Dust Suppression Systems
EFFECTIVE WET SYSTEMS TO CONTROL DUST
Based on the elements of your operation, there are many factors to take into consideration when considering spray technology as your dust suppression solution. A few of these factors include: the process and material producing the dust; where in your operation the dust is being generated; and the utilities and resources (electricity, compressed air, water, labor, etc.) available.
Wet systems using spray technology are used for dust prevention (humidity/moisture content in the material is increased to prevent dust from becoming airborne) and dust control/capture (humidity/moisture is added to the air to capture dust particles that are already airborne).
These systems use spray nozzles to apply water and/or chemicals such as wetting, foaming and binding agents to dust particles. However, the system configuration varies depending on the goal – dust prevention or airborne dust control in mines. Most operations require both prevention and suppression to effectively control dust. It is important to understand the differences between these two systems to ensure proper spray nozzle specification and operation. See Figures 1 and 2.
No matter the application, wet systems are a popular choice as they are highly effective and implementation is typically fast and straightforward. Wet systems provide a long-term solution that can provide years of trouble-free performance with regular maintenance.
TYPICAL OPERATIONS
Dumping
Transport
Transfer points
Stockpiling/reclaiming
Load bins
Screens
Conveying
Shearing
Continuous mining, Crushing and screening
Dryers
Packaging/filling
Fundamentally, wet dust suppression systems are the same – all use water sprays. However, that’s where the similarities end. There are many variables to consider when specifying a spray system:
Dust particle size
Spray pattern
Operating pressure
Nozzle placement
Control options
Spray drop size
Spray angle
Surface wetting
Water quality and availability
LEARN THE BASICS OF DROP SIZE
- Air atomizing nozzles produce the smallest drop sizes, followed by fine spray, hollow cone, flat fan and full cone nozzles (see graphic below)
- Higher pressures yield smaller drops, and lower pressures yield larger drops
- Lower-flow nozzles produce the smallest drops, and higher-flow nozzles produce the largest drops
- Increases in surface tension increase drop size
- Drop velocity is dependent upon drop size. Small drops may have a higher initial velocity, but velocity diminishes quickly. Larger drops retain velocity longer and travel further
Stages of spray pattern formation
FIGURE 4: If the drop diameter is larger than the dust particle diameter, the dust particle will follow the air stream around the drop. (Shown left.) If the diameters of the drop and the dust particle are comparable, the dust particle will follow the air stream and collide with the drop. (Shown right.)
