A computational fluid dynamic modelling study of a jet fluidised bed gasifier has been carried out. The modelling was based on the Euleian-Eulerian models for gas and solid flows, which take into account the hydrodynamics. mass and heat transfer, and heterogeneous and homogeneous reactions. The bubble dynamics was simulated in detail, enabling its effect on temperature distributions, gasification reactions and gas compositions in the bed to be examined. The results revealed that jet growth, bubble rise, and the associated convective flow play a significant role in the heat exchange and mass transfer, and in turn, affect the gasification reactions. (c) 2005 Elsevier Ltd. All rights reserved.