Fog Cannon Dust Suppression – Advantages and Disadvantages

A fog is a high-powered fan or jet with specially engineered nozzles sprays dust suppressants to bind dust particles. The fogging process involves the action of fog nozzles which nebulize water into very small micro-droplets of water under pressure. The fog drives airborne dust particles to the ground and wets the surface to prevent fugitive dust particles. The water atomized mist produced has a small particle size range and its particle size can even be less than 10 microns. When water is combined with dust in the air, due to the adhesion of the surface of water molecules, it will be combined with the dust, and the effect of gravity will drop after condensing, to achieve the purpose of dust suppression. The fog cannon machine is suitable for dust suppression, construction site dust reduction, demolition dust reduction. Applications extend to urban development zones, station coal storage yards, coal washing plants, coking plants, iron mines, steel plants and ports. The main function is spray dust suppression. Fog cannon machines can spray dust particle in the respective areas of concern, with the ability to decompose and desalt the particle concentration in the air and quickly force down the polluting particle and dust floating in the air. 

This article discusses 

• The science behind fog cannon dust suppression
• The components that make up a fog cannon dust suppression system
• Its advantages and disadvantages, then
• Its applications in different industries

The ‘science’ behind fog cannon dust suppression

The core theory in fog cannon dust suppression is the Slipstream Effect. To bind fugitive dust in the air and bring it to the ground, the dust suppressant droplet and dust particle must be comparable. The dust particle is more likely to collide with the droplet and be absorbed, driving the dust to the ground. Smaller dust suppressant droplets and enough water are the recipe to incredible coverage. Smaller droplets have the potential to travel farther because of the higher of surface area to mass, which means the influence of air pressure compared to gravity is relatively greater. Therefore, the air will keep them buoyant longer before the effect of gravity brings them down. The science is that heavier water droplets are susceptible to gravity more quickly like clouds where when water droplets grow too large, they fall as rain. Smaller droplets can be more prone to evaporation, which is why you need the right nozzle for your situation. In some cases, it might be the desired effect depending on your situation. The tiny, water droplets form a dense fog and trap the dust particles increasing their weight which causes them to fall from the air. The fog cloud also needs to be greater than the concentrations of dust particles in the air so that all the dust can be captured. 

What are the components of a fog cannon dust suppression system?

1. Nozzle: atomize the water into suitable dust-reducing water mist particles, thereby speeding up the dust-reducing speed and making the spraying more uniform.
2. Water pump: The heart of the dust removal fog gun machine, which mainly realizes the delivery of water from the water tank to the nozzle and atomizes the water through high-pressure water flow.
3. Fan: produces high-speed airflow. When the fan wheel rotates, the high-speed airflow is ejected from the air outlet to blow the fine droplets formed by the nozzle atomization to the required area.

Generally, centrifugal fans with convenient driving, high wind pressure, high wind speed and strong air penetration are adopted. The blades adopt backward curved blades with higher total pressure efficiency, which can ensure the spray range and improve the atomization effect.

4. Turning and positioning device: the outlet direction of the air outlet pipe can be rotated 360° in the horizontal plane (generally, it can only be rotated at 350° in actual operation) to adapt to the change of the operating wind direction, and there is another setting in the air outlet pipe. A steering positioning device is used to adjust the elevation angle of the air outlet.

What are the advantages and disadvantages of fog cannon dust suppression?

The key criteria to consider benefits of fog cannon dust control would be reduction in volume of water used from the dust suppression system and the elimination of residue. The advantages of using fog cannon dust suppression are mostly application dependent.

• With fog cannon systems you use water more strategically and achieve lower associated cost. Reduced stormwater effects and runoff, which are critical in keeping air and land pollution in balance. Fewer pools of water to ensure a safer and more efficient worksite.
• Fog cannon dust suppression avoids product over-saturation, often creating a muck that is difficult to handle and sticks to facility surfaces and equipment, shortening life of both.
• With fog cannon dust suppression, one achieves reduced labor costs due to automated operation. Plug, play and forget about it! Water flow rates can be adjusted to regulate the volume of water discharged forms the fog cannon to control both surface dust and airborne dust without saturation problems.
• The cannons can be set up in a fixed or mobile position depending on the site-specific needs. Fog cannon dust suppression contribute to the popularity of wet dust suppression choices. They are highly effective, and implementation is fast and straightforward. Provision of long-term solutions that can provide years of trouble-free performance with regular maintenance.

Fog cannons also have some shortcomings – 

• First, they are incapable of significant coverage due to evaporation.
• They also have limitations in the requirement of a controlled environment. Ideally, an enclosed environment, with no wind movement. The fog must stay in the air, undisturbed and prolonged to be able to slowly bond to dust particles.
• Finally, when dust particles are hydrophobic in nature, the fog will only act as a barrier, rather than capturing the dust and dropping it from suspension. However, the addition of technologies such as GRT: Activate can greatly improve the function and outcome of fogging systems for dust control.

What are the applications of a fog cannon dust suppression system?

Fog cannon dust suppression systems are designed to tackle the problem of airborne dust particles generated from mining activities, demolition sites and bulk material handling sites. The fog cannon units come in different sizes. The smaller units are ideal for suppressing dust where it is generated in high concentrations at easily defined point sources such as discharging onto stockpiles, discharging into ships, reclaiming from stockpiles, dumping, crushing and loading/unloading trucks. The fog cannon is directed at the point source of the dust, and it rapidly suppresses the emitted dust before it can disperse. The larger units can suppress general airborne dust through fogging the general area. They are also capable of suppressing dust caused by high volume dust events such as blasting, and the low throw distance is usually necessary for this. Fog cannons are also useful for dust suppression of stockpiles where their low water use is an advantage. Throw ranges of fog cannons vary from 30 to 500 meters and they utilize powerful fans. Automatic rotation can be up to 360 degrees with adjustable elevation angles from 0 to 45 degrees. Water consumption varies from 15 liters/min up to 6000 liters/min depending on the model and application. Chemical dust suppressants such as surfactants and liquid polymers can also be added to spray to either make water work or develop a crust on the stockpiles. Other fog cannon system accessories include telescopic elevation systems, remote control including remote camera, intrinsically safe version for explosive atmospheres and self-contained vehicle units. 

Dust management

Dust, if not managed effectively, can reduce productivity, have a serious impact on operational costs, damage the environment and cause harm to the safety of workers and surrounding communities. The fog cannon produces a mist from water which effectively suppresses airborne dust particles. Dust kills and binding it at its source helps to save lives. GRT advocates for dust suppression to minimise the risk to miners, workers and communities with the vicinity of dust generating activities. 

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