When the initial plant design or modifications to contain dust have failed, some operators resort to air-lift or scrubbing systems. Baghouses, wet scrubbers and cyclones are expensive in terms of capital cost and maintenance. Also, there is an additional cost of rehandling the collected fines or slurry.
Dust suppression is a less expensive technology using water sprays that create fine water droplets to impinge on the fines, to collect and settle them back onto the conveyor or stockpile.
Even without resorting to chemical additives, the use of compressed air atomizing nozzles can control particulate with a minimum volume of water in stationary as well as portable installations.
Addition of wetting agents or foaming surfactants can be used to extend the suppression effect over very long multiple transfer point conveyors.
One of the most successful developments in the industry's campaign to control fugitive particles is a low cost Dry Fog® dust suppression system from TurboSonic. The system agglomerates dust at the source through a fine spray of thousands of tiny droplets. It can be installed at breakers, crushers and screws as well as transfer points.
A TurboSonic dust suppression system includes SoniCore® atomizing nozzles, a source of compressed air, a sequencing circuit, linear actuators or simple on-off controls depending upon site requirement. The Dry Fog® dust suppression system controls respirable particulates 0.1 to 3 microns in diameter and larger airborne particles. These 'fines' are considered the principal source of dust clouds, haze and accompanying low levels of visibility. In most applications where respirable dust particles can be settled out of the atmosphere quickly, the TurboSonic system makes it unnecessary to add a tension active chemical to the water thus keeping costs low.
The nozzles are air driven acoustic oscillators which atomize liquids by passing them through a field of high frequency soundwaves. The air expands through a convergent/divergent section into a resonator cap where it is reflected back to primary shock-wave.
The result is an intense field of sonic energy focused between the nozzle body and the resonator cap. Compared to water-only sprays, the TurboSonic Dry Fog® system's efficiency requires as little as 10% of the water volume for effective control.
In one example, a TurboSonic dust suppression system was given the tough job of suppressing siliceous dust at a quarry producing 100 tons of silica sand each day. With the help of 13 SoniCore® nozzles strategically located in the feeding sieves of three Rollercone gyratory crushers, the dust particles were agglomerated and settled down as the silica sand was discharged from crushers to conveyors.
The TurboSonic Dry Fog® Dust Suppression System provides these benefits:
- less product wetting than conventional water spray systems (less than 0.5%);
- lower capital costs than baghouses or scrubbers;
- costly wetting agents and their controls eliminated;
- no conveyor belt wetting or accompanying tracking problems;
- less conveyor downtime and fewer conveyor belt replacement parts;
- nozzles operate on low pressure air and water to eliminate need for expensive pumping systems;
- improved working conditions enables compliance with applicable health and safety regulations;
- cleaning and maintenance costs reduced;
- permits recovery of spilled materials.