When the full low-pressure oxygen concentrator is started, the cooling of the main cooling system requires a certain amount of cooling, and the cooling required to cool it to the operating temperature is also certain. Some people believe that using gas pre cooling for the main cooling in the second stage and liquid air pre cooling in the fourth stage both transfer a portion of the cooling capacity to the main cooling, and the effect should be the same. Therefore, the pre cooling work for the main cooling is ignored, resulting in the switching heat exchanger being overcooled in the liquid accumulation stage. What is the reason for this?
This is because during the liquid accumulation stage, the temperature condition of the switching heat exchanger has become normal. In addition to compensating for cold losses, the cooling capacity of the expander should be transferred to the tower for liquid accumulation. Its cooling capacity recovery is mainly carried out by the liquefier. The liquefied air recovers the cooling capacity. This part of the liquid enters the upper tower and vaporizes completely due to the high temperature of the main cooling system. Although a portion of the cooling capacity is also transferred to the upper tower, the evaporated steam leaves the upper tower and passes through the liquefier. The temperature rise of low-temperature gas in the liquefier is limited, so the liquid air volume it can generate in the liquefier is less than 10% of the original, Only a small amount of cooling capacity is transferred to the tower through the liquefaction device, and the remaining majority of cooling capacity will be transferred to the switching heat exchanger, resulting in supercooling of the switching heat exchanger, a decrease in temperature in the middle, and an increase in temperature difference at the hot end.
It can be seen that the effect of cooling capacity distribution is different between pre cooling the main cooling system and relying on liquid air for cooling. In the liquid accumulation stage where more cooling capacity needs to be transferred to the tower, liquid should not be used to cool the main cooling equipment to prevent the cooling capacity from returning from the tower to the switching heat exchanger.
