Contactor-separator units

#The present invention relates to subassemblies of contactor-separator units suitable for use in liquid-liquid or gas-liquid exchange or extraction apparatus.

#There exist numerous extraction or exchange processes which require a number of successive operations each successively involving intimate contact between two immiscible fluids and separation between the fluids. Examples of such processes are isotopic enrichment by exchange between two liquid phases containing uranium in different valence states, for instance VI and IV. Another example is separation of rare earths, which may require several hundred of mixing-settling operations for achieving the required purity.

#Referring to isotopic enrichment as an example, each elementary contact-separation sequence provides an enrichment, however, with a low partition coefficient, whereby a large number of operations is necessary for achieving the desired enrichment. A large number of contactor-separator units is consequently necessary, in which counter-current flows of two phases occur. In the conventional cascades, one pump for each stage or unit is provided, resulting in high investment and maintainance costs as well as difficult monitoring and control.

#Several embodiments of the invention will now be described with reference to the accompanying drawings in which only those elements necessary for an understanding of the invention have been shown.

#FIGS. 1 and 2 are most simplified block diagrams of a sub-assembly of contactor-separator units for an isotopic enrichment installation, FIGS. 1 and 2 respectively providing indications on the pressures and enrichments;

#FIGS. 3, 4 and 5 are simplified block diagrams of an installation having two sub-assemblies of the general type shown in FIGS. 1 and 2, a head end sub-assembly and a tail end sub-assembly, FIGS. 3, 4 and 5 respectively providing indications on the organic phase enrichment, aqueous phase depletion and distribution of pressures;

#Referring to the drawings, it will be assumed that the installation is for isotopic exchange between an organic phase which becomes enriched in a particular isotope and an aqueous phase immiscible with the organic phase and which becomes progressively depleted in that isotope. The flows of organic and aqueous phases are shown in full line and dash-dot lines, respectively.

#Referring to FIG. 1, there is shown a sub-assembly 1 comprising twelve contactor-separator units numbered from 3a to 3l. In each contactor-separator unit, there takes place an elementary operation, namely successive mixing and separation of the two phases. The contactor-separator units may be of any conventional type, for instance mixer-settlers.

#The sub-assembly of FIG. 1 is connected with other sub-assemblies located upstream and/or downstream in the direction of flow of the organic phase, for constituting an enrichment installation, by pipe means which will be referred to later.