In the Shell coal gasification process, the syngas produced in a gasifier passes through a syngas cooler for steam production and temperature control for gas cleaning. Fly slag present in the syngas may cause major operational problems such as erosion, slagging, and corrosion, especially in the upper part of the syngas cooler (gas reversal chamber, GRC). This study investigates the flow, heat transfer and particle behaviors in the GRC for a 300 MWe IGCC process using computational fluid dynamics. Three operational loads of 100%, 75% and 50% were considered. The gas and particle flows directly impinged on the wall opposite to the syngas inlet, which may lead to erosion of the membrane wall. The heat transfer to the wall was mainly by convection which was larger on the side wall at the inlet level due to the expansion of the cross-section. In the evaporator below the GRC, the particles were concentrated more on the outer channels, which needs to be considered for alleviation of fouling and blockage.