Process for separating aggressive gases from gas mixtures

Claim 1

A process for separating an aggressive gas from a mixture of said aggressive gas and at least one other gas, comprising (a) passing the gas mixture through a plurality of treatment zones connected in series, (b) in each zone first compressing the gas mixture, (c) then in each zone bringing the compressed gas mixture into contact with a feed side of a membrane having a critical partial pressure for the aggressive gas and being more permeable to the aggressive gas than said other gas such that the aggressive gas permeates the membrane to the other side thereof to thereby decrease the partial pressure of the aggressive gas on the feed side of the membrane, said gas mixture being compressed at a temperature and to such a pressure prior to contact with the membrane that the partial pressure of the aggressive gas is a least 75 percent of said critical partial pressure and the partial pressure of the aggressive gas is not above the critical partial pressure of the aggressive gas, (d) maintaining the gas mixture in contact with said feed side of said membrane a sufficient time to decrease the partial pressure of the aggressive gas on the feed side of the membrane to less than 40 percent of said critical partial pressure, and (e) passing the gas mixture through a sufficient number of treatment zones that the non-permeated gas mixture leaving the last treatment zone in said series contains less than 20 percent of said aggressive gas.