The examination of a natural gas combined cycle power plant by exergy analysis

In this study, energy and exergy analysis were performed by using data from gas turbines, steam turbines and boiler operation reports of the 1st unit of the Natural Gas Combined Cycle Power Plant. The unit that is examined at the plant has two gas turbine cycles and one steam turbine cycle. From the molar fractions obtained by the equilibrium of the combustion reaction, from the thermodynamic tables and relations, enthalpy, physical and chemical exergy values of air, fuel, exhaust gases, water-steam cycle nodes were calculated. Thus, energy-exergy values of each node were determined and mass, energy and exergy equilibrium equations were applied to each component loss heat and irreversibility were calculated. By using these calculations, energy and exergy balance sheets were prepared and the heat loss percentages of the components according to the fuel energy and the irreversibility percentages according to the fuel exhaustion were compared. Rationality by calculating the irreversibility of the components yields were found. According to this; It was determined that the power plant has a thermal efficiency of 47.2%, gas turbine cycle efficiency of 31.0%, a steam turbine cycle efficiency of 30.5% and a plant exergy efficiency of 45.7%. The most energy loss in the condenser and the chimney, the highest irreversibility was observed in the combustion chamber with 27.8% and in the gas turbine with 9.4%. Gas turbine cycle irreversibility accounts for 43% of fuel exclusion and 80% of total irreversibility. For this reason, it was concluded that the gas turbine cycle should be focused in the improvement works to be performed in the plant. In the conclusion part, suggestions for reducing the energy loss on the compressor and increasing the plant efficiency were evaluated. In addition, if some cooling is applied to the compressor, the change in net energy and efficiency is investigated.