PSA device is used to produce nitrogen by using the compressed air as raw material and applying the principle and technology of pressure swing adsorption. It uses carbon molecular sieve as adsorbent. Under certain pressure, carbon molecular sieve’s adsorption to oxygen in the air is much bigger than that of nitrogen in the air. Two adsorption towers-A and B can adsorb by adding pressure and desorb by reducing pressure alternately during which the oxygen and nitrogen will be separated, and the   nitrogen with required purity will be produced.