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 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.
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.
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.
Fog cannons also have some shortcomings –
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, 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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