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By Robert D. Norris

Heap leaching provides a method of economically recovering gold from low grade ores with low capital and reasonable operating costs. As with conventional methods, alkaline cyanide solutions are used for leaching. Since gold (and silver) is (are) present as the native metals, oxygen (as air) is required to oxidatively complex the metals with the cyanide. Oxygen depletion can readily occur adversely affecting recovery. The addition of low levels of hydrogen peroxide during leaching can lead to significant increases in both rate of recovery and total recovery. This process allows for the use of shorter pad times or deeper heaps and increases the gold (silver) concentration to the recovery circuit and thus can reduce cyanide losses by virtue of permitting the use of less total leach solution per ton of ore processed.

Jan 1, 1983

By B. A. Wills

Much research effort has been spent in attempting to reduce the high energy costs in grinding, but relatively little in developing methods to enhance the liberation of the minerals from each other. This paper presents some ideas on the nature and role of grain boundaries in mineral assemblies, and their influence on the propagation of cracks through the rock. It is argued that if the mechanisms of fracture are more clearly understood, crack propagation may be controlled in such a way that intergranular fracture dominates breakage, producing less fines and a higher degree of liberation.

Jan 1, 1995

By D. J. Barratt

The application of autogenous and semi-autogenous grinding circuits in recent years has contributed toward substantial savings in capital and operating costs compared to conventional circuits, particularly for large scale copper and molybdenum operations. Such savings have been realized from the deletion of operating, maintenance, equipment purchase and substantial civil/structural costs associated with secondary-/tertiary crushing and screening, fine ore storage and conveying. In spite of the downturn in the copper- moly industry in North America, there is still an interest in autogenous and semi-autogenous grincting for copper-zinc, gold and silver ores and in the overseas market. Both single-stage and two-stage circuits are in operation. Primary circuits operate autogenously or semi-autogenously in either open or closed-circuit. Critical sizes are extracted and crushed for recycle in some cases (e.g. ABC circuit). Secondary grinding is conducted using ball mills or pebble mills.

Jan 1, 1985

Commercialisation of outcomes from research projects is a process often poorly understood and managed, but has the potential to achieve significant benefits for the industry and community as a whole. JKTech Pty Ltd was established in 1986 to transfer viable research outcomes from the Julius Kruttschnitt Mineral Research Centre (JKMRC) at The University of Queensland, Australia. This paper describes successful and unsuccessful examples of commercialisation by JKTech over the years, and draws some conclusions as to the factors that contribute to success and failure in technology transfer.

Jan 1, 2012

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 D. L. Kiser

Conventional and advanced coal preparation technologies were investigated through both a literature search and through direct contact with investigators and developers. In addition to a brief description of each process, performance characteristics including feedstock type, ash and sulfur reduction, thermal energy recovery and cost are provided in a tabular form. Seven of the most commonly utilized conventional coal preparation processes, including those respectively accepting coarse, intermediate and fine coal feed, were reviewed. It was found that certain properly implemented and well maintained conventional processes were capable of better than 75 percent ash removal while recovering 90 percent or more of the inherent thermal energy. Almost 50 advanced coal preparation processes were investigated based on biological, chemical and physical principles. Physical processes investigated included cycloning, homogeneous heavy media, electrostatic, high gradient magnetic, flotation and selective coalescence. Using pulverized coal as a feedstock, some of these processes are respectively reported to be capable of removing better than 95 percent ash. 95 percent pyritic sulfur, and 50 percent organic sulfur while incurring energy losses of less than 5 percent.

Jan 1, 1986

By R. M. Schuster

This study attempts to compare the costs of transporting coarse coal by pipeline, versus the more conventional use of belt conveyors. Hydraulic conveying of crushed (not pulverized) coal has not had widespread commercial acceptance. However, there is little doubt that the technology is available, so that, should this method be proven economical for a given application, implementation of this technology will become more acceptable. Hydraulic transport by pipeline between the mine stockpile and the coal preparation plant, for distances normally considered practical for an overland belt conveyor, should be an ideal application. In this application there is no need for dewatering facilities at the receiving end of the pipeline, because, the receiving screens at the plant serve this purpose. Further, clarified water from the preparation plant can be recirculated back to the mine, a plus for water resource and environmental considerations.

Jan 1, 1982

By McGuirk. C. H.

The Port of Conneaut, long regarded as a leader in advanced bulk material handling technology, recently incorporated into its existing facility a new, multi-million dollar coal transfer-storage system. While the basic principles of conveyorized bulk material handling remain unchanged in the new system, design modifications such as rotary dumping of railroad cars, automated car feed to dumper, belt rip detection for conveyor belting, bucket wheel continuous production, and other innovations make The Pittsburgh and Conneaut Dock Company's complex worthy of classification as the "Port of Tomorrow - Today". The Pittsburgh & Conneaut Dock Company, the "Port of Tomorrow - Today", 1s a bulk materials storage and transfer facility located on Lake Erie, 68 miles east of Cleveland, 30 miles west of Erie, PA., and 138 miles north of Pittsburgh. Figure 1 shows an aerial view of the facility. It is designed to handle over 25 million tons per year of metallurgical and steam coals, direct shipping ore, fine ores, concentrates, pellets, limestone, and dolomite. Inbound shipments of iron ore and limestone are received from Minnesota, Michigan, Labrador, and Quebec. Coal arrives from Pennsylvania, Ohio, Virginia, West Virginia, and Maryland. Rail service is provided by the Bessemer & Lake Erie Railroad Company.

Jan 1, 1980

By J. Kretschmann, N. M. Smith, J. F. Brune, P. Goerke-Mallet

Coal production and coal use for electric power generation are diminishing worldwide. Germany will phase out lignite mining as well as lignite and hard coal-powered electricity generation by 2038. In the United States, coal production has dropped by more than 50% since 2006, including in key coal production states like West Virginia and Wyoming (EIA 2021). Closing mines and power plants across entire mining regions has significant socio-economic impacts. Existing industries must be focused on the post-mining economy by attracting new industries, and implementing job retraining programs for displaced workers, as former mining regions transition towards agricultural, industrial and recreational use. This paper examines the German “exit from coal” under the 17 UN Sustainability Goals and illustrates the complex procedures, interrelationships, risks, and rewards of the transition towards renewable energy sources, including wind, solar, hydrogen, and bioresources.

Mar 2, 2022

By D. E. Ranta, William B. Ryan, Ronald W. May

The Lower Cretaceous McMurray Formation in northern Alberta contains bituminous sands interbedded with other sediments which form the reject encountered during mining operations. Grade prediction is based on a combination of geological interpretation, computer modelling and past mining experience. In addition to estimates for ore, an accurate estimate of "waste" or "reject," are required for Mine Planning. This study investigates the ability of point-kriging using geostatistics, to augment the existing data base of drill-holes in a study area on Syncrude's leases. This approach enables the assessment of potential "worst" case - "best" case scenarios within the context of Mine Planning.

Jan 1, 1992

By Oluwafemi Salami

Conducting full-scale fire experiments in underground mines is difficult and expensive. Sometimes, it is impossible to carry out fire tests in mines due to the danger they pose to mine workers and the underground facilities. However, understanding the potential occurrence of fires in a mine and their dynamics is critical to developing an appropriate emergency evacuation plan, fire suppression, and firefighting techniques. In this study, a numerical fire model using computational fluid dynamics (CFD) with fire dynamics simulator (FDS) 6.7.6 was developed to examine the influence of tunnel bifurcation on maximum temperature beneath a tunnel ceiling. The model was validated using full-scale experimental data. The maximum ceiling gas temperature predicted using FDS and measured maximum smoke temperature during the experiment shows good agreement. The study shows that bifurcation could lower the maximum ceiling temperature of fire-induced smoke in a subsurface environment. The findings from this study apply to the broader field of ventilation and fire life safety in tunnels and other underground environments.

Jun 23, 2024

By R. D. Wunder

The Chino Mines Company, a Kennecott-Mitsubishi partnership, located in Hurley, New Mexico, recently completed a $405 million modernization of its mine, concentrator, and smelter facilities. The mine/ concentrator modernization commenced in 1980 and the smelter modernization began during 1982. Modernization of the mine and concentrator facilities involved increasing the mining rate from 98 kt/d (108,000 stpd) to 152.2 kt/d (167,800 stpd). Ore mining was designed to increase production from 20.2 kt/d (22,300 stpd) to 34.0 kt/d (37,500 stpd). A new concentrator was constructed near the mine using semi-autogenous grinding. The new smelter uses the INCO flash smelting process, increasing capacity by 40.8 kt/a (45,000 stpy) to 99.8 kt/a (110,000 stpy) of salable copper.

Jan 1, 1985

By R. M. Quinlan

The coal industry in the United States has undergone significant economic changes during the past six years. The price of coal remained relatively constant from 1950 to 1969 (See Figures 1 and 2). Steam coal prices tripled and metallurgical coal prices doubled from 1969 to 1974. This price structure has created a new economic environment for coal preparation. Contributing factors to these price trends include: ? Coal Mine Health and Safety Act of 1969 ? Mid-East oil embargo of 1973 ? United Mine Workers of America contract agreements ? Productivity decrease (tons per man-day basis) ? Environmental Protection Agency regulations The increased value of coal justifies additional capital investment in cleaning facilities to optimize yield. Current trends include recovery of existing slurry ponds and recleaning of refuse. Coal preparation plant product yield and quality must be evaluated in terms of the amount of capital expended and cost of operation. Therefore, it is advantageous to optimize the plant product based on clean coal selling price and rate of return on investment.

Jan 1, 1976

By Javad Sattarvand, Amin Moniri-Morad

Predicting equipment failure behavior plays a critical role in providing a safe operation. Although various reliability evaluation methods are available for estimating failure behavior profiles, these approaches are based on mathematical formulation, leading to actual operation simplification and improper estimation of failure trends. This study proposes a discrete-event simulation (DES) approach to model fleet failure behavior. This approach can model the maintenance strategies in multi-component systems with minimum simplifications. In this regard, the first step was to collect a historical failure time dataset (e.g., the time between failures). Then, the DES model is established to predict the severity of failure events and design maintenance strategy considering actual operation circumstances. Afterward, the maintainability analysis was performed to estimate equipment downtime and availability. The achieved results showed that the system availability was about 85%. Also, the findings demonstrated that the DES could efficiently predict the equipment failure behavior using various stochastic events.

Jun 25, 2023

By Rodney R. Krause

In attempting to tell the general public about the coal industry's land reclamation efforts, we have often said, "We're not doing things by the book, because we're still writing it." Like any good catchphrase, the statement is not only striking but true. It is particularly true in the mountains of Appalachia, where the problems of mining; and of reclamation are made more intense by the nature of the terrain. Mining and reclaiming the land "by the book' --which is to say by the methods of contour mining traditionally used in hill country--hasn't worked too well. So a lot of conscientious coal operators and associations are trying new methods--new ways of mining, new machines for seeding and planting, and new species to seed. Not all their experience can be transplanted to other areas, and of course I don't believe that Appalachia is the only place where new methods are being developed. Nevertheless, there's enough action in Appalachia to make a detailed examination rewarding, so let's focus on the hills to see what's new.

Jan 1, 1970

By Norman K. Olson

A geologic investigation of mineral resources in South Carolina first began in 1825 when the General Assembly authorized Lardner Vanuxen to conduct a "Geological and Mineralogical Survey of South Carolina." Vanuxen, South Carolina's first State Geologist, reported in 1826 on the limestones (marble) of the Piedmont which during those early years, were burned in many shall, scattered kilns in the region wherever suitable raw material was available. He also mentioned the possibility of using marl from the Atlantic Coastal Plain province for direct application and enrichment to the soil. Since before the year 1844 industrial minerals in South Carolina have been commercially produced literally from A to Z, asbestos to zircon. The first pub¬lished reports of actual commercial production, not just an occurrence, are referenced in Table 1 for 33 known industrial minerals and rocks in South Carolina. Known or suspected occurrences of undeveloped non-metallic mineral resources in South Carolina await future verification by geologic mapping, sampling (including coring), possible beneficiation, and market analysis. These industrial minerals and rocks include, but are not limited to, special, clay minerals (e.g. bentonitic clays, zeolites and others), sillimanite, argillite (lightweight aggregate), kaolin (alumina) and marl (underground storage and tunneling medium). In addition other non-metallic minerals, once mined but still worthy of reconsideration, include topaz (industrial), heavy minerals, barite, feldspar, and monazite. Finally, possibilities for new reserves, as an expansion of existing mine output, might develop for fuller's earth, limestone (lime), sericite (finely divided mica), vermiculite, kaolin (paper coating and filling, other filler), and metallurgical gravel. Official South Carolina data from the U. S. Bureau of Mines for 1974 indicated a total value of mineral production of $105.2 million. During 1974 production consisted of cam-on clays, (brick and tile), fuller's earth, kaolin and vermiculite

Jan 1, 1977

By Drummond Earley III

The U.S. Bureau of Mines is currently conducting laboratory experiments to study the reactions occurring during in situ leaching of oxide copper ores hosted by biotite-poor granite and biotite-rich granite porphyry. Detailed pre-leach and post-leach petrographic examinations of the rock samples are combined with the leach solution chemistry resulting from core leaching experiments to enable an evaluation of the various reactions which are responsible for the observed fluid chemistry. The information resulting from these laboratory studies is being utilized to support the design of the Bureau's ongoing field research project at the Santa Cruz deposit near Casa Grande, AZ. Atacamite and chrysocolla are the primary copper minerals present in this deposit, and both are readily soluble in the dilute 5% sulfuric acid solutions used in these experiments. In addition to the dissolution of copper minerals, biotite dissolution also occurs during the experiments, contributing K, Mg, Fe, and Al to the leach solution. The biotite dissolution appears to be non-stoichiometric, as it is progressively altered to vermiculite and finally, amorphous silica. While K, Mg, and Fe concentrations in solution steadily increase with time, Al quickly reaches a maximum, and then remains relatively constant for the remainder of the experiment. This suggests that Al saturation is achieved, and this Is supported by the presence of precipitated Al sulfate and aluminosillcate clay mineralization in the post-leach rock samples.

Jan 1, 1990

By Gamal Rashed, Zorica Radakovic-Guzina, Khaled Mohamed

"Underground coal mines use mechanical bolts in addition to other types of bolts to control the rib deformation and to stabilize the yielded coal ribs. Limited research has been conducted to understand the performance of the mechanical bolts in coal ribs. Researchers from the National Institute for Occupational Safety and Health (NIOSH) conducted this work to understand the loading characteristics of mechanical bolts (stiffness and capacity) installed in coal ribs at five underground coal mines. Standard pull-out tests were performed in this study to define the loading characteristics of mechanical rib bolts. Different installation torques were applied to the tested bolts based on the strength of the coal seam. A typical tri-linear load-deformation response for mechanical bolts was obtained from these tests. It was found that the anchorage capacity depends mainly on the coal strength. Guidelines for modeling mechanical bolts have been developed using the tri-linear load-deformation response. The outcome of this research provides essential data for rib support design.INTRODUCTIONThe design of rib bolting in U.S. coal mines is based on a trial-and-error process, which is insufficient to eliminate injuries and fatalities caused by rib falls. In the last 10 years, rib failures have resulted in 17 fatalities, representing 52% of the ground-fall fatalities in underground coal mines in the United States (MSHA, 2018). Recently, NIOSH researchers surveyed 90 sites in 14 underground coal mines in the Eastern United States and found that 11 mines are bolting coal ribs, with 4 of those mines using the conventional mechanical bolts and the others using fully-grouted bolts. NIOSH researchers are developing an engineering design procedure for rib support. Pull-out test programs for mechanical and grouted rib bolts were conducted to understand the rib control mechanisms of rib bolts. Only the test results of mechanical bolts are presented in this paper.Mechanical bolt (or point-anchored bolt) is a tensioned bolt anchored down the borehole with a mechanical expansion shell or a resin-grouted medium (Peng and Tang, 1984). The mechanical anchor bolt consists of a plug, a shell anchor, a headed bar with the top end threaded, a bearing plate, a hardened washer, and occasionally a friction-reducing washer. The shell anchor can be either standard or bail type (Figure 1). The standard type shell is held in place by a nut, while the bail anchor uses a strap to hold the shell in place (Peng, 2008). The diameter of the bar is generally 16 mm (? in) for the #5 bolt or 19 mm (6/8 in) for the #6 bolt. The diameter of the hole that the bolt is inserted into must be carefully controlled, since an oversized hole can result in poor anchorage (Moss, 1971). The anchorage is obtained by applying torque to the bolt head, which in turn pulls the plug down in the shell and expands the serrated leaves against the sides of the hole-wall. In the resin-grouted anchor, the resin replaces the mechanical expansion shell at the end of the hole. The anchorage is achieved by bonding between the resin, bolt, and the hole-wall."

Jan 1, 2019

By Carl R. Christiansen

Underground sites have great potential for industrial plants, for warehouses, and for other purposes where above-surface locations are now employed. Subsurface locations have generally been over- looked by industrial planners even though they may offer many features of superiority over the conventional sites. There are many opportunities for industries or warehouses to go underground. New space can be excavated expressly for this purpose or openings in existing mines may be converted to useful space. Another possibility is the pre-planned mine-industrial site, in which a mineral product is mined and marketed as a commercial venture while utilizing a mining plan which will permit rapid conversion of the openings created into active industrial areas while mining continues in the adjacent ground. An underground plant located in chambers created by excavating space in solid rock has many advantages, including low construction costs, low heating-cooling costs, freedom from storm damage or other surface weather conditions, absence of traffic noise and vibration, fireproof construction, low insurance costs, excellent working conditions, easily controlled temperature and humidity, almost unlimited bearing capacity of floors, low maintenance costs, no effect upon surface.

Jan 1, 1973

By Stephen V. Thompson

Within recent years portable seismic refraction units have found their place in the industry for shallow investigations, Completely portable, relatively inexpensive and of proven accuracy, the portable refraction seismograph is an electronic tool in an electronic age. The age of electronic instrumentation has seen the development of seismic reflection and refraction equipment for deep exploration, especially in the petroleum industry. Large, expensive units, normally truck-mounted and utilizing explosives, are being used successfully for this type of sub- surface investigation. The portable seismograph utilizes the same theory for shallow work as that applied to deep refraction seismology.

Jan 1, 1964