| abstract |
Provided are a nitrogen production method having high nitrogen recovery rate and a high energy efficiency for producing liquid nitrogen, and a nitrogen production apparatus. A part of the raw material air is expanded by cooling at the front end of the main heat exchanger 1 and cooled, and the remaining raw material air which is not expanded is used as a cold to preheat inside the main heat exchanger 1. In addition, a part of the preheated raw air inside the main heat exchanger 1 is taken out of the main heat exchanger 1 to expand and cool, and the remaining unexpanded preheated raw air is cooled inside the main heat exchanger 1. It is used as cold to do. |