Modeling and simulation of an entrained flow coal gasifier

Abstract

A mathematical model has been developed to simulate the Texaco downflow entrained-bed pilot-plant gasifier using coal liquefaction residues and coal-water slurries as feedstocks. This model describes the physical and chemical processes occurring in an entrained coal gasifier. The gasification kinetics describes different complex reactions occurring in the gasifier and the hydrodynamics describes mass, momentum and energy balances for solid and gas phases. Temperature, concentration and velocity profiles along the reactor height were obtained by solving the mass, momentum and energy balances. Parameter studies were made to provide a better understanding of the reactor performance for various inlet feed conditions utilizing the model. RAKESH GOVIND and JOGEN SHAHDepartment of Chemical and Nuclear Engineering University of Cincinnati Cincinnati, OH 45221 SCOPE Entrained-bed gasifiers are cocurrent flow reactors in which pulverized or atomized hydrocarbons react with oxygen and steam to produce gaseous fuels. These reactors are becoming popular in the processing of coal into synthetic fuels and thermal energy since they produce higher coal gasification rates and are easier to operate than fluidized-or fixed-bed reactors. Further, due to the incineration effect they produce a product gas that is relatively free of higher hydrocarbons particularly the tarry materials.In this paper, a mathematical model has been developed to simulate the Texaco downflow entrained-bed pilot-plant gasifier using coal liquefaction residues as feedstocks. Results of the simulation have been compared with experimental data from the gasifier. CONCLUSIONS AND SIGNIFICANCEThe Texaco downflow pilot-plant gasifier was simulated by simultaneously solving the mass, momentum and energy balances-for the solid and gas phases. Good agreement was obtained between the simulation programs and experimental results. The gas composition leaving the gasifier and the final carbon conversion depends on three essential parameters: the fuel rate, the oxygen to fuel ratio, and the steam-fuel ratio. It was found that oxygen-fuel ratio affects carbon conversion more than the steam-fuel ratio. The steam-fuel ratio significantly affects the gas product composition. The optimum oxygen-fuel ratio is between 0.8 and 0.9 to achieve 98-99% conversion. Depending on the oxygen-fuel ratio, the optimum steam-fuel ratio ranges from 0.3 to 0.6 using coal liquefaction residues as feedstocks.

Simulation and optimization integrated gasification combined cycle by used aspen hysys and aspen plus

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Environmental Performance of Hypothetical Canadian Pre-Combustion Carbon Dioxide Capture Processes Using Life-Cycle Techniques

“…The highly pure oxygen (95% O 2 ) at an ambient temperature of 25˝C and slurry coal were introduced at the top of the gasifier. The mass ratio between injected water and coal was set at 0.54 and the oxygen-fuel ratio was set at 0.85, based on the report from [31] for the optimum steam-fuel ratio and oxygen-fuel ratio, respectively. The fuel (slurry-coal) flows co-currently and reacts with the oxygen.…”

Modified Two-Step Dimethyl Ether (DME) Synthesis Simulation from Indonesian Brown Coal

“…A gasifier yields the product composition that approaches equilibrium [11]. The gasification design was based on technology of GE/Texaco, a major player in gasifier technology [12,13]. This design uses partial oxidation of the coal in oxygen generated in an air separation unit to provide the required heat to drive the gasification reactions.…”