DEAR air separation combined with international advanced technology ensures that the equipment is safer and more reliable, and has won unanimous praise from users. Adopt molecular sieve adsorption, full-pressure low-pressure process technology of turboexpander refrigeration. This device includes: air filtration system, air compression system, air pre-cooling system, molecular sieve purification system, turbine expansion unit, oxygen pressure system, nitrogen pressure system, liquid storage system, instrument control system, electric 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 column. 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 column, an oxygen-enriched liquid air is obtained in the lower column. After the liquid air is cooled by the cooler, it is throttled into the upper column. After the upper column is further rectified, oxygen at the bottom of the upper column 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 column, 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 column, 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.