Process and device for producing a gas using a cascade of membranes working at different temperatures

摘要

Process for producing a high purity gas from a gaseous mixture using at least two successive membrane separators. The inlet mixture (1) passes into a first membrane separator (2) operating at a first temperature and all or part of the residual mixture (5) from this separator is passed to a second membrane separator (3) operating at a second temperature to obtain high purity gas at the residual outlet of the second operator. The first temperature is at least 20 deg. C higher than the second temperature and preferably 40 deg. C higher. The mixture from the permeate side of the second separator is recycled to the inlet of the first separator. High purity nitrogen production apparatus is also claimed.