Dust suppression uses a variety of methods and equipment ranging from sophisticated stationary exhaust ventilation systems, cyclone separators and electrostatic precipitators to sprinklers, water monitors and fog guns that spray water, chemicals and foam.
Modern dust suppression equipment
Dust reduces visibility on the roadway, increasing the risk of accidents and slowing traffic speeds. Dust from explosive and combustible materials in the air poses a risk of explosion or fire. An increased amount of dust has a negative effect on the condition of machinery. In addition to mechanical wear (ingress of abrasive particles into moving parts), machine control systems may malfunction as an excessive amount of dust penetrates electronic control units. The service life of engines operating in dusty environments is reduced by 2-3 times. Exposure to dust increases the intensity of the corrosion process, maintenance and repair of equipment becomes more difficult and time-consuming.
Therefore, dust suppression solutions are extremely important and are used in many industries. Dust suppression is a very broad concept. We will consider only a part of it in this article – a complex of ways and means to prevent dust pollution in construction and mining industries by reducing dust emission and precipitation of dust from the air.
In the process of mining, dust is always formed – during crushing, blasting. Ash and slag dumps of metallurgical plants and thermal power plants, as well as open-cast mining pits emit up to 2-5 tons of dust per day per hectare into the atmosphere; dust is blown long distances by the wind. A lot of dust enters the air from open ore and coal storages in ports.
At open pits and construction sites, 19% of dust is caused by wind erosion of the soil. Vehicles and special equipment moving on technological roads raise 52% of the dust into the air. As a result of pressure and movement of tires at speeds over 15 miles per hour, small stones on technological roads are destroyed and the resulting dust is released into the air.
A considerable amount of dust is generated during construction work. During finishing work, circular saws and grinders create the most dust. If a huge building must be demolished, the surrounding area must be carefully protected from dust. Dust suppression and protection from fumes in hazardous waste landfills are very important. This is only a brief and incomplete list of dust sources.
Methods and equipment for dust suppression
Most experts agree that there is no single solution to all the complex problems of dust control and a universal, completely safe and productive method of dedusting. In each case these issues are addressed individually.
In developing a method of dust suppression, it is recommended to analyze the following questions: what is the main source of dust generation and where it is located, what process creates the largest amount of dust in the air, and where are the most sensitive areas to airborne dust?
Irrigation with water, sprinkler systems
Irrigation by water spraying with stationary and mobile sprinklers and water monitors has been a common method of grain dust suppression for a long time.
Stationary sprinklers are used as the main method of dust suppression during the operation of roadheaders. Many roadheaders are equipped with their own sprinkler systems – they wet the rock surface. Sprinkler systems on the ceiling or walls of the adit are used for premises and underground roads. Long-range sprinkler systems are used for dust suppression of stacked materials. A lot of fugitive dust is generated when dumping dump trucks into the crusher bunker or into the waste rock dumps. For its suppression it is recommended to use a sprinkler system, which is mounted on the rear wheels of the dumping truck and during the unloading it strongly moistens the material being unloaded.
Fogging systems and fog guns
Fine respirable dust from the air can be precipitated with water mist. The use of water mist, which is generated by different types of equipment, is another modern, evolving method of dust suppression. Fogging systems are recommended for applications where sprinkler systems are not suitable or do not suppress dust formation sufficiently, for example, to create a fog screen near the bunkers of crushers.
In some cases, spraying foam to coat the material is more effective than water mist. By spraying foam into the areas where the material is broken, the access of the air to the dust source and the possibility for the dust particles to escape into the atmosphere of the excavation are decreased. Chemical dust suppression is also often used for such applications and can help make the process intrinsically safe.