Large air separation FAQ

What's the reason for using two-stage distillation column in air separation column?

Sieve tray column

Superheated steam

The air separation cold box is filled with insulation material, generally pearlite, and the pearlite particles are filled with air. After the operation of the air separation unit, the temperature of the insulation material and the air will decrease, and the volume will decrease. At this time, if the cold box is well sealed, negative pressure will be formed in the cold box, and the cold box may be compressed under the effect of internal and external pressure difference. If the cold box is not well sealed, the moisture outside the cold box will enter the cold box, making the insulation material damp, and the cold loss of the unit will be greatly increased. In order to prevent the cold box from being compressed and the thermal insulation material from becoming damp, dry nitrogen or crude nitrogen is usually filled into the cold box after the unit is running to keep the cold box at slightly positive pressure.

Pressure test before valve installation 1. In the warranty period, those with the certification and the sealing surface is intact can no longer conduct the strength test alone, but only the air tightness test can be taken before installation. 2. Within the warranty period, it has the certificate, and its sealing surface has defects such as corrosion and damage. After treatment, it must carry out the air tightness test. 3. Outside the warranty period, those with certification and intact sealing surface shall be subject to air tightness test before installation. 4. For valves that need to be degreased and disassembled on site, air tightness test shall be conducted separately before installation. 5. The safety valve shall be sent to the local quality inspection department of the project for verification before the end of installation and commissioning.

The most important index of radiographic quality is the sensitivity of radiography, which is the size of the smallest defect along the direction of ray penetration that can be found on the negative plate quantitatively. Natural defects’ size are hard to be sure. It is obvious that it is unrealistic to use natural defects to evaluate the sensitivity of radiography. Therefore, in order to facilitate the evaluation of photographic quality, it is often used to monitor the image quali...

Before the air cooling columnand water cooling columnare hoisted in place, the anchor hole shall be cleaned, and there shall be no water and debris in the anchor hole.   After the air cooling columnand water cooling columnare hoisted in place, the perpendicularity of the equipment shall be checked. The perpendicularity shall be ≤ 1/1000 and the total length shall not exceed 10mm.   The bottom of the anchor bolt shall not touch the bottom of the reserved anchor hole. Af...

1. Before filling with pearlite, the water accumulated on the foundation surface of air separation unit must be removed, dried with hot air, and all manholes shall be closed. 2. When filling pearlite, all containers and pipes in the cold box should be inflated and kept at 50kPa pressure, then slightly open the valve of each meter pipeline, and all thermometers should be electrified to check whether the thermometer cable is damaged during the filling process. 3. The filled pearlite shall not be mixed with combustibles. 4. When filling with pearlite, coarse mesh or pearlite pouring device should be set at the manhole on the top of the cold box to prevent whole bag pearlite from entering the cold box. 5. After the pearlite is filled, the manhole shall be sealed.

In the upper column fractionation, below the liquid air inlet is called the stripping section, and above the liquid air inlet is called the distillation section. The stripping section realizes the separation of oxygen and argon, and the distillation section realizes the separation of oxygen and nitrogen. Because the boiling points of oxygen and argon are relatively close, the separation is difficult. In order to ensure the purity of oxygen, the separation of oxygen in the distillation section is not clean, and argon escapes with oxygen and nitrogen. If high purity nitrogen is to be obtained, argon will condense with oxygen in the distillation section, which will affect the purity of oxygen. In order to ensure the purity of oxygen and obtain high purity nitrogen, it is necessary to extract part of the gas with high argon concentration in the distillation section.

Fluid resistance refers to the pressure drop of fluid flowing through pipes, valves or equipment. The actual process pressure gradually decreased. In order to ensure the final pressure required by the process, a pressure source (gas compressor or pump) is needed to provide higher pressure, that is, more energy is consumed. Therefore, the amount of resistance reflects the amount of energy loss. In oxygen production, flow resistance is also closely related to the production process. For example, the resistance measurement of switching heat exchanger is the basis to judge whether self-cleaning is good. If the resistance of the distillation column is too large, the normal distillation conditions will be destroyed. The magnitude of resistance (i.e. energy loss) can be expressed by the pressure drop before and after the fluid flows through the vessel. For example, the gauge pressure at the bottom of the tower is 0.038 MPa, the gauge pressure at the top of the tower is 0.025 MPa, and the p

In the process of operation, especially in the start-up and shutdown of the air separation unit, one-way force should be avoided on the instrument. During the start-up of the equipment, close the high pressure and low pressure valves firstly, then open the balance valve, and then slowly open the high pressure (or low pressure) valve, so that the measured medium can enter the positive (negative) pressure chamber of the transmitter. If the liquid is to be measured, the gas in the positive (negative) pressure chamber should be discharged from the upper vent. If the gas is measured, drain the liquid accumulated in the positive (negative) pressure chamber from the lower drain screw hole. After discharging the gas (liquid), close the balance valve, and then open the valve on the other side. When the equipment is shut down, the high pressure (or low pressure) valve should be closed first, then the balance valve should be opened, and then the valve should be closed on the other side. Someti

When the amount of treated air increases, the rising steam in the distillation column will increase, and the amount of liquid to be condensed in the main cooler will increase accordingly, so it has no effect on the reflux ratio in the column. The purity of oxygen and nitrogen remained unchanged in a certain range with the increase of gas volume, and the output increased proportionally with the increase of gas volume. However, with the increase of the amount of condensate in the main cooler, the heat load of the main cooler increases. When the heat transfer area is insufficient, the temperature difference of the main cooler will inevitably expand, and the pressure of the lower column will increase accordingly. At the same time, with the increase of gas velocity in the column, the amount of downflow liquid increases, and the liquid layer on the tray thickens, which increases the resistance of the tray and the pressure of the upper and lower columns. This will adversely affect the sepa