Energy, Exergy and Environmental Impact Analyses of Barapukuria Coal Based Thermal Power Plant

Abstract

Energy and exergy analyses of Barapukuria 2x125 MW coal-based thermal power plant have been carried out in order to evaluate the energetic and exergetic efficiencies and losses of different components and the overall system of the plant. This coal fired power plant, consuming about 2,000 metric tons of coal, generates about 170 MW to 180MW of electricity every day against the installation capacity of 250MW. The energy supply to demand narrowing down day by day around the world. The growing demand of power has made the power plants of scientific interest, but most of the power plants are designed by the energetic performance criteria based on The First Law of thermodynamics only. The real useful energy loss cannot be justified by The First Law of thermodynamics, because it does not differentiate between the quality and quantity of energy. So, this present study deals with the comparison of energy and exergy analyses of coal based thermal power plants. The entire plant cycle has been split up into three zones for the calculation: (1) only the turbo-generator with its inlets and outlets, (2) turbo-generator, condenser, feed pumps and the regenerative heaters, (3) the entire cycle with boiler, turbo-generator, condenser, feed pumps, regenerative heaters and the plant auxiliaries. The analyses have been done considering design data (50%, 80%, 100% and 106% loading condition) and operation data (57% and 67% loading condition) of this power plant. The overall energy efficiencies of the plant were 35.48%, 56.77%, 70.96% and 75.67% and the overall exergy efficiencies were 44.25%, 33.31%, 30.78 % and 30.21% for 50%, 80%, 100% and 106% (above 100%) loading condition for the design data. But the overall energy and exergy efficiencies of the power plant at operation data are 39.2%, 46.6% and 27.9 %, 27.2% for 57% and 67% loading condition which are lower than the design value. The environmental impact of the power plants is also studied by using specific emissions of CO2, SOx, NOx and particulates. The distribution of the exergy losses in power plant components has been assessed to locate the process irreversibility. The comparison between the energy losses and the exergy losses of the individual components of the plant shows that the maximum energy losses of 49.92% occur in the condenser, whereas the maximum exergy losses of 68.27% occur in the boiler. The analyses have been also performed by inactivating heater one by one. Exergy analysis can be particularly effective in identifying ways to optimize the performance of existing operations and designing the plant while energy balance gives heat transfer between the system and its surrounding. Operation and maintenance decisions based on exergy analysis have proved to be more effective in reducing inefficiencies in operating power plant.