New operating strategy for a combined cycle gas turbine power plant

The highly dynamic nature of power demand forces a combined cycle gas turbine (CCGT) power plant to often run at less-efficient part-load conditions. A new operating strategy called EGR-IGVC is proposed in this work to improve the part-load performance of a CCGT plant. The strategy partially recycles the flue gas from the heat recovery steam generator and manipulates the inlet guide vanes to regulate part-load operation and boost plant efficiency. It allows the CCGT plant to set its own acceptable gas turbine temperature limits at any time and thus maximize the plant performance. Our previous CCGT flow diagram in Aspen HYSYS [Liu and Karimi (2018)] is modified to accommodate EGR for evaluating EGR-IGVC. Then, using a case study CCGT plant, EGR-IGVC is compared in detail with the conventional inlet guide vane control (IGVC). The results show that EGR-IGVC improves the plant part-load performance significantly. It increases the plant efficiency by up to 1.2% (actual) and reduces the CO2 emissions by up to 13.8 kg MW-1 h(-1). By enabling an effective utilization of low-temperature waste heat and reducing the propensity for NO formation, EGR-IGVC promises to be a better strategy for the part-load operation of CCGT plants.