Exergoeconomic effect of adding a new feedwater heater to a steam power plant

¹ Faculty of Mechanical & Energy Engineering, Shahid Beheshti University, A.C., Tehran, Iran
² Department of Renewable Energies, Faculty of New Sciences and Technologies, University of Tehran, Tehran, Iran

^a Corresponding author : mohammadhosein.ahmadi@gmail.com

Received: 16 March 2016
Accepted: 13 September 2016

Abstract

Steam power plants play a key role in electricity generation throughout the world. Their performance is strongly dependent on the boilers performance and feedwater heater network. In this study, exergoeconomic analysis is performed on a steam power plant in Iran and effects of adding a new feedwater heater to the cycle are investigated through exergy and exergoeconomic analyses. In this respect, two configurations are considered, in the first one the new feedwater heater is placed before the first existing feedwater heater and in the second configuration, the new feedwater heater is placed after the last one. Performance of the system in these two new configurations is studied and then compared with the base case condition. Also an optimization algorithm is applied to each configuration and the base case condition. The results show that boiler has the highest rate of exergy destruction. Also in terms of exergoeconomic analysis, boiler has a high value of relative cost different which 45% of it is because of exergy destruction cost. Comparison between the results shows that adding the new feedwater heater increases the exergy efficiency of the plant, but if it placed after the last feedwater heater, it can reduce the product cost rate of the plant as well. Optimization results reveal that placing the new feedwater heater in this position can reduce the product cost rate by 0.16% and increase the exergy efficiency by 0.33%.