Enhancement of efficiency for steam cycle of thermal power plants using process integration

Highlights: • Pinch analysis of streams in steam cycle is discussed. • Six schemes were proposed to increase the efficiency of steam cycle. • Schemes are based on use of heat transfer across the pinch and boiler blowdown. • The deletion of LPH-1 in LP turbine is discussed in detail in various schemes. • Exergy analyses of steam cycle before and after modifications discussed in detail. -- Abstract: In this study, pinch analysis is employed to integrate energy in steam cycle of a 250 MW thermal power plant (TPP) located in Rajasthan state of India. To apply pinch analysis on steam turbine, all extractions exiting the turbine are considered as hot utility and feedwater as cold utility. Pinch analysis shows the potential savings in hot and cold utilities as 9.66% and 0.77%, respectively. Considering heat transfer across the pinch in condenser, heat available in boiler blow down and flowrates of extraction of low pressure (LP) turbine, six different energy integration schemes are proposed. Results show that extraction of LP turbine entering to LPH-1 is eliminated, which saves steam extracted from turbine for preheating the feedwater and thus, extra power is generated. It is also seen that flowrates from other two extractions of LP turbine decrease marginally. Amongst six energy integration schemes, the best one indicates that using pinch analysis, net generated power is increased by 0.55% and demineralized water demand is reduced by 57.6%. Further, exergy analysis of steam cycle is carried out and compared with that of most suited retrofitted scheme. Results of the present study are compared well with that of published literature.