An integrated gasification combined cycle power generation system (100). In one embodiment, shown in FIG. 1, a gasifier (108) is configured to generate synthetic gas (117) from a carbonaceous material (106) and an oxygen supply (109) with a cleaning stage (120) positioned to receive synthetic gas (117) from the gasifier (108) and remove impurities therefrom. A gas turbine combustion system (2) including a turbine (123) is configured to receive fuel (128) from the gasifier (108) and a first air supply (131) from a first air compressor (130). A steam turbine system (4) is configured to generate power with heat recovered from exhaust (140) generated by the gas turbine system (2) and an ion transport membrane air separation unit (110) includes a second air compressor (114) for generating a second air supply (113). A first heat exchanger (118) is configured to cool the synthetic gas (117) prior to removal of impurities in the cleaning stage (120) by flowing the second air supply (113) through the first heat exchanger (118) so that the second air supply (113) receives heat from the synthetic gas (117).