同心双轴搅拌器气液分散性能的实验研究

Experimental investigation on gas-liquid dispersion performance in coaxial mixer

针对气液搅拌操作形式单一的现状,将框式桨和Rushton桨组成的同心双轴搅拌器与黏稠体系中的气液分散操作相结合,实验考察了转动模式、内桨转速、通气量和体系黏度等因素对其气液分散性能的影响。结果表明,与单相黏稠体系中同向旋转模式下的功率与混合性能均占优不同,同心双轴搅拌器在反向旋转模式下的气液分散性能相对更好;外桨转速不变时,内桨转速从100增加到300 r·min^-1,整体气含率提高94.3%,局部气含率也均有增大;通气量从0.4提高到1.2 m^3·h^-1,整体气含率提高了72.5%,但局部气含率和气泡尺寸的增大不显著;体系黏度增加,气泡在釜内的停留时间加长,整体气含率单调增加。作为影响搅拌釜气液分散性能的重要参数,转动模式、内桨转速和通气量的确定还必须兼顾系统的功耗与混合效率,并避免发生气泛。

A coaxial mixer consisting of an anchor(outer impeller) and a Rushton turbine(inner impeller) was proposed to improve the gas dispersion in viscous system.The effects of rotation mode,inner impeller speed,gas flux and liquid viscosity on gas dispersion performance were investigated experimentally.Results show that the coaxial mixer operating in counter-rotation mode has better gas dispersion performance,but that coaxial mixer operating in co-rotation mode has better performance of power and mixing.The overall gas holdup is increased by 94.3% and the local gas holdup is also increased correspondingly when the inner impeller speeds up from 100 to 300 r·min^-1 under constant outer impeller speed.Additionally,the overall gas holdup is increased by 72.5% with the rising of gas flux from 0.4 to 1.2 m^3·h^-1,but there are no significant increases in local gas holdup and bubble size.It is also found that the higher viscosity results in the longer residence time of bubbles in liquid and the larger overall gas holdup.The rotation mode,inner impeller speed and gas flux are the important parameters affecting the gas-liquid dispersion performance in coaxial mixer,and also determine the power consumption,mixing efficiency and the occurrence of gas flooding.