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By Joe B. Rosenbaum

Fine-sized mineral wastes discarded by ore milling plants require stabilization to prevent air and water pollution. Methods devised for achieving this stabilization include physical, chemical vegetative, and combination procedures. Although vegetative reclamation is preferred to physical and chemical stabilization, it is difficult to achieve because the wastes are sterile, contain deleterious inorganic salts, and lack the essential nutrients and physical characteristics required for sustaining vegetative growth. Nevertheless, recent research has developed methods for producing vegetative growth on all but excessively acidic, basic, or saline tailings at costs ranging from $100 to $650 per acre. This report summarizes effective procedures developed for vegetating average tailings, the cost differential between the various methods, and suggests procedures that may be applicable for achieving stabilization of pyrite-containing wastes that may oxidize and become excessively acidic. The use of buried layers of sewage sludge to prevent this acidification is discussed.

Jan 1, 1972

By M. Fig, B. Treffner, J. Brune, C. Strebinger, G. Bogin, D. Pardonner

"Methane gas explosions in a longwall coal mine can originate from in or around the gob and can seriously harm nearby workers and equipment. In order to fully understand the explosion flame and pressure wave propagation in the mine, it is important to investigate methane flame propagation in confined spaces as well as flame interaction with rock rubble and other mine structures. The latter can lead to enhanced turbulence causing high-speed deflagrations and/or detonations. Researchers ignited methane-air mixtures in horizontal, cylindrical reactors that contained inserts to simulate various gob characteristics. Rock surface topology and ignition location were investigated. Results show rock surface roughness increased fluid motion, thereby increasing methane flame front propagation velocity, overall pressure rise of the explosion, and time of pressure decay. Moving the point of ignition away from the open end of the reactor resulted in an increase in peak overpressure and an overall pressure rise of the explosion. Experiments were used to validate a computational fluid dynamics (CFD) combustion model that will be incorporated into a mine-scale explosion model to simulate and predict explosion hazards of large scale methane gas deflagrations in longwall coal mines. INTRODUCTION Coal mining is an integral part to our global society with coal-fired power plants providing about 40% of our global electricity [1]. A common method of extracting coal underground is by longwall mining. Researchers and investigative reports have found that explosive gas zones of methane-air mixtures can form along the longwall face and within the longwall gob, presenting an explosion risk to nearby workers and equipment [2]. In an explosion, the resulting flame and pressure wave presents a fatal traumatic injury hazard and can cause serious damage to equipment. In order to evaluate and mitigate the explosion risks in longwall coal mining, researchers at the Colorado School of Mines are developing a coupled CFD and combustion model of a longwall coal mine. The purpose of the model will be to better predict the explosion hazards under various mine conditions in order to build stronger prevention and mitigation strategies for miners."

Jan 1, 2018

By P. M. Soupios

An integrated suite of environmental methods was used to characterize the hydrogeological, geological and tectonic regimes of the study area, to determine the geometry of the landfill (depth and spatial extent of electrically conductive anomalies), to define the anisotropy caused by bedrock fabric fractures and to locate potential zones of electrically conductive contamination. The study area which covers an area of about 0.08 Km2 is a municipal solid waste site (MSW), located 20Km West of Herakleion in the central part of Crete (S. Greece). The landfill is located in a northwest oriented valley with highlands to the northeast and southwest. The combination of geophysical methods and chemical analysis are commonly implemented for characterization and management of land-fills. At the particular site, geophysical methods were focused on studying the electrical insolating properties of the materials, electrical con-ducting properties of fluids (leachates) and electromagnetic properties of the disturbed regolith materials in the burial zones. Three different types of geophysical surveys were performed: 1) 2D electrical tomography (ERT), 2) electro-magnetic measurements using very low frequencies (VLF) and 3) electromagnetic conductivity (EM31). Furthermore, in order to calibrate the geophysical methods dielectric spectrometry measurements are conducted. To evaluate the environmental degradation of the area, soil and liquids samples were collected.

Jan 1, 2005

By K. Zhang

Real option value (ROV) method is considered to be more practical and advanced compared to net present value (NPV) method in evaluating a mining project, in particularly when there is substantial uncertainty in the commodity market as well as possible operational flexibility embedded in the project. Usually, it may take months or even years for the commodity product to be available in the market after the mining activation decision is made. The impacts of postponing the delivery of commodity product on the mine?s ROV and NPV are assessed based on the proposed real option method. Postponing the delivery of the products leads to declined NPV and ROV compared to the non-postponing scenario and extended postpone results in higher lost values in NPV and ROV. For a mine with lower mining cost, by postponing the delivery, the exercising threshold of commodity price is lower because the mine owner anticipates that commodity price may rise during the time of postponing. A mine with higher mining cost requires a higher exercising price threshold to ?lock up? the profit when there is ambiguity of market situation due to the postponing of the delivery.

Feb 23, 2014

By Heriban Soto

Primary amines are strong collectors of apatites and they can selectively float sedimentary phosphates from calcareous ores. However, secondary and tertiary amines and tri-methyl ammonium salts were ineffective. The use of kerosene reduces the collector requirements because hydrocarbon is coadsorbed along with the amine on the mineral surface. The heats of reaction of aminium ions with such anions as phosphate, carbonate and sulfate, were measured in a microcalorimeter and discussed in terms of the solubility of the precipitates formed and their relationship with the adsorption mechanism of primary amines on phosphate minerals. Experimental evidence supports a view that primary amines are adsorbed through chemical interaction between the aminium and phosphate ions at the mineral surface.

Jan 1, 1984

By J. D. Miller

The effects of operating variables on water transport to the over- flow, classification of hydrophilic particles and the recovery of copper and molybdenum from a low-grade porphyry ore are presented. Recoveries of copper and molybdenum exceeding 90 percent at a grade of 8 percent Cu and 0.2 percent Mo were realized for minus 100 mesh (1 49 µm) material at retention times of less than 500 milliseconds. The rapid rate of flotation and the effective separation of fine particles for an air sparged hydrocyclone appear to be due to directed interaction of particles in a high force field with numerous freshly formed small bubbles. This interaction occurs in the swirl flow developed by the system and is analyzed in terms of collision and induction time phenomena.

Jan 1, 1982

By Otis M. Clarke

The purpose of geochemical research in the Alabama copper belt is to re-evaluate geochemical prospecting methods as related to igneous and metamorphic rocks in a humid climate. It is also a correlation of laboratory research on copper mineral solubility with geochemical anomalies over known mineral deposits. Geochemical prospecting in warm humid climates involves different problems and conditions than geochemical prospecting in semiarid areas. Stems and others (1972) reported soil surveys in a humid tropical environment in Bahia, Brazil, were not effective in outlining areas of copper mineralization. Clarke (1971) reported false anomalies in lateritic soils in Alabama over mafic rocks. Bjorklund (1971) reported biogeochemical sampling in Finland was ineffective in detailed work outlining potential mineralized areas, although it may serve to indicate regional areas of high mineral potential. During this investigation, water, stream sediments, residual soil, and organic matter, mainly twigs, were collected from three known copper-mineralized areas. Samples were selected so as to cross mineralized outcrops and results were correlated with copper stability charts as reported by Silman (1958) and Schmitt (1962). The geochemical research performed in Alabama should be applicable to other humid areas. Geologic, Climatic, and Pedologic Setting The area of investigation is in the southern end of the Appalachian eugosyncline in eastern Alabama. It includes the Hatchet Creek prospect, Pyriton mining district, and Stone Hill copper mine. The copper mineralization is in calcium-rich metasediments that lie along the western flank of a high rank metamorphic belt. All three deposits are in the uplands of the Ashland Plateau section of the Piedmont physiographic province. The Hatchet Creek copper prospect (Clarke, 1963; 1971) consists of three mineralized areas that contain pyrrhotite, pyrite, and chalcopyrite in small crisscrossing veinlets.

Jan 1, 1972

By Remi Tremblay

This paper describes the laboratory study which permitted an exploration of high grinding ball consumption in the secondary open circuit wet grinding mills at the Sidbec-Normines plant, Port Cartier, Québec. Corrosion undoubtedly exists but is of minor importance. Abrasion resulting from the physical nature of the company's iron concentrate is the main reason for the high ball wear. It was found that at least 30% reduction in ball consumption is possible by decreasing attrition grinding through the use of lifters in the mill. At the industrial level this would entail more lifters and/or higher lifters in the mill linings.

Jan 1, 1984

By L. S. Gertsch, M. Z. Abu Bakar

The research presented here is part of a project to quantify the differences in the mechanical excavatability of rocks in dry and water-saturated conditions. A series of full-scale laboratory linear rock cutting tests were carried out with a long-bladed single disc cutter on dry and water-saturated sandstone blocks. The muck collected from the cutting tests was analyzed to establish a link with the specific energy (SE) of the operation. The coarseness index (CI), a non-dimensional parameter, was found to be a useful indicator of the relative efficiency of the cutting operation. An inverse relationship of the form SE = k CI-n was observed between SE and CI. The power n of the relationship for both dry and saturated rock was much lower than found in previous studies. The exponent n is believed to be dependent on the strength of the rock and the cutter type used. Although the average CI was lower for saturated rock than for dry rock, at the same time, saturated rock cutting was found to be less energy-intensive (in terms of SE) than dry rock cutting. Moderate correlation exists between the production rate or yield and the SE of the cutting operation for both dry and saturated rock, which can provide some useful information about the field production rate, discounting the effect of discontinuities in the rock mass.

Jan 1, 2012

By G. E. Sreedhar, R. Kumar

The pockets of high silica blue dust across the entire high grade hematite deposits in the Bailadila sector bothers the excavation activity due their iron content, which is higher than the threshold value specified by the Indian Bureau of Mines and the agony of stacking them separately due to their fragile & powdery nature. The physical nature of blue dust and its negligible alumina content makes these a potential source of hematite, which is a blessing in disguise. As most of the particles are in the form of an independent grain making it appropriately suitable feed for dry magnetic separation and thus the dry beneficiation has turned a bane into boon by enabling to produce concentrate either suitable for using as DSO or amenable for blending. The emphasis on carrying out dry beneficiation studies in the present context serves the purpose of mineral conservation, mitigates the issues of excavation and stacking as well as conservation of water resource. This paper describes the laboratory and pilot scale dry beneficiation studies carried out on blue dust of 48 – 60%Fe and Silica up to 30% at 25 Kg/hour to 400 Kg/hour, resulting in production of concentrate assaying 60 – 65%Fe. INTRODUCTION High silica blue dust (HSBD) is associated with Banded Hematite Quartzite (BHQ) and is available in abundance in various pockets across the Iron ore body in the Bailadila region of Chhattisgarh state. High Silica Blue dust occurs in the form of free granular particles and also as friable lumps. The chemical quality of this falls under sub-grade category (45 – 55%Fe) and as per the guidelines of Indian Bureau of Mines, these are to be stacked and conserved as future resources of Iron if it can’t be utilized in the present circumstances. Due to its friable nature, stacking of HSBD is a challenge and it is also compounding the problem by polluting the air under high velocity wind conditions. Because of its physical nature and occurrence in pockets pose challenge to systematic mining. The existing processing set up of the operating mines is designed to treat either Direct Shipping ore (DSO) or Run-of-Mine (ROM) have grade >60% Fe. The present practice of beneficiating iron ore fines (<1 mm) comprise combination of two or more processes such as desliming, hydraulic classification, magnetic separation and flotation apart from requirement of grinding depending on liberation characteristics. The HSBD which is predominantly occur as free granular particles, is significantly low in its alumina content. This gives us an opportunity to utilize them by exploring a suitable beneficiation process so that the concentrate produced can be used as a sweetener for alumina rich iron ore/concentrate. Thus, in the present study, an attempt has been made to adopt dry high intensity magnetic separation technique to explore the amenability of the high silica blue dust for beneficiation.

Jan 1, 2019

By D. R. Zuchelli

The purpose of wrapping ball mills with thermal/acoustic blankets is twofold: 1) to maintain the desired temperature inside the mill, and 2) to reduce the sound emanating from the mill. This field case study focuses solely on the latter, evaluating and documenting the sound level reduction attributed to the installation of the blankets on ball mills and its potential to reduce the noise dose experienced by the process attendant. One of the three ball mills had already been treated (baseline) before the evaluation started. However, treating the remaining two mills still proved to be very effective, further reducing ball mill noise in the near field by as much as 10.0 dBA and producing far field noise reductions of 3.0 dBA or greater, extending as far as 35 feet from the mills and to the floor above. The model developed from the survey data shows that a process attendant spending a substantial portion of a shift in the mill building will experience a significant reduction in overall noise dose.

Jan 1, 2010

By J. D. Vincent

The Mission By-Products Plant at the Mission Concentrator of the American Smelting and Refining Company, some 20 miles south of Tucson, Arizona in the Twin Buttes mining area, has been in operation slightly over a year. The plant produces a molybdenite concentrate a copper concentrate and, at times, a zinc concentrate. An intensive test program of over three years was conducted at Mission to make the recovery of molybdenum economic. Briefly it was found necessary to make a scavenger concentrate in the copper mill before it was possible to recover economic quantities of molybdenite. By so doing there were resulting additional recoveries of copper, silver and zinc. This program resulted in the design and construction of the existing plant. A paper by the authors discussing the test work and the design was presented at the, October 1965 meeting of the American Mining Congress in Las Vegas, Nevada, by Mr. Wayne Bossard.

Jan 1, 1966

"From April 22 to 28, the eyes of the tunneling and underground construction world will be on San Francisco, CA, as the world’s most influential underground construction industry leaders gather at the Moscone Center for the 2016 World Tunnel Congress.Recognized as the most important international annual meeting for the industry, the 2016 version comes to the United States for the first time in 20 years and will be hosted by the Underground Construction Association of SME (UCA of SME). The conference will be held in lieu of the UCA’s biennial North American Tunneling Conference and will bring the strengths and resources of the UCA of SME and the International Tunnelling and Underground Space Association (ITA). The result will be a conference with unmatched technical programming and a showcase of more than 200 exhibiting companies.A program committee led by Randy Essex of Mott MacDonald, Lonnie Jacobs of Frontier Kemper Constructors, Michael Mooney, of the Colorado School of Mines, Priscilla Nelson, of the Colorado School of Mines and Amanda Elioff of Parsons Brinkerhoff formed the program committee and worked for more than two years to build the program. The result is four technical sessions with five tracks in each session and 185 oral presentations.“One challenge was the sheer size of the group that would be assembled, perhaps 2,500 attendees or more, and the large number of abstracts we were likely to receive,” said Essex. “ We investigated extending the conference a fourth day, but that was not workable with the Moscone Center. We settled on having five concurrent technical tracks – something that has not been attempted in past NAT or RETC conferences to my knowledge. The next step was to develop suggested session titles that would span the breadth of subjects that would interest conference attendees as well as serve the conference theme.”"

Apr 1, 2016

By Gordon M. Bell

Water has received little attention as a variable in flotation, even though it is a known fact that water hardness often has an adverse effect on purity and recovery, particularly on the flotation of non-metallic minerals. Because of this fact, process water used in some flotation plants is treated to reduce hardness to an acceptable level. In the laboratory, distilled water is usually used as the flotation medium in order to standardize conditions, whereas in flotation plants locally available water is used. At Rosiclare Works of Aluminum Company of America, Rosiclare, Illinois, where a vein-type of fluorspar deposit was being processed by flotation to make an acid-grade fluorspar concentrate until February of 1968 when the plant was closed, qualitative correlations had been observed between metallurgy and reagent consumption and the seasons of the year. The observed effects were thought to be due to seasonal variations in the quality of Ohio River water used as the flotation medium. Figure 1 shows the variations in total hardness and chloride contents of Ohio River water at Rosiclare for the period September 1964 through September 1967. During this period, the sulfate content varied from 85 to 245 ppm (as Na2SO4), the calcium from 90 to 160 ppm (as CaCO3) and the magnesium from 50 to 70 ppm (as CaCO3). The data in Figure 1 show that the total hardness and chloride contents are highest in the late summer and fall which are usually periods of low water and lowest in late winter and spring which are usually periods of high water.

Jan 1, 1970

By Fritz Kleiner, Walter Meintrup

On Nov. 4, 1981 A/S Sydvaranger&apos;s 1-kt/h (1,100-stph) wet-process, iron ore ball mill completed its first four months of uninterrupted, full-load operation in Kirkenes, Norway. This 6.5-m-diam (21-ft-diam) mill is driven by a gearless ring or wraparound 8.1-MW (10,860-hp) motor at 13.1 rpm-a first of a kind in this segment of industry. This article examines reasons for selecting this type of drive over more conventional schemes, lists specific advantages of such large mills, and describes the installation in Norway. History For almost a decade, good operating experiences have been gained with 28 gearless ring motor drives in the cement industry, driving 2.5 to 4-m-diam (8.2 to 13-ft-diam) tube mills with drive powers ranging from about 3-4 MW (4,000 - 8,000 hp). Why then did the mineral ore processing industry hesitate until 1980 to adopt this successful concept for similar applications on ball, semiautogenous, and autogenous mills? There are a number of good reasons in the eyes of conservative mill builders and operators, the most commonly cited ones are: • No operating experience in this segment of specialized industry. • More severe environmental conditions in the wet ore grinding process. • An indifferent attitude of mill builders and electric motor manufacturers towards new drive technologies. • Limited confidence in solid-state power supply systems, such as frequency converters of the required size. There have been and still are numerous problems associated with low-speed geared mill drives of any kind, especially with individual motor/gear sizes approaching or exceeding about 4 MW (5,360 hp). Every mill builder knows about them, but operators learn to accept them as inevitable. The Decision to Change Three things combined to break this technological stalemate: the courage and progressive spirit of one major iron ore processor in Scandinavia, the cooperation of three experienced manufacturers, and an unusual application problem that could not be solved by any conventional approach. The last factor was surely the decisive one, but the first one does not come as a surprise either. The Swedes near Kiruna and the Norwegians around Kirkenes are experienced ore miners and processors, and much credit goes to them for technological breakthroughs in the industry. At A/S Sydvaranger in Kirkenes, above the Polar circle at about the latitude of Alaska&apos;s northern tip, the existing grinding facilities, with a total of 14 100 to 240-t/h (110 to 264-stph) ball mills, can not be expanded. Nevertheless, to increase mill throughput, only installing a larger mill in place of an existing smaller one was a practical alternative. For this replacement, the owners set requirements that seemed impossible to meet: • The old 100-t/h (110-stph) ball mill should be replaced with a new ball mill with 10 times the rated throughput, without significantly impairing the operation of the remaining mills, and without significantly changing the mill building. • The new mill should have a variable-speed drive to ultimately optimize the grinding process by means of a closed-loop process¬computer-controlled grinding cycle, and to minimize the specific energy consumption. • Availability, efficiency, and life expectancy of all new components must be higher than those being replaced. • Inrush-current and harmonic loads on the rather weak electric supply line must be minimized to ensure safe plant operation. All old ball mills at A/S Sydvaranger are the geared type, using single synchronous and wound-rotor, slow-speed motors with ring-and-pinion gears. Operators are familiar with the limitations and problems associated with such drives, and they are aware that the following items become major concerns when drive powers are drastically increased: • Gears are subject to wear and tear, require frequent maintenance, and eventual replacement of major parts. • Gears are sensitive to misalignment, overload, and thermal distortion, limiting their useful life. • On dual or quadruple drives, load-sharing and torque oscillations between motors can be a major reason for concern. • At these speeds, ring-and-pinion gears reach their torque transmission capabilities altogether at around 4 MW (5,360 hp) per motor/pinion. To obtain the desired variable-speed performance of the new drive, the only practical and economical conventional solution would have been a frequency-controlled, low- or medium-speed dual motor drive with about 8 MW (10,720 hp) of power. This, however, was not feasible because of limited floor space. Therefore, bids were solicited for the alternative drive method, the gearless ring motor. General Considerations Why are such large mills considered? After all, one could avoid all the problems by simply staying with smaller mill unit sizes. Under competitive pressures of free markets, however, grinding efficiencies and specific energy consumption become key factors in selecting new equipment. Specific energy consumption of ball mills decreases with increas-

Jan 9, 1982

By Omar A. Muhtadi

Brohm Mining Corporation, in conjunction with Geobiotics, Inc. has nearly completed a pilot heap biooxidation test on sulfidic ore from the Gilt Edge Mine near Rapid City, South Dakota. Some results from the pilot testing have shown the correlation between the extent of biooxidation and the increase in cyanide gold recovery seen in the laboratory. Bench scale testing showed approximately a 1: 1 correspondence between percent biooxidation and percentage increase in gold recovery. The economics of large scale biooxidation were also evaluated in terms of increased gold recovery versus the time and cost of biooxidation. In the pilot test, the rate of biooxidation became limited by the acid water neutralization system. Later in the test, measures were taken to overcome this problem. Results from bench scale column bioleach testing showed that the Gilt Edge sulfide ore is quite amenable to biooxidation with a substantial increase in gold recovery with just partial biooxidation. Direct cyanide gold recovery of 51 % on ore crushed to -3/8" was enhanced to 82-85% after oxidation of37% of the sulfide as measured by iron. Laboratory experiments also showed that the slow rate of biooxidation of this ore could be accelerated by removal of metal sulfate build up from the leach liquor. The combination of these normally non-toxic metals became inhibitory to biooxidation if not removed by the neutralization circuit.

Jan 1, 1995

By Nan Hua

As a high production and high efficient mining method, top coal caving method is now widely used in China. However, as more extra-thick coal seams are mined, it becomes more and more difficult to make the top coal fully broken up, resulting in more and more top coals flowing into the gob, rather than onto the rear AFC at the working face as designed. This research is aimed to investigate the failure mechanisms of the extra-thick top coal caving mining method.

Jan 1, 2009

By G. C. Hambleton

There is sufficient indication of the existence of a basic misconception in the Coal Mining industry (on a world-wide basis) as to what computer control really does, what it costs, how it works and how and what it achieves as to make this presentation a welcome opportunity to present the case in what we hope is a simple, meaningful way. A plant cannot be said to be "automated" unless the control system has the capability to react automatically in accordance with predetermined programs under a great multiplicity of operational situations.

Jan 1, 1981

By Jorgen Elbrond

Shovels, trucks and repair bays for the trucks each play their role in the capacity of an open pit operation. It is therefore convenient to have a procedure for the capacity calculation which takes all 3 factors into consideration in a comprehensive manner. This can be done by means of a cycle model, earlier developed for the shovel-dumper circuits, when the repair facility with its number of repair bays is added as a superimposed service system, which the trucks visit at certain specified intervals. The calculation model transforms the mechanical availability of the trucks into their operational availability. The system&apos;s capacity in truckloads per shift and the trucks&apos; operational availability of certain combinations of shovels, trucks and repair bays are shown.

Jan 1, 1981

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&apos;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