Experimental study on secondary air mixing along the bed height in a circulating fluidized bed with a multitracer-gas method

doi:10.1016/j.cjche.2024.03.003

摘要/Abstract

摘要： A multitracer-gas method was proposed to study the secondary air (SA) mixing along the bed height in a circulating fluidized bed (CFB) using carbon monoxide (CO), oxygen (O₂), and carbon dioxide (CO₂) as tracer gases. Experiments were carried out on a cold CFB test rig with a cross-section of 0.42 m×0.73 m and a height of 5.50 m. The effects of superficial velocity, SA ratio, bed inventory, and particle diameter on the SA mixing were investigated. The results indicate that there are some differences in the measurement results obtained using different tracer gases, wherein the deviation between CO and CO₂ ranges from 42% to 66% and that between O₂ and CO₂ ranges from 45% to 71% in the lower part of the fluidized bed. However, these differences became less pronounced as the bed height increased. Besides, the high solid concentration and fine particle diameter in the CFB may weaken the difference. The measurement results of different tracer gases show the same trends under the variation of operating parameters. Increasing superficial velocity and SA ratio and decreasing particle diameter result in better mixing of the SA. The effect of bed inventory on SA mixing is not monotonic.

关键词: Circulating fluidized bed, Secondary air injection, Gas mixing, Multitracer-gas method

Abstract: A multitracer-gas method was proposed to study the secondary air (SA) mixing along the bed height in a circulating fluidized bed (CFB) using carbon monoxide (CO), oxygen (O₂), and carbon dioxide (CO₂) as tracer gases. Experiments were carried out on a cold CFB test rig with a cross-section of 0.42 m×0.73 m and a height of 5.50 m. The effects of superficial velocity, SA ratio, bed inventory, and particle diameter on the SA mixing were investigated. The results indicate that there are some differences in the measurement results obtained using different tracer gases, wherein the deviation between CO and CO₂ ranges from 42% to 66% and that between O₂ and CO₂ ranges from 45% to 71% in the lower part of the fluidized bed. However, these differences became less pronounced as the bed height increased. Besides, the high solid concentration and fine particle diameter in the CFB may weaken the difference. The measurement results of different tracer gases show the same trends under the variation of operating parameters. Increasing superficial velocity and SA ratio and decreasing particle diameter result in better mixing of the SA. The effect of bed inventory on SA mixing is not monotonic.

Key words: Circulating fluidized bed, Secondary air injection, Gas mixing, Multitracer-gas method

Qingyu Zhang, Leming Cheng, Kun Li, Qixun Kang, Qiang Guo, Chaogang Wu. Experimental study on secondary air mixing along the bed height in a circulating fluidized bed with a multitracer-gas method[J]. 中国化学工程学报, 2024, 70(6): 54-62.

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