Patent ID: 7670408

Claim:
A process for separating nitrogen, wherein a feed gas made up mainly of nitrogen is fed under pressure to one of at least two adsorption columns packed with molecular sieve carbon to conduct high pressure adsorption, the one of at least two adsorption columns having completed high pressure adsorption is subjected to low pressure desorption, and the alternating cycle of the high pressure adsorption and the low pressure desorption are repeated in each adsorption column to separate nitrogen gas product, wherein the molecular sieve carbon has 0.7 wt % or less ignition residue and the following relationships (I) and (II) are satisfied: (1)ln C≦ 0.325+5.14×ln {(0.64+0.098)× Q /( P+ 0.098)} (I) (2)ln U≦ 2.124−0.135×ln C (II) where C indicates an oxygen level (ppm) in the nitrogen gas product; Q indicates a volume of nitrogen gas produced per minute per unit effective volume of a single adsorption column; P indicates an adsorption pressure (MPa); and U indicates a ratio of the volume of the feed air to the volume of the nitrogen gas produced.