Various substances are used in the suppression of dust, ranging from surfactants to chemicals, but the use of water still remains very relevant. Although the use of water, just like the other methods of dust suppression, has its own limitations, it remains one of the most environment-friendly and effective methods of dust suppression. However, the effectiveness of dust suppression spray depends on many factors.
The variables to consider:
The following are some of the variables that determine the effectiveness of water spray in the suppression of dust:
Dust particle size
Spray drop size
Spray pattern
Spray angle
Operating pressure
Dust particle size:
The size of the dust particle is important as it will determine the size of water droplet required to catch and suppress it. The following table shows the average size of various dust particles
Dust particle
Size ( in microns)
Ground limestone
10 to 1000
Fly ash
10 to 200
Coal dust
1 to 100
Carbon black
0.01 to 0.3
Pulverized coal
3 to 500
Spray drop size:
Once the size of the dust particle is determined, the drop size should be calibrated to ensure it is of almost equal size. Also, the water droplets should be delivered in the form of very fine particles. This is the reason why atomization is a common term in dust control, and it refers to the process of converting water into very fine droplets. The size of the nozzle and pressure determine the size of the water droplet.
If the water droplet is larger in size than the size of a dust particle, the two may not collide and there will not be effective suppression of dust. If the size of the water droplet and that of water are comparable, there is more likelihood that the two will collide, effectively suppressing the dust. When the water droplets are smaller in size to the dust particles, the two may collide but the water will evaporate too quickly, and the trapped particles will be released into the air.
Spray pattern:
Different spray patterns produce different results in the suppression of dust. For instance, a misting cannon releases the water in the form of cloud which covers the source of dust, capturing it and ensuring do dust escapes to the air. It must be carefully designed to avoid wetting of the area.
Spray angle:
The spray angle mostly ranges between 00 and 1750. The required angle is determined by nozzle placement, a number of nozzles and the spray pattern.
The rate of flow and operating pressure:
The rate of flow and operating pressure are determined by the amount of moisture that should be applied. In this regard,
The increase in pressure will reduce the size of a water droplet.
High pressure is most suitable in enclosed areas.
Nozzles operating at high pressure need to be placed as close to the source of dust as possible. In order to minimize the amount of air which sets in motion along the water spray path.
