LDH GAS series liquid nitrogen equipment is based on the pressure swing adsorption principle, using high-quality carbon molecular sieve as adsorbent, under a certain pressure, from the air to produce nitrogen. After purifying and drying compressed air, pressure adsorption and decompression desorption are carried out in the absorber. Due to the kinetic effect, the diffusion rate of oxygen in the micropores of carbon molecular sieve is much higher than that of nitrogen. When the adsorption is not in equilibrium, nitrogen is enriched in the gas phase to form the finished nitrogen. Then decompression to atmospheric pressure, adsorbent adsorption of oxygen and other impurities, to achieve regeneration. Generally, two adsorption towers are set up in the system. One tower absorbs nitrogen and the other tower is desorption and regeneration. Automatic control by PLC program makes the two towers work alternately. The finished nitrogen is then passed through the refrigerator to produce liquid nitrogen.