Process for low-temperature separation of air

Claim 1

A process for low temperature separation of air which comprises removing dust from air; compressing the dedusted air to 180-200 kg/cm 2 ; purifying the compressed air by removing carbon dioxide and acetylene therefrom, drying to a due point of -60° C. to -70° C. and cooling at a temperature below the condensation temperature, thus partially condensing the air; subjecting the cooled and partially condensed air to primary rectification in a high pressure column to produce, at the top reflux condenser, liquified nitrogen containing less than 0.5 vol.% of oxygen and argon and at the bottom of the column oxygen-enriched liquified air containing 32-36 vol.% of oxygen, 1.5-1.8 vol.% of argon and 60.2-66.5 vol.% of nitrogen; supercooling said liquified nitrogen and oxygen-enriched air; subjecting the supercooled air enriched with oxygen to secondary rectification by said supercooled liquified nitrogen in a low pressure column, to obtain from the top of said low pressure column gaseous nitrogen containing less than 0.3 vol.% of oxygen and argon impurities, a gaseous oxygen-argon mixture containing 7-10 vol.% of argon and a liquified oxygen-argon mixture containing up to 4.5 vol.% of argon and less than 0.01 vol.% of nitrogen; and subjecting said gaseous oxygen-group mixture to a further rectification in a second low pressure column to produce an argon-oxygen mixture containing argon with impurities of 3-0.1 vol.% of oxygen and less than 0.1 vol.% of nitrogen, as well as oxygen with a concentration of 99.7-99.9 vol.% oxygen.