Wet dust collectors use liquid — often but not always simple water — to capture and separate dust, mist, fumes, and other particulate matter from a stream of flowing gas — often but not always simple air. Some wet dust collectors spray liquid in a sheet across the stream of gas; others bubble the gas through the liquid. Other more complex hybrid versions that add other capacities like oil mist collection.
The particle sizes that can be properly taken care of by a wet dust collector range from 0.3 microns to just over 50 microns in size — the vast majority of airborne dusts and mists. Many such collectors filter out the particles for collection, should there be a secondary economic value to them.
Compared to dry dust collectors, wet dust collectors:
- Allow for constant operating pressure.
- Cause no secondary dust.
- Have few moving parts and are thus low-maintenance.
- Can filter out suspended particulates (gasses) as well as solid and liquid particulate.
- Can handle high-temperature and high-humidity gas streams and act to reduce the volatility and fire danger thereof.
- Have reasonably small footprints, should space be an issue.
- Collect even sticky and hygroscopic pollutants without becoming fouled itself.
There are three major mechanisms by which wet dust collectors work:
Inertial: When a dust particle and a water particle collide, the dust particle enters the liquid particle, and the resulting mass is heavier than the surrounding gas stream. It either falls out of the gas stream or hits a separator and is removed.
Brownian: Particularly small particles have motion independent of the carrier stream. When these minute particles hit the water stream, they don’t so much impact the water as they diffuse into it. The physical mechanic may be different, but the end result is the same: they effectively become part of the water and fall out of the gas stream.
Condensation: When using very cold water, the gas stream is cooled below it’s dew point, and any particulate in the gas becomes the nucleus of a droplet of condensation. Again, the mechanism is unique, but the result — the particulate falls out of the gas stream as the stream keeps blowing on — is the same.