Investigation of Ash Deposition Dynamic Process in an Industrial Biomass CFB Boiler Burning High-Alkali and Low-Chlorine Fuel

Hengli Zhang, Chunjiang Yu, Zhongyang Luo and Yu’an Li
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Hengli Zhang: State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China
Chunjiang Yu: State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China
Zhongyang Luo: State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China
Yu’an Li: State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China

Energies, 2020, vol. 13, issue 5, 1-11

Abstract: The circulating fluidized bed (CFB) boiler is a mainstream technology of biomass combustion generation in China. The high flue gas flow rate and relatively low combustion temperature of CFB make the deposition process different from that of a grate furnace. The dynamic deposition process of biomass ash needs further research, especially in industrial CFB boilers. In this study, a temperature-controlled ash deposit probe was used to sample the deposits in a 12 MW CFB boiler. Through the analysis of multiple deposit samples with different deposition times, the changes in micromorphology and chemical composition of the deposits in each deposition stage can be observed more distinctively. The initial deposits mainly consist of particles smaller than 2 μm, caused by thermophoretic deposition. The second stage is the condensation of alkali metal. Different from the condensation of KCl reported by most previous literatures, KOH is found in deposits in place of KCl. Then, it reacts with SO 2 , O 2 and H 2 O to form K 2 SO 4 . In the third stage, the higher outer layer temperature of deposits reduces the condensation rate of KOH significantly. Meanwhile, the rougher surface of deposits allowed more calcium salts in fly ash to deposit through inertial impact. Thus, the elemental composition of deposits surface shows an overall trend of K decreasing and Ca increasing.

Keywords: deposit; biomass industrial boiler; alkali metal; circulating fluidized bed (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 (4)

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