Air separation plant's purification principle

Purification principle of oxygen plant air separation unit

In the equipment of oxygen production based on the principle of low-temperature distillation, in order to ensure the normal rectification and separation of air in the low-temperature area, the air must be pretreated in the normal temperature area, such as filtration, precooling and purification.

The air contains a lot of dust. During the long-term high-speed operation of the air turbine compressor (hereinafter referred to as the air compressor), the dust will cause the wear, corrosion and scaling of the impeller, blade and other parts inside the machine, and shorten the service life of the machine. Therefore, the raw material air filter must be set to remove the dust in the air.

The temperature of the air compressed by the air turbine compressor rises to more than 80 degrees, resulting in the failure of subsequent adsorption and heat exchange. The air precooling system can effectively reduce the temperature of the air entering the air separation unit.

In addition to a large amount of dust in the raw air, there are also moisture, carbon dioxide, acetylene and other hydrocarbons. Most modern air separation equipment use molecular sieve purification system to remove these impurities, so as to improve the cleanliness of the air entering the cold box and prevent the concentration of moisture and carbon dioxide from threatening the normal operation of the air separation equipment. Therefore, gas filtration, precooling and purification equipment is an indispensable part of air separation equipment.

Dust removal mechanism of air separation unit

There are five dedusting mechanisms:

1. Inertial impact: smaller particles can pass through the micropores of the filter element, but the path through the filter medium is tortuous. The particles have enough mass and momentum to collide with the filter element fiber and be blocked and captured.

2. Brownian diffusion: very small particles have very small mass. When diffusing with the air flow in Brownian motion, they collide with the filter fiber and are filtered out.

3. Direct blocking: when the dust particles larger than 1 micron pass through the micropores of the filter medium material, they are directly blocked and intercepted because the particle diameter is larger than the micropore diameter, so as to achieve the purpose of removing impurities.

4. Gravity sedimentation: the dust particles are continuously collected until their mass becomes large enough. Under the action of gravity, they fall to the bottom of the filter or are discharged by the ash discharge valve.

5. Electrostatic sedimentation: static electricity changes the movement track of dust and collides with obstacles, and electrostatic force participates in the sticking work.