Increasing Particle Size
If enclosing the transfer point is not an option, then increasing the size of the particles of dust to make them heavier and more prone to dropping from the airflow may be the solution. Increasing the size of the particles of dust will make the dust particles heavier. A heavier particle will not be so easily picked up by air movement, and it will fallow out of the air more readily when air velocity slows. A heavier particle also will have more momentum, so it will not be as affected by shifts in airflow.
Dust-suppression systems are generally based upon the principle of increasing dust particle weight to improve dust control and return the particles to the main material stream. These systems increase the weight of airborne dust particles by combining the particles with drops of water (or with a water-and-chemical solution). The wet, and now heavier, dust particles fall back into the material stream before they can escape into the atmosphere.
It is relatively difficult to capture dust particles once they have become airborne. Fog dust-suppression systems specifically target dust in this difficult state. A fog system needs time and relatively undisturbed space to bond with airborne dust particles. This necessitates an enclosed transfer point and relatively slow moving air. Fog systems are more successful when the dust particles and water droplets are of similar size. To achieve the small water-droplet size necessary to match the small particles of airborne dust, the water must be pumped at high pressure through atomizing nozzles or atomized with air. Both methods for making small water droplets to match small particles are expensive and complicated.
Dust collection is also used to increase material size. This method uses a vacuum to pull the air (and the dust it carries) out of the material-handling system. The dust agglomerates to itself or on the surface of the filter system and is then collected at a central location or deposited back onto the belt with the use of local collectors.
Dust-collection systems require the enclosure of the transfer point(s) and a substantial amount of overhead space. Such systems do nothing to reduce the material’s potential to create dust: When the material is agitated at the next transfer point, dust must be dealt with again.