Exergy analysis of dual pressure HRSG for different dead states and varying steam generation states in gas/steam combined cycle power plant

This paper deals with exergy analysis of a dual pressure (DP) heat recovery steam generator (HRSG) having steam generation at high pressure (HP) and low pressure (LP) in the range of 50-70 bar and 2-6 bar respectively in the gas/steam combined cycle power plant for varying dead states. The in-operation plant data for this study are taken from a gas/steam combined cycle power plant at Auraiya (U.P.), India. Results have been obtained for exergy loss and exergy efficiency with varying dead state temperatures for different HP and LP steam generation states in different sections of HRSG. The exergy analysis for chosen conditions/parameters helps in locating the particular sections of the HRSG having maximum exergy loss. It is found that at varying steam generation pressures the HP and LP super heater sections and at higher dead state temperatures the HP evaporator are found to act as major source of irreversibilities. The results obtained are useful in finding the thermodynamic states that will help in reducing the exergy destruction for enhancing HRSG performance which eventually improves the efficiency of combined cycle power plants.