Abstract: A chromatographic simulated moving bed separation process is most generally characterized by a recycling pump which successively adopts the flow rate characteristics of 4 or 5 zones of the process. The invention describes the method by which a conventional simulated moving bed separator process can be adapted to a simulated moving bed process in which the recycling pump is operated at an optimal constant flow rate. In order to achieve this, throughout the cycle all the introduction and extraction circuits are shifted using independent means, such that the eluted volume at the outlet to each zone remains substantially constant, zone by zone, between two successive shifts throughout the cycle.

Abstract: An apparatus and process for fractionation of component mixtures by chromatography or adsorption on a simulated mobile bed comprising three, four or five zones is described. A compressed gas is injected as eluent (IE, IR) using a compressor or pump, the pressure being lower than the critical pressure of the gas. At any point in at least one zone and preferably at any point in at least two zones from the eluent injection point (IR), the gas has a compressibility coefficient substantially different to 1. A supercritical fluid or a subcritical liquid may equally be injected as the eluent. The pressure between each zone may be altered.