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By K. Huang, L. Pan

"Darcy’s law has been used extensively to model cake filtration. It is a macroscopic model, in which particle size dominates the kinetics and cake moisture. In the present work, a capillary flow model has been developed from first principles to study the effects of microscopic parameters such as capillary radius, boundary layer slip, disjoining pressure, and surface tension that may be important for dewatering ultrafine particles. Laboratory-scale pressure filtration tests show that dewatering kinetics is strongly dependent on capillary radius, which in turn is influenced by surface hydrophobicity, surface charge, and length scales of particles. The model parameters determined from laboratory-scale filtration tests show that use of a hydrophobizing reagent can greatly improve fine particle filtration due to increased slip and decreased capillary pressure. The kinetics of dewatering kaolin clay is fastest at a pH where the layer-structured particles coagulate with a face-to-edge orientation. The capillary flow model developed in the present work may be useful for designing filters and optimizing operating conditions.INTRODUCTIONIn 2014, Canada produced 2.2 million barrels per day of crude oil from the oil sands resources in Alberta, which is expected to grow to 3.2–4.0 million barrels per day by 2030 (CAPP, 2013). One of the challenges to meeting these projections is the tailings management. At present, the industry uses ?77 km2 of the lands to construct tailings ponds. Significant amounts of the tailings disposed to the ponds are silts and clays that are slow to settle and consolidate, creating problems for reclamation. It is, therefore, the objective of the present work to develop a filtration model that may be useful for developing advanced dewatering technologies that can address the tailings management issues.Darcy’s equation is the governing law for filtration. It was derived as an empirical model by H. Darcy in 1856 while he was studying fluid flow in sand filters (Hall, 1956). Since then, many investigators derived it from first principles. It relates superficial fluid velocity to the pressure drop across a porous medium of known permeability. In filtration, the latter can be related empirically to particle size using the Kozney equation (Yoon, 2005)."

Jan 1, 2016

By Reinhard Gertl, Maximilian Weithaler, Harald Kammerer, Juan Pablo Muñoz, Juan-Carlos Rueda

The Guillermo Gaviria Echeverri tunnel and its access roads project in Antioquia, Colombia is a mega infrastructure project that includes a road network with the longest tunnel in Latin America and several short tunnels, the latter being the focus of this study. The design of the project required careful consideration of several special factors, such as the tunnels’ steep slopes of up to 5%, high fire load of 100 MW, bidirectional operation, and short lengths that make it difficult to place ventilation equipment. The combination of all these parameters cause a challenging design problem for the ventilation systems and smoke control of the short tunnels. To address this challenge, a risk assessment study was conducted to support the design of a new and innovative ventilation strategy that deviates from relevant guidelines and standards, like the Austrian RVS [1][5][6] or the German EABT [8] in order to provide a customized solution for this particular project. This strategy resulted a cost-effective solution, that allowed a reduction in the number of required jet fans and at the same time reaches or reduces the risk level compared to traditional ventilation strategies.

Jun 13, 2023

By Thomas V. Durkin

About 1.41 kt (45.2 million oz) of gold have been ! produced in South Dakota since 1875. South Dakota's mining laws attempt to strike a balance between economic development and environmental protection. Mining is promoted as an industry while prevention of pollution is required along with reclamation of affected lands to a beneficial use. The South Dakota Department of Environment and Natural Resources' (DENR) system of "one-stop shop- ping" for environmental permits streamlines the permit process. It fosters quick resolutions to compliance problems and helps keep enforcement actions out of the courts. Paha Sapa means "Hills that are Black" in Dakota Sioux. Appearing dark from a distance due to a thick forest of Ponderosa pine, the Black Hills were gold to many people. The exact date that gold was discovered in the Black Hills remains debatable. An inscribed stone tablet found in 1887 near Spearfish recorded these words:

Jan 1, 1998

By Fathi Habashi

The year 1987 marked the centennial of the beginning of modern hydrometallurgy. On October 19, 1887 British Patent No. 14174 entitled Process of Obtaining Gold and Silver from Ores was issued*. The discovery was made by John Steward MacArthur (Fig. 1), a chemist-metallurgist, supported and assisted by Robert and William Forrest, two brothers practicing medicine in Glasgow. The discovery was made in the basement of their clinic. The process, which became known as the cyanidation process in reference to the alkali cyanide reagent used, immediately received industrial success in New Zealand in 1889 and in South Africa in 1890t. It displaced the chlorination method which had been in use. In 1903 MacArthur was awarded the first Medal of the Institution of Mining and Metallurgy in London1131 - The cyanidation process was responsible for the doubling of gold production in the world in the two decades which followed its first application (Fig. 2). To the modern metallurgist, it may be surprising to think of MacArthur coming across an obscure reagent such as an alkali cyanide as a leaching agent for gold ores. It is the purpose of this paper to discuss the background and the factors that led to this invention, the development of the understanding of the process, and the application of modern technology.

Jan 1, 1999

By S. K. Kawatra

A growing concern for pyrometallurgical operations is the generation of airborne particulates. These particulates can be generated by combustion processes, or by materials handling. Regulation of these particles by the EPA has become progressively more stringent, first for particulates finer than 10 micrometers (PM10), which are particles fine enough to be inhaled into the lungs. Then, restrictions were introduced on emissions of particles finer than 2.5 micrometers (PM2.5), which are fine enough to become embedded in lung tissues. The next stage of regulations is likely to be ?nanoparticulates,? particles finer than 100 nanometers, which are in a size range where their very high surface area leads to enhanced reactivity. While all of the health effects due to nanoparticulates have not yet been determined, there have been enough studies to indicate that there is a problem, and restrictions on nanoparticulate emissions are only a matter of time. In this paper, it will be demonstrated that dry handling, comminution, and combustion sources represent a significant concern for both PM and nanoparticulate emissions. In regards to dry handling, the effects of utilizing effective dust suppressants on PM and nanoparticulate emissions will be explored.

Jan 1, 2006

By Matthew Blecha

The Tribag copper deposit is one of the rare examples of mineralized breccias in the Canadian Shield. The breccia is a pipe-like body, and consists of granitic, diabasic and volcanic fragments embedded in a vuggy, quartz-carbonate matrix. The mineralization is essentially chalcopyrite and pyrite, with minor molybdenite, sphalerite, galena and other sulphides. The main ore zone is saddle-like in shape, and is enveloped in a zone of chloritization, sericitization and clay-mineral alteration. It is suggested that the breccia is of the diatreme type. Introduction T HIS paper is based on eighteen months of field work, including surface and underground geological mapping and core logging, and on the survey of relevant literature. No significant amount of laboratory work has been done as yet. Location and Access The Tribag Batchawana property is located 40 miles north of Sault Ste. Marie, Ontario, about 10 miles east of Lake Superior. A 17-mile, all-weather road connects the property to the Trans-Canada highway to the south, and 4 miles of a 12-mile road remain to be completed to link it to the Algoma Central Railway to the northeast.

Jan 1, 1965

By Manjeet Chowdhry, Qingxia Liu, Phillip Choi, Zhenghe Xu

Computational chemistry methods, such as density functional theory (DFT), are powerful tools to quantify reagent-mineral interactions encountered in sulphide mineral flotation. A quantitative relationship between theoretically calculated parameters based on chemical structure of collectors and their reactivity with different metals/minerals can provide valuable insights for design and development of more powerful and tailor-made reagents offering enhanced metal/mineral selectivity. DFT calculations at B3LYP/6-311++G(3df,3pd) level were employed to elucidate the reactivity of neutral sulphide collector reagents, including thionocarbamates (TC), thioureas (TU), xanthogen-formates (XF), dialkyldithiocarbamates (DTC) and dialkyltrithiocarbonates (TTC) with different heavy metal ions (Cu2+, Zn2+ and Pb2+) in solution. The extent of delocalization of lone pair electrons of heteroatoms (attached directly to C in C=S) over C=S group was found to be the dominant factor in determining the collector’s reactivity. Order of reactivity was established as: TU > TC > XF > DTC > TTC. All the collectors showed superior affinity towards copper followed by lead. Unidentate binding was observed through sulphur atom except for xanthogen-formate for which bidentate binding mode was observed. Effect of nature of substituent groups at N and/or O atom on reactivity of thionocarbamate and thiourea was also investigated. The results obtained through DFT calculations are consistent with the experimental data reported in literature.

Jan 1, 2015

By M. W. BERNEWITZ

AUSTRALIANS and New Zealanders, whose countries have respectively yielded gold to the value of £666,000,000 and £96,000,000, are taking full advantage of the current high prices for that metal. There is a marked activity in ordinary prospecting, geophysical exploration, further development of working mines and reopening of old properties, formation of new companies, installation of new equipment and processes, and expansion of operations generally. Australian gold production last year was approximately double the quantity of 1929 and its value three times as great, 1929 being the low of recent years. The 1933 production was about 821,000 oz. From New Zealand, 165,000 oz. was exported last year. Papua and New Guinea contributed slightly over 100,000 oz. What the future price of gold will be nobody knows, but, even if it returns to the former level, Australian producers are almost sure of 110 shillings an ounce until 1940 through the Commonwealth Government's Gold Bounty Act, at present temporarily and necessarily suspended from operation.

Jan 1, 1934

By Li Fangi

This paper describes the characteristics and regularities of a process to recover rare earth minerals from Baotou Ore with H-205 collector. H-205 is a kind of hydroxamic acid with amide as a polar group and poly-cycle aromatic hydrocarbon as a non-polar group, having strong ability to capture RE minerals (bastnasite, monazite). When adding a certain dosage of water glass and some other modifying agents, and maintaining pH value between 8.5 and 9.5, RE minerals can be effectively separated from calcium and barium minerals, such as fluorite and barite, etc. Under normal flotation temperature and concentration, when using H-205 to float RE minerals, it needs a bit longer conditioning time (a few minutes longer than that for the conventional collectors). It is also shown that the reagent has the property of resistance to hard water. The laboratory scale and pilot scale tests of the process have been carried out on bulk froth containing RE minerals and fluorite taken from Ore Dressing Plant of Baotou Iron and Steel Company, in both cases, high grade RE concentrates were obtained and the recovery increased remarkably. Therefore, the process has a great practical value.

Jan 1, 1989

By A. W. Adamson

A model for transport processes in liquid mixtures is discussed which supposes that the elementary act involves a position exchange between two species and that the exchange is so confined by the solvent cage as to occur nearly isosterically. The rate-determining step, thus, is likened to a bi-molecular reaction and is so treated, using absolute rate theory. The cage model has been applied to diffusion, thermal diffusion, sedimentation and viscosity, but only the first and last of these phenomena are emphasized in the present paper. The model leads to semi-empirical relationships between the absolute value for a digusion coefficient and the activation energy for diffusion, between mutual and self-diffusion coefficients and for the variation of the viscosity of a binary mixture with composition. These are discussed in relation to experimental data for various systems, including hydrocarbon mixtures. It is shown that the proposed viscosity equation and seven other commonly used ones all may be regarded as special cases of a single general relationship; a brief critical analysis is made of the basis of selection of one or the other for data fitting or interpolation. INTRODUCTION AND GENERAL THEORY The present paper covers a brief discussion of a cage model for transport processes in liquid mixtures and how this model may be useful in treating the diffusional behavior and the viscosity of such systems. Since diffusion requires the more detailed treatment, it will be taken up first, and the model then applied to viscosity. There are two types of diffusion coefficients that may be measured experimentally, apart from thermal diffusion quantities. The first is the mutual or binary diffusion coefficient, D which may be defined in terms of Fick's first law. This states that the permeation, or flux P, is proportional to the concentration gradient. In the usual experiment, P is measured relative to a frame of reference fixed with respect to the medium (e.g., the diaphragm in a diffusion cell); as a consequence, the same value of D is obtained regardless of whether P and C refer to Component 1 or to Component 2; i.e., there is only one independent mutual diffusion coefficient for a binary system. In addition to D there will be various self-diffusion coefficients. defined in terms of the gradient in labelled species i and its permeation in an otherwise uniform medium. The thermodynamic approach to mutual diffusion supposes that the actual driving force is the gradient of the chemical potential, i.e., that In the case of a dilute solution of solute, Eqs. 1 and 3 lead to the Einstein equation, If the solution is ideal and the friction coefficient is taken to be then the familiar Stokes- Einstein equation results. Mutual and self-diffusion coefficients can not be related on general thermodynamic grounds; it is necessary to invoke some additional assumptions, i.e., a model; several such have been proposed. Hartley and Crank' supposed the existence of separate, intrinsic diffusion coefficients (Dl and D2) for each component, essentially corresponding to the two self-diffusion coefficients. The two flows can not be independent, however, but must be coupled through the usual restriction that there be no net volume flow. For an ideal solution. one then obtains' Glasstone, et al' treated diffusion in terms of absolute rate theory, but their approach otherwise resembled the previously mentioned one in that each species was considered to move with respect to the general medium in a manner determined by its individual jump distance and specific rate constant. For other than dilute solutions, a coupling of flows leading to an equation such as Eq. 6 would again be present. However, as required by Eq. 6, one does expect that the self-diffusion coefficient for the solute and the mutual-diffusion coefficient for the system become identical at infinite dilution. Lamm4 recognized that there should be three distinctive interactions in a two-component system-1-1, 1-2 and 2-2 — and, therefore, proposed three rather than two fundamental friction coefficients. Mutual diffusion resulted from 1-2 interactions only, and self-diffusion resulted from 1-2 plus either 1-1 or 2-2 interactions. Again, a collective coupling between all motions was imposed to meet the condition of no net volume flow. Laity' has shown how to convert the Onsager equations to a form very similar to Lamm's. Cage Model For Diffusion Work in this laboratory on diffusion in aqueous sucrose solutions made it apparent that three, rather than two, interactions were indeed needed," but considera-

By B. Chalmers

THE practical importance of the phenomena of melting and freezing must have been recognized for a very long time. The difference between ice and water, for example, has had a profound influence on the history of mankind and the evolution of society. The possibility of melting a metal and allowing it to freeze in a mold of chosen shape has been an essential ingredient in our mastery of the art of shaping metals, and therefore in the evolution of the: machine age in which we find ourselves. The importance of melting and freezing, as applied to metals and alloys, has been so great, in fact, that empirical solutions have been found for the multitude of practical problems that have arisen. This approach has been so successful that relatively little attention has been directed to arriving at an understanding of the fundamentals of the processes. But metallurgy has come to a stage at which we may expect that some, at least, of the more complex problems that have not yet been solved (or perhaps even recognized) may be handled more effectively by scientific study, theoretical understanding, and logical experimentation than by trial and error. In this lecture, therefore, I propose to describe in outline what I think really happens when a metal freezes. In doing so I hope to explain many of the phenomena which have been observed, and in particular to account for the structures that are obtained in actual ingots and castings. The basic problem, to which this lecture represents a tentative partial answer, is this: a mass of metal, containing known proportions of various elements, is melted, heated to a given temperature, and then allowed to freeze under specified conditions. What will be the "structure" of the resulting metal? The term structure includes: 1—crystal size, shape, and orientations, 2—distribution of chemical elements, and 3-—shape, including cracks, cavities, pores, etc. The Solid-Liquid Interface We will first consider what takes place if a single crystal of a metal in the form of a rod is heated, not uniformly, but so that one end is hotter than the other. If this heating process is continued long enough, the hotter end will eventually melt; we will suppose that the rod is in a containing vessel so that the molten metal does not run away, Fig. 1. When some of the metal has melted, we have some solid, some liquid, and an interface or surface of contact between them. If the source of heat is now removed, the interface will move so that some of the liquid freezes, and if the supply of heat is suitably adjusted the interface will remain at rest. This very simple arrangement allows us to study the basic processes of melting and freezing, and if we fully understand this simple case, we may be able to account for what takes place under practical conditions where the heat does not all flow in the same direction, and where the heat flow is determined not by a controllable source of heat but by the heat capacity and temperature of metal and mold, and by the heat loss from the mold surface. The solid-liquid interface is evidently the region of the greatest interest to us; on one side of it there is crystalline solid, and on the other, liquid. In the solid, each atom has a well defined position, around which it vibrates as a result of thermal agitation. It only leaves this position in the relatively rare event of a "diffusion jump." The liquid is much less systematically organized. The atoms are about as far from their neighbors as in the solid, but the arrangement is much less systematic and is continuously changing. The solid and the liquid are represented diagrammatically in Fig. 2. The average energy of the atoms in the liquid is greater than in the solid by an amount that corresponds to the latent heat of fusion, i.e., the amount of heat that has to be supplied to convert unit mass of solid into liquid at the same temperature. The Two Processes As has recently been shown by Jackson and Chalmers,3 many of the features of the processes of freezing and melting can be understood if it is assumed that a continuous and rapid interchange of atoms between solid and liquid always takes place at a solid-liquid interface." It is necessary to con- sider two distinct processes, that of melting, in which atoms leave the surface of the solid and become part of the liquid, and the converse process,

Jan 1, 1955

By N. LILIENBERGS

DURING the past few years, the requirements for steel have been raised so high that soundness is more important than ever before. The old practice was to mike steel ingots of sufficiently large sections to permit a considerable reduction of area in rolling and hammering to a given size, relying on the fact that by such rolling and hammering all cavities will be squeezed together and practically eliminated. The finished sizes, if found by inspection of the surface to be faultless, were therefore pronounced to be sound. But when such steel is ?worked up,? the manufacturer is surprised and disappointed to find that it splits, or that streaks and seams make the product unmarketable. Large sections, such as rails, beams or heavy forgings, may, within certain limits, be sufficiently strong, even if the sides of the cavities are only squeezed, and not welded together. But it is well known that, in the interior of heavy articles, under certain conditions, forging may develop small streaks into large cavities. Small sections, steel for ordnance and tubes, and numberless articles in the tool-trade, always show up the defects. It may be doubted whether cavities in steel ingots can ever be completely welded. The old theory, is, that the silver-clear blow-holes, without the blue oxide, can be welded by sufficient working. They are, however, not empty, but are filled with carbonic oxide. It is admitted that the "blue" cavities, resulting from air mechanically drawn down into the mold during the casting, can never be welded, because the oxide does not melt, and there would be no escape for it if it did. The only way in which steel can be made satisfactory for the above-named particular purposes is by having it ?dead molten." But then the trouble of piping is encountered. As is well known, a pipe is the result of the contraction of

May 1, 1906

By H. I. Aaronson, C. Laird

Although the past results of X-ray experiments indicate that the broad faces of 0' plates are coherent with their matrix, dislocations lying in arrays have frequently been observed at these boundaries by transmission electron microscopy. Critical experiments employing the latter technique have been carried out in order to determine the origin of these dislocations. It is concluded that 8' plates are essentially coherent with the matrix at their broad faces throughout the aging temperature/time envelope studied. Virtually all of the dislocation arrays observed are deduced to have been formed by plastic deformation accompanying transformation. The proportion of dislocations arising from convexity of the plates is shown to be negligible by comparison with that from plastic deformation. At the higher aging temperatures, a[001] dislocations appeared in moderate numbers. These dislocations were traced directly, however, to the ledgewise dissolution of 0' occasioned by the formation nearby of 0 crystals. On the other hand, since there is a parametric difference normal to the broad faces of the ?' plates, mismatch dislocations do form at their edges. A previous conclusion that these dislocations have Burgers vectors of type a[001] was confirmed directly. The edges of 0' plates were observed to develop octagonal shapes when growing, but circular shapes during dissolution. 1 HIS paper presents the results of an investigation of the interfacial structures of plates of the transitional phase, 8', formed in an A1-4 pct Cu alloy. In a companion paper, Part 11, the effects of these structures upon the migration kinetics of a:?f boundaries are reported. This work is pa.rt of a general program designed to establish the basis of precipitate morphology. The present authors in Al-Ag,1 and whitton2 previously in U-C alloys, have used transmission electron microscopy to examine directly the vander Merwe3-6 networks of dislocations anticipated7 to compensate the small amount of lattice misfit normally founda at the broad faces of Widmanstatten plates. Since the broad faces of 0' plates are considered to be perfectly coherent with the corresponding habit planes in the a matrix,' no dislocations should be present at these faces. Many reports have been published, however, giving evidence to the contrary.10-18 The primary objective of this investigation was therefore to ascertain the nature of these dislocation structures. An attempt to do this is described in the first three sections of this paper. Inspection of the matching of the a and 8 ' lattices at the orientations of the 0:0' boundary corresponding to the edges of 0' plates raises the possibility that these edges may be made up of rather closely spaced edge- type misfit dislocations oriented so as to be sessile with respect to the lengthening or shortening of the plates. Since this structure should severely inhibit migration of the plate edges (Ref. 7, Part II), a situation not originally anticipated,' an experimental determination of the interfacial structure of the edges of 8' plates was clearly in order, and is reported in Section III. Those aspects of the experimental procedure applicable to both Parts I and I1 are presented in the next section. Specific procedures applicable to individual aspects of each investigation, and also the relevant surveys of the literature, are then individually reported in the appropriate sections. I) GENERAL EXPERIMENTAL PROCEDURE The material used in both parts of these studies was the same as that of a previous investigation:" strips of A1-3.93 pct Cu, 0.009 in. thick, prepared as before, solution-annealed at 548°C for 6 hr, and quenched. Details of subsequent aging, and in some cases deformation treatments, are given in the Experimental Procedure sections of the individual parts of both papers. Specimens of the heat-treated strips were electro-thinned as beforeLg and examined in a Philips EM 200 microscope equipped with a goniometer stage. A commercial hot stage, of the grid-heater type and capable of * 30-deg tilt about one axis in the plane of the specimen, was also used for kinetic studies. The usual precaution of calibrating for the additional heat supplied by the electron beam was taken.19 A 16-mm cine cam-I era mounted outside the viewing window was frequently used to record the transformations. Conventional selected-area diffraction and dark-field viewing techniques were used to identify the precipitates in the foils. Normal bright-field images corresponding to two-beam diffracting conditions or dark-field images were employed to characterize the dislocations observed at the interfaces of the precipitates. The application of these techniques to the study of an interphase boundary, and the interpretation of the images,20'21 has been fully described in a previous paper.'

Jan 1, 1969

By ALESSANDRA SAVAZZINI REIS

A crescente preocupação em relação à sustentabilidade ambiental no setor de cerâmica vermelha associada ao alto consumo de argila, leva à busca de alternativas de incorporação de resíduos na massa argilosa. Com isso, vê-se a necessidade de caracterizar resíduos usados em cerâmica vermelha. As olarias brasileiras consomem cerca de 10 milhões de toneladas de argila ao mês para produção de telhas e blocos. O resíduo da indústria de rocha ornamental e a lama de alto forno podem se tornar passivos ambientais caso não sejam reaproveitados. O objetivo deste trabalho visa caracterizar e avaliar as propriedades cerâmicas em massas argilosas contendo resíduo de rocha e lama de alto forno. Os resíduos foram caracterizados por meio de ensaios de FRX, DRX, limites de Atterberg e granulometria. Massas argilosas com resíduos em teores variando de 5% a 50% (massa) foram conformadas, queimadas em forno industrial na olaria à 850ºC para verificação de: absorção de água, porosidade, massa específica aparente, e resistência mecânica. Os resultados mostram que a massa argilosa com o resíduo de rocha no teor de 50% apresentou os melhores valores das propriedades cerâmicas analisadas e maior resistência mecânica, tais melhorias também foram verificadas na massa argilosa com lama de alto forno no teor de 5%.

Oct 30, 2017

By E. S. Moore

GOLD was discovered previous to the year 1900 on the east shore of Emerald lake, Afton township, Timagami Forest Reserve. It was found in a small cavern in banded iron formation, close to the water's edge. This occurrence of gold was mentioned in several reports that referred briefly to this area, and prospectors evinced considerable interest in the region. It was not, however, until the Golden Rose Mining Company, which was incorporated in 1909, started operations that much work was done on the property. In 1915-16, this Company, under the direction of E. J. Townsend, the President, did a considerable amount of work. A small mill was built and ore was extracted from pits, trenches, and a one~ hundred-foot shaft. In 1927, Afton Mines, Limited, was incorporated to take over the property, and about thirty men were employed for a time. During 1934, the New Golden Rose Mining Company was organized to handle the property, and the Consolidated Mining and Smelting Company of Canada, Limited, undertook to develop the mine. In March of the following year, this Company began deepening the shaft from 100 feet to 500 feet. A considerable amount of drilling had previously been done on the hill of iron formation in which the mine is located. Further drilling was done from the surface, and altogether about twelve holes have been put down to test the formations. Over 2,000 feet of drilling has also been done from the underground workings. The mine is now known officially as the New Golden Rose mine, although to many it is better known as the Afton. To reach the property during the summer months, there is a boat trip of about thirty miles from Timagami, a wagon-road portage of one mile to Obabika lake, a boat trip of ten miles on this lake, and finally a wagon-road portage of one and one-quarter miles to Emerald lake. The mine lies about three-quarters of a mile down the east shore of the lake. A 75 h.p. Diesel engine and compressor were taken in over this' route last summer, and it is evident that the transportation problem is quite a serious one. Airplanes have been much in use, and a winter road runs from the mine to Chudleigh, on the .Canadian National railway near Sudbury.

Jan 1, 1936

By Patrick J. Ryan, Johann F. Kerl, Angelos N. Findikakis

Introduction Tailings disposal methods used by the mining industry include the use of on-land impoundments, surface and underground mine backfill and marine disposal. The latter method, where applicable and under certain circumstances, can be the most economical and best environmental option. The term marine disposal is used to describe deposition of tailings in the open ocean, coastal waters, fjords and inland lakes. A major element in planning and designing a marine outfall is the assessment of its potential environmental impacts. The nature of the disposed tailings, and the physical, chemical, and biological characteristics of the receiving water body must be carefully assessed prior to deciding whether marine disposal is an acceptable option for a particular project. During the last decade, the North American mining industry has demonstrated a commitment to studying potential adverse environmental impacts of marine tailings disposal and to continue monitoring of the receiving waters. Extensive monitoring programs have been undertaken by Canadian mines. Marine tailings disposal is not used in the United States today. One of the largest U.S. mines proposing to use this option is the Quartz Hill mine of U.S. Borax in Southeastern Alaska. To assure the regulatory agencies and the public of the viability and acceptability of this option, U.S. Borax undertook an extensive program of environmental studies aimed at assessing the impact of marine tailings disposal. This program was part of the feasibility and environmental permitting studies conducted by Bechtel Civil & Minerals, Inc, on behalf of U.S. Borax. Due to the unique nature of the proposed tailings disposal system, a Board of Consultants was established. The Board assisted in planning the modeling and field program and reviewed ongoing work. This paper outlines the basic elements of the marine tailings disposal study program which can be viewed as a prototype for similar studies elsewhere. Background The Quartz Hill molybdenum deposit is located on a knoll in an elevated valley in a mountainous region of southeast Alaska, about 45 miles east of Ketchikan (Figure 1).

Jan 1, 1986

By B. Gamble

Solid Energy's project evaluation process utilises a standard staged gate approach, with five levels leading ultimately to project execution (level 6). For a project to progress through each level, specific financial criteria need to be satisfied. Solid Energy primarily use value based (discounted cash flow) metrics to support investment decisions. Within this approach Solid Energy utilise a number risk-based techniques to quantify project uncertainty. This includes the use of risk-based probabilistic analysis using Monte Carlo simulation and probability-based scenario analysis. Figure 1 shows the net present value (NPV) cumulative probability. Project risks are identified through comprehensive risk workshops. The output of these workshops (list of key risks, ranges of uncertainty and probability of occurrence), is quantified within the financial models. Incorporating this risk information on a probabilistic basis allows an investment decision to be made with a robust knowledge of the range of possible project outcomes along with the likelihood (probability) of those outcomes occurring, for example 80 per cent confidence that the project value will be greater than NZ$10 M, 50 per cent confident it will be greater than NZ$50 M and ten per cent confident it will be greater than NZ$70 M. Incorporating risk implicitly into the financial analysis allows the business to easily evaluate/measure projects with different risk profiles. The detailed risk analysis does away with the complexity of arbitrary risk-based hurdle (discount) rates, as projects can be evaluated based on their specific risk characteristics. Whether a project will progress to the next level of investment and ultimately into implementation depends firstly on the value assessment in comparison with the associated risk/uncertainty, and secondly matching this with the businesses appetite for risk. At Solid Energy standard criteria are used for specific project evaluations, but in addition projects are considered on a portfolio or strategic basis also. Solid Energy attempts to maintain a mix of low risk (low value) projects with some high risk (high value) opportunities. The mix of projects must remain in line with the shareholders' risk appetite. One of the keys to a successful investment decision is ensuring that the appropriate information is available to decision-makers so that they may proceed with a comprehensive understanding of the risks and impacts associated with the decision.

Jan 1, 2007

By William J. Maloney

Blind drilled shafts are becoming increasingly popular as a secondary and sometimes primary means of ventilation. This is particularly true in the Appalachian coalfields. Some reasons for the rebirth of blind shafts are economics, timeliness, safety characteristics and their inherent independence from underground operations. Blind drilling has had limited use in hard rock and tunneling ventilation. Advances in cutters, bit design, equipment and lining systems have made blind drilled shafts the shaft construction technique of choice for ventilation specialists. History of blind drilling Blind drilling's roots include the Nevada test site, the coalfields of Appalachia and Germany, and the uranium mines of Arizona. Early technology was developed using a variety of equipment mainly of oilfield origin. Shafts completed by oilfield equipment ranged from the shallow 1.5 and 1.8 m (5 and 6 ft) lined shafts on the Nevada test site to two 3 m (10 ft) lined, 222 m (730 ft) deep shafts in Alberta for heavy oil development. Several of these shafts were completed to extraordinary depths. The record, completed in 1969, is a 2.28-m-diam (90-in.-diam), 1875-m (6150-ft) deep shaft, located in the Aleutian Islands of Alaska.

Jan 1, 1993

By J. F. Magee

THERE is nothing new about drag-line dredging for placer gold. The use of the separate unit for excavating preceded the large barge with bucket-line excavator mounted upon it, which has developed to a high state of perfection through use in every part of the world. But at present there is a vogue for a small, inexpensive plant to work economically the shallower gold gravel deposits that the bucket-line dredges do not work. The dragline dredge consists of the drag-line excavator, on caterpillar mounting on the edge of the dredging pond, which feeds the gravel to the washing plant, mounted on a floating barge in the pond. There have been more than twenty-five such plants built and operated in central and northern California and an unknown number in other States. There have been variations in details of design but the essentials are similar in all. I wish to describe the operation of a typical drag-line dredging plant, that of the Wyandotte Gold Dredging Company on the Farnan Ranch in the Oroville district. This organization of six active partners built their first plant on Wyandotte creek in the autumn of 1933. The operation was successful due to wise management, which was based upon good plant design and proper principles of operation. The partners elected one of their number, H. F. England, as manager with full control and responsibility. This plant and operation furnished the pattern for many subsequent ones.

Jan 1, 1937

By Alf Thidemann, Per Marius Nilsen

Tunnelling with hydraulic drills has been a success in Norway. In the fall of 1976 excavation of tunnels for the development of the Aabjoera scheme was started. Two and a half years later a total of 25 kilometers of tunnels are completed. During the most busy period 5 rigs with hydraulic drills were in operation. GENERAL INFORMATION. Aabjoera Hydro Electric Plant is located in the central part of Norway (Fig. 1). The scheme covers a mountaineous area between the Tosen Fiord and the valley of Namdalen. Water from the area of precipitation is transferred through 5 tunnels to the main reservoir. From here the water is conducted via a 10 km long, unlined supply tunnel down to the Kolsvik power station. The power station is situated underground with a short tailrace tunnel out in the fiord. Average head of water is 507 m. The Aabjoera plant is jointly owned by Helgeland Kraftlag A/S, 8650 Mosjøen and Nord-Trøndelag Elektrisitetsverk, 7700 Steinkjer. The Civil Engineering Division of the latter company has acted as Consulting Engineers for the scheme. General contractors for the whole scheme has been Ing. F. Selmer A/S, Box 6035, Etterstad, Oslo 6.

Jan 1, 1979