CA-Black-Transp

Tackling a Gritty Problem


Controlling dust emissions from haul roads, crushers, stockpiles and tailings impoundments can be costly — or inexpensive. Coal Age looks at some of the options.
Australian Diversified Engineering claims that its ECO Spray system can deliver the optimum volume of water onto haul roads, consistent with current conditions.
Australian Diversified Engineering claims that its ECO Spray system can deliver the optimum volume of water onto haul roads, consistent with current conditions.

Without appropriate control measures in place, dust can be all-pervasive. The days when society was prepared to tolerate fugitive emissions from industrial plants of any description are long gone, and there is also a better understanding of the damage that exposure to dust can do to people and machinery alike.

There are essentially two threads to the dust story: internal and external. Within a mine, quarry or mineral processing plant, the principal concerns revolve around personal health, maintenance and — in dry locations in particular — visibility issues. Beyond the mine boundaries, the nuisance caused by fugitive dust can have a major effect on relations between the operator and local communities, with problems likely to increase further if the dust itself is not completely inert.

 
Dust Control Basics

Operations typically seek to control dust emissions by either applying an agent — usually water — or enclosing the source. Both options cost money to implement, but as Dr. Mark Kestner, president of National Environmental Service Co. (NESCO), pointed out, there are other ways of addressing the problem that need not cost a penny. “One of the most effective tools that you can use to control dust is good operating practice” is his watchword.

When it comes to haulage, Kestner said, slow the trucks down, especially if there is likely to be a delay before they can unload at a crusher. Slower trucks generate less dust. Reduce the height of stockpiles — lower piles are less affected by the wind. Choke-feed primary crushers — this will generate less dust than a crusher that is handling fluctuating loads.

And, most importantly of all, he added, dust control is everybody’s business on-site, with a strong dust-control culture essential right through an operation’s management and operator hierarchy. “Good operating practice means training operators to take personal responsibility for minimizing dust,” Kestner stated. “Training them to do so is barely a blip in the budget and can have a big payoff.

“Do the least expensive things first,” he added. “You’ll find that the savings go a long way in reducing the costs of more expensive controls like chemical suppressants and dry collection systems.”

Aside from stating the obvious, NESCO’s business includes the supply of DustPro dust-control spray systems. Operating at 200 psi, these produce a highly atomized mist to suppress airborne dust and minimize water addition rates. DustPro systems are electronically controlled, can be completely automated and winterized for use in cold climates. For metals mines, the duplex version is designed with two pumps, one operational and one spare that can kick in immediately if a maintenance issue arises, thereby avoiding any production downtime.

 
The Benefits of Cartridge Collectors

According to Camfil Air Pollution Control (Camfil APC), its Farr Gold Series dust and fume collector combine enhanced performance with ease of service and reliability for a cleaner workplace. Applications include primary, secondary and tertiary crushing, high-pressure grinding roll crushers, screening plants, conveyor transfer points, stockpiles and ore-storage bins, electrical switchgear and control rooms, and assay labs.

The Farr Gold Series dust collector has a rugged, compact, modular design that optimizes field flexibility and integrates well with conveyor bin vents, the company noted. They have a much smaller footprint than a conventional baghouse and operate at a lower pressure drop, leading to lower energy costs. The pleated filters are mounted vertically inside the collector, eliminating the problems of dust blinding and premature failure that sometimes occur with horizontally installed filters.

In addition, Camfil reported that its HemiPleat high-efficiency cartridges and a cross-flow inlet design allow Farr Gold Series collectors to handle very heavy loads that horizontal cartridges cannot.

Camfil pointed out that although its filter cartridges are more expensive initially than conventional baghouse filter bags, they last much longer and fewer of them are needed. Hence, downtime for maintenance is reduced. In consequence, total annual installation and operating costs can be markedly lower.

According to Camfil, filter change-out with its Farr Gold Series dust collectors is simple and easy.
According to Camfil, filter change-out with its Farr Gold Series dust collectors is simple and easy.

Geometrica’s Domes

With facilities in Houston, Texas, and Monterrey, Mexico, Geometrica has been constructing its domes and space-frame structures since 1992. The company noted that these offer an alternative approach to dust control, particularly for applications such as stockpiles.

The company pointed out that traditional building methods are often not practical or cost-effective, especially in remote and rugged regions. Steep slopes or corrosive saltwater environments require more than conventional building systems, Geometrica said, with its system offering lightweight, strong domes and barrel vaults. Structures that can span up to 300 m without internal columns, these can also be built over and around irregular shapes and live operations.

Geometrica cited the example of the Freedome that it supplied to Minera Coemin to cover the crushing and conveying equipment at its Carola mine in Chile, as a means of preventing dust emissions. The challenge at this particular site was that the crushing plant had been expanded several times, resulting in a highly irregular footprint that needed covering.

The company’s solution was to design a freestyle dome covering some 5,000 m2 while bridging existing buildings without needing modifications to the crushing and screening plant. The heart-shaped result included 90-m spans in the principal directions.

Dome construction progressed upward, with the partly built dome supporting its own weight and that of the construction crews. No scaffolding was needed, nor was there any operating downtime. Cladding consisted of corrugated metal sheets with a polyester finish.

 

Carefully Measured Control

Australian Diversified Engineering (ADE) claims to offer the only system in the world that can deliver consistent, measurable water coverage for dust suppression on haul roads. This, the company said, has the potential to save millions of dollars and billions of liters of water every year, while also increasing truck productivity.

ADE specializes in water truck spray systems for haul-road dust suppression. This is a precise art — if too much water is sprayed, the road can become slippery, while with too little water, dust can obscure the road. The company’s Electronically Controlled Operating (ECO) Spray system uses technology to measure the truck’s ground speed, the road surface material, the road geometry and other factors to calculate and supply the ideal amount of water to the road.

ADE suggested that on sites where water typically costs around A$2,000 per million liters ($1,500), using the ECO system, a fleet of five trucks operating 18 hours per day can save 4 million liters of water per day, or 1.4 billion liters per year — a monetary savings of A$2.9 million (more than $2 million).

Three stages of Geometrica’s Zaldívar project: the problem dome construction final dust containment
 
 
Lignins and Latex

With its headquarters in Ohio, Zinkan Enterprises offers ranges of dust-control products that can address emissions in underground and surface mining, stockpiles, rail transport and road surfaces.

Zinkan’s dust control products include its MineReady range for underground and surface applications, PileReady for stockpiles, RailReady for transport, and DustReady for haul roads. For example, RailReady-50 is a water- and latex-based sealing agent used for stabilizing materials such as coal to reduce losses during transit or storage. It penetrates the material surfaces, forming a tough water-resistant crust. A winterized version is also available.

For haul roads, DustReady-110 is a natural byproduct from trees, made primarily of lignin, the natural polymer that binds tree fibers together. Applied annually to roadways and commercial yards to stabilize and improve the quality of the road surfaces and to control dust, it is non-corrosive. DustReady-110 is applied as a liquid and dries to a hard durable surface that controls dust and increases the load-bearing capacity. As a binder, it reduces gravel losses and grading requirements, thus lowering overall road maintenance costs, the company stated.

 
The crust formed on a coal stockpile treated with Zinkan’s PileReady, a week after the sprayed application.

Roadside Sign Dust Removal

While dust problems are often considered in terms of airborne material or bulky accumulations, the effect of dust on road signs and haulage markers is often overlooked. Spinflector Industries believes it may have a solution to what it explains can be a long-term, high-cost challenge.

The Spinflector itself is a wind-powered device that automatically cleans the reflectors on the delineator posts used to mark haulage routes and other features in surface mines. With a big mine often using 10,000-15,000 individual marker posts, manually cleaning dust and grime from the reflectors can involve teams of workers traveling almost weekly along major thoroughfares, creating safety issues, loss of productivity and additional labor costs.

The Spinflector is designed to fit on a 50-mm PVC delineator post and contains a series of brushes to clean dust and grime from reflectors. The device has a built-in wind vane to power the brushes, with the company claiming it only needs to rotate half a dozen times in a 48-hour period to take off the layer of dust and be effective.

According to Spinflector Industries, it has trialed the system at an iron ore mine in South Australia for five months without incident, and without the need for any manual cleaning of roadside reflectors.

The Spinflector is designed to clean haulage marker reflectors automatically.

By Donna Schmidt, Field Editor

Building upon the features of an original design and incorporating feedback from its user community, the National Institute for Occupational Safety and Health (NIOSH) recently unveiled Version 2.0 of the Enhanced Video Analysis of Dust Exposures (EVADE) software program, usable across the metal/nonmetal mining spectrum and, hopefully, increasingly more for coal at some point in the future.

EVADE, which merges video files and logged data files and allows users to view them to aid in identifying exposure sources, has been completely rewritten from the ground up. The beta version has been used successfully, so the final software version is mere months from receiving approval.

“Based on the success of EVADE 1.0 and feedback…the function and capabilities have been expanded to make a more generic and more powerful tool,” according to NIOSH researchers Andy Cecala and Emily Haas. It was historically able to be used with the agency’s Helmet-CAM assessment tool, which uses a miner-worn video camera to provide a visual record of activities and location and paired with a real-time respirable dust monitor, a pairing that will continue with EVADE 2.0. (Editor’s note: The Helmet-CAM is currently not permissible for underground coal applications.)

Turning a page from the days of one-dimensional dust sampling that took days and often longer to receive results, the EVADE software was first developed by the NIOSH team in Pittsburgh several years ago to merge dust data with visuals in real time, monitoring both simultaneously and combining them into a format that was user friendly.

The technology was first put to the test by researchers at a silica sand processing facility, after which function and layout modifications were made to the elements of the package and an initial design for EVADE was born.

“This initial field testing also provided insight into other means to allow the miners to comfortably wear the dust monitor and video component of the Helmet-CAM technology while performing their work in an uninhibited manner,” the two said following the initial testing, which was followed by additional field tests.

Helmet-CAM, meanwhile, developed to be rugged but yet simple and inexpensive to use, includes a lightweight video camera, and a dust monitor that provided instantaneous results. The systems underpinnings are contained in a light backpack that can be easily worn by the miner.

NIOSH tested and decided upon a point-of-view, or POV, camera for which to record activities; the video lens attaches to a miner’s hard hat with a simple flashlight clip and an 18-in.-long cable connects the lens with the recorder. That component records two files, with .AVI and .THM extensions, both of which are used by for evaluation by the EVADE software.

Cecala and has noted that, because the element of real-time data was vital to the system, it selected the Thermo Scientific pDR-1500 monitor for the testing of the Helmet-CAM. As it was a rather new instrument, the research group put it through testing at the Pittsburgh NIOSH campus to ensure it would collect and produce results in a method similar to both federal compliance testing and in-house gravimetric dust sampling.

“This instrument was attractive to NIOSH researchers because it is an active sampler using an internal pump to collect the sample,” Cecala and Haas said. “[It] was slightly modified so that a 3-ft (0.91-meter) section of conductive tubing could be used to connect to the 10-mm Dorr-Oliver cyclone, which is the normal pre-classifier device used for respirable dust sampling in the metal/nonmetal mining industry. The pDR-1500 was also set to a 1.7-L/min flow rate, which is the required flow rate as established by the American Conference of Governmental Industrial Hygienists (ACGIH) for the metal/nonmetal industry.”

The newest version, EVADE 2.0, despite its pending approval of the finalized software, is fully functional; in fact, the researchers said that the beta version was made available to the industry early because of the high level of interest during in-mine testing.

The newest version provides notably more than just dust exposure levels and can now be used with any of a site’s logged data streams. A useful tool for mine management across all types of mining, the activities and locations recorded along with that logged data can be shared among staff members and used as needed in training and task analyses. Hazard recognition for such things as noise levels, diesel particulate exposure and chemical exposure monitoring are now possible, and tracking of those elements can be done at the same time as dust exposure monitoring.

EVADE 2.0 also now has multiple channels for both video and data, all of which can be compiled into a single project and viewable as a single project inside the software component of the system, giving a mine or safety manager seamless and comprehensive access.

The windowing interface of the EVADE 2.0 has become more advanced, with all playback channels, editors and bookmarks available as “drag and drop” items. “This enables them to be stacked or grouped in any configuration and docked or undocked from the main program window. This is especially beneficial for large multichannel projects and computers with multiple monitors,” the researchers said.

A redesigned project editor allows for a visual reference, and each separate imported video can be packaged and then sent to other computers for viewing. The basic data functions including max, min, mean and derivative can be applied to any logged data channel.

Custom data import and analyses functions can be created via a custom plug-in in a specific folder in EVADE 2.0. Once there, the folder is immediately available; the program will no longer needs to be recompiled before the file can be accessed and used.

Both noted that, at this time, the application of the system for surface coal is available but has been tested on a limited basis. However, with the success it has had in metal/nonmetal testing and use, future use in underground coal is not out of the realm of possibility. Additionally, tying the camera to a personal dust monitor (PDM) could also be a potential, though no work is currently being undertaken to combine the technologies. The biggest obstacle will be the future approval of the camera technology for use underground.

The beta version of EVADE 2.0. While limited in its use in coal today, the program could be applied at a greater level in the future.
The beta version of EVADE 2.0. While limited in its use in coal today, the program could be applied at a greater level in the future.