GB1149169A - Heat utilization in aromatics fractionation - Google Patents

Abstract

1,149,169. Fractionating aromatic hydrocarbon mixtures. UNIVERSAL OIL PRODUCTS CO. 16 Aug., 1966 [26 Aug., 1965], No. 36518/66. Heading C5E. Hydrocarbon mixtures comprising benzene and xylene isomers including ortho-xylene are separated by a distillation process comprising charging the mixture to a benzene distillation column to the bottom of which heat is supplied by indirect heat exchange in a reboiling zone with condensing steam obtained from a steam generation zone as described below, recovering from said benzene column a benzene-rich overhead fraction and a substantially benzenefree bottoms fraction, passing at least part of said bottoms fraction to a xylene distillation column operating under an overhead pressure of 0À68-6À8 atmospheres absolute, passing the overhead vapours from said xylene column through said steam generation zone and therein condensing said vapours by indirect heat exchange with boiling water under regulated pressure and at a temperature higher than that of the benzene column bottoms, recovering said condensed vapours which comprise meta-xylene and/or para-xylene, recovering from said xylene column a bottoms fraction comprising orthoxylene, and withdrawing steam from said steam generation zone and passing at least a portion thereof to the reboiling zone of the benzene column. When the feed mixture also contains toluene, a toluene column is interposed between the benzene and xylene columns, the benzene column bottoms being charged to the toluene column and the toluene column bottoms to the xylene column. Detailed operating conditions for each column are given. The process enables heat economy, since the benzene column may be heated solely by steam obtained within the system.