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 apparatus comprising plural sieve chambers fluidly connected with plural bedlines A1 through An+j, wherein n>2 and n+j is the total number of bedlines, which in turn are fluidly connected with a matrix of fluid communication conduits to distribute plural input streams, including desorbent, a primary flush input and a secondary flush input, and at least two multicomponent feeds differing in the concentration of paraxylene, to said plural bedlines, and plural output streams, including a primary flush output and a secondary flush output, an extract comprising a paraxylene-enriched product, and raffinate, from said 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 flushing medium, wherein said second flushing medium is selected from the group consisting of desorbent, 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 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 improvement comprising:
• when bedline An contains extract, bedline An+9 contains a first multicomponent feed, bedline An+7 contains a second multicomponent feed, then said secondary flush input is contained in a bedline between bedlines An+2 and bedline An+7.