The refrigeration capacity of the air separation unit mainly depends on the expander, but the lowest temperature of the air separation unit is at the top of the upper tower, which is about - 193 ℃, lower than the outlet temperature of the expander (- 180 ℃).DEAR Cryogenic air separation unit.When the scale is serious, it must be removed. The cleaning methods are usually mechanical or acid washing. The mechanical method is to brush off the scale with an iron brush; the pickling method is to use the dilute solution containing 10% hydrochloric acid to clean with a small water pump, dissolve and remove the scale with acid (because the scale is generally alkaline), and then neutralize it with alkali. It should be noted that the acid should not be too thick to avoid corrosion of metal.Neon and helium occupy part of the condenser, so the heat exchange area can not be fully utilized. The more neon and helium are accumulated, for example, about 6m3 of neon and helium are accumulated at the top of the main cooling system of 6000m3 / h oxygen generator in 8h. So many non condensable gases will seriously affect the normal operation of the condensing evaporator.
DEAR Cryogenic air separation unit.Helium is very inert. When smelting special rare metals such as titanium, zirconium and semiconductors such as silicon and germanium, helium should be used as protective gas. The welding and cutting of high melting point and thick alloy also need helium protection. Helium has strong diffusivity and permeability. Therefore, helium is the best leak indicator for pressure vessels and vacuum systems with strict requirements.Increasing the number of plates in the lower column can improve the purity of liquid nitrogen; increasing the number of plates in the distillation section can improve the purity of nitrogen, reduce the amount of argon carried away by nitrogen, and increase the extraction rate of argon. Increasing the number of plates from the fraction to the main cooler is beneficial to the separation of argon and oxygen, which can increase the argon content in the argon fraction and reduce the argon content in the liquid oxygen.On the one hand, it increases the saturated water content when the air leaves the spray tower; on the other hand, it decreases the adsorption capacity of molecular sieve; when the spray tower is cut off or the water level is too high, the temperature of molecular sieve adsorber will rise or water carrying accident will occur.
At the critical temperature and pressure, there is no obvious difference between the gas state and the liquid state; when the critical pressure is exceeded, when the temperature drops below the critical temperature, all of them become liquid, and there is no phase transition stage and latent heat of phase transition. On the contrary, the gasification process is the same.DEAR Cryogenic air separation unit.There are many kinds and types of low temperature valves. Taking the low temperature stop valve as an example, the failure occurred on the top of the valve. The valve top (valve head) of the valve is movably connected with the valve stem, so that the two sealing surfaces can be "automatically aligned" when the valve is closed. After long-term use, sometimes the locking nut is loose due to the damage of anti retreat gasket, and finally the valve top falls off when opening the valve.In this case, in order to close the valve, we often use a lot of strength, but the result is that the crush is aggravated. Sometimes the valve stem center line is not perpendicular to the valve seat sealing surface (valve surface), or the valve top and valve surface are worn due to long-term use, which will cause valve leakage.
