1、 Principles and Methods of Refrigeration
Expansion refrigeration: This is the core method of low-temperature refrigeration in air separation equipment. High pressure gas expands adiabatically inside the expander, while doing external work, the temperature decreases, achieving refrigeration effect.
Throttle valve refrigeration: Isothermal expansion, which reduces the pressure and temperature of high-pressure gas through the throttle valve, but the refrigeration efficiency is relatively low compared to the expander.
Reverse Brayton cycle refrigeration: using gas bearing expander to achieve refrigeration, with high efficiency and stability.
2、 Key equipment and functions
Expansion machine: The core equipment of a refrigeration system that reduces temperature through gas expansion, provides necessary cooling capacity, and cools air to liquefaction temperature for separation. There are generally three types of expanders: low-pressure expanders, medium pressure expanders, and liquid expanders, and their efficiency is closely related to the volume flow rate of the working fluid.
Refrigerant circulation system: In some high demand air separation equipment, the pre cooling system will also be equipped with a refrigerant circulation system. The refrigerant circulates in the pre cooling system, reducing the air temperature by absorbing heat from the air. This method can more accurately control the air temperature and ensure the optimal pre cooling effect.
3、 System optimization and collaborative work
Cold balance: The cold generated by the refrigeration system is transferred to the air to be cooled through the heat exchange system, achieving effective utilization of the cold. At the same time, the heat exchange system can also recover some of the cooling capacity and provide feedback to the refrigeration system to maintain the balance of cooling capacity.
Collaboration with other systems: The refrigeration system works closely with the pre cooling system, heat exchange system, distillation system, etc. The pre cooling system lowers the air temperature and reduces the cooling load; The heat exchange system achieves energy transfer and improves economy; The distillation system utilizes the cooling capacity provided by the refrigeration system for air separation.
