Compared with switching purification process, the air separation unit of molecular sieve purification process has simple start-up operation and easy control because the air is adsorbed by molecular sieve to remove impurities such as water and carbon dioxide. It does not need to consider the complex effects such as the self removal of water and carbon dioxide, the precipitation of water and carbon dioxide in the expander and so on. The attention of the start-up process is mainly focused on giving full play to the refrigeration capacity of the expander, reasonably distributing the cooling capacity, and comprehensively cooling the equipment.When there is liquid in the storage tank, it is strictly forbidden to use hot work for repair; the thawing of equipment pipeline should be heated slowly, and do not use overheated working medium or open fire to thaw; protective gloves should be worn when contacting low-temperature liquid to avoid direct contact between skin and low-temperature liquid; the transportation process should be stable, and there should be no big bumps.
In the process of putting the crude argon column into operation, firstly, the argon fraction is extracted to pre cool the crude argon column, and then the liquid air is gradually sent to the crude argon condenser. With the cooling of the crude argon column, the distillation condition of the crude argon column is gradually established. The sign is that the resistance of crude argon tower, the purity of crude argon and the extraction amount of argon fraction continue to increase until the normal index is reached. At the beginning, the main cooling liquid level may drop slightly, and with the establishment of crude argon column distillation, the main cooling liquid level will recover.DEAR Liquid air separation unit.The method is to observe the regularity of escaping gas. It is mainly used to judge the leakage of the switching channel of the switching heat exchanger. For the alternately used containers, the leakage position can be further determined by switching use.DEAR Liquid air separation unit.The unit cooling loss decreases with the increase of unit capacity, while the temperature difference at the hot end of large air separation units is generally about 3 ℃, and the unit incomplete heat exchange loss of different units has little change. Therefore, with the increase of unit capacity, the proportion of unit heat exchange incomplete loss in total cooling loss increases.
DEAR Liquid air separation unit.Before heating the device, the air cooling tower and water cooling tower should be separated from the device with blind plates; the oxygen content in the air cooling tower and water cooling tower should be analyzed. Only when the oxygen content is between 19% and 21%, can the maintenance personnel be allowed to enter; if they work in the area with oxygen content lower than 19%, they must be supervised by someone and wear isolation masks (oxygen respirator, long tube mask, etc.).DEAR Liquid air separation unit.For small non switching plate fin heat exchanger, the gas distribution valves of oxygen, nitrogen and fraction (or waste nitrogen) are not set on the air side. The influence of the quantity of oxygen and nitrogen products on the temperature of the air outlet adjacent to the cold end is not considered, so it is self balanced. Under the steady condition, the temperature of the air at the cold end is almost constant.DEAR Liquid air separation unit.When the gas volume decreases, the vapor flow rate decreases, the liquid volume on the tray decreases, and the liquid layer thins, so the tray resistance decreases. At the same time, due to the reduction of the main cooling heat load, the heat transfer area is abundant, and the heat transfer temperature difference can also be reduced. These effects will help to reduce the pressure of the upper tower and the lower tower.
DEAR Liquid air separation unit.When a large amount of water is found flowing into the air separation tower, the air inlet valve of the air separation unit and the water supply valve of the air cooling tower should be closed while the air compressor is venting. The inlet water of the switching heat exchanger with the cold end at the top and the hot end at the bottom is easy to remove the fault, and it is not easy to cause serious freezing phenomenon. However, the accumulator with the hot end at the top and the cold end at the bottom is very afraid of water inflow. Once the water inflow is easy to cause freezing blockage, the only way is to stop heating and thawing.DEAR Liquid air separation unit.The pipe is filled with both air and backflow gas, so the temperature of hot blowing period (filled with air) and cold blowing period (filled with backflow gas) can be measured. The cold end temperature is measured at the bottom of the accumulator with a resistance thermometer. The following describes how to measure the temperature condition of the accumulator and calculate the temperature difference between the hot end and the cold end with some measured data.
