Dust suppression

Engineering consideration 4 - Wetting avoidance

In many dust suppression applications it is undesirable to cause excessive wetting to the source of the dust.  For example, the production of processing dried food stuffs may cause dust and whilst this needs to be prevented the source material needs to remain dry.  In order to achieve this an equilibrium between the delivery of dust suppressing fluid being applied and the removal of the fluid by evaporation needs to be established.  When equilibrium is achieved the levels of fluid will not build up and so wetting will not occur.  In effect the steady level of fluid acts as a conveyor carrying dust particles back to the source material.

Low flow rate hydraulic nozzles

The rate of removal of fluid from the system by evaporation is often quite low so in order to establish the equilibrium described above spray nozzles with low flow rates are often needed.  At the same time though small droplet sizes need to be maintained as :

a) They present more surface area to make contact with the dust.

b) Droplets of similar sizes to the dust particles are more likely to remove them (see droplet size matching engineering consideration).

Low flow rate variants of a variety of nozzle designs may be suitable for these applications.  The L series is a low flow rate spiral nozzle but for non-windy environments a low flow rate mist producing nozzle, such as the PJ or MicroWhirl, might be more appropriate.  These nozzles produce a fine mist at relatively low flow rates.

Air atomising Nozzles

Hydraulic nozzles (like the spirals and misting nozzles described above) rely entirely on the energy of the spraying fluid itself to break it up into a spray.  The finer the droplets that need to be formed the more energy is required.  As the energy of a fluid is a function of pressure and flow rate, this means that hydraulic nozzles are unable to form very fine sprays at very low flow rates.  If the dust suppression application necessitates a flow rate below that maintainable by a hydraulic nozzle then air atomising nozzles will need to be used.

Further details

Details on the features of air atomising, small orifice misting nozzles and impingement misting nozzles can be found by clicking on the grey "Dust Suppression Nozzle Designs" menu to the right hand side of this page.  How the different features of these nozzles might be applied to dust suppression application problems are discussed and further links to relevant product specioifiction sheets are provided.