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Dust Control 

 
Author: Jack Caldwell

Summary

This review describes the control of dust in mines, including the use of water and proprietary chemicals to control the emanation of dust from mine roads, tailings impoundments, waste rock dumps, and other exposed surfaces. This review lists technology resources, websites, case histories, and consultants who work in and provide services to mines in the area of dust control.

INTRODUCTION

Growing up at a mine I was surrounded by talk of men who had lung disease. They breathed silica dust, my father would say as he puffed deep on yet another cigarette. And then as an afterthought he would add that maybe it was just the war that did them in.

When the wind blew, dust from the slimes dam beside our school deposited a thick yellow layer on our desks and we delighted in tracing patterns to reveal the ink-stained wood beneath.

I was fascinated by the large yellow trucks that ceaselessly traversed the dry roads of my first construction site: a new dam in the desert being built by a consortium of French and South African mining companies. The trucks sprayed muddy water from the Orange River on the dry roads. A cool calm emanated from the newly wet roads as we sought to slide and skid in the few muddy parts where the trucks dumped too much water. Alas, all too soon the sun dried the roads and the warm, clean-smelling dust returned. Somehow the music of Mahler was right in this setting and we played tapes of his symphonies day in and day out. Still today Mahler brings images of desert, dust, spray, and cool relief.

Enough of memories. Let us proceed to the modern world and the science and technology of mining-related dust control and the companies that would sell you their products to keep the dust down in your mine workings.

INFORMATION SOURCES

Everything you need to know about the nature of dust:

  • How to prevent its formation
  • Dust control systems
  • Collection and disposal of dust
  • The cost of dust control
  • Sampling air quality
  • Operation of dust control equipment
Wet underground dust collector cleaning air in a uranium mine

It's a superb free volume from the National Institute for Occupational Safety and Health (NIOSH): Dust Control Handbook for Minerals Processing. This volume saves me saying any more here about the topic.

Another comprehensive volume also available for free download is from NIOSH: Handbook for Dust Control in Mining. This volume further reduces the need for more on the background, technology, and control systems in this review. If you have not the time for its 132 pages, take a quick look at the NIOSH site on Dust Monitoring and Control Highlights.
You may also what to scan all the NIOSH dust publications (http://www.cdc.gov/niosh/mining/pubs/programareapubs9.htm). Here are a few to get you started:

The Foam Book is an odd website containing links to other sites and publications on dust control and other foam technologies. But mine roads is hardly its focus, so go there for general interest only.

Environment Australia has a series of e-books in their Best Practice Environmental Management in Mining series. Dust Control (pdf) is a gem. I liked its clarity, simplicity, good illustrations, and attention to detail; where else will you find a formula to estimate the dust load from an unpaved road?

A general site is Dust Control Info.com where you will find much general information. Another source of general dust technology information is the Western Mining Center Resource Center: These are three of their publications available for free download:


EFFICIENT DUST COLLECTION

After learning more about the basics of dust collection from Donaldson Australasia’s website, it reminded me of a summer job where a dust collector sure would have been handy. During that summer I worked with four other students hired to clean the boilers at our local power plant. This power plant provided electricity for the city of Estevan, Saskatchewan, Canada. Local lignite coal was used and every summer, the boilers were shut down to chip the impurities deposited from the burning of this coal. The heat and dust was stifling, even with dust masks, which is all they gave us. Even if these boilers still exist twenty years later, I’m sure health & safety laws have changed how these pipes are cleaned today.

As I understand, one of the primary maintenance costs for a dust collection system are the filter bags. This is what caught my attention about Donaldson’s Dalamatic dust collectors, which come standard with their Dura-Life long life filter bags.

According to Donaldson’s literature, their Dura-Life filter bags, provide as much as two to three times the life of standard bags. Increased bag life means less service requirements and disruption to equipment operation as well as a reduction in overall maintenance and bag costs. This is achieved in four key steps. Firstly, dust accumulates on the outer surface of the bag. Secondly, a blowpipe (jet tube) injects a burst of compressed air into the filter bag. Thirdly, airflow is briefly reversed which inflates the filter bag and dislodges the dust and fourthly, the dust cake falls into a collection hopper.

As shown in the pictures below, traditional polyester bags have been woven with a needling process that creates larger pores where dust can embed into the fabric, inhibiting cleaning and reducing bag life. Dura-Life bags are engineered with a unique hydroentanglement process that uses water to blend the fibres. This process provides more uniform material with smaller pores, resulting in better surface loading and better pulse cleaning and doubles the bag life. Tough EPA tests in North America have shown that Dura—Life bags have 30 % less emissions than other market options.

In any environment where dust is either a nuisance or a health hazard, and is a major part of a mining operation, Donaldson’s dust collection systems certainly deserves serious consideration to help reduce filter bag and maintenance costs.


DUST CALCULATIONS

The United States Environmental Protection Agency (EPA) e-publishes the definitive volume on how to calculate the quantity of dust from mine (and indeed all) unpaved roads, paved roads, construction sites, and ore stockpiles. Its title is AP 42, Chapter 13: Miscellaneous Sources. Thus if you need to estimate the amount of dust in the air for a new mine Environmental Impact Statement (pdf) or to compare the benefits of using gravel versus paved roads, this EPA volume provides the equations you should use.

Each section includes a brief description of the physics of the situation, the methodologies to analyze the situation, and most important the equations that give you the means to quantify how much dust your particular operations will cause. This is pretty much what was done in preparation of a paper whose abstract we can read at this link. I quote:

This paper presents PM[10] fugitive dust emission factors for a range of vehicles types and examines the influence of vehicle and wake characteristics on the strength of emissions from an unpaved road. Vertical profile measurements of mass concentration of the passing plumes were carried out using a series of 3 instrumented towers. PM[10] emission fluxes at each tower were calculated from knowledge of the vertical mass concentration profile, the ambient wind speed and direction, and the time the plume took to pass the towers. The emission factors showed a strong linear dependence on speed and vehicle weight. Emission factors (EF = grams of PM[10] emitted per vehicle kilometer traveled) ranged from approximately EF = 0.8 x (km h[-1]) for a light (~1200 kg) passenger car to EF = 48 x (km h[-1]) for large military vehicles (~18000 kg). In comparison to emission estimates derived using US EPA AP-42 methods the measured emission factors indicate larger than estimated contributions for speeds generally > 10-20 km h[-1] and for vehicle weights > 3000 kg. The size of a wake created by a vehicle was observed to be dependent on the size of the vehicle, increasing roughly linearly with vehicle height. Injection height of the dust plume is least important to long-range transport of PM[10] under unstable conditions and most important under stable atmospheric conditions.

A good summary powerpoint presentation is at this link. Another superb summary is at Wikipedia

As with all calculations there are caveats associated with the use of these equations, not the least the input parameters and the need for sensitivity analyses. Ultimately it might simply be easier to go into the field, wait for the wind to blow and to observe and measure the dust emissions.

California has a parallel method in the Technical Memorandum California Road Dust Scoping Report. They also have methods for the CEQA process and that delightful document a NEG DEC, i.e., Negative Declaration that in essence says there is nothing to worry about. Ontario, Canada has essentially adopted the EPA approach—but see the details at this link. Utah has a neat worksheet that incorporates the method for quarry and mining operations.

ROAD DUST CONTROL PRODUCT SUPPLIERS

Here is my personal survey of suppliers of products to control the dust on unpaved mine roads. Do they work any better than those yellow trucks filled with muddy river water?

CBR Plus LLC. I particularly liked their brochure, including the history of the product development in South Africa and the soil chemistry lesson that explains why the product works.

Mega Corp has the trucks that do what I am most familiar with, namely spray vast quantities of water on roads. How refreshing that was in the hot deserts of my first construction site.

Midwest Industrial Supply, Inc. has a well-stocked website with loads of information on and a wide range of products for conventional and other dust control methods in mining and other industries. I will go back to this site. They even have products for bike trails. They get my vote.

A water truck sprays water on broken rock to reduce dust.

Polo Citrus Australia has the prettiest website with "natural" dust control product for sale. Not quite what you expect from mining Australia.

Dust-A-Side (Pty) Ltd is a South African-based company specializing in total dust control management systems for the mining industry. They have dust binding products and construction and maintenance programs to help you control your mine's dust.

Dustkill is a mid-west distributor of 100 percent agriculturally derived oils that cure, stabilize, control, and provide dust abatement for mine haul roads.

Dust suppression. Water spray fitted to the cutter heads of roadheading machines reduce water consumption and provide explosion protection.

Road Material Stabilizers (Pty) Ltd. carries that fascinating South African (Pty) after its name. I once studied the law behind this but forget the details. Regardless, they have a full line of soil stabilizers, binders, dust suppression, and erosion control products.

RhinoSnot Soil Stabilizer. Who can resist a product with this name? They promote its use on mine tailings, landfills, and stockpile caps. And it is used in Afghanistan by the U.S. Marines. Actually the company is called Environmental Products & Applications, but that is ordinary!

The Martha Mine (pdf) case history of dust control is interesting as an example of full-scale mine application and use.

If you have more relevant information about similar products, please contact us gregf@infomine.com or jcaldwell@infomine.com and help us spread the word and keep the users of InfoMine informed & up-to-date.


OTHER SUPPLIERS

InfoMine Suppliers lists over 50 suppliers under the category Dust & Fume Control Equipment. I leave you to browse these at your leisure.

On InfoMine's EquipmentMine, there are 15 new and used dust collectors listed. A few of the top suppliers of used dust collectors on InfoMine are A.M. King and Machinery & Equipment Company, Inc.

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