Three columns method and - device for the low-temperature separation of air

摘要

A method for obtaining a gaseous pressure nitrogen product by low-temperature separation of air in a three columns system consisting of a high pressure column (7), of an additional column (8) and a low-pressure column (9), with the following steps:(a) introducing a first part (101, 103, 104) of compressed feed air (3, 4) in the pressure column (7);(b) introducing a second part (201, 202) of the compressed air (3, 4) in the additional column (8);(c) pulling off a first oxygen-enriched liquid fraction (18) from the high pressure column (7);(d) the introduction of at least one first part (19) of the first oxygen-enriched liquid fraction (18) into the low-pressure column (9);(e) generating a second oxygen-enriched liquid fraction (26) in the additional column (8);(f) generating a third oxygen-enriched liquid fraction (30) in the low-pressure column (9);(g) generating a first nitrogen-enriched liquid fraction (50) by condensation of a first nitrogen-enriched top gas (55, 10) from the high pressure column (7) by indirect heat exchange with the third oxygen-enriched liquid fraction (30) in a first capacitor - evaporator..