多层组合桨搅拌槽内气-液分散特性的研究

Gas- Liquid Dispersion in a Multi-Impeller Stirred Tank

在直径为0.476m的椭圆底搅拌槽中,采用由六叶半椭圆管叶盘式涡轮桨(HEDT)及四叶宽叶翼型桨的上提(WHU)及下压(WHD)操作组合的六种不同的三层桨,研究了气-液两相体系中的通气功率变化及气含率特性,获得不同桨型的通气搅拌功率及气含率的关联式;结果表明,底桨为HEDT的组合桨通气功率下降幅度最小,相同输入功率时气含率最高,其次为WHD,WHU为底桨时气液分散性能最差。因此,适用于气液两相操作的优化组合桨应以HEDT为底桨。此研究结果可为工业用多层组合桨气液搅拌反应器的设计提供参考。

In a triple-impeller stirred tank of 0.476 m in diameter the mixing power demand and gas holdup were measured by using a torque transducer and calibrated radar probe respectively. Six kinds of impeller combinations consisting of three basic impeller types, namely, half elliptical disk turbine (HEDT), four wide-blade hydrofoil upward-pumping (WHU) and downward-pumping (WHD) impellers, were used in the experiments. The gassed mixing power demand and gas holdup correlations for different agitators combination were proposed. The results show that the gas-liquid dispersion is mainly controlled by the bottom impeller in the multi-impeller stirred tanks. Among the six kinds impeller combinations the combinations with HEDT as bottom impeller have the flattest relative power demand (RPD, the power demanded in gas-liquid two phases operation compared to that at the same speed in liquid alone) and the highest gas holdup under the same power input and gas flow rate, and followed by the impeller combinations with WHD as the bottom impeller. The impeller combinations with WHU as bottom impeller have the lowest RPD and gas holdup. The impeller combinations with HEDT as bottom impeller are the optimal combinations for gas-liquid dispersion. The results are helpful for the design of the multi-impeller reactor.