Retrofit of a 600 MW Down-Fired Pulverized-Coal Furnace for Low NOx Emission

Tao Liu, Sheng Wang, Ziming Wei and Jie Yu ()
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Tao Liu: State Key Laboratory of Low-Carbon Smart Coal-Fired Power Generation and Ultra-Clean Emission, Nanjing 210023, China
Sheng Wang: State Key Laboratory of Low-Carbon Smart Coal-Fired Power Generation and Ultra-Clean Emission, Nanjing 210023, China
Ziming Wei: State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074, China
Jie Yu: State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074, China

Energies, 2023, vol. 16, issue 19, 1-16

Abstract: Aiming at solving the problem of high NOx emissions of a down-fired boiler, a new combustion system has been proposed by means of the numerical simulation using Ansys Fluent. The coal-lean stream (tertiary air), which was originally mixed with a separated overfired air (SOFA) stream on the front and rear walls of the upper furnace, was relocated to the lower zone of the furnace after retrofit. The secondary-air slots were transformed into a new annular port type, which was injected into the furnace with a down-tilt angle to increase the residence time of the coal stream. Furthermore, the effect of secondary air distribution and velocity of coal stream on performance was studied. After retrofitting the combustion system, the NO emissions were effectively controlled, decreasing from 906 mg Nm −3 to 576 mg Nm −3 , but the carbon content of fly ash increased from 2.46% to 5.78%. Aiming at decreasing the carbon content of fly ash, the effect of coal/primary air velocity on the arch was studied. Less carbon content in fly ash can be observed for the lower arch airflow velocity. The results showed that the NO emissions can be controlled below 595 mg Nm −3 , and the carbon content of fly ash was reduced to 3.39% when the velocity was decreased to 18 m s −1 .

Keywords: down-fired furnace; NOx; combustion efficiency; simulation; air distribution (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: 2023
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