Patent ID: 6276172
Filing Date: 2001-08-21
Classification: F25J,Y10S

Abstract:
A process for producing ultrapure nitrogen by low-temperature fractionation of air in a rectification system having at least one rectification column, said process comprising providing an oxygen-free pressurized nitrogen fraction, characterized in that the oxygen-free pressurized nitrogen fraction is expanded into a bottom-heated low-pressure column, ascending vapour being formed in the low-pressure column and being freed from carbon monoxide using a reflux of ultrapure nitrogen applied at the top of the low-pressure column, the resultant ascending vapor being taken off at the top of the low-pressure column as carbon-monoxide-free overhead gas and after a pressure increase being partly liquefied and the liquefied part being expanded into a bottom-heated He--Ne--H.sub.2 column from which the ultrapure nitrogen is taken off in the liquid state.