A two-stage equilibrium model applicable to the wide range of operating conditions is developed to predict carbon conversion and composition of the product gas in an entrained-flow coal gasifier. The model is composed of two separate stages including char-gasification and gas-phase reaction. Carbon conversion is estimated in the first stage with solid-gas reactions, and then the product gas composition is calculated from gas-phase reactions in the second stage. Water consumption involved in the equilibrium reaction of the first stage is expressed as an exponential function of temperature. The model is validated with experimental data taken from literatures. It is confirmed that carbon conversion and product gas composition are influenced significantly by the oxygen to coal ratio. The optimum range of steam to coal ratio and the total yield of CO and H(2) depend on the type of coal and oxygen to coal ratio. (C) 2010 Elsevier Ltd. All rights reserved.