The quality of the liquefier can be judged by the difference between the temperature after the expander and the temperature of the waste nitrogen out of the liquefier. If the temperature rise is large, it means that the working condition is good; if the temperature rise is not obvious, the liquefier may be blocked and not play a role in liquefaction.DEAR Cryogenic air separation unit.Its temperature can be lower than that of the cooled medium (chilled water, etc.), so it can absorb heat Q2 from the cooled medium in evaporator 4, and the refrigerant will evaporate into low-pressure steam and return to the compressor for circulation. Therefore, compared with the refrigeration in the oxygen generator, the common point of the refrigeration in the refrigerator is that the compressor needs to consume work.DEAR Cryogenic air separation unit.The purpose of throttling is to obtain low temperature, so the greater the effect of throttling temperature drop, the better. Pressure difference before and after throttling. The greater the pressure difference before and after throttling, the greater the temperature drop. To increase the pressure before throttling, we must increase the discharge pressure of the compressor, and correspondingly increase the energy consumption of the compressor, which is not what we want.
DEAR Cryogenic air separation unit.If the heat exchange effect of the air compressor end cooler (or nitrogen water precooler) is not good, or the cooling water temperature is high, the air temperature into the device will rise. If the air volume remains unchanged, the cooling capacity required to cool the air to near the liquefaction temperature will increase accordingly.DEAR Cryogenic air separation unit.When the temperature of the air entering the unit increases, not only the heat load of the accumulator (or switching heat exchanger) increases, but also the amount of water brought in increases, which increases the burden of self cleaning. With the increase of water freezing, the heat transfer efficiency is reduced. When the heat transfer area of the heat exchanger is fixed, the increase of the heat load and the poor heat transfer effect will inevitably lead to the increase of the temperature difference between the cold end and the hot end.DEAR Cryogenic air separation unit.The key to affect the total cooling capacity is the maintenance, installation quality and operation level of the expander. In the start-up stage, to prevent the moisture and carbon dioxide from freezing in the expander, to prevent the expander filter from being blocked, and to extend the operation time of the expander at a higher inlet temperature as far as possible are all measures to increase the total cooling capacity and shorten the start-up stage.
DEAR Cryogenic air separation unit.Damp insulation material will greatly reduce the thermal insulation performance and increase the loss of cooling. If the cold insulation box is not sealed tightly, after the internal temperature of the cold insulation box decreases, the external wet air will invade, and the internal condensation or even freezing may occur. Therefore, it is necessary to ensure the sealing of the cold box, and fill a small amount of dry gas to maintain micro positive pressure.DEAR Cryogenic air separation unit.The structure of water cooling tower for large air separation plant in China is as follows: packed tower. In the early stage, it was equipped with ceramic lacigo ring, which had good heat transfer effect and little resistance. However, when it is used in the self cleaning low-pressure process, because the switching system is switched every few minutes, the air flow has a great impact on the porcelain ring during the switching venting, which is easy to cause the porcelain ring damage and increase the resistance. There are also plastic rings to increase strength.
