This study investigates the steady state operation and performance of a 253 MW Integrated Coal Gasification Combined Cycle (IGCC) that is based on the design and operating parameters of the existing Willem-Alexander plant in Buggenum, the Netherlands. For further performance optimization of such plants, an extensive base case model of the IGCC is developed and validated with actual process data. The model accurately predicts the mass flows, temperatures and pressures as well as a net efficiency of 42%. Exergy losses are experienced to the greatest extent in the gasifier and the combustion chamber of the gas turbine which indicates that efficiencies of mature IGCC's could be further optimized. To enhance the environmental performance of IGCC's, the specified model can be employed to simulate alternatives for biomass co-gasification and carbon capture technologies. (C) 2015 Published by Elsevier Ltd.