固-液导流筒搅拌槽内流体流动和颗粒悬浮特性

在直径0.8 m的导流筒搅拌槽内，对单相液体的三维速度分布、固-液两相的固体颗粒浓度分布和离底悬浮特性进行了系统的实验研究. 结果表明，导流筒内外的轴向液相速度远大于径向和切向速度，导流筒外壁附近存在一个与主体轴向流动方向相反的二次流区域；搅拌槽底部结构对固体颗粒的临界离底悬浮转速(NJS)有显著的影响，浅锥底的NJS比平底的低14%以上；NJS随固相浓度的增加而增加，但当浓度超过50%时，NJS略有降低；槽内固相浓度分布的均匀性随固相浓度的增加而得到改善. 本研究结果对导流筒搅拌槽的优化设计具有一定的指导意义.

Characteristics of Fluid Flow and Particle Suspension in a Solid-Liquid Draft-tube Stirred Tank

The three-dimension velocity distribution of single liquid phase, solid concentration distribution and particle off-bottom suspension characteristics in the liquidsolid phases were systemically investigated in a draft-tube stirred tank of 0.8 m diameter. The results showed that the axial velocity of liquid phase was far larger than radial and tangential velocities inside and outside the draft tube. And there was a second circulation zone close to the outside wall of the draft tube. The shallow conical bottom leads to a critical just off-bottom suspension impeller speed (NJS) at least 14% lower than that in the flat bottom. As expected, NJS increased as the solid concentration increased. NJS decreased slightly as the solid concentration exceeded 50%. The homogeneity of vertical solid concentration distribution was enhanced with the increase of solid concentration. The results are of importance to the optimization of industrial draft-tube stirred reactors.