Adapting Gas Turbines to Zero Emission Oxy-Fuel Power Plants

Abstract

Future power plants will require some type of carbon capture and storage (CCS) system to mitigate carbon dioxide (CO 2 ) emissions. The most promising technologies for CCS are: oxyfuel (O-F) combustion, pre-combustion capture, and postcombustion capture. This paper discusses the recent work conducted by Siemens Power Generation, Florida Turbine Technologies, Inc. (FTT) and Clean Energy Systems, Inc. (CES) in adapting high temperature gas turbines to use CES's drive gases in high-efficiency O-F zero emission power plants (ZEPPs). CES's O-F cycle features high-pressure combustion of fuel with oxygen (O 2 ) in the presence of recycled coolant (water, steam or CO 2 ) to produce drive gases composed predominantly of steam and CO 2 . This cycle provides the unique capability to capture nearly pure CO 2 and trace by-products by simple condensation of the steam.An attractive O-F power cycle uses high, intermediate and low pressure turbines (HPT, IPT and LPT, respectively). The HPT may be based on either current commercial or advanced steam turbine technology. Low pressure steam turbine technology is readily applicable to the LPT. To achieve high efficiencies, an IPT is necessary and efficiency increases with inlet temperature. The high-temperature IPT's necessitate advanced turbine materials and cooling technology. O-F plants have an abundance of water, cool steam ~200ºC (400ºF) and CO 2 that can be used as cooling fluids within the combustor and IPT systems.For the "First Generation" ZEPP, a General Electric J79 turbine, minus the compressor, to be driven directly by CES's 170 MW t high-pressure oxy-fuel combustor (gas generator), has been adapted. A modest inlet gas temperature of 760ºC (1400ºF) was selected to eliminate the need for turbine cooling. The J79 turbine operating on natural gas delivers 32 MW e and incorporates a single-stage free-turbine that generates an additional 11 MW e . When an HPT and an LPT are added, the net output power (accounting for losses) becomes 60 MW e at 30% efficiency based on lower heating value (LHV), including the parasitic loads for O 2 separation and compression and for CO 2 capture and compression to 151.5 bar (2200 psia). For an inlet temperature of 927ºC (1700ºF), the nominal value, the net output power is 70 MW e at 34% efficiency (LHV).FTT and CES are evaluating a "Second Generation" IPT with a gas inlet temperature of 1260ºC (2300ºF). Predicted performance values for these plants incorporating the HPT, IPT and the LPT are: output power of approximately 100-200 MW e with an efficiency of 40 to 45%.The "Third Generation" IPT for 2015+ power plants will be based on the development of very high temperature turbines having an inlet temperature goal of 1760ºC (3200ºF). Recent DOE/CES studies project such plants will have LHV efficiencies in the 50% range for natural gas and HHV efficiencies near 40% for gasified coal [ ] 1 .

Analiza termodynamiczna i techniczna zeroemisyjnej elektrowni dla pomorza

“…The gas-steam generator, into which the fuel, pure oxygen and water are injected, is a very important element of the cycle. In the presence of oxygen without nitrogen, the fuel burns at a much higher temperature than in traditional burning chambers; however, the temperature is decreased as the result of the evaporation of water [21]. There have already been modifications made to the GE J79 combustion chamber into gas-steam mixture generator, it works at a pressure of 11.6 bar and at 760 o C. In the secondgeneration power plant cycle, with use of the SGT900 both gas-steam mixture generator and turbine, due to the temperature is expected to rise up to 1080-1260 o C before the first stage turbine.…”

“…In paper [21], research results relating to the gas-steam turbine are presented; gas-steam is the working fluid of these turbines. The gas-steam generator, into which the fuel, pure oxygen and water are injected, is a very important element of the cycle.…”

“…It should be added, that Clean Energy Systems and the Siemens Corporation cooperate together to invent a large-scale, oxy-combustion power plant, which combines both gas and steam turbine operation [21]. In the literature, this cycle with oxy combustion and water injection is referred to as a water cycle [3,[19][20][21] because of the fact that steam makes up 90% of the content of mixture; the remaining 10% is carbon dioxide from methane combustion.…”

“…There have already been modifications made to the GE J79 combustion chamber into gas-steam mixture generator, it works at a pressure of 11.6 bar and at 760 o C. In the secondgeneration power plant cycle, with use of the SGT900 both gas-steam mixture generator and turbine, due to the temperature is expected to rise up to 1080-1260 o C before the first stage turbine. In the third generation gas-steam turbine, the work flux is expected to reach approximately 1650-1760°C and 40 bar [21].…”

“…In the literature, this cycle with oxy combustion and water injection is referred to as a water cycle [3,[19][20][21] because of the fact that steam makes up 90% of the content of mixture; the remaining 10% is carbon dioxide from methane combustion. A more sophisticated cycle which works on steam and enables reaching a higher level of efficiency is the GRAZ cycle [19].…”