Inhalable and respirable exposure to dust in coal mines has long been known to be dangerous to the health of coal mine workers. Both, coal dust and silica dust pose serious health threats to human health which are coal workers’ pneumoconiosis and silicosis respectively. These two diseases are fatal, hence best practices for dust control in coal mines is all about saving lives through dealing with dust at its source. Best practices for dust control vary according to the different types of coal mining operations. The deliberate intent should be to protect workers from exposure to respirable dust generated from the coal mining operations. Prevention is better than cure, but in this case, there is no cure to coal workers’ pneumoconiosis and silicosis therefore dust must be dealt with at its source.
In this article, dust control in coal mines is assessed based on best practices available in the following operations:
- Longwall mining operations.
- Continuous mining operations.
- Surface mines.
Dust control in longwall mining operations
Longwall workers can be exposed to harmful respirable dust from multiple dust generating sources, including the intake entry, belt entry, stageloader or crusher, shearer, and shield advance. It is key to address respirable dust concentrations at the face area in intake roadways which have a significant contribution to dust exposures of longwall face workers. Research shows that over the years, average air quantities on the longwall faces are higher than ever and higher air velocities in the intake entries may result in increased dust entrainment if proper controls are not applied. Activities that disturb dry dust on the intake roadways may contribute to dust reaching the longwall face. We now focus on longwall coal mining best practices for dust control in the specific dust generating areas:
Shearer: face ventilation, drum mounted water sprays, cutting drum bit maintenance, directional water sprays, keeping the headgate splitter arm parallel to the top of the shearer, shearer deflector plates, crescent sprays, lump breaker spray manifold and tailgate side sprays. Adding GRT: Activate UG into these water sprays makes the water work by changing its nature to attract and capture high speed, hydrophobic dusts like coal and silica.
Belt entry: belt maintenance, wetting the coal product during transport, belt cleaning during transport, belt cleaning by scraping and washing, use of rotary brush that cleans the conveying side of the belt and wetting of dry belts. GRT: Activate UG is also applicable for dust control at conveyor systems and in transit.
Stageloader or crusher: fully enclosing the stageloader/crusher, wetting the coal in the crusher and stageloader area, using scrubber technology in the stageloader/crusher area and using a high-pressure water-powered scrubber. For process and production optimization, GRT Activate can be added to water used for dust control in material crushing achieving binding of finest dust particles that would otherwise bounce of water sprays alone.
Shield: canopy mounted spray systems, shield sprays on the underside of the canopy, air dilution and unidirectional cutting sequence.
Intake roadways: limit support activities during production shifts, apply water or hydroscopic compounds to control road haulage dust and use of surfactants. GRT Haul-Loc is a specially formulated liquid polymer added to watering trucks. In addition to binding fugitive dust particles, GRT Haul-Loc reduces water required for haul road dust suppression.
Dust control in continuous mining operations
The largest source of inhalable and respirable dust at continuous mining operations are generated from two sources which are the continuous mining machine and the roof bolter. The continuous miner and the roof bolter operators are often exposed to elevated silica levels because of cutting and drilling into the rock. Dust generated by the continuous miner has the potential to expose the miner operator and anyone working downwind of the active mining. Water spray systems, flooded-bed scrubbers and face ventilation are used as best practice methods for dust control in continuous mining operations. Continuous mining dust control can be achieved using the following best practice techniques:
Water spray systems: hollow-cone for small to medium droplet sizes, full-cone for medium to large droplet sizes, solid-stream for uniformity in wetting of the material to be cut, flat-fan for small to medium droplet sizes in narrow and enclosed spaces and air-atomizing for fine mist droplet sizes which are the smallest droplets of all sprays. GRT: Activate UG is an ionically charged product that super-activates water enabling effective dust suppression in continuous mining operations.
Flood-bed scrubbers: capture dust from the cutting face through the ductwork on the miner, and pass through a filter panel that is wetted with water sprays or use of surfactants. To improve the efficiency of the scrubber the best practice methods include scrubber maintenance, airflow measurement and adjustment of the filter panel thickness to specifications that suit quantity of airflow through the scrubber.
Face ventilation: blowing face ventilation in which intake air is delivered to the face of the working entry by blowing it from behind tubing. Exhausting face ventilation in which intake air is delivered to the face in the working entry.
Dust control for roof bolters is achieved using these 12 best practices methods: (1) maintaining the dust collector system, (2) cleaning the dust box (3) using dust collector bags (4) removing and replacing the canister filter (5) cleaning and discharge side of the collector (6) installing a sock on precleaners (7) using dust hog bit (8) positioning to avoid working downwind of the continuous miner (9) wet drilling or mist drilling (10) using a canopy air curtain (11) routing miner-generated dust to the return and (12) working of the bolter.
(Note: Point 9 “wet drilling” can be greatly improved by the addition of GRT: ACTIVATE UG in the water used.)
Dust control in surface/open-cut mines
Surface mining operations present dynamic and highly variable silica dust sources. The bulk of the dust generated at surface mines is produced by mobile earth-moving equipment such as drills, bulldozers, trucks, and front-end loaders excavating silica-bearing rock and minerals. Drill dust collection systems, enclosed cab filtration systems, controlling dust on unpaved haul roads and dust control at the primary hopper dump are best practice techniques used for dust control in surface mines. Silica dust is carcinogenic, it causes silicosis, and it kills. Exposure to airborne inhalable and respirable crystalline silica leads to fatal lung disease. There is no small amount of silica dust that must be overlooked as acceptable because cumulatively that results in silicosis with its severity varying from acute, accelerated and chronic silicosis. The best practice methods for dust control in surface mines are described more in-depth as follows:
Drill dust collection systems: drill dust is generated by compressed air flushing the drill cuttings from the hole. Dry or water-based dust collection systems are used to control drill dust. For dry dust collector systems, a tight drill deck shroud enclosure with the ground must be maintained. The collector-to-bailing airflow ratio of at least 3:1 is key which should be coupled with a good drill stem seal with the drill table and maintaining the dust collector per manufacturers specifications. For wet dust suppression, some best practice techniques include the addition of small amounts of water into the balling air to reduce visible dust and minimizing water flow to a rolling cutter bit to increase bit life. GRT: DC Binder prevents dust generation from the hazardous piles of drill cuttings produced by drill and blast activities. GRT: 12X drill transforms drill water so it saturates and captures the fine, hazardous dust drilling can generate, preventing it from becoming an airborne hazard.
Enclosed cab filtration systems: one of the main engineering controls for reducing mobile equipment operators’ exposure to airborne dust at surface mines. Enclosed cabs with heating, ventilation and air conditioning (HVAC) systems are integrated into the drills and mobile equipment to protect the operator from the outside environment. It is important to ensure good cab enclosure integrity to achieve positive pressurization against wind penetration into the enclosure. Use high-efficiency respirable dust filters on the intake air supply into the cab and use an efficient respirable dust recirculation filter. Minimize dust sources in the cab and keep doors closed during equipment operation.
Haul road dust control: off-road haul trucks used in surface mining contribute most of the total dust emissions at a mine site. Treatment of unpaved road surfaces using hygroscopic salts, surfactants, soil cements and polymers can be used for haul road dust control. Increase the distance between vehicles travelling the haul for road dust dissipation and dilution which provides opportunity to use administrative and mine planning control to reduce work dust exposure. GRT: Haul-Loc is effective for dust suppression on unsealed roads plus provides benefits in terms of ride-ability and decreased maintenance costs.
Primary hopper dump dust control: Mined product is normally loaded into the haul trucks from the surface mine pit and driven to the primary crusher location. The product is either dumped directly from the haul truck into the primary hopper feeding a crusher or dumped into a stockpile. Best practice for dust control include enclosing the primary hopper dump, use of water sprays to suppress the dust in the enclosure and dust liberated due to rollback under the dumping mechanism of the dump vehicle. The use of GRT Activate in water sprays (permanently mounted or using mobile fog cannons) enables effective dust suppression and capture in this operation.
Working with you to deliver solutions
The severity of lung diseases in coal mining is often understated and seldom would you see news headlines on them. GRT commits to awareness through highlighting relatable best practice examples in driving advocacy for more action towards dealing with dust at its source. There is no better commitment than elimination of dust at its source, because the aftermath of exposure to dust creates a prolonged cycle of lung disease associated deaths and dents all the efforts that only focus on limiting exposure to dust instead of eliminating it at its source. Are you dealing with dust at its source? Do you have a dust management plan that is achieving its intended outcome? If you are struggling, GRT has got your back. Speak to us.
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