Wet Dust Collectors

Wet Dust collectors use scrubbing liquid, which comes into contact with dusty air. If the contact between the air and liquid is greater, then the efficiency of dust removal will be higher.

There are three features shared by each type of wet dust collector:

• Gas-humidification - This increases the size of fine dust particles so that they can be collected easier.

• Gas-liquid contact - This is one of the most important factors affecting the efficiency of dust collection. Four primary mechanisms bring dust and water into contact:


• Inertial impaction - When water is placed in the path of a dust-filled air stream, the stream separates and flows around them. Due to inertia, the larger dust particles will continue on in a straight path, hit the droplets, and become encapsulated.
• Interception - Finer particles moving within an air stream do not hit water droplets directly, they, however, brush against them and adhere to them.
• Diffusion - When liquid droplets are scattered among dust particles, the particles are deposited on the droplet surfaces. This is the principal mechanism in the collection of dust particles that are smaller than a micrometre.
• Condensation nucleation - If air passing through a scrubber is cooled below the dewpoint, condensation of moisture occurs on the dust particles. This increase in particle size makes collection easier.


• Gas-liquid separation - Once contact is made between dust and water, the two combine to form agglomerates. As the agglomerates grow larger, they settle into a collector.

The cleaned gases are normally passed through de-mister pads to remove water from them. The dirty water from the scrubber system is either cleaned and discharged or recycled to the scrubber, removed from there by a drag chain or clarification unit. In both systems, solid material settles on the bottom of the tank, removed and deposited into a dumpster by a drag chain.

Types of scrubbers

Spray-tower scrubber wet scrubbers may be categorized by pressure drop as follows:

• Low-energy scrubbers (0.5 to 2.5 inches water gauge - 124.4 to 621.9 Pa)
• Low- to medium-energy scrubbers (2.5 to 6 inches water gauge - 0.622 to 1.493 kPa)
• Medium- to high-energy scrubbers (6 to 15 inches water gauge - 1.493 to 3.731 kPa)
• High-energy scrubbers (greater than 15 inches water gauge - greater than 3.731 kPa)