Computational fluid dynamics modelling of an entrained flow biomass gasifier

A mathematical model, based on the Computational Fluid Dynamics package CFX4, has been developed to study the flow within an entrained flow biomass gasifier. The gasifier is designed to convert sawdust and chopped cotton gin trash into a low calorific value gas which can be burned in a modified engine to run a generator. Calculations of the flowfield are performed using the standard k-epsilon model and a Differential Reynolds Stress Model (DSM). In line with current thinking, it is shown that the k-epsilon model gives unphysical results for complex swirling flows, whereas the DSM model performs well. Particle tracking was performed to determine typical trajectories for the biomass and char and the results used to determine means of avoiding slagging in the gasifier base. The simulations have proved to be very useful to the designers who are now using the model to optimise the design. (C) 1998 Elsevier Science Inc. All rights reserved.