Influence of particle size on the exit effect of a full-scale rolling circulating fluidized bed
Influence of particle size on the exit effect of a full-scale rolling circulating fluidized bed
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DOI：
10.1080/02726351.2016.1276496
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发表时间：
2018-07
影响因子：
2.5
通讯作者：
Zhilong Wang;T. Zhao;Jiafeng Yao;Kai Liu;M. Takei
中科院分区：
文献类型：
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作者：
Zhilong Wang;T. Zhao;Jiafeng Yao;Kai Liu;M. Takei
摘要采用计算流体力学-离散元方法(CFD-DEM)，研究了颗粒尺寸对全尺寸滚动循环流化床(CFB)出口效应的影响。对全尺寸滚动循环床与简化滚动循环床的气固两相流动进行了比较。从而阐明了全尺寸滚动循环床的出口效应。在空气相，当全尺寸滚动循环床达到最大角位移时，空气轴向速度Vya出现峰值。在全尺寸滚动循环床上，颗粒相在顶部和底部分别存在返混和径向交换现象。然而，这些现象在简化滚动循环床的顶部和底部并不明显。通过分析不同粒径下颗粒所受的作用力，阐明了上述出射效应的机理。最后，颗粒尺寸的增大导致VYA峰的加剧、颗粒返混和径向交换现象。因此，气固两相流的出口效应强度随着颗粒尺寸的增大而增大。结果表明，由于小颗粒的出口效应，小颗粒有可能提高全尺寸滚动循环床的净化效率。
ABSTRACT This paper investigated the influence of particle size on the exit effect of a full-scale rolling circulating fluidized bed (CFB) by using the Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) method. The gas–solid two-phase flow of the full-scale rolling CFB was compared with that of a simplified rolling CFB. Thus, the exit effect of the full-scale rolling CFB was clarified. In the air phase, a peak of air axial velocity vya was observed when the full-scale rolling CFB reached the maximum angular displacement. The particle phase possessed back mixing and radial exchange phenomena at the top and bottom of the full-scale rolling CFB, respectively. However, those phenomena were not obvious at the top and bottom of the simplified rolling CFB. The mechanism of the above-mentioned exit effect was then clarified by analyzing the forces acting on the particles under different particle sizes. Finally, the increases in particle size lead to the intensification of the peak of vya, particle back mixing, and radial exchange phenomena. Therefore, the intensity of the exit effect of the gas–solid two-phase flow increased as the particle size increased. The results suggested that the small particles had the potential to promote the purification rate of the full-scale rolling CFB on account of its small exit effect.