Improvement of integrated gasification combined cycle performance using nitrogen from the air separation unit as turbine coolant

초록

An integrated gasification combined cycle (IGCC) power plant uses fuel made by coal gasification for gas turbines. The oxygen required for the gasification reaction is supplied using a cryogenic air separation unit (ASU), and a large amount of nitrogen is generated. In the conventional IGCC, nitrogen generated in the ASU is injected into the combustor to generate more power. However, since the temperature of the injected nitrogen is lower than that of the air supplied to the combustor, injecting nitrogen requires more fuel to maintain a constant outlet temperature (i.e., turbine inlet temperature (TIT)). We propose a novel system configuration to improve the performance of the IGCC and analyzed its effects. We used nitrogen generated in the ASU as a turbine blade coolant instead of compressed air. Since the nitrogen temperature was lower than the temperature of compressed air, the turbine blades can be protected with a lower flow rate of coolant. As a result, both the power and efficiency are increased. We also investigated possibilities for further performance improvement by changing design parameters and determined the design point that maximizes the efficiency.

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