DEAR air separation continues to make breakthroughs and innovations, and the field of development has become wider and wider, and always adhere to the "quality is our pride" concept. Adopt molecular sieve adsorption, full-low pressure process technology of turboexpander refrigeration. The device includes: an air filtration system, an air compression system, an air pre-cooling system, a molecular sieve purification system, a turbine expansion unit, an oxygen pressure system, a nitrogen pressure system, a liquid storage system, an instrument control system, and an electronic control system. After removing the mechanical impurities such as dust in the air filter, the raw air enters the air turbine compressor, compresses the air to the required pressure, and then enters the air cooling tower for heat exchange with water and then enters two alternate molecular sieve adsorption. Device, where impurities such as moisture, CO2, C2H2 in the raw air are adsorbed by the molecular sieve. Part of the gas is drawn from the middle of the main heat exchanger, enters the expander, and the expanded air enters the upper tower. After the air enters the main heat exchanger, it is cooled to the saturation temperature by the return gas and enters the lower tower with a small amount of liquid. After the air is initially rectified by the lower tower, an oxygen-enriched liquid air is obtained in the lower tower. After the liquid air is cooled by the cooler, it is throttled into the upper tower. After the upper tower is further rectified, oxygen at the bottom of the upper tower is obtained with a purity of 99.6% The oxygen of this product is reheated by the main heat exchanger and then sent out to the user after being discharged from the cold box. 99.999% nitrogen is obtained from the top of the upper tower, and it is returned to the cold box after being reheated by the cooler and the main heat exchanger. The polluted nitrogen is led out from the top of the upper tower, reheated by the cooler and the main heat exchanger, and then exits the cold box. After being heated by the regeneration heater, it is used as the molecular sieve regeneration gas and the excess gas is vented.