Relevance Of Exergy Analysis In The Assessment Of Thermal Power Plant Performance
Keywords:
Exergy, energy, thermal power plant, efficiency, irreversibility, units and subsystemsAbstract
Exergy analysis of a natural gas based thermal power plant at Egbin, Ikorodu, Lagos State, was done to: evaluate the exergy and energy efficiencies and irreversibilities of units, subsystems and overall system; identify the units with large thermodynamic irreversibilities and investigate the causes of irreversibilities in the units and how they can be minimized; study the effect of interaction of units on the performance of subsystems and overall system. Process simulation was done using HYSYS, commercial process simulator software, and exergy analysis was done using Microsoft Excel Spreadsheet. It was found that the condenser unit has the lowest exergetic efficiency and the highest energetic efficiency of 22.6% and 99.9%, respectively. The furnace/boiler unit was found to have the highest irreversibility of 1484.3 MW and the regenerative unit has the lowest irreversibility of 9.7 MW. The study of the units interaction revealed that the furnace/boiler unit made the highest contribution of about 67% to the overall process irreversibility while the least contribution of 9.7% came from the turbines/generator unit. It was found that the optimum natural gas mass flow rate which optimized the flue gas temperature and CO2 emission was 40,000 kg/h rather than the operating rate of 45,570 kg/h.
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