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Development of slag-resistant refractory linings Sarkar, Dipankar 1984

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DEVELOPMENT OF SLAG-RESISTANT REFRACTORY LININGS By DIPANKAR/SARKAR B.Tech., Indian Institute of Technology, Kharagpur, 1 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in THE FACULTY OF GRADUATE STUDIES Department of Metallurgical Engineering We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA .July 1984 (T) Dipankar Sarkar, 1984 f6 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and study. I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying o f t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the head of my department or by h i s or her r e p r e s e n t a t i v e s . I t i s understood t h a t copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without my w r i t t e n p e r m i s s i o n . Department of The U n i v e r s i t y of B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 DE-6 (3/81) i i ABSTRACT Attempts have been made to d e v e l o p s l a g r e s i s t a n t r e f r a c t o r y l i n i n g f o r Dore f u r n a c e s , which a r e p r i m a r i l y used f o r s m e l t i n g Pb-anodes i n o r d e r t o e x t r a c t p r e c i o u s m e t a l s . A l l the p h y s i c a l p r o p e r t i e s o f Dore s l a g (PbO-based) such a s , m e l t i n g t e m p e r a t u r e , m e l t d e n s i t y , v i s c o s -i t y , s u r f a c e t e n s i o n and w e t t i n g b e h a v i o u r o v e r the tempera-t u r e range o f f u r n a c e o p e r a t i o n s (600-1100°C) were d e t e r -mined. These s t u d i e s i n d i c a t e d t h a t Dore s l a g s ( i ) melt at t e m p e r a t u r e s between 550 and 600°C; ( i i ) have 3 the m e l t d e n s i t i e s 5.0 t o 7.0 g/cm i n the t e m p e r a t u r e range 750-1050°C, melt d e n s i t y p r i m a r i l y b e i n g c o n t r o l l e d 3 by the c o n c e n t r a t i o n o f Pb0(P 2 Q O Q-8.0 g/cm ) and B.i'^O^ 3 (P2QOC-8.9 g/cm ); ( i i i ) a r e h i g h l y f l u i d i n the tempera-t u r e range 750-1050°C, h a v i n g the v i s c o s i t y o f 0.4 t o 0.8 N.S.m ; ( i v ) have low s u r f a c e t e n s i o n v a l u e s 450 to 325 dyne.cm - 1 a t 750°C and (v) have low c o n t a c t a n g l e s between 15 and 30° on alu m i n a s u b s t r a t e s . These s l a g p r o p e r t i e s i n d i -c a t e t h a t the s l a g s would s p r e a d v e r y e a s i l y on al u m i n a r e -f r a c t o r i e s and most p o s s i b l y on o t h e r r e f r a c t o r i e s . C o a t i n g c o m p o s i t i o n s were then d e v e l o p e d by s t u d y i n g the a v a i l a b l e phase e q u i l i b r i u m diagraim/s, w i t h the c o n s i d e r a -t i o n t h a t a g l a s s y component would be n e c e s s a r y i n the c o a t i n g t o s e a l - u p the p o r e s . S l a g p i l l t e s t s on c o a t e d b r i c k s r e v e a l e d t h a t o n l y a p p l i c a t i o n o f a c o a t i n g c o u l d not p r e v e n t s i g n i f i c a n t s l a g p r e n e t r a t i o n . T h i s i s so i n s p i t e o f the f a c t t h a t the c o a t i n g c o m p o s i t i o n s c o n t a i n e d 60-70 s i l i c a to form a l a r g e amount o f g l a s s y phase i n the c o a t i n g . To reduce the harmful e f f e c t o f s l a g con-s t i t u e n t s , CaO was found to be the b e s t o x i d e to produce h i g h t e m p e r a t u r e m e l t i n g compounds by r e a c t i n g w i t h o x i d e c o n s t i t u e n t s i n s l a g s . F u r t h e r s t u d i e s on i m p r e g n a t i n g the b r i c k s w i t h CaO and C a C ^ show t h a t an optimum i m p r e g n a t i o n o f b r i c k s w i t h i> 2 wt.% C a C ^ , and a c o a t i n g o f a m i x t u r e o f 30% CaO, 60% S i 0 2 and 10% s l a g on the impregnated b r i c k s , have been a b l e to s t o p s l a g p e n e t r a t i o n i n t o the r e f r a c t o r y b r i c k s . iv TABLE OF CONTENTS Page Abstract i i Table of Contents iv L i s t of Tables v i i i L i s t of Figures . i x Acknowledgement x i i i Chapter 1 INTRODUCTION .' 1 1.1 Refractory Usage ... 1 1.2 Refractory Failure 2 1.3 Refractory Lining Repair 3 1.4 Remedies for Refractory Failure 4 1.5 Problems Associated with Conventional Remedies .. 5 1.5.1 Dense Refractories . 5 1.5.2 Water Cooling 9 1.5.3 Water-cooled Panels 1,0 1.5.4 Refractory Impregnation .. 1 0 1.6 Refractories in Ferrous Metallurgy ^2 1.7 Refractories in Non-Ferrous Metallurgy 1 3 1.7.1 Lead Metallurgy 1 4 1.7.2 Possible Approaches Towards Solving the Problem of Refractory Corrosion in Dore Furnaces ^ 24 1.7.3 Dore Furnace Slags V Chapter Page 1.8 Objectives of this Investigation 26 2 EXPERIMENTAL PROCEDURES AND RESULTS . 2 8 2.1 Materials Studied 2 8 2.2 Slag Properties 2 8 2.2.1 Chemical Properties 2 8 2.2.2 Chemical Composition 2 9 2.2.3 Slag Structure 2 9 2.2.4 Physical Properties 30 2.2.4.1 Melting Point Determination 30 2.2.4.2 Visc o s i t y of Slags 36 2.2.4.3 Surface Tension and Melt Density 50 2.2.4.4 Melt Density 5 6 2.2.4.5 Experimental Procedure 6 0 2.2.4.6 Results and Analysis 6 6 2.2.4.7 Contact Angle 6 9 2.2.4.8 Conclusion . 8 1 3 DEVELOPMENT OF COATINGS 8 8 3.1 Coating Composition 0:7 3.1.1 Properties Required 8 9 3.1.2 Choice of Brick and Slag 9 1 no 3.1.3 Basis of Coating Development 94 3.1.4 Coating Composition v i Chapter Page 3.1.4.1 Phase Diagrams Relevant to Coating Composition Development.. 94 3.1.4.2 Coating Development Experiments.. 98 3.1.5 Coating A4. 104 3.1.5.1 Coating Materials 104 3.1.5.2 Coating Preparation 104 3.1.5.3 Coating Applications 104 3.1.5.4 Testing of Coating A4 .. 105 3.1.5.5 Determination of Slag-Penetration ,;,> Depth 105 3.1.5.6 Results and Discussion 107 3.2 Ca0-Si0 2-Slag Coatings 1 ° 7 3.2.1 Coating Composition 1 ° 7 3.2.2 Low Ca0-Si0 2 Coatings ... 1 0 9 3.2.3 High S i 0 2 Coatings 1 1 3 3.2.3.1 X-ray Diffractometer Studies of . ' the Coatings H 3 3.2.3.2 Coating Preparation ] 1 4 3.2.3.3 Slag Penetration Tests ] 1 5 3.3 Results and Discussion 1 1 5 4 IMPREGNATION OF REFRACTORY BRICKS BY OXIDES AND SALTS 1 1 8 4.1 Introduction 1 1 8 119 4.2 Impregnation v i i Chapter Page 4.2.1 Calculation of Brick Porosity 119 4.2.2 Oxide Impregnation 120 4.2.2.1 Vacuum Suction 122 4.2.2.2 Boiling 1 2 5 4.2.3 Salt Impregnation 1 2 6 4.2.4 Slag Penetration Tests on CaCl 2 Impregnated Bricks I 2 9 4.2.5 Eff e c t of Different wt.% CaCl 2 ' Impregnation on Slag Penetration ^ 2 4.2.6 Impregnation and Coating ^ 3 7 4.3 Reactions Between Coatings, CaCl 2 and Slag 144 4.4 SEM Studies on Slag Penetration 147 4.5 Coatings and Impregnation on Magnecon Bricks .... 153 5 SUMMARY AND CONCLUSIONS I 5 6 SUGGESTIONS FOR FUTURE WORK ] 5 9 BIBLIOGRAPHY I 6 1 APPENDICES 1 Vis c o s i t y of Slags 1 6 5 l a V i s c o s i t y Measurements 1f>9 2 Surface Tension and Density of Slags 1 7 2 3 Correction f o r the Effect of Gravitational Force ' on the Shape of a Sessile Drop 1 7 5 4 Contact Angles of Dore Slags 1 8 0 v i i i LIST OF TABLES Table P a 9 e I Composition of Magnecon B r i c k s 1 6 II S e r v i c e L i f e of Magnesia R e f r a c t o r i e s 2 0 III Composition of Dore" Slags IV Phases I d e n t i f i e d i n Dore Slags . 3 1 V Melting Point of Dore Slags 3 5 VI PbO-Oxide E u t e c t i c s ... 3 6 87 VII P h y s i c a l P r o p e r t i e s of Dore Slags. no V I I I Phase Diagrams f o r Magnecon-Dore Slag Systems IX Phases I d e n t i f i e d i n CaO + Slag C4 Mixtures 1 0 3 X Composition o f Coatings ^ XI P o r o s i t y of Alumina B r i c k s 1 2 0 124 XII CaO Impregnation in Alumina B r i c k s XIII Wt. % CaO Impregnation in Alumina Bricks 1 2 6 XIV CaO Impregnation in Alumina Bricks I 2 8 A l a . l V i s c o s i t y o f DorS Slags 1 7 0 Ala.2 V i s c o s i t i e s o f CaO and Slag Mixtures 1 7 1 A2.1 Surface Tension 1 7 3 A2.2 Density o f Slags 1 7 4 A4.1 Contact Angles o f D i f f e r e n t Slags 1 8 1 182 A4.2 I n t e r f a c i a l Tension of D i f f e r e n t Slags ix LIST OF FIGURES Figure Page 1 S t a b i l i t y and Propagation Behaviour of Cracks 8 2 Flow-Chart for the Dore Process 1 7 3 Simplified Flow-Chart f o r the Dore Process .. ^8 4 Elevation View of a Dore Furnace 1 9 5 Photograph of Corroded Magnecon Refractories 2 2 6 Melting Temperature of Dore Slags 3 3 7 Schematic View of the Viscosity-Measuring Apparatus .. 3 9 8 Schematic View of the Vertical-Furnace 4 2 9 Calibration Plot for the Modified Spindle 4 4 10a Vi s c o s i t y of Dore Slags 4 7 .10b Normalized V i s c o s i t y Plot of Dore Slags .. 11 V i s c o s i t y of Dore Slags 4 9 12 C a p i l l a r y Rise in a Tube 5 3 13 D i f f e r e n t i a l C a p i l l a r y Rise in Tubes 5 3 14 Increase of Capil l a r y Rise of Slags in Alumina Tubes With Time. Time from 1 to r ( i ) 30 sees , ( i i ) 60 sees and ( i i i ) 2 mins. ^ 15 Apparatus Used for the Maximum Bubble Pressure Method. 61 16 Dependence of the Maximum Manometric Height on Bubbling Interval 64 17 Surface Tension of Dore Slags 67 18 Density of Dore" Slags 70 X Figure Page 19(a) Elevation View of a Sessile Drop 7 1 19(b) Surface Tensions Associated with a Sessile Drop 71 20(a) Sessile Drop 7 6 20(b) Incorporation of the Drop in (a) into a Representative C i r c l e — 7^ 21 Sessile Drop Picture of a Slag P e l l e t on an on Alumina Substrate u 22 Contact Angles of Dore Slags on Alumina 8 2 , oo 23 In t e r f a c i a l Tension of Dore Slags with Alumina 24 Density and Vi s c o s i t y of Dore Slags vs Wt.%Pb Content of the Slags 8 5 25 Surface Tension and Content Angle of Slags vs Wt.% Pb Content 8 6 26 Normalized Vi s c o s i t y Plot for CaO Slag C4 Mixtures 100 27 DTA Plot for a 20 Wt.% CaO + Slag C4 Mixture 101 28(a) Picture of a Slag-Penetrated Alumina Brick 106 28(b) Schematic View of the Brick in 28(a) .. 106 29 Slag Penetration in A1 20 3 Bricks 108 30 Ca0-Si0 2 Phase Diagram :... 110 31 DTA Plot for Coating C8 112 32(a) Slag Penetration in A l , ^ Bricks with Coatings 1 : A8, C7 and C8 116 32(b) Slag Penetration in Alumina Bricks with Coatings C6, DI and D2 H 7 xi Figure Page 33 Apparatus Used for Vacuum Suction 123 34 Shows Alumina Bricks a f t e r Slag-button Tests 130 35 Bricks with Varying Amounts of CaCl 2 Impregnation 133 36 Photograph of Cracks in Bricks Due to Excessive ^ CaCl 2 Impregnation 135 37 SEM Photomicrograph of such a Crack 136 38 Slag Penetration Distance vs Wt.% CaCl 2 Impregnation for Coatings A6, C8 and DI 1 3 9 39 Slag Penetration Distance vs Wt. % CaCl 2 Impregnation for Coatings A4, D2 and C6 1 4 0 40 Slag Penetration in Alumina Bricks with Coating A4 and CaCl 2 Impregnation 1 4 1 41 Slag Penetration in Alumina Bricks with Coating i no DI and CaCl 2 Impregnation 42 Slag Penetration in Alumina Bricks with Coatings 14? and CaCl 2 Impregnation 43 Slag Spreading on Alumina Bricks — 1 4 5 44 SEM-EDX Plot for a Slag Attacked Alumina Brick 1 4 8 45 SEM-EDX Plot for a Slag Penetrated CaCl 2 Impregnated 149 Alumina Brick 46 SEM-EDX Plot for a Slag Penetrated Alumina Brick with Coating D2 , o u 47 SEM-EDX Plot f o r a Slag. Penetrated Alumina Brick with 152 CaCl~ Impregnation and Coating D2 x i i Figure Page 48 SEM-EDX Plot for a Slag Penetrated Magnecon Brick with CaCl 2 Impregnation and Coating D2 — 155 A3.1 Sessile Drop 1 7 6 A3.2 Sessile Drop Under the Influence of Gravity I 7 6 A3.3 Plot Used f o r Contact; Angle Corrections I 7 9 x i i i ACKNOWLEDGEMENT I w o u l d l i k e t o t h a n k P r o f . A.C.D. C h a k l a d e r f o r h i s a s s i s t a n c e and g u i d a n c e , and t h e t e c h n i c i a n s and t h e g r a d u a t e s t u d e n t s o f t h e d e p a r t m e n t f o r t h e i r h e l p . Thanks a r e a l s o due t o C o m i n c o , L t d . , f o r t h e i r k i n d c o o p e r a t i o n and a l s o f o r s u p p l y i n g t h e s l a g s a l o n g w i t h t h e i r a n a l y s i s and t h e b r i c k s u s e d f o r t h i s i n v e s t i g a t i o n . F i n a n c i a l s u p p o r t f r o m NSERC i s g r a t e f u l l y a c k n o w l e d g e d . C h a p t e r 1 V. INTRODUCTION 1 • 1 R e f r a c t o r y Usage A l a r g e number of i n d u s t r i e s , both m e t a l l u r g i c a l and n o n - m e t a l l u r g i c a l , use r e f r a c t o r i e s f o r v a r i o u s pur-poses. In the m e t a l l u r g i c a l i n d u s t r i e s , r e f r a c t o r i e s a r e used m a i n l y f o r metal p r o d u c t i o n by p y r o m e t a l l u r g i c a l p r o c e s s e s . The f o l l o w i n g i n d u s t r i e s a r e the prime con-sumers o f r e f r a c t o r y b r i c k s : ^ I r o n and S t e e l I n d u s t r i e s 60% o f the t o t a l ) N o n - f e r r o u s m e t a l s Cement G l a s s P e t r o l e u m and o i l Cerami c Power g e n e r a t i o n In the m e t a l l u r g i c a l i n d u s t r y , the major a r e a s where r e f r a c t o r i e s a r e used can be i d e n t i f i e d a s : S m e l t i n g R o a s t i ng Heat Treatment 2 S o a k i n g P i t Coke Oven L a d l e L i n i n g Tundi sh 1 - 2 R e f r a c t o r y F a i 1 u r e The major c a u s e s of r e f r a c t o r y f a i l u r e can be b r o a d l y c l a s s i f i e d under the f o l l o w i n g c a t e g o r i e s : (a) C o r r o s i o n and E r o s i o n The major cause of r e f r a c t o r y f a i l u r e i n any m e t a l -l u r g i c a l f u r n a c e i s due to the c o r r o s i o n and e r o s i o n o f the r e f r a c t o r y l i n i n g m a t e r i a l s by the molten s l a g . In s l a g c o r r o s i o n , the s o l u t i o n a t the s l a g - r e f r a c t o r y i n t e r f a c e and the d i f f u s i o n o f the d i s s o l v e d r e f r a c t o r y c o n s t i t u e n t s from the i n t e r f a c e t h r o u g h a boundary l a y e r i n t o the s l a g , 2 i s the major r a t e c o n t r o l l i n g f a c t o r . Hence, i t can be e n v i s a g e d t h a t both c o r r o s i o n and e r o s i o n l e a d to r e f r a c -t o r y d i s s o l u t i o n which l e a d s t o t h e i r f a i l u r e . (b) S p a l l i n g S p a l l i n g i s u s u a l l y d e f i n e d as the f r a c t u r e o f r e -f r a c t o r y b r i c k s due to t h e r m a l s t r e s s e s s e t up i n the b r i c k d u r i n g t h e i r use. Thermal s t r e s s e s ean be s e t up by uneven h e a t i n g o r c o o l i n g of the b r i c k due to t e m p e r a t u r e f l u c t u a t i o n s i n s e r v i c e . In the l a t t e r c a s e , the e x p a n s i o n 3 c o u l d be l a r g e enough to produce s h e a r f a i l u r e s . R e f r a c -t o r y m a t e r i a l s (metal o x i d e s ) n o r m a l l y have low t hermal c o n d u c t i v i t y and so when they are s u b j e c t e d to h i g h h e a t i n g o r c o o l i n g r a t e s , t hermal s t r e s s e s can e a s i l y cause f a i l u r e . (c) S l a g P e n e t r a t i o n and S p a l l i n g T h i s s p e c i a l but common cause f o r r e f r a c t o r y 3 f a i l u r e has been c a l l e d s p a l l i n g by some, but i t would be b e t t e r not to c l a s s i f y i t under s p a l l i n g . In t h i s c a s e , the s l a g : i ) p e n e t r a t e s the s u r f a c e l a y e r s o f t h e b r i c k , i i ) r e a c t s w i t h the b r i c k m a t e r i a l , and i i i ) forms v a r i o u s compounds and g l a s s y p hases. The s l a g - p e n e t r a t e d l a y e r , so formed, has a d i f f e r e n t t h e r m a l e x p a n s i o n c o e f f i c i e n t as compared to the r e s t o f the b r i c k , and the s u r f a c e l a y e r c r a c k s , p e e l s or s h e a r s o f f d u r i n g thermal c y c l i n g . 1.3 R e f r a c t o r y L i n i n g R e p a i r The c o s t o f r e p l a c i n g o r r e p a i r i n g r e f r a c t o r y l i n i n g s i s a r e c u r r i n g expense and problem. In c e r t a i n o p e r a t i o n s , where r e f r a c t o r y b r i c k s have to be r e p l a c e d two o r t h r e e times a y e a r , the c o s t i n v o l v e d i n r e f r a c t o r y r e p a i r c o n t r i b u t e s a s i g n i f i c a n t p a r t t o the t o t a l c o s t o f metal p r o d u c t i o n . To g i v e an example, one of the l a r g e s t i r o n and s t e e l p r o d u c e r s i n 4 Canada s p e n t about 40 m i l l i o n d o l l a r s t o p u r c h a s e r e f r a c -t o r i e s i n 1980. I t i s v e r y l i k e l y t h a t they s p e n t a l m o s t the same amount i n s t a l l i n g them. The c o s t o f down-time (shut-down) o f metal p r o d u c i n g u n i t s i s not i n c l u d e d i n the above e s t i m a t e . The t o t a l c o s t i n v o l v e d i n r e f r a c t o r y l i n i n g r e p a i r can be grouped under the f o l l o w i n g c a t e g o r i e s : (a) C o s t o f p u r c h a s i n g r e f r a c t o r i e s . (b) The down-time c o s t o f the metal p r o d u c i n g u n i t s . (c) The l a b o u r c o s t o f i n s t a l l i n g the r e f r a c t o r i e s . 1.4 Remedies f o r R e f r a c t o r y F a i l u r e Due to many f a c t o r s , t h e problem of r e f r a c t o r y b r i c k d i s s o l u t i o n by s l a g s c a n n o t be p r e v e n t e d i n p r a c t i c e , but r e c e n t developments have i n d i c a t e d t h a t r e f r a c t o r y f a i l u r e , due t o s p a l l i n g o r s l a g a t t a c k , can be r e d u c e d s i g n i f i c a n t l y . In the f o l l o w i n g s u b s e c t i o n s , r e f r a c t o r y f a i l u r e by s l a g a t t a c k w i l l be emphasized more i n comparison to thermal f a i l u r e as ( i ) t h i s k i n d o f f a i l u r e i s more common and ( i i ) the p r e s e n t work i s d i r e c t e d towards the s t u d y o f s l a g a t t a c k on r e f r a c t o r i e s . The s l a g c o r r o s i o n problem i s c o n v e n t i o n a l l y h a n d l e d by the f o l l o w i n g methods: 5 (a) Use o f dense r e f r a c t o r i e s whenever a v a i l a b l e (b) Chemical c o m p o s i t i o n mani pul a t i o n - e s ' s e n t i a l l y i n -v o l v i n g the s e a r c h f o r a c h e m i c a l l y i n e r t r e f r a c t o r y m a t e r i a l (c) Water c o o l i n g o f r e f r a c t o r y l i n i n g s (d) Replacement o f r e f r a c t o r i e s or f u r n a c e w a l l s en-t i r e l y by t h e use o f w a t e r - c o o l e d metal p a n e l s (e) F i l l i n g the pores i n r e f r a c t o r i e s w i t h c a r b o n ( f ) The use o f s p e c i a l r e f r a c t o r i e s l i k e s i l i c o n c a r b i d e , s i l i c o n n i t r i d e , e t c . 1. 5 Problems A s s o c i a t e d w i t h C o n v e n t i o n a l Remedies ]. 5 . -j Dense R e f r a c t o r i e s Dense r e f r a c t o r i e s have two main drawbacks: (a) 4-8 poor t h e r m a l shock p r o p e r t i e s ~ ••(b) the h i g h c o s t and d i f f i c u l t y i n v o l v e d i n t h e i r f a b r i c a t i o n . As a m a t t e r o f f a c t , v e r y few such r e f r a c t o r i e s a r e c o m m e r c i a l l y a v a i l a b l e . The b a s i c r e q u i r e m e n t s o f a r e f r a c t o r y b r i c k are h i g h t h e r m a l shock r e s i s t a n c e c o u p l e d w i t h low thermal c o n d u c t i v i t y . The l a t t e r p r o p e r t y i s n e c e s s a r y and impor-t a n t , as r e f r a c t o r i e s s h o u l d a l s o p o s s e s s i n s u l a t i n g p r o -8 9 p e r t i e s . K i n g e r y and Hasselman showed t h a t good thermal shock r e s i s t a n c e r e q u i r e s h i g h thermal c o n d u c t i v i t y , but h i g h t h e r m a l c o n d u c t i v i t y i n r e f r a c t o r i e s o b v i o u s l y l e a d s 6 to poor i n s u l a t i n g p r o p e r t i e s . T h i s means good t h e r m a l shock r e s i s t a n c e and low t h e r m a l c o n d u c t i v i t y are m u t u a l l y i n c o m p a t i b l e . I t has been shown by HasseTman, Smith and co-5 4 w o r k e r s , and G a r v i e and N i c h o l s o n t h a t i n h e r e n t p o r o s i t y o r i n d u c e d p o r o s i t y i n r e f r a c t o r i e s up t o a c e r t a i n degree h e l p s t o i n c r e a s e the t h e r m a l shock p r o p e r t i e s . T h e i r work was done p r i m a r i l y on a l u m i n a ( A l 2 ^ 3 ) and p a r t i a l l y s t a b i l i z e d z i r c o n i a ( P S Z ) , but t h e i r c o n c l u s i o n s can be e x t r a p o l a t e d to o t h e r r e f r a c t o r i e s as w e l l . Pores i n 5 b r i c k s can a c t both as c r a c k i n i t i a t o r s and a r r e s t o r s . So,, i n the l a t t e r case an i n c r e a s e d p o r o s i t y l e a d s to a d e c r e a s e i n c r a c k l e n g t h . The shape and d i s t r i b u t i o n o f 5 10 the pores ' a l s o seem': to have a b e a r i n g on the t h e r m a l shock p r o p e r t i e s . In the above d i s c u s s i o n , the term 'thermal shock' i s d i r e c t l y r e l a t e d t o the s t r e n g t h r e -t a i n e d i n a r e f r a c t o r y b r i c k a f t e r a thermal shock t e s t . 6 ' 1 1 ' 1 2 T h i s term can be f u r t h e r e l a b o r a t e d q u a n t i t a t i v e l y . H a s s e l -man d e v e l o p e d an e q u a t i o n to p r e d i c t the c r i t i c a l t e m p e r a t u r e d i f f e r e n c e ( & T c ) r e q u i r e d f o r the i n i t i a t i o n o f c r a c k p r o -p a g a t i o n which i s : HT c = x ( 1 + 2TTN£ 2) •na EZ where the symbols a, E and G r e f e r t o the c o e f f i c i e n t o f thermal e x p a n s i o n , Young's modulus o f e l a s t i c i t y and the 7 f r a c t u r e s u r f a c e e n e r g y , r e s p e c t i v e l y . F i g u r e 1 shows AT c as a f u n c t i o n o f c r a c k l e n g t h . From t h i s f i g u r e i t can be seen t h a t when i < i' , m A T c d e c r e a s e s w i t h i n c r e a s i n g c r a c k l e n g t h and i s i n d e p e n -dent o f c r a c k d e n s i t y . When % > &m, 'AT - i n c r e a s e s r a p i d l y w i t h both t h e c r a c k l e n g t h and the c r a c k d e n s i t y . The r e a s o n f o r t h i s i s t h a t the p r e s e n c e o f the c r a c k s r e d u c e s the e f f e c t i v e v a l u e o f Young's modulus ( E ) . For c r a c k l e n g t h s > £ m , t h e v a l u e o f AT £ can be i n c r e a s e d s i m p l y by i n c r e a s i n g the c r a c k d e n s i t y 'N'. 7 4 R o s s i , G a r v i e and N i c h o l s o n who worked on m i c r o -c r a c k e d MgO-W c o m p o s i t e s and p a r t i a l l y s t a b i l i z e d z i r c o n i a (PSZ) r e s p e c t i v e l y , v e r i f i e d t h a t m i c r o c r a c k i n g and p o r o s i t y i n c r e a s e d the thermal shock p r o p e r t i e s o f c e r a m i c s . So i t can be c o n c l u d e d t h a t the use o f dense ( a l m o s t 100%) r e -f r a c t o r i e s may not be a s u i t a b l e remedy f o r s l a g a t t a c k . Dense r e f r a c t o r i e s c o u l d be used to p r e v e n t s l a g 1 3 p e n e t r a t i o n but i t has been shown t h a t s l a g s can a l s o p e n e t r a t e a l o n g g r a i n b o u n d a r i e s . So c o n s i d e r i n g the c o s t and e f f o r t s needed i n d e v e l o p i n g such b r i c k s and a t the expense o f t h e r m a l p r o p e r t i e s , i t may not be an e f f e c t i v e way i n p r e v e n t i n g s l a g p e n e t r a t i o n and c o r r o s i o n . F i g . 1: S t a b i 1 i t y C Ref. 9 ) and P r o p a g a t i o n B e h a v i o u r o f C r a c k s . 9 D e v e l o p i n g a new r e f r a c t o r y f o r a s p e c i f i c k i n d o f a f u r n a c e and s l a g i s not v e r y f e a s i b l e due to the l a c k o f i n f o r m a t i o n ( e s s e n t i a l l y phase diagrams) i n the f i e l d o f c e r a m i c s . A l t h o u g h t h e r e a r e q u i t e a number o f phase diagrams on b i n a r y and t e r n a r y o x i d e s y s t e m s , t h e s e a r e n ' t o f much h e l p when c o n s i d e r i n g complex r e f r a c t o r y - s l a g prob-1 ems. D e v e l o p i n g a c h e m i c a l l y i n e r t b r i c k w i t h a l l the r e q u i r e d p h y s i c a l ( c r u s h i n g s t r e n g t h and modulus o f r u p t u r e ) and thermal ( t h e r m a l shock and i n s u l a t i o n ) p r o p e r t i e s may not be p o s s i b l e , even i f c h e m i c a l l y i n e r t m a t e r i a l s can be found o r d e v e l o p e d . 1.5.2 Mater C o o l i n g Water c o o l i n g o f r e f r a c t o r i e s i s a p o s s i b i l i t y but here the f u r n a c e and the r e f r a c t o r y l i n i n g d e s i g n would have to be changed,which would i n v o l v e e l a b o r a t e r e - d e s i g n -i n g . T h i s method would o b v i o u s l y r e q u i r e a l a r g e c a p i t a l i n v e s t m e n t . T h i s approach i s f o l l o w e d s p e c i a l l y i n t h e f e r r o u s -e x t r a c t i v e i n d u s t r y . In the b l a s t f u r n a c e , the t e m p e r a t u r e i n the lower zone ( h e a r t h , bottom, bosh and t u y e r e r e g i o n ) i s i n the o r d e r o f 1300-1800 oC; here the r e f r a c t o r i e s ( c a r b o n , f i r e b r i c k , f u s e d a l u m i n a and z i r c o n i a ^ a l u m i n a ) a r e water c o o l e d . Water c o o l e d c a r b o n l i n i n g s a r e a l s o used i n the c a s e o f c a s t i r o n C u p o l a s i n the lower p a r t s o f the s h a f t r e g i o n . In the n o n - f e r r o u s i n d u s t r y , where the o p e r a t i n g t e m p e r a t u r e s a r e not v e r y h i g h compared to b l a s t f u r n a c e s and s t e e l - m e l t i n g f u r n a c e s , t h e use o f c o o l i n g o f r e f r a c t o r i e s (by a i r o r water) i s somewhat l e s s p r e v a l e n t . To c i t e some examples: the bottoms of copper anode r e f i n -i n g f u r n a c e s are c o o l e d by a i r or a t times by water*, water c o o l i n g i s used i n e l e c t r i c s t e e l making e x t e n s i v e l y . 1.5.3 W a t e r - c o o l e d P a n e l s Removing r e f r a c t o r i e s a l t o g e t h e r and r e p l a c i n g them by w a t e r - c o o l e d metal p a n e l s ( o r w a l l s ) i s a N p o s s i b i 1 i t y but t h i s a g a i n , as i n the p r e v i o u s e a s e , i n v o l v e s a l a r g e c a p i t a l i n v e s t m e n t an.d a. re-design "of the f u r n a c e . In t h i s e a s e , t h e p r o t e c t i v e c o a t i n g on the w a l l s i s o b t a i n e d by the s l a g i t s e l f , as the s l a g s o l i d i f i e s when i t comes i n c o n t a c t w i t h the c o l d , w a t e r - c o o l e d w a l l s . 1.5.4 R e f r a c t o r y I m p r e g n a t i o n F i l l i n g r e f r a c t o r y pores w i t h c a r b o n has been p r a c t i c e d from as e a r l y as the l a t e 1800s. These e a r l y r e f r a c t o r i e s were made from m i x t u r e s o f de a d - b u r n t d o l o m i t e and p i t c h ( t a r ) , and were used p r i m a r i l y i n b a s i c - b e s s e m e r f u r n a c e s . At p r e s e n t , r e f r a c t o r y b r i c k s , used i n the i r o n and s t e e l i n d u s t r y , and s p e c i a l l y i n B a s i c Oxygen P r o c e s s 14 (BOP), a r e a l m o s t always P i t c h - B e a r i n g MgO-CaO r e f r a c t o r i e s . When t h e s e p i t c h b e a r i n g r e f r a c t o r i e s are i n i t i a l l y h e a t e d , by c h a r g i n g hot coke i n the c o l d BOP f u r n a c e , the r a p i d h e a t i n g (38°C/min) to about T095°C i g n i t e s t h e p i t c h i n the r e f r a c t o r y l i n i n g . The vapours produced by t h i s i g n i t i o n , moves away from the hot f a c e and d e p o s i t s c a r b o n i n the c o n s t r i c t e d ends o f pores a t a p o s i t i o n where the c a r b o n i z a -t i o n t e m p e r a t u r e i s r e a c h e d . The c a r b o n i n t h e s e b r i c k s 1 5 c o u l d be about 3-4% by w e i g h t . These b r i c k s a r e more c o r r o s i o n r e s i s t a n t , as s u g g e s t e d by t h e i r use i n the BOP. Carbon p r e v e n t s the c o r r o s i o n o f t h i s r e f r a c t o r y b r i c k ( m a i n l y Magnesia and M a g n e s i a - C a l c i a ) by the methods p r o -15 16 posed by Park and B a r r e t t , Kappmeyer and Hubble, Howe 17 18 and McGee, Brezny and Landy and o t h e r s : (a) The carb o n p h y s i c a l l y p r e v e n t s the e n t r y o f the s l a g i n t o the b r i c k as the s l a g - c a r b o n c o n t a c t a n g l e i s q u i t e l a r g e ( g r e a t e r than 9 0 ° ) . 1 6 1 9 (b) Robinson p r o p o s e d t h a t the p r e s s u r e o f the carbon monoxide gas produced by the r e d u c t i o n o f MgO i n the b r i c k by the c a r b o n ( a l s o p r e s e n t i n the b r i c k ) a c c o r d i n g to the r e a c t i o n : 12 MgO(s) + C ( s ) •+ Mg(gr) + CO(g) 1.2 p r e v e n t s o r r a t h e r d e l a y s the p e n e t r a t i o n o f s l a g i n t o the b r i c k . 20 ( c ) C h e s t e r s p r o p o s e d t h a t t h a t carbon i n the r e -f r a c t o r y b r i c k r e d u c e s t h e f e r r i c o x i d e ( o r c a l c i u m f e r -r i t e ) i n t o FeO o r even m e t a l l i c i r o n , b o t h o f which a r e v i r t u a l l y n o n - c o r r o s i v e to magnesia (MgO) and l i m e (CaO) i n the b r i c k . 15 18 R e c e n t l y , * i t has been shown t h a t t h e carb o n i n the r e f r a c t o r y b r i c k s used i n BOP's has c e r t a i n drawbacks. I t seems t h a t t h e c a r b o n i n t h e b r i c k r e d u c e s the magnesia and the magnesi um vapour thus- p r o d u c e d l e a v e s t h a t p a r t i c u l a r r e g i o n . T h i s i n c r e a s e s b r i c k p o r o s i t y and l e a d s , e v e n t u a l l y , t o a d e c r e a s e i n the s t r e n g t h o f t h e b r i c k . When carbo n i m p r e g n a t e d a l u m i n a b r i c k s were used 1 5 i n a sodium t e t r a b o r a t e m e l t and a sodium vanadate m e l t , the c a r b o n was r a p i d l y o x i d i z e d t o CO2 gas. The e v o l u t i o n o f gas from the i n n e r pores o f a r e f r a c t o r y c o u l d g i v e r i s e to m i c r o - and m a o r o - c r a c k i n g . 1.6 R e f r a c t o r i e s i n F e r r o u s M e t a l l u r g y As mentioned b e f o r e , the F e r r o u s M e t a l l u r g y 13 i n d u s t r y i s the major consumer (A, 60%) o f a l l r e f r a c t o r i e s . So, i t i s q u i t e u n d e r s t a n d a b l e t h a t most of the r e f r a c t o r y development has been done i n t h i s f i e l d . Some r e c e n t developments i n t h i s f i e l d i n c l u d e t h e use o f : (a) g r a p h i t e - S i C b r i c k s i n the bosh r e g i o n o f the b l a s t f u r n a c e by the J a p a n e s e . (b) S i C and S i 3 N 4 b r i c k s i n the m i d d l e and upper s e c t i o n s o f b l a s t f u r n a c e s . S e r v e r e a b r a s i o n o c c u r s i n t h e s e s e c t i o n s , due to the passage o f l i m e s t o n e , coke and i r o n o r e s i n t e r s . (e) a i r and water c o o l e d g r a p h i t e b r i c k s i n the h e a r t h r e g i o n o f b l a s t f u r n a c e s , where the o p e r a t i n g t e m p e r a t u r e s are v e r y h i g h . (d) c a r b o n i m p r e g n a t e d b r i c k s i n the B a s i c Oxygen Furnace ( s e c t i o n 1.5.5 ) and a l s o i n t h e LD p r o c e s s o f s t e e l making. S l a g a t t a c k on r e f r a c t o r i e s i s v e r y s e v e r e i n t h e s e p r o -c e s s e s , due t o h i g h t e m p e r a t u r e s employed. Such b r i c k s can be used f o r about 300 h e a t s i n the BOF and f o r about 3000 h e a t s i n the QB0P. 1 1. 7 R e f r a c t o r i e s i n Non-Ferrous M e t a l l u r g y In the f i e l d o f n o n - f e r r o u s m e t a l l u r g y , v e r y l i t t l e work has been done towards the development of r e f r a c t o r i e s as compared to f e r r o u s m e t a l l u r g y . The 14 development o f r e f r a c t o r i e s i n t h i s f i e l d i s v e r y d i f -f i c u l t , due to the l a c k o f phase e q u i l i b r i a f o r systems i n v o l v i n g n o n - f e r r o u s s l a g s and o x i d e s . The o n l y development has been an i n c r e a s e d use of 3 b a s i c r e f r a c t o r i e s i n n o n - f e r r o u s m e t a l l u r g y . Most o f the r e f r a c t o r i e s a r e s e l e c t e d on a t r i a l and e r r o r b a s i s ; 1 the f a c t o r s f o r c h o o s i n g the b e s t r e f r a c t o r y b e i n g i t s c o s t , a v a i l a b i l i t y and r e s i s t a n c e to s l a g a t t a c k . No a p p a r e n t a t t e m p t has eve r been made to d e v e l o p new r e f r a c t o r i e s f o r s p e c i a l i z e d a p p l i c a t i o n s i n non-f e r r o u s m e t a l l u r g i c a l f u r n a c e s . T h i s i s t r u e f o r the Copper, N i c k e l , Lead and o t h e r n o n - f e r r o u s m e t a l l u r g i c a l i n d u s t r i e s . I t ean be s a i d t h a t the major developments and improvements t h a t can be made i n the f i e l d o f r e f r a c -t o r i e s l i e i n n o n - f e r r o u s m e t a l l u r g i c a l a p p l i c a t i o n s . 1.7.1 Lead Metal 1urgy In the p r o c e s s o f l e a d e x t r a c t i o n , the v a l u a b l e e l ements l i k e g o l d and s i l v e r a r e c o n c e n t r a t e d i n the l e a d anodes. When t h e s e l e a d anodes ( b u l l i o n ) a r e f u r t h e r p u r i f i e d , t h e p r e c i o u s m e t a l s ( g o l d and s i l v e r ) a l o n g w i t h b i s m u t h , antimony, c o p p e r , a r s e n i c , s i l i c o n and z i n c pass i n t o the anode s l i m e . T h i s s l i m e i s m e l t e d y i e l d i n g ' B l a c k M e t a l ' (26 o z / t o n Au, 7000 o z / t o n Ag, 20 wt.% Pb, 40 wt.! Sb, 15 wt. % As, 5 wt.% Bi. and 3 wt.% Cu). The B l a c k Metal i s b u r n t down i n Dore f u r n a c e s i n d i f f e r e n t s t a g e s and e v e n t u a l l y s i l v e r and g o l d a r e r e c o v e r e d and f u r t h e r p u r i f i e d by e l e c t r o l y s i s ( F i g s . 2 and 3 ) . The r e f r a c t o r y b r i c k s used i n t h e s e Dore f u r n a c e s are e s s e n t i a l l y Magneeon ( T a b l e I ) . The s l a g s t h a t a r e g e n e r a t e d i n t h e s e d i f f e r e n t 'Dore burndowns' ( f i g . 3 ) , have d i f f e r e n t c o m p o s i t i o n s which a r e l i s t e d i n T a b l e I I . I t can be seen t h a t the s l a g s have h i g h l e a d , a r s e n i c , bismuth and antimony c o n c e n t r a t i o n s . The Dore f u r n a c e i s ' e s s e n t i a l l y an o v a l - s h a p e d domed f u r n a c e i n the p l a n view. From F i g . 2, i t can be noted t h a t the maximum t e m p e r a t u r e i n any o f t h e s e f u r n a c e s i s l e s s than 1100°C. Temperature here i s not as s e v e r e as i n the ease o f most f u r n a c e s used i n the f e r r o u s m e t a l l u r g i c a l i n d u s t r y . Most o f the r e f r a c t o r y d i s s o l u t i o n t a k e s p l a c e a t the s l a g l e v e l and a t the r o o f l e v e l . F i g . 4 shows an e l e v a t i o n view o f the f u r n a c e . I t can be seen t h a t h i g h duty f i r e c l a y b r i c k s a r e used on the bottom and c o r r o s i o n here i s not so s e v e r e . T h i s i s due to t h e f a c t t h a t a t the bottom, most o f the melt i s i n the m e t a l l i c s t a t e and 16 T a b l e I C o m p o s i t i o n o f Magnecon B r i c k s C o n s t i t u e n t s wt. % S i 0 2 9.0 CaO 18.3 F e 2 ° 3 7.6 A 1 2 ° 3 3.9 C r 2 ° 3 7.9 MgO 53. 3 Slag "A" 700oC Slag "B" 1080°C Slag "B" 1080°C Drum-Shaped No. 3 Furnace Mild Reduction B1/Pb A l l o y Slag "C" 1040 eC Slimes Melting Metal Bumdown No. 4 Dore Mild Oxidation Metal Burndown No. 5 Dore Mi l d Oxidation Metal Plus Slag "D" 840°C Metal Plus Slag "D" 840°C No. 1 Dore Strong Oxidation No. 2 Dor£ Strong Oxidation Metal Metal Parting C e l l s G o l d / S i l v e r 2 Flow-Chart for the Dore Process. Impure Lead Bullion (Anodes) Anode Slime Slime Block Metal (Au, (Ag,Au,Bi,Sb,As) Melting Ag.Pb.Sb, As, Bi.Cu) Ag. Au Burn-down Furnace removes Sb 8 As at ~ 8 0 0 B C Burn-down Metal I Dore Furnoce (~IIOO°C) removes Pb,Bi, Cu as Litharge Slog 1 Dore Furnoce Metal 99 % A g a ~ 0 5 % Au 1 Electrorefining 3 S i m p l i f i e d Flow-Chart f o r the Dore P r o c e s s . F i g . 4 E l e v a t i o n View of a Dore F u r n a c e . 20 T a b l e II S e r v i c e L i f e o f Magnesia R e f r a c t o r i e s . S l a g Average L i f e o f 9" Magnesia R e f r a c t o r i e s A 9 - 1 2 months B 3 - 5 C 9 - 1 2 D 6 - 1 2 C o m p o s i t i o n and s e r v i c e t e m p e r a t u r e o f above s l a g s . Slag Temp °C % Cu % Pb % Zn % Sb % As % Bi % S i 0 2 1 A 700 9.2 26.0 0.2 39.0 7.0 0.3 10.0 B 1080 10.0 47.0 0.2 7.0 3.0 18.0 1.5 C 1040 2.7 42.0 4.0 17.0 3.0 2.0 5.0 D 840 10.0 47.0 0..2 7.0 3.0 18.0 1.5 21 i t does n o t wet t h e r e f r a c t o r i e s and c o n s e q u e n t l y d o e s n o t c o r r o d e . Magnecon b r i c k s ( T a b l e I) seem t o o p e r a t e b e s t i n Dore' f u r n a c e s as c o m p a r e d t o t h e o t h e r s t a n d a r d commerci a l l y a v a i l a b l e b r i c k s . The a v e r a g e l i f e o f h i g h m a g n e s i a - c h r o m e r e f r a c t o r i e s i n t h e s l a g - l i n e and r o o f i n d i f f e r e n t Dore' f u r n a c e s i s l i s t e d i n T a b l e I I ( s u p p l i e d by C o m i n c o ) . I t can be s e e n t h a t s l a g 'B' ( T a b l e I I ) i s t h e most c o r r o s i v e o f a l l s l a g s . The s e v e r i t y o f s l a g a t t a c k c a n be s e e n i n F i g . 5, where a 9 i n c h magnecon b r i c k was r e d u c e d t o a b o u t 1.75 i n c h e s i n j u s t 72 d a y s by s l a g B a t a b o u t 1 0 8 0 ° C . The c o s t o f t h e s e b r i c k s and t h a t o f r e p l a c i n g them i s q u i t e 1 a r g e . S l a g 'B' and s l a g 'D' have s i m i l a r c o m p o s i t i o n s b u t t h e o p e r a t i n g t e m p e r a t u r e i n t h e c a s e o f s l a g 'B' i s much h i g h e r (by a b o u t 2 4 0 ° C ) t h a n i n t h e c a s e o f s l a g 'D'. So i t c a n be s a i d t h a t t h e r e f r a c t o r y d i s s o l u t i o n r a t e (in r e l a t i v e t e r m s ) d e p e n d s p r i m a r i l y on t h e o p e r a t i n g t e m p e r a t u r e o f t h e f u r n a c e . 1.7.2 P o s s i b l e A p p r o a c h e s T o w a r d s S o l v i n g t h e P r o b l e m o f R e f r a c t o r y C o r r o s i o n i n Dore F u r n a c e s The s o l u t i o n t o t h e p r o b l e m i n t h i s s p e c i f i c c a s e 22 F i g . 5 P h o t o g r a p h o f C o r r o d e d Magnecon R e f r a c t o r i e s . 23 i s to d e v e l o p a r e f r a c t o r y l i n i n g m a t e r i a l f o r Dore f u r n a c e s which can r e s i s t the a t t a c k o f h i g h l y c o r r o s i v e l e a d - b e a r i n g s l a g s . The problem ean.be approached i n two ways: ( i ) Development o f an e n t i r e l y new r e f r a c t o r y body c o m p o s i t i o n based on s l a g - o x i d e c h e m i s t r y . T h i s would e s s e n t i a l l y i n v o l v e the t e d i o u s p r o c e d u r e o f making s u i t a b l e phase diagrams because most o f the diagrams needed f o r d e v e l o p i n g s p e c i a l i z e d r e f r a c t o r i e s do not e x i s t . T h i s would c e r t a i n l y be a v e r y l a r g e r e s e a r c h p r o j e c t c o n s i d e r i n g a l l the work to be done. F u r t h e r m o r e even i f a new r e f r a c -t o r y b r i c k can be d e v e l o p e d i n t h i s manner, a s u i t a b l e and w i l l i n g m a n u f a c t u r e r f o r such a b r i c k may not be easy to f i n d . ( i i ) Development o f a r e f r a c t o r y c o a t i n g f o r c o m m e r c i a l l y a v a i l a b l e r e f r a c t o r y m a t e r i a l s . T h i s seemed to be the b e s t p o s s i b l e approach to the problem f o r t h i s s t u d y . When t h i s i n v e s t i g a t i o n was s t a r t e d , i t was soon r e a l i z e d t h a t no work had been done i n t h i s f i e l d b e f o r e , s o, t h e r e wasn't much r e f e r e n c e i n f o r m a t i o n a v a i l a b l e . However i t can be s a i d t h a t t h i s l a t t e r a p p r o a c h appears to be more v i a b l e and l e s s t i m e consuming as compared to t h e p r e v i o u s one. Moreover, i f a s l a g - r e s i s t a n t c o a t i n g f o r c o n v e n t i o n a l r e f r a c t o r i e s can be developed.,: any Dore f u r n a c e u s e r s h o u l d be a b l e t o make t h i s c o a t i n g m a t e r i a l i n - p l a n t and a p p l y i t to the b r i c k s . 24 I t s h o u l d be mentioned h e r e , t h a t no c o a t i n g can r e s i s t the a t t a c k o f molten s l a g s , but a good c o a t i n g s h o u l d slow down the s l a g a t t a c k . 1.7.3 Dore" Furnace S l a g s The o n l y i n f o r m a t i o n a v a i l a b l e on the Dore' f u r n a c e s l a g s i s t h e i r c o m p o s i t i o n ( T a b l e I I I ) . The i m p o r t a n t s l a g p r o p e r t i e s r e q u i r e d to s t u d y the i n t e r a c t i o n s between r e f r a c t o r y o x i d e s and the s l a g s a r e p h y s i c a l p r o p e r t i e s such as : ( i ) s u r f a c e t e n s i o n and m e l t d e n s i t y ( i i ) v i scos i t y ( i i i ) m e l t i n g p o i n t s ( i v ) w e t t i n g c h a r a c t e r i s t i c s and (v) w e i g h t l o s s on h e a t i n g . None o f the above p h y s i c a l p r o p e r t i e s o f the s l a g s were known when the work was s t a r t e d . Even to d e v e l o p a r e f r a c -t o r y c o a t i n g as d e s c r i b e d i n s e c t i o n (1..7...2), i t i s h e l p f u l to know the phase r e l a t i o n s between the s l a g c o n s t i t u e n t s and the o x i d e s i n the b r i c k . However, some phase e q u i l i -b r i a diagrams r e l e v a n t to t h i s s t u d y are a v a i l a b l e o n l y as b i n a r y d i a g r a m s . These are l i s t e d l a t e r a l o n g w i t h t h e i r l o w e s t e u t e c t i c t e m p e r a t u r e s and t h e i r numbers as t h e y appear i n Ref. ( 2 1 ) . On the b a s i s o f the l i t e r a t u r e s u r v e y T a b l e I I I C o m p o s i t i o n of Dore S l a g s i n wt.%. S l a g Temp °C % Cu % Pb % Zn % Sb % As % Bi % S i 0 2 A 700 9.2 26.0 0.2 39.0 7.0 0.3 10.0 B 1080 10.0 47.0 0.2 7.0 3.0 18.0 1.5 C 1040 2.7 42.0 4.0 17.0 3.0 2.0 5.0 D 840 10.0 47.0 0.2 7.0 3.0 18.0 1.5 CI - 2.0 48. 7 - 22.0 5.1 0.8 -C2 - 4.5 49.0 - 16.5 3.4 6.7 -C3 - 2.6 76.8 - 2.0 0.7 1 . 7 -C4 - 10.4 31 .6 0.3 2.5 0.2 41 .2 0.4 The c o m p o s i t i o n s o f the s l a g s were s u p p l i e d by Cominco. ro cn 26 above, an e x p e r i m e n t a l programme was f o r m u l a t e d to s t u d y the s l a g p r o p e r t i e s and then t o d e v e l o p a s l a g r e s i s t a n t r e f r a c t o r y c o a t i n g , i f p o s s i b l e . 1.8 O b j e c t i v e s o f t h i s I n v e s t i g a t i o n The o b j e c t i v e o f t h i s s t u d y i s t o d e v e l o p a s l a g -r e s i s t a n t r e f r a c t o r y m a t e r i a l to i n c r e a s e the l i f e o f the l i n i n g c u r r e n t l y b e i n g used i n Dore f u r n a c e s . In o r d e r to a c c o m p l i s h t h i s , the f o l l o w i n g r e s e a r c h i n v e s t i g a t i o n s were c o n d u c t e d : 1. P r o p e r t i e s o f Pore* s l a g s ( i ) m e l t i n g t e m p e r a t u r e s ( i i ) v i s c o s i t y ( i i i ) s u r f a c e t e n s i o n and melt d e n s i t y ( i v ) r e f r a c t o r y o x i d e and s l a g w e t t i n g p r o p e r t i e s (v) w e i g h t l o s s on h e a t i n g . 2. Development o f c o a t i n g c o m p o s i t i o n s and p r o p e r t i e s . 3. S l a g a t t a c k t e s t s on c o a t e d r e f r a c t o r i e s . When i t was o b s e r v e d t h a t s i m p l y c o a t i n g r e f r a c -t o r i e s d i d not a d e q u a t e l y p r e v e n t s l a g a t t a c k , the f o l l o w -i n g a d d i t i o n a l i n v e s t i g a t i o n s were c o n d u c t e d : Impregnation of r e f r a c t o r y b r i c k s by oxides s a l t s . Slag attack t e s t s on impregnated and coated r e f r a c t o r i e s . 28 C h a p t e r 2 2. EXPERIMENTAL PROCEDURES AND RESULTS 2.1 M a t e r i a l s S t u d i e d In the e x p e r i m e n t a l programme - the p r o p e r t i e s o f the s l a g s were s t u d i e d f i r s t . Then c o a t i n g m i x t u r e s were d e v e l o p e d and t e s t e d on a s u i t a b l e r e f r a c t o r y . F i n a l l y , m o d i f i c a t i o n s o f c o a t i n g m a t e r i a l s and t e c h n i q u e s f o r i m p r e g n a t i o n were d e v e l o p e d . In t h i s c h a p t e r o n l y s l a g p r o p e r t i e s a r e d i s c u s s e d . B e f o r e t h i s work was s t a r t e d , the o n l y known s l a g p r o p e r t y was c h e m i c a l c o m p o s i t i o n , which was d e t e r m i n e d by Cominco L t d . 2.2 S l a g P r o p e r t i e s The s l a g p r o p e r t i e s r e q u i r e d f o r d e v e l o p i n g a c o a t i n g a r e as f o l l o w s : (a) Chemical c o m p o s i t i o n (b) P h y s i c a l P r o p e r t i e s ( c ) S l a g - o x i d e R e a c t i o n s 2.2.1 Chemical P r o p e r t i e s The a t o m i c c o m p o s i t i o n o f the s l a g s and t h e phases 29 p r e s e n t i n quenched s l a g s , d e t e r m i n e d by x - r a y d i f f r a c t i o n a n a l y s i s , are o u t l i n e d below: 2.2.2 Chemical C o m p o s i t i o n The c h e m i c a l c o m p o s i t i o n o f v a r i o u s s l a g s a r e shown i n T a b l e L U . These s l a g s a r e r i c h i n l e a d , bismuth and antimony. The p r e s e n t s t u d y was done on s l a g s CI, C2, C3 and C4 which were o b t a i n e d from Cominco's Dore f u r n a c e s . As d i s c u s s e d e a r l i e r : ( s e c t i o n 1.2 and T a b l e I I ) , s l a g 'B' i s the most c o r r o s i v e o f a l l s l a g s a t 1080°C. Some p r e -l i m i n a r y t e s t s w i t h s l a g b u t t o n s ( d i s c u s s e d l a t e r ) showed t h a t s l a g C4 was the most ' r e f r a c t o r y - p e n e t r a t i n g ' o f the f o u r ' C - s l a g s ' . S l a g B and s l a g C4 a r e the c l o s e s t i n c h e m i c a l c o m p o s i t i o n . So a l t h o u g h a l l the ' C - s l a g s ' were i n v e s t i g a t e d an added emphasis was g i v e n to s l a g C4. 2.2.3 S l a g S t r u c t u r e The d i f f e r e n t phases p r e s e n t i n the s l a g were found by the x - r a y d i f f r a c t i o n method as mentioned b e f o r e . The s t u d i e s were c o n d u c t e d on ' a s - r e c e i v e d ' s l a g s . The s l a g s were ground to a f i n e powder (about -325 mesh), as r e q u i r e d f o r p o w d e r - d i f f r a c t i o n p a t t e r n d e t e r m i n a -2 2 t i o n . For the d i f f r a c t i o n p a t t e r n s Cu Ka r a d i a t i o n w i t h 30 a n i c k e l f i l t e r was used. The phases i d e n t i f i e d i n s l a g s CI , C2, C3 and 04 a r e l i s t e d i n T a b l e IV. The o n l y ' f r e e ' o x i d e s i n the s l a g s a r e P b , ^ , PbO, B i and Cu,,0. The p r e s e n c e o f some amorphous phases was i n d i c a t e d by the e x i s t e n c e o f a broad band (hump) between 26° and 34° (2 e a n g l e e s p e c i a l l y i n the case o f s l a g C4). 2.2.4 P h y s i c a l P r o p e r t i e s The p h y s i c a l p r o p e r t i e s o f the s l a g s , t h a t were d e t e r m i n e d , a r e l i s t e d below. The e x p e r i m e n t a l p r o c e d u r e s and the r e s u l t s a r e g i v e n i n each s e c t i o n . (a) M e l t i n g p o i n t (b) V i s c o s i t y (c) S u r f a c e t e n s i o n and m e l t d e n s i t y (d) C o n t a c t a n g l e (e) Weight l o s s a t e l e v a t e d t e m p e r a t u r e s . 2.2.4.1 M e l t i n g P o i n t D e t e r m i n a t i o n (a) E x p e r i m e n t a l P r o c e d u r e : The l i q u i d u s t e m p e r a t u r e o f the s l a g s was d e t e r -mined u s i n g the D i f f e r e n t i a l Thermal A n a l y s i s (DTA) method. A c o m m e r c i a l l y a v a i l a b l e DuPont 1090 Thermal A n a l y z e r was used a l o n g w i t h a 1200 (°C) DTA f u r n a c e module. 31 T a b l e IV Phases I d e n t i f i e d i n Dore S l a g s S l a g CI: P b 2 ° 3 a n d s o m e P b-y S b 2 - x ° 7 ( B i n d h e i m i t e ; 2<y*3, 0<x<l) S l a g C2: B i A s 0 4 > P b 2 S b 2 G"7 and some (Sb, A s ) 2 0 3 and B i 2 4 P b 2 °40 S l a g C3: PbO S l a g C4: P b 2 ° 3 ' P b S b 2 0 4 .and BT 20 3(B) 32 To e n s u r e homogeneity o f s l a g samples, a few chunks o f a s l a g were m i l l e d to a f i n e powder w i t h s t e e l b a l l s . The powder was then mixed t h o r o u g h l y f o r 24 h r s . i n a ' t u m b l i n g - u n i t ' . T h i s w ' a s t o e n s u r e t h a t the "micro sample" used i n the DTA, a p p r o x i m a t e l y 0.025 grams, was r e p r e s e n t a t i v e o f the b u l k s l a g . A c o n t r o l l e d h e a t i n g r a t e o f 15°C/min. was used, and the f u r n a c e was purged w i t h N i t r o g e n gas w i t h a f l o w 3 r a t e o f about 50 cm /min. The DTA p l o t s f o r the f o u r s l a g s r e c o r d e d by the 1090 Thermal A n a l y z e r u n i t a r e shown i n F i g . 6. The o r d i n a t e i n t h i s c ase i n d i c a t e s the t e m p e r a t u r e d i f f e r e n c e ( A T ) between the s t a n d a r d sample (Alumina powder) and the specimen ( s l a g ) . In a t y p i c a l DTA e x p e r i m e n t the s t a n d a r d cup i s p l a c e d on the r i g h t and the sample on the l e f t . With such an arrangement an e n d o t h e r m i c r e a c t i o n i s r e p r e s e n t e d by a drop on the DTA p l o t and an e x o t h e r m i c r e a c t i o n by a peak. In the case o f ' g l a s s y ' m a t e r i a l s (amorphous) the peaks a r e much b r o a d e r than the peaks a s s o c i a t e d w i t h c r y s t a l l i n e m a t e r i a l s . T h i s o c c u r s because the s o f t e n i n g and m e l t i n g i n g l a s s y m a t e r i a l s a r e q u i t e s l u g g i s h and o c c u r o v e r a range o f t e m p e r a t u r e s . The s i z e o f the e n d o t h e r m i c o r e x o t h e r m i c peak g i v e s an a p p r o x i m a t e 33 I i i i i i i i 1 1 i . 1 0 200 400 600 800 1000 Temperature (°C ) F i g . 6 M e l t i n g Temperatures o f Dore S l a g s . 34 i d e a r e g a r d i n g the amount o f m a t e r i a l u n d e r g o i n g the thermal t r a n s f o r m a t i on. (b) R e s u l t s : The l i q u i d u s t e m p e r a t u r e s of s l a g s C I , C2, C3 and C4 are l i s t e d i n T a b l e V. The m e l t i n g t e m p e r a t u r e s of s l a g s are not t r u e m e l t i n g p o i n t s but r a t h e r l i q u i d u s t e m p e r a t u r e s of the d i f f e r e n t phases t h a t e x i s t i n a complex s l a g system. I t i s a l s o a p p a r e n t t h a t the s l a g s don't have j u s t one l i q u i d u s t e m p e r a t u r e but two o r more depending on the system (see F i g . 6 ) . The f r e e o x i d e s t h a t were i d e n t i f i e d i n t h e s e s l a g s by x - r a y d i f f r a c t i o n ( T a b l e IV) d i d not m e l t as s i n g l e o x i d e s but r a t h e r r e a c t e d i n a b i n a r y or t e r n a r y f a s h i o n w i t h o t h e r o x i d e s ; t h i s c o u l d e x p l a i n the absence o f f r e e -o x i d e m e l t i n g p o i n t s as i n d i c a t e d i n the DTA p l o t s . From T a b l e V i t can be noted t h a t s l a g C3 has the h i g h e s t l i q u i d u s t e m p e r a t u r e ; t h i s may be due to i t s h i g h PbO c o n t e n t (82.7 w t . % ) . In the case o f C I , C2 and C4 t h e r e are o t h e r low m e l t i n g p o i n t o x i d e s l i k e Bi^O^ ( 8 1 7 ° C ) , S b 2 n 3 ( 6 5 5 ° C ) , S b 2 0 5 ( 3 8 0 ° C ) , e t c . which may produce low-t e m p e r a t u r e l i q u i d u s and e u t e c t i c s . As e x p e c t e d , s l a g C4 has the l o w e s t l i q u i d u s tempera-t u r e - 525°C. T h i s e x p l a i n s t h e f l u i d i t y and r e f r a c t o r y -p e n e t r a t i n g a b i l i t y o f t h i s s l a g at 1080°C (the Dore f u r n a c e 35 T a b l e V Mel t i n g P o i n t o f Dore S l a g s . S l a g M e l t i n g P o i n t (°C) CI 540 C2 670 C3 710 C4 515 36 t e m p e r a t u r e ; - a. t e m p e r a t u r e a l m o s t 550°C above i t s ' m e l t i n g point'). The b i n a r y e u t e c t i c s o f the s l a g components are g i v e n i n T a b l e VI. T a b l e VI PbO-Oxide E u t e c t i c s System Lowest E u t e c t i c T(°C) PbO- A s 2 0 5 <800 Cu 20 680 " B i 2 ° 3 ^750 " S b 2 ° 3 540 - s b 2 o 5 820 - S i 0 2 715 From the DTA pi o t s ji n' Fej g .6 , and T a b l e V I , i t can be seen t h a t some o f the peaks c o r r e s p o n d to the l o w e s t e u t e c t i c s i n the b i n a r y systems. PbO i s t h e major c o n s t i t u e n t i n t h e s e s l a g s , so o n l y PbO b i n a r i e s were c o n s i d e r e d . 2.2.4.2 V i s c o s i t y o f S l a g s (a) I n t r o d u c t i o n The v i s c o s i t y o f a l l l i q u i d s and most s l a g s f o l l o w an A r r h e n i u s t y p e r e l a t i o n s h i p w i t h t e m p e r a t u r e as g i v e n by the r e l a t i o n 3 7 a s A 1 exp (En./RT) 2.1 where, n. ~ v i s c o s i t y o f the l i q u i d , A-j = a c o n s t a n t , E^ = a c t i v a t i o n energy f o r v i s c o u s f l o w , R = gas c o n s t a n t and T = t e m p e r a t u r e i n K. A d e t a i l e d d i s c u s s i o n r e g a r d i n g the development of the above e q u a t i o n i s g i v e n i n Appendix 1. (b) A p p a r a t u s S e v e r a l methods are a v a i l a b l e f o r the measurement of s l a g v i s c o s i t y . In the p r e s e n t i n v e s t i g a t i o n a c o n c e n -t r i c c y l i n d e r v i s c o m e t e r was used b e c a u s e : 1. A c o n v e n t i o n a l B r o o k f i e l d v i s c o m e t e r was a v a i l a b l e 2'. The r e l a t i v e l y s m a l l i s o t h e r m a l zone r e q u i r e d f o r such v i s c o m e t e r s 3. The ease o f o p e r a t i o n 4. The h i g h l y c o r r o s i v e n a t u r e o f the molten s l a g . Other methods used f o r m e a s u r i n g v i s c o s i t y i n c l u d e : ( i ) the f a l l i n g body method ( i i ) v i s c o u s f l o w i n c a p i l l a r i e s ( i i i ) the l o g a r i t h m i c decrement method (.using a disc» spher e o r a c r u c i b l e ) . ( i v ) the cone and p l a t e method. Most o f t h e s e methods are 38 s u c c e s s f u l when used f o r l i q u i d s a t room'temperature but molten s l a g s pose s e v e r a l r e s t r i c t i o n s a t high, t e m p e r a t u r e s (>1000°C) l i m i t i n g the use o f the above methods. The con-c e n t r i c c y l i n d e r method i s the most w i d e l y used t e c h n i q u e 23 f o r m e a s u r i n g s l a g - m e l t v i s c o s i t i e s . M i c h e l , D avies and 24 25 26 W r i g h t , Kato and Minowa, and B o c k r i s and Lowe have used the c o n c e n t r i c c y l i n d e r v i s c o m e t r i c method f o r the measurement o f molten s l a g s and g l a s s . There a r e two v a r i a n t s o f the c o n c e n t r i c c y l i n d e r method, one i n which the o u t e r c y l i n d e r ( t h e c r u c i b l e ) i s s t a t i o n a r y and the i n n e r c y l i n d e r (.-the s p i n d l e ) r o t a t e s , and the o t h e r where t h e o u t e r c y l i n d e r r o t a t e s and the i n n e r one remains s t a t i o n a r y . The f o r m e r method i s used i n com-m e r c i a l v i s c o m e t e r s and the l a t t e r i s used i n s p e c i a l cases where a l a r g e range o f s h e a r r a t e s are r e q u i r e d . An a p p a r a t u s was d e s i g n e d and f a b r i c a t e d to measure the s l a g v i s c o s i t y i n t h i s i n v e s t i g a t i o n . The a p p a r a t u s can be d i v i d e d i n t o the f o l l o w i n g p a r t s : ( i ) V i s c o m e t e r , ( i i ) C r u c i b l e and s p i n d l e , ( i i i ) F u r n a c e , and ( i v ) C r u c i b l e r a i s i n g d e v i c e . A s c h e m a t i c diagram o f the a p p a r a t u s i s ; shown i n F i g . 7. The i m p o r t a n t d e s i g n a s p e c t s o f the f o u r p a r t s a r e d i s c u s s e d b r i e f l y : ( i ) A B r o o k f i e l d S y n c h r o - L e c t r i c v i s c o m e t e r was used. However, the m e t a l l i c s p i n d l e s o f t h i s v i s c o m e t e r c o u l d not Brookfield Viscometer F i g . 7 Schematic View of the V i s c o s i t y - M e a s u r i n g A p p a r a t u s . 40 be used f o r the p r e s e n t purpose as the s l a g e a s i l y a t t a c k e d them. ( i i ) The b i g g e s t problem f a c e d i n measuring the v i s c o s i t y o f Dore s l a g s was the s e l e c t i o n o f a p r o p e r r e f r a c t o r y m a t e r i a l f o r the c r u c i b l e and the s p i n d l e . P l a t i n u m or molybdenum c r u c i b l e s a r e used f o r most purp o s e s ( C a F 2 m e l t s , C a O - A l 2 0 3 - S i 0 2 s l a g s , and g l a s s ) but t h e s e can not be used i n t h i s s t u d y as the s l a g " a t t a c k e d " both m e t a l s . R e f r a c -t o r y o x i d e s were chosen as c r u c i b l e and s p i n d l e m a t e r i a l s . M u T l i t e showed p r o m i s i n g s 1 a g - r e s i s t a n t q u a l i t i e s but dense alumina 1 was found t o be the b e s t m a t e r i a l . The c r u c i b l e s were made by s l i p - c a s t i n g a c o m m e r c i a l , c a s t a b l e a l u m i n a powder ( A l c o a - A 1 7 ) and then s u b s e q u e n t l y f i r i n g the green c r u c i b l e s i n a gas f i r e d f u r n a c e a t 1700°C f o r 5 h r s . These a l u m i n a c r u c i b l e s were a l m o s t 100% dense and c o n s e q u e n t l y non-porous. The s p i n d l e s were i n the shape o f rods w i t h an o u t e r d i a m e t e r o f 1.30 cms and were o b t a i n e d c o m m e r c i a l l y . These A 1 2 0 3 s p i n d l e s were a t t a c h e d t o s t a i n l e s s s t e e l tubes w i t h about 10 cms o f the s p i n d l e p r o j e c t i n g out o f the t u b e s . The s t a i n l e s s tubes were then a t t a c h e d t o t h e v i s -cometer. A p i e c e of s t r a i g h t p l a t i n u m w i r e was f i x e d on the al u m i n a s p i n d l e 4 cms from the bottom ( t h i s was the p r e -d e t e r m i n e d immersion depth o f the s p i n d l e ) u s i n g s t a i n l e s s s t e e l clamps. A n o t h e r p l a t i n u m w i r e was immersed i n the m e l t . When the alu m i n a s p i n d l e was immersed to the c o r r e c t d e p t h , the e l e c t r i c a l c i r c u i t between the two p l a t i n u m w i r e s and the molten s l a g was c o m p l e t e d . C i r c u i t c o m p l e t i o n was i n d i c a t e d by a z e r o r e s i s t a n c e measurement on an ohm-meter. The c r u c i b l e s were 7.0 cms h i g h , 4.6 ems o u t e r d i a -meter and 0.2 cm w a l l t h i c k n e s s . ( i i i ) A s c h e m a t i c drawing o f the f u r n a c e can be seen i n F i g . 8. The f u r n a c e had a type 2712-KSP Ka n t h a l h e a t i n g element c a p a b l e o f g o i n g up to 1200°C. I t had an i n t e r n a l d i a m e t e r o f 6.03 cms (2 3/8 i n c h e s ) and a l e n g t h o f 30.48 cms (12 i n c h e s ) . Alumina-wool i n s u l a t i o n was wrapped around the f u r n a c e ; the i n s u l a t i o n had a t h i c k n e s s o f 3.80 cms (9.65 i n c h e s ) . In the c o r e o f the f u r n a c e , a dense alumina tube o f l e n g t h 36 cms and an o u t e r d i a m e t e r o f 5.72 cms (5.01 cms i n n e r d i a m e t e r ) was p l a c e d . The i s o t h e r m a l zone i n the f u r n a c e was about 5.00 cms and the l e n g t h o f the c r u c i b l e was 6.00 ems but the s l a g h e i g h t ( m o l t e n ) i n the c r u c i b l e was about 5.00 ems. The c r u c i b l e (4.50 cms O.D. and 4.20 ems I.D.) was s u p p o r t e d i n the f u r n a c e by an A I 2 O 3 -rod which r e s t e d on the r a i s i n g d e v i c e - a l a b o r a t o r y j a c k . The t e m p e r a t u r e o f the i s o t h e r m a l zone c o u l d be con-t r o l l e d w i t h i n + 5°C. ( i v ) The r a i s i n g d e v i c e was an o r d i n a r y l a b o r a t o r y j a c k to which a v e r n i e r d e v i c e was f i x e d . T h i s was i n p l a c e o f the o r d i n a r y knob used f o r r a i s i n g o r l o w e r i n g the pi a t -form. The h o r i z o n t a l movement o f the ' t h r e a d e d screw' was Al e 0 9 Tube 8 S c h e m a t i c View o f t h e V e r t i c a 1 - F u r n a c e . g r a d u a t e d i n terms o f the v e r t i c a l movement o f the p l a t f o r m u s i n g a s t r a i n - g a u g e . The c r u c i b l e c o u l d be r a i s e d o r lowered w i t h an a c c u r a c y o f G.05 cm , u s i n g t h i s d e v i c e . (c) C a l i b r a t i o n The v i s c o m e t e r was c a l i b r a t e d u s i n g machine o i l s , g l y c e r i n e and c a s t o r o i l a t d i f f e r e n t t e m p e r a t u r e s . The v a l u e s o f v i s c o s i t i e s o f the l i q u i d s used f o r c a l i b r a t i o n were t a k e n from a s t a n d a r d handbook on the p h y s i c a l p r o -27 p e r t i e s of l i q u i d s . V i s c o s i t i e s o f t h e s e l i q u i d s were measured u s i n g the m o d i f i e d a l u m i n a s p i n d l e and the A l ^ O ^ c r u c i b l e on the ' 1 0 0 - s c a l e ' o f the v i s c o m e t e r . The c a l i -b r a t i o n p l o t f o r t h i s m o d i f i e d v i s c o m e t e r i s shown i n F i g . 2 8 9. T i e d e used a s i m i l a r method f o r c a l i b r a t i n g h i s B r o o k f i e l d v i s c o m e t e r which was used t o measure the v i s c o s -i t y of g l a s s . (d) E x p e r i m e n t a l The c r u c i b l e was f i l l e d w i t h about 450 gms. o f powdered s l a g and was i n t r o d u c e d i n t o the f u r n a c e from the bottom. The water c i r c u l a t i n g i n the top p l a t t e n kept i t c o o l which p r e v e n t e d the v i s c o m e t e r stem from g e t t i n g h o t . An u n s h e a t h e d , Pt-.P.t 13%. Rd t h e r m o c o u p l e was i n t r o d u c e d from t h e top i n t o the molten s l a g ( i n the c r u c i b l e ) and was used to r e c o r d the t e m p e r a t u r e . T h i n w a l l e d a l u m i n a t u b e s were t r i e d f o r s h e a t h i n g m a t e r i a l s but the s l a g 44 F i g . 9 C a l i b r a t i o n P l o t f o r t h e M o d i f i e d S p i n d l e . p e n e t r a t e d t h r o u g h the tubes e a s i l y ; t h i c k w a l l e d tubes c o u l d not be used as the thermal c o n d u c t i v i t y o f a l u m i n a i s q u i t e low and t h e time t a k e n f o r one r e a d i n g would be about one minute. On the o t h e r hand, unsheathed t h e r m o c o u p l e beads were found to l a s t f o r about one run (1.5 h r s . ) . The t h e r m o c o u p l e was not kept immersed i n the m e l t a l l the time. When the d e s i r e d t e m p e r a t u r e was r e a c h e d , the c r u c -i b l e was r a i s e d by the r a i s i n g d e v i c e u n t i l the p r e d e t e r -mined l e n g t h (4 cms) o f th e s p i n d l e was immersed i n t o the molten s l a g . The c o r r e c t l e v e l o f immersion was i n d i c a t e d by a z e r o r e s i s t a n c e o f f e r e d by the s l a g i n the e l e c t r i c a l c i r c u i t (2.2.4.2 ( i i ) ) . A f t e r the s p i n d l e was immersed, v i s c o m e t e r r e a d i n g s were t a k e n . A l l v i s c o s i t y measurements were done i n a i r d u r i n g the h e a t i n g c y c l e . The h e a t i n g c y c l e was chosen i n s t e a d o f the c o o l i n g c y c l e as the t e m p e r a t u r e c o n t r o l i n the h e a t i n g c y c l e was much e a s i e r . To e s t a b l i s h the v i s c o s i t y - t e m p e r a -t u r e p l o t s f o r the s l a g s , a t l e a s t t h r e e runs were performed on each s l a g . The v i s c o s i t y measurements were a l s o p e r -formed a t o t h e r speeds (50 and 20 rpro) and the measurements were found to agree w i t h the ones o b t a i n e d a t 100 rpm. (ei) R e s u l t s The r e s u l t s o f the v i s c o s i t y measurements ar e t a b u l a t e d i n Appendix l a and the average v i s c o s i t y v a l u e s are p l o t t e d a g a i n s t t e m p e r a t u r e i n F i g s . 10a and 10b. A l l the measurements were o b t a i n e d between 750°C and 1050°C ex-c e p t f o r s l a g C3 where the measurements were s t a r t e d a t 800°C. The measurements o b t a i n e d f o r s l a g C3 a t 750°C a r e not l i k e l y to be a c c u r a t e as the s l a g was "seedy" or " " g r a i ny." A 'seedy' molten s l a g l i k e C3 was a l s o e n c o u n t e r e d 2 8 by T i e d e , f o r some g l a s s e s . Subsequent v i s c o s i t y measure ments, o b t a i n e d o v e r s m a l l e r t e m p e r a t u r e i n t e r v a l s d e v i a t e d from the r e s u l t s g i v e n i n F i g . 10. There was f r o t h i n g o f s l a g s o v e r a narrow t e m p e r a t u r e range e s p e c i a l l y i n the case o f s l a g C4. D u r i n g f n o t h i n g , t h e v i s c o s i t y s u d d e n l y i n c r e a s e s to a h i g h e r v a l u e and then drops q u i c k l y . T h i s phenomenon can be seen i n F i g . 11. A s i m i l a r f r o t h i n g e f f e c t took p l a c e i n the case o f s l a g s CI and C2 but the degree o f f r o t h i n g (measured by the sudden i n c r e a s e i n v i s c o s i t y ) was much l e s s . In F i g . 10 t h i s sudden i n c r e a s e i n v i s c o s i t y i s not shown f o r two r e a s o n s : ( i ) when e x p e r i ments were f i r s t p e r f ormed - the r e a d i ngs i<n F i gs. 10a and 10b, t h i s e f f e c t was not n o t i c e d as no e x p e r i m e n t s were per formed between 895°C and 910°C, ( i i ) i f t h i s e r r a t i c be-h a v i o u r i s e x c l u d e d , the p l o t assumes the normal form as shown i n F i g . 10. Temperature ( °C) F i g . TOa V i s c o s i t y of Dore S l a g s . Temperature ( °C ) 1050 1000 950 900 850 800 750 n 1 1 1 1 1 r-T " ' x | 0 4 (K"') F i g . 1 0& N o r m a l i z e d V i s c o s i t y P l o t o f Dore S l a g s . 49 i 1 1 1 1 1 1 r CM 0 6 6 6 0 6 6 0 6 1 1 1 1 1 1 1 1 1 ( j . w s N u ! ) A j j soDS jA 601 2.2.4.3 S u r f a c e T e n s i o n and M e l t D e n s i t y 50 The m e l t - d e n s i t y and the s u r f a c e t e n s i o n measure-ments, o f the s l a g s were combined as t h e same a p p a r a t u s and t e c h n i q u e c o u l d be used f o r both measurements. For t h i s r e a s o n t h e s e c t i o n s on 'Ap p a r a t u s ' and ' E x p e r i m e n t a l P r o c e d u r e ' are combined;' whiTe the?'1 i n t r o d u c t i o n ' and ' r e s u l t s ' s e c t i o n s a r e kept s e p a r a t e . There a r e s e v e r a l methods a v a i l a b l e f o r mea s u r i n g the s u r f a c e t e n s i o n o f l i q u i d s ; c a p i l l a r y r i s e , drop w e i g h t , f i l m b a l a n c e , s e s s i l e drop and maximum bubble p r e s s u r e . Most o f t h e s e methods c a n ' t be used f o r molten s l a g s , and i n f a c t , most o f the s u r f a c e t e n s i o n measurements on s l a g s have been done by u s i n g o n l y f o u r methods: ( i ) maximum bubble p r e s s u r e , ( i i ) s e s s i l e d r o p , ( i i i ) pendant drop and ( i v ) c a p i l l a r y r i s e . In the p a s t few y e a r s the maximum bubble p r e s s u r e method has been used more o f t e n than the ... 29-34 o t h e r s . In the f o l l o w i n g s e c t i o n s the adva n t a g e s and d i s -a d v a n t a g e s o f d i f f e r e n t methods a r e d i s c u s s e d . ( i ) The s e s s i l e drop method i n v o l v e s the use o f a h i g h 35 t e m p e r a t u r e m i c r o s c o p e . Kojima used t h i s method t o de t e r m i n e the s u r f a c e t e n s i o n o f C a 0 - S i 0 2 and C a O - S i O ^ - A l 2 ° 3 s l a g s c o n t a i n i n g s u l p h u r . In t h i s method a s m a l l s o l i d 51 sample ( a b o u t 0.6 cm ) i s p l a c e d on an i n e r t s u b s t r a t e . The sample i s then h e a t e d i n a f u r n a c e . P i c t u r e s o f the drop formed at d i f f e r e n t t e m p e r a t u r e s a r e then t a k e n . The maxi-mum h e i g h t and the maximum r a d i u s are d e t e r m i n e d from the p i c t u r e s and the s u r f a c e t e n s i o n i s c a l c u l a t e d u s i n g the t a b l e s o f B a s h f o r t h and Adams. The d i m e n s i o n a l measure-ments have to be pe r f o r m e d a c c u r a t e l y i n o r d e r t o a v o i d l a r g e e r r o r s i n c a l c u l a t i n g the s u r f a c e t e n s i o n . In the p r e s e n t work t h i s method was not used t o measure the s u r f a c e t e n s i o n o f Dore s l a g s because a h i g h t e m p e r a t u r e m i c r o s c o p e was not a v a i l a b l e and the c o n s t r u c -t i o n o f one would be v e r y time consuming. ( i i ) The pendant-drop t e c h n i q u e has been used by Rasmussen 3 7 38 and N e l s o n and K i n g e r y to d e t e r m i n e the s u r f a c e t e n s i o n o f molten AlgOg. T h i s t e c h n i q u e c o u l d not be used i n the p r e s e n t case a l s o due to the n o n - a v a i l a b i l i t y o f a h i g h t e m p e r a t u r e m i c r o s c o p e . ( i i i ) The c a p i l l a r y r i s e method i s one o f the e a s i e s t and most p r a c t i c a l o f a l l methods when used to measure s u r f a c e t e n s i o n o f l i q u i d s a t room t e m p e r a t u r e . But t h i s i s not so i n the case o f Dore s l a g s ; here t h e c a p i l l a r y tube c o u l d not be made o f o p t i c a l l y t r a n s p a r e n t g l a s s . 52 r e f r a c t o r y o x i d e s , p l a t i n u m o r molybdenum as t h e s l a g s were v e r y r e a c t i v e . The c a p i l l a r y r i s e m ethod i s p e r h a p s t h e o l d e s t method f o r m e a s u r i n g t h e s u r f a c e t e n s i o n o f l i q u i d s -g o i n g b a c k t o t h e d a y s o f L e o n a r d o da V i n c i . When a v e r t i c a l c a p i l l a r y ( F i g . 12) i s p a r t l y immersed i n a l i q u i d w h i c h wets t h e c a p i l l a r y w a l l s p e r f e c t l y , t h e h e i g h t o f r i s e o f t h e l i q u i d i n t h e t u b e i s g i v e n by t h e e q u a t i o n h = 2 .2 where r i s t h e r a d i u s o f t h e t u b e and p i s t h e d e n s i t y o f t h e l i q u i d y and g have t h e i r u s u a l m e a n i n g s . The use o f t h e a b o v e e q u a t i o n ( 2 . 2 ) i s however v e r y l i m i t e d i n p r a c t i c e due t o t h e f a c t t h a t no l i q u i d c a n wet any c a p i l l a r y t u b e p e r f e c t l y . C o r r e c t i o n s have t o be made f o r c o n t a c t a n g l e s . A s i m p l e r f o r m f o r m e a s u r i n g l i q u i d s u r f a c e t e n s i o n i s t h e ' D i f f e r e n t i a l C a p i l l a r y R i s e ' m e t h o d . In t h i s method two t u b e s o f d i f f e r e n t d i a m e t e r s a r e p a r t i a l l y immersed i n t h e l i q u i d F i g . 13. The h e i g h t d i f f e r e n c e between t h e two l o w e r m e n i s c i i i s f o u n d and t h e n t h e s u r f a c e t e n s i o n 39 c a l c u l a t e d by u s i n g t h e method d e y e l o p e d by S u g d e n . 12 C a p i l l a r y R i s e i n a Tube, 13 D i f f e r e n t i a l C a p i l l a r y R i s e i n Tubes. 54 In the p r e s e n t work the d i f f e r e n t i a l c a p i l l a r y r i s e method was t r i e d w i t h o u t s u c c e s s due t o the s l a g g i n g r e a c -t i o n between the c a p i l l a r y tube used ( A l ^ 0 ^ ) and the s l a g s . 40 Wanibe e t a l . a l s o o b s e r v e d s l a g g i n g r e a c t i o n s i n the case o f FepQo,* CaO, S i ^ and A ^ O g s l a g s w i t h m u l l i t e c a p i l -l a r i e s . Such a s l a g g i n g r e a c t i o n g i v e s r i s e t o a t r a n s i e n t s u r f a c e t e n s i o n v a l u e . Due to t h e s e problems both the c a p i l l a r y r i s e and the d i f f e r e n t i a l c a p i l l a r y r i s e methods were r e j e c t e d . However, a few e x p e r i m e n t s were performed u s i n g the D i f f e r e n t i a l R i s e method b e f o r e coming to the above con-c l u s i o n . I t was found t h a t t h e s l a g r i s e i n the c a p i l l a r y t ubes depended on t i m e . The d i f f e r e n t amounts o f s l a g r i s e i n such c a p i l l a r i e s a t d i f f e r e n t time l e n g t h s can be seen i n F i g . 14. So c a p i l l a r y r i s e methods a r e s e r i o u s l y a f f e c t e d .by time : and , t h e s e methods can be used o n l y when t h e l i q u i d r i s e i n the c a p i l l a r i e s has r e a c h e d a s t a b l e and maximum h e i g h t v e r y q u i c k l y . ( i v ) The o n l y method found to be s u i t a b l e f o r m e a s u r i n g the s u r f a c e t e n s i o n o f Dore s l a g s was the maximum b u b b l e 29 p r e s s u r e method. T h i s method has been used by Hara e t a l . 31 f o r the CaO-CaF^-S'iO^ s y s t e m . Cooper and K i t c h e n e r f o r 30 the C a O - S i O 2 - P 2 O 5 system and G u n j i and Dan f o r the C a 0 - S i 0 2 - A l 2 ° 3 system and a l s o by.-others . 4 1 ~ 4 3 55 F i g . 14 I n c r e a s e o f c a p i l l a r y r i s e o f s l a g s i n a l u m i n a t u b e s w i t h t i m e . Time f r o m 1 t o r ( i ) 30 s e e s , ( i i ) 60 s e e s a n d ( i i i ) 2 m i n s . 56 In t h i s method a c a p i l l a r y tube i s d i p p e d i n t o the l i q u i d ( m e l t ) and an i n e r t gas ( N 2 o r Ar) i s pass e d t h r o u g h i t . When a s u f f i c i e n t l y h i g h p r e s s u r e i s a p p l i e d gas bub-b l e s break f r e e from the c a p i l l a r y t i p . By measuring the p r e s s u r e needed to break the b u b b l e s f r e e the s u r f a c e t e n -44 s i o n can be found by u s i n g S c h r o d i n g e r 1 s e q u a t i o n ; ,2 Y = 0.5 rg (Hp m-hp s) 1 2 r P i ( r p s ) ' 3(H P m-hp s) 6(Hp m-hp s)' 2-.3 where y = s u r f a c e t e n s i o n o f l i q u i d i n dyn.cm" r = r a d i u s o f c a p i l l a r y tube i n cm„ g = g r a v i t a t i o n a l c o n s t a n t i n cm sec H = maximum manometrie h e i g h t i n cm h = depth o f immersion i n cm P m = d e n s i t y o f manometrie l i q u i d i n gm cm p = d e n s i t y o f l i q u i d ( s l a g ) i n gm cm -3 The u n i q u e n e s s o f t h i s method l i e s i n the f a c t t h a t i t s use i s i n d e p e n d e n t o f the c a p i l l a r y - s l a g c o n t a c t a n g l e and t h e s l a g g i n g r e a c t i o n does not o c c u r as the s l a g can-not e n t e r the tu b e . The amount o f c o o l i n g i s a l s o v e r y s m a l l as the immersion depth can be kept s h o r t and l i t t l e time i s r e q u i r e d to p e r f o r m such an e x p e r i m e n t . 2.2.4.4 M e l t D e n s i t y The m e l t d e n s i t y o f a s l a g i s needed to c a l c u l a t e i t s 57 s u r f a c e t e n s i o n . The d e n s i t i e s o f l i q u i d s a t room tempera-t u r e ean be e a s i l y found by me a s u r i n g i t s weight and volume, but i n the case of molten s l a g s . t h i s becomes d i f f i c u l t because o f the h i g h t e m p e r a t u r e s i n v o l v e d . M e l t d e n s i t y i s u s u a l l y d e t e r m i n e d by ( i ) Archemedes p r i n c i p l e , ( i i ) the l e v e l o f r i s e o f the m e l t i n a p l a t i n u m tube and ( i i i ) t h e maximum bubble p r e s s u r e method. ( i ) The Archemedes Method T h i s method r e q u i r e s a z e r o c o n t a c t a n g l e between the body b e i n g immersed and the l i q u i d . I f t h e c o n t a c t VM a n g l e i s not z e r o then c o r r e c t i o n s have to be made, as the v e r t i c a l component o f the l i q u i d s u r f a c e t e n s i o n a f f e c t s the b a l a n c e between t h e w e i g h t o f t h e body b e i n g immersed and the upward t h r u s t b e i n g e x p e r i e n c e d by i t . T h i s method i s used f r e q u e n t l y to c a l c u l a t e d e n s i t i e s o f l i q u i d s w i t h o u t t a k i n g the c o n t a c t a n g l e i n t o c o n s i d e r a t i o n . However, the e f f e c t o f s u r f a c e t e n s i o n can be taken c a r e o f by com-p l e t e l y immersing two b o d i e s o f d i f f e r e n t w e i g h t s i n a l i q u i d and u s i n g the same s u s p e n s i o n w i r e . Here the s u r f a c e t e n s i o n e f f e c t s c a n c e l out - a method based on t h i s p r i n c i p l e 29 was used by Hara e t a.l.. to s t u d y the d e n s i t y o f Cap^-CaO-S i 0 2 m e l t s . In the above method t h e r e a r e t h r e e main r e s t r i c t i o n s : ( i ) the body b e i n g immersed s h o u l d be den s e r than the m e l t , (1.1) and 1 ow. 58 the s u s p e n s i o n w i r e s h o u l d not he a t t a c k e d by the melt, ( i i i ) the v i s c o s i t y o f the melt s h o u l d be r e a s o n a b l y I f the v i s c o s i t y o f the m e l t i s q u i t e h i g h ( i n r e l a t i v e terms) then the w e i g h t r e c o r d e d on immersing the body w i l l be more o f a t r a n s i e n t n a t u r e , as the body w i l l t ake a f i n i t e time t o become c o m p l e t e l y immersed. In the case o f s l a g s w i t h the f r o t h i n g t e n d e n c y (as i n the p r e s e n t case F i g . 11 and s e c t i o n 2.2.4.2) the v i s c o s i t y w i l l change a b r u p t l y d u r i n g f r o t h i n g and t h i s w i l l a f f e c t the weig h t r e c o r d i n g s . A s i m i l a r f r o t h i n g b e h a v i o u r was n o t i c e d 31 by Cooper and K i t c h e n e r i n the case o f CaO-Si 0 2-P 20,. m e l t s 45 and by S p e i t h and H e i n r i c h s i n the case o f F e 0 - S i 0 2 s l a g s . The b i g g e s t problem f a c e d i n u s i n g t h i s method i n the p r e s e n t c a s e was t h a t a s u i t a b l e s u s p e n s i o n w i r e c o u l d not be f o u n d . Even p l a t i n u m w i r e s a r e a t t a c k e d and d i s -s o l v e d by the Dore s l a g . C l e a r l y , the above method c o u l d not be a p p l i e d . Other, l e s s c r i t i c a l e x p e r i m e n t a l problems were a l s o e n c o u n t e r e d and the Archemedian method was f i n a l -l y r e j e c t e d . ( i i ) C a p i l l a r y R i s e Method The second method o f mea s u r i n g t h e m e l t - d e n s i t y o f s l a g s and o x i d e s i s by d i r e c t l y o b s e r v i n g i t s r i s e i n a tube. Rasmussen and N e l s o n u s e d t h i s method t o m e a s u r e t h e m e l t d e n s i t y o f A 1 2 ° 3 " I n t l r i s method a molybdenum t u b e w i t h one end s e a l e d i s u s e d ( a s molybdenum has a h i g h m e l t i n g p o i n t and does n o t r e a c t with. most o x i d e s ) . The o x i d e i s p u t i n s i d e t h e t u b e n o r m a l l y i n t h e f o r m o f c y l i n d r i c a l r o d s . The molybdenum t u b e i s t h e n h e a t e d i n a f u r n a c e ( w h i c h has a f a c i l i t y f o r x - r a y r a d i o g r a p h y ) and t h e l i q u i d m e n i s c u s r a d i o g r a p h i s f i l m e d . By t a k i n g i n t o a c c o u n t t h e volume e x p a n s i o n o f t h e t u b e - t h e volum e o f t h e l i q u i d and he n c e i t ' s d e n s i t y c a n be f o u n d . In p r i n c i p l e , t h i s method i s v e r y s i m p l e b u t t h i s m ethod c o u l d n o t be u s e d b e c a u s e a h i g h v o l t a g e ( a b o u t 300 kV) x - r a y s o u r c e , n e e d e d f o r s u c h r a d i o g r a p h y , was n o t a v a i l a b l e . ( i i i ) The maximum b u b b l e p r e s s u r e method has been u s e d by q u i t e a few w o r k e r s t o m e a s u r e t h e m e l t - d e n s i t y o f 46 s l a g s . P o p e l and E s i n u s e d t h i s method t o d e t e r m i n e t h e d e n s i t y o f F e 0 - S i 0 2 and C a 0 - F e 0 - S i 0 2 m e l t s , and G u n j i and Dan u s e d i t f o r t h e C a 0 - S i 0 2 and C a O - S i 0 2 - A l 2 0 3 s y s t e m s . In t h i s method t h e p r e s s u r e r e q u i r e d t o f o r m bub-! b l e s ( a t a ' s t a b l e maximum m a n o m e t r i e h e i g h t ' ) , a t two d i f -f e r e n t i m m e r s i o n h e i g h t s o f t h e c a p i l l a r y t u b e , i s m e a s u r e d 44 Then u s i n g S c h r o d i n g e r ' s e q u a t i o n (.2.3); t h e d e n s i t y o f 60 the melt can be f o u n d . p - 2>4. ( h 1 = h 2 ) where p i s the d e n s i t y o f the melt-, s P m i s the d e n s i t y o f the manometric l i q u i d (used to measure p r e s s u r e changes) H-| and H2 are the maximum manometric h e i g h t s a t depths o f immersion o f h^ and h 2 r e s p e c t i v e l y . The u n i q u e n e s s o f t h i s method l i e s i n the f a c t t h a t i t does not r e q u i r e c o n t a c t a n g l e s o r the s u r f a c e t e n s i o n of the m e l t . I t can a l s o be used f o r h i g h l y v i s c o u s m e l t s l i k e C a 0 - S i 0 2 and CaO-Si 0,,-Al . For the c o n v e n i e n c e o f u s i n g a s i n g l e t e c h n i q u e to measure both the s u r f a c e t e n -s i o n and m e l t d e n s i t y , a bubble p r e s s u r e a p p a r a t u s was con-s t r u c t e d f o r t h i s i n v e s t i g a t i o n . 2.2.4.5 E x p e r i m e n t a l P r o c e d u r e A p p a r a t u s The a p p a r a t u s t h a t was b u i l t f o r m e a s u r i n g the s u r -f a c e t e n s i o n and the m e l t d e n s i t y o f the Dore s l a g s i s shown s c h e m a t i c a l l y i n F i g . 15. The a p p a r a t u s c o n s i s t s o f s i x p a r t s : ( i ) gas p u r i f i c a t i o n t r a i n , . ( i i ) manometer, ( i i i ) v e r t i c a l f u r n a c e , ( i v ) c a p i l l a r y t u b e , ( v ] r a i s i n g -l o w e r i n g d e v i c e f o r t he c r u c i b l e and ( v i ) t h e bubble Tron»dueer F i g . 15 Apparatus Used f o r the Maximum Bubble P r e s s u r e Method. f r e q u e n c y m o n i t o r i n g system. 62 ( i ) The N i t r o g e n gas used f o r b u b b l i n g was p u r i f i e d by p a s s i n g i t t h r o u g h sodium h y d r o x i d e , c o p p e r f i l i n g s h e a t e d at 800°C and then t h r o u g h s i l i c a g e l . T h i s reduced the water and oxygen c o n t e n t o f the N i t r o g e n gas t o a v e r y low l i m i t . B e f o r e the N i t r o g e n gas was p a s s e d t h r o u g h t h e p u r i f i c a t i o n t r a i n , i t had a USP grade p u r i t y w i t h <30 ppm The b u b b l i n g r a t e was a c c u r a t e l y c o n t r o l l e d u s i n g a m i c r o - n e e d l e v a l v e . ( i i ) The manometer was made of a U-shaped g l a s s tube o f i n t e r n a l d i a m e t e r 0.6 cm and the l e n g t h o f each l i m b was about 60 cms. The manometer l i q u i d was water dyed r e d w i t h an o r g a n i c c o l o r a n t and i t s d e n s i t y a t room t e m p e r a t u r e (20°C) was 1.00 gm cm as measured by a p y c n o m e t r i c b o t t l e . L i q u i d l e v e l s i n the manometer were measured u s i n g a t r a v e l -l i n g t e l e s c o p e which was p l a c e d a t a d i s t a n c e o f 1.5 m from the manometer. ( i i i ) The f u r n a c e used f o r the s u r f a c e t e n s i o n and den-s i t y measurements was t h e same as the one used f o r t h e v i s c o s i t y measurements ( F i g . 8 ) . A l l the measurements were c a r r i e d out i n a i r . ( i v ) The c a p i l l a r y tube was made out of dense Al which had an i n t e r n a l d i a m e t e r o f 0.242 cm- These were the 63 o n l y tubes t h a t were i m m e d i a t e l y a v a i l a b l e . The tubes were about 46 ems l o n g . The tubes were mounted v e r t i c a l l y on a s t a n d , w i t h the a i d o f a p l u m b - l i n e , and then c o n n e c t e d to the p u r i f i e d gas f l o w . The o u t e r d i a m e t e r o f t h e s e tubes was 0.442 cm. A f t e r each measurement the c a p i l l a r y tubes were take n out and checked f o r p o s s i b l e s l a g a t t a c k but i n most c a s e s the tubes s u r v i v e d about 8 to 10 measure-ments w i t h o u t any s i g n i f i c a n t r e a c t i o n . (v) In most maximum bubble p r e s s u r e e x p e r i m e n t s , t h e c r u c i b l e i s n o r m a l l y f i x e d a t a c e r t a i n e l e v a t i o n and the c a p i l l a r y tube i s l o w e r e d i n t o the m e l t . In the p r e s e n t c a s e , due t o p r a c t i c a l p r o b l e m s , the c r u c i b l e was r a i s e d u s i n g the r a i s i n g - l o w e r i n g d e v i c e d i s c u s s e d p r e v i o u s l y . T h i s d e v i c e had an a c c u r a c y o f 0.05 cms. The c r u c i b l e was r a i s e d v e r y g e n t l y so as not to d i s t u r b the l i q u i d -s l a g s u r f a c e . ( v i ) The b u b b l i n g f r e q u e n c y i n f l u e n c e s the maximum manometrie h e i g h t . Very h i g h b u b b l i n g r a t e s l e a d to un-s t a b l e and r a p i d growth and break-away o f b u b b l e s . In a d d i t i o n , the i n e r t i a o f the manometrie l i q u i d p r e v e n t s i t from c h a n g i n g l e v e l s i n r e s p o n s e to h i g h f r e q u e n c y p r e s s u r e f l u c t u a t i o n s . The e f f e c t o f bubble f r e q u e n c y on the maximum manometrie h e i g h t was s t u d i e d u s i n g water p u r i f i e d by p a s s i n g i t t h r o u g h an i o n exchange r e s i n . The r e s u l t s a r e shown i n F i g . 16. When t e s t e d w i t h Dore s l a g m e l t s s i m i l a r r e s u l t s 64 F i g . 16 Dependence of the Maximum B u b b l i n g I n t e r v a l . Manometric H e i g h t on were a l s o o b t a i n e d . G u n j i and Dan a l s o found s i m i l a r r e s u l t s . I t can be seen from the above f i g u r e t h a t a bub-b l e f r e q u e n c y o f l e s s than 1 b u b b l e / m i n u t e i s n e c e s s a r y i n o r d e r to o b t a i n r e l i a b l e r e s u l t s . To m o n i t o r the bu b b l e f r e q u e n c y a P i e z o e l e c t r i c T r a n s d u c e r was a t t a c h e d to the c a p i l l a r y tube ( F i g . 15). The p r e s s u r e s i g n a l s from the t r a n s d u c e r were f e d to a 3-ehannel a m p l i f i e r . The s i g n a l s from the a m p l i f i e r were then f e d i n t o a Dual H i / L o e l e c -t r o n i c f i l t e r and the e l e c t r i c a l s i g n a l s were r e c o r d e d on a T e k t r o n i x O s c i l l o s c o p e w i t h a Time Base. U s i n g t h i s s e t -up bubble r a t e s of l e s s than 1 b u b b l e / m i n u t e c o u l d be measured. I t was f e l t however, t h a t a t r a n s d u c e r w i t h a lower p r e s s u r e r a t i n g would have been more s u i t a b l e f o r t h i s work as the use o f an o s c i l l o s c o p e to measure maximum mano-m e t r i c h e i g h t would make the p r o c e d u r e o f d e t e r m i n i n g mano-m e t r i c h e i g h t s much s i m p l e r . A t r a n s d u c e r w i t h a lower p r e s s u r e r a t i n g was not a v a i l a b l e and the e x i s t i n g t r a n s -ducer c o u l d not be used to measure the manometric h e i g h t s . T h i s i s because the t r a n s d u c e r had a r a t i n g o f 0 to 60 p s i g and the maximum manometric h e i g h t r e c o r d e d i n t h e s e measure-ments c o r r e s p o n d to about 0.15 p s i g . On the o t h e r hand, the f r e q u e n c y c o u l d be measured v e r y a c c u r a t e l y w i t h t h i s system. The e x p e r i m e n t a l p r o c e d u r e f o r mea s u r i n g the s u r f a c e 66 t e n s i o n and the d e n s i t y v a l u e s o f molten s l a g s was r e l a -t i v e l y s i m p l e . For s u r f a c e t e n s i o n measurements the c a p i l -l a r y was immersed to a c e r t a i n d e p t h , the bubble r a t e kept a t a f r e q u e n c y o f l e s s than 1 bu b b l e / m i n u t e and then the maximum manometrie h e i g h t was d e t e r m i n e d . For d e n s i t y measurements manometrie h e i g h t s were measured a t two d i f -f e r e n t depths o f immersion, as d i s c u s s e d e a r l i e r . 2.2.4.6 Re s u i t s and A n a l y s i s (a) S u r f a c e T e n s i o n The maximum manometrie h e i g h t was measured from the d i f f e r e n c e between the l i q u i d l e v e l s i n t h e two l i m b s o f the manometer. These v a l u e s were f e d i n t o e q u a t i o n ( 2 . 3 ) -and the v a l u e s o f y were computed. The v a l u e s o f the e x p e r i m e n t a l measurements and t h o s e o f the o t h e r p a r a m e t e r s i n e q u a t i o n ( 2 . 3 ) f o r the f o u r Dore f u r n a c e s l a g s ( C I , C2, C3 and C4) can be seen i n Appendix 2. The s u r f a c e t e n s i o n v a l u e s o f the s l a g s as a f u n c t i o n o f t e m p e r a t u r e a r e p l o t t e d i n F i g . 17. The low s u r f a c e t e n s i o n v a l u e s o f Dore s l a g s r e f l e c t i n d i r e c t l y t h e i r s p r e a d i n g b e h a v i o u r on r e f r a c t o r i e s . Y i s r e l a t e d t o the s p r e a d i n g c o e f f i c i e n t S by the e q u a t i o n S " Y l(1+COSQ) 2.5 where 8 i s the a n g l e o f c o n t a c t between the molten s l a g and the s u b s t r a t e . L9 68 When a pure l i q u i d i n e q u i l i b r i u m w i t h i t s own vapour i s h e a t e d , i t s t e m p e r a t u r e e v e n t u a l l y r e a c h e s the c r i t i c a l p o i n t o f the s u b s t a n c e , where t h e r e i s no d i f f e r e n c e between the l i q u i d and the vapour and no s u r f a c e t e n s i o n can e x i s t ; t h i s t e m p e r a t u r e i s c a l l e d the c r i t i c a l tempera-t u r e ( T c ) . In g e n e r a l the g r e a t e r the t e m p e r a t u r e d i f f e r -ence between the o p e r a t i n g t e m p e r a t u r e and the c r i t i c a l t e m p e r a t u r e , t h e g r e a t e r the s u r f a c e t e n s i o n v a l u e becomes. In some s l a g m e l t s t h e s u r f a c e t e n s i o n may not f o l l o w the b e h a v i o u r o f a pure l i q u i d , as some complex s l a g systems 41 d i s s o c i a t e on m e l t i n g . In the p r e s e n t c a s e , t h e s u r f a c e t e n s i o n o f the s l a g - m e l t s d e c r e a s e d l i n e a r l y w i t h i n c r e a s e , i n t e m p e r a t u r e ( F i g . 17). For q u i t e a number o f o x i d e s such a l i n e a r r e l a t i o n s h i p h o l d s t r u e w i t h i n t h e l i m i t s of e x p e r i m e n t a l e r r o r . * I t s h o u l d be mentioned here t h a t s u r f a c e t e n s i o n measurements were not p e r f o r m e d i n the narrow t e m p e r a t u r e r e g i o n ( a b o u t 15°C) where f r o t h i n g t a k e s p l a c e . I t was o b s e r v e d t h a t the manometrie l i q u i d behaved v e r y e r r a t i c a l l y d u r i n g f r o t h i n g ; such an e f f e c t was not r e p o r t e d by Cooper 31 and K i t c h e n e r who worked on foaming molten s i l i c a t e s . The e r r a t i c b e h a v i o u r o f t h e manometrie l i q u i d c o u l d pos-s i b l y a r i s e from the f o r m a t i o n and breakage o f b u b b l e s i n the f r o t h which a f f e c t bubble f o r m a t i o n and break-away a t the c a p i l l a r y t i p . D u r i n g t h e p e r i o d o f f r o t h i n g the 69 maximum manometric h e i g h t was somewhat lower than e x p e c t e d i m p l y i n g lower s u r f a c e t e n s i o n v a l u e s . T h i s e f f e c t i s i n 31 agreement w i t h the work o f Cooper and K i t c h e n e r . (b) D e n s i t y The d e n s i t y o f the s l a g s d e c r e a s e d w i t h i n c r e a s e i n t e m p e r a t u r e . T h i s r e l a t i o n s h i p can be seen i n F i g . 18. The e x p e r i m e n t a l v a l u e s r e c o r d e d a l o n g w i t h the o t h e r parameters i n e q u a t i o n (2.4) a r e g i v e n i n Appendix 2 f o r the f o u r d i f -f e r e n t s l a g s . The d e n s i t y o f a l i q u i d a f f e c t s i t s p h y s i c a l p r o p e r t i e s i n d i r e c t l y as the d e n s i t y parameter i s i n v o l v e d i n t h e i r d e t e r m i n a t i o n . 2.2.4.7 C o n t a c t Angle (a) I n t r o d u c t i o n The w e t t i n g and s p r e a d i n g c h a r a c t e r i s t i c s o f a l i q u i d on a s o l i d s u b s t r a t e can be d e t e r m i n e d by mea s u r i n g i t s s u r f a c e t e n s i o n and t h e c o n t a c t a n g l e t h a t i t makes w i t h the s o l i d . When a l i q u i d drop s i t s on a s o l i d s u b s t r a t e ( F i g . 19) i t makes an a n g l e 'e ' w i t h i t , t h i s a n g l e i s c a l l e d the C o n t a c t A n g l e ; s m a l l c o n t a c t a n g l e s imply e x t e n s i v e s u b s t r a t e w e t t i n g by the l i q u i d . From Young's e q u a t i o n and F i g . 19 Y S V = Y S L + Y L V Cos e 2.6 8 0 L 750 800 850 900 950 Temperature (°C) 1000 1050 F i g : 18 Density o{ Dore Slags; F i g . S u r f a c e T e n s i o n s A s s o c i a t e d w i t h a S e s s i l e D r o p . 72 and from e q u a t i o n (.2.6) S = T l v (GosQ+vl ) 2.5 i t can be seen t h a t the s u r f a c e t e n s i o n Cv^y) o f a l i q u i d and the c o n t a c t a n g l e i t makes w i t h a s o l i d s u b s t r a t e a r e i n t i m a t e l y l i n k e d . The s p r e a d i n g ( o r w e t t i n g ) o f a l i q u i d on a s o l i d i s d e t e r m i n e d both by the s u r f a c e t e n s i o n ( y ^ y ) and the c o n t a c t a n g l e ( e ) . There are many methods a v a i l a b l e f o r the measure-ment o f l i q u i d - s o l i d c o n t a c t a n g l e s . In t h e case o f m e t a l s and s l a g s t h e r e a r e two common methods ( i ) d i r e c t o b s e r v a -t i o n o f the c o n t a c t a n g l e by t a k i n g p i c t u r e s o f the molten drop a t e l e v a t e d t e m p e r a t u r e s and ( i i ) c a l c u l a t i n g the c o n t a c t a n g l e from the e q u i l i b r i u m d i m e n s i o n s ( h e i g h t and r a d i u s ) o f the drop. R e c e n t l y , P r a b r i p u t a l o o n g and P i g g o t 4 ' d e t e r m i n e d the c o n t a c t a n g l e s o f Al , Ag, Au, Cu, In and Sn on s a p p h i r e by t h e t h i n f i l m t e c h n i q u e . However i n the case o f s l a g s and metal o x i d e s the t h i n f i l m t e c h n i q u e may not prove v e r y h e l p f u l due to t h e h i g h b o i l i n g p o i n t s o f most o x i d e s . From F i g . 19 i t seems t h a t the t h e o r y and t h e e x p e r i m e n t a l p r o c e d u r e s f o r d e t e r m i n i n g the c o n t a c t a n g l e s are q u i t e s i m p l e but i n p r a c t i c e i t i s not so. The f a c t o r s 73 t h a t c o u l d a f f e c t the v a l u e s o f c o n t a c t a n g l e s between l i q u i d s and s o l i d s u b s t r a t e s a r e numerous. In t h i s s e c t i o n o n l y the i m p o r t a n t f a c t o r s w i l l be c o n s i d e r e d . S u r f a c e roughness o f the s o l i d s u b s t r a t e (assuming i t i s 100% dense) seems to a f f e c t c o n t a c t a n g l e v a l u e s the most. The s u r f a c e roughness i s g e n e r a l l y e x p r e s s e d i n terms o f the s u r f a c e roughness f a c t o r ' r ' . The term ' r ' i s the r a t i o o f the a c t u a l s u r f a c e a r e a o f the s o l i d sub-s t r a t e to i t s g e o m e t r i c a r e a (A : A. );• where t h e a c t u a l s u r f a c e a r e a i n c l u d e s t h e u n d u l a t i o n s p r e s e n t on the s u r -f a c e . I f the roughness f a c t o r i s i n c l u d e d i n Young's e q u a t i o n a f t e r r e a r r a n g e m e n t i t becomes: Y L V Cos e = r ( ' Y - S V - Y S L ) 2.7 So i t i s a p p a r e n t t h a t r can a f f e c t the v a l u e o f ev As an example the roughness f a c t o r o f ground g l a s s can v a r y be-tween 1.4 to 2.2 and the c o n t a c t a n g l e o f h i g h - a r o m a t i c t a r on p l a t e g l a s s can var y between 27° and 52°. Such l a r g e v a r i a t i o n s o f c o n t a c t a n g l e a r e due to the combined e f f e c t s o f s u r f a c e roughness and c o n t a c t a n g l e h y s t e r e s i s . The c o n t a c t a n g l e h y s t e r e s i s i s e x p l a i n e d by the a d v a n c i n g and r e c e d i n g c o n t a c t a n g l e phenomenon. 74 48 In 1935 Mack showed t h a t the use o f s m a l l drops f o r m e asuring c o n t a c t a n g l e s possesses; s e v e r a l a d v a n t a g e s : ( i ) s m a l l drops can be used on s m a l l p l a n e a r e a s o f an i r r e g u l a r s u r f a c e or on an a r e a w i t h an a p p r o x i m a t e l y con-s t a n t c u r v a t u r e , ( i i ) s m a l l drops have g r e a t e r v a r i a t i o n i n h e i g h t f o r s m a l l e r v a r i a t i o n s i n c o n t a c t a n g l e s and ( i i i ) s m a l l drops assume the a d v a n c i n g c o n t a c t a n g l e w h i l e l a r g e r drops e x h i b i t a f l u c t u a t i n g a n g l e which T i e s between the a d v a n c i n g and r e c e d i n g c o n t a c t a n g l e s . The a c u t e a n g l e o f c o n t a c t (0) i s g i v e n by: e = 2 t a n " 1 (h/x) 2,8 where h i s the g r e a t e s t h e i g h t o f the drop and x i s the r a d i u s o f t h e base ( F i g . 19). The d i s t a n c e x can be e a s i l y and a c c u r a t e l y measured as i t i s q u i t e l a r g e but the s m a l l magnitude of 'h' i n t r o d u c e s e r r o r s i n i t s measurement. T h i s i s e s p e c i a l l y t r u e f o r s m a l l d r o p s . In the case o f s m a l l drops t h e e v a p o r a t i o n i s q u i t e l a r g e , due to the l a c k o f e q u i l i b r i u m between the l i q u i d and the s u r r o u n d i n g vapour -t h i s a f f e c t s the v a l u e o f 'h'. The measurement o f 'h' can o n l y be done a c c u r a t e l y i n a h i g h t e m p e r a t u r e m i c r o s c o p e . These problems can be s o l v e d by s u b s t i t u t i n g the volume f o r the h e i g h t as a m e a s u r a b l e d i m e n s i o n o f the drop, 75 T h i s e l i m i n a t e s the problem o f e v a p o r a t i o n o f the l i q u i d . 48 Mack o b s e r v e d t h a t an e v a p o r a t i n g drop m a i n t a i n e d i t s o r i g i n a l r a d i u s l o n g a f t e r i t s h e i g h t , volume and c o n t a c t a n g l e had been c o n s i d e r a b l y r e d u c e d . When the c o n t a c t a n g l e , o f s m a l l drops i s a c u t e the shape o f t h e drop ean .be a p p r o x i m a t e d by a s p h e r o i d a l segment. The e q u a t i o n (2.8) mentioned e a r l i e r assumes such a shape but t h i s e q u a t i o n cannot be used s u c c e s s f u l l y f o r s m a l l drops when t h e v a l u e o f 'h' i s v e r y smal1. So, an e q u a t i o n was d e r i v e d i n terms o f the drop volume, u s i n g drop r a d i u s a t the base and the c o n t a c t a n g l e as pa r a m e t e r s * C o n s i d e r a s e s s i l e drop which i s a s p h e r o i d a l segment ( f l a t t e n i n g o f s e s s i l e drops i s d e a l t w i t h i n Appendix 3) s i t t i n g on a s o l i d s u b s t r a t e and making an a n g l e e w i t h i t a t i t s base ( F i g . 20a). The same drop can be i n c o r p o r a t e d i n a sphe r e as i n F i g . ( 2 0 b ) . The volume o f t h e s p h e r o i d a l segment ABC i s g i v e n by V c = ~ TT h 2 ( 3 r - h ) 2.9 where h =<B D and r-j - CD E q u a t i o n ( 2 . 9 ) can be f o u n d . i n any book .on M e n s u r a t i o n . From F i g . 20. b , h = r-| tan (.9/2) r l and t a n (e) = — ^ r^ + r tan (o) hence, h = t a n ( e l 2.10 76 F i g . 20 (a) Drop S e s s i l e Drop and (b) I n c o r p o r a t i o n o f i n ( a ) i n t o a R e p r e s e n t a t i v e C i r c l e . t h e 77 From t r i a n g l e ODC, and 2 , / u \ 2 2 r-j + ( r - h ) = r r^ + h 2.11 2h S u b s t i t u t i n g e q u a t i o n ( 2,. 1 2) i n t o C 2.9 ) y i e l d s V = c TT h ' 2.12 2.13 2.14 A f t e r s i m p l i f y i n g e q u a t i o n (2.14) Tf.hr, .Tr.tr 2.15 and s u b s t i t u t i n g f o r h i n e q u a t i o n (2.15) from (2.10) the f i n a l form o f the e q u a t i o n f o r V i s o b t a i n e d . V c = 1,5708 r ^ tan (e/2) + 0.5236 r ^ tan 3Ce/2) 2.16 From the above e q u a t i o n , t h e v a l u e o f e can be c a l c u l a t e d by knowing the v a l u e s o f V c and r ^ • I t s h o u l d be mentioned here t h a t the c o n t a c t a n g l e o b t a i n e d from e q u a t i on (. 2.16) i s the e x p e r i m e n t a l v a l u e and i s c a l l e d the ' a p p a r e n t ' c o n t a c t a n g l e i n Appendix 3, and i s r e p r e s e n t e d by 9 ' . (b) C o r r e c t i o n f o r C o n t a c t A n g l e s A s e s s i l e drop r e g a r d l e s s o f s i z e tends to get 78 f l a t t e n e d by g r a v i t y . I t i s always b e t t e r t o c o r r e c t the e x p e r i m e n t a l l y measured v a l u e s o f the c o n t a c t a n g l e s . 48 Mack has shown t h a t t h i s can be done by u s i n g the t a b l e s o f B a s h f o r t h and Adams. In t h i s a n a l y s i s , drop r a d i u s and the c a p i l l a r y c o n s t a n t o f the s l a g a r e used to c o r r e c t f o r the f l a t t e n i n g o f the drop by g r a v i t y . The o r i g i n a l a n a l y s i s by Mack has been m o d i f i e d t o s u i t the needs of the p r e s e n t work. -A complete d i s c u s s i o n o f the m o d i f i c a t i o n s i s p r e s e n t e d i n Appendix 3. (c) E x p e r i m e n t a l P r o c e d u r e C o n t a c t a n g l e s o f the f o u r s l a g s (CI , C2, C3 and C4) on an a l u m i n a s u b s t r a t e were d e t e r m i n e d a t d i f f e r e n t t e m p e r a t u r e s . Small c y l i n d r i c a l s l a g p e l l e t s o f d i a m e t e r 0.3150 cm and h e i g h t 0.203 cm ( a p p r o x i m a t e l y ) were made by d r i l l i n g s o l i d s l a g samples w i t h a h o l l o w diamond d r i l l . A f t e r the d r i l l i n g o p e r a t i o n , the ends o f the c y l i n d r i c a l specimens were c u t on a diamond saw to o b t a i n the d e s i r e d h e i g h t . The d i a m e t e r and the h e i g h t o f the c y l i n d r i c a l specimens were measured u s i n g a m i c r o m e t e r screw-gauge and hence the volumes were d e t e r m i n e d . The p e l l e t s were then p l a c e d on 100% dense a l u m i n a p l a t e s (.1.5 cms x 1 .5 cms x 0.06 cm) and m e l t e d i n a h o r i z o n t a l tube e l e c t r i c f u r n a c e 79 u s i n g n i t r o g e n a s t h e f u r n a c e a t m o s p h e r e - T h e s e e x p e r i -m e n t s w e r e c o n d u c t e d f o r v a r y i n g l e n g t h s o f t i m e a t d i f f e r -e n t t e m p e r a t u r e s . T h e r a d i u s o f t h e m o l t e n s l a g d r o p w a s t h e n m e a s u r e d u s i n g a p l a n i m e t e r o n e n l a r g e d p i c t u r e s o f t h e s l a g d r o p . A t y p i c a l e n l a r g e d p i c t u r e (6x) o f a s l a g d r o p o n a n a l u m i n a s u b s t r a t e i s s h o w n i n F i g . 21. T h e p e r i m e t e r o f t h e s l a g s p r e a d i s n o t a p e r f e c t c i r c l e a n d s o a n a v e r a g e r a d i u s o f t h e d r o p i s c o m p u t e d f r o m t h e a r e a m e a s u r e d b y t h e p l a n i m e t e r . W h e n t h e c o n t a c t a n g l e i s f o u n d f r o m t h i s ' a v e r a g e r a d i u s ' t h e a n g l e d e t e r m i n e d i s t h e a v e r a g e o f a l l a n g l e s m a d e b y t h e d r o p o n t h e s u b s t r a t e * 4s m e n t i o n e d e a r l i e r , t h e c o n t a c t a n g l e v a r i e s f r o m p o i n t t o p o i n t d u e t o v a r i o u s r e a s o n s . C o m p u t a t i o n o f c o n t a c t a n g l e s f r o m r a d i i m e a s u r e m e n t s i s m o r e r e l i a b l e t h a n t h e ' o p t i c a l o b s e r v a t i o n ' m e t h o d s . A f t e r c a l c u l a t i n g t h e c o n t a c t a n g l e s : , c o r r e c t i o n s a r e m a d e u s i n g A p p e n d i x 3. T h e c a p i l l a r y c o n s t a n t s o f t h e s l a g s h a d t o b e k n o w n , i n o r d e r t o .;-.make ' t h e s e c o r r e c -t i o n s . C a p i l l a r y c o n s t a n t s w e r e c a l c u l a t e d f r o m t h e s u r f a c e t e n s i o n o f t h e s l a g s a t d i f f e r e n t t e m p e r a t u r e s . ( d ) R e s u l t s C o n t a c t a n g l e d e c r e a s e d w i t h i n c r e a s i n g t i m e a t a f i x e d t e m p e r a t u r e a n d r e a c h e d a c o n s t a n t v a l u e a f t e r a S e s s i l e d r o p p i c t u r e o f a s l a g p e l l e t on an a l u m i n a s u b s t r a t e ( L i n e a r mag. = 6 x ) . 81 c e r t a i n l e n g t h o f t i m e . In t h e p r e s e n t work i t was f o u n d t h a t t h e a n g l e r e m a i n e d c o n s t a n t a f t e r ab.out 150 s e c o n d s . Such a t i m e d e p e n d e n t c o n t a c t a n g l e b e h a v i o u r has a l s o been r e p o r t e d by B a r t l e t t and H a l l " who w o r k e d on A1^0 3 and BeO. A l l t h e c o n t a c t a n g l e m e a s u r e m e n t s J i n t h i s s t u d y were o b t a i n e d a t t i m e s g r e a t e r t h a n 150 s e e s . The c o n t a c t a n g l e v a l u e s f o r t h e f o u r s l a g s a r e shown i n F i g . 22 and t h e d e t a i l e d c a l c u l a t i o n s l e a d i n g t o t h i s f i g u r e a r e g i v e n i n A p p e n d i x 4. No c o n t a c t a n g l e m e a s u r e m e n t s c o u l d be p e r f o r m e d a t t e m p e r a t u r e s l e s s t h a n 8 0 0 ° C as t h e s l a g s t o o k a v e r y l o n g t i m e t o m e l t w h i c h c o u l d p o s s i b l y r e d u c e t h e a c c u r a c y o f t h e m e a s u r e m e n t s . C o n t a c t a n g l e m e a s u r e m e n t s were a l s o n o t p o s s i b l e a t t e m p e r a -t u r e s a b o v e 1 0 0 0 ° C as t h e s l i a g p e l l e t s m e l t e d e v e n b e f o r e t h e y c o u l d be p l a c e d i n t h e c o r r e c t t e m p e r a t u r e z o n e o f t h e f u r n a c e and t h e s l i g h t v i b r a t i o n s i n v o l v e d i n p e r f o r m i n g t h i s o p e r a t i o n a f f e c t e d t h e m e a s u r e m e n t s . The i n t e r f a c i a l t e n s i o n ( y ^ ) between t h e s l a g s and t h e a l u m i n a s u b s t r a t e were c a l c u l a t e d . T h e s e v a l u e s a r e shown i n A p p e n d i x 4 and t h e r e l a t i o n b e t w e e n y ^ and t e m p e r a t u r e i s shown i n F i g . 23. 2.2,4.8 C o n c l u s i o n S l a g C4 i s t h e most c o r r o s i v e o f a l l t h e o t h e r 30 Contact Angles of Slags on Alumina 20 10 O O -O—C3 -A—C2 750 800 850 900 950 Temperature ( ° C ) JL 1000 1050 F i g . 22 C o n t a c t Angles of Dore S l a g s on Alumina 84 ' C - s l a g s ' a t 1.080°C. S l a g C4 i s more f l u i d than the o t h e r s l a g s a t the o p e r a t i n g t e m p e r a t u r e due to the low v i s c o s i t y and c o n t a c t a n g l e e x h i b i t e d by i t . The low con-t a c t a n g l e v a l u e causes i t to spread* more e a s i l y . So i t was d e c i d e d to s t u d y c o a t i n g c o m p o s i t i o n s on the b a s i s o f s l a g C4 a t 1080°C. I f a s u i t a b l e method o f r e d u c i n g s l a g C4 p e n e t r a t i o n i n t o r e f r a c t o r i e s can be found then the same method s h o u l d a l s o work f o r the o t h e r s l a g s . From the e x p e r i m e n t s c o n d u c t e d on the f o u r s l a g s i t was o b s e r v e d t h a t the p h y s i c a l p r o p e r t i e s ( m e l t d e n s i t y , v i s c o s i t y , s u r f a c e t e n s i o n and c o n t a c t - a n g l e ) depended on the s l a g c o m p o s i t i o n . Lead was the major element p r e s e n t i n v a r y i n g p r o p o r t i o n s i n the s l a g s and i t s e f f e c t on the s l a g p r o p e r t i e s a r e shown i n F i g u r e s 24 and 25, where the p h y s i c a l p r o p e r t i e s are c o r r e l a t e d . The r e s u l t s are summarized i n T a b l e V I I . In t h i s t a b l e , the s u b s c r i p t numbers i n d i c a t e the magnitude o f the terms (1>2>3>4). I t can be seen t h a t s l a g C3 has the h i g h e s t d e n s i t y because o f i t s h i g h l e a d c o n t e n t . The s u r f a c e t e n s i o n and c o n t a c t a n g l e f o l l o w the same p a t t e r n as they a r e i n t i m a t e l y r e l a t e d . I t seems t h a t l e a d tends to i n c r e a s e both the s u r f a c e t e n s i o n and the c o n t a c t a n g l e whereas b i s -muth r e d u c e s i t . The v i s c o s i t y tends to be i n c r e a s e d by l e a d and bismuth tends to reduce i t . 85 1 1 1 Density (P ) 8 Viscosity [Tj) at 9 0 0 ° C C 3 p / / C4 q 6h E u E 3l L5 1^ 4} C2 O CI ^ s '—p. 900 s -v 900 C2 A C4/ A' 30 40 50 60 wt. % Pb 70 80 F i g . 24 D e n s i t y and V i s c o s i t y o f Dore S l a g s vs Wt.%Pb C o n t e n t o f the S l a g s . Dark c i r c l e r e p r e s e n t s the p o i n t where Pb % and Bi % a r e combined. 86 450 1 1 1 Surfoce Tension (X) 8 Contoct Angle (#) ot 9 0 0 ° C 25 400 E o 20 ^ CD 350 15 300 10 i>3 / / / / C3 • 900 / C2 O 900 C4 c r ' r C 4 CI. -o C2 / • _L 30 40 50 wt. % Pb 60 70 80 F i g . 25 S u r f a c e T e n s i o n and C o n t e n t A n g l e o f S l a g s vs Wt. % Pb C o n t e n t . F i l l e d hexagon and s q u a r e are the p o i n t s f o r Pb % and Bi % combi ned. T a b l e VII P h y s i c a l P r o p e r t i e s o f Dore S l a g s . Slag Density Surface Tension Contact Angle Viscosity C3 P'l Y l e l n l C4 P 2 Y4 n4 C2 p3 Y2 92 n3 CI p4 Y 3 G3 n 2 88 C h a p t e r 3 3. DEVELOPMENT OF COATINGS The c o r r o s i o n o f r e f r a c t o r y b r i c k s by molten s l a g s i s g e n e r a l l y enhanced i f the b r i c k s are porous.. Molten s l a g e n t e r s the b r i c k s t h r o u g h p o r e s , r e a c t s w i t h the r e -f r a c t o r y c o n s t i t u e n t s , and c o r r o d e s the b r i c k . The p e n e t r a -t i n g power o f a c o r r o s i v e m olten s l a g i s the r a t e c o n t r o l -l i n g s t e p i n the wear o f r e f r a c t o r i e s i n t h e s e e a s e s . I f s l a g p e n e t r a t i o n can be r e d u c e d , by s e a l i n g the pores and with-out r a d i c a l l y a l t e r i n g the thermal p r o p e r t i e s o f r e f r a c t o r -i e s , then s l a g i n d u c e d c o r r o s i o n can be r e d u c e d . There a r e two p o s s i b i l i t i e s : ( i ) s u r f a c e pores o f a b r i c k can be s e a l e d by a v e r y v i s c o u s l i q u i d and ( i i ) most o f the pores can be f i l l e d by i m p r e g n a t i n g the b r i c k . The former ap-proach i s e a s i e r as b r i c k c o a t i n g s can be a p p l i e d w i t h i n -e x p e n s i v e commercial equipment such as s p r a y guns. Very l i t t l e work has been done p r e v i o u s l y on d e v e l o p i n g r e f r a c t o r y c o a t i n g s f o r b r i c k s . Usachev e t a l . d e v e l o p e d a c o a t i n g f o r f i r e c l a y r e f r a c t o r i e s used f o r 51 s t e e l t a p p i n g l a u n d e r s , and Bar d e v e l o p e d a c o a t i n g f o r usage i n the p r o d u c t i o n o f h i g h p u r i t y aluminum. 89 3.1 C o a t i n g C o m p o s i t i o n 3.1.1 P r o p e r t i es 'Required-The p r o p e r t i e s r e q u i r e d f o r an i d e a l c o a t i n g a r e : ( i ) c h e m i c a l c o m p a t i b i l i t y w i t h both the b r i c k and the s l a g , ( i i ) a f u s i o n t e m p e r a t u r e g r e a t e r than t h a t o f the s l a g s , ( i i i ) the p r e s e n c e o f f u s i b l e p h a s e s , and • ( i v ) ease o f m a n u f a c t u r e and a p p l i c a t i o n . ( i ) The c o a t i n g s h o u l d have c h e m i c a l c o m p a t i b i l i t y w i t h the b r i c k * o r e l s e i t c o u l d a t t a c k and c o r r o d e the b r i c k . The c o a t i n g s h o u l d a l s o be c o m p a t i b l e w i t h t h e s l a g so t h a t s l a g c h e m i s t r y and f u r n a c e o p e r a t i o n a r e not a f f e c t e d . The c h e m i c a l c o m p a t i b i l i t y o f a c o a t i n g w i t h a b r i c k s h o u l d depend, to a c e r t a i n d e g r e e , on the p e n e t r a t i n g power o f the c o a t i n g . The p e n e t r a t i n g power depends on the v i s c o s i t y and s u r f a c e t e n s i o n o f the c o a t i n g a t the o p e r a t i n g t e m p e r a t u r e , and on the pore s i z e and the pore volume o f the b r i c k . The c o m p a t i b i l i t y o f a c o a t i n g w i t h a s l a g can be a s s u r e d by i n c o r p o r a t i n g some o f the s l a g components i n the c o a t i n g i t s e l f . M oreover, i f the c o a t i n g t h i c k n e s s i s s m a l l ( a b o u t 1 mm) compared w i t h the b r i c k t h i c k n e s s (230 mm = 9 i n c h e s ) , then the s l a g c h e m i s t r y s h o u l d not be a f f e c t e d . ( i i ) In Dore f u r n a c e s the l i q u i d u s t e m p e r a t u r e o f s l a g 90 C4 i s 520°C and the o p e r a t i n g t e m p e r a t u r e o f the f u r n a c e i s 1080°C. The m e l t i n g p o i n t s o f the h u l k o f the phases i n a c o a t i n g have to be h i g h e r than t h a t o f the s l a g and s h o u l d be even h i g h e r than the f u r n a c e o p e r a t i n g t e m p e r a t u r e . I f t h i s i s not the c a s e , the c o a t i n g w i l l melt a t the f u r n a c e t e m p e r a t u r e and may wash away and s p e c i f i c a l l y i f the v i s c o s -i t y i s low. A complex c o a t i n g c o n t a i n i n g s e v e r a l o x i d e s w i l l not have a s i n g l e m e l t i n g p o i n t a t a f i x e d t e m p e r a t u r e but w i l l r a t h e r have s e v e r a l l i q u i d u s t e m p e r a t u r e s . Here the term m e l t i n g p o i n t o f a c o a t i n g i n d i c a t e s the t e m p e r a t u r e at which the maximum amount o f the s o l i d phases pass i n t o the l i q u i d s t a t e . ( i i i ) The p r e s e n c e o f f u s i b l e phases i n a p r o t e c t i v e c o a t -i n g f o r r e f r a c t o r y b r i c k s i s e s s e n t i a l , as t h e s e a r e the phases which s h o u l d p e n e t r a t e i n t o the pores and s e a l them. These g l a s s y phases s h o u l d have a s u f f i c i e n t l y h i g h v i s c o s -i t i e s a t the o p e r a t i n g t e m p e r a t u r e or a t the p r e t r e a t m e n t t e m p e r a t u r e so t h a t they cannot be washed away e a s i l y . How-ev e r i t s h o u l d be r e a l i z e d t h a t wash-out cannot be c o m p l e t e l y p r e v e n t e d i f the s l a g i s h i g h l y c o r r o s i v e . The amount o f f u s i b l e phases t h a t need to be p r e s e n t i n a c o a t i n g f o r s u c -c e s s f u l a p p l i c a t i o n , v a r i e s from system to system, depen-d i n g on the c h e m i s t r y and p o r o s i t y o f r e f r a c t o r y b r i c k s . I f the c o n c e n t r a t i o n o f the f u s i b l e phases i s s m a l l , and the c o a t i n g has a h i g h v i t r i f i c a t i o n t e m p e r a t u r e , i t i s 91 l i k e l y t h a t the c o a t i n g w i l l p e e l - o f f a t the o p e r a t i n g t e m p e r a t u r e . I f th.e amount o f t he f u s i b l e phase i s v e r y l a r g e , the c o a t i n g w i l l p r o b a b l y be washed away by c o n t i n -uous r e a c t i o n w i t h the s l a g . So, the p r e s e n c e of an o p t i -mum amount o f f u s i b l e phase i n a c o a t i n g , i s v e r y i m p o r t a n t . ( i v ) The ease o f m a n u f a c t u r e o f a c o a t i n g combined w i t h the a v a i l a b i l i t y o f raw m a t e r i a l s f o r c o a t i n g p r e p a r a t i o n , and the method o f a p p l i c a t i o n s h o u l d be c o n s i d e r e d , as a l l o f t h e s e f a c t o r s d e t e r m i n e the u s e f u l n e s s o f a c o a t i n g . 3.1.2 C h o i c e o f B r i c k and S l a g To s t u d y the s l a g p e n e t r a t i o n , i n t o r e f r a c t o r y b r i c k s , a s u i t a b l e b r i c k had t o be found where the amount of s l a g p e n e t r a t i o n c o u l d be f o l l o w e d e a s i l y - p r e f e r a b l y by v i s u a l o b s e r v a t i o n . Magnecon b r i c k s c o u l d not be used f o r Dore s l a g s , as both ar e b l a c k i n c o l o u r . A lumina b r i c k s ( o f p u r i t y 99%) were chosen because t h e s e b r i c k s a r e w h i t e ; s l a g p e n e t r a t i o n i s r e a d i l y o b s e r v e d . When t e s t e d a t 1080°C, both the magnecon and the a l u m i n a b r i c k s were w e l l below t h e i r r e f r a c t o r i n e s s l i m i t , so the lower r e f r a c t o r i n e s s o f a l u m i n a b r i c k s s h o u l d not i n f l u e n c e s l a g p e n e t r a t i o n . I t was a l s o r e a l i z e d t h a t i f a c o a t i n g worked w e l l f o r a l u m i n a b r i c k s , i t s h o u l d work e q u a l l y w e l l f o r magnecon b r i c k s , as the l a t t e r have more r e s i s t a n c e to the 92 Dore s l a g s . S l a g C4 i s the most c o r r o s i v e o f the f o u r Dore s l a g s ( T a b l e I I ) , and has a low v i s c o s i t y . So, s l a g C4 was chosen f o r r e f r a c t o r y - s 1 a g a t t a c k t e s t s . 3.1.3 B a s i s o f C o a t i n g Development By making use o f the s l a g and r e f r a c t o r y c h e m i s t r y , i t s h o u l d be p o s s i b l e to d e v e l o p a p r o t e c t i v e c o a t i n g f o r b r i c k s used i n Dore f u r n a c e s . The b a s i s o f such d e v e l o p -ment s h o u l d , o f c o u r s e , be the r e l e v a n t phase d i a g r a m s . However, v e r y few u s e f u l phase diagrams a r e a v a i l a b l e f o r s l a g - r e f r a c t o r y systems. T h i s a p p roach would be f e a s i b l e i n the case o f f e r r o u s m e t a l l u r g i c a l p r o c e s s e s , where most o f the phase diagrams (even f o r f o u r and f i v e component systems) have been d e v e l o p e d . Phase diagrams p e r t a i n i n g to the Dore s l a g s (CI to C4) and the magnecon b r i c k s a r e l i s t e d on T a b l e V I I I . These diagrams were o b t a i n e d from 21 the handbook "Phase Diagrams f o r C e r a m i s t s . " L i t t l e can be l e a r n e d from t h e s e d i a g r a m s , as most a r e b i n a r y or t e r n a r y i n n a t u r e . S e v e r a l a d d i t i o n a l phase diagrams would be needed t o approach t h i s work s y s t e m a t i c a l l y . In the absence o f r e l e v a n t phase diagrams and thermo-dynamic d a t a , the f o r m a t i o n o f s t a b l e compounds between Dore TABLE V I I I Phase Diagrams f o r Magnecon-Dore S l a g Systems f System Type Lowest E u t e c t i c (*C) NO. CaO-CuO-Cu20 3 ox i d e s 1013 2105 P b 0 - C r 2 0 3 2 787 2134 C u 0 - A l 2 0 3 2 " 1165 2085 A l 2 0 3 - C u 0 - C u 2 0 3 1130 2087 Cu0-S10 2 2 1050 2142 P b O - A l 2 0 3 2 650 5166 A I Z O 3:B1 2 O 3 2 820 4365 Cu 20(CuO 5S)-S10 2 2 1060 164 Mg0-Cr 20 3 2 2320 262 Cu 20-Mg0 2 " 1190 274 B1 20 3-HgO 2 785 326 A l 2 0 3 - Z n 0 2 1720 299 Bi 20 3-CaO 2 - 326 B i 2 0 3 - Z n 0 2 750 326 C a 0 - A l 2 0 3 2 1360 2295 Ca0-A1 20 3-Cu0 3 » 1550 626 Ca0-Al 20 3-S10 2-Zn0 4 1150 2669 CaO-Cr 20 3 2 1022 39 CaO-Cr 20 3-MgO 3 - 597 CaO-Cr 20 3-MgO-S10 2 4 1490 2665 C a 0 - C r 2 0 3 - S i 0 2 3 - 651 CaO-MgO 2 2370 229 Ca0-Mg0-Si0 2 3 » 1700 2471 C a 0 - S i 0 2 2 - 2302 CaO-Si0 2-ZnO 3 » - 624 C r 2 0 3 - A 1 2 ° 3 2 - 309 C r 2 0 3 - A l 2 0 3 - H g O 3 1950 710 C r 2 0 3 - A l 2 0 3 - S i 0 2 3 1580 2583 Cr 20 3-CaO-MgO 3 » - 597 C r 2 0 3 - M g 0 - S i 0 2 3 - 715 Cr 20 3-Pb0 2 787 2134 C r 2 0 3 - S i 0 2 2 » 1723 332 Cu0-Cu 20-Cr 20 3 3 1130 2125 Cu0-Cu 20-S10 2 3 2143 C a 0 - A l 2 0 3 - C r 2 0 3 -Hg0-S10 2 5 1515 2699 CaO-A1203-MgO 3 1321 2469 Ca0-A1 20 3-Hg0-Si0 2 4 » 1400 2647 C a 0 - A l 2 0 3 - S 1 0 2 3 1400 2493 Mg0-Al 20 3 2 1995 259 P b 0 - A l 2 0 3 - S 1 0 2 3 - 737 S 1 0 2 - A l 2 0 3 - C a 0 3 1540 2267 94 s l a g c o n s t i t u e n t s and o t h e r r e f r a c t o r y o x i d e s was i n v e s t i -g a t e d . Thus, the development o f a p r o t e c t i v e c o a t i n g f o r r e f r a c t o r i e s was approached from a p u r e l y e x p e r i m e n t a l v i e w p o i n t . Some commonly a v a i l a b l e metal o x i d e s were chosen and t h e i r a b i l i t y t o form s u i t a b l e c o a t i n g s was s t u d i e d . 3.1.4 C o a t i n g C o m p o s i t i o n The o x i d e s CaO, SiO,,, A ^ O ^ , MgO and Z r 0 2 were c o n s i d e r e d as p o s s i b l e c o a t i n g m a t e r i a l s . F o r any o f the above o x i d e s t o be s u i t a b l e , t h r e e c o n d i t i o n s must be s a t i s -f i e d ; the o x i d e must ( i ) r e a c t and form h i g h m e l t i n g t e m p e r a t u r e compounds w i t h the s l a g c o n s t i t u e n t s , ( i i ) form t h e s e compounds e a s i l y , and ( i i i ) n o t be e x p e n s i v e . 3.1.4.1 Phase Diagrams R e l e v a n t to C o a t i n g C o m p o s i t i o n  Development The e f f e c t i v e n e s s o f the o x i d e s - CaO, S i 0 2, A 1 2 0 3 , MgO and Z r 0 2 , i n f o r m i n g compounds or s o l i d s o l u t i o n s wi th the s i a g c o n s t i t u e n t s was s t u d i e d u s i n g the phase diagrams from Re-f e r e n c e ( 2 1 ) . The b i n a r y o r t e r n a r y o x i d e systems a l o n g w i t h t h e i r numbers as they appear i n R e f e r e n c e (21) have been l i s t e d below w i t h t h e i r s a l i e n t f e a t u r e s . P l e a s e note t h a t r e a c t i v e o x i d e s p r e s e n t i n the s i a g s and -capable o f f o r m i n g s t a b l e compounds are As^C1,., B i ^ O ^ . PbO, Cu,,0 and s b 2 o 3 . (a) ( i ) C a 0 - A s 2 0 5 (No. 5095) - T h e r e i s no b i n a r y phase diagram a v a i l a b l e but a t e r n a r y w i t h Fe 0 i n d i -X c a t e s t h e e x i s t e n c e o f t h e compounds CaO.As 20,-, Z C a O . A s 2 0 5 , 3 C a O . A s 2 0 5 , 4 C a O . A s ^ . The compounds 3 C a O . A s 2 0 5 and 4 C a O . A s 2 0 g have m e l t i n g p o i n t s o f 1450°C and 1520°C r e s p e c t i v e l y . ( i i ) CaO-BigOg-(No. 326) - There are no compounds but o n l y m o n o c l i n i c and rhombohedral s o l i d s o l u t i o n s . The m o n o c l i n i c to c u b i c t r a n s i t i o n o c c u r s a t 690°C and the h i g h e s t CaO c o n t a i n i n g c u b i c phase has a m e l t i n g p o i n t o f 900°C. ( i i i ) Ca0-Cu 20-Cu0 (No. 2105) - The o n l y compound p r e s e n t i n t h i s system i s CuO. 2 CaO. This system has ,a, lowest e u t e c t i c a t 1030°C ( i n a i r ) c o n t a i n i n g about 95 wt. % C u O . A ( i v ) CaO-PbO (No. J5140) - The o n l y compound p r e s e n t i n t h i s system i s PbO.2 CaO which has a m e l t i n g p o i n t o f 822°C. The l o w e s t e u t e c t i c i s a t 815°C w i t h 13.75 wt.% CaO. (y) CaO-Sb 0 - No phase diagram i s a v a i l a b l e on t h i s 2 3 system but some of the compounds formed between 96 t h e s e two o x i d e s have been d e t e r m i n e d . These compounds i n c l u d e : Ca oSb, o0^, CaSb o0,, Ca.Sb o'0- o o , C LI CO 4 O CO C a 9 S b o 0 t : , C a o S b o 0 , , and CaSb o0... c Z b 3 2 6 2 4 (b) ( i ) M g0-As 20 5 (No. 4054) - No b i n a r y phase diagram i s a v a i l a b l e f o r t h i s system; o n l y a t e r n a r y w i t h water. The p o s s i b l e compounds a r e 3Mg0.As 20,-, 2Mg0.As 20 5 , M g O . A s ^ and Mg0.2As 20 5. ( i i ) Mg0-Bi 20.j (No. 326) - No compounds or s o l i d s o l u -t i o n s e x i s t i n t h i s system. The e u t e c t i c i s a t 785°C w i t h about 18 wt. %MgO. ( i i i ) Mg0-Cu 20 (No. 274) - No compounds a r e p r e s e n t i n t h i s system. The e u t e c t i c i s a t 1180°C. ( i v ) MgO-PbO - Not a v a i l a b l e . (v) Mg0-Sb 20 3 - Not a v a i l a b l e . (c) (1) A l 2 0 3 - A s 2 0 5 (No. 4058) - Only the t e r n a r y phase diagram w i t h water i s a v a i l a b l e . I t appears t h a t the compoundsAl 2 03" A s 2 ° 5 ' 2 A 1 2 ° 3 ' 3 A s 2 ° 5 a n d A l 2 0 3 . 3 A s 2 0 5 are p r e s e n t . The m e l t i n g p o i n t s o f t h e s e compounds are not known. ( i i ) A^Qg-Bi^jQ-j (.No. 327) - Tfiere a r e no compounds i n t h i s s ystem, and o n l y two s o l i d s o l u t i o n s - one i s 97 m o n o c l i n i c and the.other bcc. The m e l t i n g p o i n t s o f the bcc and m o n o c l i n i c s o l i d s o l u t i o n s are a t 770°C and 810°C r e s p e c t i v e l y . ( i i i ) A^O^-PbQ (N0. 280) - There i s one compound i n t h i s s y stem, PbO.Al 2 0 3 , w i t h a m a l t i n g p o i n t "of 1000°C and the l o w e s t e u t e c t i c i s a t 865°C w i t h about 90% PbO. ( i v ) A l 2 0 3 - C u 2 0 - C u 0 (No. 2085) - The e u t e c t i c i s a t 1165°C w i t h about 8 wt. % A 1 2 0 3 . The compounds ar e CuAl 2 0 4 and CuA.lD 2-(v) A l 2 0 3 - S b 2 0 3 - Not a v a i l a b l e . (d) ( i ) S i 0 2 - A s 2 0 5 - Not a v a i l a b l e . ( i i ) S i 0 2 - B i " 2 0 3 (No. 328) - There a r e no compounds. Two s o l i d s o l u t i o n s , one c u b i c arid the o t h e r bcc are p r e s e n t . The l o w e s t e u t e c t i c i s a t 800°C. ( i i i ) S i 0 2 ~ C u 2 0 (No. 164) - There a r e no compounds p r e s e n t . The l o w e s t e u t e c t i c i s a t 1060°C w i t h 8 wt. % S 1 0 2 . ( i v ) S i 0 2 - P b 0 (No. 51-70) - The compounds are P b 4 S i 0 g , P b 2 S i Q 4 , P b 3 S i 2 0 7 and PbSIOg. The l o w e s t e u t e c t i c i s a t 718°C. 98 (v) S i 0 2 - S b 2 0 3 - Not a v a i l a b l e . (e) ( i ) Z r 0 2 - A s 2 0 5 - Not a v a i l a b l e . ( i i ) Z r 0 2 - B i " 2 0 3 (No. 328) - There a r e no compounds. Two s o l i d s o l u t i o n s a r e p r e s e n t ; one i s mono-c l i n i c and the o t h e r i s c u b i c . ( i i i ) Z r 0 2 - C u 2 0 - C u 0 (No. 2145) - There a r e no compounds or s o l i d s o l u t i o n s p r e s e n t . The l o w e s t e u t e c t i c i s a t 1160°C. ( i v ) Zr0 2~PbO (No. 2330) - There a r e no compounds or s o l i d s o l u t i o n s p r e s e n t . (v) Z r 0 9 - S b „ 0 „ - Not a v a i l a b l e . From the above i t can be seen t h a t most o f the i n f o r m a t i o n a v a i l a b l e on an o x i d e and s l a g components i s on CaO and s l a g c o n s t i t u e n t s . Moreover, i t i s e v i d e n t from the b i n a r y systems, t h a t compounds formed between CaO and o x i d e s i n the s l a g s have r e l a t i v e l y h i g h m e l t i n g p o i n t s . On the o t h e r hand, CaO a l s o has a h i g h m e l t i n g p o i n t -2787°C and i s r e a d i l y a v a i l a b l e i n i t s h y d r o x i d e and c a r b o n a t e forms. For t h e s e r e a s o n s CaO was chosen as a base compound f o r c o a t i n g development. 3.1.4.2 C o a t i n g D e v elopment E x p e r i m e n t s ( i ) V i s c o s i t y For t h i s i n v e s t i g a t i o n v i s c o s i t i e s o f t h e s l a g C4 99 w i t h v a r y i n g p r o p o r t i o n s o f CaO (10, 15, 20 and 25 wt.%) were measured. The CaO was added i n the form o f C a COH^ and mixed and ground t h o r o u g h l y i n a b a l l m i l l . The v i s c o s i t y measure-ments were c a r r i e d out w i t h the a p p a r a t u s used b e f o r e . The v i s c o s i t i e s o f the CaO and s l a g m i x t u r e s a r e g i v e n i n Appendix l a and p l o t t e d i n F i g . 26. M i x t u r e s con-t a i n i n g more than 20 wt. %CaO were e x t r e m e l y g r a i n y because of compound f o r m a t i o n and l i t t l e l i q u i d r e m a ined. So no v i s c o s i t y measurement was p o s s i b l e f o r m i x t u r e s c o n t a i n i n g more than 20 wt. .% CaO. I t can be seen from F i g . 10 and F i g . 26 t h a t the a d d i t i o n o f 20 wt. % CaO ca u s e s a 60 f o l d i n c r e a s e i n the v i s c o s i t y o f s l a g C4. The l o w e s t m e l t i n g phase i n t h i s m i x t u r e i s 670 GC, as d e t e r m i n e d by the DTA t e c h n i q u e ( F i g . 2 7 ) . The m e l t i n g p o i n t o f the pure C4 s l a g i s 520°C. A l a r g e i n c r e a s e both i n m e l t i n g p o i n t and v i s -c o s i t y can thus be a t t a i n e d by a d d i n g about 20 wt. % CaO to the s l a g . I t was o b s e r v e d d u r i n g t h e v i s c o s i t y measurement t h a t more e x t e n s i v e f r o t h i n g o c c u r r e d i n the m i x t u r e con-t a i n i n g 20 wt. % CaO and s l a g C4 than i n the pure s l a g . I t was a l s o o b s e r v e d t h a t the f r o t h i n g t e m p e r a t u r e was extended o v e r a t e m p e r a t u r e range o f about 80°C - compared w i t h 15°C f o r the pure s l a g . The i n c r e a s e i n both the e x t e n t o f i I E in 0-5 o o 01 CP ° 0 0 -0-5 C> --15 CaO + C4 —10 CaO + C4 JL 7-5 8 0 8 5 9 0 9-5 T " x | 0 4 ( K " ' ) F i g . 26 N o r m a l i z e d . V i s c o s i t y P l o t f o r CaO - S l a g C4 M i x t u r e s 100 j LOL 1 02 f r o t h i n g and the f r o t h i n g t e m p e r a t u r e range on a d d i n g CaO to the s l a g c o u l d be due to the i n c r e a s e i n s l a g v i s c o s i t y , 31 as p r o p o s e d by Cooper and K i t c h e n e r . However, the f r o t h i n g d e c r e a s e d a l o n g w i t h the f r o t h i n g t e m p e r a t u r e range on s u c c e s s i v e h e a t i n g and c o o l i n g runs p e r f o r m e d w i t h the same sample. A f t e r about f o u r c y c l e s the f r o t h i n g a l m o s t d i s a p p e a r e d . ( i i ) I d e n t i f i c a t i o n o f Compounds i n F i r e d CaO-Slag M i x t u r e s X-ray d i f f r a c t i o n p l o t s were made on C a O - s l a g C4 m i x t u r e s a f t e r h e a t i n g them to 1080°C; the r e s u l t s a r e t a b u -l a t e d i n T a b l e IX. These e x p e r i m e n t s showed t h a t CaO and s l a g C4 c o n s t i t u e n t s r e a c t e d and formed s e v e r a l compounds i n d i c a t i n g t h a t CaO was e f f e c t i v e i n t r a p p i n g the s l a g con-s t i t u e n t s . The absence o f low a n g l e s c a t t e r i n g i n the x - r a y d i f f r a c t o m e t e r p l o t s i n d i c a t e d the p r e s e n c e o f v e r y l i t t l e g l a s s y p hases. On the o t h e r hand, p r e s e n c e of some g l a s s y phase i s e s s e n t i a l i n c o a t i n g s f o r s e a l i n g p o r e s . However, i t was s t i l l d e c i d e d to t e s t the p r o t e c t i v e q u a l i t y o f t h i s m i x t u r e o f 20 wt. %CaO and s l a g C4 as a c o a t i n g m a t e r i a l on an a l u m i n a b r i c k a g a i n s t s l a g p e n e t r a t i o n . T h i s c o a t i n g was c a l l e d A4. 103 Table IX Phases I d e n t i f i e d i n CaO + S l a g C4 M i x t u r e s wt. % CaO wt. % S l a g Phases I d e n t i f i e d 5 95 Ca^ B i g 0 l g , PbO and B i ' 2 0 3 15 85 Ca^ B i c 0 7 C and some PbO. 1 , D I D 25 75 C a 2 PbO^, C a 7 B i 1 Q 0 2 2 and some f r e e CaO. 50 50 Free CaO 104 3.1.5 C o a t i n g A4 3.1.5.1 C o a t i n g M a t e r i a l s The c o a t i n g c o m p o s i t i o n i d e n t i f i e d as A4 was p r e -pared u s i n g 98% pure C a ( 0 H ) 2 and the s l a g C4. The C a ( 0 H ) 2 d i s s o c i a t e s to CaO and H 20 a t about 450°C. 3.1.5.2 C o a t i n g P r e p a r a t i o n A smooth p a s t e o f 20 wt. %CaO and s l a g C4 was made by s u s p e n d i n g p a r t i c l e s o f s l a g C4 and CaO i n w a t e r , w i t h a s m a l l amount o f a d e f l o c u l a t i n g agent and gum a r a b i c . The s l u r r y was then mixed and ground i n a c e r a m i c b a l l m i l l f o r about 12 h o u r s . 3.1.5.3 C o a t i n g A p p l i c a t i o n s T h i s p a s t e was a p p l i e d on one s u r f a c e o f s m a l l a l u m i n a b r i c k s ( d i m e n s i o n s were about 2.5 cm x 2.5 cm x 2.5 cm) u s i n g a p a i n t b r u s h . A p p r o x i m a t e l y 54 gms o f the 20 wt. 3 % CaO and s l a g C4 m i x t u r e i n 100 cm o f water gave the b e s t f l u i d c o n s i s t e n c y f o r a p p l i c a t i o n . The c o a t i n g was f i r s t d r i e d at ambient t e m p e r a t u r e and then i n an oven a t 100°C. The c o a t e d b r i c k was s l o w l y h e a t e d to 1100°C, m a i n t a i n e d a t t h a t t e m p e r a t u r e f o r one hour, and c o o l e d to room t e m p e r a t u r e . 105 A f t e r p e r f o r m i n g s e v e r a l e x p e r i m e n t s as d e s c r i b e d above, i t was o b s e r v e d t h a t a v e r y t h i c k c o a t i n g a p p l i c a t i o n produced s u r f a c e c r a c k s on the c o a t i n g . A c o a t i n g t h i c k n e s s o f about 1 mm was found to be o p t i m a l . 3.1.5.4 T e s t i n g o f C o a t i n g A4 S l a g C4 b u t t o n s (1.0 gm) were p l a c e d on an u n c o a t e d t e s t b r i c k and on an A4 c o a t e d t e s t b r i c k . These b r i c k s were then h e a t e d i n an e l e c t r i c b o x - f u r n a c e ( t h e same f u r n a c e was used p r e v i o u s l y f o r f i r i n g the 'green' c o a t i n g s ) to about 1080°C and h e l d a t t h i s t e m p e r a t u r e f o r about an hour. The b r i c k s were then c o o l e d to room t e m p e r a t u r e and s e c t i o n e d t h r o u g h the s l a g b u t t o n u s i n g a f i n e diamond saw. 3.1.5.5 D e t e r m i n a t i o n o f S l a g - P e n e t r a t i o n Depth A t y p i c a l s e c t i o n e d b r i c k a f t e r a s l a g b u t t o n t e s t i s shown i n F i g . 28; s i m i l a r o b s e r v a t i o n s were made f o r a l m o s t a l l s l a g b u t t o n t e s t s . A s c h e m a t i c drawing o f a s l a g pene-t r a t i o n depth p r o f i l e i s shown i n F i g . 28-b., The maximum p e n e t r a t i o n d e p t h , d, r e p r e s e n t s the w o r s t case o f s l a g a t t a c k ; t h i s depth was t a k e n as the s l a g p e n e t r a t i o n d e p t h . T h i s v a l u e was used f o r a l l measurments on s l a g a t t a c k . T h i s depth was measured u s i n g a v e r n i e r c a l i p e r . 106 (a) r r d _ . J . A l 2 0 3 B R I C K (b) F i g . 28 (a) P i c t u r e o f a S l a g - P e n e t r a t e d A l u m i n a B r i c k and (b) S c h e m a t i c View o f the B r i c k i n ( a ) . 3.1.5.6 R e s u l t s and D i s c u s s i o n 107 The s l a g p e n e t r a t i o n i n t o the A4 c o a t e d b r i c k was o n l y s l i g h t l y l e s s than the p e n e t r a t i o n i n t o the uncoated t e s t b r i c k , F i g . 29. T h i s poor r e s u l t i n d i c a t e d t h a t the c o a t i n g d i d not p r e v e n t , or reduce s l a g p e n e t r a t i o n . T h i s r e s u l t was not un e x p e c t e d as the c o a t i n g had v e r y l i t t l e f u s i b l e phases to seal-up the pores i n the b r i c k ( s e c t i o n 3 . 1 . T ) . / - The absence o f any f u s i b l e phases a t the o p e r a t i n g t e m p e r a t u r e r e s u l t e d i n a porous c o a t i n g and the pores i n the b r i c k remained exposed. A l t h o u g h t h i s e x p e r i m e n t was not s u c c e s s f u l i t formed a b a s i s f o r f u r t h e r development. 3.2 CaO - S i 0 2 - S l a g C o a t i n g s 3.2.1 C o a t i n g C o m p o s i t i o n A C a O - s l a g c o a t i n g does not s t o p s l a g p e n e t r a t i o n because t h i s m i x t u r e c o n t a i n s v e r y few'. f u s i b l e phases. However,CaO does i n c r e a s e the l o w e s t l i q u i d u s t e m p e r a t u r e o f s l a g C4. I t was r e a l i z e d a t t h i s s t a g e t h a t a s u i t a b l e c o a t -i n g must have some f u s i b l e phases a t the o p e r a t i n g o r p r e -heat t r e a t m e n t t e m p e r a t u r e ! A s u i t a b l e g l a s s f o r m i n g o x i d e had to be used. S i l i c a r e a c t s w i t h most o f the s l a g con-s t i t u e n t s f o r m i n g low t e m p e r a t u r e e u t e c t i c p h a s e s , (see 2 3 4 5 6 7 8 9 60 1 !...!...!...... I i I I I i I I I I i : 1 ' 1 S l a g p e n e t r a t i o n i n A ^ O ^ b r i c k s : ( i ) b r i c k 'a' i s a t e s t b r i c k and ( i i ) b r i c k '!' i s a b r i c k w i t h c o a t i n g A4. 109 s e c t i o n 3.1.4) and s i l i c a i s a l s o a good g l a s s - f o r m e r . S i l i c a was added to the A4 c o a t i n g m i x t u r e . A c o a t i n g m i x t u r e o f o n l y CaO and S i 0 2 c o u l d not be v e r y e f f e c t i v e as the l o w e s t e u t e c t i c i n t h i s system i s a t 1436°C ( F i g . 30). c o n t a i n e d e x c e p t c o a t i n g 3.2.2 Low CaO - S i 0 2 C o a t i n g s I n i t i a l l y s m a l l amounts o f S i 0 2 were added a l o n g w i t h s m a l l q u a n t i t i e s o f CaO to r e l a t i v e l y l a r g e q u a n t i t i e s o f s l a g C4 to s t u d y the e f f e c t o f S i 0 2 on the f o r m a t i o n o f f u s i b l e phases i n the c o a t i n g s . C o a t i n g s o f d i f f e r e n t c o m p o s i t i o n s A6, A8, C7, C8 and C9 were made. The c o m p o s i t i o n s o f t h e s e c o a t i n g s a r e t a b u l a t e d i n T a b l e X. These c o a t i n g m i x t u r e s were p r e -par e d as b e f o r e . D i f f e r e n t i a l t hermal a n a l y s i s e x p e r i m e n t s were pe r f o r m e d on the above c o a t i n g m i x t u r e s . A t y p i -c a l DTA p l o t f o r c o a t i n g >C8 (as can be seen i n F i g . 31) showed t h a t i n s i g n i f i c a n t amounts o f f u s i b l e A l l s u b s e quent e x p e r i m e n t a l c o a t i n g s CaO, S i 0 2 and s l a g C4 i n v a r y i n g p r o p o r t i o n s , C8 which a l s o c o n t a i n e d A l o 0 o . 2400 2000 1723 < 1200 800 -•600 _ Cristobalite +Liq. '. Tridymite+ Liq. Tridymite + Pseudowollastonite (a-CaSi03) 1125° Tridymite + Wollastonite ( B-CoSi03 ) 870° a-Quartz + Wollastonite _L S-CaSiOj + Ca 3Si 20 7 a'-Ca zSi0 4 + CaO ,Ca 3Si 20 7 4-y-Ca 2Si0 4 725 ° J- 1 y - Ca2SiQ, + CaO 30 - ^ - ^ ^ - ^ 90 CaOSiOj 3CaO-2Si02 2Ca0 Si0 2 3CoO Si0 2 C a 0 10 S i 0 2 Bert Phillips and Arnulf Muan, J. Am. Ceram. Soc, 42 [9] 414 (1959). Based mainly on data of G. A. Rankin andlF.IE. Wright, Am. J. Sci. [4], 39, 5 (1915) and J. W. Greig, Am. J. Sci., [5], 13, 1-14; [74] 133-54 (1927). Changes with respect to stability relations of tricalcium and dicalcium silicates based on data of D. M . Roy, / . Am. Ceram. Soc, 41 [8] 293-99 (1958) and J . H . Welch and W. Gutt, J. Am. Ceram. Soc, 42 [1] 11-15 (1959). F i g . 30 CaO - S i 0 ? Phase Diagram. I l l T a b l e X C o m p o s i t i o n o f C o a t i n g s C o a t i n g No. C o m p o s i t i o n (wt. % ) S i Oo CaO A 1 2°3 S l a g C4 A4 - 20 - 80 A6 10 10 - 80 A8 20 10 - 70 C8 15 15 - 70 C7 15 15 10 60 C9 20 20 — 60 C6 80 10 — 10 DI 70 20 — 10 D2 60 30 ' — 10 Sample. COATING C8 Sizes 0. 00 Rate* 15. 0 D T A Date. 19-Jul-83 Time. 9.47.06 Operators DIPANKAR F i g . 31 DTA P l o t f o r C o a t i n g C8. 113 phases were p r e s e n t i n t h i s system. T h i s i s i n d i c a t e d by the absence o f s m a l l and broad e n d o t h e r m i c peaks such as th o s e found i n F i g . 27. In o r d e r to i n c r e a s e the f u s i b l e phases i n the c o a t i n g m i x t u r e s the c o n c e n t r a t i o n o f S i 0 2 had to be i n c r e a s e d . T h i s was done by i n c r e a s i n g the c o n c e n t r a t i o n o f S i 0 2 i n the c o a t i n g m i x t u r e s w h i l e d e c r e a s i n g the amount of s l a g C4 and ke e p i n g the CaO to a low l e v e l o f about 20 wt. % i n the c o a t i n g s . 3.2.3 High S i 0 2 C o a t i n g s The amount o f S i 0 2 was i n c r e a s e d to as h i g h as 80 wt. %: i n the c o a t i n g m i x t u r e s to c r e a t e s i g n i f i c a n t con-c e n t r a t i o n s o f g l a s s y phases. C o a t i n g s C6, DI and D2, c o n t a i n i n g v a r y i n g p r o p o r t i o n s o f CaO, S i 0 2 and s l a g C4, were made. The c o m p o s i t i o n s o f th e s e c o a t i n g s can be seen i n T a b l e X. 3.2.3.1 X-ray DiffTactometer S t u d i e s o f the C o a t i n g s The c o a t i n g m i x t u r e s were f i r e d a t 1080°C and r a p i d l y c o o l e d to ambient t e m p e r a t u r e . The phases p r e s e n t i n the c o a t i n g s were then d e t e r m i n e d by x - r a y d i f f r a c t i o n . In the low C a 0 - S i 0 2 c o a t i n g s some f r e e s l a g c o n s t i t u e n t s were found to be p r e s e n t e.g., PbO and B i ^ 0 ^  and the c o a t i n g s d i d n ot appear to be v e r y amorphous. In the case o f the 114 h i g h CaO-SiG^ c o a t i n g s . t h e r e was no f r e e s l a g but CaSiO^ and S i O 2 ( c r i s t o b a l i t e ) were p r e s e n t . The p r e s e n c e o f g l a s s y phases was a l s o i n d i c a t e d by a broad peak a t s m a l l a n g l e s i n the x - r a y d i f f r a c t o m e t e r p l o t s . 3.2.3.2 C o a t i n g P r e p a r a t i o n Large b a t c h e s o f c o a t i n g m i x t u r e s were p r e p a r e d f o l 1 owing the p r o c e d u r e o u t l i n e d b e f o r e . From t h e s e m i x t u r e s smooth p a s t e s were made and then a p p l i e d to a l u m i n a b r i c k s as mentioned e a r l i e r . These c o a t e d b r i c k s were f i r e d a t a slow h e a t i n g r a t e o f 150°C/hour up to 500°C to p r e v e n t c r a c k i n g o f the c o a t i n g s . From 500°C t o 1100°C the h e a t i n g r a t e was i n -c r e a s e d t o about 250°C/hour.. At the maximum t e m p e r a t u r e of 1100°C, the specimens were h e l d f o r one hour. The b r i c k s were then c o o l e d to room t e m p e r a t u r e and were ready f o r s l a g p e n e t r a t i o n t e s t s . To form a c o a t i n g m i x t u r e o f the r i g h t c o n s i s t e n c y f o r good c o a t i n g f i n i s h and t o m i n i m i z e c r a c k i n g , i t was found t h a t the c o a t i n g s s h o u l d have the f o l l o w i n g powder to water r a t i o s : C o a t i n g s Weight o f Powder/100 gms. o f Water A6 83.0 gms C6 41.5 gms C8 32.1 gms DI 33.0 gms D2 30.7 gms 1 1 5 I t s h o u l d be mentioned here t h a t c o a t i n g C8 was made to s t u d y the e f f e c t o f A ^ O ^ on s l a g p e n e t r a t i o n . 3.2.3.3 S l a g P e n e t r a t i o n T e s t s The c o a t e d and p r e f i r e d a l u m i n a b r i c k s were s u b j e c t e d to s l a g b u t t o n t e s t s and the p e n e t r a t i o n depths were measured as d e s c r i b e d e a r l i e r . 3.3 R e s u l t s and D i s c u s s i o n C o a t i n g s A6, A8, C7, C8 and C9 ( a l l w i t h low SiOy) y i e l d e d a modest r e d u c t i o n i n s l a g p e n e t r a t i o n - F i g . 3 2 ( a ) . However, the r e d u c t i o n i n p e n e t r a t i o n was not s i g n i f i c a n t (probably due t o the absence o f any f u s i b l e phases i n t h e s e c o a t i n g s ) . From the performance o f c o a t i n g C8, i t was r e a l i z e d t h a t A 1 2 0 3 was not a good c o a t i n g m a t e r i a l . The h i g h S i 0 2 c o n t a i n i n g c o a t i n g s p e r f o r m e d r e a s o n -a b l y w e l l . The e x t e n t o f s l a g p e n e t r a t i o n i n t o a l u m i n a b r i c k s c o a t e d w i t h c o a t i n g s C6, DI and D2 ( a l l wi th h i g h S i 0 2 ) i s compared w i t h s l a g p e n e t r a t i o n i n t o the u n c o a t e d t e s t b r i c k i n F i g . 3 2 ( b ) . F i g . 32 a S l a g p e n e t r a t i o n i n A l b r i c k s : ( i ) b r i c k 'a' i s a t e s t - b r i c k , ( i i ) b r i c k '2' i s w i t h c o a t i n g A8, ( i i i ) b r i c k '4' i s w i t h c o a t i n g C7 and ( i v ) b r i c k '3' i s w i t h c o a t i n g C8. 50 1 2 3 4 5 6 _ 2 S l a g p e n e t r a t i o n i n A l ^ O ^ b r i c k s : ( i ) b r i c k 'a' i s a t e s t b r i c k , ( i i ) b r i c k 40 i s w i t h c o a t i n g C6, ( i i i ) b r i c k 56 i s w i t h c o a t i n g DI and ( i v ) b r i c k 44 i s w i t h c o a t i n g D2. 118 C h a p t e r 4 4. IMPREGNATION OF REFRACTORY BRICKS BY OXIDES AND SALTS 4.1 I n t r o d u c t i on I t became a p p a r e n t from the c o a t i n g e x p e r i m e n t s t h a t a p p l i c a t i o n o f a c o a t i n g cannot p r e v e n t s l a g p e n e t r a t i o n i n t o r e f r a c t o r y p o r e s . For t h i s r e a s o n , an a l t e r n a t i v e method to b l o c k the pores had to be f o u n d . I t was d e c i d e d to attempt to f i l l the pores o f the b r i c k s by i m p r e g n a t i n g the b r i c k s w i t h o x i d e s and s a l t s . The o n l y known p r a c t i c e f o r impregna-t i n g b r i c k s i s i n the case o f the BOF and QBOP p r o c e s s e s where carbon i s impregnated i n t o m a g n e s i t e and chrome-magnesite b r i c k s . The c a r b o n i s i n t r o d u c e d i n t o t h e s e b r i c k s by two methods: ( i ) the b r i c k c o n s t i t u e n t s a r e mixed w i t h a p i t c h b e f o r e the b r i c k i s p r e s s e d and baked, and ( i i ) f i r e d r e -f r a c t o r i e s a r e impregnated w i t h molten p i t c h by vacuum i m p r e g n a t i o n t e c h n i q u e s . Carbon i n f i l t r a t e d b r i c k s cannot be used i n Dore f u r n a c e s because o f the h i g h l y o x i d i s i n g e n v i ronment. 1 119 4.2 I m p r e g n a t i o n 4.2.1 C a l c u l a t i o n o f B r i c k P o r o s i t y Alumina b r i c k s were used f o r i m p r e g n a t i o n s t u d i e s because o f the ease w i t h which s l a g p e n e t r a t i o n p r o f i l e s c o u l d be s t u d i e d , as mentioned i n s e c t i o n ( 3 . 1 . 2 ) . To s t u d y the i m p r e g n a t i o n c h a r a c t e r i s t i c s o f t h e s e b r i c k s i t was n e c e s s a r y to know t h e i r a p p a r e n t volume p o r o s i t y ( i . e . open pore volume). The a p p a r e n t p o r o s i t y o f a r e f r a c t o r y b r i c k ( e x p r e s -sed as a p e r c e n t a g e ) i s the r a t i o o f the volume o f the open pores p r e s e n t i n a b r i c k to the t o t a l volume o f the b r i c k . T h i s i s measured i n the f o l l o w i n g way: i.) a c o n v e n i e n t l y s i z e d dry b r i c k i s weighed i n a i r (W-j), ( i i ) the b r i c k i s then b o i l e d i n water f o r about 40 minutes ( f o r a sample measuring a p p r o x i m a t e l y 2.5 cm x 2.5 cm x 2.5 cm) and weigh-ed w h i l e suspended i n water (W 2) and ( i i i ) the water-s a t u r a t e d w e i g h t o f the b r i c k i n a i r i s measured (W*3). The weight measurements are summarized: Dry w e i g h t = toy gms Suspended w e i g h t = W2 gms S a t u r a t e d weight = w"3 gms The % volume p o r o s i t y x 100. 4.1 F i v e b r i c k samples were taken and the average p o r o s i t y was d e t e r m i n e d . The r e s u l t s a r e g i v e n i n T a b l e XI. T a b l e XI P o r o s i t y o f Alumina B r i c k s W1 (gms) W2 (gms) W3 (gms) (Apparent) % Vol. Porosity 47.29 30.98 51.35 19.95 51.15 33.51 55.53 19.90 48.50 31.78 52.71 20.10 47.79 31.31 51.91 20.00 54.50 35.71 59.21 20.05 The average volume ( a p p a r e n t ) p o r o s i t y (%) o f the al u m i n a b r i c k s was found to be 20.00%. 4.2.2 Oxide I m p r e g n a t i o n I t i s o b v i o u s from the s t u d i e s o f the c o a t i n g development t h a t CaO r e a c t s w i t h most o f the s l a g con-s t i t u e n t s to form compounds and s o l i d s o l u t i o n s . So i t was d e c i d e d to impregnate the a l u m i n a b r i c k s w i t h CaO to reduce s l a g p e n e t r a t i o n . S e v e r a l methods can be used to impregnate the b r i c k s w i t h CaO and f i l l t he p o r e s . These i n c l u d e : ( i ) CaO i n aqueous s o l u t i o n , ( i i ) C a ( 0 H ) ? 121 i n aqueous s o l u t i o n and ( i i i ) CaO suspended i n wat e r . CaO has a v e r y low s o l u b i l i t y i n water a t 20°C (0.100 gm Ca0/100 cm w a t e r ) . T h i s low s o l u b i l i t y - l i m i t does not p e r m i t a s i g n i f i c a n t i n t r o d u c t i o n o f CaO. A sample c a l c u l a t i o n was performed t o v e r i f y t h i s c o n t e n t i o n . A 20% porous b r i c k , w i t h a volume o f 16.42 cm and a mass o f 47.80 gms was c o n s i d e r e d . I f a l l the open pores were f i l l e d w i t h CaO s o l u t i o n the amount o f 3 s o l u t i o n i n t h e pores would be 3.284 cm ( a p p r o x i m a t e l y 3.284 gms). T h i s amount o f s o l u t i o n c o n t a i n s 0.00328 gms o f CaO which y i e l d s a wt. % CaO i m p r e g n a t i o n o f o n l y about 0.0069. T h i s s m a l l amount o f CaO i m p r e g n a t i o n c o u l d not reduce s l a g p e n e t r a t i o n . A s i m i l a r c a l c u l a t i o n s u g g e s t s t h a t the i n t r o d u c t i o n of CaO as a s a t u r a t e d s o l u t i o n o f C a ( 0 H ) 2 y i e l d s a r e t a i n e d CaO c o n t e n t o f o n l y 0.0096 wt. %CaO a f t e r h e a t i n g a t 450°C. T h i s i s because the s o l u b i l i t y o f C a ( 0 H ) 2 i n water i s o n l y 3 about 0.185 gm/100 cm o f water. The i m p r e g n a t i o n o f a l u m i n a b r i c k s w i t h CaO by s u s p e n d i n g CaO o r C a ( 0 H ) 2 i n water was c o n s i d e r e d n e x t . A water s u s p e n s i o n o f c o a r s e CaO p a r t i c l e s was made by s u s p e n d i n g c o m m e r c i a l l y a v a i l a b l e CaO powder w i t h 122 the h e l p o f a d e f l o c u l at.ing a g e n t . The s t r e n g t h o f the 3 s u s p e n s i o n was 50 gms o f CaO powder i n 100 cm o f wat e r . A sample c a l c u l a t i o n r e v e a l e d t h a t a s u s p e n s i o n o f t h i s s t r e n g t h would y i e l d a net .weight; g a i n o f a p p r o x i m a t e l y 2.78 wt. % CaO i n the al u m i n a b r i c k s i f a l l the pores were f i l -l e d by the i n f i l t r a t i n g l i q u i d . Two methods were used to i n f i l t r a t e the CaO-water s u s p e n s i o n i n t o the a l u m i n a b r i c k s . The methods employed were d i f f e r e n t i n o p e r a t i o n a l t e c h n i -que but the o b j e c t i v e o f s o a k i n g the al u m i n a b r i c k s w i t h the s u s p e n s i o n was the same. 4.2.2.1 Vacuum S u c t i o n A vacuum s t u c t i o n d e v i c e was a v a i l a b l e as shown i n F i g . 3 3 . The bottom p l a t e o f the c y l i n d r i c a l p a r t o f the d e v i c e had h o l e s punched i n t o i t and t h i s p l a t e was con-n e c t e d to an a s p i r a t o r by f l e x i b l e r u b b e r t u b i n g . The alu m i n a b r i c k samples were p l a c e d on t h e s e h o l e s making su r e t h a t the b r i c k f a c e i n c o n t a c t w i t h the. c i r c u l a r p l a t e was r e a s o n a b l y f l a t . The a r e a c o v e r e d by the h o l e s i n the p l a t e was s m a l l e r than the a r e a o f the b r i c k f a c e . i n c o n t a c t w i t h the p l a t e . The aluminum'; h o l d e r was f i l l e d w i t h the CaO-water m i x t u r e . T h i s m i x t u r e was sucked t h r o u g h the b r i c k u s i n g an a s p i r a t o r . In o r d e r to d e t e r m i n e the amount o f 123 Acrylic Tube Collector Flask Fig. 33 App a r a t u s Used f o r Vacuum S u c t i o n . 124 CaO impregnated i n t o the b r i c k the b r i c k was h e a t e d to about 500°C a f t e r i n f i l t r a t i o n to remove the water and c o n v e r t the Ca(OH),, to CaO, and from the net we i g h t g a i n e d the e x t e n t o f i n f i l t r a t i o n was d e t e r m i n e d . The r e s u l t s o f t h i s t e s t a r e shown i n T a b l e X I I . T a b l e XII CaO Impregnation i n Alumina B r i c k s Dry Wei ght o f B r i c k s W1 (gms) Weight A f t e r CaO Impregnati on W2 (gms) Wt. % CaO Impregnati on 45.15 45.28 0.29 47.69 47.83 0.29 43. 33 43.46 0.30 49.25 49.41 0.32 50.46 50.61 0.29 The maximum i m p r e g n a t i o n t h a t c o u l d be a c h i e v e d by t h i s method was about 0.3%, w e l l below the 2.75% o r i g i n a l l y e x p e c t e d from the c a l c u l a t i o n . I t appears t h a t CaO p a r t i -c l e s do not e n t e r the pores o f the b r i c k s . In o r d e r to d e t e r m i n e the amount o f l i q u i d p e n e t r a t i o n u s i n g the vacuum s u c t i o n d e v i c e , a l u m i n a b r i c k s were impregnated w i t h water at 20°C. ..\ , ' • ' •• r 125 About 75% o f the pores i n the b r i c k s can be f i l l e d by an i n f i l t r a t i n g l i q u i d u s i n g the vacuum s u c t i o n d e v i c e . The s m a l l w e i g h t g a i n a r i s i n g from CaO i m p r e g n a t i o n en-c o u n t e r e d d u r i n g i n f i l t r a t i o n was most p r o b a b l y because the i n f i l t r a t i n g p a r t i c l e s were not e n t e r i n g the pores o f the b r i c k s . T h i s can be a t t r i b u t e d to t h e b l o c k a g e o f s u r f a c e pores by CaO p a r t i c l e s which p r e v e n t s f u r t h e r p a r t i -c l e p e n e t r a t i o n . 4.2.2.2 B o i l i n g The open volume p o r o s i t y o f b r i c k s i s found from the amount o f water i n c o r p o r a t e d i n t o a b r i c k sample.by b o i l i n g the b r i c k s i n water f o r about 40 m i n u t e s . S i n c e the vacuum s u c t i o n p r o c e d u r e was u n a b l e to f i l l a l l the pores p r e s e n t i n the b r i c k s , i t was d e c i d e d to impregnate the b r i c k s by b o i l i n g them i n a s u s p e n s i o n o f CaO i n water. A s u s p e n s i o n was made as b e f o r e and the b r i c k s were then b o i l e d i n them o v e r a b u r n e r f o r about 40 m i n u t e s . The l e v e l o f water i n the b o i l i n g v e s s e l was kept c o n s t a n t by a d d i n g s m a l l amounts o f water a t r e g u l a r i n t e r v a l s . T h i s t e s t was performed on a few b r i c k samples and then the b r i c k s were f i r e d to 50O°C and the wt. % i n c r e a s e due to CaO r e t e n -t i o n was c a l c u l a t e d . The r e s u l t s a r e t a b u l a t e d i n T a b l e x i r i . 126 T a b l e X I I I Wt. %CaO Impregnation i n Alumina B r i c k s W1 (gms) W2 (gms) wt. % CaO • Impregnati on 51. 36 51.61 0.48 47.84 48.09 0.52 49.18 49.43 0.51 B o i l i n g the b r i c k s i n c r e a s e s the wt. % CaO impregna-t i o n but t h i s i n c r e a s e i n i m p r e g n a t i o n i s s t i l l q u i t e s m a l l . The amount o f carbon i m p r e g n a t e d i n t o mag-chrome b r i c k s i s i n the o r d e r o f 2 wt. %. So both the above methods a r e not s u i t a b l e f o r o x i d e i m p r e g n a t i o n i n t o b r i c k s . However, i t s h o u l d be p o s s i b l e to i n f i l t r a t e o x i d e s i n t o r e f r a c t o r y b r i c k s i f the o x i d e p a r t i c l e s are made s m a l l e r than the pores i n the b r i c k s but t h i s work was not p u r s u e d . 4.2.3 S a l t I m p r e g n a t i o n I t was d e c i d e d a t t h i s s t a g e t o i n f i l t r a t e the a l u m i n a b r i c k s w i t h a h i g h l y s o l u b l e c a l c i u m s a l t and then c o n v e r t the s a l t to C a ( 0 H ) ? , i f p o s s i b l e , by p a s s i n g NH.OH 127 t h r o u g h the b r i c k . The s o l u b l e s a l t chosen was CaCl,,. The r e a c t i o n used to c o n v e r t C a C l 2 to C a ( 0 H ) 2 i s : C a C l 2 +2 NH 40H C a ( O H ) 2 + 2 NH^Cl 4.2 Both the v o l a t i l i z a t i o n of NH 4C1 and the c o n v e r s i o n o f Ca(0H) 2 to CaO can be done by h e a t i n g the impregnated b r i c k s to 500°C. S e v e r a l a l u m i n a b r i c k samples were im p r e g n a t e d w i t h a C a C l 2 s o l u t i o n by b o i l i n g them i n the s o l u t i o n . The b r i c k s were then s l o w l y h e a t e d to 500°C to en s u r e t h a t a l l o f the s a l t i n the b r i c k was i n the form o f C a C l 2 ( a n h y d r o u s ) . The we i g h t o f t h e s e b r i c k s was measured and then NH^OH s o l u t i o n p assed t h r o u g h the b r i c k s by vacuum s u c t i o n . The b r i c k s were r e h e a t e d to 500°C to c o n v e r t the C a ( 0 H ) 2 to CaO and v o l a t i l i z e the NH^Cl and then reweighed. The wt. % o f C a C l 2 and CaO i m p r e g n a t i o n a r e shown i n T a b l e XIV. When N H 4 O H s o l u t i o n was pass e d t h r o u g h the b r i c k s i t washed C a C l 2 out o f the pores i n the b r i c k l e a v i n g v e r y l i t t l e C a C l 2 b e h i n d . A b r i c k i m pregnated w i t h about 2.5 wt. % C a C l 2 produced o n l y about 0.5 wt. % i n c r e a s e due t o CaO r e t e n t i o n * whereas t h e w e i g h t i n c r e a s e e x p e c t e d from 2.5 wt. % C a C l 0 i s about 1.5%. T h i s method was abandoned. T a b l e XJV CaO Impregnation i n Alumina B r i c k s Dry Wt. (gms) Wt. After CaCl 2 Impregnation (gms) Wt. % C a C l 2 Impregnation Wt. After CaO Conversion (gms) Wt. % CaO Impregnation 50.45 51.74 2.50 50.70 0.50 46.23 47.46 2.60 46.48 0.54 48.78 50.07 2.58 49.04 0.53 ro co 4.2.4 S l a g P e n e t r a t i o n T e s t s on GaC1 ? Impregnated B r i c k s I t was o b s e r v e d i n the p r e v i o u s s e c t i o n , t h a t the a l u m i n a b r i c k samples c o u l d e a s i l y be impregnated w i t h CaCl s o l u t i o n and 2.5 wt. % C a C l 2 c o u l d be r e t a i n e d i n the b r i c k s In o r d e r t o e v a l u a t e the e f f e c t i v e n e s s o f CaCl,, impregnated a l u m i n a b r i c k s s l a g p e n e t r a t i o n t e s t s were c o n d u c t e d on them. The r e s u l t s are shown i n F i g . 34. The r e s u l t s i n d i -c a t e t h a t the s l a g p e n e t r a t i o n i n a C a C l 2 impregnated b r i c k was l e s s than t h a t o f c o a t i n g s C6, DI and D2. On the b a s i s o f t h i s o b s e r v a t i o n i t was c o n c l u d e d t h a t C a C l 2 c o u l d be used as an i n f i l t r a t i n g m a t e r i a l to f i l l - u p the pores o f r e f r a c t o r i e s . A f t e r t h i s p r e l i m i n a r y t e s t the e f f e c t o f the con-c e n t r a t i o n o f C a C l 2 i n r e f r a c t o r i e s on the s l a g p e n e t r a t i o n b e h a v i o u r was s t u d i e d . B r i c k s were impregnated w i t h d i f f e r ent wt. % o f C a C l 2 by two methods as d e s c r i b e d below. (a) The maximum pore volume o f the b r i c k samples t h a t c o u l d be f i l l e d by the vacuum s u c t i o n t e c h n i q u e was about 75% o f the t o t a l pore volume. By a d o p t i n g the c a l c u S r l a t i o n g i v e n below, a p r e - d e t e r m i n e d w e i g h t % i n c r e a s e c o u l d be o b t a i n e d . 3 L e t the volume o f the b r i c k = V cm , then volume 3 o f l i q u i d i n f i l t r a t e d i n t o the b r i c k = 0.15 V cm (75% o f 20% v o l . p o r o s i t y ) . 130 I i I i I i 1 i I i I i I i I i I * ! F i g . 34 Alumina b r i c k s a f t e r s l a g - b u t t o n t e s t s . ( i ) b r i c k 'a' i s a t e s t b r i c k , ( i i ) b r i c k 'b' i s w i t h c o a t i n g D2 and ( i i i ) b r i c k 'c' i s w i t h about 2 wt. % C a C l 2 i m p r e g n a t i o n . 131 L e t the w eight of the b r i c k = M gms, and the r e q u i r e d wt. % o f s o l i d s i n the b r i c k = m. L e t the w eight o f G a C l 2 t h a t w i l l be i n f i l -t r a t e d i n t o the b r i c k = x gms (unknown) Then, m = j ^ f y 4.3 From the above e q u a t i o n x can be found as m and M a r e known. A f t e r d e t e r m i n i n g the v a l u e o f x a s o l u t i o n o f x gms o f C a C l 2 was made i n water and i t s d e n s i t y measured w i t h a pycnometer. Once the d e n s i t y was known the s t r e n g t h o f the s o l u t i o n c o u l d be found u s i n g a t a b l e a v a i l a b l e i n any handbook on I n o r g a n i c C h e m i s t r y . Then s e v e r a l s o l u t i o n s were made f o r d e s i r e d amounts o f i m p r e g n a t i o n . The b r i c k s were im p r e g n a t e d by the vacuum s u c t i o n method d e s c r i b e d b e f o r e . The wt. % i m p r e g n a t i o n was c a l c u l a t e d on the b a s i s o f the amount o f anhydrous C a C l 2 i n the b r i c k . (b) When b r i c k s were b o i l e d i n a l i q u i d or s o l u t i o n about 100% o f the open pores c o u l d be f i l l e d i n about 40 m i n u t e s . However, the b o i l i n g o p e r a t i o n r e d u c e d the volume o f water p r e s e n t i n the s o l u t i o n due to e v a p o r a t i o n and so the l i q u i d i n the b o i l i n g v e s s e l was kept a l m o s t a t the same l e v e l a t a l l t i m es by a d d i n g s m a l l amounts o f water. T h i s t e c h n i q u e c o u l d be improved by r e - c i r c u l a t i n g the steam produced i n 1 32 the form o f water to the b o i l i n g v e s s e l . The above methods (a and b) showed v a r i a t i o n s o f + 5% i n the v a l u e s o f m, the w e i g h t % o f s o l i d s i n the b r i c k . I t s h o u l d be mentioned here t h a t t h e above methods worked q u i t e s u c c e s s f u l l y f o r s m a l l b r i c k samples (2.5 em x 2.5 cm x 2.5 cm) g i v i n g a l m o s t a u n i f o r m d i s t r i b u t i o n o f C a C l 2 w i t h i n the b r i c k body but i n the case o f l a r g e r b r i c k s t h i s may not work as w e l l . C a d 2 p e n e t r a t i o n o f s u r f a c e l a y e r s to a depth o f a few c e n t i m e t r e s s h o u l d p r o v i d e an adequate b a r r i e r a g a i n s t s l a g p e n e t r a t i o n . A number o f b r i c k s were impregna-t e d w i t h d i f f e r e n t c o n c e n t r a t i o n s o f C a G l ^ s o l u t i o n s and d r i e d . U s i n g t h e s e b r i c k s the e f f e c t o f t h e C a C l 2 con-c e n t r a t i o n ( p r e s e n t i n a b r i c k ) on s l a g p e n e t r a t i o n was s t u d i e d . S l a g - b u t t o n t e s t s were used. 4.2.5 E f f e c t o f D i f f e r e n t wt.% C a C l 2 I m p r e g n a t i o n on S l a g P e n e t r a t i o n When the maximum s l a g p e n e t r a t i o n d i s t a n c e i s p l o t t e d a g a i n s t the wt.•:'•% C a C l 2 i m p r e g n a t i o n i n the AlgO^ b r i c k s , the s l a g p e n e t r a t i o n f i r s t d e c r e a s e s and t h e n i n c r e a s e s as shown i n F i g . 35. The minimum s l a g p e n e t r a t i o n was 0.5 cm f o r a 2.5% i m p r e g n a t i o n (measured e x p e r i m e n t a l l y ) and 0.49 cm f o r a b r i c k c o n t a i n i n g 3% C a C l 2 , whereas the s l a g pene-t r a t i o n i n a b r i c k w i t h no c o a t i n g o r i m p r e g n a t i o n i s 1.20 133 Ail ^tA ferf mmM i 9 20 1 2 3 4 5 6 7 8 9 F i g . 35 B r i c k s w i t h v a r y i n g amounts of CaCl,, i m p r e g n a t i o n No. 37 = 0.7 wt.%, No. 51 = 1.2 wt.%, No. 38 = 2.0 wt.%, No. 2 = 2.5 wt.%, No. 47 = 3.0 wt.% and No. 36 = 4.0 wt, 134 cms. B r i c k s c o n t a i n i n g more than 3.0 wt. % C a C ^ showed i n -c r e a s e d s l a g p e n e t r a t i o n . T h i s can be a t t r i b u t e d to the f o r m a t i o n o f m i c r o and macro c r a c k s i n the b r i c k . With an i n c r e a s e d amount of s o l i d s i n the b r i c k ( g r e a t e r than 3%) the water ( f r o m the s o l u t i o n and water of c r y s t a l 1 i s a t i o n ) would f i n d i t more d i f f i c u l t t o escape ( i n the form o f steam) thr o u g h the pores d u r i n g f i r i n g . The s t r e s s e s g e n e r a t e d i n the b r i c k due to e n t r a p p e d water vapour c o u l d cause c r a c k s t o a p p e ar. The c r a c k s can be seen i n F i g s . 3& and 37. L a r g e r c o n c e n t r a t i o n s o f C a C ^ p a r t i c l e s i n the c r a c k e d r e g i o n s a r e i n d i c a t i v e o f t h e f a c t t h a t a l a r g e r amount o f steam was g e n e r a t e d i n t h e s e a r e a s . Such c r a c k s a r e c l e a r l y v i s i b l e w i t h o u t any m a g n i f i c a t i o n i n b r i c k s w i t h about 5 or 6% i m p r e g n a t i o n . S o : the b e s t i m p r e g n a t i o n o f A ^ O ^ b r i c k s was by about 3 wt. % G a C ^ - T h i s c o n c e n t r a t i o n can reduce s l a g p e n e t r a t i o n s i g n i f i c a n t l y . The b e s t c o a t i n g (D2) r e d u c e s the s l a g p e n e t r a t i o n by a f a c t o r o f 1.41. A 3 wt.% i m p r e g n a t i o n w i t h CaClg r e d u c e s s l a g p e n e t r a t i o n by a f a c t o r o f 2.40. Both f a c t o r s have been computed on the b a s i s o f s l a g p e n e t r a t i o n i n t o pure Al^Og b r i c k s w i t h o u t c o a t i n g s o r i m p r e g n a t i o n . By s t u d y i n g the e f f e c t s o f c o a t i n g s and i m p r e g n a t i o n 135 30 1 2 3 4 5 6 7 8 9 F i g . 36 Cracks i n b r i c k s due to e x c e s s i v e C a C l 2 i m p r e g n a t i o n No. 46 = 3.5 wt. %, No. 28 = 5.5 wt. %, No. 36 = 4.0 wt. %, No. 47 = 3.0 wt. %. F i g . 37 SEM p i c t u r e o f a c r a c k i n a 5.0 wt. % CaCl i m pregnated b r i c k . White p a r t i c l e s a r e C a C l 9 (x 40). 137 on s l a g - b r i c k i n t e r a c t i o n s , i t was d e c i d e d to use a combina-t i o n o f both t o reduce s l a g p e n e t r a t i o n i n t o the b r i c k s . I f the s l a g can pass-by the c o a t i n g and e n t e r i n t o the b r i c k impregnated C a C ^ p a r t i c l e s s h o u l d s t i l l s t o p f u r t h e r pene-t r a t i o n . By using the b e s t c o a t i n g s and t h e optimum amount o f i m p r e g n a t i on,, the s l a g p e n e t r a t i o n c o u l d be r e d u c e d s i g n i f i -c a n t l y . 4.2.6 I m p r e g n a t i o n and C o a t i n g W i t h o ut a c o a t i n g , the optimum amount o f i m p r e g n a t i o n was about 3.0 w t . % C a C l | . However, to o b t a i n a t o t a l p i c t u r e o f the e f f e c t o f comb i n i n g c o a t i n g . a n d i m p r e g n a t i o n , d i f f e r -e nt t y p e s of c o a t i n g s w i t h v a r y i n g amounts o f i m p r e g n a t i o n were t e s t e d . The al u m i n a b r i c k samples were impregnated w i t h d i f -f e r e n t amounts o f C a C ^ (from about 0.5 wt. % to about 6.0 wt.%) by the b o i l i n g method. The c o a t i n g c o m p o s i t i o n s chosen to c o a t t h e s e impregnated b r i c k s were A4, A6, C6, C8, DI and D2. The c o a t i n g s were a p p l i e d to t h e s e b r i c k s as b e f o r e t o a t h i c k n e s s o f about 1 mm and then the s l a g p e n e t r a t i o n t e s t s were performed and the maximum s l a g - p e n e t r a t i o n d i s t a n c e was measured. The depth o f s l a g p e n e t r a t i o n ( i n 1 38 cms) vs the wt.% i m p r e g n a t i o n was p l o t t e d f o r a l l c o a t i n g s to d e t e r m i n e the optimum amount o f C a C ^ i m p r e g n a t i o n f o r each c o a t i n g . These can be seen i n F i g s . 38 and 39. I t was d e c i d e d to c o n v e r t the wt.% i m p r e g n a t i o n on the x - a x i s to a r a t i o o f wt.% i m p r e g n a t i o n to % p o r o s i t y m u l t i p l i e d by a f a c t o r o f 1000. A s i m i l a r method was used p r e v i o u s l y by most of the workers on c a r b o n - i m p r e g n a t e d r e f r a c t o r i e s . C o a t i n g s DI and D2 p r o v i d e d t h e b e s t r e s i s t a n c e to s l a g p e n e t r a t i o n a f t e r C a C ^ i m p r e g n a t i o n . I t appears t h a t t h e r e i s an optimum amount of i m p r e g n a t i o n which p r o v i d e s a maximum r e s i s t a n c e t o s l a g p e n e t r a t i o n . T h i s knowledge i s i m p o r t a n t to a s c e r t a i n the most s u i t a b l e c o n d i t i o n s f o r both i m p r e g n a t i o n and c o a t i n g development. P a r t i c u l a r l y i t i s e a s i e r and cheaper to impregnate a t a low c o n c e n t r a -t i o n , which i n a d d i t i o n , r e d u c e s t h e chance o f c r a c k s appear-i n g i n b r i c k s . The b e s t c o m b i n a t i o n o f c o a t i n g s and/CaClg impregna-t i o n i s DI w i t h about 2.5 wt.% i m p r e g n a t i o n . Some o f the s l a g p e n e t r a t e d b r i c k samples are shown i n F i g s . 40 and 41, These f i g u r e s show the amount o f s l a g p e n e t r a t i o n a t 1080°C i n t o A l ^ O ^ b r i c k s w i t h d i f f e r e n t amounts o f i m p r e g n a t i o n and the s i x d i f f e r e n t c o a t i n g s . F i g u r e 42 compares the s l a g p e n e t r a t i o n i n t o A 1 ?0~ b r i c k s which a r e : ( i ) o n l y c o a t e d 100 150 200 wt.% Impregnotion ^ \QQQ % Porosity i g . 38 Sla g P e n e t r a t i o n D i s t a n c e vs Wt. % C a C l 2 Impregnation f o r C o a t i n g s A6, C8 and DI. 50 100 150 200 wt. % Impregnation 250 300 % Porosity x 1000 F i g . 39 Sla g P e n e t r a t i o n D i s t a n c e vs Wt. % CaCl„ I m p r e g n a t i o n f o r C o a t i A4, D2 and C6. ngs 141 F i g . 40 C o a t i n g A4 w i t h v a r y i n g amounts o f C a C l ^ Imprgnation a f t e r s l a g b u t t o n t e s t s . Impre-g n a t i o n i n c r e a s e s i n a c l o c k w i s e d i r e c t i o n s t a r t i n g from b r i c k No. 52. 142 F i g . 41 C o a t i n g DI w i t h v a r y i n g amounts o f CaCl,,. 143 F i g . 42 Compares s l a g p e n e t r a t i o n i n A ^ O ^ b r i c k s . a) = pure Al 2 0 3 b r i c k , (b) and ( c ) = o n l y c o a t i n g s , (d) o n l y C a C l ^ i m p r e g n a t i o n , (e) and ( f ) = c o a t i n g s and i m p r e g n a t i o n . 144 (DI and D2), ( i i i ) c o a t e d and impregnated (DI and D2 w i t h the optimum amount o f i m p r e g n a t i o n ) and ( i v ) n e i t h e r c o a t e d nor i m p r e g n a t e d (a t e s t b r i c k ) . A11 o f t h e s e .. f i g u r e s show s e c t i o n e d b r i c k s i n an e l e v a t i o n view. F i g . 43 shows the s l a g s p r e a d on b r i c k s w i t h o n l y c o a t i n g s (DI and D2) and c o a t i n g s w i t h i m p r e g n a t i o n . S i n c e the w e i g h t o f the s l a g b u t t o n s were the same i n a l l e x p e r i m e n t s the s p r e a d i n g of s l a g s h o u l d be more i n the case where p e n e t r a t i o n i s l e s s and v i c e v e r s a . In the case o f the combined use o f c o a t i n g s and i m p r e g n a t i o n any i m p r e g n a t i o n w i t h amounts o f C a C l 2 more than the optimum r e s u l t e d i n enhanced s l a g p e n e t r a t i o n . B e s i d e s f o r m i n g c r a c k s i n the b r i c k s too much C a C l ^ a l s o c a u s e d c r a c k i n g and f l a k i n g o f t h e c o a t i n g . 4.3 R e a c t i o n s Between C o a t i n g s , CaCl 2 and S l a g I t i s i m p o r t a n t to a s s e s s the n a t u r e o f r e a c t i o n s t h a t may be o c c u r r i n g between the c o a t i n g s , C a C l 2 and the s l a g . At h i g h t e m p e r a t u r e s , t h e components used f o r making c o a t i n g s are l i k e l y t o r e a c t and form o t h e r compounds. E x p e r i m e n t s were performed to d e t e r m i n e the n a t u r e o f r e a c - i t i o n p r o d u c t s formed at 1080°C. ( i ) S l a g s and C o a t i n g s The c o a t i n g s were mixed w i t h the s l a g i n r a t i o s o f 1:1. The m i x t u r e s were then f i r e d a t 1080°C f o r 4 h o u r s , 145 F i g . 43 S l a g s p r e a d i n g on A l b r i c k s . C l o c k w i s e f r o m top l e f t : c o a t i n g DI, c o a t i n g D2, c o a t i n g D2 and C a C l 2 i m p r e g n a t i o n , a n d c o a t i n g DI and C a C l 9 i m p r e g n a t i o n . quenched and p u l v e r i z e d . The powder was then s u b j e c t e d to x- r a y d i f f r a c t i o n . From the d i f f r a c t o m e t r i c p l o t s , a t t e m p t s were made t o i d e n t i f y the compounds. There were o n l y v e r y few broad and smal1 mpeaks i n the p i o t s , i n d i c a t i n g the p r e -sence o f p o o r l y c r y s t a l l i n e m a t e r i a l s and i n sm a l l con-c e n t r a t i o n s . No f r e e o x i d e s c o u l d be d e t e c t e d which means t h a t a l l the s l a g c o n s t i t u e n t s r e a c t e d w i t h the c o a t i n g s to form f u s i b l e phases. I t i s v e r y l i k e l y t h a t t h e s e g l a s s y phases a r e v i s c o u s and s e a l t h e pores p r e v e n t i n g f u r t h e r e n t r y o f s l a g i n t o the b r i c k . The p r e s e n c e o f f r e e C a S i 0 3 i n t h e s e m i x t u r e s a l s o i n d i c a t e s t h a t a l l the c o a t i n g m a t e r i a l s d i d not r e a c t w i t h t h e s l a g . ( i i ) C o a t i n g s CaCl 2 and S l a g M i x t u r e s o f c o a t i n g s , .CaC.^ and s l a g i n the r a t i o of 1:1:1 (by wei g h t ) were made as b e f o r e and x - r a y d i f -f r a c t o m e t r y c o n d u c t e d on them. No f r e e s l a g or C a C l ^ c o u l d be d e t e c t e d but t h e r e was some CaSiO^. The p r e s e n c e o f g l a s s y phases was a g a i n e v i d e n t . The r e a c t i o n p r o d u c t s formed w i t h the c o a t i n g s , C a C ^ and s l a g C4, a r e v e r y g l a s s y and a l l t h e ' h a r m f u l ' o x i d e s i n the s l a g are e f f e c t i v e l y t r a p p e d by r e a c t i o n w i t h the c o a t i n g m a t e r i a l s and C a C l ? . 4.4 SEM S t u d i e s on S l a g P e n e t r a t i o n 147 S c a n n i n g e l e c t r o n m i c r o s c o p y (SEM) s t u d i e s were per f o r m e d on s e c t i o n e d b r i c k s (as shown b e f o r e ; e.g. F i g . 42), i n o r d e r to d e t e r m i n e the depth o f p e n e t r a t i o n o f s l a g c o n s t i t u e n t s . The b r i c k s were scanned from the top s u r f a c e o f t h e b r i c k (where the s l a g i s p l a c e d ) to a c e r t a i n depth w i t h i n the b r i c k body. The X-ray Energy A n a l y z e r on the SEM was used to d e t e r m i n e the p r e s e n c e o f s l a g e l e m e n t s (Cu, Pb, Sb, B i , As and Zn) q u a l i t a t i v e l y , by comparing the Al peak a m p l i t u d e ( f o r an A 1 2 0 3 b r i c k ) to o t h e r peak a m p l i t u d e s . The Al peak a m p l i t u d e remained c o n s t a n t a t d i f f e r e n t depths as was e x p e c t e d . By comparing the d e c r e a s e i n peak a m p l i t u d e s o f the s l a g e lements w i t h i n c r e a s i n g d e p t h , the s l a g p e n e t r a t i o n w i t h depth i n the b r i c k can be d e t e r m i n e d . F i g . 44 r e p r e s e n t s a s l a g a t t a c k e d pure alumina r e f r a c t o r y . The x - r a y peaks o f the SEM scan c o r r e s p o n d to Al and the s l a g e lements at a depth o f about 10 mm from the top s u r f a c e o f the b r i c k . F i g . 45 (a and b) shows the a m p l i t u d e o f the peaks a t the s u r f a c e o f the b r i c k and a t a depth o f about 5 mm f o r a C a C l 2 impregnated a l u m i n a b r i c k which was s u b j e c t e d to a s l a g (C.4) p e n e t r a t i o n t e s t . T h i s shows t h a t the s l a g ( r e p r e s e n t e d by i t s e l e m e n t s ) p e n e t r a t i o n was r e d u c e d due to •Al ENERGY (KeV) Fig. 44 SEM-EDX Plot for a Slag Attacked Alumina Brick (1 cm from the top surface). 4^ CO 149 •"AL 00 ,*5L (a) Top S u r f a c e ENERGY (KeV) Pi (b) 5 mm from Top S u r f a c e 5C • J Co. ENERGY (KeV) Fig.45 SEM-EDX P l o t f o r a S 1 a g - A t t a c k e d C a C l 2 Impregnated Alumina B r i c k . 1 50 AL (a) Top S u r f a c e •AL ENERGY (KeV) (b) 5 mm from Top S u r f a c e ;- JPfc/Bi F i g . 46 ENERGY (KeV) SEM-EDX P l o t f o r a S l a g A t t a c k e d Alumina B r i c k w i t h C o a t i n g D2. 151 i m p r e g n a t i on. F i g s . 4 6 (a and b) show s i m i 1 a r EDX p l o t s f o r an alu m i n a b r i c k w i t h c o a t i n g D2. Figs., 47 (a and b) show EDX p l o t s f o r an A1,,03 b r i c k w i t h both C a C ^ i m p r e g n a t i o n and c o a t i n g D2. A l l t h e s e f i g u r e s (45 - 47) show t h a t s l a g p e n e t r a -t i o n i s r e d u c e d by the c o a t i n g s , C a C l ^ i m p r e g n a t i o n and a l s o by t h e c o m b i n a t i o n o f c o a t i n g s and i m p r e g n a t i o n . I t s h o u l d be mentioned here t h a t i t i s not p o s s i b l e to do ' p o i n t s c a n n i n g ' on the SEM so the d i s t a n c e s were measured a p p r o x i m a t e l y a t a m a g n i f i c a t i o n of 100k on a 'Reduced A r e a ' s c a n . The a r e a o c c u p i e d by the 'Reduced A r e a 1 scan a t an i n c l i n a t i o n o f 45° c o r r e s p o n d s t o a sample -4 2 are a o f 24.5 x 10 cm which i s a square w i t h 0.495 mm s i d e s . U s i n g t h i s i n f o r m a t i o n and the v e r n i e r arrangement to move the specimen, the a p p r o x i m a t e depths from the s u r -f a c e c o u l d be d e t e r m i n e d . The i r o n peaks o b s e r v e d i n the SEM p l o t s a r e due to the p r e s e n c e o f i r o n i n the b r i c k o r i n the s l a g . 1 52 00 LU O O AL (a) Top S u r f a c e St ENERGY (KeV) •AL (b) 10 mm f r o m Top S u r f a c e ENERGY (KeV) F i g . 47 SEM-EDX P l o t f o r a S l a g A t t a c k e d A l u m i n a B r i c k w i t h C a C ^ I m p r e g n a t i o n and C o a t i n g D2, 1 53 4.5 C o a t i n g s and Im p r e g n a t i o n on Magnecon B r i c k s The magnecon b r i c k s are n o r m a l l y used i n the Dore f u r n a c e s as they were found to l a s t l o n g e r than any o t h e r commercial b r i c k s . T h i s has been found i n the i n d u s t r y by t r i a l and e r r o r . I t i s e x p e c t e d t h a t the c o a t i n g s and C a C l ^ i m p r e g n a t i o n used i n the case o f al u m i n a b r i c k s s h o u l d a l s o work f o r magnecon b r i c k s i n r e d u c i n g s l a g pene-t r a t i o n . The p r e s e n c e o f MgO i n l a r g e q u a n t i t i e s (about 53% by w e i g h t ) i n t h e s e b r i c k s s h o u l d h e l p i n r e d u c i n g s l a g p e n e t r a t i o n due to i t s hig h r e f r a c t o r i n e s s ( m e l t i n g p o i n t of 2 8 0 0 ° C ) . The a p p a r e n t ( o r open) p o r o s i t y o f t h e s e magnecon b r i c k s i s ^ 20% as d e t e r m i n e d i n t h i s s t u d y . So the i m p r e g n a t i o n p r o c e d u r e used f o r A ^ O ^ b r i c k s c o u l d be used f o r Magnecon b r i c k s - w i t h o u t a l t e r a t i o n . The f o u r c o a t i n g s which worked b e s t w i t h A l ^ O ^ b r i c k s were chosen f o r t e s t s w i t h magnecon r e f r a c t o r i e s ; t h e s e were C6, C8, DI and D2. The optimum amount o f C a C ^ i m p r e g n a t i o n n e c e s s a r y f o r each c o a t i n g was d e t e r m i n e d from F i g s . 38 and 39. The b r i c k s were then i m p r e g n a t e d , c o a t e d , p r e f i r e d a t 1080°C and then s u b j e c t e d to s l a g p e n e t r a t i o n t e s t s . The b r i c k s were then s e c t i o n e d and s u b j e c t e d to SEM EDX t e s t s as mentioned e a r l i e r . The r e s u l t s o f the SEM t e s t s on magnecon b r i c k s w i t h c o a t i n g D2 and C a C ^ i m p r e g n a t i o n can be seen i n F i g s . 48 a and b . S l a g p e n e t r a t i o n can be d r a s t i c a l l y r e d u c e d by the combined use o f CaCl2 i m p r e g n a t i o n and c o a t i n g s , as can be seen from t h e s e f i g u r e s . 155 to LU 1{ ENERGY (KeV) F i g . 48 A SEM-EDX p l o t f o r Magnecon b r i c k w i t h c o a t i n g D2 a t 0.5 cm from Top S u r f a c e . u l r : • "• Co. F i g . 48 b ENERGY (KeV) SEM-EDX p l o t f o r a Magnecon b r i c k w i t h c o a t i n g D2 and Ca'Cl 2 i m p r e g n a t i o n at 0.5 cm from Top S u r f a c e . 1 56 Ch a p t e r 5 SUMMARY AND CONCLUSIONS The p h y s i c a l p r o p e r t i e s o f Dore s l a g have been d e t e r m i n e d . The r e s u l t s can be summarized as f o l l o w s : (a) The l o w e s t l i q u i d u s t e m p e r a t u r e s o b s e r v e d i n Dore s l a g a r e between 550 and 600°C. 3 (b) The s l a g - m e l t s have the d e n s i t i e s 5.0 to 7.0 g/cm i n the t e m p e r a t u r e range 750 - 1050°C. The melt d e n s i t y b e i n g c o n t r o l l e d p r i m a r i l y by the c o n c e n t r a -t i o n o f PbO and B i " 2 0 3 . (c ) The m e l t s are h i g h l y f l u i d i n the t e m p e r a t u r e range 750 - 1050°C, h a v i n g the v i s c o s i t y o f 0.4 to 0.8 _2 N . S . m (d) The s u r f a c e t e n s i o n v a l u e s o f the m e l t s a t 750°C a r e i n the range 325 - 450 dyne . cm - 1 i . e . v e r y low as compared to s i l i c a t e s l a g s (which a r e i n the range o f 700 dyne . cm"'' o r more). (e) The s l a g s made v e r y s m a l l c o n t a c t a n g l e s (15 to 30°) on a l u m i n a s u b s t r a t e s i n the t e m p e r a t u r e range 800 to 1000°C ( t h e Dor© f u r n a c e o p e r a t i n g r a n g e ) . T h i s i n d i c a t e s t h a t s l a g s w i l l s p r e a d e a s i l y on the r e f r a c t o r y s u r f a c e and p e n e t r a t e v e r y e a s i l y i n t o the pores o f r e f r a c t o r y b r i c k s . Attempts were a l s o made to d e v e l o p c o a t i n g composi-t i o n s t o p r e v e n t s l a g from p e n e t r a t i n g i n t o r e f r a c t o r i e s . S u b s e q u e n t l y , i i m p r e g n a t i o n s o f b r i c k s w i t h o x i d e s and s a l t s were a t t e m p t e d . F i n a l l y a c o m b i n a t i o n o f both i m p r e g n a t i o n and c o a t i n g was d e v e l o p e d , which appears to be e f f e c t i v e i n p r e v e n t i n g s l a g p e n e t r a t i o n and d i s s o l u t i o n o f r e f r a c t o r y b r i c k s . These r e s u l t s can be summarized as f o l l o w s : ( i ) C o a t i n g c o m p o s i t i o n s were d e v e l o p e d u s i n g CaO, S i d 2 and a s m a l l c o n c e n t r a t i o n o f s l a g s . C a l c i u m o x i d e was found to be e f f e c t i v e i n f i x i n g - u p the harmful o x i d e c o n s t i t u e n t s i n s l a g s . A l a r g e con-c e n t r a t i o n o f S i 0 2 was needed to d e v e l o p a g l a s s y phase f o r s e a l i n g - u p the p o r e s . The f i n a l and b e s t c o m p o s i t i o n c o m t a i n s 30 wt. %. o f CaO, 60 wt. % o f S i 0 2 and 10 wt. % s l a g . ( i i ) S l a g - p i l l t e s t s on c o a t i n g b r i c k s r e v e a l e d t h a t o n l y a p p l i c a t i o n o f a c o a t i n g c o u l d not s t o p s l a g p e n e t r a t i o n , a l t h o u g h i t was r e d u c e d t o some e x t e n t . F u r t h e r s t u d i e s on i m p r e g n a t i n g the b r i c k s w i t h CaO 1 58 and CaCl£ show t h a t an optimum i m p r e g n a t i o n o f b r i c k s w i t h ^ 2 wt. % CaCl2» and a c o a t i n g o f a m i x t u r e o f 30% CaO, 60% S i 0 2 and 10% s l a g on the imp r e g n a t e d b r i c k s have been a b l e to s t o p s l a g p e n e t r a t i o n i n t o the r e f r a c t o r y b r i c k s . SUGGESTIONS FOR FUTURE WORK 159 T h i s s t u d y s h o u l d be c o n s i d e r e d as the f i r s t attempt to d e v e l o p s l a g - r e s i s t a n t r e f r a c t o r i e s by i m p r e g n a t i o n and c o a t i n g , and t h u s , i t i s p r e l i m i n a r y i n n a t u r e . E x t e n s i v e s t u d i e s must be made to d e v e l o p g e n e r a l c r i t e r i a , b e f o r e t h i s t e c h n i q u e can be a p p l i e d t o a l a r g e number o f d i v e r s e s l a g - r e f r a c t o r y s ystems. Even f o r r e f r a c t o r i e s f o r the Dore f u r n a c e s , f u r t h e r e x p e r i m e n t s s h o u l d be per f o r m e d f o r improvement and o p t i m i z a t i o n o f s l a g r e s i s t i v i t y . The f o l l o w i n g s t u d i e s s h o u l d be made to improve i m p r e g n a t i o n : 1) C o n v e r s i o n o f C a C ^ i n s i d e the b r i c k to CaCO^ u s i n g (NH-^JgCO I t i s hoped t h a t because o f lower water s o l u b i l i t y o f CaCO^ as compared to Ca(0H)2> r e t e n t i o n o f CaC0 3 would be e a s i e r . T h i s i s i m p o r t a n t as CaCl,, impregnated b r i c k s may not be s u i t a b l e f o r use a t v e r y h i g h tempera-t u r e s e.g., as i n s t e e l p l a n t s . 2) Other i m p r e g n a t i n g m a t e r i a l s such as Magnesium c h r o m i t e - MgCr0 3xH,,0 which i s h i g h l y water s o l u b l e . T h i s compound' a t h i g h t e m p e r a t u r e s t r a n s f o r m s to MgCr^O^ which i s h i g h l y s l a g -r e s i s t a n t . C o a t i n g f o r m u l a e must be d e v e l o p e d from d i f f e r e n t t y p e s o f s l a g s , s p e c i a l l y f o r s t e e l p l a n t use. 161 BIBLIOGRAPHY 1. C h a k l a d e r . A . 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M e t a l s , p.53, J a n . 1956. 42. F i s c h e r W.A. e t a l . , A r c h . E i s e n h u t t e n w e s e n , 47 ( 1 0 ) , p.607, (1 9 7 6 ) . 43. Ono K. e t a l . , J . Japan I n s t . M e t a l s , 3_3, p.299, ( 1 9 6 9 ) . 44. Schrb'dinger Von E r w i n , Annalen Der P h y s i k , 46^, p.413, (1915). 45. S p e i t h and H e i n r i c h s , J . The Iron and S t e e l I n s t . , p.48, Sep. 1959. 46. Popel S.I. e t a l . , Akademii Nauk SSSR Doklady Phys. Chem. , 1_1_2, p.26, (1 9 5 7 ) . 47. P r a b r i p u t a l o o n g K. and P i g g o t t M.R., S u r f a c e S c i e n c e , 44_, p.585, (1974). 48. Mack G.L. and Lee D.A., J . Phys. Chem., 40, p.159, (19 3 6 ) . 49. B a r t l e t t R.W. and H a l l J.K., Am. Ceram. Soc. B u l l . , 44 ( 5 ) , p.444, (1965). 164 50. Usachev I.M. e t a l . , S t a l ( Engl i s h ) , 1J_, p.874, (19 70). 51. La Bar R.G., Aluminum Co. o f A m e r i c a , O f f . Gaz., 19 June 1979, Pat. No. U.S4158568 (U.S.A.). 52. Andrade E.N. d a C , P h i l . Mag. , T 7 , p.497, ( 1 9 3 4 ) . 53. Macedo and L i t o v i t z , S u r f a c e and C o l l o i d S c i e n c e , V o l . 3, Ed. Egon M a t i j e v i c , I n s . C o l l o i d and Sur. S c i . , Potsdam, New York. 54. C h a k l a d e r A . C D . , G i l l W.W. and M e h r o t r a S.P., S u r f a c e s and I n t e r f a c e s i n Ceramic and C e r a m i c -Metal Systems, Ed. Pask J . and Evans A., Plenum Pub. Corp., (1981). 165 Appendix 1 VISCOSITY OF SLAGS (a) I n t r o d u c t i o n The r h e o l o g i c a l b e h a v i o u r o f s l a g s a f f e c t s the heat 49 50 51 t r a n s f e r r a t e s , ' the mass t r a n s f e r r a t e s , the momentum t r a n s f e r r a t e s , m i x i n g and the v e l o c i t y o f d r o p l e t s f a l l i n g t h r o u g h i t . However, i n the p r e s e n t work none o f the above are as i m p o r t a n t as the i n c r e a s e o f ' r e f r a c t o r y - p e n e t r a t i n g ' power o f the s l a g due to i t s low v i s c o s i t y . I t was e s t a -b l i s h e d i n the p r e s e n t work t h a t one o f the main r e a s o n s f o r the h i g h c o r r o s i o n r a t e s o f the r e f r a c t o r i e s , was t h e e x t r e m e l y low v i s c o s i t y o f the Dore f u r n a c e s l a g s . The v i s c o s i t y o f a l i q u i d can be d e f i n e d as the measure o f i t s r e s i s t a n c e t o f l o w caused by i n t e r n a l f r i c t i o n f o r c e s . T h i s i n t e r n a l f r i c t i o n f o r c e i s due to the r e s i s t a n c e o f f e r e d to f l o w when l i q u i d l a y e r s move a g a i n s t each o t h e r . On a m i c r o s c o p i c l e v e l , v i s c o u s f l o w can be d e s c r i -bed i n two s t e p s ; the f o r m a t i o n o f h o l e s and the jumping of ' f l o w u n i t ' i n t o t h e s e h o l e s . The a c t i v a t i o n e nergy f o r v i s c o u s f l o w i s e s s e n t i a l l y the energy r e q u i r e d f o r a f l o w u n i t t o jump i n t o a h o l e . T h i s energy i s made up o f two p a r t s : ( i ) the energy n e c e s s a r y to form a h o l e c o m p a t i b l e w i t h the shape and s i z e o f the f l o w u n i t , and ( i i ) the energy r e q u i r e d to d e t a c h the f l o w u n i t from i t s s u r r o u n d -i n g s , and move i t i n t o the h o l e . 52 Andrade has shown t h a t the t e m p e r a t u r e dependence o f v i s c o s i t y can be r e p r e s e n t e d by an A r r h e n i u s type equa-t i o n n = A 1 exp(EnVRT) A l . l where n = v i s c o s i t y o f the l i q u i d A.J = a c o n s t a n t = a c t i v a t i o n e n e r g y f o r v i s c o u s f l o w R = gas c o n s t a n t T = t e m p e r a t u r e i n degree K e l v i n E q u a t i o n A l . l h o l d s t r u e f o r most l i q u i d s and 53 s l a g s . R e c e n t l y , Maeedo and L i t o v i t z d e v e l o p e d a g e n e r a l r e l a t i o n f o r the v i s c o s i t y o f l i q u i d s and s o l i d s . T h i s t h e o r y i s i n f a c t based on the o l d t h e o r y o f ' h o l e s ' and 'flo w u n i t s ' . In t h i s t h e o r y a q u a s i - c r y s t a l l i n e model i s assumed f o r the l i q u i d . The i m p o r t a n t e q u a t i o n s w i l l be mentioned h e r e : L_ = A A1.2 " ~ P j P E * PV 167 where P. = p r o b a b i l i t y o f a m o l e c u l a r jump, P^ = p r o b a b i l i t y o f the f l o w u n i t a t t a i n i n g s u f f i c i e n t e nergy t o break r e s t r a i n i n g bonds, Py = p r o b a b i l i t y t h a t s u f f i c i e n t l o c a l f r e e volume i s a v a i l a b l e t o accommodate the f l o w u n i t . The f a c t o r s i n E q u a t i o n A l . 2 o f the M-L a n a l y s i s a r e : where Ey = p o t e n t i a l energy b a r r i e r a t c o n s t a n t volume,, R = gas c o n s t a n t T = a b s o l u t e t e m p e r a t u r e ; m = m o l e c u l a r mass k = Boltzmann's c o n s t a n t V.j = m o l e c u l a r volume o f f l o w u n i t Y = a f a c t o r between 0.5 and 1.0 Vg = molar f r e e volume a s s o c i a t e d w i t h a z e r o f r e e - v o l u m e c o n d i t i o n f o r the f l o w u n i t V.f = molar f r e e volume o f the f l o w u n i t E q u a t i o n s AT.1 and AT.2 both show t h a t the r e l a t i o n between v i s c o s i t y and t e m p e r a t u r e i s an A r r h e n i type r e l a t i o n . So the f a l l o f v i s c o s i t y w i t h a r i s e i n t e m p e r a t u r e s h o u l d be o f an e x p o n e n t i a l n a t u r e f o r most l i q u i d s and molten s l a g s . 169 Appendix l a VISCOSITY MEASUREMENTS The v i s c o s i t y data f o r Dore s l a g s a r e t a b u l a t e d i n T a b l e A l a . l and the p l o t s o f v i s c o s i t y ( n ) vs t e m p e r a t u r e (°C) and i n v e r s e t e m p e r a t u r e (K~^) are g i v e n i n s e c t i o n ( 2 . 2 . 4 . 2 ) . The v a l u e s r e p o r t e d were measured a t a s p i n d l e speed o f 100 rpm because o f the low v i s c o s i t i e s o f the s l a g s . The c o u n t s r e c o r d e d by the a l u m i n a s p i n d l e were c o n v e r t e d to a b s o l u t e v i s c o s i t y (N.S. m ) u s i n g F i g . 9. The v i s c o s i t y measurements on CaO and s l a g C4 m i x t u r e s are g i v e n i n T a b l e A l a . 2 . 1 70 T a b l e A (0 S l i g C3 (H) Slag CI (1H) Slag a (Iv) Slag C4 a .1 V i s c o s i t y o f Dore S l a g s . Temperature •C 1/1 « io" Counts on Alumina Spindle Avenge Vtaxoslty M Polte log M K (1) <») (111) Counts 600 i.S! 8.80 8.85 6.95 8.80 7.93 0.90 eso 6.91 5.25 6.20 5.15 5.20 6.07 0.78 too 6.53 4.15 4.30 4.15 4.20 4.90 0.69 950 e.ie 3.(0 3.55 3.65 3.60 4.20 0.62 1000 7.86 2.70 2.75 2.95 2.80 3.27 0.51 1050 7.56 2.45 2.35 2.40 2.40 2.BO 0.45 750 9.76 5.60 5.75 5.75 5.70 6.65 0.62 800 9.32 4.70 4.50 5.05 4.75 5.54 0.74 650 8.91 4.20 4.16 4.10 4.15 4.B4 0.69 goo 8.53 3.40 3.45 3.50 3.45 4.03 0.61 950 8.16 2.60 3.10 2.65 2.B5 3.33 0.52 1000 7.86 2.55 2.45 2.80 2.60 3.03 0.46 1050 7.56 2.35 2.20 2.20 2.25 2.63 0.42 750 9.76 4.26 4.20 4.15 4.20 4.90 0.69 800 9.32 3.80 3.65 3.95 3.80 4.43 0.65 850 8.91 3.20 3.05 3.05 3.10 3.60 0.56 900 8.53 2.90 2.60 2.70 2.80 3.27 0.52 950 8.18 2.40 2.45 2.50 2.45 2.85 0.46 1000 7.86 2.30 2.15 2.15 2.20 2.57 0.41 1050 7.56 1.80 1.85 2.05 1.90 2.22 0.35 750 9.78 3.30 3.4D 3.35 3.35 3.91 0.59 BOO 9.32 2.95 2.85 3.05 2.95 3.44 0.54 850 8.91 2.30 2.35 2.55 2.40 2.60 0.45 900 8.53 2.15 2.10 2.05 2.10 . 2.45 0.39 950 8.16 1.65 1.75 1.85 1.75 2.04 0.31 1000 7.86 1.40 1.50 1.3D 1.40 1.66 0.22 1050 7.56 1.20 1.20 1.35 1.25 1.46 0.16 Tab 1e A 1 a.2 V i s c o s i t i e s of CaO and S l a g M i x t u r e s . Temperature 1/T x 10 Counts on Alumina Spindle (D (11) (111) Average Counts Viscosity (n) Poise log (n) (1) 10 wt.% CaO + Slag C4 750 770 780 840 850 880 9Z5 960 1000 1050 9.775 9.588 9.497 8.965 8.905 8.673 8.347 8.110 7.855 7.559 46.50 39.55 37.65 26.00 31.50 35.15 29.25 19.45 20.10 13.00 50.00 36.00 35.15 26.50 32.00 34.50 29.00 20.90 19.15 14.10 48.10 39.35 34.30 30.60 34.30 37.45 26.95 19.95 18.35 13.70 48.20 38.30 35.70 27.70 32.60 35.70 28.40 20.10 19.20 13.60 56.23 44.67 41.65 32.36 38.02 41.69 33.11 23.44 22.39 15.85 1.75 1.65 1.62 1.51 1.58 1.62 1.52 1.37 1.35 1.20 (11) 15 wt.% CaO + Slag C4 750 770 780 830 850 900 950 1000 1050 9.775 9.588 9.497 9.066 8.905 8.525 8.177 7.855 7.559 67.15 56.70 52.00 70.50 95.35 68.00 58.00 44.15 36.15 68.60 58.00 49.75 71.45 92.85 69.35 55.70 42.80 35.25 68.55 55.10 49.75 71.95 93.80 66.95 56.10 42.05 35.70 68.10 66.60 50.50 71.30 94.00 68.10 56.60 43.00 35.70 79.43 66.07 58.88 83.18 109.65 79.43 66.07 50.12 41.69 1.90 1.82 1.77 1.92 2.04 1.90 1.82 1.70 1.62 (111) 20 wt.% CaO + Slag C4 925 960 1000 1050 8.347 8.110 7.855 7.559 92.50 87.10 88.25 78.15 95.15 92.40 86.35 76.00 94.35 89.90 88.50 80.45 94.00 89.80 87.70 78.20 109.65 104.71 102.33 91.20 2.04 2.02 2.01 1.96 Appendix 2 SURFACE TENSION AND DENSITY OF SLAGS ( i ) The s u r f a c e t e n s i o n v a l u e s o f the s l a g s ( y ) i n dyne cm"^ are g i v e n i n T a b l e A 2 . 1 . The terms l i s t e d i n t h i s t a b l e a r e : r = i n n e r r a d i u s o f c a p i l l a r y tube g = a c c e l e r a t i o n due to g r a v i t y H = maximum manometrie h e i g h t P M = d e n s i t y o f manometrie f l u i d h = depth o f c a p i l l a r y tube immersion P s = d e n s i t y o f m e l t ( s l a g ) . _ q ( i i ) The d e n s i t i e s o f t h e s l a g s ( p s ) i n gm cm a r e g i v e n i n T a b l e A2.2. The terms l i s t e d i n t h i s t a b l e a r e e x p l a i n e d below: h-j and h^ - the two depths o f immersion o f the c a p i l l a r y tube H-| and = the two maximum manometrie h e i g h t s a t h, and h 0 . 1 73 T a b l e A2.1 S u r f a c e T e n s i o n (t) Slag C3 (II) Slag U (111) Slag CI (Iv) Slag C4 l e a p . •c r CD 9 cm sec - 2 H cms "m gm cm ^  h cm °s ("»m - N» 2rp, (rp s)2 t dViucnf' 3<Kp„-"e,> 6(H»„-h,s)2 800 0.121 981 15.10 1.00 1.00 7.00 8.10 0.0695 0.0018 447.50 850 0.121 981 14.65 1.00 1.00 6.60 8.05 0.0666 0.0016 445.00 900 0.121 981 14.40 1.00 1.00 6.40 8.00 0.0645 0.0016 442.50 950 0.121 981 14.55 1.00 1.00 6.60 7.95 0.0669 0.0017 441.00 1000 0.121 981 14.10 1.00 1.00 6.20 7.90 0.0633 0.0015 440.00 1050 0.121 981 14.00 1.00 1.00 6.20 7.80 0.0641 0.0015 437.50 750 0.121 981 13.40 1.00 1.00 6.50 6.90 0.0759 0.O022 381.30 BOO 0.121 981 13.25 1.00 1.00 6.35 6.90 0.0742 0.0021 378.80 850 0.121 981 12.65 1.00 1.00 6.05 6.60 0.0716 0.0019 375.00 900 0.121 961 12.60 1.00 1.00 5.75 6.75 0.0667 0.0018 372.50 950 0.121 981 12.20 1.00 1.00 5.55 6.65 0.0673 0.0017 368.80 1000 0.121 981 12.05 1.00 1.00 5.45 6.60 0.0666 0.0017 365.00 1050 0.121 981 11.60 1.00 1.00 5.10 6.50 0.O633 0.0015 362.50 750 0.121 981 12.85 1.00 1.00 6.40 6.45 0.0800 0.0024 351.30 BOO 0.121 981 12.50 1.00 1.00 6.10 6.40 0.0769 0.0022 350.00 850 0.121 981 12.15 1.00 1 .00 5.85 6.30 0.0749 0.002! 347.50 900 0.121 981 11.75 1.00 1.00 5.50 6.25 0.0710 0.0019 345.00 950 0.121 981 11.40 1.00 1.00 5.20 6.20 0.0676 0.0017 343.00 1000 0.121 981 11.25 1.00 1.00 5.10 6.15 0.0669 0.0016 341.30 1050 0.121 981 10.85 1.00 1.00 4.75 6.10 0.0626 0.0015 339.50 750 0.121 981 13.10 1.00 . 1.00 6.90 6.20 0.0B98 0.0030 335.00 BOO 0.121 981 12.75 1.00 1.00 6.65 6.10 0.0880 0.0029 327.50 850 0.121 981 12.40 1.00 1.00 6.45 5.95 0.OB74 0.0028 321.30 900 0.121 981 12.00 1.00 1.00 6.10 6.90 0.0834 0.0026 318.60 950 0.121 981 11.75 1.00 1.00 6.00 5.75 0.0842 0.0026 312.50 1000 0.121 961 11.65 1.00 1.00 5.95 5.70 0.0842 0.0026 306.30 1050 0.12) 98) 11.15 l.nn 1.00 5.65 5.50 0.01129 0.0025 :"I7.50 1 74 Table A2.2 Density of Slags (1) Slag C3 ( i i ) Slag C2 (i.1i) Slag CI (iv) Slag C4 Temperature h1 h 2 H l h2 (Hg-H^ p s °C cm cms cms cms cms gm cm ^ 800 1.00 1.50 15.10 18.60 3.50 7.00 850 1.00 1.50 14.65 17.95 3.30 6.60 900 1.00 1.50 14.40 17.60 3.20 6.40 950 1.00 1.50 14.55 17.85 3.30 6.60 1000 1.00 1.50 14.10 17.20 3.10 6.20 1050 1.00 1.50 14.00 17.10 3.10 6.20 750 1.00 1.50 13.40 16.65 3.25 6.50 800 1.00 1.50 13.25 16.45 3.20 6.35 850 1.00 1.50 12.85 15.85 3.00 6.05 900 1.00 1.50 12.50 15.40 2.90 5.75 950 1.00 1.50 12.20 15.00 2.80 5.55 1000 1.00 1.50 12.05 14.75 2.70 5.45 1050 1.00 1.50 11.60 14.15 2.55 5.10 750 1.00 1.50 12.85 16.10 3.20 6.40 800 1.00 1.50 12.50 15.55 3.05 6.10 850 1.00 1.50 12.15 15.10 2:>90 5.85 900 1.00 1.50 11.75 14.50 2.75 5.50 950 1.00 1.50 11.40 14.00 2.60 5.20 1000 1.00 1.50 11.25 13.80 2.55 5.10 1050 1.00 1.50 10.85 13.25 2.40 4.75 750 1.00 1.50 13.10 16.55 3.45 6.90 800 1.00 1.50 12.75 16.10 3.30 6.65 850 1.00 1.50 12.40 15.60 3.20 6.45 900 1.00 1.50 12.00 15.05 3.05 6.10 950 1.00 1.50 11.75 14.75 3.00 6.00 1000 1.00 1.50 11.65 14.60 2.95 5.95 1050 1.00 1.50 11.15 13.95 2.80 5.65 1 75 Appendix 3 CORRECTION FOR . THE EFFECT OF GRAVITATIONAL FORCE ON THE SHAPE OF A SESSILE DROP I t was mentioned p r e v i o u s l y ( S e c t i o n 2.2.4.7) t h a t g r a v i t y a f f e c t s the shape o f s e s s i l e drops and thus:; the c o n t a c t a n g l e formed between the l i q u i d and the s u b s t r a t e . 48 Mack has worked on the e f f e c t o f g r a v i t y on the shape o f 3 6 a s e s s i l e drop u s i n g the t a b l e s o f B a s h f o r t h and Adams. However, the e q u a t i o n d e v e l o p e d by Mack c o u l d not be used i n t h i s s t u d y . Thus an a l t e r n a t e e q u a t i o n has been d e v e l o p e d which does not r e q u i r e the t a b l e s by B a s h f o r t h and Adams. I t s h o u l d be r e a l i z e d t h a t the approach used here i s a p p l i c -a b l e o n l y f o r a c u t e c o n t a c t a n g l e s and f o r the shape o f the drop shown i n F i g . A 3 . 1 . C o n s i d e r a drop o f l i q u i d r e s t i n g upon a s o l i d s u r f a c e OP under the i n f l u e n c e o f g r a v i t y and s u r f a c e t e n s i o n ( F i g . A3.2). The s o l i d l i n e s PR and PR' a r e t h a a c t u a l forms o f two drops making c o n t a c t a n g l e s o f 9 and 9' r e s p e c t i v e l y w i t h OP. The d o t t e d l i n e s PQ and PQ' a r e the forms o f the drops i n the absence o f g r a v i t y and a r e s p h e r i -c a l s u r f a c e s . The s u r f a c e s PQ and PR have a common t a n g e n t PM, and PQ' and PR' have a common t a n g e n t PM 1. The q u a n t i t i e s F i g . A3.2 S e s s i l e Drop under the I n f l u e n c e o f G r a v i t y . 1 77 x and V a r e measured. V i s t h e volume o f the drop and can be o b t a i n e d by r o t a t i n g the a r e a OPR. 360° about the v e r t i c a l a x i s OR. From the geometry i n F i g . A3.2, t a n ( 9 / 2 ) = (h+e)/x A3.1 L e t the d i f f e r e n c e between the two volumes g e n e r a t e d by the a r e a s P0Q' and POR' be denoted by AV 1. i . e . AV 1 = V P 0 Q I - V P Q R , A3.2 and i f ( 9 - 9 1 ) i s s m a l l , AV' w i l l be n e a r l y equal to a V = VP0Q " VP0R* s i n c e b y c o n s t r u c t i o n V P ( ) R = V p 0 Q ' 5 AV = v p o p - v p 0 Q 1 (Tr/6)[(h+e) 3 + 3-x2 (h+e) - (h 3+3x 2h)] A3.3 S i n c e e i s v e r y s m a l l , the term e may be i g n o r e d and the e q u a t i o n A3.. 3 r e d u c e s to 3 2 h + e ( x 2 + h 2 ) - (2 AV/TT = 0 A3.4 The g e n e r a l s o l u t i o n o f the q u a d r a t i c e q u a t i o n f o r 'e' i s e x p r e s s e d as 2 2 YT + h • 2h 2 2 + 8hAV 2h 2 2 2 TT(X + h ) A3.5 A f t e r e x p a n d i n g the terms o f the above e q u a t i o n , a c c o r d i n g t o t h e b i n o m i a l theorem, and s u b s t i t u t i n g the 1 78 v a l u e o f e / x i n e q u a t i o n A 3 . 1 one o b t a i n s tan ( e / 2 ) . = tan ( e ' / 2 ) + (2AV/TTX3) C o s 2 (6 ' / 2 ) 1 2 fi - (2AV/WJT) tan ( e ' / 2 ) C o s 0 (e '/2) + . . . A3 .6 I n t h e a b o v e e q u a t i o n e' i s t h e m e a s u r e d c o n t a c t a n g l e a l s o r e p r e s e n t e d by 6 a v g ( T a b l e A 4 . 1 ) and 6 i s t h e t r u e c o n t a c t a n g l e ( a f t e r c o r r e c t i o n s ) a l s o r e p r e s e n t e d by e c Q r r ( T a l b e A 4 . 1 ) . 3 Mack t a b u l a t e d v a l u e s f o r t h e t e r m AV/X f o r d i f -f e r e n t v a l u e s o f e' and x / a . H o w e v e r , i n h i s w o r k t h e x / a r a t i o v a r i e s f r o m 0 .1 t o 0 . 5 a n d i n t h e p r e s e n t w o r k t h e x / a r a t i o was as l a r g e as 1 . 3 . The v a l u e s f r o m M a c k ' s t a b l e w e r e p l o t t e d and t h e n e x t r a p o l a t e d i n t o t h e n e c e s s a r y ' x / a ' 3 r e g i o n , F i g . A 3 . 3 . F rom t h i s f i g u r e t h e v a l u e o f AV / x c a n be f o u n d f o r any v a l u e o f e' and x / a . H e r e x i s t h e r a d i u s o f t h e s e s s i l e d r o p and a i s t h e c a p i l l a r y c o n s t a n t o f t h e l i q u i d ( a = 2 y / p g ; ] w h e r e ' y ' i s t h e s u r f a c e t e n s i o n o f t h e l i q u i d , ' p ' i s i t s d e n s i t y and ' g * . i s t h e a c c e l e r a -3 t i o n due t o g r a v i t y ) . Once t h e v a l u e o f AV/X i s f o u n d t h e v a l u e o f e ( o r 9 c o r r ) c a n be c o m p u t e d f r o m e q u a t i o n A 3 . 6 . T h i s c o r r e c t i o n has been a p p l i e d t o t h e e x p e r i m e n t a l v a l u e s o f a' (e „ w „ ) i n T a b l e A 4 . 1 i n o r d e r t o o b t a i n t h e a v g , t r u e c o n t a c t a n g l e (0corr)« The c o n t a c t a n g l e v a l u e s p l o t t e d i n F i g . 22 a r e e c 0 r r -A3.3 P l o t Used f o r C o n t a c t Angle C o r r e c t i o n s . 1 80 Appendix 4 CONTACT- ANGLES OF DORE SLAGS The v a l u e s o f the c o r r e c t e d c o n t a c t a n g l e s (9 ) . x c o r r a l o n g w i t h the r a d i i o f the s e s s i l e drops ( r ) , the volume of the drops and the u n - c o r r e c t e d v a l ue o f •©' (8 ) a r e g i v e n r avg' 3 i n T a b l e A4.1 f o r the f o u r s l a g s . The c o r r e c t i o n used here i s from Appendix 3. The i n t e r f a c i a l s u r f a c e t e n s i o n v a l u e s were c a l c u -l a t e d u s i n g the f o l l o w i n g e q u a t i o n Y S L = Y S V " Y L V C o s 9 f o r the f o u r s l a g s and a l u m i n a . . The v a l u e o f f<-y f o r alumina was o b t a i n e d from the e q u a t i o n Ys v = 892 - 0.12 T 5 4 where T i s the t e m p e r a t u r e i n °C. The v a l u e s o f Y ^ L * and Cos 6 are l i s t e d i n T a b l e A4.2. c o r r 181 Table A 4.1 Contact Angles of D i f f e r e n t S l a g s i ) Slag C3 i i ) Slag C2 i i i ) Slag CI (iv) Slag C4 Temp. °C Volume cm^ radius (cm) f 3 eavg 6 corr r l r2 61 8 2 800 0.0149 0.3484 0.3475 24.91 25.09 25.00 28.27 850 0.0149 0.3813 0.3792 19.25 19.55 19.40 22.4.0 900 0.0163 0.3965 0.3929 18.75 19.25 19.00 22.08 950 0.0157 0.4025 0.3963 17.30 18.10 17.70 20.66 1000 0.0164 0.4125 0.4094 16.82 17.18 17.00 19.91 800 0.0140 0.4027 0.4001 15.45 15.75 15.60 18.53 850 0.0165 0.4702 0.4571 11.50 12.50 12.00 14.91 900 0.0152 0.4623 0.4854 11.15 ')9.65 10.40 13.05 i950 0.0147 0.4727 0.4826 10.10 9.50 9.80 12.38 1000 0.0161 0.5037 0.4881 9.15 10.05 9.60 12.11 800 0.0152 0.4442 0.4339 12.55 13.45 13.00 15.90 850 0.0165 0.4849 0.4980 10.50 9.70 10.10 12.89 900 0.0144 0.4862 0.4975 9.10 8.50 8.50 11.26 950 0.0158 0.5251 0.5141 7V95 8i:45 8.45 10.80 1000 0.0160 0.5486 0.5315 7.05 7.75 7.75 9.77 800 0.0165 0.4904 0.4766 10.15 . 11.05 10.60 13.52 850 0.0143 0.4906 0.4833 8.80 9.20 9.00 11.80 900 0.0156 0.5427 0.5590 7.10 6.50 6.80 9.47 950 0.0161 0.5635 0.5726 6.55 6.25 6.40 9.00 1000 0.0159 0.5655 0.5779 6.40 6.00 6.20 8.73 1 82 T a b l e A4.2 I n t e r f a c i a l T e n s i o n o f D i f f e r e n t S l a g s Temp. °C YSV dynectn"1 YLV dynecm"1 e corr Cose„„„„ corr Y S L (dyne-cm"1) 800 704.00 447.50 28.27 0.8807 309.90 850 748.00 445.00 22.40 0.9245 336.60 900 792.00 442.50 22.08 0.9267 381.94 950 836.00 441.00 20.66 0.9357 423.36 1000 880.00 440.00 19.91 0.9402 466.31 800 704.00 378.80 18.53 0.9482 344.82 850 748.00 375.00 14.91 0.9663 385.64 900 792.00 372.50 13.05 0.9742 429.11 . 950 836.00 368.80 12.38 0.9767 475.80 1000 880.00 365.00 12.11 0.9777 523.14 800 704.00 350.00 15.90 0.9617 367.41 850 748.00 347.50 12.89 0.9748 409.26 900 792.00 345.00 11.26 0.9808 453.62 950 836.00 343.00 10.80 0.9823 499.07 1000 880.00 341.30 9.77 0.9855 543.65 800 704.00 327.50 13.52 0.9723 385.57 850 748.00 321.30 11.80 0.9789 433.48 900 792.00 318.80 9.47 0.9864 477.54 950 836.00 312.50 9.00 0.9877 527.34 1000 880.00 306.30 8.73 0.9884 577.25 

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