Prevention is better than a cure. In coal mining, these words offer particularly good guidance. Underground mining presents numerous hazards ranging from structural collapses, flooding and explosions. The tremendous amount of dust generated by activities in a coal mine creates breathing-related problems for workers as well as maintenance issues for machinery. Dust can also create a potentially explosive environment. Injuries and deaths occur every year either from accidents or health issues caused by exposure to coal dust. Mining companies can dramatically reduce these risks by applying rigorous dust suppression safety measures.
This blog investigates dust suppression methods and evaluates preventative versus corrective techniques that can effectively be used to suppress dust in underground coal mines, reducing the risk to workers and equipment.
Coal dust is a known carcinogen that causes miners’ lung disease (pneumoconiosis). Dust in the atmosphere can also create an ignition hazard when mixed with gas. Coal dust buildup is often a root cause of premature maintenance and failure of mining equipment. To this end, preventative suppression is critical.
There are a variety of ways to suppress dust in coal mines that offer a varying degree of effectiveness and efficiency. The most common methods are:
Bag filter system uses fans to circulate the air and trap the solids in a bag. However, this type of system is maintenance-intensive and requires bag filter change-outs — which is not conducive to work in an underground mine.
Dry fog system requires electricity, making it impractical for work below ground level.
Water is an ideal solution because it takes advantage of the mine's existing water supply, forming it into a spray to suppress the dust as soon as it is generated at the coal extraction point and all other areas where dust is generated.
Logically, if a problem can be prevented from happening, then the time and cost of fixing it can be saved. Preventing dust from becoming airborne is critical in dust suppression. Three important elements to successful preventative suppression using water include:
Control pertains to how the water is controlled. It may be controlled by the presence of coal on the conveyor or by the belt’s motion. In either case, the water is isolated before entering the system.
Filter technology is used to remove contaminants from the water to assure reliable system operation.
Spray refers to a predetermined volume and pattern in which the water is delivered to the coal before the dust is generated.
The figure below shows a typical belt conveyor transfer point dust suppression system has two options: paddle valve (A) or belt-driven valve (B). Both are designed to operate only when there is coal on the conveyor.
Corrective or symptomatic dust control is implemented after the dust is created and is more challenging than preventative dust control. Dust particles come in a range of sizes with some as small as 10 µm which is invisible to the human eye. These small particles are the most dangerous to workers and equipment because they can remain airborne for long periods of time and eventually find their way into miners’ lungs, onto and into machinery as well as outside of the mine itself. Small particles are also the most difficult to remove from the atmosphere. Airborne coal dust can be addressed correctively using sprays. The principal is that the dust agglomerates with the water, causing it to fall under gravity. However, if the water droplets are too large, then the airborne dust particles are just moved around, resulting in very little dust being removed. To effectively remove the dust, the water droplets and dust particles must be the same size. Hence, the design of the spray head is of great importance. With preventative suppression, the size of the particle is less important.
Parker Conflow, a leader in the industry, works continuously with mining companies and equipment manufacturers to enhance products for preventative dust suppression. In one case, at CI Milpa in Colombia, a manufacturer of metallurgical coal, Parker Conflow engineers designed two dust suppression systems for a mine as well as a fire suppression system on a roadway.
“We are focused on continually improving the efficiency and safety of our production sites and the Parker Conflow systems are an important part of this. We chose to work with Parker Conflow, because of the company’s expertise in the manufacture and installation of dust and fire suppression systems and are very pleased with the result.”
— David Fernando Jaimes Mojica, CI Milpa
Preventive coal dust suppression is vital to ensuring the health and safety of workers and protecting mining equipment from costly downtime and failure. For over 60 years, Parker Conflow has been providing dust suppression, fire suppression and water control equipment and services that help protect workers in the coal mining industry worldwide.
After more than a century of experience serving our customers, Parker is often called to the table for the collaborations that help to solve the most complex engineering challenges. We help them bring their ideas to light. We are a trusted partner, working alongside our customers to enable technology breakthroughs that change the world for the better.
This blog was contributed by Gary Wain, product manager, Parker Conflow.