ABSTRACT

Coal gasifier is a key process to produce a high-quality gas in Integrated-coal Gasification Combined-Cycle (IGCC) plants. The entrained-flow coal gasifier has been widely used in IGCC plants due to the high gasification rate achievement and a relatively clean gas production. In this study, a three-dimensional Computational Fluid Dynamics (CFD) model is developed to predict the performance of coal gasification in an entrained-flow gasifier using a CFD code, Fluent (Fluent, Inc., Lebanon, NH). The kinetic model is built by dividing the coal gasification into sub-models such as pyrolysis, char gasification, and gas phase reactions. The discrete phase model (DPM) is used to examine the behavior of coal particles inside the gasifier. Carbon combustion and char gasification are taken into account by using the Multiple Surfaces Reaction (MSR) model, and the gas phase reactions are considered as the Turbulent Reacting Flow (TRF) model. The simulation results provide the detailed information about the flow field, temperature and species concentration distributions inside an entrained-flow gasifier including dry-feed and slurry-feed types. The numerical results of the CFD simulation are compared to the experimental data from published works.

INTRODUCTION

Modeling of coal gasification process has received significant attention over the last two decades. Several mathematical models have been developed for entrained flow gasifiers. Wen and Chaung (1979), Govind and Shah (1984) developed models for Texaco down-flow, slurry-type entrained gasifiers. Ni and Williams (1995) developed a multivariable model for Shell coal gasifiers on the basis of equilibrium, mass and energy balances by means of non-linear programming. Recently, Liu et al. (2000) proposed a model for a pressurized entrained flow coal gasifier to determine the effect of pressure, reaction kinetics and char structure on the gasification reactions. The model predictions were compared to published experimental data.

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