Patent ID: 6197090
Filing Date: 2001-03-06
Classification: B01D,C01B

Abstract:
A method for recovering a gas from a gas mixture, comprising the steps of:pressurizing a feed stream, which is a gas mixture of a fast gas having a relatively high permeability to a membrane and a slow gas having a relatively low permeability to the membrane by a compressor, and feeding the feed stream pressurized to a membrane separation unit having the membrane;recirculating part of a permeate stream on a permeate side of the membrane to an upstream side of the compressor and merging the part into a stream of the feed stream;recovering another part of the permeate stream on the permeate side of the membrane to obtain a product gas containing the fast gas increased in concentration,wherein a concentration of the fast gas present in the permeate stream is measured on the permeate side of the membrane; anda flow rate of the part of the permeate stream to be recirculated to the upstream side of the compressor is controlled on the basis of a measured concentration value of the fast gas, so as to maintain the fast gas concentration in the permeate stream at a constant value.