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By F. K. Crundwell

The rate of dissolution of sulphide minerals is frequently interpreted in terms of the passivating behaviour of a layer of material on the surface. This interpretation has driven research to identify and possibly remove this layer from the surface, and thus yield higher rates of dissolution. The identification of such layers has proved difficult, with different researchers claiming different compositions for possible layers. An alternative framework has been pursued by the author and co-workers, who have argued that the rate of dissolution is governed by the electronic structure of the minerals which give rise to their semiconducting properties. Researchers sceptical of this approach have argued that semiconducting properties are only important in highly pure substances. In this paper, we review the electronic and semiconducting properties and discuss how they impact dissolution behaviour. These properties affect their colour and dissolution properties even though the minerals are not high purity substances. Keywords: Dissolution, leaching, passivation, semiconductor, chalcopyrite

Jan 1, 2020

By Yuting Xue, Danqing Gao, Brijes Mishra

Heterogeneity and discontinuity significantly affect rock strength. For accurate stability prediction, intact rock behavior is imperatively included in rock mass behavior. However, past research largely used arbitrary scaling approaches to produce rock strength. This paper considers a stochastic approach in order to determine the strength of a rock. Based on the laboratory data, a MATLAB® with extreme value stochastic model generates a database for each physico-mechanical property. Then FLAC® simulates laboratory-sized rock specimens. The grids developed in the numerical model can in turn develop random material properties in MATLAB®, which researchers then applied to the final FLAC® model. Model runs simulate the approach performed in the laboratory. The results from the model indicate that a stochastic approach produces strengths that are lower than a deterministic approach. Failure modes for each specimen are different, similar to observations in the laboratory. In addition, random density also influences the failure mode, highlighting the importance of stochastic analysis in rocks.

By R. V. Ramani, A. S. C. Owili-eger

A mass balance equation can be written for the unit block of Figure 7 for changes within the volume during time At as: [ ] where x and y are the coordinates; q is the flow across any surface; p is the density of the fluid flowing through the medium; qvol is the volumetric flowrate; @ is the medium porosity; and Ax and Ay are the dimensions of the block. The subscripts t and (t+At) denote time levels and At is the change in time. Writing this equation in nota- tional form and on rearranging, the following expression is obtained:

Jan 1, 1974

By J. B. Newkirk, A. H. Geisler

INTRODUCTION CERTAIN of the permanent magnet alloys provide ideal systems for the study of the kinetics of the precipitation reaction and the correlation of structure with properties. One such system, Cu-Ni-Fe, was found by Bradley1,2 to exhibit a coherent transition state in the precipitation process analogous to that reported for Al-Cu alloys somewhat earlier.3 The attractiveness of some permanent magnet alloys for study lies in the fact that vertical sections of the ternary phase diagram in certain regions of composition (Fig I) have as their prototype the binary Ni-Au diagram. Alloys of this type decompose into products that have the same crystal lattice type but only slightly different lattice parameters. The advantages that such alloy systems offer for study over the usual in which an intermetallic compound is formed are many: I. Since the precipitate has the same crystal structure as the matrix, complex atomic movements are not required to form the new lattice. 2. Similarly, complex orientation relationships are not involved for both the matrix and the precipitate would be expected to have the same orientation. 3. Small disregistry of the decomposition products at equilibrium (in contrast with Cu-Ag alloys) is conducive to extensive coherent growth in the transient state and thus the transition lattice can be detected by the usual X ray diffraction methods. 4. Finally, the relative quantities of precipitate and depleted matrix can be varied from o to 100 pct* thus permitting wide freedom for the study of the effect of composition on coherent growth and properties. In the Cu-Ni-Fe alloys of appropriate composition, the face-centered cubic precipitate and also the depleted matrix when first formed are coherent with the parent matrix.1,2 The two have the same [ao] parameter as the original matrix but they are both tetragonal; the precipitate has an axial ratio c/a < I while that of the depleted matrix is c/a > I. When coherency is lost they assume the normal face-centered cubic structure with the depleted matrix having a lattice parameter greater than the original matrix and that of the precipitate less. Such a mechanism would also be expected for Cu-Ni-Co alloys because of the similarity in constitution but this had not been demonstrated. The present investigation was conducted on a Cu-Ni-Co alloy. The constitution diagram and magnetic properties of these alloys have been fairly well established 4,5 however, no previous determinations of mechanism of precipitation and no correlation of structure with properties had been made. Thus, an alloy of this system was chosen for a comprehensive investiga-

Jan 1, 1948

By D. A. Elgillani

Oxidation potentials have been measured in the presence of various concentrations of cyanide, ferrocyanide, and ferricyanide and ethyl xanthate at various values of pH and related to flotation response. Eh-pH diagrams are constructed and show that the formation of surface ferric ferrocyanide is probably responsible for depression when cyanide is added. The influence of cyanide in the depression of pyrite with xanthates as collector has been the subject of many investigations (1,2,3,4,5,6), and from these studies several theories on the mechanism of depression have evolved. Wark and Cox (7) and Gaudin(8) have suggested that the depressing effect is due to a competition of cyanide ion with xanthate ion for the surface. Cook and his colleagues (9,10,11) have explained this phenomenon in terms of competition between hydrocyanic acid and xanthic acid. Sutherland (12) has shown that both of these theories describe accurately the relation between pH value and cyanide addition at constant collector addition but fail to describe the relationship, between pH value and the amount of collector required to cause flotation. Taggart(12) suggested that depression in these systems is due to the formation of a reaction product between ferric ion at the pyrite surface and ferrocyanide ion derived from solution. Majumdar(4,6) has attempted to prove this hypothesis by measuring the contact angles of pyrite in the presence of 25 mg/liter ethyl xanthate and different concentrations of potassium ferrocyanide and ferricyanide. In all cases the contact angles were quite high up to pH 10; these results indicate that pyrite should not be depressed by either potassium ferrocyanide or ferricyanide. In view of these facts, Majumdar has assumed that the compound Fe(CN)2 forms at the surface.

Jan 1, 1968

By Orlando Rojas, Javier Pizarro, Romke Kuyvenhoven, Francisco Soto

"The concept of geometallurgy has been extensively mentioned and used in the mining industry in the past years. However, each mining firm has a different understanding of what geometallurgy means, and its actual value varies significantly from site to site. Even in the case of properly constructed geometallurgical models, it is fairly common to observe a sub-utilization of the model in the actual operation, because of its low production forecasting capability on the short term. This disconnect between the geometallurgical model and operations is typically caused by a lack of tuning between the original model and the actual plant operation. Also, the absence of procedures and other standards for reconciliation, affects the confidence and the predictive quality of the model. The geometallurgical model should consist of three different levels: (I) adequate capture of information, (II) data analysis and modelling, and (III) development of the block model. Once the geometallurgical in-situ model is finalized, a process model should be developed of the plant at industrial scale, in order to scale up the in-situ geometallurgical parameters from their base or standard condition, to the actual operating reality of the plant. Finally, the stage of reconciliation will close this process, assuring that any deviation between the geometallurgical model and the actual plant operation is not due to lack of tuning, but due to operational issues such as unattended maintenance requirements or poor process control in the operation. The methodology as described in this paper has been applied at several large mining sites in Chile. The paper presents the characteristics of the proposed methodology, and quantitatively describes its benefits with examples from actual operations.INTRODUCTIONIt probably is fair to say that geometallurgy became widely used in greenfield projects in the Andes region during the mining boom of the 90’s, when massive orebodies were studied and developed, and upfront metallurgical characterisation proved its use for accurate economic evaluation including estimates of plant throughput, energy consumption, final product quality and overall recovery. A few examples of such greenfield studies for concentrator plants in the 90’s are Minera Los Pelambres (Antofagasta Minerals, Chile), Minera Escondida, Laguna Seca (BHP Billiton, Chile), and Rio Blanco (then Montterrico Metals, Peru). Large size hydrometallurgical operations such as Cerro Colorado, Quebrada Blanca and Lomas Bayas (all in Chile), also recognised early on the importance and value of relating ore mineralogy, geological characterisation and metallurgical behaviour."

Jan 1, 2016

By Naoki Takada, Dae-Sung Cheon, Minoru Sato, Masaji Kato, Manabu Takahashi, Weiren Lin

"The permeability and specific storage of rocks and sedimentary layers deep underground are critical parameters for issues related to the buried evaluation of natural gas and oil, CO2 aquifer storage, various kind of waste storage and so on.The Shirahama sandstone of the Wakayama prefecture, Kii peninsular in central Japan, consists mainly of quartz grains with no cracks and rock fragments that are aggregations of various kind of minerals. The quartz grains have an average size of about 150 micron. The pre-existing pore sizes were distributed dominantly at approximately 1 micron, and the total porosity was about 13%.During the hydrostatic compression test, we measured permeability of Shirahama sandstone by Transient Pulse test for three mutually perpendicular directions. Permeability of Shirahama sandstone remained fairly constant while increasing the effective confining pressure. Permeability anisotropy was observed slightly in the normal and two parallel directions to the bedding planes.We used micro focus X-ray CT with high resolution of 10 micron to visualize and measure the voids space information in Shirahama sandstone. Three-dimensional data were obtained in the intact and stressed sandstone simultaneously. Pore structures and grain boundaries were clearly distinguished. Pore closure and grain movement were clearly observed with increasing confining pressure. Micro focus X-ray CT is an effective tool to visualize and measure the geometrical information in rocks.Three-dimensional medial axis (3DMA) method was introduced to quantify the flow-relevant geometric properties of the voids structure in Shirahama sandstone using µfocus X-Ray CT data. The number of connecting path between two faces, tortuosity and the shortest path distribution within an arbitrary region of Shirahama sandstone specimen were analyzed. Geometrical information on the number of connecting path shows reasonable correlation between permeability anisotropy and mutually perpendicular directions normal and parallel to bedding planes. In addition, we introduced numerical simulation of fluid flow of pressurized Shirahama sandstone by LBM, to discuss the permeability change caused by pressurization on effective confining pressure. We obtained the detailed distributions of fluid pressure and fluid velocity in relatively narrow voids space more than 10 µm. It was confirmed that pressurization effect on permeability caused by the decrease of the connecting path and the shortest path between arbitrary faces, and then caused a complex condition on fluid pressure and fluid velocity."

Jan 1, 2015

By F. Milton Lewis

In this paper an attempt has been made to review the cost trends in producing copper by conventional milling. smelting and hydro-metallurgical means during the last five years. The primary objectives of this cost analysis are to provide a base for future projections as well as to indicate which cost items are more volatile in their influence on overall cost of producing copper.

Jan 1, 1977

By Duk-Won Park

Ground water has been a problem in underground mines (Anon., 1981; Aughenbough, 1973; Stansbury, 1981). Water migrates from water-bearing formations and surface water bodies such as lakes, ponds or creeks into the underground workings through fractures and cracks. As a result, under- ground workings become plagued with the necessity of having the water pumped out in large quantities. Underground workings become flooded when unexpected amounts of water flow into the openings, especially when mines use pillar extraction or longwall mining methods. It is difficult to detect water bodies above the coal mine roof before water problems take place. The resistivity method was used as a method for detecting water saturated rock layers and bodies of water above the roof of a coal mine in northern West Virginia, where the multiple seam mining method was being used.

Jan 1, 1983

By A. Kar, J. Mazumder

"Laser ablation is a process that can be used to synthesize novel nanoscale particles as well as to deposit thin films of various materials. Usually, nanoscale particles and thin films are formed at relatively high and low pressures, respectively, inside the ablation chamber. This paper presents a mathematical model to predict the particle size distribution in the plasma generated during laser ablation. The model is developed by considering the effects of the laser-matter and laser-plasma interactions, the Stefan condition, and the discontinuity across the Knudsen layer. The nanoscale particles are found to be located at the central region of the plasma near the target. The particles have very high velocity and temperature. A good qualitative agreement is observed between the results of this model and experimental data. IntroductionRapid solidification produces novel microstructures whose atomic arrangements and/or chemical compositions are different from those of conventional materials. The conventional materials are either crystalline or amorphous. The crystalline materials have both short- and long-range orders, whereas the amorphous materials have only the shortrange order. The nanocrystalline materials have neither short- nor long-range orders, and for this reason, they exhibit novel properties which are important for synthesizing new materials. The atoms of a nanocrystal can be classified as ""crystal atoms"" and ""boundary atoms"", where the ""crystal atoms"" have the nearest-neighbor configurations similar to the lattice configuration, whereas the nearest-neighbor configurations of the ""boundary atoms"" differ from the lattice configurations 1. Various aspects of the nanoscale materials have been discussed in Refs. [1-7]."

Jan 1, 1994

By H. Miki, S. Wheatley

The addition of precipitated silica greatly enhances chalcopyrite leaching in the presence of sodium chloride at moderate temperatures (65-90°C) in acid media with ferric ions as the oxidant. The beneficial effect increases with the increase in chloride concentration and temperature. The addition of sodium silicate and silica sand has no significant influence. The analysis of solubility data in acid/salt solutions indicates that the solubility of silica as Si(OH)4 as the dissolved species is controlled by the activity of water, as expected from the hydration theory. Kinetic analysis shows the trends that copper dissolution from chalcopyrite in the presence of precipitated silica with sodium chloride follows a shrinking sphere model indicating a chemically controlled surface reaction. The effect of temperature on copper dissolution in the presence of both precipitated silica and sodium chloride was also larger compared to the results in sodium chloride alone. The SEM analysis shows that chloride and silica facilitates the precipitation of sulfur on the surface of the silica particles rather than the chalcopyrite particles which avoids the blockage of the mineral surface and thus improves the leaching kinetics.

Jan 1, 2014

By Reynold Q. Shotts

One often sees in the papers, in these days of ecological consciousness, estimates of the quantity of land that has been "devasted," "ruined," or "destroyed," by surface or strip mining, especially for coal. One feels sure that coal miners must have been the first to discover the art of excavation and that the public didn&apos;t know of its existance until five or 10 years ago! Estimates of the acreage vary widely with most of them sounding somewhat unreal. One estimate of 175,000 acres in Alabama appeared in one newspaper article and the implication was that all of this was mining for coal. The question was raised anew last summer when the author began working on a land use estimate utilizing aerial photographs, a preliminary project to the Alabama Earth Resources Technology Satellite (ERTS) contract presently being fulfilled. One land use category was barren or waste land and aside from some sand beaches in the two coastal counties in Alabama, recently strip mined land constituted most of that category. It quickly became apparent that old stripping was very hard to detect so that estimates from aerial photographs are not accurate. With regard to relatively new stripping, a thin veneer of reflective dirt washed over the countryside may result in a considerable overestimate of the excavated area. Actually, there is a way to estimate the area excavated by strip mining using published Bureau of Mines figures. At least three sets of data are needed: (1) Coal production figures, (2) average thickness of coalbeds mined, and (3) an accurate recovery figure.

Jan 1, 1973

By John A. Organiscak

[Fugitive Just is generated alone unpaved mire reads from intermittent equipment traffic. Typically, the majority of such traffic consists of trucks hauling either mine product or waste [rum the surface mime pit and/or the processing plant. Fugitive dust generated along these unpaved mine roads includes particles of all sizes which become airborne. The potential hazards include the deleterious effects to human health of inhaled dust, traffic visibility hazards and environmental impacts on the localized area by the larger-sized visible airborne dust. Two held surveys were recently conducted to quantify fugitive dust generation and dispersion from truck traffic on unpaved and untreated mine haulage roads For these surveys., airborne glow sampling was conducted at multiple sampling fixations away from an unpaved haulage road at a limestone quarry/plant and at a coal mine preparation plant lo measure the size characteristics, concentrations. and dispersive behavior of the dust cloud generated from truck traffic- Results show that at least 80% of the airborne Just generated by haul trucks was larger than 10 µm- Airborne respirable, thoracic, and total dust concentrations all decreased and approached background concentrations 30.5 in (100 feet) from the road This report describes the average and instantaneous peak dust levels that were measured tip to 30.5m (100 feet) Iron the haulage road. Keywords: Unpaved mine road, fugitive dust, silica.]

Jan 1, 2008

By Fengnian Shi

In the current energy-sensitive world, sustainable development in the mineral industry will require new, better and more efficient processes. Novel comminution methods, which offer the prospect of achieving the required outcomes of size reduction and mineral liberation at lower energy consumption, are continually being sought. In the past five years, extensive research using high voltage pulse electrical comminution technology has been carried out at the Julius Kruttschnitt Mineral Research Centre (JKMRC), in collaboration with selFrag AG. The major outcome of this research is the development of the concept of pre-weakening ore particles by electrical comminution procedures to reduce the energy consumption in the downstream grinding circuit. The research has also verified the preferential liberation of valuable minerals by electrical comminution. Given the advantages, several potential applications of electrical comminution in the mineral industry are proposed, including AG/SAG mill feed pre-weakening, pebble treatment, ball mill feed pre-weakening, early recovery of the liberated valuable minerals, crack/micro crack generation for improved leaching, and smelter slag treatment. For the mineral industry to utilize electrical comminution, two emerging issues identified from the research need to be address. They are the energy consumption by electrical comminution in the locked cycle treatment and the facilities scale up necessary to move this technology from the laboratory to the plant. Keywords: high voltage pulses, electrical comminution, energy efficiency, mineral liberation

Sep 1, 2012

By K. Ananthpadmanabhan

Hydrolyzable surfactants such as fatty acids and amines undergo, in addition to micellisation and precipitation, various associative interactions in aqueous solutions to form ion molecular complexes such as acid-soap, dimers etc. depending upon the solution conditions such as pH. The interaction of these collector species with the mineral surface and with other dissolved species in solution will play a significant role in determining the interfacial processes such as adsorption and flotation. Marked differences in the hydrophobicity imparted to the mineral surface depending upon the solution conditions such as Ph can be attributed to possible differences in surface activities of the above complexes. This aspect of solution chemistry of flotation systems is discussed here for two widely used collectors namely, oleic acid and dodecylamine. Equilibrium species distribution diagrams based on the available literature .data and on estimates of energy of interactions between molecules, have been obtained for oleic acid and dodecylamine solutions.

Jan 1, 1978

By Charles C. L. Smith

A review and comparison is made of the circuitry utilized for dc crane control systems. Anti-parallel three phase full wave thyristor bridges for dc motor reversing and speed control are compared with a single three phase full wave thyristor bridge for speed control and either contactor or static switching for reversing control to obtain complete four quadrant operation for crane material handling. In recent years the Harnischfeger Corporation has developed a solid state adjustable voltage control system to control the speed and direction of dc motors for crane applications and handling materia1.1 Shunt wound dc motors are utilized and speed is controlled in the motor base speed operating region at constant torque by a thyristor, silicon controlled rectifier (SCR), adjust- able armature voltage supply. The three phase thyristor bridge is the power controlling element of the dc adjustable voltage control. ELECTROTORQUE is the Harnischfeger Corporation registered trade name for this type of drive system. By controlling the gating signals or firing pulses to the thyristor bridge SCR&apos;s the dc output voltage can be varied over a wide range. This range is limited only by the magnitude of the ac applied voltage. To obtain operation of the motor in both directions two thristor bridges are connected in an anti-parallel arrangement. A typical schematic for two anti-parallel connected three phase SCR bridges is shown in Figure 1.

Jan 1, 1973

By S Sims, A Stradl, G Hope, B Lacouture

Column flotation cells have been installed in numerous base metal operations around the world. The majority of these cells utilise conventional air-only spargers to introduce air into the bottom of the column. The recent development of instruments to measure the bubble characteristics in these columns has provided a renewed understanding of column behaviour. These new tools provided insight into why the columns at Red Dog Mine had never performed up to expectations. After efforts to optimise the spargers failed to substantially change the bubble size and air efficiency, alternate sparger systems were investigated. The Metso Minerals CISA Microcel sparger system appeared promising and was selected for a full-scale plant trial. The Microcel sparger system was originally developed for the coal industry at the Virginia Centre for Coal and Minerals Processing. In October 2003, a Microcel was retrofitted into one of two 3.66 m diameter flotation columns in the zinc retreat circuit at Red Dog Mine. The operation of the two different sparger systems in parallel allowed a detailed comparison. This paper discusses the performance of the Microcel based on the data collected during several detailed surveys. Bubble size measurements carried out in the pulp zone using the McGill University bubble viewer showed a significant difference in bubble size. The mean Sauter diameter of the bubbles decreased from 3.4 mm for the jetting-type sparger to 1.9 mm for the Microcel sparger. The overall recovery and the recovery by size fraction for both valuable and gangue minerals were compared. Paired t-tests demonstrated that the Microcel column produced a higher concentrate grade (0.6 per cent zinc absolute) and a higher unit recovery (2.8 per cent zinc absolute) than the existing Canadian Process Technologies Inc (CPT) SlamJet column. These improvements provided a payback period of 1.5 months for the $109 000 investment.

Jan 1, 2005

By David A. Zegeer

It&apos;s a pleasure to be here, and an honor to be invited to address this distinguished group of professionals. Today, I&apos;d like to begin with an overview of progress in coal mine safety and health. I&apos;ll discuss some current areas of concern. And I&apos;ll make some suggestions as to where we may be headed in the future. This year marks the coal industry&apos;s 15th anniversary under the Coal Mine Safety and Health Act, which took effect in 1970. We have come a long way in those 15 years. As a coal mining man from way back, I remember the era when the Coal Mine Safety and Health Act first was passed. Some of you may remember it, too. At that time, the safety and health of coal miners was in the public eye even more than it is at present. One reason was a mine explosion that killed 78 miners when it occurred in a large underground coal mine in November 1968. That disaster raised tremendous public concern about protecting the safety of miners.

Jan 1, 1985

By John Starkey

"The development of the Minnovex SAG Power Index (SPI) Test in Canada has created a new and accurate way to measure ore hardness in a SAG environment. Coupled with the standard Bond Ball Mill Work Index Test it is now possible to determine from these two relatively inexpensive laboratory tests, the amount of energy required to grind an ore from the primary crushed size to the desired liberation size. By testing multiple samples to discover where the hard and soft ore zones are located, the representative hardness distribution for the ore body can be determined and grinding equipment selected that is capable to meet production targets for all mining areas of the deposit.In the last century, it was deemed prudent to select up to 50-tonne samples of ore for Semi Autogenous Grinding (SAG) pilot plant tests and a second 5-tonne sample for metallurgical pilot plant work. The methods outlined in this paper show how the 50-tonne sample is no longer required for SAG design because it is better to measure the representative hardness distribution of the ore body than the hardness of a “chosen” representative sample. This is demonstrated to be true by the fact that the lower horizons of an ore zone cannot initially be accessed to recover 150mm pieces, and the bulk samples taken, rarely represent the desired design hardness of the ore. Median hardness will not yield a good result in most cases and a clear understanding of the location and extent of the hardest zones is imperative to achieve a truly successful grinding circuit design.This paper discusses two plants (Kubaka and Agnico Eagle) that have been designed using SPI and Bond with no pilot plant test backup. Both have been very successful in that they can grind design tonnage on the hardest ores in the mine. This guarantees that the mine’s profitability is protected in any mining sequence. It also allows the extra power to be converted to higher throughput on softer ores if additional cash flow is needed. The advantages from the owner’s point of view are dramatic. This procedure will be attractive as well when considering the costs for test work, and the samples for testing. Existing diamond drill core is normally used and this allows the inclusion of data from the deepest regions of the mine. In addition, it is also clear that the decision to use a crusher can now be made at the design stage of a project based on measured parameters and the estimated capital costs of alternative designs."

Jan 1, 2003

By Steffen Schweizer, Tadeusz Brzozowski, Alfred Koller, Michał Topolnicki, Jürgen Wäger, Grzegorz Sołtys

A full scale test has been conducted to determine ground bearing pressure under rig tracks. The track loads were recorded in real time using Liebherr's Ground Pressure Visualisation system, and the vertical stress induced in the ground was measured with pressure cells embedded in the ground. It has been found that the recommendation of EN 16228 regarding determination of the track length is oversimplified. The contact length should dependent on the susceptibility of the working platform. It has been also demonstrated that the corrected pressure distributions under the tracks influence the dimensioning of the working platforms. As a result, the designed working platform may actually be less secure than is shown by conventional calculations.

May 1, 2022