Atomization is to reduce the surface tension of the water droplets and also increasing the number of droplets in a given area and also remove the need for the addition of other additives. The small level of water added through the fog and mist systems - typically at 0.01% to 0.05% by weight of the water.
There are two methods of producing atomized water mist which is commonly used,
Two-Fluid Atomisation :
One of the common methods of producing mist from water and compressed air is by passing them through a two-fluid nozzle. The external air supply is the vehicle that fractures the water supply into the droplet mist to capture the dust.
Single-Fluid Atomisation :
This system uses a very good ultra-thin stream of water pumped through the nozzle at high pressure. It does not need any compressed air or an additional power source other than the electricity to run its pump. Single-fluid nozzles use hydraulic atomization to generate the mist.
Research literature has long recognized that small droplet size is the key to a dust suppression system. The following explanation comes from work at the Colorado School of Mines:
When water droplets that are sprayed to control coal dust are too large, the dust particles flow around the droplets and thus are not absorbed but water droplets too small simply evaporated. So CSM is looking into theories governing the formation of clouds to improve existing water spray technology.
Experience gained over the years with water sprays has established the following fact
For a given spray nozzle, the collection efficiency for small dust particles increases as the pressure increases.
At a given pressure, the efficiency increases as the nozzle design are changed so as to produce smaller droplets. The conclusion is clear-cut; the smaller droplets are more effective in knocking small dust particles out of the air. The reason for this is not hard to see.
Consider a water droplet about to impinge on a dust particle, or what is aerodynamically equivalent, a dust particle about to impinge on a water droplet, as shown in the drawing. If the droplet diameter is much greater than the dust particle, the dust particle simply follows the airstream lines around the droplet, and little or no contact occurs. In fact, it is difficult to impact micron-size particles on anything, which is why inertial separators do not work well at these sites.
If, on the other hand, the water droplet is of a size that is comparable to that of the dust particle, contact occurs as the dust particle tries to follow the streamlines. Thus the probability of impaction increases as the size of the water spray droplets decreases.
Moistening guns are a compelling method to control undesirable particles on location. They have bunches of advantages to diminish dust relocation and set aside cash in everyday tasks. The machines give fine beads of water to catch and drop residue to the ground, diminishing generally water utilization while running automatically.