in the embodiment of fig3 a power generation system 300 provides a method of pre heating compressed air prior to entering an asu with a closed loop heat exchange system using an intermediate working fluid heated by gas turbine exhaust the system 300 comprises a gas turbine system 2 a hrsg 3 a steam turbine system 4 as described with respect to fig1 and a gasification system 6 the gasification system 6 includes a gasifier 308 which receives a fuel source 306 and an oxygen supply 309 from an itm asu 310 hot syngas 317 generated in the gasifier 308 is cooled in a syngas cooler 318 using a portion 191 of feed water 167 exiting the steam turbine system 4 before the syngas enters a gas cleaning stage 320 for removal of impurities e g sulfur nitrous compounds and dust particles in the syngas cooler 318 the cooling water 191 is converted to steam 392 which is sent to the steam chest 152 the cleaned syngas 324 is mixed with steam 126 from the steam chest 152 to form a fuel mixture 328 which flows through a fuel supply line 325 to the manifold 123 and into the gas combustor 132 of the gas turbine system 2 in the gasification system 6 a compressor 314 driven by a motor 316 provides compressed air 313 from a source of ambient air 315 the compressed air 313 may be delivered from the stand alone compressor 314 shown in fig3 or from a compressor 130 of the gas turbine system 2 or from another source in the heat exchange system 11 the compressed air 313 flows through an air pre.