Mathematical modeling of gasification of high-ash Indian coals in moving bed gasification system

Simulation of gasification of high-ash Indian coal in an updraft moving bed gasification system is presented in this paper. A steady one-dimensional numerical model, which takes into account of drying, devolatilization, combustion and gasification processes, is used to solve the mass and energy balances in the gasification system. The results from the model have been validated against the experimental data available in literature for various types of coals. The predicted product gas composition, its calorific value and the exit temperature are in agreement with the reported results. The validated model is used to study the effect of input parameters such as oxygen content in air stream, steam flow rates and the pressure of the gasification system. Results indicate that the value of oxygen mole fraction around 0.42 in the oxidizer stream can provide optimum performance in oxygen-based gasification systems. There is a range of steam-to-coal ratio that is dependent on the oxygen content in oxidizer stream. For air-based systems, this value is around 0.4 and for oxygen-based systems it is 1.5. The gasification performance improves with operating pressure significantly. An operating pressure of around 8 bar and higher, based on the application, can be used for achieving the required performance with high-ash coals. The model is useful for predicting the performance of high-ash Indian coals in a moving bed gasification system under different operating parameters. Copyright © 2013 John Wiley & Sons, Ltd.