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Simulation of the Scrubber Section of a Fluid Coker Jankovic, Jasna

Abstract

HYSYS.Plant Version 3.0.1 in steady-state mode was used to simulate the Scrubber Section of a Syncrude Canada Ltd.'s Fluid Coker, a plant for oil sand bitumen upgrading. In this scrubber, hot vapours from the Fluid Coker are contacted counter-currently with cooler oils to remove heavy components. The objective was to develop a reliable simulation model, which would describe the plant operation as closely as possible, and to use this model to investigate possible process improvements, by changing process and design parameters. Plant data was used to define the composition, flow rate, temperature and pressure of all inlet streams, as well as parameters for all unit operation blocks. Additional data was provided to evaluate the reliability of the simulation model. The Scrubber Section was simulated using a number of unit operation blocks and process streams. The HYSYS Peng-Robinson property package was utilized. Heavy hydrocarbon mixtures were defined using pseudo-components derived from input laboratory assays data: boiling curves, density and viscosity. An investigation on presence of liquid phase in the vapour streams and heavy components in the Scrubber Overhead was undertaken, and its suggestions taken into account during the simulation. When the whole flowsheet was set up and a converged solution obtained, the HYSYS optimizer tool was used to determine unknown parameters in the system, such as tray and section efficiencies in the sheds and the packed section of the Scrubber, respectively, and fractions of vapour and liquid that reach equilibrium above the scrubber pool. An objective function was defined to quantify the extent of matching of model predictions with the plant data. The unknown parameters were varied to minimize the objective function. The set of parameters that resulted in the smallest deviation from the plant data was chosen and fixed as the "Base Case". Results of the simulation match the plant data very well (within 3.2% of the plant data). Eleven case studies were carried out in which different operating parameters and design changes were simulated to study their effects on predicted process performance: ATB Flow Rate, HGO Wash Flow Rate, HGO Underwash Flow Rate, HGO Wash Temperature, HGO Underwash In and Out of Service, Number of Trays in the Sheds, Number of Grid Sections, Simulation of the Conditions from Start of Run to End of Run, Water Instead of HGO Underwash, Saturated Steam Instead of HGO Underwash and Overhead Recycle Cut Point Changes. Based on the results of the case studies the suggestions for further process improvements were made, as well as recommendations for additional investigations.

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