Optimization of Air Distribution to Reduce NOx Emission and Unburned Carbon for the Retrofit of a 500 MWe Tangential-Firing Coal Boiler

Hyunbin Jo, Kiseop Kang, Jongkeun Park, Changkook Ryu, Hyunsoo Ahn and Younggun Go
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Hyunbin Jo: School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Korea
Kiseop Kang: School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Korea
Jongkeun Park: School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Korea
Changkook Ryu: School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Korea
Hyunsoo Ahn: Doosan Heavy Industries and Construction, Youngin 16858, Korea
Younggun Go: Doosan Heavy Industries and Construction, Youngin 16858, Korea

Energies, 2019, vol. 12, issue 17, 1-20

Abstract: The use of separated overfire air (SOFA) has become a standard technique of air staging for NOx reduction in the coal-fired boiler and can also be applied to existing boilers by retrofit. This study was to optimize the air distribution for the proposed SOFA installation in a 500 MWe tangential-firing boiler that has 20 identical units in Korea. Using computational fluid dynamics (CFD) incorporating advanced coal combustion submodels, the reference case was established in good agreement with the design data, and different flow ratios of burner secondary air, close-coupled OFA (CCOFA), and SOFA were evaluated. Increasing the total OFA ratio effectively suppressed NO formation within the burner zone but had a negative impact on the boiler performance. With moderate air staging, NO reduction became active between the CCOFA and SOFA levels and, therefore, the OFA distribution could be optimized for the overall boiler performance. For total OFA ratios of 25% and 30% with respective burner zone stoichiometric ratios of 0.847 and 0.791, increasing the SOFA ratio to 15% and 20%, respectively, was ideal for decreasing the unburned carbon release and ash slagging as well as NO emission. Too high or low SOFA ratios rapidly increased the unburned carbon because of inefficient mixing between the strong air jets and char particles. Based on these ideal cases, the actual air distribution can be adjusted depending on the coal properties such as the ash slagging propensity.

Keywords: coal; combustion; computational fluid dynamics; boiler; overfire air; NOx emission (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: 2019
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (6)

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