Evaluation of Design Performance of the Semi-Closed Oxy-Fuel Combustion Combined Cycle

This study aims to present various design aspects and realizable performance of the natural gas fired semi-closed oxy-fuel combustion combined cycle (SCOC-CC). The design parameters of the cycle are set up on the basis of the component technologies of today’s state-of-the-art gas turbines with a turbine inlet temperature between 1400 °C and 1600 °C. The most important part of the cycle analysis is the turbine cooling, which considerably affects the cycle performance. A thermodynamic cooling model is introduced in order to predict the reasonable amount of turbine coolant needed to maintain the turbine blade temperature of the SCOC-CC at the levels of those of conventional gas turbines. The optimal pressure ratio ranges of the SCOC-CC for two different turbine inlet temperature levels are researched. The performance penalty due to the CO₂ capture is examined. The influences of the purity of the oxygen provided by the air separation unit on the cycle performance are also investigated. A comparison with the conventional combined cycle, adopting a postcombustion CO₂ capture, is carried out, taking into account the relationship between the performance and the CO₂ capture rate.