Operational optimization of turbo-generator (TG) cycle of a 500MW coal-fired thermal power plant

Energy efficient, environmental friendly and economically viable power supply is the primary goal of any country. Higher plant performance is directly linked with clean and economic power generation. To optimize the plant performance, energy and exergy analyses play a crucial diagnostic tool to take proper operation and maintenance (O&M) decisions. In the present study, the effect of sliding pressure control mode of operation over constant pressure mode on plant performance of a 500MW coal-fired Indian subcritical thermal power plant at different load conditions (100%, 80% and 60% of the rated load) is discussed. Energy and exergy analyses disclose that at part load operation, the plant performance deteriorates due to poor performances of boiler and turbo-generator (TG) cycle. Performance gap between sliding pressure and constant pressure control mode is found more prominent at lower operating load. Quality energy losses due to mixing of feed water at different temperature in common outlet header of high pressure feed water heaters and its effect on plant performance are studied with respect to different operational combination of high pressure heaters (HPHs) in service. The performance of HPH#6 and its effect on plant are also studied by withdrawing HPH#5 from service. Result shows that only HPH#6 should not be taken into service for its remaining safe life and poor performance. But the individual bypass valves of HPH#6A&6B can be used for taking HPH#5A&5B in service to get better plant performance with respect to individual or total series bypass.