Recovering Low-Grade Heat from Flue Gas in a Coal-Fired Thermal Power Unit

Linbin Huang, Guoqing Chen, Xiang Xu, Rui Tan, Xinglong Gao, Haifeng Zhang and Jie Yu ()
Additional contact information
Linbin Huang: State Key Laboratory of Low-Carbon Smart Coal-Fired Power Generation and Ultra-Clean Emission, Nanjing 210023, China
Guoqing Chen: State Key Laboratory of Low-Carbon Smart Coal-Fired Power Generation and Ultra-Clean Emission, Nanjing 210023, China
Xiang Xu: State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074, China
Rui Tan: Guoneng Nanjing Electric Power Testing and Research Co., Ltd., Nanjing 210046, China
Xinglong Gao: Guoneng Changzhou Secondary Power Generation Co., Ltd., Changzhou 213000, China
Haifeng Zhang: Guoneng Changzhou Secondary Power Generation Co., Ltd., Changzhou 213000, China
Jie Yu: State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074, China

Energies, 2024, vol. 17, issue 20, 1-11

Abstract: To achieve the goals of carbon peaking and carbon neutrality, the retrofitting of existing coal-fired power plants is crucial to achieving energy-saving and emission reduction goals. A conventional recovery system of waste heat typically occurs downstream of the air preheater, where the energy quality in flue gas is low, resulting in limited coal-saving benefits. This study proposes a scheme involving a flue gas exchanger bypassing the air preheater and low-temperature economizers, which is used to transfer the waste heat from flue gas to primary and secondary air (System I). Additionally, a heat pump can be introduced to provide supplementary energy for primary and secondary air, as well as the condensate from the steam turbine (System II). The coal consumption rate and exergy efficiency are used to evaluate the two schemes. The results show that both waste heat recovery systems can increase the power output of the coal-fired unit by recovering waste heat. System II can boost power output by approximately 13.98 MW. The power increase in both waste heat recovery systems show a declining trend as the unit load decreases. This increased power is primarily attributed to the medium- and low-pressure cylinders, while the contributions from ultra-high-pressure and high-pressure cylinders are negligible. The increased power output for the medium-pressure cylinder ranges from approximately 3.49 to 3.58 MW, while the low-pressure cylinder has an increased power output of around 10.10 to 10.19 MW. The coal consumption rate is decreased from 250.3 g/(kW·h) to 247.5 g/(kW·h) under a full load condition for both systems, which can be augmented at lower load conditions. System II outperforms System I at 30% load condition, achieving a reduced coal consumption rate of 3.36 g/(kW·h). System I has an exergy efficiency of 40%, while System II shows a higher efficiency of 44%.

Keywords: waste heat utilization; air preheater bypass; heat pump; exergy efficiency; coal consumption rate (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
References: View references in EconPapers View complete reference list from CitEc
Citations:

Downloads: (external link)
https://www.mdpi.com/1996-1073/17/20/5204/pdf (application/pdf)
https://www.mdpi.com/1996-1073/17/20/5204/ (text/html)

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:gam:jeners:v:17:y:2024:i:20:p:5204-:d:1502126

Access Statistics for this article

Energies is currently edited by Ms. Agatha Cao

More articles in Energies from MDPI
Bibliographic data for series maintained by MDPI Indexing Manager ().