Wet and Dry Dust Suppression Systems

What are dust suppression systems?

These are wet or dry techniques that use either dust suppressants or baghouse filters to bind or collect fine dust particles respectively. The dust suppression systems must be placed strategically for the dust suppression to be effective. In wet dust suppression systems droplets absorb the dust particles in the air whereas in dry dust suppression fabric filters are used to vacuum dust. Our discussion is more inclined towards wet dust suppression systems. The mechanism of action of the microscopic droplets on the fugitive dust involves binding and the increasing the weight of the dust particles. As a result of the weight increase, the heavy dust particle falls back down to the ground and stays on the surface rendering a dust-free environment. The choice of dust suppression system depends on many factors and in all honesty, there is not a perfect fit for every type of dust particle. We cannot emphasize enough the importance of chemistry in the appreciation of making informed choices on a selection of dust suppressants to use with a particular dust suppression system. Factors such as type of dust (silica dust, coal dust, metalliferous dust or asbestos dust), how the dust is generated (haul roads, drilling, blasting, transportation, veneering, conveyor belt transfer points and stockpiles) and availability of water supply (water scarcity, reuse of water, making water work with water savings and frequency of repetitive water use) play a pivotal role in careful considerations for decision making. The application of dust suppression systems is critical in mining, quarries, ship loading, construction, concrete plants, waste transfer stations and material handling. Stay with us, as we continue to unpack the very interesting discussion. 

In this article best dust suppression systems are evaluated from the following:

• The ‘science behind wet dust suppression is a closer look into droplet behaviour.
• Wet dust suppression systems.
• Wet vs dry dust suppression systems.

The ‘science behind wet dust suppression’ a closer look into droplet behaviour

The science behind wet dust suppression droplet behavior is best explained in terms of reduction of dust and less of moistening the area of interest which comes with limitations of low efficacy of using water alone. Water molecules in the free state tend to be very unstable and have a low energy level hence they tend to recombine into larger droplets. The misting and fogging methodologies prevent that from happening, but it does not replace the importance of chemistry as water from a molecular point of view is an electric dipole. That means that water attracts towards finer particles of silica dust in the process binding them. The dust particle which is an aerosol incorporated into the droplets of the dust suppressant. Success in bonding is measured as the binding that happens on impact against the dust particle without rebound and resuspension. Dust suppression systems copy and mimic natural phenomenon with the principle of spraying dust suppressants into the atmosphere in the form of drops. The downfall of using water alone in applications of dust suppression systems includes (1) water scarcity because of massive amount of water requirements (2) water/surface ratios are usually high. It is then important to get dust suppressant droplets of appropriate size and dust suppression systems reduce the dust suppressant to a state of suspended practically vapor. This is achieved using nozzles with appropriate dimensions. The following section will dive deeper into misting and fogging to complement the science behind dust suppression. 

Wet dust suppression systems 

There are different types of wet dust suppression systems and the techniques they utilize to change the dust suppressant droplets are misting and fogging. Nozzles play a huge role in the misting and fogging of dust suppressant droplets. The appropriate dimensions of nozzles enable droplets less than 80 microns to generate a mist with other droplets of diameters between 10 and 50 microns. Effectively a controlled surface for misting to take place with the dust suppressant in suspension enables the capture of dust particles and carry-overs to the ground without creating pools of mud. Misting enables a reduction in water consumption and the presence of microscopic droplets to inhibit dust from circulating throughout the area of dust suppression. There are different types of misting systems which include static line misting, mist fans fixed to walls and 360 mist fans suspended which can be used for dust suppression. Misting can be applied to for both indoor and outdoor applications. Fogging on the other hand doesn’t have the level of accuracy of misting as it treats an area as opposed to a surface. Fogging is a technique where a dust suppressant is atomized and distributed around a surface to maintain enough moisture levels in the air to bind, coalesce and suppress fugitive dust particles. In the fogging process, air atomization enables tiny particles of dust suppressant to increase the number of droplets and reduce the surface tension of the dust suppressant. Therefore, dust suppressant droplets collide with the dust particles, instead of the dust bouncing off the ‘skin’ of the dust suppressant, they emerge, and the increased weight of the dust particle causes it to fall to the ground. It is important for dust suppression systems to control airborne dust without wetting the site product and machinery. 

Wet dust suppression systems vs Dry dust suppressions systems

Dust suppression systems are used to control dust through various techniques. Our discussion compares wet dust suppression systems to dry dust suppression systems. The application of dust suppression systems is for dust particles generated in different industries. Dry dust suppression systems use collection systems that implement bag houses with fabric filters that vacuum dust from the source and collect it in a hopper for disposal. In wet dust suppression systems, a wet dust suppressant in the form of a spray (mist or fog) is commonly used to control fugitive dust particles. The most common form of wet dust suppression systems are water spray technologies, but over time products such as liquid polymers, and surfactants that make water work have emerged as major dust suppressant solutions in the interest of saving water and redirecting water to other crucial areas. Making water work also contributes positively to performance, especially for materials like coal that are difficult to wet even with misting and fogging systems. Unlike dry dust suppression systems, wetting behaviour complements chemistry. The metamorphosis of coal in addition to its different elements requires hydrophobicity to take over hydrophilicity. Water alone is not enough to bind the coal dust particles. 

Can we end dust?

Ending dust at its source is the most ideal situation, but truth be told not having any dust is practically impossible. The reality is that you must eliminate dust with effective dust suppression solutions. It should not only be in compliance with local, state and federal laws to implement dust suppression systems. Dust suppression systems ought to be implemented to save lives. Occupational hazards such as dust result in loss of life and diseases such as silicosis and black lung disease are incurable. In conclusion, the best solution is to avoid creating or try to eliminate it at its source. Nevertheless, some processes do generate dust that cannot be trapped. It becomes airborne and must be suppressed or captured. 

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