This paper investigates the effect of various gasification parameters and operating conditions on syngas composition. The gasification parameters include type of coal, oxygen and steam flow rates to the gasifier. The gasification process takes place in an entrained flow gasifier. Two gasifier models are developed with the Aspen Plus; one is based on the kinetics of the gasification obtained from experimental results reported in the literature, the second model is based on the Gibbs free energy. It was found that the kinetics based model had errors of 0.3%, 1.1%, and 2.7% by comparison, the Gibbs free energy based model exhibited an error of 4.1%, 6.5%, and 5.1% in the mole fraction of carbon monoxide, hydrogen, and carbon dioxide in the syngas respectively. Although the Gibbs free energy minimization approach based model produced slightly larger errors than the kinetics based model, the latter was chosen since the Gibbs model is more compatible with any coal type and with any combination of operating and input parameters. The latter model is used to find the effects of various gasification parameters and operating conditions on the resulting syngas composition. It is shown that the syngas composition is highly dependent on the flow rates of oxygen (gasification oxidant) and steam (gasification agent). The behavior of the syngas composition and hydrogen produced for three different types of coal is presented. Finally, the conditions leading to the maximum values of specific species in the syngas flow rates are presented. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.