Effect of operating factors on liquid-liquid mass transfer and dispersion pattern of sedimentary liquid in a mechanically stirred vessel

Liquid-liquid dispersion and mass transfer were investigated in mechanically stirred vessels without baffles by changing operation factors such as an impeller rotation speed, off-bottom clearance, volumetric liquid ratio etc. Dispersion regime was categorized into five groups: the sedimentary liquid was kept at a vessel bottom (I), partially elevated without any collision (II), partially dispersed by colliding with the impeller bottom (III), both liquids were partially dispersed by collisions with impeller blades (III’), and the sedimentary liquid is completely dispersed (IV). The dispersion switched to I→II→III →IV with the increasing rotation speed and decreasing off-bottom clearance. Liquid-liquid mass transfer rate was significantly enhanced with the collision of the sedimentary liquid with the impeller bottom, and subsequently increased with the increasing rotation speed, volumetric liquid ratio, and vessel diameter, and with the decreasing off-bottom clearance. A multiple regression analysis method was applied to determine the mass transfer rates of III and III’.