(24e) Numerical Simulation of Coal Gasification in a Counterflow Fluidized Bed Reactor

This study focuses on modeling and simulation of coal gasification in a bench-scale counterflow fluidized bed. The mathematical model is based on Eulerian-Eulerian description of multi-phase flows. The flow governing equations are solved by a finite volume method in which a time-splitting scheme is used to integrate the chemical reaction source term in a separate step using a stiff ordinary differential equation solver. The solid phase consists of Kansas bituminous coal, which contains four pseudo-species: ash, moisture, volatile matter and fixed carbon. The gas phase includes six species: CO, CO2, CH4, H2, H2O and N2. The bed is a counterflow gasifier in which coal is fed to the reactor from the top by gravity. Steam serves as the fluidizing media which enters form the bottom. Gasification occurs following de-volatilization and cracking processes as incoming coal particles heated rapidly to the gasification temperature. The char gasification and water-gas shift reactions are described by a four-step global mechanism. Simulations are conducted in a three-dimensional domain and capture the transient behavior of the reactor. Results show good agreement with experimental data.