Patent ID: 6921428

Claim:
A method of separating and recovering a halide gas from a mixed gas containing the halide gas through multiple stages using at least two separation membrane modules, which is characterized by comprising the steps of: feeding a mixed gas containing a halide gas to a gas inlet of a first stage separation membrane module; feeding, to a gas inlet of each of a second and any following stage separation membrane modules, a permeate gas of an immediately preceding stage separation membrane module; recycling a non-permeate gas of each of the second and any following stage separation membrane modules to the gas inlet of the first stage separation membrane module; and collecting a non-permeate gas of the first stage separation membrane module with a prescribed halide gas concentration while controlling the non-permeate gas flow from the first stage separation membrane module with a gas flow control valve connected to the non-permeate gas outlet of the first stage separation membrane module.