Cryogenic Air Separation Backflow Expansion

The cryogenic air separation reflux expansion process is generally applicable to occasions where the user has certain requirements on the pressure of the nitrogen product (such as higher than 0.2MPa), and its process is shown in the figure. The raw air enters the main heat exchanger after dedusting, compression, precooling and purification, and is cooled to the saturation temperature by the backflow of dirty nitrogen with a certain moisture content, then enters the bottom of the nitrogen tower to participate in rectification. In this way, the product liquid nitrogen and nitrogen gas are obtained at the top of the nitrogen tower; and the oxygen-rich liquid air at the bottom of the nitrogen tower is throttled and then enters the evaporation side of the condensing evaporator to condense the gas nitrogen at the top of the nitrogen tower.

 

Most of the oxygen-enriched air extracted from the top of the condensing evaporator directly enters the cold end of the main heat exchanger, is reheated to a certain temperature, and is extracted from the middle, and enters the turbo expander for expansion to provide cooling capacity for the entire pure nitrogen equipment. The expanded oxygen-enriched air is mixed with another throttling oxygen-enriched air and then enters the cold end of the main heat exchanger to exchange heat with the positive flow air. After reheating to normal temperature, it is discharged from the cold box, and part of it is used for Regeneration of the molecular sieve adsorber, the rest is vented. The nitrogen gas drawn from the top of the ammonia tower is reheated by the main heat exchanger to normal temperature and then exits the cold box to be supplied to users.

 

 

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