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By K. A. Natarajan, M. K. Yelloji Rao

Significance of grinding media wear and its effect on chalcopyrite flotation are discussed. Laboratory marked ball wear tests were conducted grinding chalcopyrite ore and quartzite dry, wet, and with collector added during grinding. The effects of oxygen and nitrogen on ball wear were evaluated by the addition of chalcopyrite mineral while grinding quartzite. The effect of dry and wet grinding on chalcopyrite flotation was also studied. Results show abrasive wear is greater in quartzite grinding than in grinding chalcopyrite. Oxygen increases the corrosive wear of high carbon low alloy steel balls in the presence of chalcopyrite ore. Chalcopyrite flotation was retarded due to wet grinding in the presence of oxygen. Though collector reagent increased the media wear, it improved the flotation of chalcopyrite. Probable electrochemical reactions encountered in a grinding mill are outlined.

Jan 1, 1991

By Dean J. Acuff

An overview of new size reduction technology involving the use of two-mass natural frequency vibration applied to a totally enclosed elongated drum. Material moves with a drum-like rotary motion with exposure to constant, aggressive, high frequency agitation for faster reduction and enhanced product quality. A proven, patented design with few moving parts, a vibrating mill drum provides the desirable environmental benefits of a totally enclosed rotary drum but without the same interfacing difficulties. Natural frequency design has reduced energy demand which is met by low horsepower, self-contained, motorized drives to dramatically reduce the cost per ton of finished product.

Jan 1, 1993

By John W. Wilson

INTRODUCTION In the past, the cost and time required for the construction of shafts has played an important part in the planning of underground mines. For reasons that are discussed later, the economics and technology of shaft construction in the future can be expected to play an even greater role in the planning of new mines and the operation of existing mines. Indeed, the very feasibility of a proposed mining venture may depend on the cost and timing of the shaft requirements. The most commonly used shaft sinking methods used today for excavating vertical shafts are discussed and the need for new technology and methods emphasized. In one study by the U. S. Bureau of Mines, it was reported that the coal industry in the United States alone could require 170 to 190 new shafts per year on the basis of doubling current production by the mid 1980's or 70 to 90 shafts on a more moderate coal production expansion program. This study concluded that the attainment of the required number of shafts would be unlikely with the present shaft sinking resources and costs. In order to meet the requirements for shafts in the United States coal and metal mining industries, more efficient and speedier shaft construction methods will be necessary. Current shaft sinking methods are, in the main, labor intensive, and it is noteworthy that it is becoming increasingly difficult to attract the work force required to sink shafts conventionally. Because of this situation, some attempts at mechanization have been made to compensate for this ever-increasing scarcity of trained

Jan 1, 1976

The implementation of NAFTA in January of 1994 was expected to have small but beneficial effects for the Mexican economy, mostly through increased investment flows. Mexico's mining industry was especially likely to benefit, as mineral investment funds would be diverted to the now safer Mexico and away from similarly endowed but more risky Latin American mineral economies. The results of the past two years have shown that it is governments and macroeconomic factors that influence investment flows, rather than the fine-tuning of trade flows through so called "free-trade" agreements.

Jan 1, 1996

By W. A. Haley

As far back as 1939 state laws have required reclamation of mined lands. Reclamation has been the topic of many discussions and presentations, especially since the late 1960's. In the past ten years many states have added legislation concerning the reclamation of coal-mined lands. In the near future, it seems certain that some federal regulations will be passed that will set minimum guidelines for the states to regulate. Besides the requirement of returning the land to the approximate original contour, future regulations will more than likely demand replacing topsoil from one to five feet thick. As regulations become more stringent, costs will rise accordingly. Since no one has developed a machine that can do all reclamation work by itself, it is necessary to review in detail the tools available and to select the most economical means.

Jan 1, 1976

By R. L. Peyton

Risk analysis is used extensively in many engineering applications. Although its use in the field of dam safety has been limited in practice, it has received considerable attention in recent years in the dam safety literature. Thus far, it has been shown that risk analysis in the evaluation of existing dams has the potential for providing a more rational basis for decision- making because of its focus on the direct issues--likelihood of failure, likelihood of loss of life, and risk cost of damages. It provides for a logical balance between the risk a dam imposes and the degree to which rehabilitation is required, compared to traditional evaluations based on somewhat arbitrarily chosen design events applied to large classes of dams. Dam owners could benefit by optimizing the cost of remedial measures. Downstream landowners could benefit by minimizing the likelihood of flood damages. However, it is also clear that significant technical and policy issues remain to be resolved before risk analysis in dam safety is accepted and routinely implemented in engineering practice. An obvious and important potential application of risk analysis is its use by the state regulatory agency as an in-house evaluation tool, or even as part of regulatory policy, in the implementation of its state dam safety program. Adoption of such a policy would have an important impact on the mining industry. .Although no state dam safety programs are known by the writers to have officially incorporated risk analysis into their regulations, there appears to be considerable interest in the concept. In recent surveys 47 states agreed that the development and promotion of a risk assessment methodology for state dam safety programs should be encouraged (Tschantz, 1983; Tschantz, 1984). The issue has also received important attention within the Association of State Dam Safety Officials (1986). One state-Illinois-proposed regulations during 1986 to allow risk analysis to justify lower spillway requirements for existing dams (Illinois Department of Transportation, 1986). At the Federal level, the National Research Council has found risk analysis especially appropriate for assessing dam safety at high-hazard dams (National Research Council, 19851, the Bureau of Reclamation has published guidelines for incorporating risk analysis into their dam safety grogram (U.S. Department of the Interior, 1986), and the Federal Emergency Management Agency has recently sponsored workshops and supported research related to risk analysis in dam safety (Federal Emergency Management Agency, 1985a ; Federal Emergency Management Agency, 1985b; - - McCann, et. al., 1985a, 1985b).

Jan 1, 1986

By A. Probst, N. Moores, J. A. Finch

In 1994, McGill University and INCO Ltd. (Sudbury operation) initiated the transfer of technology originally developed to detect levels in equipment ranging from flotation columns to thickeners. A conductivity probe was installed in a concentrate thickener to monitor the mud line and the solids load. The probe consisted of a vertical tube with 32 equally spaced electrode rings connected in pairs to give 31 conductivity cells. Conductivity was measured as a function of depth to produce a conductivity profile. From the conductivity profile, the mud line and the percent solids can be inferred. The probe was installed in October 1994, and it has been successfully detecting profiles since then. This paper includes a description of the incidents that occurred and the experiences gained during this technology-transfer process. Discussed is probe installation and startup; software modifications to accommodate both operating conditions and the needs of the operators; and calibration procedures to adjust to changes in performance as a consequence of long-term use. Also included are preliminary observations of the still-in-progress last stage, i.e., signal interpretation and use to facilitate operation, particularly by providing early reaction to upstream disturbances.

Jan 1, 1999

By Orlando Oliveros

The Los Bronces Mine and Concentrator, one of the three operating units of Compania Minera Disputada de Las Condes S.A. (an Exxon Minerals Co. affiliate), is located in the high Andes of East-Central Chile approximately 70 kilometers northeast of Santiago at an elevation of 3,650 meters above sea level. (Figure 1). Santiago, the capital city of Chile, is located at an elevation of about 500 meters above sea level and enjoys a very mild climate, similar to some areas of California. At the mine site, however, extremely heavy winter conditions prevail occasionally, with very heavy snow and the resulting snow avalanches endangering installations and people. At the same time, ideal skiing conditions are found at the nearby ski resort of Portillo and Farellones. Mount Aconcagua, the highest mountain in the western hemisphere is only about 55 kilometers further to the northeast of the Los Bronces mine.

Jan 1, 1983

By S. Hodgson

Introduction The Red Dog zinc/lead deposit in northwest Alaska is the second largest zinc deposit ever discovered. Being developed by Cominco Alaska, with startup scheduled for early 1990, it will ultimately be the largest zinc mine in the Western World. Table 1 shows the reserves of the deposit. Bob Baker, a local bush pilot, discovered Red Dog in 1968. The US Geological Survey assessed the find. But the Red Dog site had been withdrawn from staking by provisions in the Alaska Native Claims Settlement Act of 1971 (ANCSA). Under the terms of ANCSA, the deposit was selected by the NANA Regional Corporation, one of 13 native corporations established by the Act. Then, in 1980, the US Congress confirmed this selection, in the Alaska National Interest Lands Conservation Act. In 1982, Cominco and NANA reached an agreement that has led to the development of the mine. Under the agreement, Cominco leases the property from NANA, develops and operates the mine, and markets the concentrate produced. In return, NANA receives royalties and, after capital recovery, participates in the net proceeds from the operation. The Alaska State Government is also playing a role in the development of the mine. Under the auspices of the Alaska Industrial Development Authority (AIDA), the state will construct, own, and operate the DeLong Mountains Regional Transportation System. This consists of a 84-km (52¬mile) road from the minesite to the Chukchi Sea. Located here are the port facilities necessary to store and ship the annual concentrate production and receive the mine fuel and supplies. For using this transportation system, Cominco will pay an annual toll fee. Over the anticipated 50 year life of the operation, the fee will provide a 6.5% return to the State of Alaska. In late 1986, Cominco's Board of Directors approved the Red Dog project. And, during the summer of 1987, road construction began. In February 1988, initial stripping began at the ore body and construction started at the millsite. Project setting The project site is approximately 1000 km (600 miles) northwest of Anchorage, 84 km (52 miles) east of tidewater on the Chukchi Sea, and 192 km (120 miles) north of the Arctic Circle (Fig. 1). The countryside consists of low, rolling hills that lead into mountains north and east of the deposit. The vegetation is typical tundra mat. And the site is in an area of permafrost. However, the permafrost is relatively warm and some areas have been found to be thawed. Examples would be creek bottoms and the site of the main waste dump.

Jan 12, 1988

By William E. Bonini

Gravitational field anomalies have been observed over many igneous intrusives of medium (4000 km2) to small (100 km2) size in outcrop area. These studies give good results because the residual anomalies can be separated from larger scale crustal anomalies and density contrasts usually are present. Although unique solutions are not possible, the analysis of the gravity anomalies can put limits upon the geologic interpretation of such bodies. Three examples in Montana, U. S. A. are discussed: (1) the Boulder Batholith, a late Cretaceous quartz monzonite series of intrusives of 4000 km2 outcrop area; (2) the Little Rocky Mountains, an up-domed area, in which an Eocene porphyry (130 km2) has intruded the Precambrian crystallines and lower Cambrian sediments; and (3) the Crazy Mountains, an Eocene diorite (100 km2), which has intruded the Paleozoic and Mesozoic sediments. In both the Boulder Batholith and the Little Rocky Mountains, intrusive rocks are less dense than the surrounding rocks and negative anomalies are found (40 and 28 mgal, resp.). In the Crazy Mountains, the intrusive is more dense than the surrounding sediments and a sharp positive residual anomaly of 42 mgal is observed. The analyses of the gravity anomalies predict that: (1) the thickness of the Boulder Batholith is on the order of 10 to 15 kms and is concave upward; (2) the Little Rocky Mountain syenite is not a simple laccolith, but is T-shaped and extends in depth to about 16 kms; (3) the Crazy Mountain diorite is not a simple small scale series of stocks, but a large connected body extending in depth 5 kms to the basement (although nothing can be said of it within the basement because there is little density contrast). The analyses of the anomalies place important limits on both the areal and depth extent of the intrusive bodies. Of all possible geophysical techniques, gravity studies offer the most promise in the determination of the shape in depth of intrusive bodies.

Jan 1, 1969

By Chris J. Conway, Bruce W. Atkinson, Graeme J. Jameson

The flotation of coal in the fie and coarse particle size ranges presents particular problems. Fine or ultra-fine coal less than 100 microns presents a challenge to conventional flotation machines because the rate of capture of the coal particles can be very low, so longer residence times are needed. Also, conventional mechanical cells are not normally designed with froth properties in mind. Froth drainage may be inadequate, leading to excessive entrainment of ash. The upper limit of flotation of coal is normally put at about 500 um (30 mesh). It appears that, in mechanical cells, coarser particles tend to be torn away from bubbles in the turbulent environment created by the impeller. In this paper, results are presented from plant trials of a high-intensity flotation column of novel design, namely the Jameson cell. Extensive trials have been conducted on coal slurries with a top size of around 1 mm. Size-by size analysis shows that it is possible to achieve high yields of low ash product over the whole particle size range.

Jan 1, 1995

The extraction and recovery of gold from copper electrorefining slimes by leaching and solvent extraction using dibutyl carbitol (DBC) has been practiced for several decades. Yet, the deportment of some common elements in this process has not been reported. The focus of this paper is to report the behavior of copper, bismuth, silver and selenium during the processing of industrial solutions by batch and continuous extraction on the laboratory scale. It was found that DBC, while an excellent extractor of gold from a highly oxidative chloride leach solution, also loads significant quantities of Cu, Bi, and Se. Silver was not present in significant quantities in the leach solution nor did it load appreciably. The deportment of gold and impurities are reported for batch and continuous operations of a two-stage extraction process using distribution ratios and separation factors.

Jan 1, 2010

By F. Letowski

A column reactor was applied for leaching with simultaneous flotation a complex sulfide ore in ferric sulfate-solution under oxygen pressure. Elemental sulfur and the flotable, nonreacted sulfides were collected in the froth and separated from the insoluble, nonflotable gangue minerals and solid particles formed during pressure leaching. The two-stage laboratory unit, built from Corning-glass elements is described. Results of the continuous leaching/flotation experiments conducted under 20-40 psig of oxygen pressure are presented, as are supplementary batch leaching experiments with iron precipitation under 150 psig oxygen pressure. High zinc extraction to solution and near total accumulation of lead sulfate in the nonflotable fraction are easily attainable. Relatively poor flotation of pyrite is probably caused by the partial oxidation of its sulfidic sulfur to sulfate.

Jan 1, 1988

By Ronald H. Mullennex

The growing need for development of thinner, more erratic, or less easily- mined coals in the Appalachian region requires more detailed analysis of conditions and factors controlling or influencing deposition of these seams. The value of depositional modelling in evaluation of such coals has been demonstrated in many recent studies and publications. Such modelling may be applied to allow prediction of factors varying from regional coal occurrence trends to very local areas of seam discontinuities, but requires thorough utilization of all available types of data. Mapping of general depositional energies, as derived from basic geophysical and driller's logs, can be applied to specific prediction of coal occurrence, and projection of particular facies as representative of unique depositional features or conditions often proves more applicable to coal character delineation than does mapping of the coal itself. Depositional modelling and trend projection may also serve as a guideline in reserve classification and confidence-levels in reserve estimations.

Jan 1, 1981

By Stephen P. Winkelmann

The expansion of gold production in Nevada's Carlin Trend over the last few years has been staggering. To increase gold production while minimizing capital requirements and providing for the safe and efficient mining and processing of ores has required a tremendous effort by the mine engineering group at Newmont Gold. Organizational changes were implemented by the company to effectively deal with a full range of engineering problems. Specially developed computer software and its applications will be explained in this article as well as improvements in the techniques used in converting geologic resources into reserves. Scheduling procedures for the mining of multiple pits to feed multiple processing facilities will likewise be presented. Ore control procedures and current mine engineering practices are discussed. Growth at Newmont Gold Expansion of production levels at Newmont Gold Co. was brought about primarily by the economic incentive to exploit increased reserves. From 1987 to 1989, mined production increased by 260%, gold production by 238%, and manpower by 166% (Table 1). These increases came quickly and demanded

Jan 1, 1990

By V. G. Medina

The 15 000 t/d La Coipa mine initiated operation in July of 1991. The complex consists of a conventional, open-pit mining operation and a mill employing cyanide leaching with Merrill-Crowe gold and silver recovery. The process plant includes a primary crushing circuit, a 15,000 t (live) covered stockpile, a semi-autogenous mill/ball mill/crusher or SABC grinding circuit, a leach circuit, a belt filtration/washing circuit, a zinc precipitation circuit and a "dry" tailing disposal system. The process plant is described in detail with major design considerations used in the selection of the processes and equipment. The unique methodology employed in the disposal of the filtered tailings is also described.

Jan 1, 1992

By B. Mishra, Q. Shi, Y. Zhao, G. Zhao

Shale is anisotropic due to the presence of bedding planes. The anisotropic strength of shale has been extensively studied. However, little attention has been paid to the size effect on shale strength considering the anisotropy. This research uses the discrete element method to study the size effect on the strength of shale under the uniaxial stress state. It is assumed that the anisotropy is caused by bedding planes, while the size effect is caused by randomly distributed flaws. The numerical model of shale comprises three components: shale matrix modeled by bonded particles (2) bedding planes modeled by smooth joints (3) flaws modeled by discrete fractures. The developed model is scaled to different sizes and tested in the uniaxial compression and the direct tension tests. The test result show that the uniaxial compressive strength decreases as the specimen size increases when the loading direction is perpendicular or parallel to bedding planes. The uniaxial compressive strength is determined by the flaws while the bedding planes only play a limited role. However, the size effect on the direct tensile strength depends on the direction of bedding planes. When the loading is perpendicular to bedding planes, the size effect is not prominent. The direct tensile strength is determined by the bedding planes while the flaws have little effect. When the loading direction is parallel to bedding planes, the direct tensile strength decreases when the specimen size increases. The direct tensile strength is determined by the flaws while the bedding planes have little effect.

Mar 2, 2022

By G. J. Joy, J. P. Rider

"Technical advances in longwall mining over the last several years have resulted in much larger and faster shearers that have the capability of mining at speeds over 100 ft./min. This has resulted in a substantial increase in the amount of dust that is generated at the shearer and during shield advances. Meanwhile, increased underground coal production has put a greater demand on longwall dust control systems as some operators have had difficulty maintaining consistent compliance with federal dust standards. To address this need, the National Institute for Occupational Safety and Health [NIOSH] is investigating the effectiveness of a water spray manifold mounted on the tailgate end of the shearer body. The sprays are oriented parallel to the tailgate ranging arm, and these sprays create a water curtain confining the dust plume near the face, preventing the dust from drifting into the walkway. This redirection of dust provides a clean air envelope for the tailgate shearer operator and jacksetters working near the tailgate drum. Three different tailgate spray manifold designs were tested and evaluated at the Office of Mine Safety and Health Research [OMSHR] Pittsburgh Longwall Test Facility. Manifolds were equipped with hollow cone or flat fan water spray nozzles and evaluated at three face air velocities (500, 700, and 900 fpm) and at water pressures of 100, 150, and 200 psi. Reductions in dust concentrations were observed at six face sampling locations for all the tailgate manifold systems at each of the tested spray pressures and face velocities. Based on results from the laboratory tests showing reductions in dust concentrations at sampling locations downwind of the shearer a spray manifold was fabricated and evaluated at an underground operation. INTRODUCTION In 2012, underground coal mining in the United States produced a total of 342 million short tons, with longwall mining accounting for over 53% of this production [EIA 2013]. The longwall mining industry continues to see remarkable and significant improvements in longwall mining equipment and mining practices. Average shift production during compliance dust sampling has increased from 3,500 tons per shift in 1994 to approximately 6,000 tons per shift in 2012. A dramatic decrease in working longwall faces from 80 to 49 has occurred over the same period [Fiscor 2013]. Factors specific to longwall mines that supported productivity improvement include: higher capacity shearers, improved shield hydraulics and control, higher horsepower for equipment, wider face conveyors, and larger faces. Today, the average face width has increased to 1,188 ft., with one longwall operation reporting a face width of 1,650 ft. compared to an average of 750 ft. in 1994 [Fiscor 2009, 2014]. Panel lengths in 2013 averaged 11,307 ft. compared to 7,000 ft. in 1994. Overall production from U.S. longwalls has increased by nearly four percent from 2007 to 2012 with over 182 million tons mined annually [EIA 2013]. Given the volume and rate of coal produced on longwall faces, the potential to generate large quantities of respirable coal mine dust also exists."

Jan 1, 2015

By Terry McNulty

There are many potential pitfalls in the commercialization of innovative technology. The failures often are remembered longer than the successes, thereby serving as deterrents to subsequent attempts. The mineral industry's future depends on effective innovation. So it is essential that the causes of failure are understood. Innovation can be examined equally well in the context of geophysics, geology or mining. However the author's experience has been in mineral processing and chemical engineering. So the following discussion is limited to processes and/or plants for producing mineral concentrates, metals or inorganic chemicals. More of what follows has to do with underachievement or failure than success. But this article demonstrates that there is a strong element of predictability in the former. Furthermore, it is a credit to the minerals industry and to the engineering profession that a very high percentage of projects succeed in achieving design capacity and forecast operating costs. Innovation means the introduction of something new. In this article, the words "innovative technology" are used broadly. They include new processes and novel combinations of established unit operations, as well as novel types of processing equipment or largest-ever equipment models. The discussion of project outcomes is based on personal experience or on published information. Citations are given for technical publications that provide either project information or insights into the methodology used to analyze project performance. However, specific projects have not been identified due to the rather negative connotations of some of the conclusions drawn about the less favorable outcomes.

Jan 1, 1998

By W. J. Schlitt, J. H. Templeton

The chemical reactions that occur within a copper-leach recovery system are discussed, and the impact on the overall acid balance is evaluated. Both oxide and sulfide mineralogy are addressed, and their effects on acid consumption, generation and solution buffering are presented. Two case studies that apply the discussed chemistry show the practicality of using a computer spreadsheet acid-balance model for the early planning and design of copper-leach systems.

Jan 1, 1998