Effects of internal structure on throughput of mixer-settler extraction column

Maximum throughputs were measured for a mixer-settler extraction column of 100 mm diameter, and the effects of agitation speed and the internal structure on throughput were examined. To elucidate these effects on the throughput, the pressure differences at various points in the column were also measured. The throughput increased linearly with the agitation speed and the value for the 100 mm column was 2.3 times as large as that for the 60 mm column. Large effects of the downspout diameter and the distance between the impeller and the riser on the throughput were observed. It was confirmed that the throughput could be determined from the balance among the pressure drop of fluid flow, the suction pressure induced by the lifter-turbine impeller, and the buoyant force. The pressure drop of fluid flow was given by the sum of the pressure drops through the downspout and across the drop coalescer, and the former was dominant. The suction pressure induced by the impeller was correlated with the tip velocity of the impeller. It was predicted by the calculation method derived here that a large throughput could be realized by use of large downspout pipes, and the throughput increased with the column diameter for the column of similar figures, but the increase was comparatively small for the agitation speed corresponding to a given average drop diameter. The throughput was also expected to increase with the increase in the interfacial tension, while the effect of the density difference between the dispersed and the continuous phases on the throughput might be comparatively small.