The working principle of nitrogen generating device can be divided into three categories: PSA pressure swing adsorption nitrogen generation principle, cryogenic air separation nitrogen generation principle, membrane air separation nitrogen generation principle. Cryogenic nitrogen generating device is a traditional method of nitrogen production, which uses air as raw material, through compression, purification and heat exchange to liquefy gas. Using the different boiling points of oxygen and nitrogen in liquid state, the gas can be separated by rectifying the mixture to obtain nitrogen.