MODELING OF MOVING-BED COAL GASIFIERS

A mathematical model of an atmospheric countercurrent moving-bed coal gasifier was developed and used for air + steam gasification. The model considers an adiabatic reactor in a stationary state with different temperatures for the solid and the gas and uses a shrinking unreacted core model to describe the solid-gas reactions. The system of differential equations for the mass and energy balances is solved by using a fourth order Runge-Kutta-Merson method with variable step size. The effect of the reaction scheme in the combustion zone on the longitudinal temperature profiles predicted by the model is studied. A parametric study is performed on the effect of reactivity with steam, CO2and O2) of particle size, and of the emissivity of the ash layer on the longitudinal temperature profiles, the maximum temperature, and the gas composition. The effect of operating conditions on the gas compositions, low heating value, and thermal efficiency of the process is also studied. © 1990, American Chemical Society. All rights reserved.