Liquid air and liquid nitrogen supercooler uses nitrogen as cold source to cool liquid air or liquid nitrogen. There are Pipe type and plate type cooling device. When leakage occurs, it will affect the normal operation of the distillation column. It can be divided into two situations:
1) liquid air and liquid nitrogen leak to the nitrogen side. Since the liquid air leaks to the nitrogen side, it will be further recovered in the heat exchanger, so the increase of cold loss is not obvious, but the temperature at the cold end is Ding. Will drop, the cold end is too cold. If it is liquid leakage, because of the low concentration of nitrogen in liquid, the leak into the gas nitrogen will make the purity of gas nitrogen decline. After the leakage of liquid, the amount of liquid going into the tower will decrease and the recirculation fluid will decrease, which will worsen the rectifying working condition and decrease the oxygen output. In severe cases, the distillation tower will not work normally.
2) outside the gas and nitrogen leak. This usually happens at the weld joint or flange of the connection pipe. When the gas and nitrogen leak out, the amount of gas and nitrogen entering the heat exchanger will decrease, the supercooling degree of the liquid will decrease, and the gas rate will increase after throttling. At the same time, because this part of nitrogen which has not been reheated is leaked out through the heat insulating material, the production of gas and nitrogen will decrease, the cold loss will increase, the shell will Frost, and the liquid oxygen level of the condensing evaporator will decrease. In order to further judge whether the liquid air and liquid nitrogen supercooler leak or not, the distillation column should be stopped for heating. Separate the medium-voltage system from the low-voltage system, try to avoid air leakage, and then test the pressure of the medium-voltage system and the low-voltage system respectively. If the medium pressure system rises to the working pressure, the low pressure system has gas or the low pressure system rises to the working pressure, when the medium pressure system has gas, in the case of excluding condensation evaporator, liquid throttle valve, liquid nitrogen throttle valve and other middle and low pressure connection valve without leakage, it can be further confirmed that the leakage of liquid air and liquid nitrogen supercooler. At this time, the Pearl sand should be removed and dismantled.
