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This review provides a new and comprehensive summary on studying colloidal interactions encountered in mineral processing with representative examples for critical information, which are of great scientific and practical importance. Colloidal interactions play a vital role in mineral processing, including grinding, physical separation (particularly flotation), dewatering and tailings management (Fig. 1). Despite great energy input in comminution to liberate valuables from gangues, hetero-coagulation between valuables and gangues would prevent the separation of valuables from gangues. On the other hand, selective coagulation/flocculation to increase the size of desired fine particles could enhance physical separation and dewatering, while dispersion is needed for fine grinding. The importance of colloidal interactions is becoming increasingly significant as we process ever more finely disseminated low-grade ores as a result of inevitable depletion of high-grade ore deposits. To control the state of colloidal dispersions by creating favorable conditions, it is of paramount importance to study colloidal interactions in a relevant system and understand underlying mechanisms. 

By Mike Preston

Attrition scrubbers may not be glamorous, but they are an important and sometimes neglected step in mineral processing. Optimal attritioning will significantly improve the results and efficiencies of subsequent processing steps and can lead to reduced costs and improved product yields. Why is attrition scrubbing used? Attrition means to wear away a surface, typically by friction or abrasion. An attrition scrubber does exactly this, using impellers to force particles against each other, causing intense scrubbing, grinding, abrasion and polishing. This process is not a new concept. It has long been used in the glass industry to remove surface contaminants from silica. But it is also widely used in many areas of mineral processing and other applications including soil remediation and plastics recycling. In mineral separation, for example, the scrubbers help improve yield and efficiencies by preparing feed materials for downstream processes such as flotation, magnetic or electrostatic separation. Inefficient scrubbing can lead to coatings remaining on valuable minerals and decreased yields, as the covered minerals cannot be processed efficiently or are mistaken as waste contaminates and removed. In the example of flotation separation, pre-flotation conditioning uses attrition scrubbers to provide better recovery of minerals while using fewer chemicals. If surface contaminants remain on the mineral, yield is reduced, as the unwanted coating acts as a barrier to the reactants, which make it unfloatable and, therefore, unrecoverable.

Oct 1, 2013

By Ehsan Moradabadi, Debra F. Laefer

"To more rigorously address tunneling risks to above-ground structures, vulnerability evaluation of all structures along a tunnel route is required. This multi-block area along the route can be considered a district. To fully assess each structure within a tunnel’s zone of influence, a multi-block or district-level model may provide new insights as to risk evaluation and mitigation strategies. However populating such a model with the existing geometry of the built environment poses a major challenge as measured drawings are not readily available for all structures along a tunnel’s route. Cost-effective population of such a model could arguably involve remote sensing data in the form of laser scanning or photogramme-try. However even for unreinforced masonry structures, where external, above-ground geometries can be captured, without a prohibitively expensive building-by-building, in person survey many factors would remain unknown. To consider these uncertainties in an automatic way, a performance assess-ment framework is proposed. Such a framework allows a more rigorous, initial, risk quantification than is currently possible within the simple empirical models generally being used in industry when tunneling risk is initially assessed. This paper introduces (within the allowable space limits of this format) consider-ations for auto-population and application of a district-level, tunnel-risk screening tool. INTRODUCTION Challenging topography, intense urbanization and infrastructure development, combined with limited land availability and a growing awareness of environmental issues have lead to increasing usage of un-derground spaces to control aboveground traffic and provide essential services in metropolitan areas. Tunneling, however, is not without its own risks, especially with respect to aboveground structures whether it be widespread minor damage (Burland et al. 2001) or the more notable, although less fre-quent, large-scale collapses such as the 2003 Shanghai (Allianz 2015) or 2004 Singapore (Magnus et al. 2005) events."

Jan 1, 2016

By G. H. Schnakenberg

In 1986, the US Bureau of Mines (USBM) embarked on a major research effort to develop technology that could substantially reduce worker exposure to face hazards by simply relocating the equipment operators to an area of relative safety. This reduced-exposure mining system (REMS) research effort enhances the USBM's ongoing health and safety efforts aimed at reducing and controlling dust and noise and reducing accidents through training and better mining practices. This paper reports on the progress made on the developing research and demonstrates the technologies required for the computer-assisted teleremote operation of continuous mining machines, haulage systems and roof bolting machines.

Jan 1, 1997

By Liming Yuan, A. C. Smith

Barometric pressure changes affect air density, leading to change in the mass of the gas in the gob. When the barometric pressure decreases, the volume of gas in the gob expands, while the volume of gas contracts when the barometric pressure increases, a process which causes the gob to “breathe” out and in. Although the concept of gob “breathing” is simple, its effect on spontaneous heating of coal in the gob area is not clear. In this study, computational fluid dynamic (CFD) simulations were conducted to model the spontaneous heating of coal in the longwall gob area under measured barometric pressure changes. A single longwall panel using a bleederless ventilation system was simulated. If there is no barometric pressure change, the intake airflow rate is equal to the return airflow rate. When the barometric pressure changes, these two airflow rates are no longer equal, and the difference between the two airflow rates represents the airflow rate the gob breathes in and out. The effect of inflow and outflow of gas on the potential spontaneous heating in the gob was investigated using the CFD model developed in our previous study. The effect of barometric pressure changes on the spontaneous heating was found to be dependent on the gob permeability and the coal oxidation rate. The effect of barometric pressure changes on oxygen concentrations in the gob was also examined.

Jan 1, 2010

By H. Kimura

A new technology for ironmaking based on direct gaseous reduction of iron ore concentrate is under development. The process is based on the flash reduction of the concentrate particles in a gaseous reducing agent, such as hydrogen, natural gas, a reducing gas generated by partial combustion of coal, or a combination thereof. This technology is expected to drastically lower CO2 emission and reduce energy consumption by about 38% of the blast furnace requirements. The energy savings are possible largely due to the elimination of pelletization and cokemaking. Process design and simulation using hydrogen as the reductant for iron ore concentrate have been performed. A process flow sheet composed of a flash reactor, heat recovery system, water removal system for purifying recycled hydrogen, and all connecting streams was evaluated using the METSIM software. Ironmaking using two reactors was also designed and simulated, which could reduce the total required amount of hydrogen although it would increase the complexity of the flow sheet and operation.

Jan 1, 2010

By Horst H. Gielen

Bong Mining Company/Liberia provides the rare opportunity to compare two generations of grate kiln pelletizing plants operating on the same magnetite/hematite ore basis. In this paper advantages and drawbacks are compared: mechanical aspects, energy-savings, pellet quality. Plant I with up- and down-draft drying gas flow. Plant II runs only on down draft drying and incorporates a heat-recoup system. Ferteco Mineracao/Brazil operates a Lurgi straight grate plant since 1977 on hematitic pelletfeed. Energy-political situation and char- coal as energy source in Brazil are reflected also in the search for alternative fuels for pelletizing. First measures and results are reported as well as intended further steps towards a 100 % oil replacement.

Jan 1, 1983

By Fiona M. Doyle, Christopher R. Lubeck, Michael C. Chin

The fundamentals behind a novel approach for creating inorganic/polymer hybrids are described. The binding of +2 charged ions, specifically Cue-and Cat+, to ionic functional groups is explored through UV-Vis spectroscopy and zeta potential measurements. The novel approach uses an electric field to drive ions into a functionalized polymeric matrix, thereby inducing the precipitation of calcium phosphate species. Scanning electron microscopy images of the resulting composite illustrate the results of these precipitations with two distinct morphologies observed.

Jan 1, 2003

By D. G. Purdy

Planning, as defined in Webster's New Collegiate Dictionary, is a detailed program of action designed to achieve an end. When developing a detailed plan to incorporate all the complex activities involved in a surface lignite mine, many elements must be carefully evaluated as to the individual and cumulative effects on the end result. The following elements are generally evaluated when planning a surface lignite mine: ? Reserve evaluation, including lignite quality characterization; ? Delineation of mining parameters, including lignite recovery factors, geotechnical factors, land control factors; ? Selection of mining blocks; ? Pit sequencing; ? Reclamation, including soil reconstruction design and land use planning; ? Overburden handling design; ? Selection of equipment; ? Sizing of equipment; ? Manpower requirements; and ? Other elements, including contract negotiations and execution, financing, investment return, operation economics, permitting and scheduling.

Jan 1, 1985

By N. E. Norman

The big hole drilling industry is a relatively new one. In fact, very little big hole drilling was done prior to 1950. If there is to be a marriage between big hole drilling and mining, we should certainly take a look at the background of the big hole drilling industry. Let us examine the three main features of big hole drilling and determine how each applies to mining. Let's also look at the good qualities and the limitations of each of these character traits.

Jan 1, 1968

By Charles Kocsis, Pedro Nascimento, W. Patrick Arnott, Samuel J. Taylor

Respirable crystalline silica (RCS) is an inhalation health hazard for mining and industrial work environments and must be monitored. We provide theoretical analysis of real-time measurements for determining RCS mass concentration without the use of filters by using photoacoustic spectroscopy. The suspended dust in the mine air can be continuously sampled by the photoacoustic instrument. A tunable quantum cascade laser is the light source, allowing for determination of interferences such as kaolinite, coal dust, and water vapor. The most useful spectral region is found to be between 11 and 13 μm. Absorption by water vapor, and, to a lesser extent, carbon dioxide, in this spectral region has gaps that allow for quantification of the aforementioned dust species as well as a convenient check on the calibration of the instrument. This work brings photoacoustic measurement of aerosol to the mid infrared range where spectrally dependent light absorption can be used to quantify dust composition and mass concentration.

Jul 31, 2022

By L. Sandbak

"CURRENT BASIS OF GROUND SUPPORT DESIGN ANALYSIS The current strategy used in determining what kinds of support are needed is based on empirical design charts (Grimstad and Barton, 1993). Figure 1 is an example of the topcut analysis used for a 14 foot wide (4.3 meter) drift, which is the current design width used for topcuts at TRJV mine. The majority of our topcuts are situated in ore of the Type IV and Type III weak rock class categories that necessitate the use of bolts, mesh and 2”-4” of shotcrete. This type of empirical chart gives excellent guidelines for the kinds of support, and it is based on case histories of civil tunneling and mining properties. It is a good starting point for determining the kinds of support needed, but not to the detail needed to optimize the number of bolts, type of mesh, or combination of types or strengths of shotcrete. This report is an attempt to help quantify the safety factor and optimum design parameters to include mesh and shotcrete as part of the design criteria and subsequent safety factor.SAFETY FACTOR ANALYSIS: BOLTS ONLY One type of safety factor analysis used at TRJV for the past 7 years is described as the “dead weight” method, developed by Pakalnis (2008). It involves the support of a conservative “dead weight” of rock held in place by bolts in which the depth of failure is approximated as a wedge whose height is one-half of the span. The failure or dead weight wedge resembles a triangular wedge that must be supported by the remainder of the bolts going through the wedge (see Figure 2).The support capacity of the system is determined by the bond strength of the bolts holding up the wedge, which is in turn based on the RMR. The method assumes the total support capacity is the sum of the individual bolt values defined by either the breaking strength or the bond strength of the bolts (whichever is lower) passing through the failure surface."

Jan 1, 2017

By Steve Kral

In December 2013, the Colorado Department of Transportation (CDOT) completed the widening of the eastbound tunnel on Interstate 70 (I-70) from two lanes to three. Work on the westbound tunnel began earlier this year and is scheduled for completion in December. The Twin Tunnels project is located in the mountains about 55 km (35 miles) west of Denver. They were bored during the 1960s when I-70 was being built and became the main access to Colorado?s growing number of ski areas and the state?s Western Slope. Throughout the decades following their construction, traffic on I-70 continued to increase and now the tunnels have a major bottleneck. Com-mutes to and from the mountain resorts, particularly on weekends, have become long and slow. Adding a third lane through the tunnels will help alleviate the congestion. (A complete report on the project can be found in T&UC, December 2013, page 61.) Once the eastbound tunnel was completed late last year, CDOT authorized the funding to begin work on the westbound side. That made economic sense, as the equipment used on the eastbound tunnel needed to only be shifted across I-70 to begin work on the westbound side, rather than removing it in December and bringing it back in March when construction began on the westbound tunnel. Work on the westbound tunnel uses essentially the methods that were used on the eastbound tunnel ? removal of the existing concrete lining and using drill-and-blast methods for tunneling widening. The main difference between the two tunnels is that the westbound side requires more blasting on both ends to widen I-70 to three lanes.

By Brendan Howard

Rio Tinto has a large globally distributed technical workforce and needs to ensure these employees have the requisite skills to not only manage technical risk and enable safe efficient production, but also ensure they are keeping pace with a fast-changing technological landscape. Traditional approaches to learning struggle for scale and an inability to respond to the extreme diversity of capability development needs. In response, Rio Tinto has successfully introduced innovative approaches to learning and employee engagement via leveraging the power of globally distributed networks for peer-to-peer knowledge transfer and providing mechanisms to recognise, reward and retain the individual technical contributors.

Feb 1, 2024

By William J. Miles

The inhalation of dust has been a problem in the mining industry since antiquity. Crystalline silica is now known to be the cause of silicosis, a form of pneumoconiosis that is associated with excessive exposure to respirable particles in some mining and industrial environments. Crystalline silica was reviewed by the International Agency for Research on Cancer (IARC) in 1986 and classified as a Group 2A, Probably Carcinogenic to Humans in Volume 42 and Supplement 7 of the IARC Monographs (1987). In 1996, IARC reviewed additional literature and studies published in the intervening decade and recommended that quartz and cristobalite, two polymorphs of crystalline silica, be listed as Group 1, Carcinogenic to Humans. Their recommendations and reclassification were published in 1997 in IARC Monographs 68.[2] In both Monographs, IARC classified amorphous silicas as Group 3, Inadequate Evidence for Carcinogenicity to Humans.

Jan 1, 1998

By C. A. Holley

The generation of coal fines is a growing problem which has serious environmental and resource recovery Impact. Several methods of agglomeration are studied including the production of briquettes for the consumer market. Simplified process flow diagrams, "order of magnitude" plant capital cost and operating costs are presented.

Jan 1, 1986

By Vincent Tricot, Daniel Altier, Roger Storry

"INTRODUCTION The Liantang / Heung Yuen Wai Boundary Control Point (BCP) project, located in the north-east New Territories of Hong Kong, will form the seventh land crossing between the Hong Kong Special Administrative Region (HK) and Shenzhen in China (Figure 1). The BCP project comprises an 11km long dual two-lane trunk road linking the border crossing facility to the existing road infrastructure in HK and when completed it will facilitate future regional development and alleviate frequent traffic congestion at the existing Boarder control points.In December 2013 Dragages Hong Kong (a member of the Bouygues Construction Group) was awarded the 5.4km long Contract 2 section of the project, including the 4.8km long Lung Shan Tunnels, by the Civil Engineering and Development Department of the Government of the HK SAR. To overcome the difficult ground conditions anticipated along the Contract 2 section of the project the tunnels will be constructed using mechanical and drill and blast (D&B) excavation techniques together with a 14.1m diameter multi-mode Earth Pressure Balance Tunnel Boring Machine (TBM). Land constraints imposed on the project alignment require that the final 500m section at the northern end of the Lung Shan tunnels, under Princess Hill (Figure 2), takes an almost 90 degree turn towards the north. The resulting 354m radius curve restricts the sight-line of road users to below the minimum 110m at 80km/hr hence, the internal span of the tunnels needs to be increased from 12.6m, in the standard straight section, to 15.4m in this curved section to accommodate a widened shoulder which will provide the required sight-line distance."

Jan 1, 2016

By T. F. Dumm

With increasing interest in the physical cleaning of fine coal, there is a need for extension of the sink-float analysis procedure to finer sizes. Problems arise, however, in ensuring complete dispersion of the particles in the heavy liquids. A procedure has been developed in which surfactants are used as dispersing agents and solids concentration is minimized (using a simple formula to estimate the minimum weight needed for statistical reliability). Using centrifuges to increase separation rates and sub-sieve particle size analysis of the specific gravity fractions, a complete size-specific gravity distribution can be obtained. Analyses have been performed on coal samples as fine as -10 µm.

Jan 1, 1987

By Arnold P. Szaj

There is no startling revelation to the fact that the mining industry as a whole is generally moving toward the use of larger equipment to process ores in quantities far greater than what was even considered a decade ago. Trucks and shovels have led the way in extra large machines and many other manufacturers have followed suit in the development of so-called "supers" in their line of equipment. In order to keep pace with the industry, crusher manufacturers have also enlarged the size of their equipment. There is now on the market, a Gyratory crusher capable of accepting a 72" diameter piece of ore. Primary jaw crushers have also increased in size. It is inevitable, therefore, that larger secondary cone crushers would also be required to complement the other equipment used to process these large quantities of ore. This super-size secondary cone crusher is the SYMONS 10 Ft. Cone Crusher. Until 1973, the largest cone crusher built was the 7 Ft. Extra Heavy Duty crusher, which is currently used in the majority of the mining operations throughout the world. The 10 Ft. crusher, when compared to the 7 Ft. Extra Heavy Duty Crusher, is approximately 1-1/2 times larger in physical dimensions; three times heavier; will accept a maximum feed size which is approximately twice as large; and will crush at approximately 2-1/4 times the rate of the 7 Ft. machine at identical closed side settings. It will be the largest cone crusher built in the world. At the present time, Rexnord's Nordberg Machinery Group has accepted an order for two 10 Ft. Standard cone crushers to be delivered to an iron ore mine in South Africa in early 1975.

Jan 1, 1973

By David D. Lambert

REE analyses of cumulate plagioclase from the PGE ore zone of the Stillwater Complex indicate that pressure fluctuations in the magma chamber acting on a single magma can- not be responsible for features such as the reappearance of Mg-rich olivine on the liquidus. The data is more consistent with a model involving multiple injection and mixing of geochemically distinct magmas. The PGE bearing sulfides of the J-M Reef are associated with such a re- appearance of olivine, indicating that the unusual location of the ore zone may be related to the addition of new magma, compositionally distinct from magmas that produced cumulates in the Ultramafic zone of the complex.

Jan 1, 1981