During the start-up phase of an air separation plant, the refrigeration capacity is mainly used to cool the unit and reduce its temperature. Since all parts of the equipment operate at ambient temperature, refrigeration is needed to gradually lower the temperature and build up the liquids required for distillation in the column. The cooling capacity consumed in this phase is mainly used for cooling the equipment and accumulating the liquid.
In the normal operation stage, it is mainly used to make up for the loss of cold running, incomplete loss of heat exchange, the cold volume taken away by liquid products and other cold volume loss. When the air separation equipment operates at low temperature, the external heat will be continuously transferred into the equipment, resulting in cold loss. This kind of cold loss caused by external heat transfer is called running cold loss. In the process of heat exchange, due to the existence of temperature differences within the heat exchanger, resulting in incomplete recovery of cold. This kind of cold loss caused by incomplete heat exchange is called incomplete heat exchange loss. When the air separation equipment to produce liquid products (such as liquid oxygen, liquid nitrogen, liquid argon, etc.), these low-temperature products will take away part of the cold.
In order to maintain stable working conditions, air separation equipment production of refrigeration needs to be equal to the cold loss and cold consumption, that is, to achieve “cold balance”.
