DEAR Air separation plant.For the all low pressure air separation unit which uses freezing method to remove moisture and CO2 from the air, because sufficient backflow gas is needed to carry the frozen moisture and CO2 out of the unit, the pure nitrogen (99.999%) yield is only 1.1 times of the oxygen yield. For the molecular sieve purification air separation process of extracting argon fraction, the yield of pure nitrogen is not subject to the above restrictions.DEAR Air separation plant.The increase of temperature difference at hot end is not necessarily due to the freezing of heat exchanger. Because the opening of cam and throttle-1 valve is not suitable, the distribution of high-pressure air into oxygen, nitrogen and distillate compartment is unreasonable, too much processing air or poor heat exchanger manufacturing will cause the increase of temperature difference at the hot end.In order to reduce the temperature of the process air entering the purifier before the molecular sieve purifier, the nitrogen water precooling system, including air cooling tower and water cooling tower, is usually installed in the low-pressure oxygen generator. In the air cooling tower, the air enters from the bottom, leads out from the top of the tower and enters the molecular sieve purifier.
DEAR Air separation plant.The equipment that transfers heat from hot fluid to cold fluid is called heat exchanger, or heat exchanger. There are many heat exchangers in the air separation plant, including nitrogen water precooler, switching heat exchanger (or cold accumulator), main heat exchanger, condensing evaporator, subcooler, liquefier, gasifier, heater and air compressor cooler.DEAR Air separation plant.The intensity of heat transfer is related to the process of gas nitrogen condensation and liquid oxygen evaporation. Taking the long tube condensing evaporator as an example, the evaporation and boiling state of liquid oxygen in the tube can be roughly divided into three sections from bottom to top: preheating section, boiling section and steam section.DEAR Air separation plant.Low pressure small diameter has threaded flange, high pressure and low pressure large diameter are welded flange, different pressure flange thickness and connecting bolt diameter and quantity are different. According to different levels of pressure, flange gasket also has different materials, from low pressure asbestos gasket, high pressure asbestos gasket to metal gasket.
Contact of cryogenic liquid with skin will cause severe frostbite. Light skin blisters, swelling, pain; heavy will freeze the internal tissue and bone joints. If it falls into the eye, it will cause eye damage. Therefore, when discharging the liquid, avoid direct contact with the liquid by hand, and wear dry cotton gloves and protective glasses when necessary. In case of contact with the skin, should immediately wash with warm water (below 45 ℃).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.Since the gas entering the purifier is saturated air, the purpose of controlling the high-pressure air pressure during heating of small air separation unit is: 1) reducing the moisture of the heated gas into the purifier (or dryer); 2) ensuring the service life of the purifier (or dryer); 3) extending the service life of the adsorbent.
