Inter-column heat integration for multi-column distillation system.

摘要

A multi-component feed (10) comprising component A, B and C with A being the most volatile and C the least volatile is introduced to a multicolumn distillation system comprising a main distillation column (12) and a side column (22). The component A is separated from component C in the main distillation column (12), component A being removed as an overhead fraction (18) and component C being removed as a bottoms fraction (19). Recovery of component B from the side column (22) is enhanced by withdrawing a liquid fraction (24) from the main distillation column (12) at a point intermediate the overhead and feed and introducing that liquid fraction to an upper portion of the side column (12). Lighter components are withdrawn as an overhead (26) from the side column (22) and returned to an optimal location in the distillation system, typically the main distillation column (12). A vapor fraction (25) is also withdrawn from the main distillation column (22) at a point intermediate the bottoms and feed and is introduced to a lower portion of the side column (22). A liquid fraction (27) is withdrawn as bottoms from the side column (22) and returned to the main distillation column (12). Thermal integration in the side column (22) is effected by removing the liquid (28) from the side column (22) and vaporizing (32) this fraction (28) against a vapor fraction (34) from the main distillation column (12). Additionally or alternatively, thermal integration may be achieved by withdrawing a vapor fraction (40) from the side column and heat exchanging with a liquid fraction (36) from the main distillation column. At least a portion of the vaporized liquid (31,37) is returned to the multi-column distillation system and at least a portion of the condensed vapor fraction (35,41) also is returned to the multi-column distillation system.