(138f) RDC-Design and Operation Efficiency

Although beeing classified as "out of fashion" RDC-extractors still do a great job in liquid-liquid extraction.

Advantageous application is recommended when the feed phases do have problematic properties such as high viscosities or the formation of crud layers in separation zones. Therefore design research for optimization of RDC operation is still on the agenda.

The dimension of compartment geometry and its effect on operation have been object of research for decades with different design recommendations. In the present work a lab size RDC column with two different compartment geometries was investigated. Operation characteristic and mass transfer efficiency were investigated on the basis of RTD- and mass transfer experiments. RDT was carried out with pulse tracer and monitoring of the conductivity along the column height. Mass tranfer was investigated with the test system SST-butanol-water. Although the test system is not in accordance with EFCE recommendation it has several operational and safety related advantages.

From basic investigations a significant effect of compartment geometry on dispersed phase distribution in the single compartment was derived. The outcome of these hydraulic optimizations shows very even holdup along the apparus height with symmetric eddies for large compartment height. Low compartment height induces uneven hold-up distribution of the dispersed phase along the apparatus height with eddies of different direction of rotation, even in neighbouring compartments.

But RTD as well as mass transfer experiments confirm that latter design is advantageous over symmetric compartment hydraulics, worth being considered in practical application.