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Exergy analysis has been found to be a useful method for improving the conversion efficiency of energy resources, since it helps to identify locations, types and true magnitudes of wastes and losses. It has also been applied for other purposes, such as distinguishing high- from low-quality energy sources or defining the engineering technological limits in designing more energy-efficient systems. To identify locations, types, and actual magnitudes of energy losses; exergy analysis has been found to be a valuable way for enhancing the conversion efficiency of the different energy systems. The aim of this research is to analyze the effect of the operation conditions on the performance of coal-fired power plants. As well, this study focuses on the effect of different feedwater heaters' numbers that lead to the highest exergy destruction of the coal-fired power plants. For different values of the superheated steam temperature and the pressure, a parametric study was conducted to determine the efficiency of the coal-fired power plant. The results show that, when the pressures and temperature of the superheated steam increases the evaporator temperature will increases too. Increasing the temperature of evaporator rises the average maximum temperature of the cycle, which improves the thermal efficiency of the cycle as well as the powerplant efficiency. The results show that, at higher boiler pressures and temperatures, the temperature difference between the water/steam and hot gases of the boiler is reduced which means the irreversibility associated with the heat transfer process decreases. Therefore, by increasing the pressure and temperature of the superheater, the exergy efficiency of the thermal cycle is improved. It was observed that operating the coal-fired power plant at high superheated pressure and temperatures produce lead to reduce the exergy losses.

This study aims to investigate the feasibility of using a feedwater heaters system with coal-fired power plant. Furthermore, the influence evaluation of the different coal consumption on the coal-fired power plants in terms of power output and thermal efficiency improvements. As well, this study focuses on the effect of different feedwater heaters' numbers which caused the highest exergy destruction of the coal-fired power plants. For different values of the coal consumption, a parametric study was conducted to determine the efficiency of the coal-fired power plant. The results show that, when the coal consumption increases the power output will increases too. The slight decreases in the efficiencies are due to the small differences in how the mass flow rates of different streams increase. The exergy destruction was increased by about 16% when the consumption of fuel increases by 40 kg/s. It was observed that operating the coal-fired power plant at high coal consumption leads to reduce the effective ness of the feedwater heaters and increases the power output.