Method and device for generating gaseous compressed nitrogen

A method for generating gaseous compressed nitrogen by low-temperature separation of air in a distillation column system having a pre-column which has a pre-column head condenser/evaporator having a liquefaction chamber and an evaporation chamber, a high-pressure column and a low-pressure column, said process comprising:

• compressing input air in a main air compressor to form compressed input air,
• cleaning the compressed input air in a cleaning device to form cleaned input air,
• cooling the cleaned input air in a main heat exchanger to form cooled input air,
• feeding a first partial stream of the cooled input air in gaseous form into the pre-column,
• feeding a second partial stream of the cooled input air in a predominantly liquid state into the distillation column system,
• feeding a gaseous fraction from an upper region of the pre-column into the liquefaction chamber of the head condenser/evaporator wherein liquid is formed in said liquefaction chamber, and
• returning at least part of the liquid formed in the liquefaction chamber to the pre-column,
• wherein said low-pressure column has a low-pressure column sump condenser/evaporator which has a liquefaction chamber and an evaporation chamber,
• withdrawing a first nitrogen product fraction from the high-pressure column in gaseous form, warming said first nitrogen product fraction in the main heat exchanger, and removing warmed first nitrogen product fraction from the main heat exchanger to form a first gaseous compressed nitrogen product,
• feeding at least a first substream of the second partial stream into the evaporation chamber of the pre-column head condenser/evaporator,
• subjecting a third partial stream of the cooled input air to pressure reduction whereby work is performed,
• wherein, after said pressure reduction, the third partial stream has a pressure which is higher than an operating pressure of the low-pressure column,
• wherein, after said pressure reduction, the third partial stream is fed into the liquefaction chamber of the low-pressure column sump condenser/evaporator and is at least partly liquefied there to form liquefied third partial stream,
• feeding at least a substream of the liquefied third partial stream into the low-pressure column, wherein said sub stream of the liquefied third partial stream is liquefied air,
• wherein the low-pressure column has an intermediate condenser/evaporator having a liquefaction chamber and an evaporation chamber,
• evaporating at least part of an intermediate liquid of the low-pressure column in the evaporation chamber of the intermediate condenser/evaporator,
• liquefying at least part of a gaseous head fraction from the high-pressure column in the liquefaction chamber of the intermediate condenser/evaporator to form liquid, and returning at least part of the liquid formed in the liquefaction chamber of the intermediate condenser/evaporator to the high-pressure column,
• wherein said first gaseous compressed nitrogen product is more than 35 mol % of said input air, and
• wherein less than 30 mol % of said input air is fed in the liquid state into the distillation column system.

A method for generating gaseous compressed nitrogen by low-temperature separation of air in a distillation column system having a pre-column which has a pre-column head condenser/evaporator having a liquefaction chamber and an evaporation chamber, a high-pressure column and a low-pressure column, said process comprising:

• compressing input air in a main air compressor to form compressed input air,
• cleaning the compressed input air in a cleaning device to form cleaned input air,
• cooling the cleaned input air in a main heat exchanger to form cooled input air,
• feeding a first partial stream of the cooled input air in gaseous form into the pre-column,
• feeding a second partial stream of the cooled input air in a predominantly liquid state into the distillation column system,
• feeding a gaseous fraction from an upper region of the pre-column into the liquefaction chamber of the head condenser/evaporator wherein liquid is formed in said liquefaction chamber, and
• returning at least part of the liquid formed in the liquefaction chamber to the pre-column,
• wherein said low-pressure column has a low-pressure column sump condenser/evaporator which has a liquefaction chamber and an evaporation chamber,
• withdrawing a first nitrogen product fraction from the high-pressure column in gaseous form, warming said first nitrogen product fraction in the main heat exchanger, and removing warmed first nitrogen product fraction from the main heat exchanger to form a first gaseous compressed nitrogen product,
• feeding at least a first substream of the second partial stream into the evaporation chamber of the pre-column head condenser/evaporator,
• subjecting a third partial stream of the cooled input air to pressure reduction whereby work is performed,
• wherein, after said pressure reduction, the third partial stream has a pressure which is higher than an operating pressure of the low-pressure column,
• wherein, after said pressure reduction, the third partial stream is fed into the liquefaction chamber of the low-pressure column sump condenser/evaporator and is at least partly liquefied there to form liquefied third partial stream,
• feeding at least a substream of the liquefied third partial stream into the low-pressure column, wherein said sub stream of the liquefied third partial stream is liquefied air,
• wherein the low-pressure column has an intermediate condenser/evaporator having a liquefaction chamber and an evaporation chamber,
• evaporating at least part of an intermediate liquid of the low-pressure column in the evaporation chamber of the intermediate condenser/evaporator,
• liquefying at least part of a gaseous head fraction from the high-pressure column in the liquefaction chamber of the intermediate condenser/evaporator to form liquid, and returning at least part of the liquid formed in the liquefaction chamber of the intermediate condenser/evaporator to the high-pressure column,
• wherein said first gaseous compressed nitrogen product is more than 35 mol % of said input air, and
• wherein, after said reducing, the pressure of the third partial stream is lower than an operating pressure of the high-pressure column.