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The electric motor connected to the piston expander of the DEAR air separation unit drives the expander to turn when it is started. Why does the generator output electric energy when it is in normal operation?
2022-01-14

Large size gate valves and pneumatic control valves should be installed vertically to avoid deviation due to the heavy weight of the valve core, which will increase the mechanical wear between the valve core and the bushing and cause leakage; when tightening the compression screw, the valve should be slightly open to avoid damaging the top sealing surface of the valve;However, at the beginning of the handover, it often goes up instead of down. This phenomenon is not caused by the abnormal phenomenon of the accumulator, nor by the wrong connection of the thermometer. It is often caused by the hysteresis of the platinum resistance thermometer. The length of the lag time is also related to the position of the temperature measuring point and the insertion depth of the thermometer rod. If the probe is inserted deeper, the temperature response is more sensitive. On the contrary, the lag time is longer.If the liquid oxygen level of the condensing evaporator is too high and the liquid air level of the lower tower is too low, it may be due to too much liquid air entering the upper tower. At this time, the liquid air throttle valve should be turned down. On the contrary, if the liquid oxygen level of the condensing evaporator is too low and the liquid air level of the lower tower is too high, the liquid air throttle valve should be opened to keep the liquid level of the condensing evaporator stable.
In the condensing evaporator of small DEAR air separation plant, most of the liquid oxygen evaporates between tubes and the gas nitrogen condenses in tubes. The level of liquid oxygen surface reflects the size of heat transfer surface. The liquid oxygen surface is too low and the heat exchange area is insufficient. In order to increase the heat exchange area, it is necessary to make the liquid oxygen surface as high as possible.The better the ability of liquid oxygen to scour the wall of the channel, the more acetylene and other hydrocarbons are not easy to precipitate on the wall, and the carbon dioxide particles are not easy to block the channel section; from the perspective of heat transfer, because the boiling heat transfer coefficient of the liquid oxygen side of the plate fin condensing evaporator is related to the fluid flow, the better the flow is, the greater the heat transfer coefficient is.If the cold end temperature is too low, the air will start to liquefy somewhere in the cold section, and the cold end air temperature will not decrease. At this time, the temperature difference at the cold end will further expand and the temperature in the middle will decrease. The reason for the further expansion of the temperature difference at the cold end is that the temperature of the backflow gas rises continuously when it passes through the cold end, while the temperature of the air is almost unchanged after partial liquefaction.
The cooling of each equipment is carried out in stages, so the cooling is uniform and the thermal stress is small. In addition, in the second cooling stage, the cooling capacity of each equipment in the cooling tower is large, which makes the expander run for a long time at a higher inlet temperature, so as to give play to the large cooling capacity of the turbo expander at high temperature and shorten the start-up time.The purification effect of molecular sieve purification system affects the operation cycle of the device. For the same equipment, improper operation may also affect the purification effect. During the operation, the following problems should be paid attention to: the installation requirements of molecular sieve adsorber: carefully check whether the upper and lower screens are damaged and whether the fixation is firm;When a unit group of switching heat exchanger is cut off due to channel damage, the total heat exchange area of the heat exchanger is reduced, and the capacity of transferring cold energy is also reduced. If the amount of air passing through is constant, the air can not be cooled to the original set temperature, and the temperature difference at the cold end will also expand, which is not conducive to self cleaning, and the resistance will increase rapidly.