Performance analysis and optimization of a NGCC-CHP plant with low pressure economizer partial recirculation system

Abstract In this paper, the performance of a natural gas combined cycle (NGCC) power plant operating in combined heat and power (CHP) mode is analyzed, and the optimization of partial recirculation system is conducted. In order to compare the plant performances between complete and partial recirculation systems, the simulations of NGCC-CHP plants with both systems are performed. Base on the off-design characteristics of both systems, the optimal operating strategies are proposed to achieve energy utilization efficiency. The comparisons on thermodynamic performance and operational flexibility between the plants with both systems are performed. Results show that in contrast with the complete recirculation system, the partial recirculation system can improve the energy utilization efficiency of the NGCC-CHP plant by 0.48–0.58% at various conditions. More waste heat can be recovered from flue gas under the limitation of dew point corrosion. Moreover, the heat generation capacity of the plant increases and the operational gap between extraction-condensing mode and backpressure mode of the plant shrinks. The plant achieves the decoupling between power generation and heat generation at backpressure mode. The combined heat and power operational continuity and flexibility of the plant with partial recirculation system is superior to that with complete recirculation system.