Patent Application
20090301054
The present invention relates to a turbine system having a gas turbine with a reheat combustion system and an exhaust gas recirculation (EGR) system for the reduction of thermal NOx.
As concerns over the environmental impact of industrial emissions have increased, so too have the restrictions on allowable emissions. Large gas turbine systems are of a particular concern due to the considerable quantities of fuel required to meet electricity demands. A number of combustion schemes have been developed to reduce emissions that result from the high turbine firing temperatures currently in use on most commercial systems. Some of these combustion schemes include premixed combustion, staged combustion, atomized liquid fuel, injection of various diluents, catalytic combustion, exhaust gas recirculation (EGR), and reheat combustion.
In a typical reheat turbine system, the reheat combustor is located downstream of the primary combustor and provides typically greater efficiency and lower emissions. EGR is often used to reintroduce exhaust gases into a section of the turbine, such as the inlet or the combustion chamber, in order to improve emissions benefits by lowering temperature in high temperature gas pockets and also reducing oxygen concentration.
In one embodiment, a turbine system comprises a first compressor configured to compress gases; a first combustor configured to mix the compressed gases with fuel and burn the mixture; a first turbine configured to be driven by combustion gases of the first combustor; a second combustor configured to mix exhaust gases from the first turbine with fuel and burn the mixture; a second turbine configured to be driven by combustion gases from the second combustor; and a generator configured to be driven the turbine system. A first portion of the exhaust gases from the second turbine is recirculated for mixing in the first combustor.
In another embodiment, a method of operating a turbine system comprises compressing gases with a first compressor; mixing the compressed gases with fuel to form a first mixture and burning the first mixture; driving a first turbine with combustion gases from burning the first mixture; mixing exhaust gases from the first turbine with fuel to form a second mixture and burning the second mixture; driving a second turbine with combustion gases from burning the second mixture; and recirculating a first portion of the exhaust gases from the second turbine into the first mixture.
In a further embodiment, a turbine system comprises a plurality of compressors, each compressor configured to compress gases; a plurality of combustors, each combustor configured to mix compressed gases with fuel and burn the mixture; a plurality of turbines, each turbine configured to be driven by combustion gases of at least one of the plurality of combustors; and a generator configured to be driven by the turbine system. Portions of the exhaust gases from at least some of the turbines are recirculated and introduced into at least some of the compressors.
Referring to
The amount of air provided to the primary combustor 10 by the compressor 6 exceeds the amount of air necessary for combusting the fuel 12. The combustion gases 14 from the primary combustor 10, which includes the excess air, are fed to a high pressure turbine 16 which is connected to the compressor by the shaft 36. The high pressure turbine exhaust gas 18 is fed to a secondary, or reheat, combustor 20 and mixed with fuel 22. The combustion gases 24 from the secondary combustor 20 are fed to a low pressure turbine 26 which is connected to the high pressure turbine 16, the compressor 6, and the generator 4 by the shaft 36. The connection of the generator 4, the compressor 6, the high pressure turbine 16, and the low pressure turbine 26 allows the components to run at the same speed.
The low pressure turbine exhaust gases 28 are divided into atmosphere exhaust gases 30 and recirculated exhaust gases 32. The atmosphere exhaust gases 30 are exhausted to the atmosphere, for example, through an optional heat exchanger (not shown).
The recirculated exhaust gases 32 are fed through a heat exchanger 34 and the cooled, uncompressed recirculated exhaust gases 33 are then fed into the compressor 6 with the inlet air 8. The heat removed from the recirculated exhaust gases 32 by the heat exchanger 34 may be used to operate a steam turbine apparatus, for example, so that the system may be a combined cycle system.
Referring to
As shown in
A second portion 35 of the low pressure turbine exhaust gases 28 may be routed to a HRSG (heat recovery steam generator) 80. The HRSG 80 generates steam to operate a steam turbine 82 so that the system may be a combined cycle configuration. It should be appreciated that any of the embodiments described herein may be provided with a HRSG and steam turbine to provide a combined cycle configuration.
Referring to
Referring to
The low pressure compressor 54, the low pressure turbine 26 and the generator 4 are supported by a common shaft 58. A second shaft 60 connects the high pressure compressor 56 and the high pressure turbine 16 to ensure that the high pressure compressor 56 and the high pressure turbine 16 rotate at the same speed.
As shown in
The compressor 6, the high pressure turbine 16, and the recirculated exhaust gas compressor 68 are connected by a first shaft 64. The low pressure turbine 26 and the generator 4 are connected by a second shaft 66 that ensures that the low pressure turbine 26 and the generator 4 rotate at the same speed.
Referring to
The compressor 6 and the high pressure turbine 16 are connected by a first shaft 74 to ensure that primary compression is powered by the high pressure turbine 16. The mid-pressure turbine 70 and the recirculated exhaust gas compressor 68 are supported by a second shaft 76. The low pressure turbine 26 and the generator 4 are connected by a third shaft 78 that ensures that the two components rotate at the same speed.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
