TY - JOUR
T1 - Prediction and minimization of NOx emission in a circulating fluidized bed combustor
T2 - A comprehensive mathematical model for CFB combustion
AU - Ke, Xiwei
AU - Engblom, Markus
AU - Yang, Hairui
AU - Brink, Anders
AU - Lyu, Jun Fu
AU - Zhang, Man
AU - Zhao, Bing
N1 - Funding Information:
This work was supported by the Key Project of the National Thirteen-Five Year Research Program of China (2020YFB0606300, 2019YFE0102100). Mr. Xiwei Ke also acknowledges the Johan Gadolin Process Chemistry Centre (PCC) in Åbo Akademi University for the Johan Gadolin Scholarship (JGS) awarded.
Funding Information:
This work was supported by the Key Project of the National Thirteen-Five Year Research Program of China (2020YFB0606300, 2019YFE0102100). Mr. Xiwei Ke also acknowledges the Johan Gadolin Process Chemistry Centre (PCC) in ?bo Akademi University for the Johan Gadolin Scholarship (JGS) awarded.
Publisher Copyright:
© 2021 Elsevier Ltd
PY - 2022/2/1
Y1 - 2022/2/1
N2 - A comprehensive 1-dimensional/1.5-dimensional hybrid mathematical model is developed for predicting NOx emission of a circulating fluidized bed (CFB) combustor under broader operating parameters. In this model, the local gas–solid fluidization state and gas/heat transfer conditions in different regions of a CFB combustor are specifically considered. Some two- or three-dimensional problems, such as bubble breakage over dense bed surface, secondary air injection, core-annular flow structure, and particle clusters in freeboard, are also taken into account in 1-D/1.5-D modeling. The detailed chemical kinetic mechanism is creatively used to describe the homogeneous reaction system towards CFB combustion simulation. In addition to operating parameters and fuel-specific inputs, no other model parameters can be trimmed from case to case. This integral CFB model is validated against the field test data obtained from three commercial CFB boilers with different capacities, some of which are first disclosed. Favorable comparisons are obtained between the predicted and measured results, involving particle size distributions, temperature and pressure profiles, and NOx/SO2 emissions. The final NO emission, as well as gas profiles, are somewhat different among the cases, which may be attributed to the discrepancy in boiler structure, fuel properties, and operating conditions. Further sensitivity analysis indicates that the proportion of volatile-N in total fuel-N, char combustion reactivity, and char-NO reactivity significantly impact the NOx emission for CFB combustion. Meanwhile, the gas–solid fluidization state also plays an essential role in the NOx emission and the in-furnace combustion efficiency, such as the gas flow distribution between phases, bubble size, secondary air penetration depth, etc. However, the NOx emission seems insensitive to the particle external gas mass transfer coefficients.
AB - A comprehensive 1-dimensional/1.5-dimensional hybrid mathematical model is developed for predicting NOx emission of a circulating fluidized bed (CFB) combustor under broader operating parameters. In this model, the local gas–solid fluidization state and gas/heat transfer conditions in different regions of a CFB combustor are specifically considered. Some two- or three-dimensional problems, such as bubble breakage over dense bed surface, secondary air injection, core-annular flow structure, and particle clusters in freeboard, are also taken into account in 1-D/1.5-D modeling. The detailed chemical kinetic mechanism is creatively used to describe the homogeneous reaction system towards CFB combustion simulation. In addition to operating parameters and fuel-specific inputs, no other model parameters can be trimmed from case to case. This integral CFB model is validated against the field test data obtained from three commercial CFB boilers with different capacities, some of which are first disclosed. Favorable comparisons are obtained between the predicted and measured results, involving particle size distributions, temperature and pressure profiles, and NOx/SO2 emissions. The final NO emission, as well as gas profiles, are somewhat different among the cases, which may be attributed to the discrepancy in boiler structure, fuel properties, and operating conditions. Further sensitivity analysis indicates that the proportion of volatile-N in total fuel-N, char combustion reactivity, and char-NO reactivity significantly impact the NOx emission for CFB combustion. Meanwhile, the gas–solid fluidization state also plays an essential role in the NOx emission and the in-furnace combustion efficiency, such as the gas flow distribution between phases, bubble size, secondary air penetration depth, etc. However, the NOx emission seems insensitive to the particle external gas mass transfer coefficients.
KW - Circulating fluidized bed
KW - Combustion
KW - Mathematical model
KW - NO emission
KW - Validation
UR - http://www.scopus.com/inward/record.url?scp=85116865456&partnerID=8YFLogxK
U2 - 10.1016/j.fuel.2021.122133
DO - 10.1016/j.fuel.2021.122133
M3 - Article
AN - SCOPUS:85116865456
SN - 0016-2361
VL - 309
JO - Fuel
JF - Fuel
M1 - 122133
ER -