Performance analysis of ventilation and filtration equipment based on the principle of adsorption

I. The principle of adsorption

The activated carbon material in the equipment can do selective adsorption of polluted gases, rather than mechanical operation, because the surface of the activated carbon has a large number of micro-pores, most of which are extremely small pore size, and the surface area of the micro-pores of the unit material we call "specific surface area", the specific surface area can be as high as 700 - 2300m2/g, so the adsorption effect is very good. When adsorption is carried out, we call the harmful gases in the air "adsorbent" and activated carbon "adsorbent". If a chemical reaction occurs during this process, we call it chemisorption, otherwise, it is physical adsorption.

After a long period of use, the adsorption capacity of the activated carbon will continue to weaken and the desorption will continue to increase so that the activated carbon material will become obsolete. Of course, we can also heat or steam fumigation methods to make the adsorption material out of the adsorbent, activated carbon can be regenerated.

II. Performance of adsorption

1. Absorption capacity

The so-called adsorption capacity is specific to a certain gas, and the amount of adsorption capacity per unit of activated carbon is called "adsorption capacity".

2. Retention time

The longer the retention time, the better the adsorption effect. To maintain sufficient retention time, we must keep the carbon layer thick enough and the air speed of filtration must not be too high.

3. Service life

The adsorption efficiency of new activated carbon materials is naturally higher, but in the process of use its efficiency will continue to decay, when the accumulated pollution in the equipment exceeds the permissible range, the filtration equipment will be scrapped.

4. Selectivity

Usually, gases with high molecular weight or boiling point are more easily adsorbed, and volatile organic gases are more easily absorbed than inorganic small molecule gases; chemisorption is more selective than physical adsorption, and this is standard for our choice of equipment.

III. Choice of materials

Nowadays, the main materials used in ventilation filters are granular carbon and fiber carbon. The traditional granular activated carbon includes coal carbon, wood carbon, coconut shell carbon, bone carbon, etc. Sometimes the granular carbon is made into powder and adhered to other porous materials, which are then processed and shaped. The other type of fiber-activated carbon is made from organic fibers containing carbon, which has a small pore size, high adsorption capacity, fast adsorption rate, and quick regeneration. The more common fiber substrates are phenolic, vegetable fibers, polyacrylonitrile, etc.