A combined cycle process that includes gas turbines, a steam turbine train, a heat recovery unit, and a gasification unit that produces low or mid BTU fuel gas from coal, lignite, coke, biomass, or other suitable hydrocarbon containing material wherein the fuel gas is burned in the heat recovery unit at one or more points to increase steam rate to the steam turbine train.
The fuel gas injection flow rates into the heat recovery unit are controlled to avoid exceeding peak temperatures in the heat recovery unit of about 2500 F.
Optionally, the fuel gas from the gasification unit is cooled by transferring sensible heat to condensate from the steam turbine train to convert the condensate to high pressure steam for driving the steam turbine train.
Optionally, a steam boiler unit is integrated into the combined cycle process to raise additional high pressure steam for the steam turbine train. The steam boiler feed water is condensate from the steam turbine train. The steam boiler produces saturated high pressure steam that is superheated in the heat recovery unit.