Large air separation FAQ

In the air separation unit, the function of air cooling column is to reduce the temperature of air compressed by air compressor. Air cooling column is a kind of hybrid heat exchange equipment. In order to increase the heat transfer area, make the cooling water fully contact with the air and mix completely to enhance the heat transfer effect, the air cooling column usually adopts several structural forms such as packed column, sieve plate column or hollow spray column.

In the air separation unit, the water cooling column is a hybrid heat exchange equipment which uses the crude nitrogen to reduce the temperature of the cooling water from the air cooling column after cooling air, so as to provide the air cooling column with recycling. In the water cooling column, the crude nitrogen from the reversible heat exchanger (or accumulator) is 27-28 ℃ and the relative humidity is about 30%, while the temperature of the cooling water from the air cooling column is 35-45 ℃. When the crude nitrogen meets the hot water sprayed, it absorbs heat, thus reducing the water temperature. Generally, the structure of water cooling column is packed column, cyclone plate column and sieve plate column.

The leakage of unit or pipeline in the cold box needs removal of perlite treatment. Since it is uncertain whether there is a leakage point in the cold box, it will have a certain impact on removal of perlite. No matter whether the leakage is liquid or air, the sand filling holes at the top should be opened first, so that the residual gas in the cold box can be slowly discharged into the atmosphere. The oxygen content of the gas in the cold box and the pressure indication in the cold box should be strictly monitored in removal of perlite process. In the process of sand stripping, it is particularly important to avoid the formation of sand free area in the middle of the cold box, so as to avoid sand storm caused by the sudden drop of pearlite sand.

According to the dye composition of penetrant, it can be divided into fluorescent penetrant testing, dye penetrant testing and fluorescent dye penetrant testing, which are represented by I, II and Ш respectively. According to the penetrant removal method, it can be divided into water washing type penetrant testing, lipophilic post emulsifying penetrant testing, solvent removing penetrant testing and hydrophilic post emulsifying penetrant testing, which are represented by A, B, C and D respectively; according to the type of imaging agent, it is divided into dry type Powder imaging agent, water soluble imaging agent, water suspension imaging agent, solvent suspension imaging agent and self imaging were expressed as a, b, c, d, e, respectively. II Cd means solvent removal dye penetrant testing, and the imaging agent is solvent suspension type.

There must be enough smooth straight pipe sections before and after the flow orifice plate. The distance is 10 times of pipe diameter in front of the orifice plate and 5 times of the pipe diameter behind the orifice plate, and no factors affecting the measurement accuracy (such as pipe joint, etc.) are allowed. The inner surface of the pipe weld should also be ground smooth, and the gasket should not extend into the inner diameter of the pipe. And carefully check the installation direction of the orifice plate, do not install it in reverse. (judgment method: the small exit is the entrance, and the large exit is the outlet)

After a long-term operation of the air separation plant, the components in the cryogenic equipment and pipelines in the distillation system will be blocked due to ice or mechanical powder, which will increase the resistance of the fractionator. When the air separation plant has been in normal operation for about 2 years, the fractionator system should be heated and thawed to remove these deposits. When the molecular sieve adsorber and the main heat exchanger have water inflow or other faults, it is also necessary to stop and heat up. In general, the following methods will be used for heating and thawing.

After a long-term operation of the air separation plant, the components in the low-temperature equipment and pipelines of the distillation system will be blocked due to the internal precipitation of icing or mechanical powder, which will increase the resistance of the fractionating column. Therefore, after the normal operation of the air separation plant for about 2 years, the fractionating column system should be heated and thawed to remove these sediments. When the molecular sieve adsorber and the main heat exchanger have water or other faults, they must also be stopped for heating. The following describes several heating and thawing operation methods: