Simulated moving bed separation method and device with reduced number of beds and bypass fluid flow

A method for the simulated moving bed separation of a feedstock (F) in a simulated moving bed separation device,

• the device comprising:
• at least one column comprising a plurality of beds of adsorbent (Ai) which are separated by plates (Pi) each comprising a distribution/extraction system;
• and
• external bypass lines (Li/i+1) directly joining two successive plates (Pi, Pi+1), each external bypass line comprising fluid (F, D) feed points and effluent (E, R) withdrawal points,
• wherein said method comprises:
• the at least one column is fed with the feedstock (F) and a desorbent (D) and at least one extract (E) and at least one raffinate (R) is withdrawn from the at least one column, the feed and withdrawal points being shifted during the course of time by an amount corresponding to one adsorbent bed with a switchover period (ST) and determining a plurality of operating zones of the device, and notably the following main zones:
• a zone 1 for the desorption of the compounds from the extract, this zone being comprised between the feed for the desorbent (D) and the withdrawal of the extract (E),
• a zone 2 for the desorption of the compounds from the raffinate, this zone being comprised between the withdrawal of the extract (E) and the feed for the feedstock (F),
• a zone 3 for the adsorption of the compounds from the extract, this zone being comprised between the feed for the feedstock (F) and the withdrawal of the raffinate (R), and
• a zone 4 situated between the withdrawal of the raffinate (R) and the feed for the desorbent (D);
• in which method:
• at least one zone contains fewer than three beds,
• if the stream (D, E, F, R) delimiting said zone containing fewer than three beds (1, 2, 3, 4) and situated upstream of said zone (1, 2, 3, 4) is injected or withdrawn at the plate Pi via the bypass line Li/i+1, then the stream (E, F, R, D) delimiting the zone and situated downstream of said zone (1, 2, 3, 4) is injected/withdrawn at the plate Pj via the bypass line Lj/j+1, and
• if the stream (E, F, R, D) delimiting said zone containing fewer than three beds (1, 2, 3, 4) and situated downstream of said zone (1, 2, 3, 4) is injected or withdrawn at the plate Pi via the bypass line Li−1/i, then the stream (D, E, F, R) delimiting the zone (1, 2, 3, 4) and situated upstream of said zone (1, 2, 3, 4) is injected/withdrawn at the plate Pj via the bypass line Lj−1/j,
• the plate Pi corresponding to one plate of the column,
• the plate Pj corresponding to a plate other than Pi,
• the bypass line Ji−1/i being the line joining the two successive plates Pi−1 and Pi,
• the bypass line Li/i+1 being the line joining the two successive plates Pi and Pi+1,
• the bypass line Lj−1/j being the line joining the two successive plates Pj−1 and Pj,
• the bypass line Lj/j+1 being the line joining the two successive plates Pj and Pj+1.