Air separation unit is to separate air into oxygen and other gases. Its principle is to compress and cool the air into liquid, and then use the different boiling points of oxygen and other gases in the air to obtain oxygen, liquid oxygen and other rare gases by evaporation.
It mainly includes the following basic processes:
(1) After the air is filtered, it enters the compressor, the air pressure reaches a certain requirement, and then the compressed air is cooled to about - 55 ℃;
(2) The compressed and cooled air is sent to the water cooling tower for further cooling, drying and re cleaning at the same time, and then entering the molecular sieve to remove water vapor and other harmful gases;
(3) After the molecular sieve is discharged, it is sent to the main cooling and heat exchange unit (tower), and the temperature is further reduced to - 120 ℃. A small part of it is pressurized by the expander (up to 10kg pressure), cooled, throttled and depressurized to 1-2kg pressure, and cooled to - 200 ℃ (liquid state);
(4) The liquid air at - 200 ℃ is used to cool the air at - 120 ℃ to below - 196 ℃;
(5) The liquid air below - 196 ℃ enters the distillation column for heating, and the nitrogen with boiling point of - 196 ℃ first evaporates from the liquid air, leaving behind liquid oxygen (its boiling point is - 182 ℃).
(6) If you want to get other gases, such as argon, nitrogen and so on, you need to enter the distillation tower again to distill other gases.
