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. The average temperature difference of air separation plant manufacturers is related to the relative flow direction of cold and hot fluids. The parallel flow of two fluids in the same direction is called "downstream flow"; Parallel reverse flow is called "countercurrent"; Vertical cross flow is called "cross flow". When the properties, flow rate, inlet and outlet temperature and heat exchange area of the cold and hot fluids are the same, the maximum average temperature difference between the cold and hot fluids is found in the counter flow arrangement, followed by the cross flow, and the minimum in the downstream flow.
The water and carbon dioxide in the main heat exchanger are frozen. The temperature difference at the hot end increases obviously, the cooling capacity of the air separation unit is insufficient, and the expansion air volume needs to be increased. Pay special attention to this situation when the moisture and carbon dioxide detection instruments fail. When the heat transfer surface of the condensing evaporator is insufficient, the air separation plant manufacturer must increase the pressure of the lower tower to increase the heat transfer temperature difference to ensure a certain heat load. According to the characteristic curve of the air compressor, with the increase of the exhaust pressure, the air volume will also decrease, which will also reduce the oxygen production. The key to affect the total cooling capacity is the maintenance, installation quality and operation level of the expander. In the start-up stage, to prevent the moisture and carbon dioxide from freezing in the expander, to prevent the expander filter from being blocked, and to extend the operation time of the expander at a higher inlet temperature as far as possible are all measures to increase the total cooling capacity and shorten the start-up stage.
Scale attached to the cooler wall, nitrogen water precooler packing, nozzle or sieve, not only affect the heat transfer, reduce the cooling effect, but also hinder the circulation of cooling water or air, serious equipment failure will be caused, such as nitrogen water precooler with water, so that the accumulator (or heat exchanger) frozen. The scale is hard and hard to remove. Because the heat transfer coefficient increases greatly, it is not necessary to increase the temperature difference by increasing the pressure of the lower tower, and the actual operating pressure of the lower tower also decreases slightly. This is not exactly the same as the heat transfer of long tube condensing evaporator, because the mechanism of boiling heat transfer in tube is different from that in tank. It is safe and reasonable to adopt full immersion operation for plate condensing evaporator.
Krypton and xenon are mainly used in electric light sources. The lamp filled with krypton, xenon and argon mixture has the advantages of small volume, long service life and high efficiency. Generally, the efficiency is 4-5 times higher than that of incandescent lamp, and the service life can be increased by 2-3 times. Krypton and xenon are used in flash lamp and stroboscope. Because the discharge intensity of xenon lamp is higher than that of sunlight, the long arc argon lamp filled with xenon gas, commonly known as "little sun", has strong fog piercing ability, and can be used for lighting in airports, stations, docks and other places, as well as in the battlefield. When the air separation plant manufacturer finds a large amount of water flowing into the air separation tower, the air inlet valve of the air separation plant 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.
