Air separation is simply the process of using physical methods to separate the various components of an air mixture to obtain high-purity oxygen and high-purity nitrogen as well as some rare gases.
The main components in the air are oxygen and nitrogen, which exist in a molecular state and are evenly mixed together, and it is usually difficult to separate them out. At present, there are three main methods to realise air separation in the industry, such as deep cooling method, adsorption method and membrane separation method.
Deep-cooling method (also known as low-temperature method) separation principle: the first mixture of air through compression, expansion and cooling until the air liquefaction, and then the use of oxygen, nitrogen vaporization temperature (boiling point) of the different (in the standard atmospheric pressure, the boiling point of oxygen -183 ℃; nitrogen's boiling point of -196 ℃, the boiling point of nitrogen relative to the oxygen to be easy to vaporize the Characteristics, in the distillation tower so that the higher temperature steam and the lower temperature of the liquid is constantly in contact with each other, low boiling point components of nitrogen more evaporation, high boiling point components of oxygen more condensation of the principle, so that the rising vapour nitrogen content is constantly increasing the oxygen content of the liquid in the downstream is constantly increasing, so as to achieve the separation of oxygen and nitrogen. To liquefy the air, the air needs to be cooled to a temperature below -173 ℃, this refrigeration is called deep freezing (deep freezing); and the use of boiling point difference will be separated into liquid air oxygen, nitrogen, argon process is called the distillation process. The combination of deep freezing and distillation is currently the most widely used air separation method in industry.
