Method and system for use with an integrated gasification combined cycle plant

#The field of the invention relates generally to an integrated gasification combined cycle (IGCC) system, and more particularly, to an IGCC system that includes an adiabatic axial air compressor.

#In at least some known IGCC power plants, hydrocarbonaceous feeds, including low value feeds, are reacted with high purity oxygen, such as approximately 95% oxygen purity, to produce combustion products, including syngas, at a temperature of about 2200° F. to about 2700° F. The resulting syngas is combusted within a combustion turbine to produce electric power.

#Moreover, in at least some known IGCC power plants, the oxygen is supplied by an air separation unit (ASU). More specifically, to supply the oxygen from the ASU, air supplied to the ASU is initially compressed using an intercooled air compressor. However, within known intercooled air compressors, thermal energy from each stage of cooling is transferred to cooling water rather than being used within the power plant. Such thermal energy is transferred rather than used within the plant because the thermal energy within the intercooled air compressor is generally below about 200° F. Moreover, the transfer of the thermal energy to the cooling tower requires additional power consumption by the cooling water circuit. Accordingly, a need exists for an IGCC power plant with improved heat efficiency. The embodiments described herein seek to improve the heat efficiency of an IGCC power plant.

#FIG. 1 is a schematic view of an exemplary integrated gasification combined cycle (IGCC) power generation plant.

#The methods and systems described herein include an adiabatic air compressor for supplying air to an air separation unit. The adiabatic air compressor generates a compressed heated air flow from which thermal energy is recovered within an integrated gasification combined cycle power generation plant. More specifically, in the exemplary embodiment, the compressed, heated air flow is used to heat a diluent nitrogen flow and to produce a medium pressure steam. As such, although an adiabatic air compressor consumes more power than known intercooled air compressors, the thermal energy of the adiabatically compressed air may be recovered, rather than rejected through a cooling tower. Accordingly, the method and system described herein improves overall efficiency of an integrated gasification combined cycle power generation plant as compared to integrated gasification combined cycle power generation plants that use an intercooled air compressor to supply air to an air separation unit.

#FIG. 1 illustrates a schematic view of an exemplary integrated gasification combined cycle (IGCC) power generation plant 10 (also referred to herein as “power plant” or “plant”). In the exemplary embodiment, plant 10 includes a gas turbine engine 12, a steam turbine 14, a gasification unit 16, and an air separation unit (ASU) 18. Gas turbine engine 12 includes a compressor 20, a combustor 22, and a turbine 24. In the exemplary embodiment, compressor 20 is an adiabatic axial flow type compressor, and turbine 24 is coupled in flow communication with a heat recovery steam generator (HRSG) 26, which supplies steam to steam turbine 14. HRSG 26 and steam turbine 14 are considered to be a steam cycle. Gasification unit 16 is coupled in flow communication with ASU 18 and combustor 22.

#Plant 10 also includes a nitrogen compressor 28, an adiabatic air compressor 30, a first heat exchanger 32, a second heat exchanger 34 a third heat exchanger 36, and a fourth heat exchanger 38. In an alternative embodiment, plant 10 does not include third heat exchanger 36 and/or fourth heat exchanger 38. In the exemplary embodiment, nitrogen compressor 28 may be a single or multi-stage intercooled compressor, and adiabatic air compressor 30 is an adiabatic axial air compressor. Alternatively, compressor 28 and/or compressor 30 may be any suitable compressor that enables plant 10 to function as described herein.