Principle and operation of air separation unit: at present, there are many forms and types of air separation unit produced in China. There are mainly four basic processes: high pressure, medium pressure, high and low pressure and full low pressure process. With the expansion of production scale, the demand for oxygen and nitrogen is increasing. At the same time, the correct operation of air separation unit is of great importance, which is related to the safety of air separation unit and the long-term stable operation of production unit.