DEAR Air separation equipment.The temperature in the lower tower is the saturation temperature corresponding to the lower tower pressure; after throttling to the upper tower, the temperature drops to the saturation temperature corresponding to the upper tower pressure, and some liquid gasifies. The temperature of tap water is far lower than the saturation temperature corresponding to the water pressure, because the saturation temperature of water at atmospheric pressure is 100 ℃, so the general water is in the supercooled state lower than the saturation temperature. For pressure water, the minimum pressure after throttling is atmospheric pressure, and it is still impossible to reach saturation state, so it is impossible to produce gasification phenomenon, and the temperature will not decrease.For the low pressure air separation unit, the air pressure is close to the lower tower pressure and can not be increased at will. The air pressure of the medium pressure air separation unit is much higher than that of the lower tower, which is expanded by throttle valve and expander respectively before entering the lower tower. Since the working pressure does not affect the distillation condition, it can be determined according to the need of cooling capacity.
DEAR Air separation equipment.The adsorption method makes use of the selective adsorption characteristics of adsorbents (such as molecular sieve, activated carbon, etc.) to separate or further purify the noble gas components. For example, the purification of crude neon, neon, helium, krypton and xenon can all adopt this method.DEAR Air separation equipment.Before shutdown or opening, the operating pressure of the whole oxygen pipe network shall be regulated by oxygen compressor to 1.8MPa (the minimum allowable operating pressure). Try to reduce the pressure difference between the front and back of the oxygen valve, and reduce the discharge volume of the shutdown pipeline or spherical tank;DEAR Air separation equipment.Stop pressure test can be carried out only after external leakage is eliminated. After the heat exchanger is raised to the maximum working pressure and stopped for 1 hour, it is qualified if the pressure does not drop obviously. Pressure test of lower tower system. Close the liquid nitrogen throttle valve, liquid air throttle valve and liquid air to argon tower valve.
For an all low pressure air separation unit, increasing or decreasing the refrigerating capacity mainly depends on increasing or decreasing the expansion capacity of the expander (or changing the pressure and speed in front of the expander). When the liquid level of condensing evaporator is too high or too low, it is necessary to check whether other liquid levels are suitable.When the air passes through the throttle valve, the total enthalpy remains unchanged and the temperature and pressure decrease. As for whether liquid is produced before and after throttling, it depends on the state before throttling and the pressure after throttling. It can be seen from the thermodynamic properties of air that there is a saturation curve as the boundary of state.DEAR Air separation equipment.After the air compressor stopped automatically, the pressure in the air cooling tower decreased, and when the air compressor was started again, the molecular sieve purifier water inflow accident occurred. The reason is that the automatic regulating valve of water level and the check valve of backwater system are out of order. When the air compressor stops automatically, the check valve from the air inlet of the air cooling tower to the outlet of the air compressor is full of water, and the air compressor starts again.
When the purity of liquid oxygen is constant, the evaporation temperature increases with the increase of pressure. For example, when the purity of liquid oxygen is 99.55%, if the absolute pressure increases from 0.14MPa to 0.15Mpa, the evaporation temperature will increase from 93.5k to 94.25k. For the condensation process of gas nitrogen, when the pressure is constant, the purity of gas nitrogen increases, and the condensation temperature decreases.DEAR Air separation equipment.The middle temperature difference between the control units is generally not greater than 3 ~ 5 ℃; the middle temperature should not be too low, and the cooling capacity should not be too much concentrated in the main heat exchanger, resulting in the increase of the temperature difference at the hot end. When the temperature of the cold end reaches the air liquefaction temperature, the cooling capacity should be transferred to the distillation system to make the distillation system cool enough, accumulate liquid as soon as possible and establish the distillation system.
