PROCEDE DE SEPARATION CRYOGENIQUE D'UN DEBIT D'ALIMENTATION CONTENANT DU METHANE ET DES GAZ DE L'AIR, INSTALLATION POUR LA PRODUCTION DE BIO METHANE PAR EPURATION DE BIOGAZ ISSUS D'INSTALLATIONS DE STOCKAGE DE DECHETS NON-DANGEREUX (ISDND) METTANT EN ŒUVRE LE PROCEDE

A process for cryogenic separation of a feed stream containing methane and air gases in which: the feed stream is cooled in order to produce a cooled stream, at least one portion of the cooled stream is sent to one level of a distillation column, a bottom stream is drawn off from the distillation column, the bottom stream being enriched in methane relative to the feed stream, a stream enriched in oxygen and in nitrogen relative to the feed stream is drawn off from the distillation column, at least one noncombustible dilution stream that is more volatile than oxygen is introduced into the distillation column at at least one level lower than the one at which the cooled stream is introduced. The dilution stream is extracted from the feed stream. Facility for producing biomethane by purification of biogases derived from non-hazardous waste storage facilities (NHWSF) implementing the process.