DEAR Air separation equipment.When the temperature of the cold end of the switching heat exchanger reaches - 60 ～ - 150 ℃, the circulation can be used. The function of the circulation is to reduce the temperature difference at the cold end. When passing through the water freezing stage before - 60 ℃, it is easy to ensure the temperature difference of water self-cleaning (between 12 ℃ and 28 ℃), so the circulating current can not be used. In particular, the central cooling method can accelerate the cooling of the cold end of the switched heat exchanger.The range of temperature change is proportional to the temperature difference, so it also reflects the size of the temperature difference. When examining the temperature difference between the hot end and the cold end of a cold accumulator, it is necessary to measure it strictly, instead of using the temperature amplitude to replace the temperature difference. The temperature of the middle part or the middle part of the pump is also changing in a switching cycle, which is usually measured before switching.
DEAR Air separation equipment.There is water in the pipe and it cracks. When the heating is not complete, especially when the small pipe is blocked and the accumulated water can not be blown away, the small pipe may freeze and crack when the water at low temperature freezes into ice and the volume expands. There was a slight local explosion in the main cooler.Usually, the air volume during start-up can reach about 80% of the air volume during normal production by regulating the bypass valve, and the air volume can also be determined as 80% ~ 100% of the sewage nitrogen volume. At the same time, the throttling effect of bypass air can be recycled in the switching heat exchanger.DEAR Air separation equipment.Some air separation processes are different. There is no butterfly valve at the nitrogen outlet of the upper tower. At the same time, the expanded air is only sent to the liquefier without going through the cooler. For such a process, gas can be sent to the upper tower at the beginning of liquid accumulation. Because it can make full use of low temperature gas to cool the upper tower, and the cooling capacity of the gas discharged from the upper tower can be fully recovered in the subcooler and liquefier.
DEAR Air separation equipment.Control the nitrogen water precooler and reduce the temperature of air entering the tower as much as possible. In the air cooling tower, air and water are in direct contact, which can not only exchange heat but also be washed. It can remove the dust in the air and dissolve some corrosive impurity gas, so as to avoid the corrosion of aluminum alloy material of plate fin switching heat exchanger and prolong its service life. Due to the large volume of the air cooling tower, it can also play a buffer role for the processing air, and the air compressor is not easy to overpressure when switching.The cooling capacity is required by the cooling capacity balance of the whole air separation unit. When the cooling capacity is greater than the demand, the liquid level of the condensing evaporator will rise, so the cooling capacity should be reduced accordingly. When the liquid level drops to a suitable height, a little more cooling capacity is needed to make it balanced and stable.
DEAR Air separation equipment.Due to environmental problems, the concentration of N2O in the air is increasing. In addition, the electronic and other industries have higher and higher requirements on the purity of oxygen products (99.99% - 99.9999%), so the removal of N2O in the processing air is more important than in the past. A better method is to find a suitable molecular sieve and remove H2O, CO2, C2H2 and N2O in the process air by CO adsorption in the molecular sieve purifier.Only by increasing the oxygen concentration in the liquid and air and reducing the burden of distillation on the upper tower, can the oxygen yield be increased. It should be noted that liquid nitrogen control valve should be used to regulate the purity of liquid nitrogen, not the liquid nitrogen reflux valve of lower tower. The return valve should be fully open under normal conditions.With the continuous increase of the flow rate of central extraction or circulation, the circulating temperature becomes lower and lower, the cold end of the switching heat exchanger becomes colder and colder, and the temperature in front of the expander still can not be increased. Finally, the adjustment means are lost, resulting in a passive situation. The reasons for this situation are: there is no proper restriction on the flow rate of central suction or circulation before liquid accumulation; the liquefier is connected late, or the liquefying effect of liquefier is poor.