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Loop seals in circulating fluidized beds – Review and parametric studies using CPFD simulation
Chemical Engineering Science ( IF 4.7 ) Pub Date : 2020-12-01 , DOI: 10.1016/j.ces.2020.115917
Janitha C. Bandara , Chameera Jayarathna , Rajan Thapa , Henrik K. Nielsen , Britt M.E. Moldestad , Marianne S. Eikeland

Abstract Loop seal is a robust particle recycling technique used in circulating fluidized bed (CFB) reactors. The rate and the location of the loop seal aeration exert a significant impact on the rate of particle circulation (GS). The standpipe balances the cumulative pressure drop across the rest of the CFB by adjusting its particle height or gas-particle slip velocity. Higher fraction of the loop seal aeration naturally flows down to riser. Increased pressure drop in the standpipe results in high rate of particle circulation. Computational-particle-fluid-dynamic (CPFD) code is customized for multiphase flow modelling. The inbuilt tool of “BC connectors” was incorporated to downsize a CFB into a loop seal. The simulation results of GS and system pressures for loop seal showed a perfect match with experimentally validated CFB model. A parametric study for the effects of aeration rate, aeration position and length of the horizontal section was performed using the developed CPFD model of the loop seal. GS increased proportionally with the loop seal aeration, reaching an approximate threshold at 0.9 Nm3/h and beyond that GS did not improve significantly. Uniform aeration from the loop seal bottom realized the highest particle circulation with a 71% increment. The length of the horizontal section of the loop seal exhibited an inverse relationship on the particle circulation.

中文翻译:

循环流化床中的回路密封——使用 CPFD 模拟进行审查和参数研究

摘要 回路密封是循环流化床 (CFB) 反应器中使用的一种稳健的颗粒回收技术。环路密封曝气的速率和位置对颗粒循环 (GS) 的速率有显着影响。立管通过调整其颗粒高度或气体-颗粒滑移速度来平衡 CFB 其余部分的累积压降。环密封曝气的较高部分自然流向立管。立管中增加的压降导致粒子循环的高速率。计算粒子流体动力学 (CPFD) 代码是为多相流建模定制的。集成了“BC 连接器”的内置工具,以将 CFB 缩小到环密封中。环密封的 GS 和系统压力的仿真结果显示与实验验证的 CFB 模型完美匹配。使用开发的环密封件 CPFD 模型对曝气速率、曝气位置和水平段长度的影响进行了参数研究。GS 与环密封曝气成比例增加,达到近似阈值 0.9 Nm3/h,超过该阈值 GS 没有显着改善。循环密封底部的均匀曝气实现了最高的颗粒循环,增量为 71%。环封水平段的长度与颗粒循环呈反比关系。循环密封底部的均匀曝气实现了最高的颗粒循环,增量为 71%。环封水平段的长度与颗粒循环呈反比关系。循环密封底部的均匀曝气实现了最高的颗粒循环,增量为 71%。环封水平段的长度与颗粒循环呈反比关系。
更新日期:2020-12-01
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