Exergy Analysis of Pulverized Coal-Fired Ultra Supercritical Power Plants

Date
2013-08
Authors
Hasti, Sandhya
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Faculty of Graduate Studies and Research, University of Regina
Abstract

Demand for power generation has been increasing day by day and, along with it, a clean and efficient way of generating power is becoming more and more important. Apart from the electricity generated, the emission of the hazardous gases plays a vital role in the research field. The world’s power generation majorly depends on fossil fuels like coal and natural gases. Among power plants, pulverized coal-fired power plants are of great concern due to the relatively high emission of CO2 per MW of production. The modification of coal-fired power plants has been significantly used in reducing the emissions of particulate matter, like CO2, to the atmosphere. Analysis of the power generation systems is an expansive concept involving the efficient use of the energy resources. In the present scenario, it is important to focus on the stability of the power generation process. A study performed to analyze the stability of the system is known as exergetic analysis. This research deals mainly with the exergy analysis of coal-fired power plants operating in ultra supercritical conditions. The main steam conditions used for the model development are 750oC temperature and 35 MPa pressure. The primary objective of this study is to analyze the various working parametric conditions that lead to the highest exergy destruction. Exergetic analysis is a methodology for evaluation of the performance of components and involves examining the exergy at different points in a series of energy-conversion steps. The power plant model was validated using different operating conditions. The results showed consistent performance for the comparison made. A parametric study was conducted for different operating temperatures and pressures to determine the plant’s efficiency. The plant’s overall thermal efficiency was determined to be 55.23% with a net efficiency of 44.16% for a gross power output of 941.25 MW. The results obtained from the exergy analysis showed that the furnace had the highest exergy losses followed by turbine. The exergy loss in the furnace was 886.75 MW and that of the turbine was 67.34 MW. The results reveal that instability in the combustion process is the main reason for exergy loss in the furnace. Instability is due to the greater entropy generation. Increasing the preheated air temperature, maintaining the lowest possible moisture content in the coal, and decreasing the excess air percentage decreased the exergy destruction rate in the furnace. A detailed parametric study for the turbine to increase the exergetic efficiency was also conducted. It was observed that operating the power plant at ultra supercritical conditions yields a positive response regarding exergy losses.

Description
A Thesis Submitted to the Faculty of Graduate Studies and Research In Partial Fulfillment of the Requirements for the Degree of Master of Applied Science in Industrial Systems Engineering, University of Regina. xviii, 103 p
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