The chemical property of nitrogen is not active. It is inert in normal state and is not easy to react with other substances. Therefore, nitrogen is widely used as protective gas in glass, oil refining, metallurgy, electronic and chemical industries, and its application prospect is very broad.

      The distillation tower includes a turbine expander, a main heat exchanger and a subcooler for heat exchange, a distillation tower and a condensing evaporator. The distillation tower includes an upper tower and a lower tower. The outlet of the purification system is connected to the air inlet of the lower tower through a pipeline which passes through the main heat exchanger.