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Entropy 2019, 21(4), 342; https://doi.org/10.3390/e21040342

Thermodynamic and Economic Analyses of Reformative Design for High Back-Pressure Heating in Coal-Fueled Cogeneration Units

1
National Thermal Power Engineering and Technology Research Center, North China Electric Power University, Beijing 102206, China
2
East China Electric Power Design Institute, Shanghai 200063, China
*
Author to whom correspondence should be addressed.
Received: 21 February 2019 / Revised: 24 March 2019 / Accepted: 26 March 2019 / Published: 28 March 2019
(This article belongs to the Special Issue Thermodynamic Optimization)
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Abstract

High back-pressure (HBP) heating technology has been identified as an effective approach to improve the efficiency of combined heat and power (CHP). In this study, the novel concept of a HBP heating system with energy cascade utilization is developed and its probability examined. In the reformative design, the extracted heating steam from the intermediate-pressure turbine (IPT) is first drawn to an additional turbine where its excess pressure can be converted into electricity, then steam with a lower pressure can be employed to heat the supply water. As a consequence, the exergy destruction in the supply water heating process can be reduced and the efficiency of the cogeneration unit raised. A detailed thermodynamic investigation was performed based on a typical coal-fired HBP–CHP unit incorporating the proposed configuration. The results show that the artificial thermal efficiency (ATE) promotion was as much as 2.01 percentage points, with an additional net power output of 8.4 MW compared to the reference unit. This was attributed to a 14.65 percentage-point increment in the exergy efficiency of the supply water heating process caused by the suggested retrofitting. The influences of the unit power output, unit heat output, supply water and return water temperatures and turbine back pressure on the thermal performance of the modified system are discussed as well. In addition, the economic performance of the new design is assessed, indicating that the proposed concept is financially feasible. View Full-Text
Keywords: combined heat and power; heating system; high back pressure; energy cascade utilization; thermodynamic analysis; economic analysis combined heat and power; heating system; high back pressure; energy cascade utilization; thermodynamic analysis; economic analysis
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Chen, H.; Wu, Y.; Xu, J.; Xu, G.; Yang, Y.; Liu, W.; Shi, G. Thermodynamic and Economic Analyses of Reformative Design for High Back-Pressure Heating in Coal-Fueled Cogeneration Units. Entropy 2019, 21, 342.

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