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By Michael Brittan

For several years, Independence Mining Co. (IMC) has routinely used oxygen fluid-bed roasting to pre-oxidize refractory gold ores ahead of conventional carbon-in-leach (CIL) processing. Oxygen serves jointly as the fluidizing medium and the combustion gas. This technology has proven to be reliable, environmentally sound and cost-effective. IMC is a subsidiary of the Minorco group. The company operates the Jerritt Canyon (a joint venture with FMC Gold) and Big Springs gold mines in the Independence mountain range north of Elko, NV. Ore bodies in the range contain characteristic refractory ore. It requires pre-oxidation ahead of conventional CIL processing. This article describes the technology developed specifically to treat these difficult ores.

Jan 1, 1995

By Simon J. McDonald

In late 2007 Neptune Minerals Plc. commissioned Genesis - a leading consultancy and engineering company affiliated to the Technip group - to undertake a Seafloor Mining Conceptual Study for mining of Seafloor Massive Sulphides (?SMS?) in Neptune?s New Zealand licenses. A key deliverable of the study was information to de-risk the perception of SMS mining for investors the minerals, and that deep-sea mining of SMS material is technically feasible, commercially viable and can safely be managed as a sustainable marine resource industry. The aim of the study, completed in April 2008, was to evaluate alternative existing marine technologies for seafloor mining, ore lifting, dewatering and surface offtake, considering the following parameters: ? Efficiency; ? Reliability; ? Safety; ? Environmental impact; and ? Cost

Jan 1, 2008

By Lynton Gormely

Oxygen transfer in a stirred tank bioreactor has been modelled mathematically to determine the trends in transfer efficiency (kg transferred per kWh) with transfer rate, tank depth, superficial velocity, and mixer power.

Jan 1, 1990

By Scott G. Britton

In this chapter, I shall discuss railroad con¬struction for modern underground coal mines. Because men, materials, and supplies are being moved more often and farther by rail, the ef¬ficient and safe construction of the system takes on new importance. Most large coal mines are opting to use track haulage over other support transportation systems because of cost, ease of installation, reliability, and other factors. En¬gineers tackling the problem of designing such a transportation network must be aware of all the steps required for an effective transportation system design. This chapter discusses all aspects of efficient trackwork construction. The areas covered in¬clude design factors, laying the track, installing turnouts and switches, and installing trolley wire. Each area includes a description of the steps needed to complete the work.

Jan 1, 1983

By Aladar B. Dory

INTRODUCTION Anyone familiar with the problems of hardrock mining will agree that the majority of the serious dangers present in mining are quite visible and obvious to any person reasonably familiar with the profession. Having unsecured, unscaled back over ones head, gives one a very good chance of ending up under a caved in mass of rock. Staying too close to a blast gives one almost a certainty of being hit by a flying rock. Too little oxygen in the air will very quickly lead to loss of consciousness and death. One walks only so much over deep, unsecured openings before he falls into them. It is because of this clear visibility of the conventional health and safety hazards that mining regulations in almost all jurisdictions world-wide are a more or less comprehensive collection of "shalls" and "must nots" of good common sense. When basic rules of common sense safe working practices are at stake, there is little room for dialogue and compromise. The mine inspector is then observing, during his inspection, how well the mine follows these common sense rules. RADIATION AS A HIDDEN DANGER Radiation in mines is a risk, the impact of which does not demonstrate itself immediately. It is first of all a potential risk. Two individuals exposed to identical radiation will almost certainly be effected differently, if at all. This is certainly true of exposures and doses one might encounter in the mines today. We hear very often the phrase: "there is very little known about the effects of radiation". It is one of the most misused and misunderstood half-true statements. I would doubt that there is any other carcinogen whose effects have been studied as extensively as the health effects of radiation. Where the statement is correct is regarding the knowledge of the quantitative assessment of the risk of low level radiation exposures. The reason for this uncertainty is that the magnitude of their health effect is very close to the health effects of natural radiation, cosmic radiation and the effects of other carcinogens such as industrial pollution, hydrocarbons from cars and other chemicals we have grown accustomed to using. As far as lung cancer is concerned, the effects of wide use of tobacco probably outperforms any other single substance. All this having been said, the bottom line is still unchanged. Radiation exposure, in most cases mainly radon daughter exposure, was and still is one of the health hazards of uranium mining and as such has to be controlled to the best of our ability. Various jurisdictions have adopted different approaches to the control of radiation exposures of uranium minemill workers. The following sections of this presentation will attempt to explain the regulatory approach taken in Canada. THE CANADIAN REGULATORY PHILOSOPHY As indicated earlier, the health effects of low level radiation are quantitatively not yet defined and no proven threshold of radiation exposure exists. The Atomic Energy Control Board's (the Board's) regulatory system is based on the basic assumption that there is no absolutely safe limit of radiation exposure below which there are no health effects. Theoretically we should therefore strive to reach zero exposure. It is obvious that this objective cannot be reached in real life. The objective of the regulatory process therefore has to be to achieve radiation exposures of the workers that are as low as reasonably achievable, social and economic factors taken into account. This, of course, is the internationally acclaimed ALARA principle put forward by the International Commission on Radiological Protection (ICRP). To avoid any misunderstanding it is worth emphasizing that the ALARA principle is applied to achieve exposures below the regulatory limits which must not be exceeded in normal operation of any nuclear facility including uranium mines and mills. The present regulatory limits for radiation exposures of atomic radiation workers are based on the recommendations of the ICRP and they are almost universally accepted. They should ensure that the risk from radiation exposure is not greater than the risk associated with working in a comparatively safe industry. Basically, there could be two extreme approaches to the regulation of uranium mining and milling. One extreme approach is to develop very extensive and detailed regulations and requirements covering all aspects of radiation protection. This is a somewhat autocratic approach to the regulatory process. This approach has two very serious shortcomings. If detailed requirements are set in regulations, due to the great variations of actual conditions at various mine-mill facilities, they have to be set as a compromise between the desirable requirements and those which could be met by practically all facilities. This approach takes away from the management of the facilities the initiative to strive for improved conditions. Requirements are spelled out in clear, understandable targets and the only worry of the management is to comply with these targets. One of the basic duties of management is to manage the operations in the most effective way with the maximum health and safety of the workers in mind.

Jan 1, 1981

By A. Mai, J. S. Wakeman

The progress results of a pilot plant study on the effects of ball top size and other mill operating parameters are reported. Test series on taconite and quartzite crude ores using a 1.7-m diam primary mill in closed circuit with a vibrating screen indicate clear trends on the improvements of mill throughput and power consumption when using larger diameter balls. Possible effects on mill liner and ball consumption as well as future research plans are discussed.

Jan 1, 1987

By Thomas O’Neil

Part 2 of this article continues with a discussion of features that distinguish contemporary investment analysis in mining from earlier methods. Part 1 traced the evolution of evaluation methodology from the traditional and discounted cash flow methods to the present. Quantitative investment models of the past 20 years played an important role in mine evaluation, but a new integrated approach to mine investment decision-making is now developing because of growing economic, technical, and political uncertainties. One of those uncertainties -inflation-was discussed in Part 1. Increased Risk At a time when mineral production technology and analytical evaluation tools have never been more sophisticated, it may seem anomalous to claim that mining ventures are riskier. Whereas technical risk has, indeed, been notably reduced, business risk the chance of a major loss due to market factors-has increased. This has been caused by two factors: the rapidly rising capital requirements of new projects and increasingly unpredictable future economic conditions. These difficulties are compounded by the long lead times of large, new mining projects. Rising Capital Requirements A $100 million investment is no longer considered to be a large mining project in most cases. For a large metal mining project, the total cost of the concentrator alone can exceed $100 million. Amoco Minerals' Thompson Creek molybdenum mine being developed in Idaho will cost over $350 million, for a relatively modest sized (23-kt/d or 25,000-stpd) ore operation with no extraordinary features. For a major grass roots copper operation producing blis¬ter or refined copper, the capital requirements are billions of dollars, not millions. Project costs are higher for two reasons. One, the projects themselves are larger; and two, the capital cost per unit of production is rising rapidly. Projects are larger because lower grade ores, yielding smaller margins, must be mined in greater volume-particularly in view of the high fixed costs of modern technology. When analysts contemplate any capital project, an important consideration is the minimum economic size of the facility. This is the smallest size that can be built and still be competitive on a total unit production cost basis. In the conventional copper smelting business, for example, a production rate of at least 91 kt/a (100,000 stpy) of blister copper is about the absolute minimum for reducing unit fixed costs to competitive levels. Clearly, many variables affect the minimum economic size of a mining facility, but with few exceptions that size continues to grow. Unit capital costs of new mining projects also are continuing to rise. The accompanying table shows that the capital costs in primary copper production have risen faster than the cost of living. Of particular note is the capital charge of over $1.70/kg (77411b) required for a new, fully integrated facility in 1981. Thus, the mid-1982 copper price would not even cover the cost of capital for a new copper producing complex without considering the direct operating costs for such a facility. The breath-taking costs of new mining projects are caused by factors such as increasingly complex technology, the rising social costs of creating attractive living and working conditions for employ¬ees, and the expenditures re¬quired for environmental protec¬tion. For whatever reasons, how¬ever, unit capital costs in mining continue to exhibit staggering growth rates. Future Economic Conditions Risk is not only a function of the size of the potential loss-an im¬portant measure of which is the capital intensity of mining dis¬cussed above-but also of the like¬lihood of incurring the loss. It is here that the ever increasing lead times of mining projects and the glaring limitations of economic forecasting are so important. In comparison to nearly all other in¬vestments, mining has more capi¬tal at stake for a longer period of time before commercial uncer¬tainty is resolved by distant eco¬nomic conditions that are subject to high forecasting errors. A sobering example of the pre¬ceding points occurred with the Lakeshore copper mine in south¬ern Arizona that Hecla Mining Co. undertook to finance and manage in 1969. The project was a joint venture of Hecla and the El Paso Natural Gas Co. and included two mines-one producing oxide ore and a second in the sulfide zone¬and a complex processing facility producing both electrowon cop¬per cathodes and copper precipi¬tates. The project originally was

Jan 12, 1982

By Alan L. Mierke

West Virginia's economy has been closely linked with coal. West Virginia is consistently one of the top three coal-producing states. Its 149 Mt (164 mil¬lion st) produced in 1992 represented 16.5% of total US coal production. In recent years, the state's economy has experienced a diversification away from its traditional employment base of min¬ing and heavy manufacturing. However, the coal industry remains an integral part of the lives of West Virginians. Coal is mined in 33 of the state's 55 counties. In many of these counties, the coal industry is the largest private employer and contributor to the economy. West Virginia has three major coal-producing regions. The northern region produces coal high in gas and sulfur content (steam coal). It is consumed primarily by utility and industrial markets. The southeast region produces high-grade coal low in sulfur content but high in carbons and Btu (metallurgical coal). The southwest region produces metallurgical and steam coal. The high-grade metallurgical coal is used in the production of coke for steel manufacturing. Metallurgical coal also comprises the majority of coal exported from the United States. During 1993, West Virginia was the country's largest exporter of coal, accounting for 44.5% of total US coal exports.

Jan 1, 1995

By Lorenzo Pellegrini

The respect of EPB reference pressure during TBM advance and hyperbaric activities, the complete and effective filling of the annular gap between tunnel lining extrados and the excavation section and a well organized monitoring system, to control surface settlements and ground distortion, are items of utmost importance in EPB tunnelling process. The paper describes how these concepts have been applied while excavating in the difficult underground conditions found at Sao Paulo (Brazil) during the execution of the Sao Paulo Metro Line 4-Lot 1. In this project, the annular gap has been filled by two components type, cement grouting. The back feed of the extensive monitoring campaign carried out to check the surface settlements during the excavation and hyperbaric maintenance operations will also be described in the paper.

Considerable attention has been given to the restoration of low-level radioactive (<1000 pCl/g) sites contaminated during the early years of the atomic energy program. Current clean-up activities which involve the relocation of contaminated soils to licensed disposal sites have been shown to be very costly due to the large volumes of soils which must be excavated, transported and stored. Recent characterization studies conducted at Virginia Tech suggest that the volume of soil requiring disposal can be greatly reduced using mineral processing techniques such as classification, density separation and froth flotation. This article discusses the application of these technologies for soil remediation and describes a conceptual flowsheet for treating soil samples from two contaminated sites.

Jan 1, 1997

By J. Brinen, D. R. Nagaraj

Secondary Ion Mass Spectroscopy (SIMS) was used to study copper ion adsorption, and its effect on subsequent sulfide collector adsorption, on pyrite and pyroxene minerals under flotation related conditions. Copper was found to adsorb on both of these minerals and cause enhanced sulfide collector adsorption. The distribution and depth profile of copper and collector on these mineral surfaces were obtained by using SIMS in the imaging mode. The results of this study have provided a valuable insight to understanding pyrite and gangue flotation observed frequently in operating plants.

Jan 1, 1995

By S. Nickson, M. Grenon

Oriented borehole data provide the means to characterize a rock mass. In this paper, the geomechanical caving potential of a hard rock mine project is investigated. In particular, the influence of random joints to the resulting block size distributions is addressed. The implications of this approach in preliminary investigations on the choice of mining methods are discussed with reference to one site.

Jan 1, 2003

By P. R. La Pointe, H. C. Ganow

The production of both over- and undersized coal fragments is a constant problem to open pit operators in the Powder River Basin. Operators strive to achieve production blasts that economically minimize the weight percentage of over- and undersize coal. However, natural fractures influence blast fragmentation, and can impose limits on the final fragment size distribution. ARCO&apos;s Anaconda Minerals Company studied the limits placed by natural fracturing as part of a wider geotechnical study of the Wyodak Coal in the eastern Powder River Basin, Campbell County, Wyoming. Measurements of fracture orientation, size and spacing were made at ARCO&apos;s Black Thunder Mine. These data were used to form statistical distributions for natural fracture size, spacing and orientation. An algorithm was created to select fracture properties at random from these distributions and to form hypothetical blocks. The blocks were then numerically "sieved" to derive pos- sible particle size distribution curves. These curves are compared to fragmentation results from samples taken from three test blasts. All test blasts yield very similar lognormal fragment size distributions. The median particle size varies from 1.25 to 2.0 in.(3.2 to 5.1 cm), the mean from 4.0 to 8.5 in. (10.2 to 21.6 cm). The standard deviation was about 1.6 in. (4.2 cm). Coal fines (fragments < 0.25 in. or 0.64 cm) are about 15%. Calculated fragment distributions for the natural fractures predict the median size well but underestimate the variance. Algorithm modifications to account for processes known to occur in the comminution zone near the blast hole significantly improve the match in the fine coal size range. The match suggests that spacing of fractures, rather than fracture length, controls the formation of fine- and medium-sized fragments. On the other hand, the oversize coal is controlled by the fracture lengths, rather than the spacing. Data from subsequent test blasts support this idea. By increasing delay times from 8 msec to 17 msec, engineers were able to reduce fines to 7% - 10% but could achieve no further improvement, despite changes in shot pattern geometry, decking and hole size. The hypothetical fragment distributions show that, even without blast enhancement, about 5% of the natural coal blocks are fine-sized.

Jan 1, 1986

By James A. Finch, Xiang Zhou, Yue Hua Tan

Widely used as collectors for nonsulfides, amines also show some frothing properties. Evaluating frother functions of amines and their combination with conventional frothers addresses whether one reagent delivering both collector and frother functions compromises the efficacy of either. From the findings, whether blending with frother confers any benefit requires knowledge of the residual amine concentration. If it is below about 10 ppm, blending eliminated coalescence, but there appears to be no benefit if the concentration is above 15 ppm.

By Ray Soper

Important progress has been made in developing the K-Process as an alternative to cyanide as a method of recovering gold from ores and other materials.

Jan 1, 1998

By C. E. Brechtel

Bench cut-and-fill stopes with heights between 85 and 105 ft are being excavated in the lower levels of the B-NEATH Zone. Estimates of pillar strength and pillar loading indicated a high probability of pillar failure. Some changes in mining practice were made to minimize impacts of pillar failure and a rock mechanics instrumentation program was employed to monitor stability during mining of the first stopes. Limited pillar failure, in the form of destressing, was observed in the initial stopes; however, global stability during mining was good. Instrumentation data indicated that predictions of pillar strength and stress were quite close to field results.

Jan 1, 1989

By Lennart Bergstedt

Boliden Aktiebolag, the prime base metal mining company of Sweden, annually treats some 11-12 million tons of sulphide ore in nine concentrators. Its first flotation plant was established in the early thirties for the complex Boliden ore. Since then, the number of mines and plants has gradually increased. Considerable effort has been devoted to the development of all phases of the technology of ore prospecting, mining, milling, smelting and refining. This has been necessary due to the complex and low-grade ores. The development of concentration has mainly been directed toward the arts of grinding and flotation. During the forties and fifties, open-stage fine crushing followed by two-stage grinding in rod and ball mills with cyclone classification was successfully introduced and used throughout the plants. The increasing cost of grinding media led to studies of an autogenous grinding technique as early as 1945. Basic test work commenced during the early fifties, with a. number of ores tested for pebble grinding. In 1956 a new pilot plant was built, with equipment installed for the continuous testing of pebble grinding and, later, for primary autogenous grinding of run-of-mine ore. The intensive test work showed that pebble grinding was feasible in almost all of the plants. At this early stage of testing, however, the merits of autogenous grinding could not be fully evaluated. As a. consequence the rod mill/ball mill grinding systems were converted to rod mill/pebble mill systems whereever possible. In parallel with the converting of grinding systems the development work concerning the merits of autogenous grinding went on. The major result

Jan 1, 1977

By John N. Murphy

In fiscal 1996, the US Congress directed that the US Bureau of Mines (USBM) be closed. Certain functions were reassigned to other agencies. The remaining employees were separated and the unoccupied sites were decommissioned. As a result, 12 locations were closed and about 1,200 employees were terminated in March 1996. About 600 employees at five locations were reassigned to other federal agencies. This article provides a summary of the continuing functions, the agencies involved and the points of contact for each continuing function. The functions that were discontinued are also identified. The functions that have been maintained and transferred to other agencies are: ? Portions of USBM&apos;s Mineral Information and Analysis program formerly conducted in Washington, DC and Denver, CO were assigned to the US Geological Survey (USGS). ? The Mineral Land Assessment program in Alaska (Anchorage and Juneau) was transferred to the US Bureau of Land Management (BLM). ? The Health and Safety Research program in Pittsburgh, PA and Spokane, WA was reassigned on an interim basis to the US Department of Energy (DOE). In fiscal year 1997, it was permanently assigned to the National Institute for Occupational Safety and Health (NIOSH). NIOSH is part of the Centers for Disease Control and Prevention within the US Department of Health and Human Services. ? Environmental Research at Pittsburgh, PA was assigned to DOE. ? Materials Research at Albany, OR was assigned to DOE. ? The helium program was assigned to BLM, where it will be managed pending privatization. ? Coal and noncoal mine maps were transferred to the Office of Surface Mining Reclamation and Enforcement (OSMRE). The following locations were closed: ? Research centers in Denver, CO; Minneapolis, MN; Reno, NV; Rolla, MO; Salt Lake City, UT and Tuscaloosa, AL. ? Field operations centers in Denver, CO and Spokane, WA. ? Washington, DC headquarters office. To provide a concise picture of all of the affected functions, the following is a synopsis of the USBM program functions and facilities immediately before the closure. There were two principal programs: information and analysis, and research.

Jan 1, 1997

Effective ground control in the gate entries, particularly in the tailgate travelways, is essential for safe longwall mining. Longwall pillars maintain gate entry stability and carry abutment loads. To answer the need for effective longwall pillar design, an empirical method called Analysis of Longwall Pillar Stability (ALPS) was proposed several years ago. Some recent research at the Bureau of Mines has focused on the refinement and verification of the ALPS method. ALPS was originally developed from field studies in which multiple stressmeters were installed in longwall pillars and monitored during mining. Several new field studies have now been incorporated into the ALPS data base. The field measurements have&apos; been used to verify formulas for predicting abutment strength and pillar loads, and to develop an expression for the distribution of the abutment load.

Jan 1, 1989

By Ronald K. Frobel, Christopher J. Wienecke

Geomembrane systems and associated geosynthetics such as geotextiles, geonets, geogrids and geocomposites have been used in precious metal heap leach and tailings facilities for many years. Geomembranes have been used in the heap leach process in pad design and solution recovery ponds as well as associated collection channels as the primary liquid barrier to contain and collect metal bearing leach solution. Geomembrane systems offer an effective, low cost alternative to other containment methods such as compacted low permeability soils, asphalt or concrete. In the 19BO's, rigid High Density Polyethylene (HOPE) liners were used to a great extent with a gradual transition to the use of the more flexible Very Low Density Polyethylene (VLDPE) and Polyvinyl Chloride (PVC). These three geomembrane systems have been used successfully in precious metal heap leach solution containment. Predominant material thicknesses have been 30 and 40 mil for PVC, 40 and 60 mil for HOPE and VLDPE. Variants in recent years have included roughened HDPE and VLDPE to provide higher surface friction characteristics, as well as newer polymer materials such as polypropylene. In addition to providing an economical method for providing enhanced solution recovery, geomernbranes are also providing the primary liquid barrier for prevention of groundwater contamination. Because heap leach solution chemical components and dissolved metal constituents are classified as toxic substances, they are subject to environmental regulation. Many regulatory agencies are still developing guidelines for heap leach pad design, however a geomernbrane liner system is often used as a single liner or in conjunction with other materials to form composite double or even triple lined systems. "Other" materials can include alternate layers of drainage aggregate, geotextiles, clay layers and other geomembrane or geocomposite layers.

Jan 1, 1993