Advanced exergy and environmental analyses and multi objective optimization of a real combined cycle power plant with supplementary firing using evolutionary algorithm

This paper deals with an advanced exergy analysis and optimization of a real CCPP (combined cycle power plant) with DBs (duct burners) located in Iran. The endogenous/exogenous exergy destruction parts of each component as well as their combinations with avoidable/unavoidable parts are determined. A parametric study is carried out to assess the sensitivity of total avoidable exergy destruction and CO2 emission to TIT (turbine inlet temperature), compressor pressure ratio (rc) and DB fuel mass flow rate (m˙DB). Parametric results reveal that the increments in TIT and rc improve the CO2 emissions by about 6.8% and 17%, respectively and the total avoidable exergy destruction rate increases within 19% when rc is in the range of 9-14. In addition, NSGA-II (Non-dominated Sort Genetic Algorithm-II) is applied to obtain the final solutions in the multi-objective optimization of the CCPP. The optimum value of total avoidable exergy destruction rate and CO2 emission indicates 10.6% and 8.3% improvements, respectively, relative to the base case. Furthermore, the values of TIT and m˙DB decrease to 1.7% and 32.5%, respectively and rc increases 38% compared with the base case.