多层组合桨搅拌槽内通气功率和传质性能研究

在内径为300 mm的搅拌槽内,用六叶半椭圆管叶盘式涡轮桨(HEDT)、抛物线管叶盘式涡轮桨(PDT)和轴流式四叶宽叶翼型桨(WH)上提操作方式(U)和下压操作方式(D)组成的3种组合桨HEDT+2WHU,HEDT+2WHD和PDT+2WHD研究了不同操作条件下各组合桨的通气功率和传质性能。结果表明,各组合桨的相对功率需求(RPD)都随着转速和通气准数的增大而减小,HEDT+2WHU桨的RPD在实验操作条件下一直维持在0.75以上,大于另外两种组合桨;3种组合桨的容积传质系数kLa都随着功耗和表观气速uG的增大而增大,并且当气速较小时,增大气速可以大幅度增大kLa,但随着气量的增加,kLa的增大幅度有所减小;小气量下3种组合桨的kLa差别不大,但大气量下差别明显;PDT+2WHD在气速uG=0.0078~0.039 m/s时表现出最好的传质性能,PDT+2WHD、HEDT+2WHD在uG=0.039 m/s时的传质性能明显优于HEDT+2WHU。基于实验数据,回归得3种组合桨的功率准数和传质系数的关联式,可用于工业设计及应用。

Power consumption and mass transfer for various impeller combinations in a stirred tank

Six-half-elliptical-blade disk turbine (HEDT), parabolic-blade disk turbine (PDT), and four-wide blade hydrofoil impeller (WH) pumping down (D) and pumping up (U) have been employed in three combinations (PDT+2WHD, HEDT+2WHD and HEDT+2WHU) in order to investigate the gassed power demand and volumetric mass transfer coefficient (kLa) in a stirred tank with a diameter of 300mm. The results show that the relative power demand (RPD) decreases with the increasing agitation speed and gas flow number. The RPD of HEDT+2WHUis above 0.75 under all operating conditions, higher than that of other two impeller combinations. kLa of all the three impeller combinations increases with increasing power input and superficial gas velocity (uG). An increase in uG can increase kLa to a great extent at low uG, but the positive effect of uG on kLa decreases when the gas flow rate is relatively high. There are no obvious differences in kLa for different impeller combinations at low uG. PDT+2WHD shows the best mass transfer performance when uG=0.0078-0.039m/s and HEDT+2WHU shows the worst mass transfer performance when uG=0.039m/s. Finally, the regressed correlations for gassed power number and kLa were obtained for actual industrial designs and applications. 