The core of cryogenic air separation is to liquefy air at low temperature. Its ideal cycle covers compression, expansion (refrigeration) and reheating processes. The simple Linde cycle in practical application includes compression, reheating and throttling processes. Air separation is mainly completed in the distillation tower, thus forming four indispensable processes: compression, refrigeration, reheating and distillation. Correspondingly, the cryogenic air separation process is also composed of four modules: air compression and pretreatment, refrigeration, heat exchange and distillation. Among them, the organization form of refrigeration, heat exchange and distillation modules is flexible and changeable, which becomes the decisive factor of different air separation processes.
In terms of product pressure acquisition, the gas product can be compressed by a compressor, or the liquid product can be pressurized by a liquid pump, and then output after vaporization and reheating in a heat exchanger. At present, the basic cryogenic air separation process includes external compression air separation process, internal compression air separation process, oxygen self-pressurization air separation process, full liquid air separation process, three-tower air separation process, LNG cold energy utilization air separation process, high nitrogen air separation process and air separation process with rare gas.
These processes each have their own characteristics and advantages, and are suitable for different industrial scenarios and needs. They provide high-purity oxygen, nitrogen and other key gases for many industries such as steel, chemicals, and electronics, and have effectively promoted the efficient and refined development of industrial production.
