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By G. Castillo, J. Mortensen

"INTRODUCTION Molybdenite is typically produced as a co-product in the copper ore flotation process. At the Rio Tinto Kennecott Concentrator (RTKC) in Copperton, Utah, the molybdenite is initially floated with copper sulfides and other value minerals producing a Cu-Mo concentrate. This is then separated in the molybdenum plant by depressing copper sulfides and pyrite and floating only molybdenite. The molybdenum plant in RTKC comprises the rougher circuit and several stages of cleaning to achieve a certain grade requirement of Mo. The rougher circuit is where the first stage of separation occurs. Cu sulfides and pyrite are depressed in the rougher circuit by adding NaSH under nitrogen and in the cleaner circuit by adding NaSH under air. The depression of Cu sulfides (and pyrite) by NaSH is related to the redox activity1. It is important therefore to maintain a reducing potential in the circuit in order to achieve effective Cu-Mo separation. If the rougher circuit is under air, like RTKC’s molybdenum cleaner circuits, it is harder to maintain the target redox potential because NaSH oxidizes rapidly in the presence of air thereby increasing NaSH consumption significantly. CU-MO SEPARATION AND ROLE OF PULP POTENTIAL The collector adsorption on copper sulfide minerals is through an electrochemical mechanism2. The collector changes the surface chemistry of the Cu mineral allowing it to float. Molybdenite, or MoS2, on the other hand, floats readily in the presence of a frother as it is naturally hydrophobic. Usually, hydrocarbon oil extenders such as diesel or burner oil are added to enhance Mo recovery. In order to effectively separate Cu from Mo, the collector complex on the copper surface needs to be destabilized or desorbed using a reducing agent such as NaSH or Nokes. As long as the circuit is under highly reducing conditions, the collector remains detached from the sulfide mineral surface allowing Cu sulfide depression. Therefore, it is important to measure the oxidation-reduction potential (ORP) continually and maintain the reducing condition with addition of NaSH. For a given collector each mineral will have a characteristic potential or electrochemical window for flotation to occur3, therefore, it is necessary to reduce the potential outside of this window in order to effectively separate Cu and Fe sulfides from MoS2 minerals2. In RTKC plant, the target reducing condition is between -450 to -550 mV to effectively destabilize the collector and depress Cu and Fe minerals. Typically the dosage of NaSH used in the molybdenum plant could range from 6 to 30 gallons/min (gpm). The high dosage of NaSH could pose risk of H2S exposure. RTKC wanted to evaluate alternatives to NaSH in order to reduce its consumption and minimize risk of H2S gas generation."

Jan 1, 2016

By Thomas J. DeMull

Heap leaching was introduced to the precious metals mining industry approximately two decades ago as a simple, low cost method for recovering gold and silver from ores. Since that time, operational experience has contributed to knowledge and understanding of the process, making it a reliable alternative to conventional milling processes for low grade ores. At time of this writing, dozens of heap leach operations are active producing hundreds of thousands of ounces of gold and millions of ounces of silver annually. These successes have caused the popular press to acclaim heap leaching "high-tech" gold mining, but, despite the hype, the process remains a simple one. An example of simplicity in heap leaching is the operation established in 1986 at Amax Gold's Sleeper Mine. Starting with a simple goal, namely to produce gold from sub-mill grade ore at low cost, heap leaching was rapidly implemented at Sleeper; only five months after testwork started, leaching commenced on the first commercial scale, 50,000 ton heap of low grade ore. Sized at 600,000 tons per year to produce 10,500 oz gold per year, the low grade heap operation has performed beyond expectations. During the first year of production, 881,800 tons have been leached producing 15,665 oz of gold and 35,528 oz of silver. Operating ·costs for the first year have averaged $112 per oz gold produced ( or $95 per oz if silver credit is included). Successful implementation of heap leaching at Sleeper has had a dramatic impact on ore reserves and future operations.

Jan 1, 1998

By M. Akser, M. Tomas

Six Sigma is a methodology that uses a structured and disciplined approach to improve process performance (higher throughput, better recovery, lower cost, shorter cycle time, etc.). Specially trained people called “black belts” lead and manage Six Sigma projects. Black belts, with assistance from their team, ensure that projects follow the DMAIC (define, measure, analyze, implement and control) process phases. Timely completion of each project, with measurable deliverables, is key to Six Sigma’s significant financial success. Implementation of Six Sigma has been growing in recent years in a wide range of industries. The heavy mineral industry, like many other industries, could benefit from what Six Sigma has to offer. Specific Six Sigma project examples are included from DuPont’s Heavy Mineral Production Plant in Florida.

Jan 1, 2005

By John Nadolski

Intensive hydrologic monitoring of the Powder river basin has been on-going since the early 1970's. Data were used in environ- mental assessments and for determination of hydrologic consequences associated with coal mining activities. For most coal mine operators, data collection has continued in this baseline mode with little or no statistical analysis of the data and with no statistical procedure established to detect changes in groundwater quality. For the past four years Powder River Coal Company has studied several statistical techniques to analyze groundwater quality. Three objectives were pursued: 1) to determine the baseline water quality for key aquifers; 2) to determine which wells could be deleted from the monitoring program without reducing monitoring effectiveness; and 3) to define a statistical test to determine water quality changes. Knowledge of the regional geo-hydrologic system was combined with an analysis of the water quality monitoring in order to identify homogeneous aquifer zones. All wells within an aquifer zone were treated as one population, and a t-test was used to determine the minimum number of samples needed to define the water quality for each aquifer zone. Results indicate that the data for each aquifer zone were nor- mally distributed and that groundwater quality could be defined using a fairly small number of samples. Because of the minimum sample size test, groundwater quality sampling was reduced by between 75 and 85 percent.

Jan 1, 1989

Newmont has been producing gold from the Carlin Trend for over 45 years. Naturally the focus, scale and complexity of the operations have changed considerably over this time. Newmont discovered and developed the Carlin Main ore body which is located about 32 km (20 miles) north of Carlin Nevada. The property was developed as a one mine one gold mill treatment plant operation which produced about 6,200 kg (200,000 Troy ounces) of dorè gold bars per year. The initial mine, mill and gold refining facilities were relatively small in comparison to today?s standards. The milling circuit used the Merrill-Crowe zinc precipitation process to recover dissolved gold and prepare a concentrated precious metal ?precipitate? to be melted into a dorè bar for sale.

Jan 1, 2012

By M. Kane, O&apos

BHP Iron Ore initiated research programs in January of 1995 to develop long term plans for decommissioning of the waste rock material at their Mt. Whaleback operation. More than 2 billion tonnes of waste rock were deposited during the past 30 years. Ultimately, the operators will deposit a total of approximately 5 billion tonnes in waste rock dumps constructed near the open pit. The Mt. Whaleback operation is located in a semi-arid climate adjacent to Newman, Western Australia, approximately 1200km north-northeast of Perth, Western Australia. The primary research program includes the development of technology for the long term performance of the waste rock dumps with respect to vegetation, slope stability, surface runoff, erosion, and water infiltration. This paper focuses on the design and implementation of a cover system to prevent water infiltration to the underlying waste rock. A laboratory program and the soil-atmosphere modelling completed to design the horizontal field test plots are described. The construction of the horizontal surface field test plots are discussed together with the field instruments installed to monitor performance. The key components of the instrumentation program are the design and installation of large scale field lysimeters to measure the unsaturated flow of moisture into the waste rock from the base of the cover layer. The cover system is designed to maximize infiltration during wet periods for subsequent evapo-transpiration while minimizing surface runoff. The result is a near zero net infiltration to the underlying waste material. A key feature of the design is the use of pit run waste material as the cover material. Monitoring is in progress and will continue for at least two annual wet/dry cycles. The optimum cover system should minimize the net infiltration of water to the underlying waste rock while maintaining physical and ecological integrity for long term performance.

Jan 1, 1998

By S. K. Singh, P. R. Sheorey

To meet increasing demand of coal, underground mining is largely being replaced by the exploitation at deeper horizons and with greater complexities. The exploitation-proposition may be below not-to-be-disturbed surface properties or below water-bodies, posing a constant threat of inundation. Also, the mounting pressures to limit the adverse impacts on the environment bring the extraction-undertaking to face more challenges. An understanding of subsidence-mechanism and a rational quantification of subsidence parameters is a requisite herein. This paper presents such pragmatic quantification, validated at mine-sites in India. In comparison, better productivity, conservation and safety is ensured in this approach.

Jan 1, 1999

Diesel powered machines are doing some specific operations in the cyclic order required by the technical process. The dynamics of this process in certain conditions has an essential influence on environmental health conditions in the working area. The main purpose of this paper is to show, using computer simulation, how the movement (dynamic) of diesel vehicles effects environmental health standards and also how to determine the required air quantity for ventilation.

Jan 6, 1985

By Timothy O’Rourke, Karrie Buxton, Chris Lynagh, Daniel Dobbels, Frederick Vincent

The Doan Valley Storage Tunnel Project in Cleveland Ohio was constructed to control Combined Sewer Overflows (CSOs). It is a complex system of three tunnels ranging from 8.5 to 18 feet in diameter with a total length of about 2.3 miles that was put into operation in mid-2021. The project lies within and below the cultural, educational, and medical hub of Cleveland, which presented unique design and construction challenges. This paper provides a case history of the design and construction, with particular attention given to lessons learned in devising a large tunnel system that can carry both dry and wet weather flows constructed in rock with limited cover, within a flood plain area and vibrant urban center

Dec 1, 2022

By John W. Ahlrichs, E. Daniel Baker, Erich U. Petersen, William J. Tafuri, Douglas N. Halbe

The combined Bootstrap and Capstone deposits, located in the Bootstrap subdistrict (Section 10, T36N, R49E, M.D.B.M., Elko County, Nevada), are approximately 27 miles northwest of Ca-1I: Nevada. The contiguous Bootstrap Capstone deposits are located along the northeastern and northern flanks of Round Mountain, a horst block separated by grabens from the sheep Creek Mountains to the north-northwest and the Tuscarora Mountains to the east. Open-pit-minable gold reserves as of December, 1989, were 13.27 million short tons with an average grade of .057 troy ounces gold per ton and an overall waste-to-ore strip ratio of 2.5:1. Ore zones in Bootstrap are concentrated along north striking high-angle dikes localized along faults, while ore zones at Capstone are strata form and structural, occurring at the Devonian limestone/siliceous sediment interface and in high-angle fault-filling dikes. Pre-ore faulting produced a complex structural setting for Capstone, dominated by strong northwest fault sets cross-cut by northeasterly structures. Alteration associated with both deposits is silicification with a-strong argillic overprint. Dike emplacement, which post-dates silicification, marked the onset of mainstage gold deposition and argillic overprinting of silicified lithologies. Gold displays an affinity for moderately argillized sedimentary and igneous lithologies. Mineralogic and geochemical analyses of rotary percussion drill samples show good correlation between gold, silica, antimony, and arsenic.

Jan 1, 1990

By A. W. Fletcher

A nickel-copper sulphide concentrate was treated in a pilot plant at Warren Spring Laboratory during 1961, by a hydrometallurgical roast-leach- solvent extraction process devised to cleanly separate the metal values, and produce acid sulphate liquors containing the metals. It is shown that 86 percent of the nickel and 95 percent of the copper could be leached from the calcine, after a sulphatizing roast on finely ground flotation concentrate. Iron was removed from the leach liquor by limestone neutralization with a small loss of values. Copper and nickel were separated by solvent extraction with naphthenic acid in kerosene after partial neutralization of the iron-free liquors with ammonium hydroxide. Hydrogen sulphide and chlorine were used to remove zinc (and residual copper) and cobalt impurities respectively. The recovery of pure copper and pure nickel, by electrowinning, from the acidic solvent extract strip liquors finally produced, appears technically feasible.

Jan 1, 1964

By Herschel H. Potter

While preparing this paper, I soon realized I had a problem in defining what injuries should be classified as "personal." Admittedly, in some cases, falls of persons, sprains and strains, pulling and pushing injuries, and back injuries may have been caused by the individual. But, I believe the number of injuries directly attributed to an individual's carelessness is relatively small in comparison to the total number of injuries in those categories. For discussion purposes, the injuries most often considered to be personal, that is, caused by individuals are those classified as back injuries. My paper will be devoted to back injuries because this category represents the greatest number of injuries occurring in coal mining. A man's best friends are his wife, his back, and his dog. The back, however, has a reputation of not being as faithful as his other two friends.1 "Industrial back injury is one of the major occupational health problems plaguing industry to- day. According to national surveys, back injury accounts for more lost time than any other occupational injury and costs companies thousands of dollars in compensation, medical fees and over- time pay."2 A study conducted by USA Today found that back ailments afflict an estimated 75 million Americans, have totally disabled about 2.5 million adults, lead to as many as 200,000 required surgeries each year, are a leading cause of absenteeism and disability, are the second leading cause of hospitalization, are responsible for 18 million doctor visits a year and cost about 93 million work-days annually. The cost to industry is estimated at $14 billion a year.3 During the past 30 years, a great deal of accident prevention education has been directed toward the reduction of back injuries. However, this effort has not produced any great change in the incidence of the injury. Back injuries should be of the utmost concern to everyone here today. I don't need to tell you what the incidence rate is for back injuries, nor will I use any statistics to inform you of the incidence rate for the coal mine industry or any specific mine. It is only important to know that the number of back injuries is excessive. Back in- juries resulting from lifting have been and continue to be one of the most constant and undiminishing problems in the occupational environment. The fact is, we use our backs to per- form work that the back was not designed to do. Historically, manual materials handling related accidents have consistently accounted for the largest percentage of all industrial accidents. In fact, over 25 percent of all industrial accidents are related to handling of materials.4 In underground coal mining operations, material handling accidents account for even larger percentage of lost time injuries. In 1983, for example, they accounted for 34 percent of all lost time injuries and 32.6 percent of all non-lost time injuries. 5 I want to use one example of a task that will illustrate what I have just said: the building of a concrete block stopping. Each solid concrete block will weigh from 60 to 70 pounds. To build a stop- ping 6 feet high and 20 feet wide will take approximately 80 blocks. On the average, these 80 blocks will be handled at least four times from loading into the conveyance for transportation to being placed while constructing the stopping. This generally requires repetitive lifting from ground level. The next three slides demonstrate the lifts

Jan 1, 1986

By F. Gonzalez, A. Zambrano, J. Schwoebel, S. Kravits

Significant lost time delays were experienced by Carbonifera de Nueva Rosita, S.A. de C.V. ("CNR") during mining development of the Pasta de Conchos Mine ("the Mine") near Nueva Rosita, Coahuila, Mexico. Furthermore, methane gas concentration in the return air course had exceeded 1.0 percent. Resource Enterprises, Inc. ("REI") was contracted by CNR to recommend an approach to reduce methane emissions at the Mine. In order to recommend a degasification approach, REI and CNR obtained geologic and reservoir characteristics of the Double coal seam, Olmos Formation. A vertical core hole was drilled to obtain core samples to determine gas content (average 8.4 cm3/gm) and to conduct a slug test to estimate permeability (34 md). This information was used to simulate gas productivity and drainage effectiveness. The simulation indicated that underground horizontal boreholes would remove significant quantities of gas in advance of mining in a reasonable period of time. Based on the results of the simulation study, an underground degasification drilling program was initiated at the Mine. In a six month period, five long in-mine degasification boreholes were drilled in advance of CNR's three to five years mining projections. Peak gas production from the five boreholes (approximately 2,750 cumulative meters) had exceeded 45,000 m3/D. Results to date have indicated a general reduction in methane concentration in the return air course below 0.8 percent.

Jan 1, 1993

By Plato Malozemoff

While this conference is dedicated to the examination of "Challenges in Mineral Processing," the broader aspect of the pursuit of this subject is Research and Development in the Mining Industry. When I was asked to speak at this symposium, I hesitated to accept. While my early schooling, training and professional occupation were in the field of this symposium, it was so long ago that I no longer feel competent to contribute anything of interest to you except perhaps for a limited historical perspective, which most of you probably already know. However, it might be worthwhile to explore the more general aspect of research and development from the viewpoint of management, as this is the stance from which I dealt with the subject for the last 30 years or so. While most managements generally have a positive view of research and development, few of the leaders in the mineral industry have actually had the personal experience of doing research for a long enough time to have obtained a full understanding and the feel for its place in the long-term technological innovation that our industry must foster. I graduated from the University of California in Berkeley with a Bachelor of Science degree and a major in metallurgy. It was during the great depression of the thirties, and it was difficult to obtain a practical job in the industry. I got a scholarship at the Montana School of Mines and received a Master of Science degree in ore dressing under Professor A. M. Gaudin, followed by another year with him pursuing research. Anyone who studied under him, or knew him well, would assert that this was a unique experience. Gaudin had a brilliant mind and a profound respect for science and the scientific method. He wished to know the scientific basis for every new technological appli-

Jan 1, 1989

By A. W. Khair, S. S. Peng

Background The mine is located in Ebensburg, Cambria County, PA. Cambria County is located within the Allegheny Mountain section of the Appalachian Plateau Province. The geologic structures in the mine area included folds, faults, joints and cleats in the coal. These geologic structures seem to have genetic relationships with the Allegheny Front (lannacchione and Puglio, 1979). The mine's geologic structures have been influenced mainly by Ebensburg Anticline and Wilmore Syncline (Watson, 1979). Current longwall panels lay along the western limb of the Wilmore Syncline oriented south 30° west. Surface topographic relief in the area is less than 152 m (500 ft) and overburden thickness varies from 183 to 244 m (600 ft to 800 ft). The coal seam in the mine is part of the Lower Kittanning Formation. The thickness of the B-seam is the subject of discussion. It varies from 1.2 to 1.5 m (48 to 60 in.) and consists of two parts. The lower part is 1.1 to 1.2 m (44 to 48 in.) of soft coal and the remainder is bony coal. The coal seam dips slightly from 0° to 6° to the east-south direction. Panel entries are driven 61 m (200 ft) wide, consisting of three 5.5 m (18 ft) wide entries and two pillars 24.4 x 30.5 m (80 x 100 ft) centers. The mine has a history of cutter roof problems in the entries (Fig. 1) that has delayed the advance rate of entry development considerably and the cost of maintaining those entries is very high due to the requirement of very heavy artificial supports (Fig. 2). Due to excessive convergence in the headgate, installation of additional support and often resetting of steel beam, to provide enough clearance, in these entries imposed additional delay during the retreat of the longwall face, as the shearer cuts coal adjacent to the headgate and shield support at the headgate needs to advance under the steel beams (Fig. 3). Methodology Extensive underground observation indicated that roof cutter [ ]

Jan 1, 1992

By J. P. Rider, T. W. Beck, J. A. Organiscak

"The National Institute for Occupational Safety and Health (NIOSH), Office of Mine Safety and Health Research (OMSHR) has recently developed a series of models utilizing Computational Fluid Dynamics (CFD) to study gas distribution around a continuous mining machine with various fan-powered flooded bed scrubber discharge configurations. CFD models utilizing Species Transport Model without reactions in FLUENT were constructed to evaluate the redirection of scrubber discharge toward the mining face rather than behind the return curtain. The following scenarios are considered in this study: 100% of the discharge redirected back towards the face on the off-curtain side of the continuous miner; 100% of the discharge redirected back towards the face, but divided equally to both sides of the machine; and 15% of the discharge redirected toward the face on the off-curtain side of the machine, with 85% directed into the return. These models were compared to a model with a conventional scrubber discharge where air is directed away from the face into the return. The CFD models were calibrated and validated based on experimental data and accurately predicted sulfur hexafluoride (SF6) gas levels at four gas monitoring locations. One additional prediction model was simulated to consider a different scrubber discharge angle for the 100% redirected, equally divided case. These models identified relatively high gassy areas around the continuous miner which may not warrant their use in coal mines with medium to high methane liberation rates. This paper describes the methodology used to develop the CFD models, and the validation of the models based on experimental data.INTRODUCTION Methane gas and respirable dust are two hazards frequently encountered at continuous miner (CM) operations. An accumulation of both methane gas and coal dust may lead to massive explosions underground [1], and overexposure to respirable coal dust can result in pneumoconiosis (commonly referred to as “Black Lung Disease”) in coal workers [2]. Current U.S. federal coal mine regulations limit concentrations of methane gas to below 1% at the face area and require exposures to respirable coal dust to be at or less than 2.0 mg/m3 for an 8 h shift average. Begin on August 1, 2016; the overall respirable dust standard in coal mines is reduced from 2.0 to 1.5 mg/m3 for full shift sampling. If the quartz content of the dust exceeds 5% by weight, the dust standard becomes more stringent, reducing the allowable concentration to the value of 10 divided by the % quartz."

Jan 1, 2015

By Steven E. Paulson

In situ mining is emerging as a potential alternative to conventional surf ace and underground mining techniques. A major factor in determining recoveries by in situ mining is the proportion of ore minerals that can be contacted and solubilized by the leach solutions. To provide basic information on the processes occurring during in situ leaching, particularly at the microscopic scale, the Bureau of Mines has developed a geologic characterization research program. This includes laboratory experiments using leaching apparatus that can accommodate whole core samples. Whole core experiments result in higher leach solution-ore mineral contact ratios than packed column experiments, and also allow for the assessment of permeability changes taking place as the result of mineral dissolution, precipitation, and clay swelling within the flow channels in the rock. A nonreactive, reusable reaction cell has been designed and tested. The leaching apparatus can be used for constant-pressure or constant-flow experiments and allows for the control of flow rate, pressure, and temperature during the experiments, thus permitting studies on a wide variety of ore samples. Details of the experimental apparatus and design are presented, as well as preliminary results from the first series of experiments on an oxide copper ore from the Casa Grande, AZ, area.

Jan 1, 1987

By Clement K. Chase, George M. Potter

Copper dump and heap leaching operations are conducted worldwide for production of substantial amounts of copper Such dumps and heaps contain appreciable amounts of other potentially valuable elements such as gold, Iron, magnesium, manganese, molybdenum, silver, titanium, and uranium. Except for uranium, recovery of these elements has not been attempted to any significant extent However, such recovery merits attention based upon availability of existing chemical techniques. This paper presents some thoughts on possible techniques together with opportunities for commercial applications.

Jan 1, 1983

By M. C. Roberts

Currently, mineral producers are suffering through a major downturn in prices for their products, even though it has only been a few years since they were enjoying high prices. From an historical perspective, the current situation is another of the cyclical down-turns that often reoccur every 5 to 7 years or so. This paper uses time trend decomposition techniques to identify the cycles and statistical methods to find the duration of these cycles for a variety of mineral prices. Given some idea of how long and severe these cycles typically are, the mining industry can better plan to weather the downturns and take advantage of the upturns. For example, timing investments in new projects to take advantage of the cyclical upturns can dramatically improve project profitability.

Jan 1, 2000

By D. W. Agers

This paper is an extension of previous work evaluating a new extractant, LIX®-64, for recovery of copper from dilute acidic solutions. Large scale pilot plant operations have confirmed the technical and economic feasibility of the process and, with minor exceptions, scale up parameters obtained by previous laboratory work. Operating problems encountered in the pilot plants are discussed. Design parameters for-scale-up to commercial plants are presented and discussed along with a revised capital cost estimate. The future pilot program is discussed, including minor design changes and the effect of entrained organic on dump leaching efficiency.

Jan 1, 1967