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By D. M. Larsen

Since start-up in 1985, the Cannon Mine has produced and shipped a 170-g/ton (5 oz/ton) gold flotation concentrate to various smelters for gold and silver recovery. Several processes have been investigated to economically produce done' at the mine site from the refractory concentrate. This paper describes laboratory and pilot scale test work used in the process design and engineering. feasibility study of a 73-t/d (80 stpd) pressure oxidation and carbon-in-leach (CIL) facility. The designed pressure oxidation circuit utilizes a series of verti¬cal autoclave units operating at 170°C (338F) and 1.4 MPa (200 psig). Projected operating costs are discussed.

Jan 1, 1993

By Regina N. Tempel, Laurie S. Balistrieri, Lisa L. Stillings, Lisa A. Shevenell, Maggy F. Lengke

Dexter pit lake, within the townsite of Tuscarora, Nevada, has been in existence since 1990 and provides a natural laboratory for the study of cycles of trace elements associated with ore deposits (e.g. As, Cu, Pb, and Se). Our goal in this study is to develop and calibrate methods of geochemical modeling that may be applied to estimating the concentrations and fluxes of trace elements in pit lake systems. Our initial modeling work considers limnology, hydrology, wall rock mineralogy and geochemistry, benthic fluxes, and colloid composition. Results from our work may be useful in evaluating water quality in the arid West.

Jan 1, 2000

By R. Cooper, K. De Wet, A. Janwong

"Horsehead Metal Products is a zinc refinery in Mooresboro, NC, treating crude Waelz oxide (WOX) to produce special high-grade zinc by a hydrometallurgical process comprising leaching, zinc solvent extraction/electrowinning, melting and casting and bleed treatment. Cadmium removal by zinc-dust cementation plays an essential role in the bleed treatment circuit to prevent cadmium buildup in the circuit. Silica, though present at a low level of approximately 0.3 percent in the WOX feed material, had a significant impact on the efficiency of cadmium cementation with zinc dust, most likely due to the passivation of zinc dust particles with silica gel. Solid/liquid separation efficiency by filter press was also affected. To identify the source of the silica issues, silica levels were mapped throughout the circuit, and adjustments, including using pregnant leach solution as the feed to cementation, and pH control in the WOX leaching and neutralization were introduced to mitigate the issues created by silica gel in the circuit. IntroductionLocated in Mooresboro, NC, Horsehead Metal Products Inc. is a hydrometallurgical zinc refinery processing Waelz oxide (WOX) to produce special high-grade (SHG) zinc. The flowsheet, known as the Modified Zincex process, consists of leaching, solvent extraction (SX), electrowinning (EW), melting and casting and bleed treatment (Fig. 1). Cadmium cementation, part of the bleed treatment process, provides an essential bleed of cadmium from the circuit, as metallic cement. The cadmium cementation circuit consists of agitated cementation reactors, a zinc dust addition system, filter presses, agitated purification (releach) reactors and a cadmium concentrate filter press.At the refinery, WOX pulp is leached at a controlled pH to achieve the maximum zinc extraction, according to the main reaction:"

Jan 1, 2016

By Anil K. Ray

Roof falls are one of the greatest hazards in underground coal mines worldwide. Due to stringent safety measures and extensive support system development, roof falls have been reduced significantly but they still persist in many underground coal mines. Some of the roof falls initiate with cutter roof or guttering. In the past, many factors have been identified as being responsible for the development of cutters and roof fall. These responsible factors can be broadly classified as stress related or non-stress related. In this paper the finer details of mining technique have been taken into consideration for better understanding of cutter roof and roof fall problems. Three dimensional finite difference modeling has been used to explain the mechanism of cutter development. Strain softening material behavior has been used to realistically simulate the cutter formation, and common cutting sequences as implemented in the field have been simulated. This was done with an objective to determine whether the cutting sequence has really any significant control over cutter formation or not. In addition to cutting sequences, the effect of cut length is also studied. The effect of step cutting and turning of crosscut into and away from major and minor horizontal stresses is also examined to see its influence on cutter development.

Jan 1, 2009

By L. Diels

About 45% of the contaminated sites are dealing with heavy metal problems. Metals are spread in the environment by mining activities, surface treatment and non ferrous processing. As heavy metals can not be degraded, removal or immobilization (leading to bioavailability reduction) are the only risk reducing measures that exist. The currently best available technique for remediation of heavy metal contaminated groundwater is to pump the contaminated water and to treat it in a wastewater treatment plant installed on the surface. Next to this often used, but expensive, pump and treat technologies, heavy metals can be immobilized by inducing sulfate reducing bacteria (SRB) to transform the sulfates, that are very often present in the same groundwater (due to the metal mining or processing activities), into sulfides. These sulfides will precipitate the metals as insoluble metal sulfides. At the moment several studies have demonstrated the feasibility of this In Situ Bioprecipitation Process (ISBP) for the removal of heavy metals from ground-water as well at lab scale (batch and column tests) as at field scale. However, some questions arise concerning the continuation of the process, the efficiency and the sustainability of the precipitates. The presented study will try to answer these questions. The study is based on more than 10 different studies, all done by the same authors, on different groundwaters and aquifer samples. The presentation will give an overview of the guidelines necessary for a correct and successful bioprecipitation process with stable metal sulfide precipitates. An important question in the ISBP is related to the sustainability of the heavy metal precipitates. It could be observed that the interruption in the carbon source delivery also stopped the in situ bioprecipitation process. Depending on the metal also some release from the precipitate could be observed. It was shown that release can occur with Co and Ni. Aquifers, on which the metals precipitated during the ISBP, were treated in a sequential extraction process under an-aerobic and aerobic conditions. It could be shown that especially under the anaerobic conditions the Zn and Cd precipitates changed from the leachable and the exchangeable fraction to the organic or Fe-Mn fraction (i.e. from the unstable to the stable fraction). The same could be observed for Co and Ni but still some fraction was present under a more available form. On the other hand it could be shown that large differences were observed concerning the heavy metal speciation on the aquifer in function of the used carbon source during the ISBP. The molasses treated systems showed a much more available heavy metal fraction on the aquifer compared to the lactate or HRC® treated groundwater. The different speciation forms based on the use of different carbon sources will be discussed in detail. It will pay attention to the influence of the carbon source, the efficiency of the induction of the bioprecipitation process, the influence on the competence between sulfate reducers and methanogenic bacteria and the influence of low pH on the ISBP. It seems that acetate, which is also a degradation product of fermentation of some carbon sources, can inhibit some sulfate reducers. Also the relation between slow release compounds and immediately available compounds will be explained. Finally a pilot study will be presented showing the problems that can be encountered during this process. Focus will be put on the induction of the process, the keeping on of the process and the follow up of the process by the installation of in situ mesocosm socks. These results will allow the correct implementation of the ISBP with an eye on longevity and sustainability of the process and present the ISBP as a much more sustainable alternative to the pump and treat technology as measure for heavy metals contaminated groundwaters.

Jan 1, 2006

By Yuexin Han

The characteristics of comminuted hematite products using a high pressure grinding roller (HPGR) and conventional jaw crusher (JC) were comparatively studied by screening, optical microscope, scanning electron microscope (SEM) and Brunauer, Emmett and Teller (BET) techniques. Major properties investigated included product size distribution, particle cracks, specific surface areas and pore volumes. Results showed that in a closed-circuit operation with a screen opening of 3.2 mm, the HPGR and JC gave a similar P80, but the HPGR achieved a more uniform size distribution, more fines and a higher crushing efficiency. Three modes of cracks were identified, namely transgranular cracks, innergranular microcracks and intergranular microcracks. Transgranular cracks originated from shearing breakage. Innergranular and intergranular microcracks were generated by HPGR via the two main nonrandom breakage forms, preferential breakage and interfacial breakage, depending on their respective ability to endure stresses when mineral phases (particles) were loaded against each other. The BET values for the same-size fractions showed that HPGR products gave higher specific surface areas and more pore volumes than JC products. This indicates that HPGR-crushed products are easier to grind because of their high porosity and extra cracks.

May 1, 2012

By R. R. Klimpel

This paper is a summary of the author's industrial experiences on the selection and optimization of flotation reagent schemes for the recovery of gold species. The trends given are a composite of data and experiences gained on 24 different gold ores from around the globe. The primary emphasis is on the benefits of matching the associated gold mineralogy to a reagent scheme most appropriate for that mineralogy. Two general categories are discussed: the flotation of free or native gold species and the flotation of gold associated with a variety of sulfide minerals. Important plant operating factors influencing each of these two categories are presented with supporting examples. Carefully matching reagent chemistry and appropriate operating conditions to any given gold-bearing ore will not only lower the total reagent cost but, more importantly, can lead to measurable increases in gold recovery.

Jan 1, 2000

By Paul F. Gnirk, Ralph A. Wagner, Joe L. Ratigan

This thermomechanical analysis used the finite element method to investigate the behavior of crushed salt backfill in a waste disposal room situated in a salt dome repository. The first of two objectives was to determine the transient temperature rise and degree of thermomechanical consolidation that occur in the backfill as a function of drillhole depths. The second objective involved the evaluation of closure due to salt creep of unlined emplacement drillholes and the determination of pressure on steel sleeve liners in the drillholes should liners become necessary for canister retrieval. The retrievability period was considered to extend for 25 years after waste emplacement. The canisters were assumed to contain ten-year old high level waste with a thermal output of 4.3 kW at the time of emplacement.

Jan 1, 1981

By Z. Hyder, M. Karmis

Underground or In-situ Coal Gasification (UCG or UICG), though not a new concept, is now attracting considerable global attention as a viable process to provide a "clean" and economic fuel from coal. Applying improved UICG technology to gasify deep, thin, and low-grade coal seams could vastly increase the amount of exploitable reserves. However, it is imperative that further development of this technology is based on integrating UCG practices and potential environmental impacts with accepted sustainability frameworks and processes. This paper evaluates the potential of UCG to conform to frameworks such as MMSD (Mining, Minerals and Sustainable Development), Natural Step and Green Engineering, in order to define its "sustainable" potential. The paper also discusses the potential contributions of UCG to sustainability during its design, operation, closure, and post-closure phases.

Jan 1, 2011

By S. J. Porter, M. T. McRae

The Melbourne City Link project includes two three-lane highway tunnels, 1.6 and 3.4km long, respectively, which are both approximately 16 meters wide and 9 meters high. The tunnels will be excavated through interbedded, moderately to highly jointed siltstones and sandstones of the Silurian Age Melbourne Mudstone formation over the major parts of their lengths. The strength of the intact rock varies from less than 5 MPa to greater than 70 MPa. Based on the available information regarding the performance of large span tunnels in weak rock, it was considered that the commonly applied empirical design guidelines for tunnel support, based on rock mass classification systems, should be augmented by more explicit design methods. The support design was, therefore, validated by analytical procedures, including numerical analyses, which are described in this paper.

Jan 1, 1997

By Clement K. Chase, Manuel R. Lastra

Introduction The choice of using a dump or heap leaching process or a fine grinding-agitation leaching process is based on the grade and tonnage of the ore body. Low grade ore and small tonnages are best treated by a low-cost method, such as dump or heap leaching. Permeability, however, is the critical factor in a successful leaching operation, regardless of tonnage or grade. Without permeability in the leach bed, no percolation, no dissolution, no extraction, and no success are possible. Solution delivery to the ore is also essential. Solute-to-mineral contact is a requisite. The solute must be effectively strong and not be depleted in active dissolvers, such as acid, ferric iron, cyanide, and oxygen. It must also be moving across the mineral to be dissolved. No pockets of stagnant solution can be allowed. A third factor is recovery of the now-dissolved metal in the pregnant liquor. All such liquor should be gathered at a reasonable metal concentration to make further pumping and processing worthwhile. Control and recovery of pregnant solutions are probably the most ignored factors of solution mining. This stage in recovery is historically where many operations either fail or become viable. Permeability A permeable heap is normally achieved by taking into account heap building/construction and agglomeration/pelletizing. Even though heap building is critical for good permeability, it will not be discussed here. It has been described in detail by others. Instead, this analysis will concentrate on agglomeration and pelletizing. Differences between agglomeration and pelletizing are emphasized. Agglomeration is referred to when small particles are being attached to larger particles -the ore presents a complete size distribution. On the other hand, pelletizing is a process where all particles are fine (less than 850)µm or 20 mesh), as with mill tailings. The difference is important from two points of view: • Mechanical devices used to achieve the desired attaching action; and • Binder dosages. Mechanical Devices Due to the absence of large particles that fines can become attached to, pelletizing should be done in a centrifugal-action-based device, such as an inclined rotating plate, a rotary drum, or a series of belt-transfer points. In agglomeration, large particles play a part as a natural nucleus for the attaching action of fines. Hence, a tumbling action as strong as for pelletizing is not required. Common methods to accomplish agglomeration include: • Cascade belt system with either all belts moving forward or some of them moving forward and at least one moving backward; • Combination of belt plus inclined vibrating chute; • Large concrete mixer drum; and • Belt discharging directly onto stockpiled ore. The proper agglomeration system will depend basically on the size distribution of the ore and the amount and type of clays present. In all of the agglomerating systems described, the tumbling action takes place at the transfer points either from belt to belt, or from belt to inclined chute ore belt to ore pile. Usually, two or three mixing bars at each transfer point are also included to help the mixing action. Plows to move the ore around on a moving belt are also used.

Jan 11, 1984

The advantages of quantitative environmental risk assessment techniques over the more commonly used qualitative approach is widely accepted. One important parameter related to the level of risk is the extent and geographic spread of pollutants. Geographic Information Systems (GIS) provide a powerful and highly flexible tool that increases the sophistication of the risk assessment methodology. Through spatial representation, the estimated risk becomes more comprehensive, thus facilitating the decision making process. In addition, valuable qualitative information can be incorporated into the risk assessment procedure with the help of GIS. This paper illustrates a methodology for quantifying risks posed to human health, by exposure to contaminated land, in a manner, which gives a measure of the uncertainty in the assessment and preserves the spatial distribution of the risks. The case study utilised to illustrate the methodology is a large industrial area around a number of decommissioned minerals production and processing sites with known high heavy metal loads at Lavrio, Greece. The spatial distribution of Pb concentration in soils was derived from 425 soil samples collected over a total area of 120 km2. Indicator kriging was used to quantify the spatial distribution of the risk and related uncertainty and the results displayed in map form using GIS.

Jan 1, 2003

By G. J. Melvin

Mines the world over tend to face a common range of problems. They begin life by trying to determine if there is sufficient product, usually under tons of earth, of sufficient quality to justify the operation. Once such a determination is made the mine must then be planned and brought into operation. Once operating most mines find that they are far away from suppliers, using very expensive equipment. Hence the three most common mining problems are, what does my ore body look like and how can it best be mined, how can I get sup- plies to my mine in the most cost effective way, and how do I control the vast dollars required to keep it all operating. Mincom started life by providing technical mining software to address the first of these problems and was very successful, particularly in the coal mining industry. However the company soon realized that if it was to become a significant provider of mining industry software it must also address the other major problem areas. Hence started what is now Mincom's largest business which is the provision of fully integrated mine management software with strong emphasis on materials and maintenance management to control costs. Mincom not only supplies the software but also provides a comprehensive implementation package using its own staff of experienced mining industry specialists. This papaer highlights some of Mincom's international implementation experiences.

Jan 1, 1989

By C. Newman, R. C. Ray

Originated and developed in the civil tunneling industry, the Ground Reaction Curve (GRC) has provided a robust methodology for evaluating and designing ground support in both tunnels and underground mining scenarios. This paper presents a preliminary assessment in the utilization of the GRC concept for the evaluation and design of the pillar-support system with respect to overburden stress and displacement. This initial assessment will be based on and backed by past research on this topic. Underground mine instrumentation is planned for a longwall mine in the Appalachian coal field based on the research and findings in this paper to support the postulated hypothesis. INTRODUCTION Since the early 1970’s, the mining industry has evaluated the structural stability of a pillar by dividing an approximated pillar load by an approximated pillar strength. While this design methodology has served the industry well in the past, as modern mining operations continue to develop in more complex geological and geometric conditions coupled with market economics, industry professionals are in dire need of a modified stability assessment approach which considers both the stress condition and material displacements. Within the civil tunneling industry, the GRC approach has been successfully utilized in designing underground support measures that enhance the stability of an underground excavation. Through the incorporation of current industry knowledge and understanding of ground and support behaviors this paper looks to investigate into preliminary assessment for the development of a Modified Support Response Method (MSRM) to further improve the analysis of local and global underground stability. CURRENT PILLAR DESIGN METHODS AND THEIR LIMITATIONS Globally, multiple pillar design methods have been utilized in the design of underground excavations. Each of these methods approaches the calculation of pillar stability a little differently with respect to material properties, underground geometries and stress conditions. Analytical solutions can be used to determine the strength of homogeneous materials like concrete, but not in case of non-homogeneous and non-isotropic mineral deposits in a mine. These equations are often derived using empirical methods. Pillar strength is defined as the maximum resistance of a pillar to axial loading (Brady & Brown, 1985). The strength of mine pillars is typically estimated through indirect methods. In the past, researchers have correlated the strength of a given size and width of a rock specimen to the strength of a mine pillar. The first study on the effect of geometry on rock strength was done by (Bauschiger, 1876) on Swiss sandstone samples. Since then several empirical equations to determine pillar strength had been published by many researchers like (Bunting, 1911), (Griffith & Conner, 1912), (Greenwald, Howarth, & Hartmann, 1939), (Holland & Gaddy, 1957), (Evana, Pomeroy, & Berenbaum, 1961) and (Holland C. , 1964).

Jan 1, 2019

By G. Milojcic

The opencast lignite mines in the Rhinel and Di strict/Germany are equipped with the continuously operating bucket-wheel excavator - conveyor - spreader system. High productivity requires large capital expenditure on main mine equipment as a precondition for efficient mining. In operation, the technology employed leads to a particular cost pattern which is quite different from that of other industries. Labour, auxiliary equipment and mobile vehicles are the most important cost factors which can be controlled by the management. In this respect information processing computer systems are used for systematical and interpretable representation of operational tasks and jobs both in planning and work preparation and in recording the operational data describing the work result and the use of resources. Another aim of the project is to relieve the middle management of major part of its administrative routine work. Job-related work planning and data recording open up various possibilities of analyzing the operational procedures. This analysis shows, for example, what auxiliary machines are particularly suitable for specific tasks, and working groups can be organized so as to take account of the different skills of individual employees for the sake of an optimal work product. Computerized information processing provides the decision makers with topical information related to their respective responsibilities. The mining department of the Hambach opencast mine is the first user of the PERMAD system. Due to the favorable evaluation it has been decided to introduce PERMAD in three other mines in the course of 1992/93.

Jan 1, 1992

By Tim Neil, O&apos

Copper price rebounds A worldwide scramble for diminishing supplies of copper has pushed the red metal's price to more than $2.20/kg ($1 per lb), the highest level since 1980. The first nine months of 1987, world copper production was down 1% from a year ago, while consumption rose 7%. Demand has been fueled by economic strength in several countries, particularly Japan, South Korea, and Taiwan. The price has also been helped by interest rate declines that have prompted manufacturers to build up inventories. In addition, China is expected to be a major buyer in 1988 as it stocks up for its five-year industrialization plan. There appears to be no sign of any significant increase in copper supplies until later 1988 or early 1989. This means supplies probably will remain tight for some time even if world economic activity slows. Strikes and other production problems slowed world output of copper in 1987. As a result, copper supplies are the lowest they have been in 14 years. World inventories currently total 625 kt (690,000 st). That is not much above the 585 kt (645,000 st) level reached in 1974 when the price of copper rose to a record $3.84/kg ($1.74 per lb). This makes all the more interesting what Chile, the world's largest copper producer, has been doing lately. Chile has been the world's largest copper producer since 1982, when it overtook the United States. Table 1 shows Chile's copper grades, reserves, and production at its mines. Chile contains roughly one-fifth of the world's copper reserves. At present production rates, these reserves would last for more than 100 years. In 1986, Chile produced 1.4 Mt (1.5 million st) of fine copper, up 3%. Chile accounted for 17% of the world's copper output.

Jan 1, 1988

By S. Acar, P. Somasundaran

Results of selective flocculation of natural ores containing two or more minerals and of synthetic mineral mixtures do not usually agree with what is expected on the basis of the results from single mineral tests (Acar and Somasundaran, 1985). This is mainly due to the ionic species released by the minerals, which act differently under different pH values. The objective of this investigation was to study 1) the surface chemical composition of selected sulfide minerals-natural chalcopyrite and pentlandite and synthetic covellite, millerite, and pyrrhotite-and 2) the changes brought about by the dissolved mineral species. Electron Spectroscopy for Chemical Analysis (ESCA) was used to perform the surface analyses.

Jan 1, 1991

By Graham Taylor, Mandy Agnew

Hardpans developing in tailings storage facilities (TSF) in Australia have been investigated in relation to Acid Rock Drainage (ARD) generation. This research had three main aims. Firstly it was to obtain an understanding of the physical and chemical characteristics of tailings residues which support the in-situ formation of cemented layers and hardpans. Secondly it was to examine how effective hardpans are at reducing ARD generation, and thirdly it was to investigate the promotion of hardpan formation to inhibit ARD and pollutant generation. This paper presents the data collected during investigations into the effectiveness of hardpans to reduce ARD generation. Three basic types of hardpans have been identified and examined: laterally extensive surface hardpans, laterally extensive cemented layers; and laterally discontinuous hardpans developing in locations of seepage. Their mineralogy, morphology, lateral extent, depth and rate of formation are dictated by sulfide and gangue mineralogy and content, milling and depositional techniques of the tailings and the climate. As the sulfides oxidise, acid and heavy metals are generated, while gangue mineral degradation is enhanced, adding to elemental loads. These liberated ions are then available for precipitation of secondary mineral cements through concentration during evaporation. In TSFs where hardpan development is restricted by mineralogy, grain size or climate, hardpan formation can be enhanced in seepage zones (eg. seepage from waste rock dumps) where tailings are exposed to seepage waters laden with heavy metals and sulfate. The effectiveness of hardpans in the inhibition of ARD generation is dependent on reducing oxygen diffusion and water infiltration into the underlying tailings. A reduction in water infiltration will diminish the transport of contaminants developed during sulfide oxidation and subsequent reactions. Water and gas movement through the hardpans at the CSA (Cu, Zn, Pb) and Elura (Pb, Zn, Ag) mines has been investigated. Permeability tests indicate the hardpans have reduced the infiltration rates by 10 to 100 times that of the fresh tailings. Oxygen diffusion rates were calculated and were shown to be up to 1000 times lower in hardpans than in fresh tailings. Such decreases are explained by persistent elevated 'degrees of saturation' within the hardpans. These conditions were verified using a conceptual model of sulfide oxidation reactions, which allowed comparisons of diffusion coefficients with modelled and observed depths of oxidation within the tailings impoundments.

Jan 1, 2000

By Larry Lynott

This paper summarizes the benefits ofusing an in-situ analyzer in a sampling and valuation program. The tests and studies cited quantify the problems associated with current conventional sampling techniques and contrast conventionally-obtained results with those obtained through in-situ analysis. Data are presented to show the improved precision in valuation resulting from the in-situ method. Greater precision in estimating the mineral content of unmined ground becomes increasingly important as mines strive for optimum exploitation of their deposits. As the following analysis shows, the variable distribution of minerals within a deposit, along with the difficulty and the cost of high density sampling limits the precision which is currently possible in practice. An inherent problem exists in the conventional method of sampling. The erratic values of ore grade necessitate the collection oflarge numbers of samples for statistically accurate valuation and ore reserve estimation. Owing to the cost of manpower, current sampling techniques do not allow for the collection of sufficiently large numbers of samples. The most common method of sampFng in current practice is chip sampling, although bulk sampling is sometimes used. The intent of sampling is to obtain an estimate of the value of blocks of ground prior to mining. This information is used to plan the rate and sequence of mining, yet the sampling intervals which are possible in practice cause these block estimations to be ubject to considerable uncertainty. This inevitably leads to mcorrect mining decisions which may be vy costly.

Jan 1, 1998

By M. K. Larson, R. G. Wade

Researchers at the National Institute for Occupational Safety and Health (NIOSH) are studying the time- dependent response of rock stressed along weakness planes. The objective is to improve mine safety by reducing the number of roof falls that cause injuries and fatalities to miners. Researchers conducted direct- shear tests on mudstone overcored from a coal mine roof. Results showed frictional strength weakens with displacement along the shearing planes. Results of direct-shear creep tests also showed time-dependent deformation. Test measurements were compared to classical analytical models. Results suggest that the risk of roof collapse may be decreased through layout and support design to reduce creep rates and thus slow progression toward failure.

Jan 1, 2002