The distillation column in an air separation unit is the core component of the air separation process. Its function is to efficiently separate and purify the main components of air (oxygen, nitrogen, argon, etc.) based on their boiling point differences through physical distillation methods.
The distillation tower achieves air separation through a multistage distillation process, utilizing the differences in boiling points of various components. The interior of the distillation tower is filled with trays or packing materials, forming multistage separation units. Steam from the reboiler (or the top of the lower tower) carries light components (such as nitrogen) upwards. Liquid from the condenser (or the bottom of the upper tower) carries heavy components (such as oxygen) downwards. On each level of trays or packing layers, the gas and liquid phases fully contact each other, undergoing mass and heat transfer. Light components (nitrogen) transfer from the liquid phase to the gas phase and are enriched upwards. Heavy components (oxygen) transfer from the gas phase to the liquid phase and are enriched downwards. Through multistage equilibrium, high-purity nitrogen is finally obtained at the top of the tower, and high-purity oxygen is obtained at the bottom of the tower.
The cold energy generated during the distillation process is recycled through the condenser and reboiler to reduce energy consumption. The argon fraction is extracted from the side line in the middle of the upper column and sent to the crude argon column and the refined argon column for further purification, ultimately obtaining high-purity argon gas. Through the distillation process, high-boiling-point impurities such as carbon dioxide and moisture in the air are concentrated and discharged at the bottom of the column, ensuring the purity of the product gas.
