Exhaust gas temperature in coal-fired power plants can reach approximately 120 °C to 140 °C, with the thermal energy accounting for approximately 3% to 8% of the total input energy. Therefore, the heat recovery of exhaust flue gas can improve the thermal efficiency of coal-fired power plants. Currently, the waste heat of flue gas can be recovered by installing an extra heat exchanger, also called low-temperature economizer (LTE), at the end of the boiler flue to heat a part of the condensed water. Extra work can then be obtained by saving the extracted steam and using it to heat the condensed water. However, the temperature of exhaust flue gas is only about 130 °C, which causes the flue gas to heat only the condensed water in the #7 and #8 regenerative heaters. Thus, the energy savings are inconspicuous. This paper proposes a novel flue gas heat recovery system to dramatically increase the temperature of flue gas in the LTE by comprehensive optimization of the air preheater and the LTE. A low-temperature (LT) air preheater can be installed after the LTE in the novel system so that the flue gas can be divided into two parts to heat the air. Simultaneously, the LTE can be installed between the two air preheaters, causing the temperature of flue gas in the LTE to reach above 170 °C. Hence, the temperature of condensed water in the LTE can be increased significantly. In addition, the LTE can replace the high-pressure extracted steam from the turbine, resulting in better energy savings. We also conduct case studies based on a typical 1,000 MW supercritical power generation unit in China. The results indicate better performance of the novel system, with a decrease in exergy loss and improvement in heat transfer characteristics. The reduction in standard coal equivalent of the novel system can reach 3.31g/kWh, nearly 2.4 times that of the system that uses conventional waste heat recovery. Our achievements provide a promising waste heat recovery methods of the utility boiler flue gas.
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ASME Turbo Expo 2013: Turbine Technical Conference and Exposition
June 3–7, 2013
San Antonio, Texas, USA
Conference Sponsors:
- International Gas Turbine Institute
ISBN:
978-0-7918-5513-3
PROCEEDINGS PAPER
A Novel Flue Gas Heat Recovery System Integrated With Air Preheating in a Utility Boiler
Cheng Xu,
Cheng Xu
North China Electric Power University, Beijing, China
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Gang Xu,
Gang Xu
North China Electric Power University, Beijing, China
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Luyao Zhou,
Luyao Zhou
North China Electric Power University, Beijing, China
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Yongping Yang,
Yongping Yang
North China Electric Power University, Beijing, China
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Yuanyuan Li,
Yuanyuan Li
North China Electric Power University, Beijing, China
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Jianling Deng
Jianling Deng
China Huadian Corporation, Beijing, China
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Cheng Xu
North China Electric Power University, Beijing, China
Gang Xu
North China Electric Power University, Beijing, China
Luyao Zhou
North China Electric Power University, Beijing, China
Yongping Yang
North China Electric Power University, Beijing, China
Yuanyuan Li
North China Electric Power University, Beijing, China
Jianling Deng
China Huadian Corporation, Beijing, China
Paper No:
GT2013-95185, V002T07A021; 9 pages
Published Online:
November 14, 2013
Citation
Xu, C, Xu, G, Zhou, L, Yang, Y, Li, Y, & Deng, J. "A Novel Flue Gas Heat Recovery System Integrated With Air Preheating in a Utility Boiler." Proceedings of the ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. Volume 2: Aircraft Engine; Coal, Biomass and Alternative Fuels; Cycle Innovations. San Antonio, Texas, USA. June 3–7, 2013. V002T07A021. ASME. https://doi.org/10.1115/GT2013-95185
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