化工学报 ›› 2022, Vol. 73 ›› Issue (6): 2622-2635.doi: 10.11949/0438-1157.20211427

• 流体力学与传递现象 • 上一篇    下一篇

密相流化床中介尺度流动结构的流体力学特性研究

牛犁1(),刘梦溪2(),王海北1   

  1. 1.矿冶科技集团有限公司，北京 100160
    2.中国石油大学（北京）化学工程与环境学院，北京 102249
  • 收稿日期:2021-10-08 修回日期:2022-01-11 出版日期:2022-06-05 发布日期:2022-06-30
  • 通讯作者: 刘梦溪 E-mail:niuli@bgrimm.com;mengxiliu@sina.com
  • 作者简介:牛犁（1993—），女，博士，工程师，niuli@bgrimm.com
  • 基金资助:
    矿冶科技集团青年科技创新基金项目(04-2115);国家自然科学基金项目(91534111)

Hydrodynamic of mesoscale flow structure in dense phase fluidized bed

Li NIU1(),Mengxi LIU2(),Haibei WANG1   

  1. 1.BGRIMM Technology Group, Beijing 100160, China
    2.College of Chemical Engineering and Environment, China University of Petroleum, Beijing 102249, China
  • Received:2021-10-08 Revised:2022-01-11 Published:2022-06-05 Online:2022-06-30
  • Contact: Mengxi LIU E-mail:niuli@bgrimm.com;mengxiliu@sina.com

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摘要：

在一套流化床冷模实验装置中对黄沙颗粒和黄沙-硅微粉 （20 μm）混合颗粒进行实验。测量固含率时间序列信号并进行统计分析，提出并建立复杂光纤脉动信号的解耦方法，实现稠密气固流中介尺度流动结构的准确识别。基于统计矩一致性原理提出气泡阈值的计算方法，通过遍历法确定气泡阈值。对气泡阈值变化规律进行分析，发现加入细颗粒有助于改善流化质量，随表观气速的增加，气泡阈值减小。对气泡、乳化和聚团三相的相分率进行统计，发现在黄沙颗粒中加入少量（5%，质量分数）细颗粒能够显著改善流化质量，细颗粒添加量过多时（10%），对流化质量的改善将减弱。对气泡的流体力学特性进行分析，发现加入10%硅微粉后，气泡弦长增大，频率降低，速度略有降低。对颗粒聚团流体力学特性进行分析，发现随硅微粉含量增加，表观气速对聚团速度的影响减弱，聚团弦长略有减小。加入5%硅微粉后，颗粒聚团的出现频率较小且径向上分布均一。加入10%硅微粉后，聚团频率有所增大，说明加入过多硅微粉会促进聚团的形成。

关键词: 密相流化床, 介尺度, 气泡, 颗粒聚团, 流体力学特性

Abstract:

Three kinds of particles, including sand, sand and fine silica powder mixed particles, are used in the experiment. Time series signals of solid holdup measured by optical fiber probe are statistically analyzed. A method of decoupling complex optical fiber signals was established. The threshold of bubble phase is determined by traversing method, and its accuracy is verified. Variation of the bubble threshold of different particles in radial direction is analyzed, and it is found that addition of fine particles helps to improve the fluidization quality. The threshold of bubble phase decrease with increasing superficial gas velocity. The criterion of particle agglomerate identification in the dense-phase bed is proposed. The characterization of mesoscale flow structure is realized, and a software for decoupling optical fiber signals is written. Mesoscale flow structures of sand and its mixed particles are analyzed. The fractions of bubble phase, emulsion phase and particle agglomerate are obtained. The result shows that addition of a small amount (5%,mass fraction) of fine particles can reduce the formation of agglomerate and significantly improve the fluidization quality. Addition of 10% fine particles will weaken the improvement of fluidization quality. An analysis of hydrodynamics of bubbles reveals that with addition of 10% fine particles, the chord length of bubbles increases and the frequency and rising velocity of bubbles decreases. An analysis of hydrodynamics of agglomerate reveals that the effect of superficial gas velocity on agglomerate velocity is weaken as the content of fine particles increases. With the increase of fine powder, the chord length of agglomerates decreases slightly. When the content of silica powder is 5%, the frequency of particle agglomeration is small and the radial distribution is uniform. When the content of silica powder is 10%, the frequency of agglomerates increases, indicating that adding too much fine powder will promote the formation of agglomerates.

Key words: dense phase fluidized bed, mesoscale, bubble, agglomerate, hydrodynamics characteristics

中图分类号: 

  • TQ 051

图1

实验装置流程图1—罗茨鼓风机; 2—缓冲罐; 3—气体分配器; 4—转子流量计; 5—气体分布器; 6—流化床; 7,8—旋风分离器; 9—料腿; 10—过滤器"

表1

颗粒物理性质"

颗粒种类平均粒径/μm堆积密度/(kg/m3)颗粒密度/(kg/m3)
黄沙38515872486
硅微粉20—2649

表2

混合颗粒性质"

颗粒种类颗粒粒径dp/μm颗粒密度ρp/(kg/m3)起始流化 固含率
黄沙38524860.67
黄沙+硅微粉 (5%,质量分数)36424950.60
黄沙+硅微粉 (10%,质量分数)34725030.55

图2

实验介质粒径分布"

图3

光纤信号解耦步骤"

图4

不同操作气速下气泡阈值沿径向分布（h=512 nm）"

图5

气泡的识别"

图6

颗粒聚团识别示意图"

图7

颗粒聚团的识别"

图8

光纤探针测量颗粒聚团示意图"

图9

求解聚团弦长概率密度的示意图"

图10

三相体积分数沿径向的变化（h=512 mm）"

图11

气泡速度沿径向的变化（h=512 mm）"

图12

气泡频率沿径向的变化（h=512 mm）"

图13

气泡尺寸沿径向的变化（h=512 mm）"

图14

平均聚团速度随表观气速和径向位置的变化（h=512 mm）"

图15

平均聚团频率随表观气速和径向位置的变化（h=512 mm）"

图16

平均聚团弦长随表观气速和径向位置的变化（h=512 mm）"

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