Oxy-Fuel Gas Turbine Technology
New gas turbine power cycles using oxygen instead of air with controlled addition of diluents such as steam and/or carbon dioxide (CO2) are being investigated. These advanced gas turbines are being developed for a variety of fuels, such as hydrogen, syngas, natural gas, and other liquids.
The major factors impacting the efficiency of these cycles are working fluid temperature at the inlet of the turbine, turbine cooling demand, oxygen and CO2 compression efficiencies, and Air Separation Unit (ASU) parasitic load.
Many gas turbine power cycles and their variants have been proposed in recent years, including semi-closed oxy-fuel gas turbine combined cycle, and integrated solid-oxide fuel cell (SOFC)/gas turbine cycle.
Semi-Closed Oxy-Fuel Gas Turbine Combined Cycle
In a semi-closed oxy-fuel gas turbine combined cycle, pressurized oxygen and fuel are combusted in a gas turbine combustor. The combustion products, mainly CO2 and water, are then expanded in a high-pressure turbine prior to being sent to a Heat Recovery Steam Generator (HRSG), where steam is produced and subsequently expanded in a steam turbine. Once the water is removed in a downstream condenser, the remaining flue gas is a CO2-rich stream that is proportionally bled off for compression and storage. The remaining portion is recycled back to the CO2 compressor to moderate the combustion temperature in the pressurized combustor.
CanmetENERGY has been leading the development of Oxy-Fuel Turbine technology in collaboration with Carleton University for the past several years. The work on the Raven Zero-Emission Gas Turbine at Carleton University was focused on the design and construction of a 50 kWe natural gas–fired system using pure oxygen combustion with CO2 re-circulation. The modeling, analysis, and design of a 100 MW semi-closed oxy-fuel gas turbine combined cycle were conducted as the scale-up version of the 50 kWe micro turbine system.
Integrated Solid-Oxide Fuel Cell/Gas Turbine Cycles
The integrated solid-oxide fuel cell (SOFC)/gas turbine cycle is a hybrid power cycle combining an SOFC and a gas turbine. In this cycle, the SOFC acts as a combustor and the pressurized air required for its operation is provided by the gas turbine compressor. The exhaust from the SOFC is then expanded in the turbine to yield a dry hybrid cycle power system. The thermal energy for the cycle can come from combustion of natural gas or clean syngas. This system concept can be expanded to include the oxy-fuel combustion process in this integrated cycle.
CanmetENERGY has been conducting performance evaluations of various gas turbine and fuel cell–based cycles utilizing oxy-fuel combustion for power generation and CO2 capture. Work is underway at the University of Waterloo to model and develop a simulation of SOFC, which can be integrated into a gas turbine bottoming cycle.
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