A dynamic model of the Shell gasifier in an integrated coal gasification combined cycle (IGCC) is established based on physical principles, focusing on the time-dependent accumulation and flow on the walls. Numerical simulations are carried out to explore the system dynamic performance with respect to step changes in the inlet oxygen-to-coal ratio and steam-to-coal. The dynamic responses of key outlet variables, including the gas temperature, exiting slag mass flow rate, thicknesses of the solid and fluid slag layer, volume percentages of H-2, CO2 and CO in syngas etc., are obtained. Three different coals are analyzed in this paper, and similar trends in their dynamic behaviors are found by using the gasifier model. The model and simulation method may be useful for providing insights to the operation and control of the IGCC process with respect to complex varying working conditions. (C) 2011 Elsevier B.V. All rights reserved.