Quarry Dust: 6 Ways Dust Suppression Can Help Improve Safety

Quarry Dust 6 Ways Dust Suppression Can Help Improve Safety
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Operators and workers in quarries generally consider dust an unavoidable feature of the process. Although most sites take considerable steps to try to mitigate quarry dust emissions, mostly using water, the many stages involved in the extraction and processing of raw materials and aggregate can make the effort seem overwhelming.

Many studies researching the effects of dust on personnel have shown that even short-term exposure to substances like Respirable Crystalline Silica (RCS) can cause serious chronic health consequences later in life. Regulators, insurance companies and workers’ advocacy groups are changing attitudes and policies toward workplace air quality. As communities expand and encroach on quarry operations, political pressure can change local environmental policies and permitting rules.

An example of this is in South Dakota in 2023.[1] Even though it is one of the least populated regions in the United States, residents near the local quarry are blocking new permits and expansion plans, citing dust as a main concern. The proposed quarry would extract 30,000 tons of rock per year. Owned by a large commercial construction company, operators said a substantial amount of time at the county meetings was spent discussing dust. Operators point out that the quarry must keep at least 10,000 gallons of water on the site at all times to help keep the dust down. While operators have met all requirements and ordinances, the potential result of this community action will come down to a public vote, which could block the entire project and force local businesses to look elsewhere for a limestone supplier.

The U.S. Mining Safety and Health Administration (MSHA), the Occupational Safety and Health Administration (OSHA), and the Environmental Protection Agency (EPA) have all increased scrutiny in relation to RCS and other hazardous particulates emitted by quarry operations. Investigations, fines and Elevated Enforcement Actions (EEAs) -- which can involve temporary shutdowns to implement dust control -- have become more prevalent.[2]

MSHA Mine Elevated Enforcement Action Graph BossTek

Industrial mist cannons are being increasingly recognized as the most effective and environmentally friendly method of suppressing airborne dust emissions in quarries. Operators are becoming aware of the ease of use and the long-term economic benefits of implementing atomized mist across several stages of their operations.

Watch how Atomized Mist works above!

QUARRY DUST AND EXCESSIVE RUNOFF

In the past, hoses and sprinklers were the standard of quarry dust control. Workers were assigned to hose down the working face or storage piles to reduce dust emissions. However, along with not preventing airborne RCS due to droplet size (as demonstrated in the video), hoses and sprinklers have several issues associated with them.

Wetting can suppress surface dust, but all the particles underneath the damp top layer will be released as soon as the material is disrupted. Further, quarries that employ pressurized water from hoses and sprinklers for dust management can use up to 500 gallons per minute (GPM) per unit for dust control. When spread across many working faces or storage piles, that translates to thousands of GPMs.  In fact, some quarries use enough water to fill an Olympic sized swimming pool roughly every week. Volumes like that can greatly increase the amount of standing water, mud, and erosion. This can overburden runoff controls and lead to a higher chance of extreme mudflow during storm events. Due to excessive pooling at the quarry’s base, pumps are employed more often, which raises the cost of operation.

Workers assigned to the task of holding the hoses are generally just outside of the drop zone and nearby working machinery. It puts them in the exposure area for dust and could be a serious workplace safety hazard if the area becomes muddy and slick. Along with increasing labor costs, manual dust control methods can also raise the chance of workplace injuries.

DustBoss DB-100 Effective Suppresses Dust During Blasting at Quarries

Atomized mist cannons are autonomous, providing both surface suppression and airborne dust control, while using only a fraction of the water. The largest DustBoss® cannon, the DB-100, offers up to five football fields of coverage using only 39 GPM. Since atomized mist is so light, propelled by a high-powered industrial fan rather than high water pressure, it travels on ambient air currents and settles lightly on dusty surfaces, delivering more consistent distribution of droplets for better surface suppression, with less pooling and virtually no runoff. Workers simply set the units and walk away, meaning labor for dust control is drastically reduced, which lowers the cost of operation and raises the return on investment (ROI) per DustBoss unit.

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DUST DURING EXTRACTION

From blasting to digging, disruption of the quarry’s working face creates a massive amount of dust. Operators use various methods of extraction, based on the application and the geological features of the site. Some use explosives more than others, but at some stage, all employ large machinery such as excavators, dump trucks, and front loaders, while handling material throughout the extraction process. There are mist cannons for each of these methods.

Dust emissions from quarry blasting can travel high into the atmosphere, carried by air currents that may be monitored by regulators miles beyond the site line. The DustBoss DB-100 can be placed downwind with a 0-50º vertical throw and a 70º horizontal oscillation range to fill the blast area with mist for a few minutes before detonation. This introduces millions of droplets into the immediate area and in the path of the airborne particulates. Once the blast releases the particulates, they immediately encounter an army of droplets preventing them from lifting into upper air currents and spreading long distances. Operators often place multiple DB-100 cannons near the blast site, allowing the plume to engulf the dust released during the blast and as the material settles.

Excavator dust can cause fugitive emissions from a very specific point on the workface. Although the DustBoss DB-60 Surge has the option to create a 60-meter cone of mist like classic atomized mist cannons, its versatility allows it to be directed at specific operations or set to oscillate for wider area coverage. For high wind locations, a specially designed pressurized center spray nozzle powered by a booster pump provides focused jet stream suppression.

Quarry Dust Emissions Can Occur During Material Loading

MATERIAL LOADING

When front loaders dump their cargo into waiting trucks, large dust plumes sweep away with the wind. The trucks come and go, taking the material with them to the next production phase, but dust from material transfers can be mitigated using atomized mist.

A single DB-60 mist cannon can typically cover a workface and loading area if properly located. The easy-to-use touch screen display allows operators to set the optional oscillation from 0-359º to offer more than 125,000 square feet of coverage. On days of normal conditions with limited wind, it effectively controls airborne particles and helps keep ground-level dust from migrating. In mild windy conditions, aiming the machine downwind takes advantage of the breeze to enhance droplet travel even beyond its rated 200-foot range, covering operations at greater distances.

CONTROLLING DUST AT HOPPERS 

In many operations, quarried material will be transferred onto a conveyor system, often requiring a hopper. Dump trucks or front loaders dropping raw material into a hopper or transfer chute causes dust emissions. Depending on the length of the drop, turbulence from the impact at the bottom causes dust to backflow at a high velocity up the chute and out of the exit point. This leads to fine particulates being lifted out of the cargo flow and into the atmosphere.

Misting heads for hoppers like the DB-M Mini are strategically placed around the edge of the container to help prevent emissions from leaving the opening, because dusty material is loaded into a mist-filled environment. Movable misting heads are the alternative to misting bars, which are mounted in a fixed position across the inside of the container and may be damaged by loading. The breach of a misting bar can also create a deluge of water to spill down the shaft. Requiring no power to operate, each DB-M is placed individually out of the trajectory of the material flow and features adjustable heads that can be directed according to changing materials or conditions.

Quarry Dust Control for Crushers Mills Hoppers Conveyors

CRUSHERS & MILLS DUST MANAGEMENT

Low air quality around crushers and mills is a common complaint from quarry workers. Those are expensive pieces of equipment that operators often protect in a covered enclosure or warehouse. Regardless of ventilation, these enclosures can entrap particulates, causing lower air quality and possible workplace violations.

Although some crushers and mills come with internal dust suppression, many operators have found the OEM dust solutions to be inadequate or specified for minimum duty and not able to live up to production demands. The reason is that many of these units only account for dust from the crushing and milling processes and don’t address emissions caused by entering or leaving the machines, such as loading, screening, or conveyor transfers.

DB-M misting heads control dust from crushers and mills at the entry and exit points. For issues that require wider area coverage, the DustBoss DB-10 is designed for enclosed spaces. With a 30-foot throw range, the small misting cannon offers directed dust control for a specific problem area around a piece of equipment or material transfer. Roughly the size of a baby carriage on a specially designed wheeled dolly, with a 0-50º vertical adjustment, it can be easily moved and set up by a single worker anywhere on the site, making it extremely versatile for dust suppression in specific problem areas.

Dust Suppression for Crusher at Limestone Quarry

CONVEYOR DUST SUPPRESSION

Belt and chain conveyors are common in quarry bulk handling. Chain conveyors are more common for larger rocks due to the weight and demands on the system, whereas aggregate and meal are more conducive to belt conveyors. However, both produce dust in different ways.

Due to the weight and oddly shaped raw material, chain conveyors employ metal paddles that push raw material along its path. These systems are often enclosed but require DB-M misting heads at the discharge zone, generally the primary escape point for dust. Without adequate suppression, the transfer can experience a backflow of dust-laden air, but the misting heads help contain the dust within the discharge zone.

Belt conveyors benefit from DB-M misting heads at the loading zone, where the impact of material hitting the moving conveyor belt can create a tremendous amount of dust. If the bulk handlers have enclosed the loading and discharge zones to control dust emissions, then the exit points of these enclosures are excellent candidates for misting heads for several reasons:

  • Even with the presence of dust curtains, the exit point can experience emissions.
  • Surface suppression on the outside of the pile helps mitigate emissions along the conveyor path.
  • Cargo separates at discharge and releases dust, so mist suppression at the point of discharge controls emissions.
DB-M Mini for Dust Suppression at Conveyor Transfer Points

STORAGE AND STOCKPILES

Material can be piled and stored at many points in the quarrying process, but the main storage area usually houses the tall piles waiting for rail, truck, or barge transport. Raw material is commonly stored in open-air mounds that rise as high as 60 feet. Storage piles shed dust throughout the discharge process and from wind or loading material for transport. There are solutions to mitigate and control emissions here, as well.

Piling is generally done with stacker conveyors that can be moved from area to area as the product is turned over. As material drops from the conveyor, it separates and becomes vulnerable to even the slightest ambient air current. Once it hits the top of the pile, the impact emits more dust. Stacker conveyor dust from discharge to the top of the pile can be controlled by the DustBoss DB-Ring. It creates a curtain of atomized mist around the cargo stream, locking in fugitive particulates, as well as offering surface suppression on the top of the pile to control impact emissions.

Conveyor Transfer Points and Discharge Dust Can Be Contained with DustBoss

On windy days, storage piles can shed dust high into the atmosphere, allowing it to travel toward neighbors and nearby communities. Raising mist cannons enough to throw atomized mist over the piles helps control dust from all sides while compensating for shifts in wind direction and weather conditions. Providing even distribution during the turnover of material, tower-mounted DustBoss units offer bulk storage dust control by capturing fugitive particulates at the point of emission and ensuring they don’t leave the designated storage zone or site line. This reduces potential fines and complaints that lead to violations.

DustBoss DB-60 towers for fly ash stockpile dust control

QUARRY DUST SOLUTIONS

From the aspects of workplace safety and environmental impact, quarry operations have changed significantly just in the last few decades. Older methods of dust suppression such as hoses and sprinklers are not holding up to new regulations. The scrutiny of local agencies and communities is making the need for a more comprehensive and effective dust control plan essential. Many quarry operators have found that identifying problem areas and utilizing appropriate misting options can greatly improve air quality and control emissions for better compliance and a safer workplace.

Our experts work closely with on-site environmental supervisors and engineers to help produce comprehensive dust management plans for quarries. For a full assessment of your quarry, Contact Us today.

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