The raw air is compressed to 0.7~0.85MPa by the air compressor, and then the air is pre-cooled to 5~10°C in the pre-cooling unit to separate most of the water. The remaining water, carbon dioxide and hydrocarbons are filtered out by adsorption in the cryogenic purifier. The air is then refrigerated in an expander to provide the cooling required by the unit. The air exchanges heat with the returning oxygen, nitrogen and dirty nitrogen in the main heat exchanger of the fractionation tower, is cooled to close to the liquefaction temperature and reheats the returning oxygen, nitrogen and dirty nitrogen to the ambient temperature. Nitrogen subcools liquid air and liquid nitrogen before throttling in the subcooler. The air is rectified and separated in the rectifying tower, the product nitrogen is obtained at the top of the upper tower, and the product oxygen is obtained at the bottom of the upper tower.

 

 

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