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By W. Holding

Since the 1975 International Mine Ventilation Congress in Johannesburg there has been a trend in South Africa towards making the mine ventilation departments responsible for monitoring the total environment. This includes the taking of noise and illumination measurements and there is in fact a debate taking place as to whether the departmental title should be changed to 'Environmental Control Department'. The organisers of the 2nd international Mine Ventilation Congress have decided that noise and illumination will not be included as Congress subjects and 'Total Environment' includes only those facets which are open to debate at the Congress. The choice of mine is significant in that while most Congress papers from South Africa will be devoted either to coal mining or to the somewhat unique deep level gold mines, Prieska Copper Mine is a mine which can easily be identified with similar mines in many other parts of the world. The mine is situated some 750 km south west of Johannesburg and about 600 km north east of Cape Town. Current production (ore and waste) is about 340 000 tons per month and the total underground labour force is just over 2 000. The ore body is a massive sulphide, the main minerals being copper and zinc and the method of mining is sub-level open stoping. Daily average surface temperature conditions range from 85°F (29.5°C) dry bulb and 69.8°F (21°C) wet bulb in mid-summer to 42°F (5.5°C) dry bulb and 36.5°F (2.5°C) wet bulb in mid winter. The information presented in-this paper is limited to what can be gathered by mine ventilation staff as part of an on-going exercise and is obviously not as comprehensive as would be the case if a fully equipped research establishment were to become involved. The paper will be divided into three sections 1) Gases 2) Dust 3) Heat In each section statutory and/or other standards will be set down followed by a discussion of assessment and in some cases control methods.

Jan 1, 1980

By Alena Conrads, Markus König, Markus Scheffer, Markus Thewes, Hannah Mattern

"INTRODUCTION In recent years, the development of tunnel boring machines has revolutionized the tunneling industry. The general structure of a tunnel boring machine (TBM) can be described as a multi-component system. To achieve high performance rates, machine elements have to perform reliably. Performance losses and interruptions of the construction process should be prevented or at least, reduced to a minimum. In order to achieve high advancing rates, cutting tools must be in good condition at any time. Furthermore, failure of individual tools might result in increased and faster wear of remaining structural components. For this reason, maintaining and replacing cutting tools is crucial to prevent project delays due to insufficient boring performance. Precise prognoses concerning the prevailing geology are infeasible and thus, efficient scheduling of maintenance actions is challenging. The intention of this work is to analyze different approaches of TBM maintenance in soft ground. Different strategies are analyzed by the use of a simulation approach. Cutting tool condition is regarded as performance limiting factor. The maximum operation time of the cutting tools is determined using the “Soil Abrasivity Index”. A case study serves to show the effects of different maintenance strategies on total project duration. SCHEDULING OF MAINTENANCE ACTIONS Scheduling maintenance actions of single and multi-component systems concerns numerous fields of industrial production. Concentrating on mechanized tunneling in soft ground, cutting tool maintenance represents the most common reason for intermission of advance (Köppl 2014). In literature, time-based and condition-based maintaining techniques are widely discussed. The following section outlines the principles of time- and condition-based policies. Furthermore, examples for their applications in recent research are given. Time-Based Maintenance In general, the time-based maintenance approach assumes that the failure behavior of the system components is predictable. Maintenance actions are scheduled according to predefined intervals (e.g., hours, days, weeks). A detailed analysis of preventive repair times or interval forms the basis for maintenance decisions. For this approach, an adequate quantity and quality of data is fundamental. Numerous studies deal with the analysis of time-based maintenance for production equipment. In fields of mechanized tunneling, unplanned machine downtimes restrict the applicability of time-based maintenance approaches. Thus, this paper mainly focuses on condition-based maintenance."

Jan 1, 2016

By Greg Hodges

Sand-and-gravel aggregates have become the number-one, nonmetallic-mineral resource in the world. Surficial aggregate deposits of economic size are becoming increasingly rare in most parts of Canada. In southern Saskatchewan, this is especially true, and detection and delineation of intertill sand-and-gravel deposits with airborne electromagnetic (EM) surveys have proven very successful. Airborne and ground geophysical surveys detect such deposits by their resistivity contrast relative to the surrounding clay-rich soils. Dighem helicopter-borne electromagnetic surveys map soil variations over a large area quickly and cost effectively, greatly reducing the cost of detecting and mapping deposits compared with traditional methods (air-photo interpretation, ground EM, and drilling.). The multiple-frequency EM system used by Dighem can map variations both horizontally and vertically. Magnetic data collected simultaneously are useful in mapping bedrock geology. Both resistivity and bedrock maps aid in the important task of reducing drilling costs and person-hours in the field. The results of the survey are presented as maps of ground resistivity, which are relatively easy to interpret. These maps are produced in the field at the time of the survey, making quick follow-up of the survey possible. Airborne EM surveys can map the extent and depth of aggregate deposits more effectively than is practical from the ground. Since aggregate deposits can vary tremendously in a very short distance (<300 m) large-area EM maps can show both local area variability and also help develop intertill trends. A test survey for the Saskatchewan Highways and Transportation Department over a 3-km by 5-km area mapped all the known deposits as well as some unknown deposits, subsequently proven by drilling. The test-survey data show that the method not only detected the deposits, but also gave an estimate of the shape (volume) of each of the deposits. Comparison of the data to drill sections shows excellent correlation. Theoretical modelling demonstrates that the multifrequency system can discriminate sand and gravel from bedrock ridges. Since the successful test work, about 725 km2 of ground have been surveyed, resulting in the discovery of four new deposits, which can be used immediately, resulting in significant savings for the Saskatchewan government and taxpayer.

Jan 1, 1999

By D. E. Martin, K. J. Hamill, H. J. Miller

1. INTRODUCTION In April 1979, the U. S. Nuclear Regulatory Commission issued the Draft Generic Environmental Impact Statement (GEIS) on Uranium Milling (NUREG-0511) for public comment. While the GEIS is a broad environmental impact assessment of the U.S. uranium milling industry as a whole, its primary focus is on the issue of uranium mill tailings disposal and long term isolation. In August of 1979, proposed regulations (U.S. Federal Register Notice 44FR50012), incorporating both conclusions of the GEIS and provisions of recent U.S. legislation on uranium mill tailings (Uranium Mill Tailings Radiation Control Act of 1978--UMTRCA), were also issued for public comment. This paper (1) briefly reviews the major conclusions of the draft GEIS, (2) summarizes the major elements and rationale of the associated, proposed regulations, and (3) reviews some of the major issues raised during the public comment period and changes which the NRC staff expects will be made in finalizing the GEIS and regulations. The risk in summarizing a document of such broad scope and complexity as the GEIS is that the depth of evaluation and the full technical bases for conclusions reached may not be adequately conveyed. Recognizing this, those Sections of the draft GEIS where a more complete discussion of the issues is presented are parenthetically noted in this paper in order to facilitate location of additional background and supporting material. 2. GENERAL CONCLUSIONS In the GEIS, a full range of tailings disposal alternatives was considered. These alternatives ranged from the past practice of doing little or nothing to control tailings, to advanced treatment alternatives such as nitric acid leaching to increase removal of radioactive elements and fixation of tailings in cement or asphalt. Our broad conclusions were: -Any alternative which results in the need for ongoing, active maintenance to assure long term containment, is unacceptable. (12.3.2.1) -Advanced treatment alternatives are unwarranted since they offer uncertain incremental benefits yet involve costs which may be as much as an order of magnitude greater than costs associated with acceptable alternatives. In addition, the advanced treatment

Jan 1, 1980

By Z. Kowalski

In the non-operational ?Górka? quarry, there are situated both a waste disposal site of an area of 6.7 ha, containing approximately 1 million ton wastes from high aluminium content materials (incl. about 400000 t of wastes from aluminum hydroxide production), and a pond of an area of roughly 3 ha, up to 15 m deep, with about 400000 m3 of polluted water and infiltrates from the disposal site mentioned. The basic problem related to the effluents in the Górka pond is both their high alkalinity (pH 12-13.4) and a variable analysis of pollutants whose level increases appreciably with the pond?s depth. The solution offered provides, first of all, remedial pumping and a treatment of effluents retained in the Górka reservoir. Effluents would be treated in a reverse osmosis plant according to a process verified so far on a quarter-commercial scale. The treatment process by-product, a brine solution (containing about 25% NaCl) whose amount may reach up to 100000 m3 might be supplied to the Debiensko Mine, which produces technological salt from salt-bearing mine waters. In parallel, an intake of underflows of infiltrates would be provided (previous geochemical identification) in order to take them away from the high aluminum site (by means of deep wells, and possibly girdling ditches). Such effluents would be subject to treatment. The successive stage is the utilization of approx. 50000 m3 of bottom slurry, left in the emptied reservoir, in the production of self-solidifying mixtures, which would be then used for sealing the bottom and the banks of the Górka reservoir. The empty and sealed reservoir would be filled up with a volume of approx. 600000 t of ashes, coming from coal burning in the thermal-electric power station. For the last stage, instead, is scheduled the rehabilitation of the entire waste disposal site in the Górka quarry. The site will be drained, covered with a leveling, sealing and rehabilitating layer, which will allow to introduce plants on the rehabilitated waste site. Later on, the area could be turned into a town park

Jan 1, 2006

By James R. Dunn

The nature of water and clay in carbonate rocks is currently being investigated at Rensselaer Polytechnic Institute by various thermal and sorption techniques. Two basic concepts &apos;led to the present research. (1) To explain the expansion and contraction on wetting and drying of some unsound argillaceous carbonate rocks, it was postulated that the pore space around each clay particle is such that when water is sorbed by the clay, force is exerted against the pore walls. (2) The clays in expansive rocks are rejected from the growing dolomite crystals during their growth, and form a more or less connected network, thereby becoming "wettable," or available to water. New quantitative cold differential-thermal-analysis (electrocalorimetric) equipment was designed and constructed to check the "limited space" and "wettable clay" concepts and to determine the thermal nature of the transition of water to ice in rocks. This DTA equipment can detect the release of heat in freezing of less than 0.001 per cent water in a rock. Twenty-three rock cores (nine sound and fourteen unsound) and 4 procelain cylinders for standards were studied. In the nine sound rocks and in all the procelain cylinders, the rapid freezing of from 50 to 100 per cent of the water was readily detectable after 7 to 10° C of supercooling. No further freezing could be detected to -20° C. However, in eleven of the fourteen unsound rocks, no freezing was detected to as low as -40° C; in the other three, less than 50 per cent of the water froze. As a check of the DTA measurements, adsorption isotherms were determined for all materials. Calculations of theoretical freezing points for sorbed water again demonstrated that the least sound rocks had the most nonfreezable water. "Frost" sensitivity in these carbonate rocks is, therefore, probably not the result of the force of expansion of water to ice. The disruptive force is believed to result from expansion of sorbed, ordered water on clay surfaces. The relationship between the unfilled rock pores after 24-hour water saturation and the water sorbed at 85 per cent humidity at 30° C (i.e., the theoretical nonfreezable water delineates the sound and unsound carbonate rocks.

Jan 1, 1966

By E. I. Jurgens, K. E. Hanney, D. C. Comrie, R. H. Fletcher

Introduction The reclamation of mine/mill tailings areas is undertaken for a variety of objectives including safety, appearance, economical use of lands and forests and long term storage of a future resource. The establishing of criteria for these objectives at any site is a shared task of the government and mining company. Our attention in this paper is directed to uranium mine/ mill tailings as they are handled in the Canadian industry and in the unique Canadian climate. We focus our attention on the state of the art. Uranium is a ubiquitous mineral forming an average of 4 g per tonne of the Earth&apos;s crust. Ores are mined at about 500 g per tonne so that the residual content of uranium in tailings is comparable to average background levels. However, as in most mine/mill operations, the ore contains other minerals that become readily mobile after milling operations. Thus the main objective of tailings impoundment is the stability both physically and chemically of the mobile materials. Since the requirements for the operation and construction of tailings areas in Canada have changed considerably over the past decade, there exists a great many mine/mill tailings areas which while considered adequate in their day, would not meet modern criteria. However, most of these installations pose no concern or hazard to the public. The proximity of mine/mill development to inhabited land areas has necessitated more stringent modes of tailings operations and provisions for tailings site reclamation. The more important of these have been: 1) the prevention of dyke failure, with large liquid-solid outflows onto adjoining lands, and 2) the prevention of seepage from the tails of pollutants such as chlorides, sulphides, heavy metals and radionuclides. Uranium mill tailings are discharged as a slurry from the concentrator after the removal of generally only about 1000 g, or less, per tonne of uranium from the as-mined ore. As a consequence, a great volume of low level activity waste is generated. The amount of tailings is expected to grow in quantity in the future even faster than the increase in yellowcake production, as the demand for energy

Jan 1, 1980

By Carlon C. Chambers

INTRODUCTION Manufacturer sponsored research over the past three years has proven the suitability of styrene-butadiene/ asphalt membranes in many waste disposal seepage control applications for the mining industry in general and uranium mining and milling in particular. The class of membranes that have been tested are SBR/asphalt blends containing up to 68 weight percent asphalt, the balance being elastomeric polymers, fillers and phase compatibility promoters. These membranes are classified as thermoplastic, elastomeric materials and can be hot spray applied to any moderately dry substrate at 177°C (350°F), and placed in service within one hour of application. The properties of this membrane that make it suitable for use as an engineering_ material in these applications are discussed. These properties include chemical resistance, bacterial resistance, UV light resistance, permeability, stress/strain characteristics and bonding data. The favorable economics of the system are also discussed. The preliminary raw test data on the above properties were reported in a previous paper, (Chambers, 1980) and most will not be repeated here. Instead, this report considers the original data in relation to subsequent data and concentrates on interpretation of the trends for engineering purposes. However, several of the pictures contained in the original paper are reproduced in this report for illustration purposes. BACKGROUND Asphalt alone has a long history of use as a water-stop material. Its limitations of becoming brittle when cold and soft when hot, however, are well recognized. The service temperature for common grades of asphalt is usually in the 4° to 49°C (40° to 120° F) range. Modifications to the base asphalt can generally improve its performance at the high end of the temperature range by raising its softening point, but only the addition of one class of modifiers, elastomeric polymers, improves low temperature flexibility as well and also adds resilience. Both of these properties are of extreme importance if the waterstop material is to maintain its integrity when used on substrates which are unstable, non-cohesive, discontinuous or have significant expansion/constraction coefficients. Although there are many elastomeric polymers which can be used with

Jan 1, 1980

By Richard B. Muter

In determining the layout or combination of unit operations to be utilized in a modem preparation plant, several factors must be taken into account. Among these are the washability data, size consist data, the particular market or markets for the coal, the mining method used, the degree to which the coal must be prepared, expected fluctuations in raw coal and markets, and the overall economics of the process. In addition, there are the health and safety aspects of coal utilization and preparation. Chapter 1 of this book discusses the characteristics of coal and coal markets, while Chapter 2 deals with the design of preparation plants. Once the unit operations for a particular plant have been decided upon, these arrangement may be depicted by using a flowsheet. A coal preparation plant flowsheet is a two-dimensional graphical representation of the sequence of operations, the arrangement of machinery, and the flow of materials for a particular coal cleaning operation. The flowsheet is usually qualitative in nature, becoming more quantitative as material balances, water balances, numbers and sizes of various pieces of equipment, etc. are added. The usual convention in preparing a flowsheet is to show the feed flowing from left to right, starting at the top left and working down as in an all-gravity process. Various symbols are used for each unit operation as depicted on a flowsheet, and Fig. 14-37 is a compilation of the commonly accepted international standard symbols for each unit operation. Fig. 14-38 through Fig. 14-40 are flowsheets of various coal cleaning processes as published in the January 1976 issue of Coal Age. Each process has its own unique features which, among others, depend upon the coal being cleaned, the coal market, and the mining operation. Fig. 14-38, for example, is a flow diagram for a jig plant preparing steam coal from two strip mines located a few miles apart. In addition to the jig washer, cyclones are used to treat the finer size coal. Fig. 14-39 is a flowsheet of a heavy media plant using a heavy media washer for + %-in. (+6.3-mm) coal, froth flotation for -28 Tyler mesh (-0.6 mm) material, and dewatering phase units (dwp) for Y, in. x 28 Tyler mesh (6.3 x 0.6-mm) cleaning of steam coal. In addition, thermal drying, centrifuge drying, and the use of vacuum disk filters and thickeners for dewatering are depicted. Fig. 14-40 is a flowsheet of a plant producing metallurgical coal. In addition to the heavy media and froth flotation circuits, a tabling circuit is also employed. These flowsheets are intended to give the reader an example of how the various unit operations for coal cleaning may be linked together. Figs. 14-41 and 14-42 illustrate the conversion of block diagrams into an IS0 prescribed set of symbols.

Jan 1, 1991

By G. Swartz, R. J. Brison, R. A. Wyman, J. P. Vandenhoeck, S. E. Khalafalla

Magnetic fluids are commonly composed of ultrafine submicron particles of magnetite (Fe3O4) dispersed in either a kerosene or a water carrier medium with oleic acid as a protective colloid. The unique property of these fluids is that when the magnetic particles are attracted to a magnet the carrier medium moves along with the particles so that the liquid also appears magnetic. The availability of a fluid whose gross behavior changes sharply in a magnetic field without affecting its rheologic characteristics is becoming critical for many technologic applications. About two gener¬ations ago suspensions of relatively large, micron-sized ferromagnetic particles in oil proved useful in clutches, brakes, and dashpots. These were called magnetic clutch materials, and their viscosities were highly dependent upon the applied magnetic field, in contrast to true mag¬netic fluids which retain their fluidic characteristics under all applied fields and field gradients. While the term "ferrofluid" was used by Rosensweig and Kaiser&apos; to designate a magnetic colloid composed of a dispersed magnetic ferrous material, the more general term, "mag¬netic fluid," is preferred. This is because these fluids may contain ferro- or ferrimagnetic substances, such as cobalt, nickel, gadolinium, dysprosium, or magnetic ferrites in carrier liquids, such as hydrocar¬bons (kerosene), silicones, water, fluorocarbons, etc. Preparation of Magnetic Fluids Magnetic fluids were first prepared by Papell and Faber, at the NASA Lewis Research Center, Cleveland, Ohio, by tumbling ferrite materials for several weeks in a carrier medium (such as kerosene) and a dispersing agent (such as oleic acid) with steel balls. Rosensweig et al.1 compared the stability of their ferrofluids obtained from both metallic iron and the magnetic oxides of iron, Fe3O4 and yFe2O3. They found that, although the saturation magnetization of iron is 3.5 times greater than that of magnetite, its colloidal solutions deterio¬rated much more rapidly. The iron particles were undoubtedly rapidly oxidized to a nonmagnetic state due to the enormous surface area of these colloidal particles. Because the properties of these fluids are highly dependent on particle size and may acquire opposite characteristics by small incre¬ments in that size, more controllable methods of preparation have been developed recently by Khalafalla and Reimers.6 In one method metastabilized pyrophoric wiistite is ground to colloidal size in a kerosene oleic acid mixture, and then it is disproportionated to colloi¬dal magnetite and iron at temperatures just below the eutectoidal temperature of wüstite stability (570°C); thus, t < 570°C 4 FeO t > 570°C Fe + Fe30, (1) Because of its antiferromagnetic characteristics, the precursor wüstite is much easier to grind than magnetite. Another method3 avoids grinding entirely and utilizes a peptiza¬tion technique from ferrous materials in the molecular state of aggrega¬tion. This latter procedure has resulted in preparation of strong fluids at considerable savings in cost.

Jan 1, 1985

By B. Pesic, J. E. Wey

Introduction One important class of manganiferrous ores is manganiferrous-silver ores. They occur in the oxidized portions of the silver deposits of the western United States. Silver is often associated with manganese oxides, which in some ore deposits are dispersed through calcite, causing the black color of the host rock, known as black calcite. Black calcites can occur in carbonate rocks (0.3 to 50 kg Ag/t) and in volcanic rocks (less than 30 g Ag/t). Silver mineralization associated with manganese oxides and black calcites can occur in veins (Hewett, 1968) or as disseminations (Graybeal, 1981). In the US, silver-bearing manganese veins are located in a broad arc that extends from southern Colorado to southwest New Mexico, southern Arizona, and southeast Califor¬nia (Hewett, 1964). Areas of disseminated silver-manganese mineralization include the Creede and Silver Cliff districts of Colorado and the Tombstone and Hardshell districts of Arizona (Graybeal, 1981). These deposits are also characterized by significant amounts of silver halides - cerargyrite (AgCl), bromargyrite (AgBr), and iodargyrite (AgI). Black calcites are also common in these deposits. Oxidized silver ores containing the higher oxides of manganese are generally refractory to hydrometallurgical methods of treatment. In the past when these ores could not be smelted, they were treated generally by cyanidation at very low efficiency. The US Bureau of Mines (USBM) studied the problem of treating silver-manganese ores in the early 1920s (Clevenger and Caron, 1925). It was found that the refractory silver in the original ore was insoluble in all the common solvents for metallic silver and its salts. The conclusion was that to obtain the highest recovery of silver, all the manganese had to be dissolved or the higher oxides of manganese reduced to manganous oxide. More recent results from treating refractory silver¬manganese ores were given by USBM (Scheiner et al., 1973). The silver ores from Candeleria District, NV, and Round Mountain District, CO, were investigated. Electrooxidation experiments recovered only 34% silver with minor amounts of manganese dissolved. Sulfurous acid pretreatment followed by cyanidation revealed that silver extracted was proportional to the amount of SO2 used. A similar approach, using sulfurous acid pretreatment followed by cyanidation, was also proposed by Rhoades et al. (1984). Hazen Research Inc. performed extensive testing on silver and manganese dissolutions from Ag-Mn ores obtained from the Candeleria and Round Mountain ore deposits. The methods examined were direct cyanidation, pretreatment with sulfurous acid followed by cyanidation, malonitrile leach, and leaching with ammonium hydroxide-sodium thiosulfate under slight oxygen pressure. The results were not satisfactory. The importance of the vast reserves of Ag-Mn ores and the lack of an efficient method to recover these metals warranted a search for new technologies. One novel method for extraction of these metals is treatment of Ag-Mn ores with acidified thiourea solutions. Preliminary results of the leaching of silver and manganese from Ag-Mn ores were very encouraging (Pesic, 1984a) ; thus, it was decided to examine the new lixiviant in more detail. Experimental Ore from the Round Mountain District was studied. It was crushed, ground, and dry sieved into monosized fractions in the range of 16 to +400 mesh. The ore composition was about 90 g Ag/t and 3% Mn, depending slightly on size. The leaching experiments were performed in apparatus described elsewhere (Pesic, 1982 and 1984b). All experiments were performed at constant temperature conditions. The leaching residues were analyzed for silver and manganese. Atomic adsorption was used to analyze the solution samples and fire assaying to analyze the leaching residues (for silver). The standard experimental conditions are given in

Jan 1, 1987

By Richard R. Klimpel

INTRODUCTION The process of froth flotation as a means of upgrading the quality of coal by removing water and/or ash and/or pyrite has been receiving increasing attention since the 1960&apos;s by the world-wide coal industry. Historically, coal preparation practice has involved the use of primarily gravity based separation techniques, screening, and/or water washing in removing the larger fragments of inert material from coarse raw feed coal. The preparation, handling, and cleaning of raw coal finer than 500 micrometers was deliberately avoided. Most often the fine coal that was produced would be judiciously incorporated into the bulk of the larger sized cleaned coal product or simply discarded. Since the 1960&apos;s and accelerating in the 19701s, the desirability of performing some type of coal cleaning or upgrading on the finer raw coal feed materials has been increasing. There are several apparent industrial incentives for implementing fine coal ((500 urn) processing alternatives including the gradually increasing value of the normally lost fine coal product; the additional amounts of fine coal being produced due to changes in mining techniques; the need to appropriately dewater and upgrade fine coal streams in order to meet increasingly stringent environmental regulations on water quality. storage of fines, etc.; the increasing need to lower undesired sulfur and ash contents in some coal end-use applications; and the increasing development of speciality coal use processes that require inherently finer and cleaner coal particles such as in gasification, liquefaction, fuel injection, etc. Looking at the over 70 years of mineral oriented fine particle separation successes at the industrial level, the use of froth flotation in fine coal would also seem to be a natural process to utilize at the industrial level. In the world of strictly mineral processing technology and, more importantly in the world of mineral commodity economics, there are clearly a number of advantages to using froth flotation that are well documented and universally accepted. These include: the relatively low capital and space requirements required when compared to other process options available to upgrade minerals; the extreme flexibility inherent to the froth flotation process both with regard to throughput and differences in raw feed characteristics; the general availability of a wide range of equipment sizes and reliable suppliers of equipment; and the general availability of appropriate and relatively cheap chemicals that are the major driving forces behind mineral flotation. Just how has the implementation of froth flotation fared in coal upgrading over the last 20 years? It is towards answering this question that this paper will be oriented. As such, the discussion will be somewhat philosophical. The comments offered are based on the personal experiences of this author who has worked in the basic side of inventing new flotation chemistry and flotation analysis techniques with the major overriding goal of implementing this new technology successfully at the industrial level in both coal and mineral flotation throughout much of the world. This paper is not intended to be a complete reference to all published scientific work on the subject of industrial froth flotation of coal. As a brief background to what will be expanded upon in this paper, the author would like to offer the following summary comments: 1) the industrial practice of fine coal froth flotation is qualitatively similar but quantitatively different than industrial mineral froth flotation when viewed from either research considerations, operating viewpoints or economic evaluation criteria; 2) it is clearly possible to invent and/or develop new technology (such as new chemistry and/or equipment) that can do statistically better than current plant practice in well-controlled tests in either coal or mineral flotation circuits; 3) there is so much inherent variability to the raw feed coal streams and other operating parameters that even if there is a documented technical incentive to implement some new piece of technology, the people, instrumentation and control methodology required are often simply not available or not economic unless the potential payoff is quite large.

Jan 1, 1988

By R. G. Benson, P. R. Wotruba, K. W. Schmidt

Introduction The Fortitude deposit is located in Nevada&apos;s Battle Mountain mining district in the central Great Basin region of the Basin and Range province of the western US. The deposit is at Copper Canyon in the southernmost portion of the district, about 19 km (12 miles) southwest of Battle Mountain (Fig. 1). Mining activity in the district began in 1866 (Roberts and Arnold, 1965). Base and precious metals were mined by underground methods intermittently until 1955. Placer gold was first discovered at Copper Canyon in 1912. Moderate scale dredging of alluvial gravel at the mouth of Copper Canyon was conducted by the Natomas Co. from 1944 to 1955 (Johnson, 1973). In 1967, Duval Corp. began large scale open-pit copper mining. (Sayers, Tippett, and Fields, 1968). Copper prices decreased and precious metals prices increased in the mid-1970s so Duval&apos;s exploration efforts at Copper Canyon shifted to precious metals. These exploration efforts resulted in the discovery of the Tomboy-Minnie deposits and shortly afterward, the Northeast Extension deposit at Copper Canyon (Blake, Wotruba, and Theodore, 1984; Fig. 2). The Fortitude deposit was discovered in late 1980, after Duval had proceeded with precious metals production at Copper Canyon. Converting the existing plant facilities at Copper Canyon to a precious metals recovery system was completed in 1978 (Jackson, 1982). Production from the Tomboy-Minnie deposits began in early 1979. Precious metals production moved to the Northeast Extension deposit in 1982. In late 1984, after three years of preproduction stripping and mining of the Upper Fortitude ore zone, production from the higher grade Lower Fortitude ore zone began. Currently, Battle Mountain Gold Co. operates the Fortitude deposit. Production from the Battle Mountain mining district before 1967 included 4.6 t (150,000 oz) of gold, 65.3 t (2.1 million oz) of silver, 13.6 kt (15,000 st) of copper, 4.5 kt (5,000 st) of lead, and 13.6 kt (15,000 st) of zinc (Roberts and Arnold, 1965). At the time of Duval&apos;s 1967 start-up, ore reserves at Copper Canyon included 12.6 Mt (14 million st) in the East ore body and another 3.6 Mt (4 million st) in the West ore body. Both had average grades of 0.79% copper, 16.1 g/t (0.47 oz per st) silver and 0.86 g/t (0.025 oz per st) gold (Blake et al., 1984). The Tomboy-Minnie deposits collectively contained 3.5 Mt (3.9 million st) of ore grading 3.09 g/t (0.09 oz per st) gold and 9.6 g/t (0.28 oz per st) silver. The Northeast Extension reserves were identified as 1.4 Mt (1.5 million st) of ore with an average grade of 2.9 g/t (0.085 oz per st) gold and 5.1 g/t (0.15 oz per st) silver. Initial total reserve estimates for the Fortitude deposit were 14.5 Mt (16 million st) grading 5.14 g/t (0.15 oz per st) gold and 29.8 g/t (0.87 oz per st) silver (Jackson, 1982). Therefore, before large scale mining, the Copper Canyon area contained a minimum of 102.6 t (3.3 million oz) of gold and 541 t (17.4 million oz) of silver as mineable reserves. The Fortitude deposit reserves as of Jan. 1, 1985 were 10.6 Mt (11 million st) grading at 5.28 g/t (0.154 oz per st) gold and 28.5 g/t (0.83 oz per st) silver. Currently, the company is producing 6.8 t (220,000 oz) of gold and significant amounts of

Jan 7, 1986

The 1996 Arizona Conference was held in Tucson on Dec. 8 and 9. Attendance was 648, a 12% increase from the 1995 conference. The annual conference is organized by the Arizona Conference Board of Directors, representing SME sections from throughout Arizona and adjacent areas. In addition to those representing mining and processing operations in the Arizona region, the meeting was well attended by interested parties from throughout North America. These included vendors, consultants, academia, research organizations and corporate management. The technical program highlighted the meeting. It consisted of a keynote address and morning and afternoon technical sessions. In the technical sessions, 23 papers were presented by the mining, hydrometallurgical, smelting, geology and mineral-processing divisions. The conference was then capped by a banquet that included a talk by a noted economist. Keynote address The program was kicked off by a keynote address titled "Forecasting for the 105th Congress," by Rep. John Shadegg (R-AZ). He was elected to Arizona&apos;s Fourth Congressional District in 1994. Shadegg serves on the House Budget Committee, the Resources Committee and the watchdog Government Reform Committee. He stressed the familiar conservative positions of reducing government spending, balancing the budget and states rights. As a member of the House Resources Committee, Shadegg stated his support for the mining industry. Technical sessions Mining division. Two of the five presentations described developments at two Arizona mining operations. T.J. Swendseid of Phelps Dodge presented a paper titled "New developments at Morenci" and P. Garretson of BHP presented a paper titled "Startup of the Robinson Project." Morenci continues to expand its operation and recently broke records for production. Other developments at Morenci included the completion of a 600-m (2,000-ft) drainage tunnel and stockpile rehandling. In addition, Phelps Dodge moved Morenci&apos;s crusher plant. It was completely disassembled and reassembled in just eight days. Another interesting presentation was "Predictive maintenance techniques for large electric shovels at Cyprus Sierrita," presented by T. Ritzel of Cyprus Amax. The presentation described high-technology methods for predicting maintenance problems. These methods included vibration analysis, ultrasonic detection, infrared thermography, electrical measurements and tribology (the science of lubricant evaluation). The benefits of these techniques are reduced downtime of the equipment, as was demonstrated in case studies at the mine. The other presentations were "Introduction to NOSA 5-star safety program," by R. McKinnon, BHP Copper North America, and "A new design guideline for mine sealing," by K. Fuenkajorn, Rock Engineering International. Hydrometallurgical division. The hydrometallurgical session consisted of five papers. These included a presentation titled "Recovery of gold and silver using guanidine-based extractants," by M. Vining of Henkel Corp., Tucson, AZ. In this presentation, guanidine-based extractants LIX-79 and AURIX resin were introduced. LIX-79 was shown to have applications in copper-gold and high silver ores. In ammonia-cyanide leaching, AURIX was shown to be more selective in CIL vs. RIL comparisons. Other papers in the hydrometallurgical division included "Application of cobalt in the copper industry," by J. Hawke, OMG Apex Inc.; "Series parallel conversions and production gains at Cyprus Miami Mining&apos;s dump leach and solvent extraction operation," by E. Bilson of Cyprus Amax; "Lead alloy anode corrosion at the San Manuel SXEW tankhouse," by W .M. Gort of BHP Copper and "Hydrometallurgical treatment of copper refinery slimes," by B.C. Wesstrom of Phelps Dodge. Smelting division. Three papers were presented in the smelting division session. These included updates and reports on improvements at the Hayden, Hidalgo and BHP San Manuel smelters. For example, W.A. Dutton of Phelps Dodge presented "Recent improvements at the Hidalgo Smelter." These changes were aimed at reducing environmental emissions and increasing production. They included modifications to the fugitive-gas collection system to reduce particulate emissions, rubber lining the acid plant scrubbers to reduce corrosion and the installation of a cold lime softening system for water treatment. Equally interesting papers were presented by D. Norton of Asarco, Hayden, AZ, in a paper titled "Update of the Hayden smelter process," and by D. Jones of BHP Copper, San Manuel, AZ, in a paper titled "Update on first campaign of the BHP San Manuel Copper." Geology division. The session began with a paper that outlined the progress of an exploration project in South America. "The Pierina exploration project, Ancash Province, Peru" was presented by J.D. Lowell, Lowell Mineral Exploration, Rio Rico, AZ. Another paper was then presented on a copper deposit in Grant County, New Mexico. "Zonation of supergene copper minerals at Hanover Mountain, Grant

Jan 1, 1997

By John D. Abbatt, H. B. Newcombe

The Eldorado Epidemiology Project formally began in late 1978. It consists of a retrospective cohort study, to be followed by and to leave in place the mechanism for a prospective cohort monitoring program. These present and future activities are intended to merge into one another. The current study includes all Eldorado employees past and present for whom records are available. The objectives of the undertaking are - 1) to obtain cause-and-effect, dose-response data with which to evaluate the risks to workers in radon and radon daughter containing atmospheres, and to provide additional quantitative information on which to base possible improvements in working conditions; 2) to identify any dead employees of E.N.L. whose cause of death suggests that a potential compensation claim right exists for their survivors, and to similarly identify living ex-employees of E.N.L. whose work histories and states of health suggest potential compensation claim rights. The nature of the study has been determined by the history of Eldorado, which will be described briefly. Eldorado began (as Eldorado Gold Mines) in the late 1920&apos;s, operating relatively unsuccessfully in Manitoba. In 1930-31 the emphasis shifted from gold to uranium, and what became the Port Radium mine was first staked. From the very early 1930&apos;s until 1942 the company&apos;s purpose was almost entirely devoted to the mining of pitchblende - uranium ore - from the Port Radium site, and the extraction of radium from this ore at the Port Hope refinery in Ontario, a process from which the uranium was a largely stockpiled byproduct. In 1942 the company was requested by the Canadian government to accelerate the production of ore, and of uranium. At the same time, all its stockpile of uranium (then being stored in silos as a "waste" product which might later "come in") was acquired for the Manhattan Project. In 1944 the company shares were bought by the Canadian government and the company itself became Eldorado Mining and Refining (1944) Limited; it has operated as a Crown corporation ever since. The name was changed to Eldorado Nuclear Limited in 1968. The Port Radium mine was closed in 1960, and since 1953 the Beaverlodge uranium mine complex has operated on the northern shores of Lake Athabasca. Radium production was discontinued in 1954 when the radium circuit was taken out of the refinery, and since that time the refinery&apos;s products have been various types of refined uranium (uranium dioxide, uranium trioxide and uranium hexafluoride) plus metallic uranium. The refinery, of course, processes the company&apos;s own yellowcake but as it is one of only five refineries in the western world, most of its work consists of custom refining for a large variety of customers. In addition to the mining and the refining operations, there have been three other divisions involved, and these are, respectively, Aviation, R. & D., and Exploration, in addition to the financial, corporate, administrative and support activities. MATERIAL AND METHODS The human study population (Abbatt, J.D. et al., 1980) consists of all Eldorado employees who have ever worked for E.N.L. and for whom records are available. The total nominal roll to December 31, 1980 is approximately 21,000 and consists of employees of the Mining, Refining, R. & D., Aviation and Exploration Divisions, as well as a relatively small number of other employees (Head Office, etc.). The basic epidemiologic design, as has been mentioned, is for a retrospective cohort study merging into a prospective cohort study, and depending very heavily upon automated record linkage and file matching. The original design called for an initial assembly of the bulk of the nominal roll, prior to the first of two matches with the National Mortality File. The first of these two matches is now complete and the second is to be separated from it in time by 18 months to two years. The second match will be the definitive match prior to the analysis, the interpretation of the data, and the publication of the results. The period between the two matches was designed to permit completion of the nominal roll, including: - addition of previously missing individuals and groups, elimination of duplicates, and amplification of identifying information, - assembly of work histories and exposure information for each individual, - digestion and application of lessons and modifications resulting from the first match with the National Mortality File at Statistics Canada, - preparation of files for the definitive second match. The analysis of data will be carried out by the National Cancer Institute of Canada Epidemiology Unit based at the University of Toronto. This group, with whom Eldorado Nuclear has a memorandum of understanding, have for a variety of reasons, including their familiarity with record linkage and their expertise, been members of the Project Team since

Jan 1, 1981

By Bernard L. Cohen

I.INTRODUCTION The B E I R-III Report (NAS-1980) introduces large increases in the estimated health effects of radon as compared with previous work (NAS-1972). It is the purpose of this paper to point out some important failures of these new BEIR-III estimates, to offer a general critique of the procedures used in obtaining them, and to offer more rational estimates. In Sec. II we use the BEIR-III model to calculate the risk to non-smokers from environmental radon, and show that it predicts more than twice the total lung cancer rate actually experienced by nonsmokers. In Sec. III we review the histological evidence which shows that no more than about 10% of the lung cancers among non-smokers can be due to radiation. In Sec. IV, we discuss alternative causes of lung cancer, which further reduces the fraction that can be caused by radiation, and in Sec. V we summarize and conclude that the BEIR-III model over-estimates the lung cancer rate in nonsmokers due to environmental radon by at least a factor of 40. In Sec. VT we review the evidence on risk of radon exposure to smokers, and conclude that it is probably not more than four times the risk to non-smokers; this means that the BEIR-III model over-estimates the risk of low level radon exposure to smokers by at least a factor of 10. In Sec. VII, we consider the reasons for the large over-estimates in the BEIR-III. Report. II. BEIR-III LUNG CANCER RATES DUE TO ENVIRONMENTAL RADON AND COMPARISON WITH TOTAL LUNG CANCER RATES AMONG NON-SMOKERS The BEIR-III Report gives the following estimates of the lung cancer risk from low-level radon exposure in terms of working-level-months (WLM): age 35-49, risk = 10 x 10-6 /yr-WLM 50-64, 20 >65, 50 where ages refer to age at death. For latent periods between exposure and onset of these risks it gives age 0-14, latent period = 25 years 15-34, 15-20 years (we use 17 yr) >35, 10 years where ages refer to age at exposure. This is a clear and unambiguous model which is readily usable for deriving numerical estimates. We begin by using it to calculate lung cancer rates due to environmental radon. *This is an abridged version of a paper scheduled to appear shortly in Health Physics. The first step in this process is to estimate the environmental exposures; this was done in a recent paper (Cohen-1981) which concluded that these are about 0.22 WLM/year. In Table 1, this is used to calculate the BEIR-111 predictions for radoninduced lung cancer rates in the U.S. (Col. (5)), and by combining these with population statistics, it is shown (Col.(7)), that it predicts about 24,500 fatalities per year, almost one-third of all U.S. lung cancers. The comparison between the age-specific expected rates from Col. (5) of Table 1 and observed rates among non-smokers is shown in Table 2. The recent paper by Garfinkel (1980) presents the results of a 12 year follow-up on one million Americans in a study by the American Cancer Society. The paper by Hammond (1966) gave the results of the first four years of that study. The paper by Kahn (1966) is based on the so-called "Dorn Study" of 293,000 U.S. veterans of World War II who carry government health insurance. It represents 8 and 1/2 years of follow-up. A recent update on that study (Rogot-1980) does not give absolute lung cancer rates, but the age-standardized ratio between smokers and non-smokers has remained the same which indicates that there has probably not been an important change in the rates for either. The paper by Hammond and Horn (Ha-1958) was an early study by American Cancer Society. It is immediately evident from Table 2 that the BEIR-III estimates for lung cancer induced by environmental radon exceed the [total] lung cancer rates due to [all] causes among non-smokers by about a factor of two at every age. It is only fair to point out that this does not represent a direct discrepancy with the BEIR-III Report since the latter states that its estimates for non-smokers may be too high by a factor ranging from 1 to 6, favoring a factor intermediate between these. Comparisons can also be made with total lung cancer incidence for all ages. A paper by Hammond and Seidman (Hammond-1980) gives the rate for ages above 40 to be 177 x 10-6/year for men and 124 x 10-6/year for women, whereas the rate calculated in Table 1 from BEIR-III for ages above 40 is 309 x 10-6, a factor of two higher. For all ages, the rate among women was reported as 36 x 10-6/year (Hammond 1958) as compared with 114 x 10-6/year calculated from BEIR-III in Table 1, a discrepancy of well over a factor of two. All of the data we have presented are basically from three study groups, but in all three cases the BEIR-III estimates for lung cancer induced [by environmental radon alone] are a factor of two higher than actual [tota] lung cancer rates among non-smokers. Another approach to comparing the BEIR-III pre-

Jan 1, 1981

By Erik Westman, BEN WESTON, SETAREH GHAYCHI AFROUZ, KATHRYN DEHN

One of the most difficult challenges in underground mining is to forecast significant seismic events prior to their occurrence in order to support the safety of miners and to minimize damage to the underground operation. Passive seismic tomography is a tool to image the seismic velocity changes in a rockmass, which can potentially reveal the rockmass behavior before and after a significant seismic event. In this paper, the changes in seismic velocity of the rockmass before and after three major seismic events are investigated to determine whether there are identifiable precursory velocity changes associated with the major seismic events. Conventional mechanics imply that the induced stress at the hypocenter would continue increasing until failure, in the form of an induced seismic event, occurs. With passive seismic tomography we can image changes to the seismic wave velocity distribution within a rockmass and hence infer the changes to the induced stress near the hypocenter. This paper evaluates the hypothesis that induced stress at the hypocenter (as inferred by the p-wave velocity) increases until the seismic event occurs. In addition to analyzing p-wave velocity changes near the hypocenter, changes to the p-wave velocity at “zone centers” were also analyzed. These “zone centers” are regions within the rockmass that consistently have a p-wave velocity that is much higher than the average p-wave velocity for the rockmass. It is found that the p-wave velocity did not increase at any of the three hypocenters prior to the seismic event occurring, however the p-wave velocity did increase in the closest “zone center” for two of the three events.

Oct 12, 2020

By Elham Najafi, Sina Ghassa, Ata Akcil, Hadi Abdollahi, Sandeep Panda, Zohreh Boroumand

The present study investigates the influence of ferrous iron (as FeSO4) and ferric iron (as Fe2 (SO4)3), and pyrite (FeS2) on the ability of bacterial leaching of a high-grade sulfide Zn–Pb ore. In this regard, shake flask experiments were carried out at 5% (w/v) pulp density of the ore sample (having 40.7% Zn and 12.4% Pb initial metal content) using a consortium of mesophilic iron and sulfur-oxidizing acidophiles. A concentration of 0.04 mol/L of ferric iron in the leaching media was found to be optimum for zinc extraction without affecting growth of the microorganisms. Under this concentration, the dissolution of Zn, Pb, Cd, and As was found to be 57%, 0.2%, 0.03%, and 9.9% in 25 days. Using ferrous iron in the media, 0.16 mol/L of Fe2+ was found to be the optimum concentration for efficient bacterial growth and metal dissolution (54.6% Zn, 0.08% Pb, 0.03% Cd, and 10.2% As) from the sample in 25 days. On the other hand, using pyrite as the source of energy for bacterial growth, an initial 12-day lag period was observed when compared to the effect of ferrous iron in the media. Under the optimum concentration (test with 0.24 mol/L iron in the form of pyrite), the dissolution of Zn, Pb, Cd, and As was found to be 39.8%, 0.1%, 0.03%, and 10% in 25 days. The surface chemistry analysis indicated formation of a sulfur layer over the particle surface that hindered reagent diffusion and affected metal recovery through bioleaching.

By John Marsden, Mike Botz

A variety of modeling techniques can be utilized to forecast metal production at heap leaching operations. These approaches reflect a wide range of complexity, flexibility, time to implement, cost, and accuracy. For many operators, a spreadsheet-based modeling technique is attractive since the calculations are directly accessible, models can often be developed by site staff, and the results are generally easy to extract and interpret. The authors have developed a spreadsheet-based modeling technique that provides a high degree of flexibility, while still considering detailed operating information for ore properties, leach kinetics, scaleup factors, lift height, and in-heap metal inventories. The technique involves establishing kinetic leach curves for each ore type to characterize metal extractions, followed by application of separate metal recovery curves to define the rate at which leached metals exit the heap in pregnant solution, taking into account delays due to the in-heap solution inventory. At any point in time, the difference between total metal extracted and total metal recovered is equal to the in-heap inventory of the leached metal. This modeling technique is particularly useful for larger multi-lift heaps where delays in metal recovery are appreciable due to in-heap solution holdup. The technique is also applicable to sites with multiple heaps, leach cycles, and/or metal recovery plants (e.g., carbon columns for gold; solvent extraction for copper). This paper describes the modeling technique, including input data required and methods for defining kinetic leach curves and metal recovery curves. The technique is compared against an alternative spreadsheet technique using a simplified in-heap solution inventory calculation to forecast metal production, which has proven to be effective at a number of sites.

By Taghi Sherizadeh, Kutay E. Karadeniz, Dogukan Guner, Samuel Nowak

Despite numerous empirical, numerical, and hybrid studies conducted on the subject of coal rib failure, mine fatalities related to rib failures continue to occur. To date, a standard methodology for the design of coal rib supports which can accommodate the wide range of unique conditions found in coal mines in the United States has not been developed, forcing mine operators to rely on the trial-and-error process or industrial legacy practices for the design of coal rib support patterns. In this study, to better understand the support systems' effectiveness, various rib bolting scenarios were investigated. A coal mass constitutive model is implemented to a Distinct Element Method (DEM) code, and rib factor-of-safety (RibFOS) analyses were performed by applying strength-reduction for the coal matrix and explicitly modeled face cleats. Ribs with various overburden depths and mining heights composed of solid Banded-Bright coal (BBC) were considered in this study. Different scenarios such as rib bolt length and the number of bolts were studied to quantify the effect of primary rib support density on rib stability. As a result of the unsupported coal rib analyses, a decaying exponential relationship is proposed between the mining height-overburden depth and the RibFOS. The developed coal rib models clearly show the coal-rib bolt interaction and illustrate how the addition of rib bolts restricts the movement of the coal rib. The results reveal that the strength reduction method in DEM code with the coal-mass model can aid in the development of practical primary support charts, which can help in the rib support design process. In addition, an unsupported RibFOS cutoff