The key to affecting the total refrigeration capacity is the maintenance, installation quality, and operational level of the expander. During the start-up phase, measures such as preventing moisture and carbon dioxide from freezing inside the expander, preventing clogging of the expander filter, and prolonging the operation time of the expander at higher inlet temperatures are all measures to increase the total refrigeration capacity and shorten the start-up phase.
During the start-up operation, attention must be paid to gradually reducing the temperature difference at the hot end of the cold storage or switching heat exchanger; Before accumulating enough liquid, do not rush to start the liquid oxygen pump or deliver oxygen. Limiting the cold loss to the minimum level can allow more cold energy to be used for liquefied gases and shorten the start-up time.
Another issue closely related to "storing cold energy" is the issue of "allocating cold energy". We hope to retain the remaining cooling capacity after offsetting the cooling loss as much as possible in the distillation tower system (including subcoolers and liquefiers) for the purpose of liquefying air. However, if the liquefaction effect of the liquefier and the liquid air subcooler during the liquid accumulation stage is not taken into account during operation, and the liquid nitrogen subcooler is not used to recover cold energy, excessive cold energy will be carried by the backflow gas to the cold storage (or switching heat exchanger), causing the cold storage to be "supercooled" and expanding the temperature difference at the hot end, resulting in increased cold loss. In this case, the inlet and outlet temperatures of the expander will drop very low, the refrigeration capacity will decrease, and the operation will not be safe. At the same time, the liquid level will also be in a state of hovering and not rising. At this point, the expansion should be reduced and the role of the subcooler and liquefier should be fully utilized. Some units introduce the expanded air into the upper tower in advance, causing the temperature of the backflow gas at the cold end of the accumulator to increase and changing the subcooling condition.
