During the start-up phase of air separation equipment, the refrigeration capacity is mainly used for:
1. Cooling device, reducing temperature: As each part of the device is at room temperature during the initial start-up, it is necessary to gradually lower the temperature of each part of the device through refrigeration to achieve the low-temperature environment required for normal operation. At this point, the cooling capacity is mainly consumed for equipment cooling.
2. Generate liquid air and accumulate liquid: As the temperature decreases, water vapor in the air condenses into liquid water and further accumulates the liquid required for distillation inside the tower. During this process, the cooling capacity is also used to promote the generation and accumulation of liquid air.
During the normal operation phase of the air separation equipment, the refrigeration capacity is mainly used for:
1. Compensating for the loss of cold running: Due to the low operating temperature of the air separation unit, despite the addition of insulation materials such as pearl sand, the surrounding air temperature is higher than the temperature inside the unit, and some heat is still transferred into the cold box, causing the temperature of low-temperature objects to rise, thereby consuming some of the cooling capacity.
2. Compensating for incomplete heat exchange loss: In the process of air separation, the cooling capacity of low-temperature objects is mainly recovered through heat exchange equipment (such as heat exchangers). However, due to the limitations of the second law of thermodynamics, a driving force (i.e. temperature difference) is required during the heat transfer process, so there must be a temperature difference inside the heat exchanger, which leads to incomplete recovery of cooling capacity.
3. The cooling capacity carried away by liquid products: When some of the liquid products produced by the device (such as liquid oxygen, liquid nitrogen, liquid argon, etc.) are output from the device, these low-temperature products will take away a portion of the cooling capacity. In order to maintain a low temperature environment inside the device, it is necessary to produce more cooling capacity to compensate for this loss.
4. Other forms of cooling loss: In addition to the main forms of cooling loss mentioned above, air separation equipment may also have other forms of cooling loss, such as valve leakage.
