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By H. K. Lin

Residual cyanide in cyanidation tailings can be detoxified by its oxidation to cyanate, as in the Inco and Degussa processes. However, cyanate, the product of detoxification and other oxidation processes, may be reduced to cyanide in reducing environments, e.g., deepwater discharge of cyanidation tailings. This study shows that the reduc-tion of cyanate to cyanide occurs and that the reduction rate increases with decreasing solution redox potential. Solutions with lower pH favor the reduction rate. No significant difference was observed between the results of tests prepared with distilled water and seawater, and the presence of cyanidation solid tailings does not show an effect on the reduction. Because cyanate can be reduced to toxic cyanide, causing environmental concerns, the deepwater discharges of cyanidation tailings must be handled carefully.

Jan 1, 2008

By J. O. Marsden

Over the past eight years, Phelps Dodge (a subsidiary of Freeport-McMoRan Copper & Gold, Inc.) devoted a significant amount of effort to the development of a suite of processes for the effective hydrometallurgical treatment of copper sulfide concentrates. This effort resulted in the development of high-temperature (>200ºC) and medium-temperature (150° to 165ºC) pressure leaching processes. Specific configurations of both processes have been commercially demonstrated at Phelps Dodge?s facility in Bagdad, Arizona. This paper reviews in detail the chemistry of medium-temperature pressure leaching of copper concentrates and reports on the process development work conducted by Phelps Dodge and others for this technology. This paper is Part I of a four-part series on this technology. Part II covers the development of medium-temperature pressure leaching and direct electrowinning technology; Part III considers the large-scale demonstration of the MT-DEW-SX process at Bagdad, Arizona; and Part IV addresses the development and design of a full-scale commercial application at Morenci, Arizona.

Jan 1, 2007

By Carl G. Bock

INTRODUCTION The Washington Metropolitan Area Transit Authority (WMATA) has let a contract for the excavation of three rock stations, spaced about 3550' (1082m) apart, beneath Connecticut Avenue in Washington, D.C. Two previous rock stations have been completed, one of which had a crown pilot tunnel excavated to explore geologic conditions that would be encountered during the station excavation. This pilot tunnel was primarily for inspection by bidders and design was based on core hole information. The other rock station had no pilot tunnel and was also designed on the basis of core hole information. The three rock station areas, which are the subject of this paper, have been explored by crown pilot tunnels and an as-built report, with geologic maps and sections, has been prepared, for use by the design engineer as the basis of design for support of the structures. The geotechnical report describes the geologic structure in detail and relates it to excavation and support of the three crown pilot tunnels and the running tunnels which will be enlarged to create the 58'W x 44'H x 700'(+)L (17.6m x 13.3m x 212m +) stations. The information was complete enough to permit the design engineer to visualize the geologic structure and compute loads for the various types of rock conditions. It was therefore possible to determine the size and spacing of the steel sets for the several different conditions of rock structure encountered in the pilot tunnels.

Jan 1, 1976

By W. G. Willson, D. E. Walsh, B. Irwin

Low-rank coal (LRC) drying processes are generally categorized by operating temperature, drying environment and type of feed (either sized or ground coal). Within these broad categories, drying processes differ according to the type of drying equipment and methods of quenching and stabilizing the dried products. This paper focuses on the produce quality of various LRC drying processes including conventional low and high temperature evaporative drying and non-evaporative, hydrothermal drying. The former may be preferred if the dried product can be utilized immediately, but moisture reabsorption, spontaneous heating and fines production during handling are problems associated with longer term storage, transportation and utilization. Methods for reducing these problems are discussed. Hydrothermal processing is an advanced technology featuring high pressure, non-evaporative drying, which solves stability problems by producing a liquid feel.

Feb 24, 1997

By John M. Dale

Now that the price of sulfur has reached unexpected high levels, it is little wonder that sulfur from surface ores is again receiving attention. In most instances, it is advantageous for an ore to be at or near the surface. However, it is a distinct disadvantage for sulfur ore to be close to the surface because it precludes the use of the Frasch process. The Frasch process depends on the presence of at least 180 m of uniform overburden to allow pressure injection of superheated water into the sulfur-bearing formation to melt the sulfur. In the Frasch process, sulfur separates cleanly from the gangue underground and comes to the surface in a very pure form. Surface sulfur deposits, particularly those in the Western Hemisphere, exist largely due to volcanic activity, and sulfur separation from the gangue is a formidable technical problem. None of the surface deposits are large compared to some of the Frasch deposits, but at the present sulfur price, they are certainly of economic importance. From the turn of the century until 1975, the price of sulfur was for the most part $18-$28/t. However, with the price of sulfur now over $154/t, there are a variety of technical alternatives to consider for sulfur surface ore separation that may not have been economically attractive a few years ago.

Jan 9, 1981

By C. Keefe, O&apos

Measurements of the quantity of entrained air within processes have challenged instrumentation developers for years. This is particularly true in the unique and demanding operating environment and applications seen in minerals processing. In minerals processing applications, entrained air plays a role in errors seen within nuclear density gauge measurements and in pumping efficiency. It is also the major component of flotation processes. The measurement of the quantity of entrained air, known as the gas void fraction, can now be performed from the outside of a process pipe through CiDRA?s patented passive sonar array-based technology. Within column cells, the need for a robust, no maintenance, accurate means of measuring the entrained air, known as gas holdup, has resulted in a submersible version of this technology. CiDRA?s meter technology calculates the gas void fraction by first measuring the speed at which naturally occurring sound in the process slurry propagates past an axial array of sensors. These sensors are incorporated in a band that is wrapped around the outside of the pipe, resulting in no process downtimes for installation and unprecedented reliability. A known relationship between this speed of sound and the entrained air captured in the form of bubbles within the slurry is then applied in CiDRA?s meter to calculate the gas void fraction. This paper will present the measurement technology, its operation, its calibration and its application in a variety of gas void fraction and gas holdup measurement situations such as pumping efficiencies, hydrocyclone operation, external sparging, and column cells.

Jan 1, 2008

By Ed Cope

The newly discovered South Arturo deposit is a Carlin-type, breccia-hosted, oxide gold deposit located on the Dee Mine property at the north end of the Carlin Trend in Nevada. The Dee Gold Mine was discovered in 1981 by Dee Delamar, a Cordex geologist. The property was put into production by Rayrock Mines in 1984. During its 16-year mine life, the Dee Mine produced about 18.6 t (600,000 oz) of gold from oxide ore at an average production rate of about 1.24 to 1.55 t/a (40,000 to 50,000 oz/year). In October 1997, Bar-rick Gold Exploration acquired the right to earn a 60-percent interest in the Dee property from Dee Gold Mines through an exploration farm-out agreement. Barrick Gold Exploration began exploration activities on the property in 1998 and vested in its 60 percent operating interest in 2004. However, the discovery hole at South Arturo was not drilled until July 2005 from atop the historic mine dumps located 300 m (985 ft) south of the Dee openpit. The discovery hole (BD-72) encountered a cumulative 75.6 m (248 ft) of oxide mineralization grading 1.9 g/t (0.055 oz/st) gold beneath 260 m (855 ft) of dump material and post mineral Tertiary Carlin Formation volcanic and sedimentary rocks. Oxidation within the deposit extends to depths greater than 610 m (2,000 ft). The deposit has passed the prefeasibility test and is presently in the feasibility stage. Exploration is on-going to enhance or enlarge the known deposit. The current resource for the deposit stands at 40.4 t (1.3 million oz) of gold. The South Arturo discovery is an example of an historic mining property yielding a new discovery through the diligent application of area selection criteria of the model type and persevering when early results were generally negative. Barrick?s original exploration pro-grams on the property were focused on the discovery of deep, high-grade sulfide deposits that would likely be mined by underground methods. As it turns out, South Arturo is mostly oxidized and will be amenable to mining by openpit methods

Jan 1, 2008

By Donald P. Tuchman, Justin R. Patts, Emanuele G. Cauda, Andrew B. Cecala, Elaine N. Rubinstein

Video techniques for monitoring exposure, such as NIOSH’s “Helmet-CAM,” employ both real-time dust monitors and mobile video cameras to assess workers’ respirable dust exposures. Many real-time personally worn dust monitors utilize light scattering sensing elements, which are subject to measurement biases as a function of dust type (size, composition, shape factor) and environmental conditions such as relative humidity. These biased and inaccurate dust measurements impair the monitor’s ability to properly represent actual respirable dust concentrations. In the testing described, instrument mass concentration data was collected using three different types of commonly used commercial off-the-shelf personal dust monitors and compared to a reference standard. This testing was performed in a calm air (Marple) dust chamber in which three units of each make and model (for a total of nine monitors) were used for each test. Equivalency factors (EF, a multiplier to match the Thermo TEOM 1400a reference instrument) ranged between 0.746 and 1.879 across all dusts and environmental conditions tested, and between 0.821 and 1.519 on the ISO test dust.

By Donald P. Tuchman, Justin R. Patts, Emanuele G. Cauda, Andrew B. Cecala, Elaine N. Rubinstein

Video techniques for monitoring exposure, such as NIOSH’s “Helmet-CAM,” employ both real-time dust monitors and mobile video cameras to assess workers’ respirable dust exposures. Many real-time personally worn dust monitors utilize light scattering sensing elements, which are subject to measurement biases as a function of dust type (size, composition, shape factor) and environmental conditions such as relative humidity. These biased and inaccurate dust measurements impair the monitor’s ability to properly represent actual respirable dust concentrations. In the testing described, instrument mass concentration data was collected using three different types of commonly used commercial off-the-shelf personal dust monitors and compared to a reference standard. This testing was performed in a calm air (Marple) dust chamber in which three units of each make and model (for a total of nine monitors) were used for each test. Equivalency factors (EF, a multiplier to match the Thermo TEOM 1400a reference instrument) ranged between 0.746 and 1.879 across all dusts and environmental conditions tested, and between 0.821 and 1.519 on the ISO test dust.

"Tell us how you got involved in mining and about your career path.My dad was a coal miner and my uncle was a metallurgist, so when I enrolled at Penn State’s New Kensington Campus, I chose the College of Earth and Mineral Sciences — exact majors didn’t get picked till the end of your sophomore year. Penn State New Ken had an associate degree in mining program and one of the guys in my carpool was going to take Mining 30 in the evening and the other guy (mechanical engineer) was also able to take an evening class. I didn’t want to break up the carpool, so I took Mining 30, complete with essay tests. I could write, so I did well, and the professor said I should go into mining engineering. Fast forward to the end of the next term at University Park, and I realized there wasn’t enough chemistry in mining. Switching to metallurgy would have meant another term at that point, so Dr. Lovell, my advisor, trotted me down the hall and to the next building and said I was a mineral processor. That stuck. I was a summer student at U.S. Steel Research between my junior and senior year and they paid for my master’s degree — all about clay and macerals in coal flotation. During that time, the steel industry tanked, and I thought a Ph.D. would be a good idea — I could always teach at the university level if I had those credentials. The Electric Power Research Institute had a Coal Cleaning Test Facility in Homer City, PA, and I conducted my Ph.D. research on rate and residence time in conventional coal froth flotation cells there and at a local cleaning plant. I went to work at the test facility in 1987 (later CQ Inc.) and stayed there until I started PrepTech Inc. in 1997. PrepTech offers some consulting services for coal cleaning plants and sells mineral processing equipment, mostly to coal companies. I can’t believe it’s been 21 years.And what about your SME career?Of course, I was a student SME member at Penn State. We used many of the SME books in class, so who wouldn’t want the student discount? While in Homer City, I became involved with the Appalachian Plateau Subsection of the Pittsburgh Section. We’d hold quarterly meetings with interesting speakers and had good attendance. I was the secretary. I’m still the secretary and also get the bank statements. We’ll need to close that out some time, but I guess I’ve been hoping for resurgence in the Indiana/Cambria/ Somerset area."

Jan 3, 2018

By Jamal Rostami, Levent Ozdemir, Amund Bruland, Filip Dahl

Cerchar Abrasivity Index (CAI) is one of the commonly used tests to evaluate rock abrasiveness for cutter life/cost estimations of TBM projects. There are at least 3 style machines, 2 different pin hardness, and the test could be run on fresh rock surface VS a sawn surface. Each of these parameters has a meaningful effect on the results, but its impacts were not fully understood nor its implications well explored. This paper reviews the current practice of Cerchar testing and its implications on geotechnical investigations related to TBM tunnels and provide a set of guidelines on testing and reporting of the test results for future projects.

Jan 1, 2005

By W. L. Zhong

Probability function integration method is one of the influence function method. It is a widely accepted method in many mining districts in China and Poland mainly because its theory and formulae can well-represent the surface subsidence basins due to longwall mining of flat or near-flat seams. This paper introduces the basic theory of the probability function integration method and determines its 4 basic parameters by analyzing the measured subsidence profiles in eight longwall panels in Northern Appalachian Coal field. It also discusses the two methods for determining the 4 parameters. Finally the acquired parameters are used to predict the subsidence and deformation of the houses for damage assessment. Comparisons are made between the measured and the predicted subsidence. Probability Function Integration Method The probability function integration method for predicting surface movements and deformations is widely used in China and Poland. The governing equation of the method contains five parameters: subsidence factor, a, offset of inflection point, d, tangent of the major influence angle, tan fl, horizontal movement constant, b, and major dispersion angle e (e = 90. for flat seams). Its applicable range iis much larger including seams less than 30' from the horizontal, critical and noncritical mining and soft to hard overburden.

Jan 1, 1986

By L. Frederick

Measurement of gamma radiation occurring in nature to characterize geological formations has been widely recognized in mineral exploration. Different methods and apparatuses have been developed for drill hole logging purposes. Geological formations vary in amount of naturally emitted gamma radiation. A gamma signature from a geological formation is captured by utilizing different types of gamma detectors. A natural gamma radiation detector (NGRD) can be used to control mining whenever there is a significant difference between the radiation levels in the mineral or ore being mined and the waste materials surrounding the ore. Surface miners, such as the one shown in Figure 1, can precisely control the elevation of the cutter as the machine moves over the surface of the formation. This type of machine is predominantly used in selective mining operations, e.g. surface coal mining. If there is a means to know the position of the cutter relative to the interface between the ore and waste, the miner can recover all or most all of the valuable mineral with very little out-of-seam dilution. This paper discusses the results of a successful application of gamma detectors to control a surface miner at one of North American Coal Corporations? locations - Red Hills Mine. The mine has nine coal seams in total with thicknesses ranging from 12? to 60?. The bottom six seams (Figure 2) are minable. The mine has complex geology and a significant amount of annual rainfall (4.7 ft). The mine produces approximately 3.5 million tons of coal and about 40 bcy of overburden per year. The operation utilizes diverse mining equipment including Dragline Marion 8200, electric shovel P&H 2800, Caterpillar end dump trucks CAT 785 and 789; bulldozers CAT D11, D10, D8, and D6. Coal is mainly extracted by utilizing a Wirtgen SM 4200 surface miner that is loading CAT 785 trucks with high volume coal bodies and payload of 150 t. Operational cutting depth is 24 inches with maximum cutting depth of 36 inches. Surface miner operators determine a cutting depth based on multiple cues, the most important being visual observations of a coal seam being cleaned or mined. The cleaning process involves removal of the last foot of waste material covering the coal seam. This is one of two critical phases in the coal extraction process. If, during the cleaning process, an operator sets a cutting head too deep, valuable product is wasted. If it is set too shallow, waste material is left to be mined with the coal. The second critical phase occurs in the last cut on the interface between the coal and waste material at the bottom of the coal seam. If the cutting head goes deeper than favorable, then waste material is delivered to a power plant.

Feb 27, 2013

By Henry A. Signore

The Appalachian coalfield, located in eastern Kentucky, Pennsylvania, Virginia and West Virginia, has been one of the most productive in the United States. Total production from the Appalachian coalfield during 1994 was 340.8 Mt (375.4 million st), or 37% of the 929 Mt (1 billion st) produced in the United States that year. This region contains various coal types from high- to mid-sulfur coal in Pennsylvania and northern West Virginia to low-sulfur, compliance steam coal and premium-grade metallurgical coal in eastern Kentucky, Virginia and southern West Virginia. The region's product is in high demand in domestic and export markets. Productivity continues to improve, resulting in the primary coal operators solidifying their market positions.

Jan 1, 1995

By Mark Colwell

As per most other earth science engineering problems, the underground coal geotechnical environment and the way in which roof and rib support interacts with the rock mass are complex issues. While the problem should not be oversimplified (i.e., the dominant failure mechanisms or critical data input parameters should not be ignored), without question judicious simplification is at the heart of all good engineering design. Engineers play a vital role in supplying the world with solutions and products; however it is crucial that engineers make practical and readily useable contributions. One way to ensure this is to employ simplification in the engineering process.

By C. A. Young, J. D. Miller

Thermodynamic data has been obtained for oleate chemisorption at fluorite (CaF2) and calcite (CaCO3) surfaces using adsorption isotherms determined previously at room and elevated temperatures by in-situ Fourier transform infrared/internal reflection spectroscopy (FT-IR/IRS). Linear regression analysis was used to statistically derive free energy data as a function of temperature assuming oleate chemisorption followed Langmuir-type adsorption. Enthalpy and entropy changes were subsequently ascertained from the Clausius-Clapeyron equation and fundamental thermodynamic relationships. Essentially, no difference in the free energy of chemisorption at the two mineral surfaces was found; however, the differences in enthalpy and entropy values were significant. By comparison, the results showed that oleate chemisorption at fluorite surfaces was more extensive and more entropically driven due to more water being displaced. Results correlate well with values determined in the literature for other mineral collector systems. These findings help explain the greater hydrophobic character of fluorite than calcite in both the absence and presence of oleate.

Jan 1, 2002

By B. Valentim

The methodology used to obtain fly ash subsamples of different sizes is generally based on wet or dry sieving methods. However, the worth of such methods is not certain if the methodology applied is not mentioned in the analytical procedure. After performing a fly ash mechanical dry sieving, the authors compared those results with the ones obtained by laser diffraction on the same samples and found unacceptable discrepancies. A preliminary study of a wet sieving analysis carried out on an economizer fly ash sample showed that this method was more effective than the dry sieving. The importance of standardizing the way samples are handled, pretreated and presented to the instrument of analysis are suggested and interlaboratory reproducibility trials are needed to create a common standard methodology to obtain large amounts of fly ash size fraction subsamples.

Jan 1, 2008

By Nathaniel Arbiter

In contrast to pyrometallurgy's 6000year history in metals production, hydrometallurgy is of relatively recent origin. The earliest reference to it was in the 16th century, with the first applications to copper in the 17th and 18th centuries. In the 19th century, increased demands for pure metal resulted in the development of electrolytic refining, and early in this century electrowinning. The rapid growth in copper production in the 20th century, particularly in the United States and Chile, stimulated the development of new technology for leaching and for the recovery of copper from leach solutions. In the past 25 years, solvent extraction has become a major factor by permitting novel leaching technology that produces dilute or complex solutions. In addition, solvents other than sulfuric acid, and chemical methods for precipitating copper metal are now of increasing interest. These are trends that should grow in importance with the need to process lower grade and more complex materials. The evolution of copper hydrometallurgy is reviewed. Key factors in recent major developments are presented with details of specific operations and with trends for the future indicated. The relative importance of copper hydrometallurgy is compared with that of pyrometallurgy in the light of probable changes in ore supplies and character.

Jan 1, 1994

By H. A. Oliveira, A. Azevedo

Physical and chemical characterization and solid/liquid separation of turbid waters from a river affected by an iron tailing rupture disaster (Gualaxo do Norte River, Brazil) were studied at bench scale. Parameters such as turbidity, pH, surface tension, electrical conductivity, total suspended solids (TSS), particle size distribution (micro- and nanoparticles), and zeta potential were analyzed from samples collected at three different river depths. The results in all samples showed the presence of micro- and nanoparticles, ranging in diameters from 100 nm to 200 μm. Best results for flocculation and settling were obtained at pH 7.5, through an innovative combination of eco-friendly reagents: (i) ferric hydroxide precipitates (10 mg L−1 Fe3+) to sweep (enmesh) the dispersed solids and (ii) gelatinized starch (5 mg L−1 ) to form large flocs. The results showed removals between 90 and 100% of total suspended solids (micro- and nanoparticles), resulting in clear water with residual turbidity < 7 NTU. It is believed that this innovative alternative has a high potential for flocculating and treating the turbid water at Gualaxo do Norte River, assisting the water treatment stations.

By H. A. Oliveira, A. Azevedo

Physical and chemical characterization and solid/liquid separation of turbid waters from a river affected by an iron tailing rupture disaster (Gualaxo do Norte River, Brazil) were studied at bench scale. Parameters such as turbidity, pH, surface tension, electrical conductivity, total suspended solids (TSS), particle size distribution (micro- and nanoparticles), and zeta potential were analyzed from samples collected at three different river depths. The results in all samples showed the presence of micro- and nanoparticles, ranging in diameters from 100 nm to 200 μm. Best results for flocculation and settling were obtained at pH 7.5, through an innovative combination of eco-friendly reagents: (i) ferric hydroxide precipitates (10 mg L−1 Fe3+) to sweep (enmesh) the dispersed solids and (ii) gelatinized starch (5 mg L−1 ) to form large flocs. The results showed removals between 90 and 100% of total suspended solids (micro- and nanoparticles), resulting in clear water with residual turbidity < 7 NTU. It is believed that this innovative alternative has a high potential for flocculating and treating the turbid water at Gualaxo do Norte River, assisting the water treatment stations.