Air is a mixture of various gases. Oxygen air separation plant uses air as raw material to liquefy, distill and finally separate air into oxygen, nitrogen and other high-purity gases. At present, there are many kinds of air separation plant in China, which can meet the specific needs of different industries. There are four basic processes of air separation in the oxygen air separation plant: high pressure, medium pressure, high low pressure and full low pressure processes. Therefore, there is a distinction between large and small oxygen air separation plant. The price of small air separation plant is not very high compared with that of large air separation plant.