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%.
Highlights
Electricity is an important form of energy the generation of which is increased in the last decades, due to population growth and improved technology
Exergy destructed in feedwater heaters and pumps are negligible compared to the other components as they are responsible for only 1.5% of total exergy destruction
The results show that performing the optimization reduces the product cost rate of the plant by 2.42%, while exergy efficiency of the plant decreases simultaneously by 0.26% which again shows the conflict nature of the two selected objective functions
Summary
Electricity is an important form of energy the generation of which is increased in the last decades, due to population growth and improved technology. The main focus of their work was to study the effect of vapor quality at steam turbine outlet They considered three different objective functions including exergy efficiency, total cost rate of the system product and the CO2 emission. Khanmohammadi et al [18] performed an exergoeconomic analysis on a steam power plant in Iran and calculated the cost of exergy destruction in each component They studied the effect of main steam temperature, reheated steam temperature, condenser pressure and number of the feedwater heaters on the cycle performance. They showed that increasing the number of feedwater heaters leads to a decrease in the electricity price. Using a sensitivity analysis, the most effective parameters on the system performance are identified and an optimization analysis is performed on the system to find the best achievable performance
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