The main components of air are oxygen, nitrogen, argon, carbon dioxide and some other gases and impurities. They exist as molecules in the air, numerous and never stop making irregular movements. Mix them together evenly to separate, there are three main methods: cryogenic, adsorption, and membrane separation.
The air separation device of cryogenic method has many advantages such as stable operation, low maintenance cost, simple operation, large output adjustment range and high product quality, which can produce liquid as spare products.
The principle of cryogenic air separate method is based on the different boiling points of each component in the air, by pressurized precooling and purification, and liquified by using the most cooling quantity provided by turbine and then rectified to obtain the required liquid oxygen, oxygen, nitrogen, liquid nitrogen and other rare gases. The specific principle is after purification, the air is cooled to the condensation temperature in cold box, and then enters the rectifying column for rectification. As an ascending gas, descending fluid from the top of column for heating and mass exchange. The liquid with low temperature absorbs heat and begins to evaporate. The nitrogen component is firstly vaporized, and the higher temperature gas condenses, and the heat of condensation is released. When the gas condenses, the oxygen component is first condensed. This process continues until the gas and liquid are in equilibrium. At this time, due to the liquid phase evaporation, reducing nitrogen composition, at the same time because of gas condensate oxygen into the liquid phase, so oxygen concentration of liquid phase increased. Meanwhile, due to gas phase condensate, reducing oxygen composition, liquid phrase nitrogen into the gas phase, so the gas phase of the nitrogen concentration increased. Repeat the above process many times, the gas phase of nitrogen concentration is increased, the liquid oxygen concentration can also increasing. So after a lot of evaporation and condensation can complete the whole rectification process, which will be separating oxygen and nitrogen in the air.
Cryogenic separate of air separation plant can produce gaseous & liquid oxygen，nitrogen, argon and other products at the same time, which is with high extraction rate. Equipment maintenance cost is very low, which can run continuously for two years without stopping (Several sets of plant of XLA have been running continuously for 15 years without large heating, also did not change the molecular sieve and alumina). Valve service life is nearly 20 years, and adsorbent service life normal operation can be more than eight years (with useage record), and the price of adsorbent is very cheap, and the cost of the whole equipment is less than 1%.
