Process for obtaining gaseous nitrogen

A process for obtaining gaseous nitrogen by low-temperature separation from air in a distillation column system, having a single column (4), comprising the following stages:

• compressed air is cooled in a main heat exchanger, and fed to single column;
• a nitrogen-rich fraction is drawn off from the distillation column system and is compressed, at least in part, in a circulation compressor;
• a first part of compound nitrogen-rich fraction is fed downstream from the circulation compressor to a liquefaction chamber of a condenser-evaporator and is condensed therein under a pressure higher than the operating pressure of the single column, thereby forming a nitrogen-rich liquid;
• a liquid, oxygen-enriched fraction is withdrawn from the distillation column system and is at least partially evaporated in an evaporation chamber of the condenser-evaporator;
• a first oxygen-enriched gas is withdrawn from the evaporation chamber and introduced into the single column, as ascending vapor;
• and
• a second part of the compressed nitrogen-rich fraction is withdrawn at least at times as gaseous nitrogen product, and wherein
• a second oxygen-enriched gas is withdrawn from the evaporation chamber of the condenser-evaporator, is work expanded, and is heated in the main heat exchanger, and wherein air compressors and circulation compressors (9) are formed by a single machine.

Apparatus for obtaining gaseous nitrogen by low-temperature separation from air with a distillation column system comprising a single column (4), an air compressor, a main heat exchanger, passage means for feed air, between the single column (4) from the air compressor through the main heat exchanger (2),

• a circulation compressor (9, 1063) for compression of the first portion of a nitrogen-rich fraction (5, 7, 8) from the distillation column system,
• a circulation line (12, 13), from the outlet of circulation compressor (1063, 9) to a liquefaction chamber of a condenser-evaporator (14),
• means for feeding a liquid, oxygen-enriched fraction from the distillation column system to the evaporation chamber of condenser-evaporator (14),
• means for the production of a first oxygen-enriched gas (234, 533) from vapor (232) formed in the evaporation chamber of the condenser-evaporator (14) and for introduction into the single column (4) and a
• a gas production line for drawing off a second portion (19, 20, 1064) of nitrogen-rich fraction (5, 7, 8) as a gaseous nitrogen product, said apparatus further comprising
• a machine (23) for engine expanding a second oxygen-enriched gas (221, 521) from the evaporation chamber of condenser-evaporator (14), and conduits leading from said evaporation chamber to said machine.

A process for obtaining gaseous nitrogen by low-temperature separation from air in a distillation column system, having a single column (4), comprising the following stages:

• compressed air is cooled in a main heat exchanger, and fed to single column;
• a nitrogen-rich fraction is drawn off from the distillation column system and is compressed, at least in part, in a circulation compressor;
• a first part of compound nitrogen-rich fraction is fed downstream from the circulation compressor to a liquefaction chamber of a condenser-evaporator and is condensed therein under a pressure higher than the operating pressure of the single column, thereby forming a nitrogen-rich liquid;
• a liquid, oxygen-enriched fraction is withdrawn from the distillation column system and is at least partially evaporated in an evaporation chamber of the condenser-evaporator;
• a first oxygen-enriched gas is withdrawn from the evaporation chamber and introduced into the single column, as ascending vapor;
• and
• a second part of the compressed nitrogen-rich fraction is withdrawn at least at times as gaseous nitrogen product, and wherein
• a second oxygen-enriched gas is withdrawn from the evaporation chamber of the condenser-evaporator, is work expanded, and is heated in the main heat exchanger, and wherein the second oxygen-enriched gas is disposed of in the atmosphere or is used as regeneration gas in an air purification system or is used as gaseous by-product.