Gas turbine combined cycle system

Abstract

In a combined cycle gas turbine configuration having at least two power blocks, stack emissions (particularly nitrous oxides or NOx but also carbon monoxide CO and unburned hydrocarbons, UHC) are controlled concurrently with part load power output. In one power block a combined cycle power plant has a relatively large heavy-duty industrial gas turbine fired to about 1,700° C. at the turbine inlet leading to a first heat recovery system. A second power block with a smaller gas turbine has a second heat recovery system. A controller adjusts coupling of flue gas and steam paths from the second power block to the first power block to meet load demand in compliance with applicable emissions regulations.

What is claimed is: 
     
         1 . A gas turbine combined cycle system comprising:
 (a) a first power block with a first gas turbine configured as a prime mover, a first heat recovery steam generator coupled to an exhaust path of the first gas turbine, and a steam turbine coupled to a steam outlet of the steam generator, the steam turbine being configured as a prime mover, wherein the first power block drives an electric generator;   (b) at least one additional power block with a gas turbine configured as a prime mover thermally coupled to a second heat recovery steam generator;   (c) wherein a controller is coupled to provide a flow of at least one of flue gas and steam from the additional power block to the first power block, said flow concurrently adjusting a power output of the first power block and a harmful emission level of the first gas turbine.   
     
     
         2 . The system of  claim 1 , further comprising a flue gas compressor, mechanically driven from one of an electric motor and a shaft of the gas turbine of the additional power block. 
     
     
         3 . The system of  claim 1 , wherein at least two of the prime movers are mechanically coupled to drive a single shaft coupled to the electric generator. 
     
     
         4 . The system of  claim 1 , comprising a multi-shaft configuration wherein each of the prime movers is coupled to a respective electric generator on a shaft. 
     
     
         5 . The system of  claim 1 , wherein the gas turbine prime mover of the first power block comprises a frame machine of one of an F, G, H or J class, with a firing temperature as high as 1,700° C. 
     
     
         6 . The system of  claim 1 , wherein the gas turbine prime mover of the at least one additional power block comprises an aero-derivative unit having a high cycle pressure ratio and high cycle efficiency, and a power output and airflow that is a fraction of that of the gas turbine prime mover of the first power block. 
     
     
         7 . The system of  claim 1 , wherein the flue gas compressor comprises a multi-casing unit with at least two casings, and further comprising intercooling between sections of the flue gas compressor. 
     
     
         8 . The system of  claim 1 , wherein flue gas from the heat recovery steam generator of the at least one additional power block is coupled to the first gas turbine at one of a gas turbine compressor inlet and a gas turbine combustor fuel inlet. 
     
     
         9 . The system of  claim 1 , wherein the second heat recovery steam generator is coupled to the first gas turbine at one or more entry locations on the turbine casing, so as to contribute cooling of components subjected to hot combustion gases. 
     
     
         10 . The system of  claim 1 , further comprising an aftercooler heat exchanger downstream of the flue gas compressor, wherein steam is heated before entry into a second gas turbine prime mover. 
     
     
         11 . The system of  claim 1 , wherein feed water from the second heat recovery steam generator is connected to a flue gas compressor intercooler for direct contact heat exchange between hot compressed flue gas from an upstream compressor section and said feed water. 
     
     
         12 . The system of  claim 10 , further comprising precooler and trim cooler water-to-flue-gas heat exchangers upstream and downstream of the flue gas compressor aftercooler, wherein said heat exchangers are configured to adjust flue gas compressor suction and discharge gas temperatures. 
     
     
         13 . A method for adjusting a load of a first gas turbine and related exhaust emissions thereof, comprising:
 apportioning flue gas from a second heat recovery steam generator between a compressor and combustor fuel inlet of the first gas turbine, steam flow to the first gas turbine for hot gas path component cooling and feed water flow to an intercooler of a flue gas compressor, including adjusting:   (a) flue gas flow from the second heat recovery steam generator to the first gas turbine compressor inlet;   (b) flue gas flow from the second heat recovery steam generator to the fuel gas compressor and, subsequently, to the first gas turbine combustor fuel inlet;   (c) steam flow and temperature to the first gas turbine, via an aftercooler;   (d) feed water flow from the second heat recovery steam generator to a fuel gas compressor intercooler;   (e) cooling water flow to a flue gas compressor precooler; and   (f) cooling water flow to a flue gas compressor trim cooler.   
     
     
         14 . The method of  claim 13 , further comprising coupling a controller to least the first gas turbine and associated flow paths for sensing operational parameters and wherein the apportioning comprises generating control outputs to associated valves. 
     
     
         15 . The method of  claim 13 , wherein said exhaust emissions comprise NOx, CO and UHC. 
     
     
         16 . The method of  claim 13 , wherein said adjusting is sequential along steps (a) through (f).