Breathing in dust at work is a serious issue, and can lead to a variety of illnesses and diseases. This is particularly true in the mining and quarrying industries, where the potential for exposure to dust is much higher than in other fields, and the composition of the dust may be more toxic.
Hence, dust suppression is critical to these industries. Dust not only affects the health and safety of mine and quarry workers but also threatens that of the residents in surrounding communities.
Arresting the spread of dust has typically involved the use of water as it is easily obtainable and stored. Water is also easy to deliver to the exact point of dust origin.
Dust suppression technology through the use of nozzles stops dust from getting scattered before it even becomes airborne. However, you need to consider the type of dust when choosing the right nozzle for dust control.
Nozzles are typically used for pre-wetting material or controlling dust leaving the confines of barrier-type suppression systems, such as enclosed transfer points in conveyors.
In this article, we’ll limit our discussion to the use of smaller applications: temporary, small and medium spray nozzles. We will not be talking about bigger spraying equipment like water cannons or stockpile sprays.
Before talking about selecting the best nozzle for specific dust suppression requirements, let’s first look at pressure atomising nozzles and air atomising or two-fluid nozzles.
Pressure atomising nozzles make use of the water pressure without the need for compressed air. There are two major types of pressure atomising nozzles:
Air atomising or two-fluid nozzles mix the water with compressed air leading to the formation of small droplets. A major advantage of air atomising nozzles (such as the XA series) is that you can use air pressure and flow to control droplet size. However, these require continuous quality air flow and filtration (a higher level of water purity) to prevent clogging and other maintenance issues.
Selecting the right nozzle as part of a dust suppression solution depends on the situation. However, there are basic principles that apply to the use of dust suppression products such as nozzles. These include:
Once all of these factors are sorted out, you can then move on to determining the number of nozzles you need.
For static or non-moving applications such as a large cross-sectional area, you can use a conical nozzle as a dust prevention application. Doing this will also prevent the area from over-wetting. If the products to be sprayed are moving under the nozzle, such as with conveyor systems, a fan spray positioned at a right angle across the conveyor might work best.
Selecting the right nozzle is critical in ensuring your dust suppression system produces the right droplet size. The droplet diameter needs to be of comparable size to the dust particle to ensure contact and collision.
Otherwise, if the droplet diameter is significantly larger than that of the dust particle, the dust will simply follow the air stream around the droplet and not make contact. Therefore, for maximum agglomeration, it is essential for the dust particles and water droplet sizes to be more or less of the same size.
Smaller droplets work in suppressing finer dust particles or fine airborne dust. You can use hollow cone spray nozzles for this purpose. Another alternative would be to use air atomising nozzles that produce small droplets. Note that these are better suited for protected areas that are not subject to wind drift, or areas with very fine dust particles.
Nozzles that produce fog-like droplet sizes require excellent filtration in order to produce like-sized water droplets that can effectively capture similarly sized fine dust particles.
To get assistance with the various dust suppression methods and dust solution products needed for your specific applications, please get in touch with Spray Nozzle Engineering.