Parex Unit Feed

A process for separation of hydrocarbon material from at least two separate sources of feed, the process comprising the steps of:

• (a) introducing a first multicomponent feed, comprising at least one desired product, through at least one fluid communication conduit into a simulated moving-bed adsorption apparatus comprising at least one rotary valve and plural sieve chambers;
• (b) flushing the at least one conduit in step (a) with a sufficient quantity of at least one initial flushing medium comprising the at least one desired product in step (a) in an initial concentration, such that feed residue is flushed from the at least one conduit in step (a) into the apparatus by the at least one initial medium;
• (c) flushing the at least one conduit in step (a) with a sufficient quantity of a second and preferably final flushing medium, wherein said second flushing medium is selected from the group consisting of desorbent, such as paradiethylbenzene (PDEB), toluene, or a mixture thereof, and a flushing medium comprising the at least one desired product in step (a) in a final concentration, such that the final concentration is not less than and is optionally greater than the initial concentration and such that initial medium residue from the at least one initial medium is flushed from the conduit in step (a) into the apparatus by the final medium;
• (d) withdrawing the at least one desired product in step (a) from the apparatus;
• (e) introducing a second multicomponent feed comprising at least one desired product, which may be the same or different from the at least one desired product in step (a) and which, if the same, is present in the second multicomponent feed in a concentration different from the concentration of the at least one desired product in said first multicomponent feed, through at least one fluid communication conduit into the apparatus;
• (f) flushing the at least one conduit in step (d) with a sufficient quantity of at least one initial flushing medium (which may be the same or different from the flushing medium in step (b)) comprising the at least one desired product in step (e) in an initial concentration, such that feed residue is flushed from the at least one conduit in step (e) into the apparatus by the at least one initial medium in step (f);
• (g) withdrawing the at least one desired product in step (d) from the apparatus;
• the process further characterized by advancement of the rotary valve to a new valve position by completion of a valve step, defined as a valve cycle, the improvement characterized by replumbing the rotary valve so that the input of the secondary flush is a least one and preferably two valve steps downstream of the original plumbing or wherein it is replumbed so that input of the secondary flush is closer in valve cycle sequent to the input of the primary flush.