Search Documents

By Robert G. Pinkerton

Boyles Bros. Drilling Co. and Gibbons and Reed Company, both of Salt Lake City, Utah, have successfully combined into two joint ventures on the San Juan-Chama project of the U. S. Bureau of Reclamation. The Azotea Tunnel is 12.7 miles in length; the inlet portal is on the Navajo River in Archileta County, Colorado, and the outlet portal is in New Mexico, about 10 miles south of the state border. The Oso Tunnel lies immediately to the north of the Azotea Tunnel and discharges water directly into it. We are presently driving both tunnels with mechanical boring machines from their portals at the Navajo River. Both tunnels are circular, fully concrete lined. The Azotea Tunnel has a finished diameter of 10 ft. 11 inches while the Oso Tunnel is 8 ft 7 inches in diameter. Both tunnels are supported with circular, structural steel rings as required by ground conditions. In good ground rock bolts and steel roof plates are used.

Jan 1, 1967

By Malcolm T. Wane

The subject matter of this paper, "Applied Rock Mechanics?," has its genesis in a recent field trip taken by the author. A more or less standard question asked at the mines visited was "How are you using the principles of Rock Mechanics to assist you in maintaining an efficient, safe, and competitive mining operation?" The question was couched in a number of different forms, but the intent was to determine whether or not a general theory based on reason and the scientific method was applied or whether the alternatives of tradition, intuition, ?common sense', revelation, ?shotgun methods' or authoritarianism were invoked. Perhaps two responses to this query will be illustrative of the general nature of the replies. At operation XYZ an extension to the known ore body has been found. The extension is of large enough size and grade that a mining scheme using load-haul-damp techniques is envisaged. Since this represents a departure from the present mining scheme, questions have arisen regarding pillar sizes, room and entry sizes and possible support requirements. A task force has been set up to expeditiously plan for these things and write the necessary specifications and requirements. The fundamental question was posed to members of this group.

Jan 1, 1971

By M. S. Klima, A. P. Pinkerton

Solid-bowl (decanter) centrifuges are used extensively to dewater slurries in a wide range of industries. However, the application of decanters as classification devices is not as common. In this study, the performance of a continuous, pilot-scale, solid-bowl centrifuge was evaluated when classifying an ultrafine coal slurry containing nearly 60% material less than 10 µm. The test conditions included centrifuge howl and scroll speeds, volumetric feed rate, solids concentration and pond depth. Centrifuge performance was evaluated using size selectivity curves and the corresponding performance parameters, along with product yields and solids concentrations.

Jan 1, 2002

By G. W. Poling

Chemical and physical properties of thiol collectors are reexamined to compare the prospects of heavy metal-thiolate or disulphide surface reaction products acting as actual collector species. Recent evidences for the existence and importance of each of these types of adsorbed species on sulphide minerals are also discussed. A conclusion is reached that partial coverage by chemisorbed heavy metal thiolate is often sufficient to confer practical levels of hydrophobicity and floatability. Only on a few highly conducting and "noble" sulphides does adsorbed disulphide-type collector oxidation product appear to be significant.

Jan 1, 1976

By John D. Price

In the constant search for ways and means of improving the quality of coke and thus making its use at the blast-fornace more satisfactory and economical, it has become increasingly evident that the present laboratory tests do not show the full picture of a coke's value as a blast-furnace fuel. This fact was recognized by Dr. A. C. Pieldner thirty-five years ago: (Ref. 1) here is perhaps no phase of fuel technicology which has aroused more discussion or regarding which there is more difference of opinion than the properties of coke which make it most suitable for blast-furnaces and other uses." Dr. Fieldner followed this assertion with a statement to the effect that men who write on this subject today (1923) have, because of conflicting experimental evidence brought forth in recent years, far less positive opinions on the matter than did writers of some years past. One is led to wonder if these statements are not just as true now as they were when first made.

Jan 1, 1959

By Raj K. Singhal

This paper is a report on a task force study dealing with many facets of computerization. The primary mandate of the task force was to examine the software and hardware currently available for application relating to reserve estimation, mine planning, economic evaluation, equipment selection, production scheduling and composite mine simulation and to evaluate how adequately the software fulfills the user needs in surface mining of oil sands and coal. To meet its objectives the task force consulted extensively with the users, developers and suppliers of hardware and software. The paper outlines the approach taken by the task force to fulfill its mandate, summarizes its findings and presents some pointers which might be useful to others considering this type of evaluation.

Jan 1, 1986

By Harrison R. Cooper

Composition data is needed as input for executing process control and management of particulate separation for flotation control. While requirements for composition data can be satisfied in many cases by manual sampling and analysis, automatic sampling and assay systems are now viewed as justified for all but the simplest or smallest processes. On-stream X-ray fluorescence analysis (XRFA) has satisfied requirements for the main portion of metalliferous sulfide ore flotation processes as XRFA technology evolved in reliability and sophistication from its beginnings in the late 1950's. In recent years, advanced on-stream analysis technologies have reached levels of development suitable for use in process control to increase efficiencies of important processes in mining and minerals industries such as coal fines flotation and industrial minerals beneficiation (particularly phosphate beneficiation) where XRFA methods have been inapplicable. Recent technical developments pertinent to use of advanced technologies as well as improvements to established on-stream composition analysis methods are discussed.

Jan 1, 1989

By Bobby P. Faulkner

Allis-Chalmers has combined a new heat transfer device, called the ROLLER GRATE, with a unique processing scheme, resulting in the ROLLER GRATE Oil Shale Processing System of Allis-Chalmers. In order to test both the process and the equipment, a batch Process Development Unit (PDU) ROLLER GRATE retort was designed and built. This unit vas designed with the flexibility to process shale over a wide range of test conditions in order to demonstrate the attributes of the oil-shale processing system. Instrumentation on the PDU and extensive sampling of the effluent streams permitted the PDU test data to be used in the design and scale-up of the process. Over 30 tests have been conducted with Colorado shale, and over 25 tests have been run with an Indiana shale. In addition, rests have been run with California and Utah tar sands.

Jan 1, 1983

By F. Wolf, R. Ellmies

"Fluorspar is one of the most important industrial minerals. It has a wide range of applications, for example it is used in the steel and aluminum industry, and is also the raw material to produce hydrofluoric acid, Teflon or Gore-Tex. There are only a few major fluorspar mines worldwide, with China being the most important fluorspar producer (U.S. Geological Survey National Minerals Information Center, 2017). At Okorusu, Namibia, fluorspar has been mined with conventional open pit mining methods from 1955 until 2014 from a large scale metasomatic fluorspar deposit with seven identified orebodies. There are about 7 million tons of measured resources left with an average grade of 27.5 % CaF2. This paper is based at an MSc thesis at Technical University Freiberg and describes the design of an underground mine for the A and D orebodies with an annual production rate of 100,000 t acid-grade fluorspar product. By comparing different mining methods and adapting variants of access to the underground orebodies the paper will emphasize on the selection of a suitable mining technology, with a special focus on the economic considerations to decide about the most profitable operation. INTRODUCTION Mining holds an important part in the economy of Namibia. In 2016 11.1 % of the GDP was made through mining activities with 22 active mines (The Chamber of Mines of Namibia, 2016). Only one of them consists an underground mining operation. The global annual production of fluorspar is approximately 6 to 7 million t (U.S. Geological Survey National Minerals Information Center, 2017). Okorusu produced on average about 50.000 t annually in recent years (U.S. Geological Survey National Minerals In-formation Center, 2015). Okorusu Mine is Namibia’s only fluorspar mine. Fluorspar was mined in an open pit mine with four individual pits (A-D) since 1980. In 2014 the mine closed due to the increased stripping ratio and beneficiation problems. The mine assets were bought by Gecko Namibia. Currently Gecko uses parts of the processing plant for beneficiation of graphite from a neighboring mine. Figure 1 shows a panoramic view with the four pits and the mine village. The intent is to develop a concept for the further underground development of the mine. There are still about 7 million t of measured resources left in the deposit, with an average grade of 27.5 % CaF2. This study focusses on the underground mine design. The above-ground plant and facilities are considered as remaining unchanged."

Jan 1, 2018

By R. Markovic

The objective of this research study was the investigation of heavy metal removal from wastewaters of the "SARAKA" stream by using low-cost materials. These wastewaters flow into Krivelj River and through the network of existing rivers into regional water reservoirs. Sawdust, cardboard and fly ash were used as reactive materials in laboratory studies. Sawdust was obtained from oak and fir-wood while fly ash from heating station Bor, bitter-oak and oak. Experiments were carried out using real Saraka stream wastewaters and the degree of removal for iron, copper, manganese and zinc was investigated. The content of these heavy metals in Saraka stream wastewaters was under the limit of III and IV class of water (Law on Water - Official Register of the Republic of Serbia). Parameters such as flow rate of water, pH and effluent volume, contact time between water and reactive material, etc, were monitored during the experiments. All used materials give satisfactory results for iron and other heavy metals removal; the highest degree of removal was obtained by using fly ash.

Jan 1, 2006

By H. W. Seany

Over the years since the initial experiments with underground concreting were made in 1956, attesting to cope with the ground weight and pressure encountered in the development of a large-scale underground block caving system, the use of monolithic concrete linings has grown to include most of the primary development in the, mining area. Although the development cost of concrete linings is higher than either timber or steel-supported openings, the repair and maintenance costs are substantially lower, making concrete the most economical means of ground support. Other advantages are also apparent, in that concrete provides superior fireproofing, better ventilation, and a safer, cleaner working place.

Jan 1, 1965

By G. L. Smit

The Buffelsfontein Gold Mining Company is situated in the Klerks-dorp district of the Province of the Transvaal in the Republic of South Africa, approximately 100 miles west of Johannesburg. Gold production commenced in January 1957 and Uranium treatment of residue slimes as a by-product started in July 1957. The mining property is 5435 mining claims in extent, the equivalent of 7,988 acres or 12.5 square miles. The mine was initially exploited by the Pioneer Twin Shaft System, consisting of a 26 feet diameter down-cast shaft and a 22 feet diameter up-cast shaft, sunk in the north-west area of the mine to cater for the hoisting and ventilation requirements for a milling rate of 150,000 tons per month.

Jan 1, 1964

By J. M. Elegante

A belt drive attendant was working underground during his shift at the junction of two belt drives. He worked alone, but communicated with others at the mine by underground phone. At noon his shift foreman stopped by his workstation. At 2:00 p.m. he was contacted by phone by a fellow belt drive attendant. At 5:00 p.m., he was found dead by the oncoming evening shifter.

Jan 1, 1989

By A. Thatcher, C. Day, C. Meyer

The purpose of this paper is to provide general information about the bioaccessibility of metals and specific information about the use of bioaccessibility in risk assessments (human health risk assessments [HHRA] or ecological risk assessments [ERA]) and a list of sites where regulatory agencies have approved the use of bioaccessibility data in risk assessment. The memorandum also cites current U.S. Environmental Protection Agency (USEPA) guidance as well as state specific guidance where applicable. BRIEF HISTORY OF METAL BIOACCESSIBILITY TESTING AND METHODS The bioaccessible fraction of a constituent is that fraction that dissolves or desorbs from its matrix (e.g., soil) in the gastrointestinal tract and is available for absorption (USEPA 2007a; ITRC 2011; ITRC 2017). This is different from the bioavailable fraction, which is the percentage of the amount of an element that an organism is exposed to that is absorbed by that organism during a given time under defined conditions (USEPA 2007a). The bioaccessibility factor is the percentage of a metal that is potentially available for absorption and, therefore, is a conservative estimate of the bioavailable fraction since all that is available for absorption may not ultimately be absorbed into the organism’s system. Currently, there are two main techniques for estimating bioavailability of metals within a medium: in vivo animal studies (time-consuming and often cost-prohibitive), and in vitro tests that simulate human, or animal digestion in a laboratory setting. In vitro and in vivo test methods and protocols have been extensively evaluated by numerous researchers (Ruby et al. 1996; Rodriguez and Basta 1999; Sips et al. 1998; Sips et al. 2001; Molly et al 1993; Oomen et al 2002; Kelley et al. 2002; Oomen et al. 2003; Furman et al. 2006; Drexler and Brattin 2007; Basta et al. 2007; Wragg et al. 2009; Wragg et al. 2011; Chaney et al. 2011; Bradham et al. 2015; Bradham et al. 2018). The most recent scientific literature demonstrates that protocols used to estimate the bioavailability of metals to mammals also predict bioavailability of metals to birds as well (Beyer et al., 2016).

Jan 1, 2019

By S. A. Braley

Water is our most important natural resource, for without it there is no life. It is also the principal natural resource for all manufacturing processes, in particular for the development of power. For these reasons it is essential that water be protected and conserved, with the realization that its quality 18 as important as the water itself. A significant factor in the quality of ground water is the mining of coal -- that other main ingredient of Power. In the mining of coal it is necessary to disturb the geological strata overlying or adjacent to the coal seam. This procedure not only releases water from water-bearing strata or underground aquifers but also exposes other minerals which eventually become the source of pollution or deterioration of the released water as well as of the surface stream into which It is discharged It is then evident that in attempting to utilize one essential natural resource there is degradation of the quality of the other. Many selfishly assume that the principal function of a stream is fishing and recreation, but the real function is the support of industry and agriculture upon which civilization is dependent.

Jan 1, 1959

By Manfred Hager

The ability of conveyor belts to transport large mass throughputs economically over previously unprepared ground has resulted in this system achieving great and extensive use. A significant component in this development is the conveyor belt itself. The development of high strength steel cord conveyor belts involves the optimising of splice design, the use of excellent rubber material especially in the splice, good craftsmanship during splice production and modern field vulcanisation equipment. The durability of a splice for belts of class St 3000 up to St 790 is expressed by the fatigue strength under dynamic stress. The results obtained with a test method and equipment developed by the University of Hannover indicate the present state of the art in this field. Belts of high nominal strength used on inclined long distance conveyors reach splice fatigue strengths of about 3000 N/mm. The design should only exploit approximately 50% of the fatigue strength determined in the tests as maximum operating stress. IMPORTANCE OF CONVEYOR BELT SYSTEMS The use of conveyor belt technology has expanded considerably over the last decades in the bulk goods transportation sector. Because of the favourable transport costs and the technology's adaptability to specific topographies, belt conveyors frequently represent the most economic solution. When flows of goods are large, as in German lignite mining operations, where masses of up to 40,000 t/h are given, it is the only technically feasible alternative. The use of belt conveyor systems allows the sensible distribution of the waste and the production of the coal (Hager, 1981). But this transportation alternative is also suitable when the masses involved are smaller. Whereas conveyor belts were only suitable for loose bulk goods up until a few years ago, today they are frequently also used for hard rock open cast mines, e.g. in the production of copper ore. Because of the favourable transport costs it is frequently still economic to use mobile crushers with a throughput of up to 10,000 t h 6 which breakdown the large blocks produced y explosives into transportable grain sizes. In many operations, trucks are only used to provide flexibility between the excavator and the crusher, i.e. over short routes, and the long, frequently steep, transport paths to the processing plant or to the spreader are undertaken by belt conveyors (Einenkel et al., 1992). The advantages of belt conveyors, i.e. to cope with large mass flows over inclines and down slopes of up to 1:4 have resulted in this system gaining very extensive use throughout the world. The conveyors can be installed over for the most part unprepared ground with suitable vertical radii, adapted to the locally available belt material. In the process individual conveyor belts with lengths of up to 15 km, and in the underground sector with lift heights of up to 1 km, have been built and operated. This great variety of application possibilities is complemented by a limited ability to pass through horizontal curves. This can be achieved with the help of design measures on the conveyor whilst bearing in mind the characteristics of the belt. STRESSING OF CONVEYOR BELTS IN DIFFERENT TYPES OF PLANT The advantage of conveyor belts compared with other systems is also to be found in the large available service-time window, i.e. the excellent reliability and the low costs of energy consumption and maintenance. It is in particular the reliability of a belt transport system which depends to a great degree on its main component, that is the belt - in all its different types and variations. For this reason, the belt is also given the greatest attention in the development of the individual components, because it is the belt which must be designed optimally with regard to various factors. The specific properties of the conveyor belt then assert a considerable influence on the design and sizing of most other components in a

Jan 1, 1993

By M. S. Prasad

This paper presents the process methods of beneficiating various copper-cobalt and copper-zinc ores mined by Gecamines in Zaire. Geology and mineralization of both sedimentary and vein-type deposits are described with special emphasis on the production of oxide, dolomitic and sulfide concentrates. Description of different types of concentrators and their treatment methods are discussed for the production of sulfide, oxide and dolomitic concentrates. Production of concentrates, their consumption and stocks are briefly reviewed. Modernization of the concentrators with substantial investments on grinding, classification, flotation methods and tailings treatments are also discussed and to improve the metallurgical efficiency of 'the concentrators to improve the production quality and quantity of concentrates.

Jan 1, 1992

By S. K. Nicol

Flotation, water-washing cyclones (hydrocyclones) and spiral concentrators are the three process units most commonly utilised in fine coal preparation. The results of testwork conducted on these three units will be presented and their performance and separation characteristics examined in detail. In particular, the dependence of the separation characteristics of each unit on particle size and the constraint this places on product quality (ash and sulphur levels) will be discussed. This dependence will be shown to be a critical criterion in the selection of fine coal circuits.

Jan 1, 1986

By A. J. Basu

Geotechnical design plays a key role in mine design. I A proper geotechnical design provides a safe working environment and facilitates efficient mining operation. There are mainly three design approaches I) judgmental, based on observational and experiential facts, 2) empirical, based on empirical design formulae, and 3) analytical, incorporating numerical analysis. Most design applications are based on the design methods one and two as mentioned earlier. However, complexities arise in deep underground mining operations and deep open pit mines. These complexities and difficult geological environment introduce more uncertainties and simple empirical formulae would not be adequate as a design tool. These situations require numerical modelling and analysis of the design problems including interpretation of the results obtained from the analysis. There are several tools available for performing the numerical modelling and analysis. A brief review of the available tools was addressed earlier (Basu and Kuruppu, 1995). The authors selected ANSYS (a general purpose finite element analysis tool) for use in mining geomechanics and geotechnical design. This paper includes several examples demonstrating the applicability of this software in designing structures applicable to mining geomechnics. The authors hope that the design examples will demonstrate the use of the numerical modelling and analysis application in excavation design.

Jan 1, 1996

By Donald W. Gentry

Introduction The mining industry is perhaps best characterized by the numerous and abnormally high risks associated with the business of mining and by its most basic assets - ore deposits, people and technology. At the most fundamental level, it is the quality and effective utilization of these basic assets that determine a mining company's ability to compete efficiently in the international market place. The gold industry has received much attention in recent years and especially in recent months, for good reason. This commodity serves as an excellent platform for the subsequent discussion of these three basic assets and their role in mining's future. Facets of the gold industry The fate of this noble metal in recent times illustrates some of the various risks associated with the mining industry and the importance of high-quality assets, whether they be ore deposits, people or technologies. The following comments pertaining to the gold industry help place proper focus on subsequent discussions. All monetary amounts given are in US dollars. Throughout 1997, falling gold prices broke record after record: first hitting three-year lows, then a 12-year low in July and finally an 18-year low at year's end. From Jan. 1 through Dec. 31, 1997, the price of gold fell by more than $2.57/g ($80/oz), or some 22%. The decline in gold-mining profitability and stock prices was even more dramatic. At the beginning of 1997, the 20 largest gold producers in North America had a market capitalization of approximately $44.5 billion. At year's end, this market cap had fallen to $26.2 billion, a reduction of 41%. The total market cap of all the world's gold companies fell from $71 billion to $46 billion, a 35% drop (Serwer, 1998). Analyses suggest that, at a spot gold price of $9.65/g ($300/oz), only one, or possibly two, North American gold-producing companies can make money when break-even or "total costs of production" are considered. While strong hedge positions mitigate this situation in the short term, clearly, this is an industry in desperate straits. For example, write-downs for North American producers in 1997 were approximately $2.5 billion. Speculative short positions in 1997 were near historical record highs and generally exceeded long positions by factors of 9:1 or 10:1. Much of this is driven by some US commercial banks, hedge fund managers and commodity speculators who can significantly move gold prices sharply over short periods of time by selling gold they do not own in the expectation they can buy it back at a lower price before they have to deliver. These signifcant short positions are likely to continue as long as central banks are willing to sell or loan gold to financial institutions that in turn make the gold available to speculators who hope to capitalize on price fluctuations. The Far East accounts for approximately 26% of the annual demand for gold. Including India, the region accounts for 43% of total demand. More than 85% of the physical demand for gold is for investment jewelry in Asia and the Middle East. This demand is extraordinarily price sensitive. The fairly recent turmoil in Asian markets and economies, combined with currency devaluations throughout the region, have made gold more expensive (30% to 50% in local currencies) for those peoples most likely to treat gold as a safe investment haven. Higher interest rates also have reduced the amount of money they have to spend on consumer goods such as jewelry. All of these recent Asian events are deflationary in nature. Deflation, if coincident with rising unemployment, could result in significant dishoarding of gold. There is one key fact to remember when analyzing

Jan 1, 1999