Reduction of Unburned Carbon Release and NO x Emission from a Pulverized Wood Pellet Boiler Retrofitted for Fuel Switching from Coal

Jiseok Lee, Seunghan Yu, Jinje Park, Hyunbin Jo, Jongkeun Park, Changkook Ryu and Yeong-gap Jeong
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Jiseok Lee: School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Korea
Seunghan Yu: School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Korea
Jinje Park: School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Korea
Hyunbin Jo: 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
Yeong-gap Jeong: Human Resource T/D Institute, Korea South-East Power Co., Jinju 52852, Korea

Energies, 2020, vol. 13, issue 19, 1-17

Abstract: For renewable electricity production, biomass can fully displace coal in an existing power plant with some equipment modifications. Recently, a 125 MWe power plant burning mainly anthracite in Korea was retrofitted for dedicated wood pellet combustion with a change of boiler configuration from arch firing to wall firing. However, this boiler suffers from operational problems caused by high unburned carbon (UBC) contents in the bottom ash. This study comprises an investigation of some methods to reduce the UBC release while achieving lower NO x emissions. The computational fluid dynamics approach was established and validated for typical operating data. Subsequently, it was applied to elucidate the particle combustion and flow characteristics leading to the high UBC content and to evaluate the operating variables for improving the boiler performance. It was found that the high UBC content in the bottom ash was a combined effect of the poor fuel grindability and low gas velocity in the wide burner zone originating from the arch-firing boiler. This prevented the operation with deeper air staging for lower NO x emissions. Reducing the particle size to <1.5 mm by modifying mills or pretreating the fuel using torrefaction was the only effective way of lowering the UBC and NO x emissions with deeper air staging while increasing the boiler efficiency.

Keywords: wood pellet; combustion; unburned carbon; NO x emission; wall-firing boiler; computational fluid dynamics (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: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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