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By J. L. Mehaffey

A variety of chemicals offered by Armak were evaluated as dewatering aids for aqueous slurries of silica sand, sparsand and feldspar; an established commercial dewatering aid was used as a control. A number of Armak's potential dewatering aids yielded lower moisture retention values than did the commercial product on all of the mineral samples. In addition to the chemical dewatering evaluations, some of the mechanisms involved in the removal of water from these mineral samples were examined.

Jan 1, 1983

By D. T. Hristopulos, A. Pavlides, C. Roumpos

In many of the lignite mines in Greece that supply the nearby power plants, the lignite deposits are multilayered and faults destroy the spatial continuity. This fact complicates lignite exploitation and the profitability evaluation of each layer. The location of a lignite layer could be so deep compared to other layers, that its exploitation would not be profitable. The purpose of this paper is the development of a suitable profitability index to help with the evaluation of the profitability of separate lignite layers. The definition of the profitability index is given and an algorithm is formulated that calculates the profitability index and evaluates whether each layer should be mined by comparison with a critical threshold value. The profitability index algorithm is applied to the multilayered lignite deposit of Amyndeo mine. It should be noted that the proposed index could be used in any kind of multilayered deposit, not just lignite.

Jan 1, 2011

By H. J. Bickel

This paper is concerned with general concepts and statistical devices used in projecting overall energy requirements. Particular emphasis is given to the use of individual end- use markets as an approach to developing future overall energy requirements, and translating these requirements into fuel consumption.

Jan 1, 1962

By Wilbur I. Duvall

INTRODUCTION This chapter outlines some general principles and procedures that a rock mechanics engineer can use to arrive at a logical design for the size, shape, and spacings of underground openings in various types of com¬petent rock formations. Rock formations can be clas¬sified into six major categories which are useful for design purposes, provided the necessary input data are available regarding the geology of the site, the physical properties of the rock, the in-situ stress field in the rock, and the general geometry of the underground openings. The US Bureau of Mines (USBM) developed a rock classification system based upon these concepts and found it to be useful for design purposes (Obert, et al., 1960; Obert and Duvall, 1967). This classification sys¬tem is given in Table 1; however, an extra column has been added to the original classification to indicate the appropriate design techniques for each rock class. In this classification system, two main classes of rock are considered: competent rock and incompetent rock. Competent Rock Competent rock is any rock which, because of its mechanical and geological characteristics, is capable of sustaining underground openings without the aid of any structural support except that provided by unmined rock in the form of pillars and side walls, etc. Roof bolts and small random props which support only local loose rock are not considered structural supports. Competent rock is further subdivided into three ad¬ditional categories-massive, laminated, and jointed¬ which are defined as follows: Massive Rock: Massive rock is a rock formation where the spacing between mechanical defects such as joints, partings, or faults is equal to or greater than the critical dimensions of openings, or where the strength of the bond across these mechanical defects is com¬parable to the rock strength. Laminated Rock: Laminated rock is a rock forma¬tion divided by approximately parallel planes of weak¬ness into lamina whose thicknesses are small compared to critical dimensions of openings and where the bond between the lamina is weak compared to the rock strength. Elastic Rock-This is rock whose physical proper¬ties will permit the use of elastic theory to predict strains and displacements from applied stresses. Inelastic Rock-This is rock whose physical proper¬ties are such that strains and displacements are a strong function of time as well as applied stress. Incompetent Rock Incompetent rock is any rock which, because of its mechanical and geologic characteristics, is not capable of sustaining underground openings without the aid of additional structural support in the form of linings, steel sets, or systems of props. This classification system for rock depends not only on the mechanical and geologic characteristics of the rock but on the size of openings and their depth be¬low the surface. For example, many competent rocks at shallow depths for small stress fields could become inelastic rock at greater depths and larger stress fields, or competent massive rock for small openings could be¬come laminated or jointed rock for larger openings. Thus, to classify rock for design purposes requires a knowledge of the geologic properties of the rock mass, the physical properties of the rock, the general size of the openings to be mined, and the average range of the in-situ stress field to be encountered. To design underground openings and structures in rock, it is necessary to use criteria of failure for rock under various stress conditions, and to use safety factors to allow for differences between laboratory and in-situ strength properties of rock and to account for errors in¬troduced by the various assumptions made in the design process. Criteria of failure based on maximum stresses have been found to give reliable results in practice. Thus, it is assumed that rock will fail in tension when the tensile stress exceeds the tensile strength of the rock as determined by a standard modulus of rupture test on samples of rock core. If the tensile stresses in rock are small, then it is assumed that the rock will fail at a value of compressive stress equal to the compressive strength of the rock as determined by standard uniaxial compres¬sive strength tests on samples of rock core. These fail¬ure criteria, when used with appropriate safety factors, can be expressed as:

Jan 1, 1982

By J. W. Powell

Several years prior to 1962, it became obvious that in order to develop ore reserves below the Storke Level, it would be necessary to devise a method to facilitate the ore being lifted three hundred feet to the surface or six hundred feet to the mill. The final plans called for an underground crusher complex with two stages of crushing and a conveyor belt gallery for transport of the ore six hundred feet above, to the third crushing stage. Access into the area was gained in 1962, by sinking Five Shaft approximately one quarter mile southwest of the proposed complex site, and drifting into the area. Collar elevation of Five Shaft is three hundred feet above the 600 Level Crusher Complex. All muck was loaded into ten-ton granby cars, hoisted to the surface and dumped. (See Figure 1 for the relationship between Five Shaft and the Crusher Area) Drifting into the Crusher Area contunued until 1965 at which time the Crusher Room Cutout was started. The Crusher Access Drift (CAD on Figure 2) war driven and mining pm- ceeded according to the description on drawings marked Figure 3a and 3b. After the arch portion of the Cutout was excavated and concreted, removal of the center "pillar" commenced. This muck was removed with an Eimco 123C crawler-mounted front-end loader. (See Figure 4) A total of 576,000 cubic feet of rock was removed from the Crusher Cutout. All sup- port was afforded by grouted roofbolts on a specified pattern, as shown in Figure 3c. Crane support columns were put into place and held by braces welded to roofbolt heads. Sidewalls and endwalls were formed and concreted. (See Figure 5 for the finished product)

Jan 1, 1970

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 D. Nilsson

This paper demonstrates the importance of including a discount rate in the determination of the optimum final&apos; depth of an open pit. Without a proper discount rate, a pit will probably end up too deep. Another consideration is future underground mining. If underground mining is profitable, the pit may need to be shallower. Of all of the investments needed, only mining equipment and the underground mine should be included, and amortization and depreciation should not he included in the study.

Jan 1, 1997

By A. A. Davis

The decade of the 70?s saw a series of landmark environmental resource programs enacted by the Congress. Many states followed suit, so that by the end of the decade air quality, water pollution, and the conservation of other natural resources, including minerals, were the subject of a wide-ranging body of laws, policies, regulations, and procedures. Many of the actions required or permitted by this rule-making involved areas for which adequate information and substantial experience were not available. Moreover, goals and objectives were sometimes established which were enormously difficult to achieve technically, or of such formidable expense as to cause concern about their consequences in the marketplace. It is therefore hardly surprising that one product of all this activity has been a mass of litigation. Court dockets are crowded with suits and counter-suits involving both substantive and procedural aspects of environmental protection. Indeed, it is probably fair to say that the volume and range of environmentally-related disputes brought before the courts parallels that generated by the civil rights movement a decade ago. There were also some new dimensions to the environmental movement. For the first time, the national environmental policy act required agencies to prepare environmental impact statements when proposed projects or activities would have substantial impacts on environmental resources. Another requirement of many of the new programs mandated meaningful citizen participation in public decision-making. Here, as elsewhere, the purpose was admirable, but guidelines were vague, and the result often was inaction, polarization, and litigation.

Jan 1, 1986

"Outotec’s TankCell® e500 flotation cell was commissioned during 2014 at the Kevitsa Mine in northern Finland. The TankCell® e500 is the first cell in this size class (500m3) to be run in an operational duty and it has been working as the first rougher in the copper flotation circuit. Treating around 850tph with an average grade of 0.3% Cu the TankCell® e500 has run with an average copper recovery of 71% and an average enrichment ratio of 50. In addition the cell has proved to be very energy efficient, operating with a specific energy of around 0.4kW/m3 under production conditions. This presentation will provide a review of the installation and operation of the TankCell® e500 at Kevitsa and will summarize the results found in the published literature from the various testing campaigns conducted around the cell. INTRODUCTION The TankCell e500 was installed and commissioned at the Kevitsa mine in northern Finland in 2014. Post startup the cell was initially run for testing and optimization with various test campaigns undertaken. but was subsequently taken into a production duty (Mattson et al., 2015a). At Kevitsa the cell is run as the first copper rougher replacing the previous two copper roughers (both 160m3) in this duty. The unit is running at between 38-40% solids at a feed rate of approximately 850tph. Since operational the average copper recovery from this single cell has been around 71% copper. This is typically with an enrichment ratio of around 50 being fed with an average head grade of 0.3% copper. More details on the circuit configuration and production performance of the e500 at Kevitsa can be found in Mattson et al., (2015a) and Murphy et al., (2016). In addition through the optimization program with the use of a variable speed drive controlling rotor speed it was found the the e500 was very energy efficient under production conditions. During this work the cell was found to run at a specific energy of around 0.4kW/m3 which exceeded design expectations (Xia et al., 2015)."

Jan 1, 2016

By Fred Perea

The practical example of the effectiveness and necessity of establishing and maintaining close communications between the design engineering section and operating section of a large plant concerned with the building of an underground crusher will be presented.

Jan 1, 1969

By Richard M. Bennett

Twelve linear test foundations were constructed over an advancing longwall panel in southern Illinois, six were located along the centerline, and six in the maximum tension zone. One footing in each set was a control foundation constructed according to conventional practice. It suffered severe damage. Footings with reinforcing bare and post-tensioning had much smaller elongations, with the post-tensioning preventing cracking of the footing. Footing-soil interface treatments of plastic-on-sand and plastic-on-soil served to reduce damage. The addition of steel fibers to the footing had about the same effect as an interface treatment. Sill plate construction (butt-jointed versus lap-jointed) appeared to significantly affect the behavior.

Jan 1, 1986

By Moussa Wone, V. Nasri, F. Guimbal, D. Andre

The Magenta underground station was constructed in the heart of Paris in saturated soft soil and at shallow depth. To investigate the surface settlement and the deformation of the concrete liner, innovative techniques combined with a vast campaign of monitoring were applied. The monitoring data and a simple three-dimensional ?nite element analysis were used to assess the accuracy of the two-dimensional ?nite element model originally utilized in the design of the station. The deformation of the concrete liner was monitored using vibrating wire extensometers. Their performance was validated by the data obtained from monitoring and also by a simpli?ed ?nite element analysis.

Jan 1, 2003

By S. Vogely, J. Trescot, D. Connor, F. Beloy

In 2001, the Minntac Division of US-Steel retrofitted one of their Grate-Kiln Iron Ore Pelletizng lines with a Ported-Kiln Air Injection System (PKAIS) the first of it’s kind in the world for oxide pellets. The Ported Kiln System injects air under the bed of pellets in the rotary kiln, causing rapid oxidation of the magnetite pellets. This rapid oxidation allows for lower kiln temperatures, reducing fuel demand; less heat load on the annular cooler; and higher pellet quality. Both the process and the equipment are patented developments by Metso Minerals. This paper discusses the process, the key equipment, and the benefits to the pellet plant and the downstream blast furnace operations.

Jan 1, 2004

By Ezra L. Kotzin

Foundry sands used to make molds and cores have been very important to foundrymen since metal casting began hundreds of years ago. They are now used in two basic ways, either in an uncured green state, grain-bonded with clay, or in a set cured state achieved with sand that, mixed with resins or oils, is cured by baking or by chemical reaction. The term sand, as generally used in foundry applications, may best be defined as material composed of granular particles of mineral matter, ranging in size from 0.5 to 2 mm in diameter. The particulate nature of the material may be the result of natural disaggregation or result from crushing and screening of rock or ceramic materials; crushed and screened products are sometimes referred to as "manufactured sand." Based on their origin, the raw materials for foundry sands will vary in grain shape, grain composition, relative surface, grain size, and grain distribution patterns. These properties, in addition to their chemical analyses, sintering point and expansion characteristics play an important part in the choice of sands used as the base molding or core aggregate in metal casting. Sands with different origins may be blended to produce specific compositions and grain size distributions. Early raw material requirements based on silica sand were simple, but as sand/core/mold technology became more sophisticated and binder technology continued to be developed, the physical properties of foundry sands became more critical. Silica sand is composed of quartz, along with, in most cases, small amounts of feldspar, mica, clay, and other common minerals. Although silica sand is still by far the most widely used base material in production of molds and cores used in metal casting, other natural mineral sands have their own unique characteristics and fill an important niche in special applications. As a result, the term sand, as applied to raw materials used in metal casting, has been logically extended to include granular materials composed of a group of minerals other than quartz. With increased use in advanced foundry technology, natural sands composed predominantly of zircon, chromite, staurolite, or aluminum silicate minerals and of granularized chromite or olivine, have become more than just alternate materials and are now commonly classified as sands when the grains are sand-sized. Foundry sand may therefore be considered under two categories: silica sands and non-silica sands.

Jan 1, 1994

By Richard L. Gordon, William A. Vogely

In this chapter, the principles that determine the procedures selected to transform minerals in the ground into usable commodities are re¬viewed.a I argue here that straightforward mod¬ification of the modern general economic theory of production suffices to meet the practical needs of a mineral economist. Therefore, the chapter is largely a review of the general economic theory of production to which is added discussion of the special prob¬lems of the exhaustibility of mineral resources and the economics of finding and developing economically recoverable minerals. In many cases, propositions applicable to all industries are reviewed because they are not treated ade¬quately in prior texts. In the discussion, use is frequently made of basic concepts of differential calculus widely used in economics. However, this is supple¬mented by simpler verbal and graphical treat¬ments, so that those either untrained in the calculus or, as is often the case, whose skills have grown rusty, can still follow the discus¬sion. Where the argument depends critically on the mathematics, this is noted and the justifi¬cation for including the material is provided. In addition, an appendix outlines the critical mathematics and reviews some of the numerous books published that provide the most readable available introduction to the subject. Further¬more, mineral industries examples are used to suggest the relevance of the theory. THE RELEVANCE OF THE ECONOMICS OF PRODUCTION Three basic steps are involved in establishing the relevance of economic analysis to mineral ¬industries decision making. First, the general theory of production must be defined, and its relationship to the simpler models of production stressed in economics textbooks must be noted. Second, the critical modification-considera¬tion of the problems of discovering and devel¬oping mineral deposits-must be developed. It turns out this too involves a special case of the general theory of production. Third, the concept of an economics of exhaustible resources must be explored sufficiently to suggest why its practical relevance is doubtful (or at least far smaller than the numerous writers on the subject seem to believe). The present approach is heavily influenced by post-1945 developments in economic anal¬ysis. Particularly since World War II, economic theory has drastically changed its scope. First, stress has increased greatly upon viewing the economy as a network of intertwined markets known technically as the general equilibrium system.b In this view, not only is the economy viewed as an integrated system, but critical con¬cepts are viewed somewhat differently than was previously fashionable. Specifically, in general equilibrium models, the concepts of supply and demand are rejected as central concepts in favor of a distinction be-

Jan 1, 1985

By Yongqin Zhang

A single bubble released into surfactant solution first accelerates, reaching a maximum velocity then decelerates to reach a terminal velocity. Modeling this "velocity profile" is fundamental to understanding the motion of bubbles in flotation systems. This contribution considers the terminal velocity. Modeling is by a combination of the Navier-Stokes equation for flow around the bubble and the Marangoni effect induced by surfactant on the bubble surface. Numerical simulation is shown to agree with experiment for bubbles in pure water and surfactant solutions.

Jan 1, 1999

By David J. Hatem, K. Bhattarai

Effective risk management in major subsurface projects involves ways to mitigate adverse impacts to final design and construction approaches due to changed subsurface conditions. An Early Contractor Involvement (ECI) collaborated with Observational Method will be an effective contractual tool to address risk developed due to encountering differing site conditions. Observational Method (OM) can further be supported with artificial intelligence (AI) technologies with automated data-driven decision-making features in risk mitigation and implementation of proper design and construction approaches. This paper presents collaborative applications of ECI, OM, machine learning, and risk baselining in risk management and productivity enhancement in tunneling projects.

Jun 23, 2024

By C. Roos

Traditionally within the mining industry, the main functional process flow for resource and reserve evaluation proceeds from geologists who build the geological model, to resource estimation geologists (modelers) who estimate the grades, to mining engineers who develop the mine design and schedule. The interface between these three disciplines is not always seamless. Assumptions made during one stage of the process are not always communicated down the line, even though most mining companies have procedures in place to encourage communication across the various disciplines. These procedures do not always achieve their aim due to a variety of reasons including time constraints, appropriate people not being available, or a lack of understanding of what other disciplines require, and the handover process can degenerate into one of sending computer files on to the next discipline in the process flow. This paper focuses on the interface between the resource estimation and mine engineering disciplines, and outlines some of the common assumptions made when generating a resource model and the risks that engineers may be taking when elevating cutoff grades, optimizing schedules or generating forecasts. The case studies presented focus on openpit gold deposits, but the concepts should be applicable throughout the industry. A summary of key questions and recommendations is provided.

Jan 1, 2014

By Richard D. Zigmond

In this paper, a computer program that has been developed for determining the capital and operating costs for coal preparation plants is described along with its applications. The logic of the computer program is based upon the results of a survey of existing preparation plants, operators, plant contractors, equipment manufacturers, and consulting firms. This survey provided information on plant performance, order-of-magnitude costs, and costing procedures. Additionally, an extensive cost data file for the major capital equipment in coal preparation plants has been developed. Using the washability data and the computer program outputs, the cleaning costs per million Btu can be calculated. Details about the program and its applications can be found in a report by the authors (Zigmond et al., 1979).

Jan 1, 1981

By J. A. Zimmer, M. S. Hillis, D. Moredock, J. A. Organiscak, A. B. Cecala

Enclosed cabs have been used on surface mining equipment for many years to protect equipment operators from health and safety hazards. The surface mining and quarrying process is a highly mechanized process that generates large quantities of respirable dust. Due to economic factors, more older mining equipment is being used today than in years past. With this older equipment, it is common to observe deterioration of many components on the enclosed cabs, which greatly reduce their protection effectiveness. NIOSH has performed a number of different field studies, as well as a comprehensive laboratory study, evaluating various factors and parameters regarding enclosed cabs. NIOSH has recently completed a cooperative research effort to evaluate the effectiveness of a newly designed unidirectional powered precleaner, filter and pressurizer that brings clean filtered air in at the roof of the cab and extracts all recirculated air near the floor. This research effort provided another example of the enhancement in air quality that can be achieved in an enclosed cab from the implementation of an improved filtration system and by establishing positive pressurization from increased intake air volume and sealing the cab. This testing showed a significant reduction in respirable dust levels in the enclosed cab when comparing baseline versus post-testing results. Since dust levels were similar near the roof and floor of the cab during post-testing, the unidirectional flow pattern did not appear to significantly improve the performance over the conventional design in this study.

Jan 1, 2009