Thermodynamic modeling and parametric study and exergy optimization of single, dual and triple pressure combined cycle power plants (CCPP)

In the present study, three different configurations of CCPP have been investigated. Hence, for a given gas turbine cycle, three different HRSG cycle configurations are chosen and parametric analysis is carried out based on exergy analysis to see the effects of main cycle parameters on cycle efficiency. These are single pressure HRSG cycle, dual pressure HRSG cycle and triple pressure HRSG cycle. In single pressure cycle, HRSG generates steam at one pressure level. In dual pressure cycle, HRSG generates steam at two different pressure levels (high and low pressure). In triple pressure cycle, HRSG generates steam at three different levels (high, intermeddle and low). In this paper, second law analysis is performed to able to see exergy destruction throughout the steam plant; in addition second law efficiency values are obtained for single, dual and triple pressure steam cycle configurations as well as basic steam power cycle with reheat. It´s shown from results that maximum lost work due to irreversibility is in HRSG for a steam cycle in a single pressure HRSG cycle. Comparing this with the single pressure cycle shows how the dual pressure and triple pressure cycles makes better use the exhaust gas in the HRSG that dual pressure and triple pressure combined cycle power plants has highest efficiency values and lost work due to irreversibility in most significant component HRSG can be lowered. The results also show that combustion chamber is the main source of irreversibility due to the higher temperature difference.