Patent ID: 6315818
Filing Date: 2001-11-13
Classification: B01D,C01B

Abstract:
Process for the purification of a gas containing preferentially adsorbable impurities by pressure swing adsorption (PSA) using several adsorbers with, for each adsorber, a cycle comprising the following operative phases, which are offset from one adsorber to another by one nth of the duration (T) of the cycle, in which n designates the number of adsorbers:substantially isobaric adsorption at a high pressure of the cycle, this adsorption phase comprising the admission of impure gas to be treated into the adsorber through a first end of the adsorber, with circulation of said impure gas in the adsorber and simultaneous withdrawal through the other end of the adsorber of purified gas of which at least a portion constitutes the gaseous product, the direction of circulation in the adsorber in the course of this production phase being called co-current and the reverse direction of circulation being called counter-current; regeneration of the adsorber ending with at least one final step in which a residual gas is withdrawn counter-current from the adsorber; and the pressure increased to a high pressure (PH) of the cycle, whereinduring a recycling step a variable portion of said residual gas is recycled, not exceeding 30% of the flow rate of the purified gaseous product, into the impure gas to be treated, the rest of this residual gas constituting a purge; andthe duration (T) of the cycle is shortened when said recycling is carried out, the more as the recycled flow rate is greater.