Air separation unit is a kind of unit that takes air as raw material, transforms air into liquid by low temperature cryogenic method which compresses and circulates air, and then gradually separates oxygen, nitrogen, argon and other inert gases from liquid air by distillation.
At present, the air separation unit produced in China has many forms and types. There are unit for the production of gaseous oxygen and nitrogen, as well as unit for the production of liquid oxygen and nitrogen. However, there are four types of basic processes: high pressure, medium pressure and low pressure, and full low pressure process. The production scale of air separation unit in China has developed from the original oxygen generator which can only produce 20m³/ h (oxygen) to the current large-scale air production capacity of 20000 m³/ h, 30000 m³/ h and 50000 m³/ h (oxygen).
The air separation unit can be divided into 5 basic systems in terms of process
1.Impurity purification system: the mechanical impurities, moisture, carbon dioxide, acetylene, etc. mixed in the air are purified by air filter and molecular sieve absorber.
2.Air cooling liquefaction system: it is mainly composed of air compressor, heat exchanger, expander and air throttle valve, which plays a role in the deep freezing of air.
3.The main components of the system are as follows: Distillation column (upper column, lower column), condensing evaporator, subcooler, liquid air and liquid nitrogen throttle valve. Play the role of separating various components in the air.
4.Heating sewage system: regeneration and purification system by heating sewage discharge method.
5.Instrument control system: the whole process is controlled by various instruments.
