Purification/recycling procedure and installation for helium used in manufacture of optical fibres uses cryogenic refrigeration and permeation

摘要

The procedure consists of two or more stages, including the cryogenic refrigeration of the impure helium, using indirect contact with liquid nitrogen to eliminate by condensation at least part of the main impurities, and permeation through one or more membranes, and preferably several in sequence to remove at least a part of the residual impurities and permit recuperation of helium that is purer than at the intermediate stage, and preferably with a purity of 99 to 99.9 per cent. The procedure can be preceded by a pre-purification stage in which at least a part of CO2 and/or H2O impurities are removed. The procedure is carried out in an installation with a compressor (3) before the pre-purification stage (8) and the cryogenic refrigeration plant (1), which is followed by the permeation unit (2).