Method of air separation

A method of air separation by low-temperature rectification comprising the following steps:

• compressing said air;
• purifying said compressed air;
• cooling said purified air;
• separating not less than 70% by volume of said cooled air in a high-pressure column of a double rectifier into liquid air enriched with oxygen, and liquid nitrogen;
• separating said liquid air enriched with oxygen and said liquid nitrogen in a low-pressure column of said double rectifier into oxygen, nitrogen gas and gaseous argon fraction containing not more than 0.5% by volume of nitrogen;
• liquefying said gaseous argon fraction;
• separating said argon fraction after said liquefaction in a rectifying column into at least one argon-nitrogen fraction and a liquid fraction of high-boiling components under a pressure exceeding a condensing pressure of said argon-nitrogen fraction by a value of from 0.01 to 0.06 MPa;
• heating, compressing and cooling a part of said nitrogen gas taken from said low-pressure column, the amount of said nitrogen gas being not more than 30% of the volume of the air being processed;
• introducing said cooled part of said nitrogen gas into said double rectifier;
• introducing said cooled air into an evaporator of said rectifying column to deliver heat and forming liquid air;
• throttling said liquid air;
• introducing said throttled air into a condenser of said rectifying column to deliver heat and forming gaseous air;
• separating said gaseous air in said double rectifier.