上浮颗粒特性对三相搅拌槽内固-液悬浮及气-液分散的影响  

Effects of Buoyant Particle Characteristics on Solid-Liquid Suspension and Gas-Liquid Dispersion in a Three Phase Stirred Tank

作　　者：包雨云[1] 龙建刚[1] 高正明[1] 施力田[1] 

机构地区：[1]北京化工大学化学工程学院,北京100029

出　　处：《高校化学工程学报》2006年第1期25-30,共6页Journal of Chemical Engineering of Chinese Universities

基　　金：教育部优秀青年教师资助计划项目(2002;350)。

摘　　要：在直径为0．476m（T）的椭圆底有机玻璃搅拌槽中，采用作者此前研究优选的多层组合桨（HEDT＋WHD＋WHU），分别选用粒径在0.5至4mm、密度范围在900至955kg·m^-3的聚丙烯（PP）颗粒及粉料、低密度聚乙烯（LDPE）颗粒、高密度聚乙烯（HDPE）颗粒作为上浮固体，操作液位为0.5～1．8T，研究了颗粒特性及操作液位对空气-水-上浮固体三相体系的固-液悬浮及气-液分散性能的影响。结果表明：对于同种颗粒，其表面状态对悬浮特性有较大的影响，颗粒表面因含有少量残余溶剂而呈现部分憎水特性时，达到液面处颗粒停留时间不大于1～2秒的临界悬浮状态所需搅拌转速及输入功率显著增加；此时减少上层桨与液面的距离对降低临界悬浮转速及功率有较大贡献。当颗粒种类不同，表面状态及粒径相近时，液固密度差越大，所需悬浮转速越高；但相同输入功率及表观气速时的气含率相差不大。液固密度差相近时，颗粒越小越易被悬浮，但颗粒越小浓度增加使三相体系的气含率降低的幅度越大。对于不同颗粒所得气含率关联式及悬浮特性研究结果可为工业气液固搅拌槽／反应器的优化设计提供参考。Gas-liquid-buoyant particle three phase stirred tank/reactors are widely used in many industries and very few studies involve in the effect of buoyant particle characteristics on the solid-liquid suspension and gas-liquid dispersion. The just drawdown agitation speed and its corresponding power consumption and gas hold-up were measured by using a torque transducer and calibrated radar probe respectively in a dished base tank of diameter 0.476m agitated by a multi-impeller agitator （a hollow blade dispersing turbine mounted at the lowest position and two wide blade hydrofoils pumping downwards and upwards mounted at the middle and uppest position respectively, HEDT＋WHD＋WHu）. The polypropylene （PP） particles and powders, low and high density polyethylene particles （LDPE and HDPE） with sizes ranging from 0.5 to 4 mm and densities from 900 to 955 kg·m^3 were used in this work. The results show that the hydrophilicity of particles has a strong effect on the solid-liquid suspension. Partly hydrophilic particles caused by the remaining organic solvent on the surface need much higher agitation speed and power consumption to reach the just drawdown of particles. With the decreasing of the level height, the above agitation speed and power consumption decrease significantly especially for aerated systems. When the density difference between the solid and liquid increases, the drawdown of particles can only be achieved with higher agitation speed and power consumption. As in the case of suspended settling particles, smaller particles are easier to bring into suspension. There is little difference in the gas retention behavior for the presence of different particles with similar size. Gas hold-up is almost unaffected by particle size though those less than 1 mm do reduce gas retention. The correlating equations for calculating the just drawdown agitation speed and corresponding power consumption and gas hold-up were proposed, and those equations are of importance to the design of the gas-liquid-solid multi-im

关 键 词：上浮颗粒 颗粒特性 固-液悬浮 气-液分散 气含率 多层桨 气-液-固搅拌槽 

分 类 号：TQ027.39[化学工程]