Search Documents

By P. James

"INTRODUCTION Dissolved salts build up in leach solutions over time as leach solutions mature. Iron can be particularly problematic for hydrometallurgical copper production as it can compete with copper for separation during solvent extraction (SX), leading to iron bleed through and reduced electrowinning (EW) efficiency. In its ferric form (Fe+3) it precipitates as a hydroxide at fairly low pH and can promote clogging and disrupted flow within leach pads as a result of localized pH deviations – such as might result from weather events. The solids formed can cause relatively irreversible degradation to pad productivity. The precipitation pH point for solids formation falls as the ferric (Fe+3) concentration increases, making the issue more prevalent as leach circuits for ore bodies containing appreciable iron get older. It can also be more of a concern when leaching lower grade ore like tailings where lower copper content may increase iron/copper ratios which may increase iron accumulation rates. The precipitation pH point for solids formation falls as the ferric (Fe+3) concentration increases, making the issue more prevalent as leach circuits for ore bodies containing appreciable iron get older. It can also be more of a concern when leaching lower grade ore like tailings where lower copper content may increase iron/copper ratios which may increase iron accumulation rates. Control of ferric (Fe+3) levels could be used to lower ferric (Fe+3) levels and keep the ferric hydroxide [Fe(OH)3] precipitation pH sufficiently high to avoid the associated solids formation and potential leach pad occlusion. Control of ferric (Fe+3) and ferrous (Fe+2) tenors and ratios may also provide benefit for improving sulfide ore leaching or bioleaching performance and effectiveness. Traditionally options for such control were rather limited with bleeding contaminants off or chemical dosing treatments being prominent methods. Now Blue Planet Strategies introduces a new option. Blue Planet Strategies (BPS) focuses on improved resource utilization targeting electrolytic treatment and waste conversion into resources and has now demonstrated that its proprietary DeMet™ (Dynamic Electrolytic Metal Effluent Treatment) platform is highly effective at efficient low-cost conversion and control of iron content in leach streams in addition to targeted dilute metal recovery.[1-6] This powerful new capability provides a new treatment opportunity to control leach solution ferric (Fe+3) and ferrous (Fe+2) tenors to enhance leach operation production."

Jan 1, 2015

By C. W. Schultz

The Alabama tar sands of the Hartselle Sandstone formation present a more difficult problem in primary extraction than do the Athabasca tar sands. In contrast to the Athabasca tar sands, the Alabama tar sands are "oil wetted" and the contained tar, or bitumen, is of much higher viscosity. A physical beneficiation scheme was developed in which clean sand from an external source was used as a scrubbing medium. High intensity scrubbing liberated the tars which are readily recovered by froth flotation. Locked cycle tests have shown that, after the use of an initial ration of clean sand, the system produced enough new clean sand to be self sustaining.

Jan 1, 1992

By Warren D. MacEvoy

INTRODUCTION Good ventilation bulkheads (stoppings) can be obtained only by conscientiously adhering to four basic principles: carefully selecting the site for the bulkhead, adequately preparing the site, properly constructing and sealing the bulkhead, and checking the results with a smoke tube before leaving the area. If all these guidelines are followed during each ventilation project, a poor job will result only from the use of improper materials and cannot be blamed on carelessness or oversight. SITE SELECTION A perfectly constructed bulkhead in the wrong location can be completely worthless. Conceivably, a bulk-head in the wrong location could cause dangerous ventilation conditions that are difficult to identify and isolate. If the suggestions herein are followed, a considerable amount of work, time, and material may be saved. Perhaps the single most important step is always to select the exact site for a bulkhead before starting construction. Although the latitude in selecting a site may be limited by instructions or operating conditions, it is common to find poor bulkheads built within a few meters (feet) of a site that would have been far superior but was overlooked during the planning process. The ideal site for a bulkhead should have as many of the following features and conditions as possible: 1) To provide a solid bulkhead, the selected site should be in firm and unbroken ground. 2) To minimize the amount of work and material required and to minimize the danger of later damage to the bulkhead, the site should have as small a cross section as possible. 3) The bulkhead site should not be encumbered by interferences such as pipes, wires, ditches, wire roof supports, trash, muck piles, etc. 4) The walls and timbers of the site should be free from oil, grease, or tar that would inhibit adhesion of the sealant used on the bulkhead. 5) Unless special precautions are taken, the site should not have water seepage, standing water on the floor, or water-carrying ditches. 6) To expedite construction of the bulkhead, the site should have reasonable access to transportation, supplies, communication facilities, and compressed-air lines. 7) The site should have a reasonably level floor, allowing direction of the bulkhead door swing to be reversed at a later time if so desired. In a steeply sloping location, it may be possible to open the door in one direction only. SITE PREPARATION Once a suitable site has been selected for the bulk¬head, it must be prepared properly. All site preparation work should be completed before starting any construction work on the stopping itself. Unfavorable site conditions can be identified during the course of thepreliminary site preparation, saving time, effort, and materials that otherwise might be wasted. The follow¬ing preparation steps help assure the construction of a good stopping: 1) If wire mesh has been used at the site, a strip 457 mm (18 in.) wide should be cut and removed from the walls and roof at the selected location. 2) The exposed strip of rock should be barred down thoroughly to provide a smooth surface. 3) All obstructing materials should be removed, including old timbers, pipes, rockbolts, wires, etc. If a conduit must cross the bulkhead area, it should be located or relocated away from the floor, walls, and roof to allow a 6.28-rad (360°) seal around the juncture between the conduit and the bulkhead structure. 4) All loose muck should be cleaned from the site and a trench about 152 mm (6 in.) deep should be dug from wall to wall in the floor. The trench must be wide enough to accommodate the entire bulkhead, including the posts. 5) The rock surfaces of the walls and roof should be cleaned with a wire brush to remove as much loose surface material as possible. Thorough cleaning promotes adhesion of the bulkhead sealant to the surfaces of the walls and roof, thus promoting an airtight seal. 6) It is quite difficult to seal landing mats that cross a bulkhead. If such a crossing cannot be avoided, the bulkhead should be placed between the end and the first hole in the steel so at least one side of the bulk-head can be sealed easily and completely. That may have to be done prior to actual construction if the end is located on the opposite face from the seal coating of the bulkhead. BULKHEAD CONSTRUCTION The three principal considerations in bulkhead con¬struction are the type of bulkhead, materials to be used, and construction method to be employed. For many projects, the bulkheads are specified by the requesting agency, with no latitude for independent choice of the type, materials, or construction method. In such cases, any deviations from the specifications, for any reason, must be approved in advance by the proper department or by the project senior ventilation engineer. Types and Materials When a choice of type, materials, or method is allowed, consideration should be given to factors such as cost, required useful life, proximity to blasting concus¬sions, availability of materials, direction of permissible air leakage, and degree of airtightness required. Other factors to be considered include the amount of time available, accessibility of transportation, potential for interference with operations or production, ambient water conditions, availability of connections to com¬pressed-air lines, etc. Despite the multitude of factors to be considered, most stoppings can be analyzed easily and the proper choices can be made without much difficulty. The four common classes of bulkheads utilized in

Jan 1, 1982

By D. L. Moellenberg

Under various state laws enacted mostly within the last 20 years, reclamation requirements and standards for hard-rock mining operations have been established virtually everywhere in the western United States. Unlike the uniform and detailed coal mine reclamation requirements under the federal Surface Mining Control and Reclamation Act ( "SMCRA" ) and state programs mode led after SMCRA, the various state law hard-rock mine reclamation requirements are based upon a variety of objectives, and therefore are subject to varying standards from state to state. While the diversity of reclamation requirements complicates the determination of what reclamation measures will be required at any particular mine, there are valid reasons for this diversity. There are dozens of different commodities mined in the United States, and mining methods are different for each commodity. Local natural conditions such as climate, precipitation, geology, hydrology, and biology vary widely across the county. Site-specific conditions also affect mining and reclamation methods. Also, factors such as economics, land use, and environmental protection issues receive different priorities in different states and communities within those states. State reclamation requirements in general provide the flexibility to consider site-specific circumstances, allowing operators to design and engineer the best reclamation measures for each mining site. To the mine developer or manager, reclamation requirements must be translated into design, operational, and closure measures for mine planning. Each of these measures must then be assigned additional costs to be factored into the economic decisions for a particular mining operation. On a broader level, reclamation costs must be factored into decisions such as where to invest in exploration and mine development. The purpose of this paper is to provide a summary of the state non-coal mine reclamation requirements in twelve western states. This summary comparison may be useful as a starting point in considering how local reclamation requirements will impact potential mining costs.

Jan 1, 1994

By Y. J. Wang

In the mathematical analysis of electrical networks, the electrical devices are often modeled using idealized network elements such as current sources, voltage sources, and resistors. An analogous approach is outlined here for the modeling of mine ventilation networks, which can be considered nonlinear resistive networks. The modeling technique proposed uses five basic (non-reducible) elements: the H element, the Q element, the D element, the R element, and the N element. These elements are characterized by their (a) pressure gain or loss, (b) air quantity, and (c) pressure-versus-quantity relationship, each of which may be known or unknown. In addition to the definition of the basic elements, the necessary conditions for which there exists a unique solution are discussed. This is performed using theoretical developments derived from electrical circuit theory and illustrated in example networks. The proposed procedures are useful in the solution and characterization of mine ventilation networks.

Jan 1, 1996

By James W. Mitchell

On December 2, 1942, a scientific team lead by Nobel Prize winner Enrico Fermi first initiated and controlled a self-sustaining nuclear chain reaction. This historic event occurring beneath the stands of the University of Chicago football stadium instantly created an entirely new and tremendously broad area of technology. Indeed, the event probably changed the course of world history and considering the curret energy shortage, it probably came none too soon. Following many technological breakthroughs in the ensuing years, this event led to the first full scale nuclear fueled electric generating plant. In December, 1957, the Shippingport Nuclear Power Plant became operational and the United States had entered the era of the nuclear fueled electric generating station. Today, only fifteen years later, there are some thirty-five operating nuclear power plants in the United States with another 56 under construction and 116 on order. Still, we are only scratching the surface of this tremendous energy source. In 1970, less than one-percent of the total electric generating capacity in the United States was nuclear fueled. By 1985, it is projected that 45% of our generating capacity will result from nuclear power plants. These projections are based upoa statistics of six months to a year ago and considering the current energy shortage and recent attempts by the United States Atomic Energy Commission (USAEC) to speed the licensing process and encourage standardized plants, the contribution of nuclear power to our total generating capacity may be even greater. In summary, it is obvious that nuclear power is now, and will continue, playing an important role in our future. Those factions of government, industry and the professional community charged with fully developing this tremendous energy source must deal with it rationally, logically and expediently. The various environmental considerations in nuclear plant siting play an important role in the overall plan.

Jan 1, 1974

By D. J. Sweet, B. Seymour, T. M. Emery, M. Armatys, J. P. Bourgeois, W. Johnson

The Spokane Mining Research Division (SMRD) of the National Institute for Occupational Safety and Health (NIOSH) has partnered with a narrow vein, hard rock underground mine to research the effects of the binder content on the elasticity and post-peak ductility of cemented hydraulic backfill (CHB). This is part of a larger study to enhance the long-term integrity of ground support in underground mines. As mining advances deeper and stresses increase, CHB mix designs will benefit if they can be modified to handle higher levels of strain which are induced by an increased stope closure, typically affected by a reduction in stope width and increased mining depth, or through dynamic loading resulting from a local seismic event. This portion of the research examined the impact of reductions in binder and their impact on Young’s modulus, peak strength, and post-peak ductility.

Mar 2, 2022

By R. Mensah-Biney

The loading characteristics of gold-tetrabromide species onto activated carbon have been evaluated using a completely mixed batch reactor system. The overall loading of gold onto carbon was rapid for the first hour but continued slowly without cessation as a result of reduction of gold. Conventional equilibrium considerations were therefore not applicable. Although loading continued slowly after several days, abnormally high loading capacity values of 10-12 meq/g carbon (650-800 kgAu/tonne) could be attained within 72 hours. The loading of gold-bromo species by activated carbon was by the mass transfer of [AuBr4l-onto the carbon surface where reduction to metallic gold took place. Elution of gold from the loaded carbon was feasible provided the carbon had not been loaded to too high capacity values. If loading is carried to high levels, complete elution becomes impractical and the gold may be recovered by ashing the carbon. For the high loading capacities observed, this option would appear to be cost effective. The effect of several variables on the loading capacity of the activated carbon is discussed.

Jan 1, 1992

By A. D. S. Gillies

Loss of visibility due to the occurrence of atmospheric fogging in underground mine airways can lead to a reduction in travel times and loss of production efficiency, an increase in the frequency of vehicular and foot traffic accidents and difficulty in checking rock surfaces for instability and loose material. Where hot and humid surface air meets colder underground air, conditions for fog formation nay be present. Further, suspended particulate matter from diesel exhausts or stoping operations together with slow movement of air along passageways nay contribute to formation. The study describes an investigation being undertaken with the cooperation of Kennecott's Ozark Lead Company to identify causes of the problem.

Jan 1, 1982

By R. Wild

[When a blast furnace has a certain defined burden and is operated under fixed conditions of blast temperature, etc., the fuel efficiency is determined by the extent to which the reducing gases can remove oxygen from the burden in the furnace stack. This is determined by two distinct factors: 1) The uniformity of gas-solid contact, and 2) The ease with which oxygen can be removed from individual pieces of burden. This latter is often called burden reducibility. When burdens were poorly prepared the first factor was by far the most important and a study of the reducibility of individual lumps was of rather academic interest recent years good burden preparation with emphasis on sized material has led to greatly improved gas distribution in the stack, and thus the second factor has become much more important and there has been a marked increase in interest in methods of measuring reducibility.]

Jan 1, 1964

By J. F. Oyler

One of the most important applications of material handling engineering technology occurs in iron ore pelletizing plants. Although the total installed value of material handling systems in such plants, as well as in many other modern process plants, is a relatively small percentage of the value of the plants (5 to 10% perhaps), their significance is considerable. Indeed this significance equals that of the more expensive process equipment in the plant, since the failure of any component of any system causes, shutdown of the entire plant. It is because of this increased consequence of failure that design criteria for process plants are more conservative than for conventional material handling applications. A second unique characteristic of material handling technology applied to process plants in general is the variety of materials being handled and the wide range of problems this variety presents. One extreme encountered is the stickiness of filter cake. Here the entire design effort is aimed at keeping the material flowing through transfer points and preventing it from building up on components. Another extreme is the conveying of fired pellets - hard spheres with a very flat angle of repose and abrasive characteristics severe enough to make conventional wear plate materials impractical.

Jan 1, 1976

By Hee-Young Chung, In-Mo Lee, Jeongjun Park, Hangseok Choi, Seok-Won Lee

"When using a Tunnel Boring Machine (TBM) during tunneling work, unexpected ground conditions can be encountered that are not predicted in the design stage. These reduce the stability of tunnels, and can result in considerable economic losses. This paper analyzes the potential risk events that may occur due to risky ground conditions. A resistivity survey is utilized to predict the risky ground conditions ahead of the tunnel face during construction. The potential risk events are evaluated considering both the occurrence probability and the impact. A TBM risk management system that can suggest proper solution methods for potential risk events is also developed. Multi-Criterion Decision Making (MCDM) is utilized to determine the optimal solution method to handle risk events. Lastly, an actual construction site, at which a risk event occurred during tunnel construction, is analyzed utilizing the Earth Pressure Balance (EPB) Shield TBM, to verify the efficacy of the proposed system.INTRODUCTION The Tunnel Boring Machine (TBM) method has been widely adopted in numerous tunneling projects because, as a mechanized tunneling method, it is also environmentally friendly, exhibiting minimal noise and vibration when compared with conventional tunneling method. In addition, it provides considerable economic benefits that allow for a high advance rate for long drives during construction. However, the TBM method has a limitation, as it is unable to deal with unexpected situations during construction, as the system is not capable of moving backwards. This leads to delays or even stoppages, and a corresponding increase in construction costs due to the need to arrange for alternative equipment and solutions. It is essential to retain systematic management in order to prevent or deal with unforeseen consequences such as the collapse of a tunnel face, ground surface upheaval or settlement, and construction delay due to water leakage during construction. Therefore, a systematic risk management system that is applicable during the construction stage of the TBM tunnel should be developed, taking into account the predicted risky ground conditions ahead of the tunnel face in advance."

Jan 1, 2016

By John Callahan

A stream sediment (minus 80-mesh and minus 60-mesh panned concentrates) and lithogeochdcal survey for gold did not locate any Triassic-age placer deposits in the northern Wadesboro and southern Sanford basins in North Carolina. A stream sediment geochemical program for uranium funded by the North Carolina Energy Institute did identify one and anomalous site (8.5 ppm U; 5 ppm Th) near Covenington, North Carolina and eighteen possibly anomalous sites (1-1.6 ppm U) . Five of the eighteen samples with uranium levels in the 1-1.6 ppm range have high thorium levels (112-853 ppm) and may indicate a monazite source for the uranium. Gold values as high as .83 ppm in the stream sediments and 9.3 ppm in the panned concentrates were obtained during the survey. Small (<.5mm) flattened grains of gold (1-4 grains) were observed along with coarse kyanite and/or monazite in some of the panned concentrates. A distinctive pattern of high gold values in the sediments was observed in the vicinity of Mangum, N. C. where Minard (13) reported values as high as 2.1 ppm £ram a Triassic lithology. Follow-up gold analyses on over 400 rock samples from twenty-eight exposures near Mangum failed to obtain any high values (<55 ppb). The presence of coarse kyanite, monazite and gold in panned concentrates may be from a source younger than the Triassic lithologies that the streams currently drain or adjacent Paleozoic rocks.

Jan 1, 1979

By Dieter Loh, Mathias Knoll, Florian Werres

When a new tunnelling project starts, it has been a vital tradition for decades to cast and erect master rings horizontally on a flat surface to demonstrate the compliance with dimensional tolerances. Some tenders ask for the erection of two or even three rings upon each other or repeated master ring erections at intervals throughout the project. Especially for large diameters, this is a challenging and risky task for the workforce in the segment factory. A truck-mounted crane is often necessary, and in some cases it can take up to a week to complete a master ring. The concept of virtual rings has the potential to replace this tradition by assembling master rings digitally instead of physically. This is based on a best-fit approach, considering the 3D coordinates from laser tracker measurements of segments or segment moulds. Building a virtual ring, a sub-millimeter accuracy can be achieved, the alignment of neighboring circumferential and ring joints observed, and the fit of bolt holes checked. The traditional method, on the other hand, is discussed controversially despite the significant amount of work and risks—particularly as the horizontal position of the ring and absence of gaskets do not simulate the reality in the excavated tunnel. This paper will highlight the technical aspects of virtual rings, as well as their pros and cons, illustrated by a case study from London Thames Tideway where a total of 30 physical master rings could be replaced by virtual rings.

Jun 13, 2023

By Joseph W. Johnson

General Electric introduced electric drive systems on 85 ton Off-Highway mining trucks in the early sixties. Due to favorable economics, trucks have increased in size to handle larger payloads. Series Motorized Wheel systems were developed to meet this demand. When the technology was available, General Electric switched from use of Series motors to separately excited motors with the added benefits of static exciters and simplified control. Over 20 years of electric drive experience have been incorporated in the STATEX drive systems, which covers truck sizes from 85 to 220 tons. This paper traces the drive system developments from the early stages to the present and takes a look at what&apos;s ahead.

Jan 1, 1983

By Lynn B. Hales

The Supervisory Computer System at Cities Service copper mine and concentrator at Miami, Arizona was installed at Pinto Valley in the spring of 1975. Design and specification [l] of the digital system was initiated jointly by key plant personnel at Pinto Valley and staff of Cities Service Research and Development Company. The Pinto Valley digital system [2] may be classified as a supervisory control system of hierarchical design. There are three fully independent satellite computers which retrieve and reduce the raw plant data from each of the three main operating areas - the primary crushing plant, the fine crushing plant, and the grinding and flotation plant. While the three satellite computers are core resident systems, the master computer is a disc-based operating system which also interfaces with a computer controlled on-stream x-ray analyzer system. Figure 1 illustrates the basic system configuration [3]. The software systems required to support a large system are quite diverse and vary greatly in function. The philosophy followed in dividing the software into three categories was designed to: 1) fully utilize existing process knowledge of technical staff; 2) delegate certain software tasks to outside sources already skilled and trained in software development; and 3) maintain final control over the design and operation of each system.

Jan 1, 1976

By M. Rotz

In the minerals industry today, the ?low hanging fruit? that once existed to debottleneck production and improve recovery, while meeting market needs for quality in mineral processing operations, are more and more difficult to find. Systematic methods for establishing plant mass flow, recovery, operational efficiency and control strategy in context with customer specifications provides the necessary insight and confidence for plant operators to prioritize improvement projects in order to maximize return on investment (ROI) for the site. The evaluation of aggregate and industrial mineral processing plants requires the following steps when projecting cost saving opportunities: collecting background data, conducting a base-line evaluation, analyzing specific unit-operation performance, defining investment options, prioritizing the selected improvement opportunities and the implementing process changes. The following paper describes the approach and challenges of developing an improvement plan for a dry and wet mineral processing operation.

Feb 23, 2014

By A. D. Davis, C. J. Webb

Brohm Mining Company&apos;s Gilt Edge Mine in the northern Black Hills was a surface heap-leach operation that was active from the 1980s until 1999. Financing problems and acid drainage concerns at the mine were reported in the late 1990s. In February of 1999 the Governor of South Dakota announced plans to request the U.S. Environmental Protection Agency to help clean up acidic water at the mine and reclaim the site. In July 1999 the parent company of Brohm, Dakota Mining, filed for bankruptcy in Canada. Because of the bankruptcy and environmental problems, the State of South Dakota intervened and began water treatment. The mine was declared a Superfund site in 2000. Hydrologic issues include the potential for acidic drainage from the site. The mine is at the headwaters of Strawberry Creek, which drains into Bear Butte Creek. About four miles downstream, Bear Butte Creek loses its discharge to swallow holes in the karstic Madison Limestone aquifer, a regionally extensive and valuable ground-water reservoir. Other concerns at the site include treatment of acidic water in mine pits and a waste rock dump.

Jan 1, 2002

By Peter W. Lipman

In the Rocky Mountain region, variations in Tertiary mineralization correlate with changes in tectonic setting and associated igneous activity that can largely be related to tectonics along the west boundary of the American plate. Successive settings include compressional tectonics and associated continental-arc igneous activity; transitional igneous types associated with intra- and back-arc extension; and basaltic or bimodal basalt-rhyolite assemblages associated with Basin and Range extension in- ward of a growing transform boundary between Pacific and American plates.

Jan 1, 2013

By B. A. Ashley

In 2007, Rosebud Mining Company (RMC) opted to extend the reserve base of Tracy Lynne Mine by developing through a sandstone channel. The extension provided access to approximately 6 million additional recoverable tons (approximately 8 years of mining) which originally had been deemed inaccessible. An evaluation of the mine?s existing ventilation system, which was designed to meet the needs of the original limited reserve, concluded that two ventilation shafts would likely be required to adequately ventilate the projected workings in the expanded reserve. To assist in the evaluation, a ventilation model of the mine was developed using Ohio Automation?s ?ICAMPS MineVent? software based on field data from Tracy Lynne Mine, prior ventilation survey experience at similar RMC mines, and relevant published sources. Model results suggested that the most economical shafts would be an 8-ft diameter return and a 4-ft diameter intake. Unfortunately, issues related to property leasing and shaft site permitting caused construction delays. Therefore, the model was also used and proved to be effective in prioritizing interim ventilation upgrades which could be implemented in order to maintain coal production. Model results indicated that the best interim upgrades included rehabilitating restricted entries and damaged stoppings and replacing the main fan with a higher pressure fan. From late 2010 to mid-2012, all interim upgrades and shafts were implemented. Current models and mine experience indicate that ventilation will not be the limiting factor for mining the additional reserve.

Feb 23, 2014