In the compressed air system, adsorption dryers are seldom used alone. Usually, two sets of filters are installed before the inlet of the adsorption dryer, and one set of filters is installed after the exhaust port. Almost all pneumatic pipe networks use the dryer in conjunction with the filter.

This is not only to meet the need of gas quality, but also to satisfy the requirement of normal operation of adsorption dryer itself.

What is the purpose of installing filters in an adsorption dryer?

 

1. Water filter.

Its function is to remove the larger liquid water droplets in the compressed air intake.

The adsorbent only adsorbs its state water (water vapor), and the adsorption effect will be weakened or even disappear permanently if the liquid water is contaminated or soaked.

Therefore, the equipment of water filter is very necessary, and its precision is generally selected between 3 and 25 μm.

 

2. Oil filter.

Even if the adsorbent surface is contaminated with a few microns of oil film, it will permanently lose its adsorption activity.

The oil content in the exhaust of general air compressors (oil mist and oil vapor) is usually over several dozen ppm. Even domestically produced oil-free air compressors cannot achieve absolute oil-free exhaust. To prevent the accumulation of trace oil in the adsorption bed, it is crucial to install an oil-removing filter before the dryer's intake.

The oil removal filter may be omitted only when the compressor exhaust is completely oil-free (e.g., in centrifugal compressors).

Generally, the oil content in the air entering the adsorption dryer should be controlled below 0.1 mg/m³, which imposes higher requirements on the precision of the oil-removing filter.

 

3. Dust removal filter.

When the adsorbent is subjected to repeated impact and compression by alternating pressure, a large amount of dust is generated by friction. Although these dust particles are fine, they are extremely hard and can cause blockage, wear, and contamination to downstream pneumatic equipment or workpieces, which must be removed.

The filter precision can be selected from 1 to 5 μm (or according to the process requirements).

If downstream gas-consuming equipment has additional requirements for compressed air quality, other specialized filters such as sterilization filters should be installed at the end of the gas distribution network.