Performance Comparison of 500 MW Coal-Fired Thermal Power Plants with Final Feedwater Temperatures

The final feedwater temperature is the temperature of the feedwater supplied to the boiler in the power plant applied with the Rankine cycle. In thermal power plants adopting a regenerative cycle, it is generally known that the heat transfer of the boiler is reduced, and the efficiency of the power plant is increased. However, the output of the power plant is reduced when the final feedwater temperature is increased. In this study, the net output and efficiency of the power plants depending on the final feedwater temperature under the condition of constant boiler heat transfer rate were analyzed for five cases. The results show that there is a final feedwater temperature at which the net output and the net efficiency are maximized. The additional output of the power plant obtained by increasing the final feedwater temperature has the effect of reducing CO2 emissions. If the final feed water temperature is below 308.3 °C, the net output and the final feed water temperature are proportional for all cases. When the final feedwater temperature increases by 1 °C, the net output increases by 63.02 kW and CO2 emissions are reduced by 60.52 kgCO2/h on average.