In the production of rare gases krypton and xenon, with the concentration of krypton and xenon, N2O is also concentrated. The content of N2O can reach 100 × 10-6 ~ 150 × 10-6. N2O itself does not burn, but can decompose. This will affect the removal of CH4 from crude krypton and xenon and the adsorption of water and carbon dioxide by molecular sieve.The upper tower itself can not produce liquid, it mainly depends on the liquid from the lower tower into the upper tower. In the liquid accumulation stage, in order to accumulate liquid level as soon as possible, the cooling capacity should be transferred to the tower as much as possible, and the phenomenon of supercooling, expansion of temperature difference at hot end and increase of cooling loss caused by excess cooling capacity of switching heat exchanger should be avoided.Membrane air separation method: it uses the permeation selectivity of some organic polymer membranes. When air passes through the membrane (0.1 μ m) or hollow fiber membrane, the speed of oxygen passing through the membrane is about 4-5 times that of nitrogen, so as to realize the separation of oxygen and nitrogen. The oxygen enrichment concentration of this method is generally suitable for 28% - 35%, and the scale is only suitable for medium and small scale.
If the molecular sieve bed is uneven and the thickness of the bed through which the airflow passes is different, the maximum temperature will not be reached at the same time at the outlet. Several peaks may appear after mixing, or the whole peak may be relatively flat, the peak temperature will decrease, and the shape of the cold blowing curve will also become "short and fat". In this case, heating and cold blowing to the specified temperature often takes longer.In order to cool the equipment and accumulate liquid as soon as possible in the start-up stage, the refrigeration capacity of the air separation unit which produces gaseous products is much larger than that of the normal production. For example, for small medium pressure air separation units, the refrigerating capacity can be increased by increasing the air pressure; for low pressure air separation units, the refrigerating capacity can be increased by increasing the expansion capacity.DEAR Air separation plant.When installing, pay attention to put the gasket in the right place, especially the pure aluminum gasket should be complete. Tighten the compression nut symmetrically and evenly. If the automatic valve is stuck during operation, it should be removed and soaked in liquid nitrogen for 15min to check the flexibility of the automatic valve. Pick out the stuck valve and properly increase the clearance between the valve stem and the valve seat hole.
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.The removal amount of waste nitrogen (or distillate) is too large, the opening of liquid air and liquid nitrogen control valves is improper, and the working condition of lower tower is not adjusted properly. Poor heat exchange of main cooling system. Insufficient heat exchange surface of the main cooler or more non condensable gas on the nitrogen side affect the heat transfer of the main cooler and reduce the evaporation of liquid oxygen.
Air pressure test on site is mainly to check the air tightness of the equipment. Attention should be paid to the following problems during pressure test: it is strictly forbidden to use oxygen as the pressure test gas source; clean and oil-free pressure test gas source should be used for the oil-free equipment which is no longer degreased after pressure test; the pressure gauge used for pressure test should be calibrated and lead sealed before use.The oxygen content of liquid oxygen and liquid air in the air separation unit is high, which will cause the oxygen concentration to increase in local range after evaporation in the air. If there is a fire, there is a risk of combustion and explosion. A large amount of liquid oxygen was discharged into the trench in a chemical fertilizer plant, and the electric welding spark caused an explosion injury accident. Therefore, it is strictly forbidden to discharge the liquid into the trench at will, and it should be discharged into the liquid evaporation tank or special low temperature resistant metal discharge pit through pipeline.
