DEAR Air separation unit.The water injection hole of the chilled water distributor is blocked, which causes the water level in the chilled water return tank to overflow to the orifice of the riser, and part of the water is carried into the purifier by air; too much spray water or poor separation effect of the water separation device (including the water capture layer on the top of the tower or the separate water separator) will also cause water entrainment;In the case of slight water inflow and slight freezing, it can be treated without stopping. For example, shorten the switching time, increase the backflow ratio (the ratio of backflow gas to positive flow gas), or stop for a short time to carry out back blowing (low temperature or normal temperature dry gas is introduced from the heating inlet pipe of the sewage nitrogen pipe at the cold end and discharged from the hot end).DEAR Air separation unit.In order to maintain the stability of the working condition, the cooling capacity produced must first make up for the two cooling losses of running off and incomplete heat exchange. When the device has a small amount of low temperature leakage or other cold loss, the required cooling capacity increases. In addition, when part of the liquid products produced by the device are exported to the device, the cooling capacity Q0 brought by the low-temperature products also needs to produce more cooling capacity to make up.
DEAR Air separation unit.The liquid oxygen surface of condensing evaporator is required to be kept at a certain height (data provided by the design and manufacturing unit) to strengthen heat exchange and ensure operation safety. The heat transfer process of condensing evaporator is the process of condensing gas nitrogen to release latent heat and transfer heat to liquid oxygen to vaporize it into gas oxygen.The liquid air subcooler is blocked and the liquid air quantity is reduced, which makes the temperature of sewage nitrogen low and causes the air liquefaction at the cold end of the switching heat exchanger. When several expanders are running at the same time during the liquid accumulation stage of the start-up process, the cold capacity of the expander is too large, and the liquefier can not be fully recovered, the cold end of the accumulator (or switching heat exchanger) may also have air liquefaction.At the same time, the condensing evaporator also acts as a liquefier in the later stage of start-up. After expansion, the low-temperature air entering the upper tower cools the low-temperature pressure gas from the lower tower in the condensing evaporator, some of which condenses and then throttles to the upper tower to further reduce the temperature and become part of the low-temperature and low-pressure reflux gas, so that the accumulated liquid volume increases gradually.
If the heat transfer surface of the condensing evaporator is insufficient, its heat load will be reduced, that is, the heat transfer will be reduced. Therefore, the evaporation of liquid oxygen will be reduced, and the condensation of gas nitrogen will be reduced accordingly. This will directly affect the distillation conditions of the upper and lower columns. At the same time, the air intake of the lower tower will be reduced, the air can not be fed, and the oxygen production will be reduced.DEAR Air separation unit.The change of the middle temperature is the result of many factors, and after taking measures to adjust it, it will change other related working conditions. Therefore, the adjustment of the middle temperature of the cold accumulator (or switching heat exchanger) should have an overall concept to prevent isolated and one-sided views. We should make a comprehensive analysis of the influencing factors, grasp the main contradictions and take effective measures.The incomplete cooling loss of heat exchange is caused by the backflow low temperature gas can not be reheated to the temperature of the positive flow air entering the heat exchanger when it comes out of the hot end of the main heat exchanger. Therefore, the larger the temperature difference between the hot end of the reflux gas and the positive air heat exchanger, the less reheating, the more unused cooling capacity, and the greater the incomplete cooling loss of heat exchange. Therefore, Q2 is directly proportional to the temperature difference at the hot end.
