Comparison of performance of the integrated gas and steam cycle (IGSC) with the combined cycle (CC)

摘要

The clear advantages of the gas turbine engine are making it the engine of the future in electric power generation. Some combined cycle power plants are breaking the 60% efficiency barrier. One of the key technologies for such high thermal efficiency is steam cooling. In the integrated gas and steam cycle (IGSC), part of the steam generated in the heat recovery boiler (HRB) is used in the gas turbine as the cooling medium instead of air, whereas the other part is used as process steam. In the analysis, the compressor pressure ratio #gamma#_c and the turbine inlet temperature were considered the main variables. A computer program was specially tailored to carry out calculations and evaluate performance over a wide range of operating conditions including the design point. Performance results show that, when the cooling air is disregarded, the combined cycle (CC) produces 7% more power than IGSC, whereas the latter outperforms the CC by about 6% in SFC_(ov) and 12% in #eta#_(ov). However, when 5% cooling air is considered, the IGSC outperforms the CC by 2%, 12% and 20%, respectively (in points). Moreover, considerable saving in capital cost is achieved by dispensing with the steam turbine, condenser and cooling tower needed by the CC.