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There are several existing methods of controlling dust but many are ineffective, costly and have detrimental effects on plant and machinery.
An effective system for the control of fugitive dust in industry should meet the following objectives.
- Must be efficient to meet Health & Safety requirements.
- Be practical and simple in operation.
- Have low initial cost.
- Have low operating costs.
- No adverse effects on product quality or plant and machinery should be created.
The Ultrasonic Atomising System has therefore been developed in order to meet these requirements and overcome the problems associated with other dust suppression operations.
The theory behind the Ultrasonic Atomising System is based on research considering a water droplet, from a spray, that is about to impinge on a dust particle.
If the diameter of the droplet is much greater than the dust particle then the dust particle is simply forced away by the airstream lines around the droplet and little or no contact occurs.
If, on the other hand, the water droplet is of a comparable size to the dust particle then contact occurs as the dust particle attempts to follow the airstream line.
The probability of impaction increases as the size of the water spray droplet decreases.
This explains why conventional hydraulic water sprays are not effective on respirable dust. With typical diameters of 200-600 microns the droplets are much larger than the dusts they are attempting to suppress.
The Ultrasonic Atomising System generates droplets averaging 10 micron in size and is capable of suppressing sub-micron dust particles.
In addition to this particle size theory, the results of additional research indicate there is another significant phenomenon that occurs when Ultrasonic Atomising Systems are applied to dust suppression.
The effect can be compared to an electrostatic precipitator in which dust particles are charged and then collected on plates of opposite charge. It was found that dust particles generally carry certain negative potential depending on the nature of the dust and the ambient conditions.
Water droplets produced by the nozzles carry a charge that is strongly positive in relation to the dust particles.
The result is that the probability of collision between a droplet and particle is greatly increased from the spatial probability, implying the need for fewer water droplets to ensure the desired efficiency.
Thus, a nozzle generating a dense fog of 1-10 micron size droplets can be used to envelop and smother dust particles at their source and prevent them from becoming airborne.
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