Basic method of industrial production of oxygen

In industrial production, the method of producing oxygen basically adopts liquid air fractionation method, which can produce oxygen on a large scale. So, what is the specific process of this method? What kind of principle is it based on? Let's take a look.
The liquid air fractionation method is used to produce oxygen industrially. First, the air passes through the filter to remove solid impurities such as dust, enters the compressor for compression, and then passes through the molecular sieve purifier to remove impurity gases such as water vapor and carbon dioxide. Here, molecular sieves can pass smaller molecules such as nitrogen and oxygen, and play the role of screening molecules. Then cool down and depressurize. When the temperature drops to about -170°C, the air begins to partially liquefy and enters the rectification tower, where fractional distillation is carried out according to the different boiling points of the gases in the air. The boiling point of liquid oxygen is higher than that of liquid nitrogen, and the two are more easily vaporized than liquid nitrogen. More than 99% pure oxygen can be obtained through multi-step fractional distillation, and nitrogen and raw materials for extracting rare gases can be obtained at the same time.
This method is complex. If oxygen with low purity is needed, molecular sieve adsorption method can be used to separate air to obtain oxygen. Specific molecular sieves have a higher adsorption capacity for nitrogen than oxygen. When the air passes through the molecular sieve bed, the outflow gas has a higher oxygen content. After repeated adsorption, a gas containing 70-80% oxygen can be obtained. This method is operated at normal temperature, has a short cycle time and is easy to realize automation.