method for isoalkan / n alkan - separation by adsorption in the gaseous phase in the druckmodulierung and four adsorber used

摘要

A separation process by gaseous phase adsorption of n-paraffins and iso-paraffins from a hydrocarbon charge as effluent from an isomerisation stage.Four adsorbers (1 - 4) are used, of substantially the same size each functioning according to a cycle of stages described as follows (with reference to adsorber 2) and figures 1 - 12 :-a) A sequence 1 in which an adsorption stage (F) is effected by circulating in ascending mode the effluent from the preceding adsorber 1, connecting the outlet from 1(in adsorption phase)to the base of 2 ; b) A sequence 2 which effects an adsorption stage (ADS), by directly injecting an ascending charge to the base of 2 and recovering an iso-paraffin-rich from the upper part of 2 ; c) A sequence 3 following the adsorption operation (ADS) and sampling part of the effluent fluid rich in iso-paraffins to effect the second pressurisation stage RP2 of the following adsorber 3 in ascending current ; d) A sequence 4 in which the adsorption stage (A/F) is conti nued connecting the top of adsorber 2 to the base of adsorber 3, preceeding a second pressurisation stage, the adsorber 2 receiving the charge then being saturated in n-paraffins and the material transfer zone displacing towards adsorber 3 ; e) A sequence 5 in which a first de-pressurisation (DP1) is effected by connecting the base of 2, functioning at high pressure, with the adsorber 4 (having terminated its stripping stage at a lower pressure) thus obtaining an equilibration of pressure in 2 and 4 ; f) A sequence 6 in which a second de-pressurisation (DP2) is effected, the upper extremity of 2 being closed ; g) A sequence 7 in which a primary stripping phase (S1) is effected by connecting the base of the preceeding adsorber 1 to the top of 2, injecting the desorbent in the head of 1 at the end of the stripping phase (S2), the effluent leaving it being relatively poor in adsorbable fraction, the product leaving 2 consisting mainly of a n-paraffin rich fraction ; h) Two sequences, 8 and 9 in which the main stripping stage (STR) is effected by supplying adsorber 2 with desorbent in descending flow ; i) A sequence 10 in which a finishing stage of stripping (S2) is effected by continuation of the desorbent supply to 2 and connecting the outlet of 2 to the adsorber 3 which is starting the desorption phase (S1) ; j) A sequence 11 in which a pressurisation stage (RP1) is effected from a low pressure to an intermediate pressure, by connecting the outlets of 2 and 4 ; and -k) A sequence 12 which effects a second pressurisation (RP2) up to the adsorption pressure by means of a flow from part of the effluent from the preceeding adsorber 1 functioning in adsorption mode (ADS), the fluid being introduced at the base of 2.