Optimization of Heat Recovery Steam Generator Operating Parameters

Abstract

Combined cycle power plant is one of the best design. It has higher eciency withrequirement of less men power. Thermodynamic analysis of plant includes Exergyanalysis. Exergy loss should be minimum for better performance of plant. Generationof steam in Heat Recovery Steam Generator (HRSG) is always associated with lossdue to irreversibility. Exergy analysis of the plant gives the best result. Here Exergyanalysis of combined cycle plant is done. The present work represents the engineer-ing design and theoretical exergy analysis of the combined cycle power plant. Exergyanalysis is performed based on the rst and second laws of thermodynamics for powergeneration systems. The results show that exergy analysis for a steam cycle systempredict the plant eciency more precisely. Power to heat ratio increases with an in-crease in pinch point, but the rst-law eciency and second-law eciency decreaseswith an increase in pinch point. The power to heat ratio and second-law eciencyincreases signicantly with increase in process steam pressure, but the rst-law ef-ciency decreases. Exergy analysis for 80% base load and 50% part load conditionhas been done from which it was found that 32.74% less exergy destruction at baseload than part load condition. Increasing the pinch points will decrease the combinedcycle plant eciency. The engineering design is based on natural gas preheating forincreasing the net power output and eciency, the fuel preheating technique can save1.10% of fuel energy and 1.09% of fuel than the old technique. The fuel consumptionrate is reduced by 1.1% when the fuel gas is preheated from 20 to 80 oC. For im-proving eciency of plant, pinch point and approach point should be kept optimum.To evaluate the energy utilization, one combined cycle unit and one co-generationsystem, consisting of gas turbine generator, heat recovery steam generator, one steamturbine generator have been analyzed. From pinch analysis eciency improved by5.16% and respectively electrical gross power generation improved by 32.91%.