Cluster characteristics in gas-solids circulating fluidized bed based on k-means algorithm-assisted imaging method

doi:10.16085/j.issn.1000-6613.2024-0132

Abstract

Abstract:

Circulating fluidized bed is widely used in industrial production due to its good gas-solids mixing. Clustering characteristics affect the gas-solids contacting and therefore the heat/mass transfer and the yield of the products as well as the selectivity. To get more detailed information effectively, a high-speed camera was used to visualize the flow field in a two-dimensional circulating fluidized bed at the superficial gas velocity, U_g, equal to 5—9m/s, and the solids circulating rate, G_s, of 50—300kg/(m²·s). The k-means machine learning algorithm was then utilized to assist the image processing to identify the cluster effectively and quantificationally. Results showed that as G_s increased from 50kg/(m²·s) to 300kg/(m²·s) at U_g=9m/s, the cluster frequency almost doubled from 116Hz to 327Hz. The average cluster concentration was correlated with the local lateral position. The average cluster concentration was more uniformly distributed in the central region (y/Y from 0 to 0.7). Toward the near wall region (y/Y from 0.7 to 0.9) it increases rapidly. The change of the average cluster concentration near the wall was nearly three times higher than in the central region. Both the average cluster velocity and the average cluster equivalent diameter displayed a similar trend, decreasing from the center toward the wall in the lateral direction. Quantitative prediction equations for cluster parameters were obtained based on the experimental data. The relative errors were all within 30%. Cluster characteristics were studied quantitatively and systematically in this study. These results can support the development of a gas-solids flow model and process intensification for circulating fluidized beds.

Key words: fluidization, circulating fluidized bed, k-means machine learning, cluster, prediction

摘要：

循环流化床因其优良的气固接触特性在工业生产中的应用十分广泛。颗粒聚团的存在影响着气固相互作用和传热传质，进而影响产品收率和选择性。为了更高效和深入地研究循环流化床内的颗粒聚团现象，本研究利用高速摄像系统对U_g=5~9m/s、G_s=50~300kg/(m²·s)的二维循环流化床内的流场结构进行了可视化采样。采用k-means机器学习算法辅助图像处理，实现复杂流场中颗粒聚团的识别以及定量表征。结果表明，当U_g=9m/s时，随着G_s由50kg/(m²·s)增大至300kg/(m²·s)，颗粒聚团频率由116Hz增加到327Hz，增长了近2倍。平均颗粒聚团浓度在横向截面中心区域y/Y=0~0.7处分布较为均匀，在y/Y=0.7~0.9的边壁处迅速增大。边壁处平均颗粒聚团浓度的变化幅度约为中心区域的3倍。平均颗粒聚团速度以及平均颗粒等效直径在横向上均表现出相同的变化趋势，均由中心向边壁递减。结合实验数据，对不同聚团参数进行拟合，获得了定量预测各个参数的关联式。对比实验数据与预测数据发现，本实验建立的定量关联式获得的预测结果相对误差均在30%以下。本研究结果定量地揭示了循环流化床内各颗粒聚团特性的分布规律，可以为循环流化床气固流动模型开发和过程强化提供数据参考。

关键词: 流态化, 循环流化床, k-means机器学习, 颗粒聚团, 预测

CLC Number:

TQ021.1

SUN Jian, ZHANG Haiyong, WANG Chengxiu, SUN Zeneng, LAN Xingying, GAO Jinsen, ZHU Jingxu. Cluster characteristics in gas-solids circulating fluidized bed based on k-means algorithm-assisted imaging method[J]. Chemical Industry and Engineering Progress, 2025, 44(2): 625-634.

孙俭, 张海勇, 王成秀, 孙泽能, 蓝兴英, 高金森, 祝京旭. 基于k-means机器学习方法的气固循环流化床颗粒聚团特性[J]. 化工进展, 2025, 44(2): 625-634.

Figures/Tables 10

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