DEAR Liquid air separation unit.The cooling water with increased temperature is led out from the lower part and sent to the water cooling tower or discharged (for open system). The cooled air is discharged from the top of the tower and sent to the air separation tower or molecular sieve adsorber. The disadvantage of packed tower is that the packing is easy to be blocked by scale, and the packing forms into large pieces, which is difficult to clean and replace.The most likely leakage place of the switching heat exchanger is the weld, especially the joint between the head and the pipe. The causes of leakage are mostly manufacturing and installation quality problems, and also related to maintenance. The working condition of the switching heat exchanger is poor. It is not only impacted by the alternating air flow, but also the air temperature changes greatly. In the long-term operation, the weak part is easy to leak.DEAR Liquid air separation unit.How to recover and transfer the cold capacity of the expansion air to the tower, whether it is transferred to the lower tower by the liquefier first, and then supplied to the upper tower, or directly transferred to the upper tower by the subcooler, is OK. If the cold fluid channel of the liquid air subcooler can be directly connected with the channel behind the expander (for example, the subcooler and the liquefier are integrated). In other words, the liquid air subcooler can be used to recover part of the cooling capacity of the expansion gas and directly supply it to the upper tower, and the subcooler can also act as a liquefier.
DEAR Liquid air separation unit.The liquid oxygen absorbs the latent heat of condensation released by the gas nitrogen with higher temperature and evaporates. So it is called "condensing evaporator". Condensing evaporator is an important heat exchange equipment in distillation system. Its working quality is related to the power consumption and normal production of the whole air separation unit. Therefore, it is necessary to correctly operate and maintain the condensing evaporator.Mixed type: its characteristic is that the heat exchange of cold and hot fluids is realized in the process of direct mixing. In the process of heat transfer, there is also material exchange, such as nitrogen water precooler.The causes of automatic valve failure are: the valve is frozen by water and carbon dioxide, or stuck by other debris. If there is a small amount of impurities on the sealing surface, the valve will not be closed tightly. The fixing bolts of automatic valve seat are not tightened evenly, and air leaks from the gap of gasket, sometimes the gasket will be damaged, and the more leakage, the greater.
In order to reduce the temperature of the process air entering the purifier before the molecular sieve purifier, the nitrogen water precooling system, including air cooling tower and water cooling tower, is usually installed in the low-pressure oxygen generator. In the air cooling tower, the air enters from the bottom, leads out from the top of the tower and enters the molecular sieve purifier.DEAR Liquid air separation unit.For the medium pressure process air separation unit, the high pressure air is divided into two channels after passing through the first heat exchanger: one is cooled continuously through the second heat exchanger, and then throttled to enter the lower tower; the other is expanded by the expander, and then enters the lower tower. The expansion amount has no direct relationship with the oxygen extraction rate.DEAR Liquid air separation unit.In order to balance the cooling capacity, it is necessary to increase the pressure of high-pressure air, which will increase the energy consumption of the device. Therefore, the inlet air temperature of medium pressure process expander should be kept within the range of process specification requirements, and should not be increased at will.
