Industrial gas is referred to as the "blood" of industry. The function of air separation unit is to provide industrial gas needed in production. As an important basic raw material of modern industry, gas products are widely used, so the demand of air separation unit has been a lot. Large scale air separation unit is mainly used in coal chemical industry, chemical fertilizer, petrochemical industry, metallurgy industry and IGCC power generation enterprises, while small and medium-sized air separation unit is mainly used in small and medium-sized metallurgical, chemical, building materials, electronic enterprises.