Serial flow continuous separation process

A process for separating an extract component from a raffinate component contained in a feed mixture comprising the steps of:

• (a) maintaining a unidirectional fluid flow system through a series of separating units in which said components have differential rates of travel due to selective retardation or acceleration of each of said components in each of said units, each of said units having a fluid inlet and a fluid outlet, said separating units being interconnected so as to achieve serial flow through said units in a single closed loop;
• (b) mixing said feed mixture with the fluid emanating from one of said fluid outlets and passing the resultant first mixture into the next inlet downstream of said outlet in said series and mixing said displacement fluid with the fluid emanating from another of said fluid outlets and passing the resultant second mixture into the next inlet downstream of said other outlet in said series;
• (c) establishing within said separating units a component concentration distribution, zones of which comprise, sequentially, progressing in the direction of fluid flow, extract and raffinate component mixture with the proportion of the raffinate component to extract component being greater than in the feed mixture, extract and raffinate component mixture with the proportion of extract component to raffinate component being greater than in the feed mixture, concentrated extract component, extract component diluted with displacement fluid, raffinate component diluted with displacement fluid, and concentrated raffinate component;
• (d) withdrawing as an extract product stream a portion of at least one of the streams between an adjacent pair of separating units, and withdrawing as a raffinate product stream a portion of at least one other of the streams between a different adjacent pair of separating units, the selection of the streams from which said product streams are withdrawn being consistent with the desired composition of each of said product streams;
• (e) periodically simultaneously advancing in an upstream direction with respect to fluid flow in said separating units, all of said inlets and outlets to effect the shifting of zones in a downstream direction with respect to said fluid flow, said shifting being effected prior to the progression through said units of said component concentration distribution to the extent that the composition of the inlet or outlet streams to or from any zone becomes inconsistent with the desired composition of that zone.