Patent ID: 8123950

Claim:
A process for simulated moving bed (SMB) separation of a feed F in a SMB device having at least one column, said column being composed of a plurality of beds of adsorbants separated by plates P i each comprising at least one distribution/extraction system, in which process the feed F and a desorbent D are supplied, and at least one extract E and at least one raffinate R are withdrawn, the supply and withdrawal points being shifted over time by a value corresponding to one bed of adsorbant with a switch time ST, and determining a plurality of operational zones of the SMB, and in particular the following 4 principal zones: a zone 1 for desorption of the compounds produced in the extract, included between the supply of the desorbent D and the withdrawal of the extract E; a zone 2 for desorption of the compounds produced in the raffinate, included between the withdrawal of the extract E and the supply of the feed F; a zone 3 for adsorption of compounds produced in the extract, included between the supply of the feed and the withdrawal of the raffinate R; a zone 4 located between the withdrawal of the raffinate R and the supply of the desorbent D; the device further comprising external bypass lines L i/i+1 directly joining two successive plates P i , P i+1 , the index i being either even throughout the column or, in a manner which is exclusive from the foregoing, odd throughout the column, and allowing said plates to be flushed, in which device each of the bypass lines L i/i+1 includes automated means for regulating the flow rate in the bypass line, the degree of opening of said regulating means being defined by the following three rules: a) establishing a flow rate corresponding to an oversynchronicity in the range 15% to 30% in all of the open bypass lines of zone 1; b) establishing a flow rate corresponding to the synchronicity within plus or minus 8% in all of the open bypass lines of zones 2 and 3; c) establishing a flow rate corresponding to an oversynchronicity in the range 20% to 40% in all of the open bypass lines of zone 4; the synchronicity flow rate being defined by (V i +V i+1 +VL i,i+1 )/ST, in which expression: V i denotes the volume of the distribution/extraction system of the outflow plate P i ; V i+1 denotes the volume of the distribution/extraction system of the inflow plate P i+1 ; VL i/i+1 denotes the volume of the bypass line between P i and P i+1 ; and ST denotes the switch time; the oversynchronicity being defined by the formula: oversynchronicity=(actual flow rate in bypass line under consideration/synchronicity flow rate)−1.