Patent ID: 11938442
Assignee: UBE CORPORATION
Field: Chemical engineering (Chemistry)
Classification: CPC B  C | IPC B  C

Claim 0:
1. A gas separation system for producing a CH4 enriched gas from a material gas containing CO2 and CH4, the gas separation system comprising:
a first gas separation membrane unit; and
a second gas separation membrane unit, wherein:
each gas separation membrane unit includes at least a gas inlet port, a permeated gas discharge port, and a non-permeated gas discharge port;
the gas separation system comprises
a material gas feed line connected to the gas inlet port of the first gas separation membrane unit,
a compression means interposed to the material gas feed line,
a first connection line connecting the permeated gas discharge port of the first gas separation membrane unit and the gas inlet port of the second gas separation membrane unit,
a second compression means interposed in midstream of the first connection line, and
a second connection line connecting the non-permeated gas discharge port of the second gas separation membrane unit and the material gas feed line;

the first gas separation membrane unit and the second gas separation membrane unit each have a gas separation selectivity P′CO2/P′CH4 of 30 or greater;
a ratio S1/S2 of membrane area S1 of the first gas separation membrane unit to membrane area S2 of the second gas separation membrane unit is from 4.6 to 12; and
a recovery rate of CH4 is 98% or higher; CO2 content in non-permeated gas discharged from the non-permeated gas discharge port of the first gas separation membrane unit is 5 mol % or less; the pressure of gas to be fed to the second gas separation membrane unit is higher than the pressure of gas to be fed to the first gas separation membrane unit; and an amount of gas fed to the second gas separation membrane unit per unit time is 60% or less of an amount of the material gas fed to the first gas separation membrane unit per unit time.