Patent ID: 8658848
Filing Date: 2014-02-25
Classification: B01D,C07C

Abstract:
1. A process for the separation of xylenes producing an extract and a raffinate from a feed constituted by a mixture of xylenes, and operating in simulated counter-current using a series of two adsorbers denoted a) and b) each comprising 12 beds of solid adsorbent, each adsorber being divided into 4 zones defined as follows: zone 1: para-xylene desorption zone, included between the injection of desorbant D and the removal of extract E; zone 2: desorption zone for isomers of para-xylene, included between the removal of the extract E and the injection of the feed to be fractionated F; zone 3: para-xylene adsorption zone, included between the injection of the feed and the withdrawal of the raffinate R; zone 4: zone located between the withdrawal of the raffinate R and the injection of the desorbant D; and the two adsorbers being able to generate in 3 different modes as a function of the flow rate of the feed to be treated and any maintenance operation on one of the adsorbers: in high productivity mode, from 100% to 150%, the two adsorbers are associated in parallel, where the streams from the bottoms of the two adsorbers are orientated to move towards the head of the adsorber from which they derive, the stream from the bottom of adsorber a) being recycled to the head of said adsorber a) and the stream from the bottom of adsorber b) being recycled to the head of said adsorber b); in intermediate productivity mode, 50% to 100%, the adsorbers are associated in series, where the principal stream moves from the bottom of the first adsorber a) towards the head of the second adsorber b) and from the bottom of the second adsorber b) towards the head of the first adsorber a); in maintenance mode, 50% to 75%, the two adsorbers are decoupled, the process operating with a single adsorber, the stream from the bottom of the adsorber used (a) or b) being orientated to move towards the head of said adsorber; the reference feed flow rate 100% being defined as the maximum feed flow rate that can be treated in the unit in intermediate productivity mode such that the mean linear velocity of the liquid stream within the adsorbers with respect to the empty adsorber is equal to 1.4 cm/s.