SCI和EI收录∣中国化工学会会刊

Chinese Journal of Chemical Engineering ›› 2015, Vol. 23 ›› Issue (7): 1077-1084.DOI: 10.1016/j.cjche.2015.03.004

• 流体力学与传递现象 • 上一篇    下一篇

Solid concentration and velocity distributions in an annulus turbulent fluidized bed

Cheng Wu, Yongxiang Gao, Youwei Cheng, Lijun Wang, Xi Li   

  1. Department of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China
  • 收稿日期:2014-08-30 修回日期:2015-01-21 出版日期:2015-07-28 发布日期:2015-08-21
  • 通讯作者: Xi Li
  • 基金资助:

    Supported by the National Natural Science Foundation of China (U1361112, U1162125).

Solid concentration and velocity distributions in an annulus turbulent fluidized bed

Cheng Wu, Yongxiang Gao, Youwei Cheng, Lijun Wang, Xi Li   

  1. Department of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China
  • Received:2014-08-30 Revised:2015-01-21 Online:2015-07-28 Published:2015-08-21
  • Contact: Xi Li
  • Supported by:

    Supported by the National Natural Science Foundation of China (U1361112, U1162125).

摘要: Solid concentration and particle velocity distributions in the transition section of a ? 200mm turbulent fluidized bed (TFB) and a ? 200mm annulus turbulent fluidized bed (A-TFB)with a ? 50mm central standpipewere measured using a PV6D optical probe. It is concluded that in turbulent regime, the axial distribution of solid concentration in A-TFB was similar to that in TFB, but the former had a shorter transition section. The axial solid concentration distribution, probability density, and power spectral distributions revealed that the standpipe hindered the turbulence of gas-solid two-phase flowat a lowsuperficial gas velocity. Consequently, the bottomflow of A-TFB approached the bubbling fluidization pattern. By contrast, the standpipe facilitated the turbulence at a high superficial gas velocity, thus making the bottom flow of A-TFB approach the fast fluidization pattern. Both the particle velocity and solid concentration distribution presented a unimodal distribution in A-TFB and TFB. However, the standpipe at a high gas velocity and in the transition or dilute phase section significantly affected the radial distribution of flow parameters, presenting a bimodal distribution with particle concentration higher near the internal and external walls and in downward flow. Conversely, particle concentration in the middle annulus area was lower, and particles flowed upward. This result indicated that the standpipe destroyed the coreannular structure of TFB in the transition and dilute phase sections at a high gas velocity and also improved the particle distribution of TFB. In conclusion, the standpipe improved the fluidization quality and flow homogeneity at high gas velocity and in the transition or dilute phase section, but caused opposite phenomena at low gas velocity and in the dense-phase section.

关键词: Fluidization, Annulus bed, Transition section, Hydrodynamics, Turbulence

Abstract: Solid concentration and particle velocity distributions in the transition section of a ? 200mm turbulent fluidized bed (TFB) and a ? 200mm annulus turbulent fluidized bed (A-TFB)with a ? 50mm central standpipewere measured using a PV6D optical probe. It is concluded that in turbulent regime, the axial distribution of solid concentration in A-TFB was similar to that in TFB, but the former had a shorter transition section. The axial solid concentration distribution, probability density, and power spectral distributions revealed that the standpipe hindered the turbulence of gas-solid two-phase flowat a lowsuperficial gas velocity. Consequently, the bottomflow of A-TFB approached the bubbling fluidization pattern. By contrast, the standpipe facilitated the turbulence at a high superficial gas velocity, thus making the bottom flow of A-TFB approach the fast fluidization pattern. Both the particle velocity and solid concentration distribution presented a unimodal distribution in A-TFB and TFB. However, the standpipe at a high gas velocity and in the transition or dilute phase section significantly affected the radial distribution of flow parameters, presenting a bimodal distribution with particle concentration higher near the internal and external walls and in downward flow. Conversely, particle concentration in the middle annulus area was lower, and particles flowed upward. This result indicated that the standpipe destroyed the coreannular structure of TFB in the transition and dilute phase sections at a high gas velocity and also improved the particle distribution of TFB. In conclusion, the standpipe improved the fluidization quality and flow homogeneity at high gas velocity and in the transition or dilute phase section, but caused opposite phenomena at low gas velocity and in the dense-phase section.

Key words: Fluidization, Annulus bed, Transition section, Hydrodynamics, Turbulence