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By Philip A. Bucci

The Florida phosphate industry successfully uses froth flotation to concentrate phosphate in: the particle size range of approximately 28 to 150 mesh. However, as recently as 1965, coarse particles in the range of 14 to 28 mesh generally had not been beneficiated by conventional flotation methods at recoveries high enough to be considered adequate. It has been customary to upgrade this coarse material; by "agglomerate flotation" or "skin flotation" using belts, tables or spirals. While these devices have proved commercially effective, their capacities are much lower than those of froth flotation cells. To determine whether coarse phosphate material could be recovered successfully by froth flotation, Armour Agricultural Chemical Company began a series of pilot and plant tests; in April 1965. Objective of the tests was to compare over-all performance of a froth flotation cell design relatively new to the phosphate industry with results from the belt circuit at the Bartow, Fla., plant.

Jan 1, 1966

By P. G. Dempsey, J. R. Heberger, J. P. Pollard

During a mine disaster or emergency, underground air can quickly become contaminated. In these circumstances, all underground mine workers are taught to don breathable air supply units at the first sign of an emergency. However, no contemporary oxygen consumption data is available for the purposes of designing breathing air supply equipment specifically for mine escape. Further, it would be useful to quantify the oxygen requirements of breathing air supply users for various escape scenarios. To address this need, 14 participants crawled a distance of 305 m each while their breath-by-breath oxygen consumption measurements were taken. Using these data, linear regression models were developed to determine peak and average oxygen consumption rates as well as total oxygen consumption. These models can be used by manufacturers of breathing air supply equipment to aid in the design of devices that would be capable of producing sufficient on-demand oxygen to allow miners to perform self-escape.

Jan 1, 2015

By W. A. Crosby

All mine operators using explosives want to maximize explosive performance while minimizing blasting costs. Use of bulk explosive products such as AN/FO, heavy AN/FO, slurries and emulsions has greatly improved blasting efficiency over the years. Many operators have improved energy output from these products by adding aluminum. A major problem facing them is the fluctuation in aluminum price. The question therefore becomes, when is it economically advantageous to use aluminum in bulk products? This paper answers this question by first reviewing the energy output from the main types of aluminized and non aluminized bulk mixed explosives and then by showing the relationship between the different products on a cost and energy basis. The paper finally presents examples of charts and tables which will aid mine operators to conveniently select the most economically correct bulk explosive, including the level of aluminum addition.

Jan 1, 1991

Fundamental results obtained from research on the properties of the edge surfaces of kaolinite particles (~500 nm) are reported. Of particular significance was the development of the experimental protocol. Well-ordered kaolinite edge surfaces were prepared as an epoxy resin sandwich structure having layered kaolinite particles in the center of the epoxy resin sandwich. Images of the sectioned kaolinite edge surfaces were examined by atomic force microscopy (AFM), and the average thickness of kaolinite particles in this study was determined to be 38.3 nm ± 11.7 nm. Furthermore, the surface charge of the kaolinite edge surfaces was evaluated with a super sharp Si tip. The point of zero charge (PZC) of the kaolinite edge surface was determined to be below pH 4, in contrast to the traditional view that the edge surfaces of kaolinite particles may carry a positive charge at pH 4. This lower PZC of the kaolinite edge surface was attributed to the lack of isomorphous substitution in the silica tetrahedral layer when compared to the PZC for the muscovite edge surface. Our results are consistent with the particle aggregation and flotation behavior of kaolinite, and should provide the basis for improved flotation strategies leading to the efficient recovery and utilization of mineral and energy resources.

Feb 23, 2014

By L. L. Lien

In this economic age of high interest rates and softening mineral commodity markets, the mining industry is taking a hard look at how it conducts its business and where economies can be effected. The capital investment to build a new metallurgical facility or open a new property has traditionally attracted substantial investigation, analysis and management attention. The areas of mineral exploitation, financial feasibility, engineering and construction have been studied extensively and their management, although still difficult, have become refined disciplines.

Jan 1, 1982

By L. K. Holder

"The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), commonly known as Superfund, mandates evaluation of remediation alternative using nine criteria: (1) overall protection of human health and the environment, (2) compliance with ARARs (applicable or relevant and appropriate standards), (3) long-term effectiveness and permanence, (4) reduction of toxicity, mobility or volume, (5) short-term effectiveness, (6) implementability, (7) cost, (8) state acceptance, and (9) community acceptance. Many states have adopted these or similar criteria for remedy selection under state laws. Although not explicitly addressed in the CERCLA criteria, consideration of sustainability can be incorporated into these criteria. This paper explores how sustainability can be evaluated for remedy selection using the CERCLA criteria. INTRODUCTION Sustainability considerations can be incorporated into all phases of site remediation: • Site investigation (remedial investigation). • Remedy selection. • Remedial design. • Remediation construction. • Operations, maintenance, and monitoring. This paper focuses on remedy selection. Many have looked at remedy selection using sustainability criteria. However, CERCLA and corresponding State programs require remedy selection using mandatory criteria. This paper shows how sustainability can be explicitly considered using the mandatory criteria. REVIEW OF CERCLA CRITERIA First, we review the definitions of the CERCLA criteria. We then explore how sustainability criteria can be fit into the CERCLA criteria. Overall Protection of Human Health and the Environment This criterion addresses the degree to which each alternative is protective of human health and the environment, considering both long-term and short-term risks. Overall protectiveness is a ""threshold"" criterion, in that alternatives that do not achieve adequate protection of human health or the environment are eliminated from further consideration. Evaluation of this criterion is derived from the evaluation of the other criteria (e.g., long-term effectiveness and permanence, and short-term effectiveness). It is not an independent criterion, but more a summary of the overall evaluation."

Jan 1, 2015

By F. D. Wicks

This paper summarizes the direct operating cash costs for the Barrick Mercur open pit gold mine. A comprehensive, detailed system of cost management has been in effect for the life of the Mercur operation. This system provides the basic data for operations control and is the basis for drafting budgets as well as analyzing impact of change on operations costs. The ore body is complex geologically and metallurgically, requiring operators to pay close attention to mining and processing costs. The cost history provides data which enables analysis of changes in production levels, aging of the mine production fleet, and the impact of specific cost changes through time.

Jan 1, 1993

By S. A. Elmquist

Research activities performed by Cleveland-Cliffs Research and Hibbing Taconite plant personnel during the last decade have resulted in the development of an improved autogenous mill grinding circuit. Minus one (1) inch autogenous mill trommel oversize material, con-sidered to be a critical size, is magnetically cobbed and then crushed to 100% minus 3/8" prior to reentry into the feed end of the mill. Autogenous mill capacity increases, up to 25%, have been measured in pilot plant tests using this approach and are also anticipated for the Hibbing Taconite concentrator which presently has reached a 15.5% improvement.

Jan 1, 1994

By Paul J. Henkels

Synthetic gypsum is the calcium sulfate co-product of a number of industrial processes. Synthetic gypsum utilization as an alternative to the naturally occurring mineral continues to grow in the gypsum industry. In particular, flue gas desulfurization (FGD) gypsum produced by the electrical utility industry has had a significant impact and a far-reaching effect on the gypsum wallboard manufacturing industry. This paper will discuss the various synthetic gypsum sources verses natural gypsum and highlight issues of use in gypsum wallboard and related products.

Jan 1, 1999

By A. I. Johnson

The pegmatites of the Black Hills of South Dakota are the coarse-grained differentiates of the Harney Peak Granite. The Harney Peak Granite was intruded into the Pre-cambrian schist and quartzites and resulted in the Black Hills uplift. In the outer adzes of the granite intrusion occur the pegmatites. In the zoned pegmatites, representing the most highly differentiated portions of the parent magma, occur most of the minerals produced from pegmatites. These are of economic importance and they are the subject of this paper. The various mineral products will be taken up separately.

Jan 1, 1978

By C. E. Jordan

The fundamental properties of the Bureau of Mines patented dielectric separator were studied to provide insight regarding its design and operating characteristics. Force equations for mineral particles were derived and evaluated experimentally. High dielectric mineral recovery was proportional to the calculated effective dielectric force volume that surrounded each drum electrode wire. Electrode spacing was the most sensitive design parameter, requiring less than 0.4-cm electrode spacing for a good separation. Operating characteristics and ore characteristics were investigated. With a dielectric constant difference as small as 2, good separations were made on a laboratory scale at energy consumption below 12 kw?h/mt.

Jan 1, 1985

By J. A. Botín

Mining investment decisions are difficult since decision analysis is often based on scarce information. The sources of uncertainty in large mining investment projects are particularly numerous and are present in all evaluation stages. Hence the feasibility decision for projects of this nature will largely depend on how well these sources of uncertainty are managed to achieve bankable risk levels. The risk associated to the construction stages of a mining project is particularly difficult to quantify, mainly because the large number of variables affecting constructive yields, and the complex interactions among constructive resources. This investigation focuses on developing quantitative simulation models and tools to increase the value of a mining project by means of an optimization of the preproduction equipment fleet. The models were validated through their application in the Chuquicamata Underground Mining Project.

Feb 23, 2014

By V. Gangrade, J. Addis, S. Vanderslice

Researchers at the National Institute for Occupational Safety and Health (NIOSH) are conducting research to improve the ventilation of large-opening underground stone mines. The mine ventilation in these mines are characterized by: (1) challenges related to keeping airflow velocities high enough to effectively remove or dilute airborne contaminants, (2) low pressure losses needed to move large air volumes of air, and (3) costly stoppings needed to direct ventilation airflows. Each of two field studies was dedicated to specific focus areas. The first focus area was the characterization of underground mine ventilation airflow. The primary means of airflow control in stone mines is through the use of freestanding booster fans. The primary goal of this study was to identify the effectiveness of various fan types and optimize their placement. Both traverse and grid-based airflow readings were taken at various distances from the fans, ranging from 70 ft to 425 ft away from the fan. The air readings were taken using a vane-anemometer and a handheld hotwire anemometer. The data was used to develop precise computational fluid dynamics models. The second focus area was to determine diesel particulate matter (DPM) concentrations in the mine. For large-opening underground stone mines, controlling DPM exposures dictates the design of the ventilation system. Therefore, researchers carried out the DPM sampling campaign to identify potential areas of concern within the mine. The samples collected during the campaign were analyzed using NIOSH Method 5040. The sampling was done using the Mine Safety and Health Administration’s (MSHA) compliance sampling methodology.

Feb 1, 2023

By Gilles Recher, Jörg Riechers, Albert Lueghamer

"INTRODUCTIONIn view of a global trend towards urbanization, more and more trunk sewers and combined sewer overflow tunnels (CSO) with medium to large diameters and the corresponding link sewers are currently built and under design. Shielded tunnel boring machines using segmental lining as tunnel support represent an efficient solution for construction of new wastewater and supply tunnels. Especially in the field of sewers, the durability of concrete structures both exposed to any groundwater present on its exterior and to aggressive waste water as well as gases on its interior is a key requirement. Despite thorough research on segmental lining and mechanized tunneling machinery, conventional thermoplastic liners show comparatively minimal progress in terms of practical advancements. This is in contrast with the development of the latest segment embedded high density polyethylene (HDPE) system. Based on experiences achieved, this paper discusses the latest development of an integral protective lining system in respect of material characteristics and its adaptability to both project and customers’ demands. Reviewed performances, as the bondage behavior of the embedded HDPE system at axial stress loads due to acting thrust cylinders during ring build as well as the ability to drain pressurized water behind the embedded membrane, tested at full scale segments, are also presented. The paper is round off by presenting first details of sewer projects endeavoring to utilize this cutting-edge solution for an integral concrete protection, which will be commenced beginning of 2016.CASE HISTORIES ENCOURAGE ADVANCEMENTS Past experience has shown that unprotected concrete surfaces as well as chemical based linings such as coatings, sprayed linings and cured in-place-systems cannot reach the desired life times. Also the fact that in deep tunnel sewer system hardly maintenance is possible, a durable and maintenance free system is required which only can be reached by applying mechanical anchored HDPE (CPL)."

Jan 1, 2016

By P. Roghanchi

The difficulties associated with performing direct tensile strength test lead to development of indirect test methods, which are simple, less expensive, and less time consuming. Splitting tensile strength test (Brazilian test) is performed by applying two opposite concentrated compression load across the diameter of a disk specimen until the failure occurs along the loaded diameter. Theoretically, the load is applied over a small width as a line load, however, by increasing the load, the contact width between the loading jaw and the specimen increases as the specimen deforms. The main aim of this study is to investigate the stress distribution in (1) regular Brazilian specimen in traditional tests with loading jaws and (2) flattened Brazilian specimen with flat platens. A series of the splitting tensile strength tests and uniaxial compression strength tests are performed on three rock types: rhyolite, basalt, and limestone. Further, Numerical modeling studies are performed to investigate the effect of the contact between jaw and Brazilian specimen on stress distribution in the disc specimen based on the results from the experimentation. Finally, the stress distribution in the traditional Brazilian test specimen and the flattened end Brazilian test specimen were compared.

Feb 23, 2014

By M. Sears, G. S. Esterhuizen, Z. Khademian

According to the 2010-2019 Mine Safety and Health Administration (MSHA) accident report database, 91% of reported ground control accidents in U.S. longwall mines were caused by roof instability. Gateroads are subject to significant changes in loading conditions from the development to the longwall abutment loading phases. When combined with thinly bedded shale roof, found in many U.S. longwall coal mines, the design of efficient roof support becomes challenging. In previous work, the Bonded Block Method (BBM) modeling of roof by UDEC was validated against field extensometer measurements in a longwall gateroad entry roof at a 180-m depth of cover. The BBM was shown as capable of capturing delamination and buckling of shale roof, one of the main roof instability mechanisms in longwall mines. This paper presents the recent findings on the roof-support interaction using BBM models of the same longwall entry. The effects of cable bolts, roof bolt density, and strap support on potential roof instability are studied. These types of studies are difficult and costly to conduct in an operating mine. Results show how the contribution of bolts, straps, and cable bolts can be quantified using the BBM models. The study demonstrates the potential for BBM numerical models to help understand the complex roof and support system interactions and to assist with optimizing gateroad support systems.

Feb 1, 2023

By W. S. Weldon

The use of spiral separators for the beneficiation of fine coal typically in the size range -2+0.1mm is now well established process technology. Developments during the mid 1980's resulted in the production of cost effective, efficient large diameter coal spiral separators. Recent developments and research have been geared to optimize metallurgical performance, materials handling and equipment geometry of large diameter coal spiral separators.

Jan 1, 1997

By S. Frisch

Selenium (Se) in effluent waters has become a significant challenge for a number of industries. Toxicity studies and new reports of occurrence have certainly caused increased scrutiny and actions in the mining industry today (Sandy, DiSante, 2010). While initial activity in addressing selenium-laden waters were conducted in the coal mining industry, today a much broader range of mine types are beginning to search for solutions to selenium treatment of their mining waters, including both hard rock mining operations (gold, nickel, zinc, etc.) and soft rock mining (phosphate, uranium, etc.) Throughout North America, new regulations covering selenium discharge are either in place or being developed. While a number of physical/chemical approaches show promise in selenium treatment, when considering optimal cost and treatment efficacy issues, biological treatment ? particularly fixed-film biological treatment - is reported to be one of the most promising approaches to managing selenium-containing waters. Among biological treatment options, the fluidized bed reactor (FBR) has undergone extensive pilot testing for Se treatment in the last three years, including eight pilot programs, and the first FBR system is now operating at a coal mining site. In all tests, the FBR has been shown to be a highly cost-effective approach to selenium treatment based on its physical and performance characteristics. This is consistent with its history for reaching low levels of treatment in similar service for other oxyanions including perchlorate, nitrate and various metals. With the results from the most recent testing, the technology has been shown to be adaptable to an ever-broadening range of influent water conditions and flow rates, in varying terrains and weather conditions. Selenium occurs in various valence states from -2 to +6 (Sobolewski, 2005). The speciation of selenium plays a critical role in understanding the effectiveness of any approach for removal, especially to low levels. Elemental selenium is insoluble and has little effect on living organisms. Colloidal fractions are known to occur. In aqueous environments such as coal mining runoff, selenium is most often found as the oxygenated anions of selenite (SeO32-, Se4+) and selenate, (SeO42-, Se6+). Selenium is commonly found in mining waters in concentrations ranging from 3 to >12,000 µg/L. The U.S. National Primary Drinking Water Standard MCL is 50 µg/L for selenium (EU 10 µg/L; WHO 40 µg/L). The National Fresh Water Quality Standard is 5 µg/L for selenium. The U.S. Fish and Wildlife Service has recommended that the National Fresh Water Quality Standard be lowered to 2 µg/L to protect fish, waterfowl, and endangered aquatic species. Several states have followed with enforcement actions at these same low levels. In Canada, permits may require stakeholders to monitor levels in water or biota, or to comply with guidelines, at either the National or Provincial levels, which can be as low as 1 or 2 µg/L in surface waters. Treatment of selenium in all mining waters presents a series of challenges. It can be present in relatively dilute concentrations and in streams with variable and often high flow rates. It can be present in many soluble and particulate forms, which may affect process design and treatability. The conditions of influent selenium-containing waters can vary, with issues such as temperature, pH, total dissolved solids and other contaminants affecting the ability to remove selenium selectively and economically. Treatment of selenium often results in the generation of a concentrated by-product requiring disposal, and re-release from residuals can occur. Beyond these issues, the physical environment of a mining operation can offer challenges such as remoteness and harsh and/or cold weather. Currently available selenium treatment technology (Table 1) includes biological treatment and a number of physical-chemical processes ? such as ion exchange, membrane filtration and adsorption ? that vary widely in efficiency and cost. Most treatment options remain either too costly and/or unproven for selenium-containing streams for reasons that include poor removal efficiency, variability in volume and composition of influents, system sizing and logistics considerations, as well as operating requirements.

Feb 23, 2014

By W. Petruk

Mineral liberations that would be obtained by grinding an ore to a specific size can be predicted by analyzing unbroken ore pieces, and mineral liberations in ground ores and mill products can be determined directly by image analysis. Predictions of mineral liberations are made by measuring size distributions and textures of mineral grains by image analysis, and using liberation models. Ground ores and mill products are analyzed to determine the proportion of mineral that is liberated, and the data are used to evaluate mineral behaviour during mineral beneficiation. The liberation data for minerals in a suite of mill products from a circuit are processed by a materials balancing technique to calculate recoveries of minerals in different types of particles throughout the circuit. The liberation-materials balance data define mineral recoveries; define the behaviour of an ore in a concentrator, pilot plant or bench test; and indicate whether recovery improvements are possible and/or feasible.

Jan 1, 1991

By Michael Davis

In the fairly recent past, with a history of cheap and abundant energy, it has been possible to predict with reasonable confidence that world energy demand would continue to double about every 15 years. Those who attempted to forecast the role of nuclear energy in future electricity generation could also start with the fairly safe assumption that electricity demand would increase even faster : with a doubling in demand about every 10 years. To estimate the likely future world demand for uranium it was then necessary to introduce a number of other assumptions including the rate of penetration of nuclear energy, the timing and the specific fuel requirements. This series of assumptions naturally compounded the uncertainty, but, remarkably, usually led to future uranium demands being overestimated. Such a bias which has almost always been observed in predictions made over the past 20 years has increasingly made uranium producers sceptical when expected to match the forecast demand with increased production capacity and supporting reserves. This scepticism has, of course, been reinforced by the persistence so far of a buyers' market in uranium throughout the entire period of emergence of commercial nuclear electricity generation.

Jan 1, 1974