Advanced ASU and HRSG integration for improved integrated gasification combined cycle efficiency

A system for increasing efficiency of an integrated gasification combined cycle system comprising: an air separation unit for producing a nitrogen gas product stream and an oxygen gas product stream; a gasifier for producing a syngas stream in the gasifier using the oxygen gas product stream and coal; a mixing valve for forming a fuel mixture stream using the syngas stream and at least a portion of the nitrogen gas product stream; and a heated regenerative steam generator for providing heat for heating at least one of the oxygen gas product stream, the fuel mixture stream, or both.