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By J. K. Neathery, T. X. Li, H. Ban, J. M. Stencel, X. K. Jiang

Upgrading molybdenite ore can be technically difficult and expensive if talc is a major impurity in the ore. The layered structure of molybdenite and talc decreases the surface specificity of floatation and suppression agents, thereby making molybdenite ore beneficiation inefficient if under some wet processing methods. However, oxidic talc surfaces may be distinct from the sulfidic or oxysulfidic molybdenite surfaces, such distinction related to electron work functions and/or densities of electron donors/acceptors sites. If such differences are present, the upgrading of finely sized molybdenite ore by dry triboelectrostatic methods may hold advantages over traditional wet methods. We report on the upgrading of molybdenite ore using a laboratory-scale, drytriboelectrostatic beneficiation system. This system employs pneumatic transport conditions to tribocharge, beneficiate and collect the fine molybdenite ore particles. Using this system, two Mo ores were beneficiated under dry conditions without the addition of water or surface modifiers and additives. Beneficiation performance was dependent on the particle size of the feed ore. The surface and particulate morphology and elemental concentrations in the parent feeds and the beneficiated products were examined by scanning electron microscopy (SEM) and optical microscopy. These data, in conjunction with a complete recovery analysis, define some potential advantages of dry, triboelectrostatic beneficiation processing and provide insight into factors controlling molybdenite ore upgrading.

Jan 1, 1999

By John Turney, John Gathje, Donald Gale

The Eskay Creek deposit, located in northern British Columbia, is a high-grade gold/silver ore associated with complex polymetallic sulfides. Process development began in 1989 and continued through 1993. Because of the refractory nature of the ore, options including roasting and smelting were investigated. The selected process of pressure oxidation was the basis for basic engineering design until a re-evaluation of economics and risk indicated a preference for toll smelting. Although well proven in many industrial applications, pressure oxidation of the Eskay Creek ore dictated several innovations to solve problems associated with silver jarosite formation, preg-robbing, and high soluble copper and zinc concentrations.

Jan 1, 1995

By J. Pereyra, M. DeMarco

"INTRODUCTION It can be vital that bolted joints holding subassemblies together remain secure. Bolts should resist the loosening effects of vibrations and dynamic loads yet need to be easily removable during maintenance. When a threaded fastener is subjected to vibration, the rapid movement causes a lowering of friction against the threads and a subsequent loss of preload. The loss of preload allows the fastener to vibrate loose and possibly fall out. As the diameter of fasteners increase desired preload becomes increasingly more difficult to achieve. Input torque requirements for achieving proper bolt preload is exponentially related to any given fasteners diameter. This means that specialized tooling or bolting practices are usually required to attempt the tightening of fasteners to reach their required preload. Traditional methods can cause problems with joint integrity and do not provide consistent bolt load across the bolted surface. BOLTED CONNECTIONS A failed critical bolted joint can lead to high maintenance costs, machine downtime, and risk to worker safety. Control of the clamp load in a bolted joint is vital. However, when faced with a problem joint, it is not surprising that the design engineer will not have an answer if asked about the clamp load. Torque calculations must always be based on the existing conditions that often are vague. Unless all parameters are correct, the calculation will be unreliable. Examples of parameters are: • Thread condition of the fasteners • Hardness of contact surface • Material (steel, aluminium, copper, etc.) • Extra friction from a locking fastener • Extra friction from an adhesive • Lubricant on the thread • Type of bolt head (flanged, regular or serrated) • Surface coating of the bolt • New or reused fastener During tightening, bolts are subjected to both tensile and torsional stress. The total stress in a bolt can be calculated using the formula: Total stress = vsx2 + 3txy2 In order to maximize the desired tensile stress (sx) it is vital to minimize the torsional stress (txy). Tensile stress (clamp load) is achieved when the bolt is axially elongated. Unwanted torsional stress (twisting) in bolts arises during tightening due to thread friction. High thread friction increases torsional stress and causes yielding at lower clamp load levels than normal. A lubricant is necessary to minimize the malign torsional stress. However, many commonly used bolt-locking systems are based on increased thread friction (deformed nuts, adhesives, etc). To minimize thread friction and concurrently safely secure the joint has often incorrectly been considered impossible. The use of locking systems that increase thread friction is the single most common reason why the full capacity of bolted joints is not utilized. The following example illustrates the problem."

Jan 1, 2015

By Constance F. Acton

This paper presents an overview of -- the carbon-in-pulp process for gold and silver recovery as seen in the early 1980's. Traced back to its origins in the mid-nineteenth century the process development through the present state-of-the art is described. The process technology and equipment design are described in detail for the carbon-in-pulp process. A typical process flowsheet is given with a description of appropriate design criteria. Technical advantages and disadvantages as compared to the traditional countercurrent decantation process are discussed including some illustrative comparisons of capital and operating costs. A summary of currently operating carbon-in- pulp plants throughout the world is given with an insight into future developments in this industry.

Jan 1, 1982

By Daniel T. Brian, O&apos

Exploration targets and results in the mining industry are commonly summarized in terms of tonnage and grade. Business appraisals require, as additional information, the expected profit or loss implied by the physical summary. The early incorporation of knowledge gained through financial analysis computations can provide a means for economically resolving many common exploration and development problems. Examples of such applications from the activities of exploration planning, reconnaissance, land acquisition, and development planning are presented in this paper.

Jan 1, 1969

By G. R. Hart

The expected 1990 Clean Air legislation is providing electric utilities with a series of challenges and decisions as the utilities prepare strategies to comply with the resulting regulations. This paper addresses the strategy development of a coal-based utility --the legislation, the process used, the fuel issues, the options available, and the decisions to be made.

Jan 1, 1991

By W. C. Brice

Minnesota's mineral resources are widespread and diverse (Figure 1). In addition to the nation's largest iron and manganese reserves, the state contains sizeable vanadium, copper, and nickel resources. Recently it has been determined that the proterozoic unconformities in Minnesota have a favorable potential for uranium deposits. Finally, major potential exists in Minnesota's archean greenstone belts for gold, silver, and copper-zinc massive sulfides. Many of the state's mineral resources have been found in environmentally sensitive areas. This is not surprising since the natural forces associated with the formation of mineral deposits are often the same processes that create unusual landforms. For example, much of the state's copper-nickel is found within and adjoining the Boundary Waters Canoe Area (BWCA) and Lake Superior. The history of mineral development on the Mesabi Iron Range has also created culturally sensitive areas. Early iron mining development required the workers to live close to their jobs, and mine wastes were dumped as near the mine as possible. Few, if any, foresaw the time when taconite would be economic to mine. Therefore, it is not unusual to find valuable taconite resources located under towns and waste dumps on the Mesabi Iron Range.

Jan 1, 1980

By Jonathon M. Hanson, John F. Schatz

A combined theoretical and laboratory test program is described with the purpose of providing a useful model of the multiple radial fracturing process. A non-quantitative conceptual model is developed as the basis for detailed mathematical modeling and test planning. The model includes borehole pressurization, flaw rupture, and gas- driven fracture propagation phases. The laboratory tests are carried out in blocks of scaled rock simulant loaded to a true three-dimension stress state and with miniature propellant/explosive charges in a wellbore as the fracturing energy source. The conceptual model, fracture initiation modeling, and laboratory test setup have been completed and are described. The remaining work is ongoing

Jan 1, 1986

By Richard K. Thorpe, Francois E. Heuze

The concept of a reusable underground nuclear test facility, named HEDEF, has been under study for some time. This rock chamber would have to be engineered to sustain the repeated mechanical and thermal shocks of internal explosions. In this paper, we summarize preconceptual studies performed in support of HEDEF, including -simple dynamic calculations for internally loaded tunnels, -outline of proof-of-concept tests of proposed reinforcement, - and initial dynamic testing of reinforcement components in an underground high explosive (HE) test.

Jan 1, 1986

By V. M. Torres

An empirical correlation to detennine laboratory mill grinding time has been developed. Grinding samples to 90 ± 5# below 147 micrometers was required for a flotation testwork at Companhia Vale do Rio Doce (CVRD) Research Center. The initial samples were all below 1 mm in size with different size distributions and work indices (Wi) ranging from 13 to 23 kWh/st. Grinding curves were determined for some initial samples. A correlation was developed between percent retained on 147 micrometers at a standard time and the time required to grind each sample to the required size. This correlation was then used to grind all samples, based on the preliminary grinding model. Finally, a statistical analysis with the size distribution of all samples was performed. The success of using the correlation was confirmed and an equation was determined using the data set.

Jan 1, 1996

By M. K. Buder

Over the years, electric utilities have been faced with declining steam-coal quality, rising coal prices, and increasingly rigid and costly environmental standards. As a result, many utilities are beginning to show an interest in coal cleaning to upgrade coal by improving its heating value and reducing its sulfur content. Among the primary questions that must be answered for these electric utilities is whether the cost of coal cleaning can be offset by the potential cost savings in coal transportation and utilization in power generation. In search of at least a preliminary answer to this question, the Electric Power Research Institute (EPRI) engaged Bechtel to perform a case-by-case economic study to examine the cost effects of using cleaned versus raw coal to fuel new electric power plants. The results of two of the seven cases studied which involved western coals - one from Montana and another from Utah - are reported in this paper. Coal cleaning appeared to be a cost effective option for the Utah coal, but only marginally economical for the Montana coal. These cost results are expected to change to favor coal cleaning to a greater extent with the application of the final revised New Source Performance Standards regulating SO2 emissions just issued by the EPA. The study was based on the regulation originally proposed by the EPA under the 1977 Clean Air Act Amendments.

Jan 1, 1979

By Gerald L. Dollinger, Joseph A. Roby, David Krauter, Kenneth Deering

Three high performance TBM's equipped with large diameter (483mm) disc cutters are currently operating in Norway. This paper summarizes the design philosophy, field performance and ongoing technical development of these cutters. Included are discussions of the early problems encountered with their usage and the solutions to these problems that have been developed. Also included are discussions of the penetration rates and cutter usages observed. From this data it is concluded that high performance TBM's with large diameter cutters can produce significant improvements in both overall performance and in cutter costs under hard rock conditions.

Jan 1, 1991

By Paul E. Scheerer

Synthetically produced magnesium hydroxide serves as the precursor for much of the magnesium oxide produced in the world today. Magnesium oxide, in a variety of physical and chemically reactive forms, is a very important commodity. It is used as the main component in refractories employed in steelmaking furnaces and in many base metal refining furnaces. In the chemical industry, it serves as a raw material in the production of epsom salts, rayon acetate, oxychloride and oxysulfate cements and magnesium sulfonates. It is a minor component in fertilizers and animal feeds. It serves as the starting material for producing fused magnesia, used as an electrical insulator in electric heating elements. It is employed in the magnesium sulfite process for pulp digestion in the paper industry. Additional uses are in SO2 scrubbers, as a neutralizing agent in the tanning industry and as a component in rubber compounding. Magnesium oxide is produced not only from synthetically produced magnesium hydroxide. It is produced from natural magnesites, natural brucites, and natural and synthetic hydro-magnesites. Synthetic magnesium hydroxide, as a starting material provides more control of the chemical purity and chemical reactivity of resulting magnesium oxide products because of the uniform nature, chemical and physical, of the hydroxide that can be produced. Synthetic magnesium hydroxide is produced by precipitation of Mg (OH)2 from magnesium chloride bearing seawater or natural brines through the use of a base such as Ca(OH)2 or NaOH.

Jan 1, 1978

By Robert D. Hansen, Richard R. Klimpel

INTRODUCTION A very important factor in froth flotation is the use of surface-active chemicals to form a froth in which minerals or coals are retained, thus allowing for valuable component enrichment. In coal flotation reagents (frothers) specifically designed to provide an efficient froth are employed. It is this group of chemicals that will be the primary emphasis of this paper. Despite the importance of frothers, surprisingly little systematic scientific work has been performed with the goal of quantifying frother mechanisms and the influence of particles on froth stability. Based on direct experimental observations in both batch laboratory and continuous large-scale flotation cells, the use of a frother significantly increases first, the possibility of a particle- bubble contact, and second, the efficiency of sticking after such a contact. Thus, a major role of a frother is to significantly increase the rate of flotation. This rate modification by a surface-active agent occurs through several observable mechanisms including the formation of a froth of relatively consistent character (bubble size and bubble density) under a variety of operational conditions, an increase in the ability to disperse air in the flotation cell, a reduction in the rate of coalescence of individual bubbles in the cell, and a decrease in the rate of bubble rise to the pulp surface. It will not be the intention of this paper to exhaustively list all frother accomplishments related to research, development and use in coal flotation. Rather, the authors will attempt, based on their experience, to present a technology overview of the role of frothers in the chemistry of flotation as successfully practiced at the industrial level. A very useful framework for flotation is the concept suggested by Klimpel (1984, 1984a) of viewing flotation as a system consisting of three major components: chemistry, equipment and operating variables. This is illustrated in Figure 1. A major point of this figure is that flotation is a highly interactive system with many technical and economic combinations of component settings available to operators to achieve a given goal. Sometimes simultaneously changing various component settings will reinforce a particular attribute. Also various component settings can cancel or counteract each other if changes are not chosen wisely. Thus, coal flotation must be viewed by the plant operator as a complex system with the economic/technical optimization of a given flotation process being directly related to the operator's knowledge of how his particular flotation system behaves as a function of the major control variables he has at his disposal. Typical important component settings in coal flotation are collector dosage, frother type and dosage, air flow rate, feed rate, particle size, pulp density, and the surface oxidation conditions of the coal. Because of the above complexities, it is sometimes assumed (especially in laboratory studies) that the choice of frother type and dosage is not as crucial as some of the other factors such as collector type and dosage (e.g., Leja, 1982). Detailed plant level testing of all of the factors of Figure 1 performed in recent years, Klimpel (1980, 1980a, 1982, 1984, 1984a), Hansen (19861, Klimpel, Hansen and Meyer (1982), simply do not support this assumption. The above testing has shown rather clearly that certain frother chemical structures consistently exhibit predictable performance characteristics in both mineral and coal flotation. In addition, significant changes in both rate and recovery can be expected. In the remaining sections of this paper, the following topics will be covered: requirements of chemicals capable of use as frothers, types of chemicals used commercially as frothers, some general performance characteristics of existing commercial frothers, and recent work in developing new frother chemical structures.

Jan 1, 1986

By K. N. Han, H. C. Cho, R. Kim

"A comprehensive analysis of the effect of OH- on various cations in hydrometallurgical systems has been investigated. Cations chosen for this analysis included groups 1A and 2A, rare-earth elements and other common transition metal ions such as Cu2+, Fe2+, Fe3+, Mn2+, Ni2+, Co2+, Ag+, Cd2+, U4+, UO2 2+, Hg2+, Al3+ and Zn2+. The Newton-Raphson technique was used to calculate and plot various metal species over a wide range of pH. This study has clearly shown that by adjusting the concentration of OH-, the separation of Fe from Mn, U from V, Ce and Eu from other rare-earth elements, and In from Sn is possible. The effects of hydrated metal ions on the separation and removal of various metals from each other under various conditions is discussed.IntroductionThe primary purpose of hydrometallurgical processing is to extract, remove and purify various metals from diverse sources. Hydrometallurgists are frequently preoccupied by the extraction of cations in metallic form, but overlook the important role anions play in such processes. A proper choice of anions can determine the fate of successful extraction, removal and purification of metals (Esmaeili et al., 2005; Brbooti et al., 2011; Wei et al., 2005; Jeppesen et al., 2005; Al-Tarazi et al., 2004), and also separation (Farha et al., 2011; Sevenich and Fritz, 1983; Rashid, 1974) of cations from various solutions.In this study, the authors have examined some of the effects that anions play in various solutions. The anion considered in this study was the first hydroxide, OH-. Other anions, such as Cl-, Br-, I-, and CN-, will be dealt with in the second part of the series of two papers."

Jan 1, 2015

By Y. H. Kim

A simulation procedure has been developed that realistically portrays aggregate growth and disintegration for particular types of floc structures in water and wastewater treatment processes. The procedure requires local dissipation rates and specification of an interaction distance between colliding particles. A principal difficulty encountered in polymer flocculation, however, arises from changes in conformation of adsorbed macromolecules. Therefore, in systems where polymer flocculation occurs by bridging, dynamic changes in the particle size distribution depend upon the interaction of nonlinear. stochastic hydrodynamics with particles whose growth results from a number of concurrent and sequential random processes.

Jan 1, 1988

By A. R. MacPherson

The procedure to arrive at an energy efficient autogenous grinding plant is carried out in the following steps: First Step - Determine power requirements to grind a particular ore. This work carried out on small samples ground in a 450 mm diameter Aerofall Hill and the results are checked against a standard Bond Index test. Second Step - A bulk sample from the ore zone is ground in a 1.8 m diameter pilot mill. This work is carried on until the power objectives as indicated from the first step have been realized. Third Step - Correlate the pilot mill data, with the data from the numerous samples ground in the small 450 mm mill and arrive at design criteria for the commercial plant. Ensure commercial mill design will be suitable to obtain similar results as those obtained in the pilot mill.

Jan 1, 1981

By Randall E. Hughes, John F. Burst

This chapter describes the nature and occurrence of the principal clay minerals that are used as ceramic raw materials, explains how these raw materials are used to produce finished goods, and summarizes positive and negative trends that will affect future demand for raw materials and products in the ceramic industry. The term ceramics was derived from the ancient Greek keramikos (a clay jar). A ceramic product is a material that has been fired to at least 468.3°C (Mitchell, 1983). In addition to being one of our earliest manufacturing and construction materials, ceramic products are among the earliest records of civilization. The enduring significance of ceramics is shown by the fact that, even today, the manufacture of whitewares, brick and related red-fired wares, refractories, and engineered ceramics continues to be a major sector of the US economy. A wide range of materials can be made into ceramic products, although relatively few earth materials make up most of the ceramics in today's markets (Table 1). Most ceramic products are made from clay or a related material. The long history of clay use in the ceramics industry stems from its variable and sometimes unique physical and chemical properties, as well as its ubiquitous occurrence and relatively low cost. Clay is important to ceramics because of its plasticity, moldability and filterability, chemical content, color. refractoriness, solubility. corrosion resistance, electrical properties, and other properties that result from the essentially two dimensional morphology of the individual clay mineral platelets. Because of their basic relationships to the chemical and physical properties of clays, the chemical and mineralogical content have been the subject of continuous studies over the past few decades. Advances in knowledge about the chemical, mineralogical, and physical properties of clays are responsible for most of the advances in processing. The need to remove off-colored contaminants, minerals with low melting points, and soluble salts has resulted in beneficiation by wet processing methods such as water washing. Water washing is restricted to kaolins, although low cost methods of water washing have been extended more recently to ball clays in Europe. High intensity magnetic filtration and flotation technologies have noticeably improved the quality of kaolins and broadly expanded their use in the ceramics industry. In addition to products for construction (e.g., brick, tile, sewer pipe, field drain pipe, cement, fiberglass, roof granules, and paint) and manufacturing (e.g., refractories, kiln furniture, sanitary ware, pottery, and dinnerware), clays are used in calcined form as ceramic fillers, carriers, extenders, and grogs. Ceramics suppliers are under economic pressure in several of these product areas. Manufacture of refractories in America has declined as steel production has decreased. Similarly, dinnerware and tile production have declined because of foreign competition. Fortunately, new uses for clays,

Jan 1, 1994

Atlas Copco, a leading supplier of equipment and services to the mining and construction industries, is consistently pursuing its strategy to offer the most productive and economical solutions by continuously offering new innovative products. These are in most cases developed and tested in close cooperation with demanding end users before Being officially launched on the international market. The demands for higher productivity and improved overall economy have resulted in systems for automation of the drilling cycle and also tools for integrating the Drilling equipment to the production control system used by the customer. In terms of improving the blasted material quality, Atlas Copco has placed emphasis on hole straightness and the need for hole logging and positioning. By applying state of the art Technology to today?s computerized drilling rigs, major steps in improving overall drilling and blasting performance have been achieved. This paper will give some examples derived from the latest development of solutions for the Rotary drilling product line.

Jan 1, 2010

By C. P. Davenport

At the risk of belaboring certain facts which have so often been stated in the past, please bear with me while I set the stage. What are the projected electrical power needs of the nation and of the Northwest during the next 15 to 20 years? No one who has researched the subject over its historical past has reached a substantially different result than the following simple conclusion: electrical power requirements are doubling every decade. There are some who question the necessity of a power company's need to install capacity every ten years equal to what it has done during its entire previous history; there are even those who would argue that such growth should be arbitrarily curtailed. We are not here today to decide who should have light, heat, jobs and comfort, for we know that a power company must, by law, meet its responsibilities of providing the energy the public expects when the switch is thrown. The Northwest area (the States of Oregon and Washington), for which I speak, has the same case history of electrical power need as does the nation as a whole, and the requirement boils down to roughly an average of a million kilowatts of new capacity each year over the next ten years and we can estimate an average two million kilowatts per year in the 1980's. This is simple arithmetic, but the problems of meeting this exhausting schedule are a real challenge. The subject to which I address this paper is the role that Western Coal will play in the 6 billion dollar investment in these power generation stations. That 6 billion dollar figure represents today's dollar value and you may wish to apply your own escalation - frankly, I haven't the courage.

Jan 1, 1972