 221. 29.756 0 .130 0.140 0.034 0 .353 238. 31.921 0 .125 0.138 0.034 0 .384 255. 33.996 0 .119 0.137 0.033 0 .415 272. 35.978 0 .114 0.135 0.032 0 .446 289. 37.871 0 .109 0.134 0.031 0 .476 306. 39.693 0 .106 0.132 0.031 0 .506 323. 41.466 0 .103 0.130 0.031 0 .536 340. 43.210 0 .102 0.128 0.032 0 .566 357. 44.932 0 .101 0.126 0.033 0 .597 374. 46.632 0 .099 0.124 0.035 0 .628 391. 48.312 0 .098 0.121 0.036 0 .660 408. 49.972 0 .097 0.119 0.038 0 .693 425. 51.613 0 .096 0.116 0.039 0 .726 442. 53.237 0 .095 0.114 0.041 0 .760 459. 54.846 0 .094 0.111 0.044 0 .795 476. 56.445 0 .094 0.108 0.046 0 .831 493. 58.039 0 .094 0.105 0.050 0 .868 NOTE: t - Reaction time evenly divided into 30 intervals. X - Carbon conversion resulting from UBC subroutine DSPLFT. dX/dt - Rate calculated using UBC subroutine DSPLN. *dX/dt - Rate calculated using the MVM(xlOO) . TY « ((dX/dt)/(l-X)]**2 TX - -Ln(l-X) Appendix F. Experimental Conditions and Results 181 Table F.16: R U N # 58 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results. NO. t H2 CO CH4 C02 (min) (mole %) 1 0. 0. .177 0. .087 0.025 0 .000 2 7. 14. .987 7, .429 0.120 3 .385 3 17. 10. .766 7. .463 0.105 2 .738 4 28. 10. .897 7. .648 0.112 3 .047 5 40. 12. .022 6. .723 0.102 2 .585 6 59. 12. .035 5. .905 0.099 3 .023 7 79. 10. .999 3, .944 0.101 3 .806 8 99. 7. .609 2. .047 0.073 2 .586 9 119. 4. .035 1. .273 0.039 1 .356 10 146. 1. .386 0. .511 0.012 0 .434 11 171. 0. .388 0. .118 0.000 0 .000 12 210. 0. .197 0. .036 0.000 0 .000 13 223. 0. .168 0. .033 0.000 0 .000 t CONVERTED X C H 0 (min) (mole) (mole) (mole) (mole%) 0. 0.000 0.000 0.000 0.000 7. 0.161 0.449 0.208 3.698 17. 0.590 1.513 0.757 13.578 28. 1.046 2.468 1.334 24.073 40. 1.518 3.580 1.930 34.920 59. 2.200 5.419 2.807 50.606 79. 2.867 7.257 3.738 65.958 99. 3.333 8.675 4.442 76.682 119. 3.577 9.474 4.812 82.281 146. 3.730 9.922 5.038 85.811 171. 3.767 10.050 5.088 86.661 210. 3.769 10.103 5.086 86.693 223. 3.770 10.118 5.088 86.732 TOTAL CONVERTED (g): C - 45.280 H - 10.118 0 - 81.401 t X dX/dt *dX/dt TY TX (min) (mol%) (1/min) (1/min) (1/min) 0. 0 .000 0.513 0.000 0 .263 0, .000 8. 4 .466 0.713 0.829 0 .558 0, .046 15. 11 .002 0.948 0.870 1 .136 0. .117 23. 18 .559 1.000 0.854 1 .507 0. .205 31. 26 .160 0.967 0.813 1 .714 0, .303 38. 33 .391 0.913 0.762 1 .880 0. .406 46. 40 .210 0.862 0.706 2 .078 0. .514 54. 46 .681 0.823 0.646 2 .385 D. .629 62. 52 .905 0.796 0.584 2 .857 0. 753 69. 58 .873 0.752 0.521 3 .340 0 .888 77. 64 .399 0.681 0.459 3 .664 1, .033 85. 69 .297 0.591 0.402 3 .703 1. .181 92. 73 .472 0.494 0.353 3 .473 1. .327 100. 76 .886 0.393 0.312 2 .889 1. .465 108. 79 .544 0.302 0.279 2 .174 1 .587 115. 81 .576 0.230 0.255 1 .561 1 .691 123. 83 .132 0.177 0.236 1 .101 1 .780 131. 84 .320 0.133 0.221 0 .721 1 .853 138. 85 .201 0.097 0.211 0 .433 1 .911 146. 85 .839 0.070 0.204 0 .243 1 .955 154. 86 .291 0.049 0.199 0 .126 1 .987 161. 86 .602 0.033 0.196 0 .061 2 .010 169. 86 .812 0.023 0.195 0 .029 2 .026 177. 86 .959 0.016 0.194 0 .015 2 .037 185. 87 .062 0.011 0.194 0 .007 2 .045 192. 87 .129 0.007 0.194 0 .003 2 .050 200. 87 .168 0.004 0.195 0 .001 2 .053 208. 87 .188 0.002 0.196 0 .000 2 .055 215. 87 .196 0.001 0.197 0 .000 2 .055 223. 87 .200 0.000 0.198 0 .000 2 .056 NOTE: t - Reaction time evenly divided into 30 intervals. X - Carbon conversion resulting from UBC subroutine DSPLFT. dX/dt - Rate calculated using UBC subroutine DSPLN. *dX/dt - Rate calculated using the MVM(xlOO). TY - [(dX/dt)/(1-X)]**2 TX « -Ln(l-X) Appendix F. Experimental Conditions and Results 182 Table F.17: R U N # 59 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results. NO. t H2 CO CH4 C02 (min) (mole %) 1 0. 0 .599 0 .376 0 .000 0 .000 2 i o . 6 .187 1 .080 0 .034 1 .949 3 25. 5 .089 0 .981 0 .039 2 .075 4 40. 5 .730 1 .446 0 .070 2 .804 5 55. 7 .592 1 .581 0 .089 2 .871 6 81. 6 .498 1 .513 0 .090 2 .524 7 140. 6 .269 1 .762 0 .091 2 .260 8 173. 5 .262 1 .913 0 .106 2 .394 9 211. 6 .512 2 .253 0 .110 2 .352 10 240. 5 .558 1 .819 0 .095 1 .872 11 281. 5 .464 1 .968 0 .096 1 .821 12 327. 5 .335 2 .160 0 .107 1 .850 13 387. 2 .730 1 .081 0 .049 0 .819 14 432. 3 .739 1 .702 0 .075 1 .187 15 484. 3 .335 1 .559 0 .064 1 .050 t CONVERTED X C H- O (min) (mole) (mole) (mole) (mole%) 0. 0.000 0.000 0.000 0.000 10. 0.058 0.230 0.090 0.574 25. 0.213 0.806 0.345 2.120 40. 0.401 1.365 0.654 3.994 55. 0.630 2.072 1.026 6.279 81. 1.017 3.349 1.646 10.135 140. 1.835 6.031 2.917 18.288 173. 2.311 7.348 3.642 23.026 211. 2.920 8.945 4.553 29.096 240. 3.344 10.202 5.177 33.320 281. 3.854 11.733 5.921 38.403 327. 4.502 13.538 6.849 44.863 387. 5.093 15.165 7.685 50.748 432. 5.432 16.100 8.153 54.125 484. 5.977 17.503 8.902 59.560 t X dX/dt *dX/dt TY TX (min) (mol%) (1/min) (1/min) (1/min) 0. 0. .000 0.093 0 .000 . 0.009 0. 000 17. 1, .593 0.099 0 .096 0.010 0. 016 33. 3 .375 0.115 0 .115 ' 0.014 0. 034 50. 5. .404 0.128 0 .127 0.018 0. 056 67. 7. .613 0.136 0 .135 0.022 0. 079 83. 9. .939 0.142 0 .141 0.025 0. 105 100. 12. .333 0.145 0 .145 0.027 0. 132 117. 14. .779 0.148 0 .147 0.030 0. 160 134. 17. .262 0.150 0 .148 0.033 0. 189 150. 19, .770 0.151 0 .149 0.035 0. 220 167. 22, .292 0.151 0 .149 0.038 0. 252 184. 24, .818 0.151 0 .148 0.040 0. 285 200. 27. .330 0.150 0 .147 0.042 0. 319 217. 29. .804 0.147 0 .145 0.044 0. 354 234. 32. .220 0.143 0 .143 0.044 0. 389 250. 34. .569 0.139 0 .141 0.045 0. 424 267. 36. .850 0.135 0 .139 0.046 0. 460 284. 39. .069 0.131 0 .136 0.046 0. 495 300. 41. .223 0.127 0 .134 0.047 0. 531 317. 43. .298 0.122 0 .131 0.046 0. 567 334. 45. .274 0.115 0 .128 0.044 0. 603 350. 47. .144 0.109 0 .126 0.043 0. 638 367. 48. .920 0.104 0 .123 0.041 0. 672 384. 50. .613 0.099 0 .121 0.040 0. 705 401. 52. .235 0.095 0 .118 0.040 0. 739 417. 53. .799 0.092 0 .116 0.040 0. 772 434. 55. .316 0.090 0 .113 0.040 0. .806 451. 56. .798 0.088 0 .111 0.041 0. 839 467. 58. .256 0.087 0 .108 0.043 0. 874 484. 59. .702 0.087 0 .105 0.046 0. 909 NOTE: t - Reaction time evenly divided into 30 intervals. X - Carbon conversion resulting from UBC subroutine DSPLFT. dX/dt - Rate calculated using UBC subroutine DSPLN. *dX/dt - Rate calculated using the MVM(xlOO). TY » [(dX/dt)/(l-X>]**2 TX - -Ln(l-X) TOTAL CONVERTED (g): C - 71.789 H - 17.503 O -142.434 Appendix F. Experimental Conditions and Results 18a Table F.18: R U N # 60 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results. NO. t H2 CO CH4 C02 (min) (mole %) 1 0. 0 .172 0 .067 0 .000 0 .000 2 10. 16 .882 8 .781 0 .123 3 .951 3 20. 17 .517 10 .188 0 .155 3 .847 4 36. 16 .846 10 .413 0 .1S9 3 .574 5 53. 14 .418 9 .151 0 .150 3 .325 6 73. 14 .185 6 .980 0 .140 3 .724 7 93. 11 .965 5 .815 0 .134 3 .817 8 114. 9 .877 3 .231 0 .091 3 .137 9 139. 5 .805 2 .259 0 .068 1 .893 10 165. 2 .792 1 .316 0 .032 0 .671 11 190. 1 .532 0 .742 0 .014 0 .345 12 220. 0 .521 0 .203 0 .000 0 .167 13 250. 0 .212 0 .039 0 .000 0 .000 14 270. 0 .150 0 .000 0 .000 0 .000 t C CONVERTED H 0 X (min) (mole) (mole) (mole) (mole%) 0. 0 .000 0.000 0. .000 0. .000 10. 0 .283 0.756 0. .366 4. .729 20. 0 .884 2.309 1. .135 14. .792 36. 1 .918 4.876 2. .427 32. .100 53. 2 .911 7.218 3. .660 48. .720 73. 3 .878 9.630 4. .905 64 .910 93. 4 .716 11.805 6. .040 78. .924 114. 5 .372 13.589 6. .969 89 .903 139. 5 .833 15.026 7. .649 97 .618 165. 6 .101 15.755 8. .020 102 .110 190. 6 .219 16.095 8, .172 104 .076 220. 6 .287 16.283 8, .264 105 .217 250. 6 .302 16.342 8 .286 105 .477 270. 6 .303 16.364 8 .286 105 .488 TOTAL CONVERTED (g): C - 75.698 H - 16.364 O -132.579 t X dX/dt «dX/dt TY TX (min) (mol%) (1/min) (1/min) (1/min) 0. 0.000 0.476 0. .000 0 .226 0. .000 9. 5.057 0.678 0. .712 0 .510 0. .052 19. 13.049 0.997 0. .978 1 .313 0. .140 28. 22.913 1.098 1. .100 2 .030 0. .260 37. 33.079 1.064 1. .129 2 .527 0. .402 47. 42.567 0.973 1. .104 2 .872 0. .555 56. 51.182 0.877 1. .044 3 .229 0. .717 65. 58.965 0.799 0. .961 3 .792 0. .891 74. 66.141 0.746 0. .857 4 .859 1. .083 84. 72.847 0.691 0. .736 6 .479 1. .304 93. 78.955 0.618 0. .607 8 .620 1. .559 102. 84.316 0.533 0. .478 11 .540 1. .853 112. 88.858 0.442 0. .358 15 .719 2. .194 121. 92.540 0.3S2 0. .251 22 .248 2. .596 130. 95.466 0.280 0. .159 38 .081 3. .094 140. 97.808 0.226 0. .080 106 .490 3. .820 149. 99.709 0.183 0. .0113948 .541 5. .840 158. 101.223 0.143 168. 102.385 0.107 177. 103.245 0.079 186. 103.883 0.060 196. 104.381 0.048 205. 104.776 0.037 214. 105.073 0.027 223.' 105.276 0.017 233. 105.397 0.009 242. 105.459 0.004 251. 105.484 0.001 261. 105.491 0.000 270. 105.490 -0.000 NOTE: . t - Reaction time evenly divided into 30 intervals. X - Carbon conversion resulting from UBC subroutine DSPLFT. dX/dt - Rate calculated using UBC subroutine DSPLN. *dx/dt - Rate calculated using the MVM(xlOO). TY •= [<dX/dt)/(l-X)]**2 TX - -Ln(l-X) Appendix F. Experimental Conditions and Results 184 Table F.19: RUN# 62 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results. NO . t K2 CO CH4 C02 (min) (mole %) 1 0. 0.151 0.031 0.006 0.000 2 7. 13.322 4.610 0.084 4.239 3 18. 13.488 6.959 0.119 4.369 4 32. 14.235 7.047 0.134 4.208 5 49. 14.017 6.276 0.134 4.405 6 68. 12.528 6.307 0.141 4.223 7 93. 12.013 4.478 0.121 4.341 8 115. 11.642 3.610 0.115 4.205 9 139. 8.203 2.613 0.096 3.746 10 169. 5.500 1.800 0.060 2.327 11 199. 3.491 1.242 0.049 1.325 12 229. 2.149 0.998 0.028 0.594 13 259. 1.388 0.716 0.017 0.327 t CONVERTED X C H O (min) (mole) (mole) (mole) (mole%) 0. 0 .000 0. .000 0, .000 0. .000 7. 0 .124 0. .376 0. .181 1. .904 18. 0 .575 1. .580 0. .818 8. .843 32. 1 .237 3. .214 1. .717 19. .017 49. 2 .012 5. .242 2. .784 30. .923 68. 2 .838 7. .326 3. .932 43. .632 93. 3. .811 9. .761 5. .311 58. .582 115. 4 .523 11. .836 6. .377 69. .527 139. 5. .170 13. .669 7, .374 79. .476 169. 5. .726 15. .095 8. .242 88. .017 199. 6 .059 16. .013 8. .749 93. .150 229. 6. .261 16. .562 9. .038 96. .245 259. 6, .385 16. .899 9. .199 98. .157 TOTAL CONVERTED (g) : C - 76.685 H - 16.899 O -147.183 t X dX/dt *dX/dt TY TX (min) (mol%) (1/min) (1/min) (1/min) 0. 0 .000 0.284 0.000 0.081 0 .000 9. 3 .159 0.482 0.479 0.248 0 .032 18. 8 .491 0.681 0.616 0.554 0 .089 27. 14 .914 0.743 0.686 0.763 0 .162 36. 21 .524 0.728 0.719 0.861 0 .242 45. 27 .912 0.703 0.729 0.951 0 .327 54. 34 .094 0.681 0.723 1.069 0 .417 63. 40 .075 0.658 0.704 1.204 0 .512 71. 45 .830 0.631 0.675 1.355 0 .613 80. 51 .324 0.599 0.639 1.514 0 .720 89. 56 .513 0.562 0.599 1.672 0 .833 98. 61 .355 0.522 0.555 1.827 0 .951 107. 65 .857 0.487 0.510 2.031 1 .075 116. 70 .061 0.456 0.463 2.316 1 .206 125. 73 .987 0.422 0.416 2.637 1 .347 134. 77 .587 0.383 0.369 2.914 1 .496 143. 80 .803 0.337 0.326 3.085 1 .650 152. 83 .617 0.294 0.285 3.215 1 .809 161. 86 .061 0.254 0.249 3.321 1 .970 170. 88 .166 0.218 0.217 3.393 2 .134 179. 89 .967 0.186 0.188 3.443 2 .299 1B8. 91 .505 0.159 0.163 3.502 2 .466 196. 92 .821 0.136 0.140 3.612 2 .634 205. 93 .954 0.118 0.120 3.800 2 .806 214. 94 .931 0.101 0.103 3.993 2 .982 223. 95 .769 0.087 0.087 4.190 3 .163 232. 96 .484 0.074 0.074 4.424 3 .348 241. 97 .100 0.065 0.062 4.971 3 .541 250. 97 .650 0.059 0.051 6.317 3 .751 259. 98 .166 0.057 0.040 9.733 3 .999 NOTE: t - Reaction time evenly divided into 30 intervals. X - Carbon conversion resulting from UBC subroutine DSPLFT. dX/dt - Rate calculated using UBC subroutine DSPLN. *dx/dt - Rate calculated using the MVM(xlOO). TY - KdX/dt)/(l-X)]**2 TX •= -Ln(l-X) Appendix F. Experimental Conditions and Results 185 Table F.20: R U N # 64 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results. NO. t H2 CO CH4 C02 (min) (mole %) 1 0. 0. .169 0. .048 0. .027 0. .000 2 10. 14. .934 7, .530 0 .082 3. .705 3 22. 12, .673 7, .208 0. .078 3. .691 4 34. 13. .485 6 .»35 0. .082 3. .748 5 52. 12. .626 5. .804 0, .073 4. .171 6 70. 12. .536 3. .969 0. .062 4. .106 7 88. 10. .190 3. .182 0. .057 4. .047 8 108. 9. .479 2. .221 0. .049 3. .722 9 130. 6. .654 1. .340 0. .039 3. .414 10 162. 6. .639 0. .933 0. .030 2. .835 11 187. 6. .306 0. • 8S6 0. .029 2. .802 12 213. 3. .596 0. .396 0. .017 1. .896 13 240. 3. .724 0. .268 0. .016 1. .727 14 265. 20. .037 0. .101 0, .010 1. .075 15 291. 1. .315 0. .056 0, .008 0. .711 t CONVERTED X C H O (min) (mole) (mole) (mole) (mole%) 0. 0.000 0.000 0.000 0.000 10. 0.237 0.636 0.312 4.122 22. 0.780 1.958 1.032 13.580 34. 1.307 3.239 1.735 22.744 52. 2.069 5.169 2.777 35.994 70. 2.711 6.973 3.710 47.174 88. 3.234 8.550 4.508 S6.281 108. 3.725 10.005 5.282 64.824 130. 4.145 11.292 5.977 72.119 162. 4.604 12.693 6.771 80.109 187. 4.930 13.837 7.339 85.777 213. 5.192 14.768 7.805 90.348 240. 5.376 15.114 8.142 93.542 265. 5.519 17.401 8.411 96.037 291. 5.609 20.695 8.583 97.602 t X dX/dt *dX/dt TY TX (min) (mol%) (1/min) (1/min) (1/min) 0. 0. 000 0.390 0 .000 0.152 0 .000 10. 4. .509 0.569 0 .607 0.355 0 .046 20. 11. .541 0.786 0 .679 0.790 0 .123 30. 19. ,558 0.798 0 .689 0.985 0 .218 40. 27. ,385 0.757 0 .672 1.086 0 .320 50. 34. ,690 0.697 0 .642 1.138 0 .426 60. 41. 330 0.627 0 .606 1.142 0 .533 70. 47. 282 0.560 0 .568 1.127 0 .640 80. 52. 592 0.501 0 .530 1.118 0 .746 90. 57. 390 0.457 0 .491 1.150 0 .853 100. 61. 764 0.414 0 .454 1.174 0 .961 110. 65. 692 0.368 0 .418 1.153 1 .070 120. 69. 167 0.325 0 .384 1.112 1 .177 130. 72. 235 0.287 0 .354 1.071 1 .281 140. 74. 962 0.258 0 .326 1.063 1 .385 151. 77. 453 0.240 0 .299 1.134 1 .490 161. 79. 818 0.233 0 .272 1.335 1 .600 171. 82. 149 0.230 0 .245 1.661 1 .723 181. 84. 405 0.218 0 .217 1.956 1 .858 191. 86. 496 0.198 0 .191 2.141 2 .002 201. 88. 363 0.174 0 .167 2.244 2 .151 211. 89. 991 0.150 0 .145 2.242 2 .302 221. 91. ,375 0.127 0 .127 2.174 2 .450 231. 92. 571 0.113 0 .110 2.305 2 .600 241. 93. 667 0.107 0 .095 2.850 2 .759 251. 94. 714 0.101 0 .080 3.617 2 .940 261. 95. 661 0.087 0 .067 4.023 3 .137 271. 96. 442 0.069 0 .055 3.759 3 .336 281. 97. 069 0.057 0 .046 3.839 3 .530 291. 97. 620 0.054 0 .038 5.065 3 .738 NOTE: t - Reaction time evenly divided into 30 intervals. X - Carbon conversion resulting from UBC subroutine DSPLFT. dX/dt - Rate calculated using UBC subroutine DSPLN. *dX/dt - Rate calculated using the MVM(xlOO). TY - [(dX/dt)/(1-X)]*«2 TX - -Ln(l-X) TOTAL CONVERTED (g): C - 67.366 H - 20.695 O -137.324 Appendix F. Experimental Conditions and Results 186 Table F.21: R U N # 65 (a) Composition of Products Gas, (b) Converted C, H, 0 and C Conversion during Gasification, (c) Rate, Feasibility Check and The Model Testing Results. NO. t H2 CO CH4 C02 (min) (mole %) 1 0. 0 .212 0. .041 0 .000 0.000 2 12. 16 .673 13 .667 0 .093 1.724 3 22. 17 .322 14 .169 0 .101 2.292 4 47. 15 .174 11 .919 0 .083 2.131 5 59. 15 .700 11 .536 0 .087 2.361 6 80. 12 .708 5 .946 0 .078 3.570 7 97. 8 .853 2 .949 0 .048 2.946 8 113. 5 .148 1 .245 0 .037 2.247 9 158. 6 .081 0 .226 0 .050 2.776 10 182. 2 .100 0 .040 0 .008 0.777 11 202. 1 .176 0 .007 0 .000 0.150 t c CONVERTED H 0 X (min) (mole) (mole) (mole) ( ole%) 0. 0.000 0.000 0.000 0 .000 12. 0.426 0.933 0.470 6 .803 22. 1.168 2.527 1.302 18 .672 47. 2.809 6.007 3.175 44 .891 S9. 3.558 7.668 4.036 56 .867 80. 4.638 10.292 5.374 74 .118 97. 5.136 11.715 6.087 82 .085 113. 5.396 12.498 6.488 86 .244 158. 5.867 14.145 7.351 93 .767 182. 6.030 14.844 7.661 96 .375 202. 6.047 14.992 7.694 96 .641 TOTAL CONVERTED (g) : C - 72.623 H - 14.992 0 -123.105 t X dX/dt *dX/dt TY . TX (min) (mol%) (1/min) (1/min) (1/min) 0. 0 .000 0 .552 0. .000 0 .305 0. 000 7. 4 .070 0 .649 0. .769 0 .458 0. ,042 14. 9 .484 0 .924 0. .940 1 .043 0. ,100 21. 16 .614 1 .086 1. .008 1 .696 0. 182 28. 24 .235 1 .097 1. .020 2 .098 0. 278 35. 31 .862 1 .090 0. .997 2 .558 0. ,384 42. 39 .377 1 .065 0. .950 3 .089 .0. ,501 49. 46 .666 1 .025 0. .885 3 .692 0. ,629 56. 53. .632 0 .974 0. .809 4 .413 0. ,769 63. 60 .215 0 .913 0. .725 5 .264 0. 922 70. 66 .281 0 .824 0. .639 5 .973 1. ,087 77. 71 .626 0 .706 0. .558 6 .183 1. .260 84. 76 .049 0 .564 0. .486 5 .549 1. 429 91. 79 .533 0 .440 0. .428 4 .625 1. .586 98. 82. .235 0 .340 0. .382 3 .655 1. ,728 104. 84. .329 0 .266 0. .346 2 .891 1. 853 111. 86. .017 0 .223 0. ,316 2 .551 1. .967 118. . 87. .495 0 .202 0. .289 2 .609 2. 079 125. 88, .837 0 .184 0. .264 2 .709 2. .193 132. 90. .060 0 .168 0. .240 2 .851 2. .309 139. 91. .181 0 .154 0. .217 3 .065 2. .428 146. 92.216 0 .143 0. .195 3 .390 2. ,553 153. 93. .183 0 .135 0. .174 3 .902 2. ,686 160. 94. .097 0 .128 0. .153 4 .692 2. ,830 167. 94. .948 0 .115 0. .133 5 .186 2. ,985 174'. 95. .680 0 .094 0. .115 4 .701 3. ,142 181. 96, .233 0 .064 0. .102 2 .863 3. .279 188. 96. .564 0 .033 0. .094 0 .931 3. .371 195. 96, .724 0 .015 0. .091 0 .201 3. .418 202. 96. .797 0 .009 0. .090 0 .071 3. .441 NOTE: t - Reaction time evenly divided into 30 intervals. X - Carbon conversion resulting from UBC subroutine DSPLFT. dX/dt - Rate calculated using UBC subroutine DSPLN. *dX/dt - Rate calculated using the MVM(xlOO). TY « [(dX/dt)/(1-X)]**2 TX •= -Ln(l-X) Appendix F. Experimental Conditions and Results 187 Table F.22: Carbon Conversion Predicted by The MVM for Each Run Run# 31 Run# 32 Run# 33 Run# 36 Run# 37 t X t X t X t X t X 5 1.347 5 1.193 6 4.017 10 4.238 10 3.474 15 7.687 16 5.988 11 8.741 20 11.943 25 11.766 30 21.371 25 10.930 20 18.280 35 26.181 45 24.545 45 37.603 40 20.094 35 34.525 50 41.049 65 37.358 60 52.792 55 29.617 50 49.294 70 59.000 85 49,198 75 65.914 70 38.933 65 61.757 90 73.224 105 59.604 90 76.421 85 47.704 80 71.786 110 83.471 125 68.429 105 84.328 100 55.732 96 80.028 130 90.307 150 77.297 120 89.968 115 62.920 110 85.470 155 95.346 180 85.143 130 92.696 130 69.241 126 90.064 213 90.975 140 94.762 145 74.714 140 92.967 240 94.132 150 96.301 160 79.388 155 95.205 270 96.442 160 97.425 176 83.571 175 97.176 301 97.926 190 86.622 195 98.370 330 98.772 205 89.340 360 99.300 225 92.209 390 99.608 245 94.371 265 95.978 295 97.618 325 98.620 Appendix F. Experimental Conditions and Results 188 Run# 43 Run# 44 ' Run# 45 Run# 47 Run# 39 t X t X t X t X t X 8 3.593 10 2.500 10 1.727 10 1.520 12 0.942 23 16.029 20 6.343 40 10.258 22 4.320 23 2.268 35 27.765 50 20.577 71 20.589 54 13.713 35 3.980 47 39.540 88 39.371 105 32.028 74 20.162 51 6.554 62 53.151 104 46.704 130 40.044 94 26.691 81 11.943 76 64.118 120 53.506 190 56.980 116 33.755 130 21.500 91 73.766 135 59.350 220 64.058 171 50.017 197 34.695 121 86.999 150 64.662 250 70.211 210 59.902 257 45.761 136 91.156 170 70.919 282 75.812 270 72.216 317 55.686 159 95.295 190 76.277 310 79.969 330 81.303 377 64.310 210 80.805 345 84.297 390 87.737 437 71.622 235 85.427 405 89.842 260 89.058 465 93.566 290 92.238 320 94.724 350 96.409 380 97.587 Appendix F. Experimental Conditions and Results 189 Run# 51 Run# 54 Run# 55 Run# 57 Run# 58 t X t X t X t X t X 12 9.659 7 2.444 10 11.696 10 0.631 7 4.967 27 24.036 15 6.455 23 29.918 31 2.684 17 13.418 42 37.682 25 12.167 36 46.498 51 5.034 28 22.781 57 49.744 40 21.274 48 59.299 81 8.948 40 32.473 73 60.634 81 45.407 63 71.821 126 15.262 59 46.157 102 75.481 100 54.541 79 81.453 162 20.460 79 58.169 122 82.646 125 65.148 99 89.348 207 26.941 99 67.868 147 88.939 150 73.720 119 94.065 267 35.319 119 75.548 205 96.356 177 80.941 150 97.721 327 43.204 146 83.300 235 98.009 208 87.064 433 55.611 171 88.396 275 99.135 238 91.259 493 61.709 210 93.543 269 94.263 223 94.712 300 96.291 Appendix F. Experimental Conditions and Results 190 Run# 59 Run# 60 Run# 62 Run# 64 Run# 65 t X t X t X t X t X 10 0.647 10 4.818 7 2.132 10 4.879 12 8.220 25 2.099 20 13.772 18 8.084 22 12.741 22 17.901 40 3.819 36 31.356 32 17.591 34 21.104 47 42.859 55 5.708 53 50.075 49 30.090 52 33.424 59 53.461 81 9.239 73 68.464 68 43.706 70 44.770 80 68.719 140 17.852 93 81.623 93 59.467 88 54.803 97 78.005 173 22.782 114 90.362 115 70.686 108 64.311 113 84.553 211 28.408 139 95.938 139 80.079 130 72.861 158 94.819 240 32.613 169 88.228 162 82.187 182 97.254 281 38.368 199 93.339 187 87.388 202 98.421 327 44.499 239 96.377 213 91.312 387 51.906 259 98.100 240 94.178 432 56.996 265 96.026 484 62.372 291 97.356 Appendix F. Experimental Conditions and Resvdts Table F.23: A Demonstration of Experimental Reproducibility RUN* 29 T CONVERTED X C H 0 (min) (mole) (mole) (mole) (mole%) o.. 0.000 0.000 0.000 0.000 10. 0.432 1.041 0.489 6.322 20. 1.211 2.890 1.372 17.711 29. 1.887 4.384 2.137 27.589 41. 2.858 6.586 3.239 41.785 57. 4.098 9.349 4.646 59.914 74. 5.196 12.052 5.997 75.965 90. 5.787 13.316 6.738 84.604 105. 6.010 13.646 7.036 87.862 120. 6.119 14.156 7.245 89.465 135. 6.156 14.248 7.312 90.001 150. 6.176 14.266 7.351 90.293 T o t a l Converted (g) C - 74.175/ H - 14.266, 0 -- 117.613 RUN# 31 T CONVERTED X C H 0 (min) (mole) (mole) (mole) (mole%) 0. 0.000 0.000 0.000 0.000 5. 0.055 0.131 0.056 0.808 15. 0.598 1.398 0.658 8.743 30. 1.878 4.436 2.121 27.453 45. 3.046 7.246 3.472 44.535 60. 4.102 9.835 4.729 59.977 75. 5.000 12.137 5.845 73.101 90. 5.631 13.968 6.698 82.321 105. 5.941 15.057 7.182 86.864 120. 6.037 15.465 7.359 88.253 130. 6.065 15.595 7.413 88.672 140. 6.083 15.678 7.447 88.929 150. 6.093 15.731 7.466- 89.073 160. 6.097 15.765 7.475 89.137 T o t a l Converted (g) C - 73.225, H - 15.765, 0 -- 119.597 Note: A l l the X values f o r both runs are c a l c u l a t e d based on the i n i t i a l moles of carbon i n the chars. 

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