This paper presents a numerical simulation of particle motion and combustion in a pulverized coal-fired sudden-expansion combustor with coaxial jets. The computations are conducted for both bituminous and lean coal flames. The obtained results show the trajectories and the mass and temperature variations with time for coal particles of different initial sizes. it is seen that the interactions between the particles and the recirculating flow have pronounced effects on particle motion and combustion. Particle motion should match the gas-how pattern and the penetration of the coal particles into the hot reverse dow is favorable for their achieving sufficient heating and devolatilization. On the other hand, the gas recirculating flow pattern has to be properly arranged to meet the needs of particle heating and devolatilization for different grades of coal. (C) 2000 Elsevier Science Ltd. All rights reserved.