초록 ▼

An object of the present invention is to provide a method for recovering a gas using a semipermeable membrane in an apparatus having a simple structure. The method is capable of maintaining a purity of a product gas at a constant value even if a feed amount of a feed stream is fluctuated. A feed str

An object of the present invention is to provide a method for recovering a gas using a semipermeable membrane in an apparatus having a simple structure. The method is capable of maintaining a purity of a product gas at a constant value even if a feed amount of a feed stream is fluctuated. A feed stream G1 is a gas mixture of a fast gas having a relatively high permeability to a membrane 1 and a slow gas having a relatively low permeability to the membrane 1. The feed stream G1 is pressurized by a compressor 3 and fed to a membrane 1 separation unit 2 having the membrane 1. Part G7 of the permeate stream on the permeate side of the membrane 1 is recirculated to the upstream side of the compressor 3 through the first recirculation line 17 and merged into a stream of the feed stream G1. Simultaneously, another part of the permeate stream G2 on the permeate side of the membrane 1 is recovered through a product gas recovering line 5. In this manner, a product gas G3 having a fast gas increased in concentration is obtained.

대표청구항 ▼

[What is claimed is:] [1.]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 ha

[What is claimed is:] [1.]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.