SCI和EI收录∣中国化工学会会刊

Chinese Journal of Chemical Engineering ›› 2022, Vol. 44 ›› Issue (4): 72-86.DOI: 10.1016/j.cjche.2021.03.034

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Numerical simulation of local and global mixing/segregation characteristics in a gas–solid fluidized bed

Zhen Wan, Youjun Lu   

  1. State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China
  • Received:2020-10-19 Revised:2021-03-17 Online:2022-06-18 Published:2022-04-28
  • Contact: Youjun Lu,E-mail:yjlu@mail.xjtu.edu.cn
  • Supported by:
    This work was supported by the National Key Research and Development Program of China (2020YFA0714400) and the National Nature Science Foundation of China (51925602, 51888103).

Numerical simulation of local and global mixing/segregation characteristics in a gas–solid fluidized bed

Zhen Wan, Youjun Lu   

  1. State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China
  • 通讯作者: Youjun Lu,E-mail:yjlu@mail.xjtu.edu.cn
  • 基金资助:
    This work was supported by the National Key Research and Development Program of China (2020YFA0714400) and the National Nature Science Foundation of China (51925602, 51888103).

Abstract: Researches on solids mixing and segregation are of great significance for the operation and design of fluidized bed reactors. In this paper, the local and global mixing and segregation characteristics of binary mixtures were investigated in a gas–solid fluidized bed by computational fluid dynamics-discrete element method (CFD-DEM) coupled approach. A methodology based on solids mixing entropy was developed to quantitatively calculate the mixing degree and time of the bed. The mixing curves of global mixing entropy were acquired, and the distribution maps of local mixing entropy and mixing time were also obtained. By comparing different operating conditions, the effects of superficial gas velocity, particle density ratio and size ratio on mixing/segregation behavior were discussed. Results showed that for the partial mixing state, the fluidized bed can be divided into three parts along the bed height: complete segregation area, transition area and stable mixing area. These areas showed different mixing/segregation processes. Increasing gas velocity promoted the local and global mixing of binary mixtures. The increase in particle density ratio and size ratio enlarged the complete segregation area, reduced the mixing degree and increased the mixing time in the stable mixing area.

Key words: Discrete element method, Solids mixing, Binary mixtures, Fluidized bed

摘要: Researches on solids mixing and segregation are of great significance for the operation and design of fluidized bed reactors. In this paper, the local and global mixing and segregation characteristics of binary mixtures were investigated in a gas–solid fluidized bed by computational fluid dynamics-discrete element method (CFD-DEM) coupled approach. A methodology based on solids mixing entropy was developed to quantitatively calculate the mixing degree and time of the bed. The mixing curves of global mixing entropy were acquired, and the distribution maps of local mixing entropy and mixing time were also obtained. By comparing different operating conditions, the effects of superficial gas velocity, particle density ratio and size ratio on mixing/segregation behavior were discussed. Results showed that for the partial mixing state, the fluidized bed can be divided into three parts along the bed height: complete segregation area, transition area and stable mixing area. These areas showed different mixing/segregation processes. Increasing gas velocity promoted the local and global mixing of binary mixtures. The increase in particle density ratio and size ratio enlarged the complete segregation area, reduced the mixing degree and increased the mixing time in the stable mixing area.

关键词: Discrete element method, Solids mixing, Binary mixtures, Fluidized bed