Numerical simulation of gas-solid flows in fluidized bed gasification reactor

Abstract

A numerical model for simulating a fluidized bed gasifier should include appropriate parameters to capture the dynamics of gas-solid flows, gasification kinetics and the interaction between these two. The focus of the present study is to analyze the effects of coal gasification chemistry models reported in literature on the prediction of product gas composition in a fluidized bed gasification reactor. Numerical results are validated against the experimental data available in literature. The validated model is used to examine the available chemical kinetics schemes for water gas shift reaction, steam methane reforming reaction and char heterogeneous reactions. It is also used to assess the effects of hydrodynamic models parameters such as drag model, particle-particle restitution coefficient and specularity coefficient on exit gas composition. Results show that the predictions of product gas composition are notably affected by the choices of the kinetics schemes for water gas shift and steam methane reforming reactions. Systematic analysis using the available choices to simulate initial processes such as moisture removal, volatile and tar cracking is reported. Drag models and the value of specularity coefficient are shown to have no effect on product gas composition, and the particle-particle restitution coefficient slightly influences the predicted gas composition.