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By Michael A. Redfearn

The use of nitrogen in molybdenite flotation circuits is a relatively new concept utilized by only a few mines around the world. This paper briefly discusses circuit chemistry and the reason for its success. It follows the entire testing process which resulted in a sodium hydro-sulphide dosage reduction from 18.5 to 4.4 lbs/ ton (9250 to 2200 g/t) through to the final installation of an inert gas generator which will produce reagent savings in excess of one million dollars annually. A description of the various types of nitrogen generators commercially available is included.

Jan 1, 1983

The disadvantages of the present zinc producing methods, RLE and ISP, are high energy consumption and environmental problems. Therefore, efforts have been directed in Outokumpu Zinc towards the development of alternate routes. One interesting pyrometallurgical process to produce zinc is to inject zinc calcine together with a solid reductant into molten iron, saturated with carbon. This process has been studied by thermodynamic calculations, laboratory tests and mini-pilot test runs at Outokumpu Research Oy, Pori, Finland. The results of these tests are presented and discussed in this paper. The mini-pilot tests demonstrated that over 97 per cent evaporation of the zinc was possible using a reactive coal dust as the reducing agent. The recovery of zinc in the metal phase was at best 88 per cent of input zinc, but only part reported in molten lead in the splash condenser. The final metallic zinc contained at best 98 per cent Zn, the main impurities being dissolved lead and coal carried along with the flue dusts.

Jan 1, 1993

By J. A. Beesley

This paper reviews contemporary international law concerning the seabed, current developments in the United Nations on the seabed, and the main outstanding problems. It emphasizes the importance that the Canadian government attaches to this area.

Jan 1, 1969

By Eugie Kabwe

Rock bolts are components of tunnel support structures and their efficacy in reinforcement requires the appropriate estimation of the bolt pre-tension. However, cases of ineffective rock bolt application due to loosening are common which leads to the potential failure of the support structures, thus negatively affecting the tunnel stability. The effective employment of pre-tensioned bolt within support structures requires an appropriate installation tension as a result of sufficient bolt head/nut pre-load. Henceforth, this paper presents a load indicator washer (LIW) capable of withstanding assigned static loading as well as provides an appropriate pre-tension. The different LIW breadths are numerically analysed in the finite element code (ABAQUS) to estimate deformation when a designated 60-kN pre-load is applied. The numerical simulation employs a bi-linear isotropic hardening constitutive law governed by the von Mises yield criterion. The simulation also considers the nominal temperature of the nutLIW-rock bolt connection. Therefore, a long-term relaxation effect on bolt pre-tension as a result of stress relaxation is neglected. The compressive force required to achieve the LIW-predetermined deformation is the bolt pre-tension. It is drawn from the simulation results that the 1.5-, 2.0-, 3.0-, 3.5-, and 4.0-mm-thick LIWs are completely flattened when subjected to 28-, 42.5-, 65-, 76-, and 88-kN pre-load respectively.

By Bryant Fitch

This paper will review thickening theory, from the ( ) of the practicing engineer, with particular emphasis on ( ) uncertainty or disagreement. It will attempt to outline broadly what we know and what we don't know. This should serve two purpose First, it will warn the process engineer where he might get into trouble. At least it will alert him to the risk involved in uncritically accepting any of the recommended design procedures. Second, it will identify for researchers some areas in which further work might be fruitful. Not too many years ago there would have been little to write on such a subject. We had been designing thickeners for decades, using the classic Coe and Clevenger procedure. As far as we were generally aware, they all turned out to be about the right size. And so if there was anything we didn't know, It certainly wasn't hurting us much. Today we know better. While it is true that in most cases units designed by the Coe and Clevenger procedure (1) will perform satisfactorily, we now know of cases in which they don't. And during the past few years there have been many developments and advances in basic thickening theory. So there is now a lot more room for disagreement, and a whole lot more to be uncertain about. What is "thickening" "Thickening" means different things to different people. For this paper we define it to mean sedimentation behavior characterized by line settling. Solids subside with a clear line of demarcation between settling solids and supernatant. Although the supernatant will usually be clear, in some cases it may be turbid. Line settling must entail that all particles just below the pulp-supernatant interface have the same subsidence rate, so that

Jan 1, 1971

By B. E. Davis

A technique was devised by the Bureau of Nines to recover coarse (plus 1.7 m) North Carolina phosphate now discarded as waste. Concentration utilizes the difference in particle sphericity between the relatively flat calcite and the rounded phosphate pebbles. Sizing, treatment in a continuous hydraulic classification system, and grinding upgraded a 17.0-pct-P205 reject to 24.5 pct P205 with a phosphate recovery of 63 pct.

Jan 1, 1985

By James R. Miller

Recent experience over extensive areas of the Basin and Range Province has demonstrated the importance of the basin's (valley's) geology and geomorphology in locating large quantities of good-quality aggregate. First, a geologic map depicting basic geomorphic-geologic units in a valley is made in the office from aerial photography. Next, derivative maps are made from geologic maps and field-derived information such as parent rock type, source area and depositional environment, relationship to adjacent deposits, and Quaternary geologic history. Studying the derivative maps leads to selection of test sites for potential deposits of high-quality aggregates. Subsequent field studies provide more detailed information about geologic processes and samples for laboratory testing. Combining all information allows the characterization of aggregate potential of very large areas. Favorable areas can be further tested. This phased approach has proven to be cost effective. The methodology used in mapping and characterizing basinfill deposits is applicable over much of the western United States. Map units were developed by focusing on the predominate geomorphic process, grain size, cementation, and relative age. The resulting functional map units are of use to engineers and planners. This study led to many conclusions, including the fact that the best quality basinfill aggregates are found in selected alluvial fan deposits and Pleistocene lakeshore deposits. The best quality aggregates are derived from Paleozoic carbonate and quartzitic parent materials that can also provide high-quality crushed-rock aggregates.

Jan 1, 1987

By S B. Richardson, D Mead, N T. Moxon

The use of air-decks to reduce explosive costs has become very topical in recent years. The majority of the research in this area has been arried out between the Soviet Union where reductions in explosive consumption of between 10-30% have been claimed with apparent benefits being gained in both fragmentation and movement. Work carried out by the University of Maryland using thick plexiglass blocks has supported these findings and indicated that air-decks in measetbe duration of action of the shock wave on the surrounding material by a factor of 2 to 5 (see Figure 1). Although the fracture network resulting from this mechanism is not as intense as that produced adjacent to the explosive charge it does appear to act over a larger volume of material. Although the mechanism attributed to air-decking has been studied in some detail the effect of this mechanism on the size distribution of material produced during a blast does not appear tot have attracted much attention.

Jan 1, 1991

By B. Singh

The use of wire ropes has already been tried in a few countries for roof support In mines. But the use of scrap wire ropes, as a method of support on extensive scale has not been reported from anywhere except India. Extensive trials using freshly discarded wire ropes for roof support were undertaken both in the laboratory and field. In laboratory, model beams supported with different reinforcing techniques were tested to evaluate their comparative load bearing capacity vis-a-vis reinforcing factor. Among all the tests, the model supported with wire rope system at 60° angle in combination with two supplementary vertical bolts offered the best result 1.e. about 95% reinforcement. It also accepted post fracture loading of the beam. In statical analysis too, the best result could be obtained with the rope installed across the gallery at 60° angle. All these findings are in conformity with the field observations obtained during roof stitching practices in coal mines. Of late, roof stitching, an effective and economical method of roof support developed at CMRS, India in 1972, found wide application in over 200 coal mines. In this method, a freshly discarded wire rope is grouted across a gallery in two inclined drill holes supplemented with two middle vertical roof bolts at every 1.0 to 1.2 m interval along the gallery. It is tensioned against the roof using wooden sleepers and thus, the whole system functions like a roof truss.

Jan 1, 1990

By T. Yamazaki, T. Goto, R. Arai, N. Nakatani

The importance of cobalt-rich manganese crusts on the Pacific seamounts for possible future rare metal sources has been recognized these 30 years. The thin layer-type coverage and the micro-topographic undulation of basement affect not only the excavation efficiency but also the economy of mining venture. Because of these distribution characteristics, no economic feasibility has been recognized through the past economic analyses. On the basis of a recent geological study about seamount rocks, a possibility of by-product substrate recovery for phosphorous supply with cobalt-rich manganese crust mining has been highlighted. In the mining model, the substrate rocks are utilized as phosphates for agricultural and chemical usages. Under some preliminary technical and economic assumptions, the possibility of cobalt-rich manganese crust mining venture is examined. The results show a better economy of the venture including the substrate rock usage for phosphorous supply. Introduction Cobalt-rich Manganese Crusts and the Economic Feasibility Cobalt-rich manganese crusts on the Pacific seamounts received attention as potential sources for strategic metals such as Co, Ni, Cu, and Mn, due to their vast distribution and higher cobalt concentration than manganese nodules (Cronan, 1980; Halbach, 1982; Manheim, 1986). In the earlier stage, the geological distribution characteristics were reported (Cronan, 1984; Clark et al., 1984; Misawa et al., 1987; Pichocki and Hoffert, 1987) and a systematic feasibility of the mining was studied (Hawaii DPED, 1987).

Jan 1, 2018

By Kevin Vander Tuig, Tim O’Rourke, Rick Vincent, Doug Lopata, Kellie Rotunno, Dan Dobbels

"The Northeast Ohio Regional Sewer District (NEORSD) was required under the Federal Clean Water Act and U.S. Environmental Protection Agency’s (U.S. EPA) Combined Sewer Overflow (CSO) Control Policy to develop a Long Term Control Plan (LTCP) to reduce or eliminate overflows from its permitted CSO outfalls. The LTCP was completed in 2002. Key components of the plan include: 26 miles (42 km) of deep storage and conveyance tunnels providing a total CSO storage volume of 325 million gallons (MG) (1.2 billion liters); over 30 miles (48 km) of consolidation sewers to route CSO control flows to the tunnels; and associated diversion/inflow control structures and drop shafts. Final design and construction of the initial phases of the LTCP are completed or underway. Advanced planning of the final phases began in April 2013. This paper summarizes this advanced planning process and, specifically, how hydraulic performance and tunnel design and construction considerations were balanced to eliminate unnecessary projects and shafts, reduce implementation risks, and reduce program costs by approximately $650 million. BACKGROUND The Northeast Ohio Regional Sewer District (District) serves an area of approximately 350 square miles (SM) (907 km2), including combined (81 SM; [210 km2]) and separate (269 SM [697 km2]) sewer systems that discharge to three wastewater treatment plants in the greater Cleveland area. The service area, shown in Figure 1, is divided into three districts—Easterly, Westerly, and Southerly—each having its own interceptor system and treatment plant, ranging in wet weather treatment capacities from 100 to 735 million gallons per day (MGD) (378.5 million to 2.8 billion L/day). The system includes 124 permitted combined sewer overflow (CSO) outfalls overflowing into the region’s tributary streams, Cuyahoga River, and Lake Erie."

Jan 1, 2016

By Alex Alves

No cenário econômico atual as organizações estão focadas na maximização de resultados para manter a competitividade e posicionamento frente aos acionistas. Isso exige uma busca minuciosa de alternativas logísticas que envolvem toda a cadeia produtiva, desde a aquisição com o menor custo até uma gestão racional dos recursos materiais, consequentemente se exige cada vez mais controle nos processos. Nesse sentido, destaca-se a atividade de recebimento e inspeção de materiais como uma função da administração de materiais, que tem a missão de garantir o abastecimento dos recursos materiais ao usuário na qualidade e tempo necessário. O presente trabalho tem por objetivo apresentar a sistemática de recebimento, controle e liberação de materiais da Companhia Siderúrgica Nacional, partindo de técnicas de recebimento de materiais e inspeção de qualidade, controle de processo através do SAP, lay-out e fluxos para melhoria da qualidade e produtividade do armazém central de recebimento, garantindo a melhoria contínua no processo e níveis de serviço no atendimento ao usuário.

Jul 29, 2018

By C. H. Jacoby

Since salt, sodium chloride, is an essential mineral to animals and humans alike, the delineation of the salt deposits of the world has been continuous from prehistoric times. As man explores deeper into the crust of the earth, particularly in search of petroleum, numerous new deposits of salt have been recorded. This paper deals with the factors that equate the current economic value of a salt deposit. The value of a salt deposit is not only determined by the chemical purity of the sodium chloride, but also the method of extraction to be used, the use of the product, and/or the use of the deposit. Salt is basically an inexpensive industrial commodity where large tonnages must be available to conduct a successful mining operation. Therefore, not only must the deposit contain these large tonnages, but also it must be accessible and transported as low cost freight to a large market. The geological environmental conditions surrounding the deposit must be such that it will be conducive to low cost mining operations. These conditions include not only the depth, size, shape, and internal structure of the deposit, but also the characteristics and extent of the overlying ground water.

Jan 1, 1973

By T. W. Camm

The Bureau of Mines conducts studies of the economic impacts of regulations on federal lands. These studies are part of the Bureau Potential Supply Analysis (PSA) program. To meet the needs of these studies, a methodology was developed to estimate operating and capital costs for a mineral deposit given its tonnage, grade, and depth. The format for the cost models in this study was developed at the Bureau's Western Field Operations Center (WFOC), Spokane, W. A., for studies of known and undiscovered resources on Federal lands. These cost models are described in a Bureau publication by Camm (1991).

Jan 1, 1993

By Robert Glass Cleland

THE MEMBERS of the Phelps-Dodge, Phelps-James co- partnership differed widely from one another in certain aspects of temperament and personality; but in one thing Anson Phelps, William Dodge, and Daniel James were fundamentally alike. They were all bred in the English Puritan tradition. Their creed, moreover, was the stern, militant, uncompromising creed of John Calvin and John Knox. The present generation, harshly intolerant of such a creed, has little understanding of the authority it exercised on the thinking and conduct of its adherents or of the contributions that those same adherents made to human welfare and social progress. The men who accepted its authority "were characterized by a blend of strong individualism and an equally strong sense of social duty, and they submitted their own souls to the same searching scrutiny that they applied to their business ledgers." To all three of the immediate founders of Phelps Dodge, their religion was the most real and important thing in life. It was with them day and night, in joy and sorrow, in loss and prosperity, in their most trivial personal affairs, in business transactions of the greatest moment. It was with

Jan 1, 1952

By Jan Drzymala, Przemyslaw B. Kowalczuk

"Flotation is possible when the forces operating between a bubble and the attached particle are properly balanced. There are many forces operating in the bubble-particle aggregate. The magnitude, location and direction of the forces depend on the type of process. The simplest arrangement in flotation is when a spherical bubble is attached to a spherical particle and both are immersed in water. In such a system there are four essential forces which shape the stability of the bubble-particle aggregate. They are excess pressure and interfacial solid/liquid, solid/gas and liquid/gas forces. A proper analysis and balance of the size, location and direction of these four principal forces lead to a general equation delineating the stability of the spherical particle–attached bubble system. Specific cross sections of the system and solution of the general equation lead to different relationships including the Young formula as well as the well-known geometrical relation between contact angle, particle and bubble radiuses. The arrangement of forces in the proposed graphical representation of the Young law is different from that presently used in literature for a bubble attached to an unmovable solid particle. Many real solid/liquid/gas systems are more complex due to the presence of additional forces which change the regular curvature of the liquid/gas interface leading to advancing and receding contact angles.INTRODUCTIONThere are numerous papers (Athukorallage, Aulisa, Iyer & Zhang, 2015; Chau, Bruckard, Koh & Nguyen, 2009; Drzymala, 1994; Lubarda, 2012; Pellicer, Manzanares & Mafe, 1995; Wang, Cui, Zhou, Xu, Sun, & Zhu, 2014; Young, 1804) and books (Davies & Rideal, 1963; Defay & Prigogine, 1966; Lee, 2013; Lyklema, 2000) dealing with the solid/liquid/gas system. Many of them concern the three involved phases having the shape of a sphere or spherical cap and the formed contact angle. The contact angle is usually measured through the liquid phase and can be either smaller or greater than 90o. The essential part of these publications is a graphical representation of the system with the Young equation shown as a result of balance of only three forces that is the excess Gibbs (or Helmholz) free energy per unit area of the three involved interfaces (Davies & Rideal, 1963; Defay & Prigogine, 1966; Israelachvili, 1985) (Figs. 1a-c). The Young equation, when the gravity force/buoyancy is neglected, is:"

Jan 1, 2016

By T. N. Moore, E. M. De Souza

J. Dasher Regarding the March 1991 ME technical paper by De Souza and Moore: For more than a decade since my February 1981 article on how to use modern metric, which SME-AIME had decided to do, I have monthly pointed out metric errors to the editors. In part, I do this because there has been no action to allow editors to fix figures and tables or to allow them to require authors to do so. The latest resulting atrocity provokes this discussion of vibrating drill handle units being stated in decibels. Reply by T. Moore We have read the discussion of our paper by Mr. Dasher. Our reaction is one of surprise and incredulity. It would seem that Mr. Dasher takes exception to the use of the decibel scale to present vibration acceleration data, and the use of hertz as the unit for frequency. The basis for his objection to the decibel appears to be that it has no dimensions (which somehow invalidates its use), that it is "non-metric" and, finally, that it is parochial (of limited or narrow scope). His objection to the use of the term hertz is not stated, but we will assume that it stands condemned as "non-metric" and parochial. Obviously we disagree with Mr. Dasher's views and will now outline our reasons. Although the decibel scale originates from transmission line theory and telephone engineering, it is also at present widely used, not only in the fields of electronic engineering and acoustics, but also in the area of vibration. The original definition of the decibel (dB) was based on power ratios: dB = 10 log 10(W/W0) where Wo is a reference power. However, as the power measured across a given impedance is related to the square of the force acting upon this impedance, Z, a more commonly used definition is: [2 dB = 10 logF /Z) = 20 log F/F 10\ F0 2 /Z(0)] where F and F0 are the r.m.s. values of the forces. Now, if the measurements are related to one and the same impedance, the decibel notation in the form of 20log10(X/Xo) may be used as a convenient relative magnitude scale for a variety of quantities. Thus, X may, for instance, be an r.m.s. displacement, velocity or acceleration. It is only required that XD always be a reference quantity of the same type as X. That is, when X represents an acceleration, then X0 represents a reference acceleration. This is the formulation used in our paper. This was not an arbitrary choice on our behalf but reflects standard practice as specified in the International Standard ISO 5349-1986(E) Mechanical Vibration - Guidelines for the Measurement and the Assessment of Human Despite the metric prefix, the decibel is a parochial expression of (l) the logarithmic ratio of the loudness of a sound to what is normally audible or (2) the logarithmic ratio of two power signals in radio or electronics. A decibel is not a unit, much less an SI, unit and has nothing whatsoever to do with the acceleration of drill handles. Stating that m/s2 (acceleration) is decibels is without reason. Whoever reviewed this material should not have allowed publication of figures of dB and H.[ ] Exposure to Hand-Transmitted Vibration. This was clearly stated in the "measurement protocol" section of our paper. This quantity is then referred to as the acceleration level and is expressed in dB. We may have inadvertently caused some confusion when we simply used the term acceleration to refer to acceleration level on our diagrams. At the time, we felt the use of dB or m/s2 would make the context clear to the reader. For any confusion this decision may have engendered, we apologize. Since the decibel expresses the ratio of two like quantities, it certainly has no dimensions. It is, however, common practice to treat "decibel" as a unit as, for example, in the sentence, "The acceleration level measured at the operator's hand was 160 dB." The expression of measured quantities in dimensionless form is not inherently unacceptable. In fact, in many areas of engineering it is standard practice (consider the use of Reynolds Number, Nusselt Number, etc.). The fact that the decibel is a dimensionless quantity makes the question of whether it is a SI unit nonsensical. However, it is valid to insist that the dimensional quantities used to obtain the decibel values be expressed in SI units. A careful reading of our paper will make it clear that the measured acceleration was, in fact, expressed in units of m/s2 as was the reference acceleration (l x 10-6 m/S2). These are the accepted derived SI units for acceleration. See, for example, the standard ASTM E380-89a Standard Practice for Use of the International System of Units (SI) (The Modernized Metric System). Concerning Mr. Dasher's implication that hertz (Hz) is an unacceptable unit of measure for frequency, we would again refer him to the standard ASTM E380-89a. Here, he will find (section 2.4.2) that hertz is an accepted "special name" for the derived SI units-1. This is in keeping with numerous other international standards including ISO 5349-1986(E) to which we referred in our paper. In conclusion, we agree with Mr. Dasher on the desirability of expressing measurements in modern SI units. But we would remind him that the standards that define the use of these units, and the accepted means of presenting measured data, are in a continual state of refinement. It is, therefore, incumbent upon him to keep abreast of these changes if he wishes to constructively critique the work of others.[ ]

Jan 1, 1992

By Chris Jobes, Alan Mayton, N. Kumar Kittusamy, Dean Ambrose

NIOSH researchers conducted a study to compare seat designs on underground coal mine haulage vehicles. The objective of the study was to support prior findings that NIOSH-designed seats, which incorporated ergonomic design features (e.g., viscoelastic foam padding and low-back support), are improved designs. Based on measured levels of vehicle jarring/jolting and perceived discomfort, researchers evaluated four different designs - two in-use and two NIOSH-developed, ergonomic designs. Researchers collected data using a short questionnaire, a linear, visual analog scale, and accelerometers with a data recorder. Results showed that vehicle operators favored the NIOSH seats with added adjustability, low-back support, and improved seat padding over the existing seats. In addition, the measurements indicated all NIOSH seats performed better than the existing seat, under the no-load (worse of two) conditions, in reducing peak acceleration, crest factor, and RMS acceleration. The authors summarize the data collected and operator preferences for seat designs and different foam padding arrangements.

By Henry Fay

THE CHAIRMAN (ALBERT SAUVEUR, Cambridge, Mass.).-In forcing us to face and to discuss the important question of erosion of steel guns, Prof. Fay is performing a public service. His investigation has been fruitful and his results illuminating and suggestive. It is not in a spirit of adverse criticism, therefore, that I venture a few remarks suggested by his paper, but rather to add my mite to the discussion in the hope that it may not be entirely without value. Prof. Fay considers it conclusively demonstrated that the hard layers forming in the inside of guns of large calibers after they have been fired a number of times consist of martensite. Still, he admits that he never was able to detect in the hard layers the structural characteristics of martensite. This leads him to conceive the existence of amorphous martensite. We may well hesitate before accepting this theory on the strength of the evidence offered. Martensite, as we know it, is essentially a crystalline condition assumed by a close association of iron and carbon, possibly if not probably of the nature of a solid solution. Lacking this crystalline character we are hardly justified in calling it martensite on the ground, merely, of its being very hard.

Jan 4, 1917

By R J. Norris, D J. MacKenzie

Gold-bearing veins have formed at a wide range of depths throughout the uplift history of the Otago Schist. The earliest gold mineralisation occurred during the later stages of Mesozoic metamorphism. This mineralisation was characterised by diffuse wall rock alteration with greenschist facies metamorphic or retrograde metamorphic mineral assemblages, and gold occurs in this altered rock. Quartz veins formed in .steeply dipping extensional fractures associated with this mineralisation type strike north to northeast. The Macraes mine exploits this deposit type. The present northwest strike of the mineralised zone at Macraes is a result of post-mineralisation deformation of the schistosity-parallel mineralised shear zone which hosts northeast striking extensional veins. This combination of schistosity-parallel shear zone and steeply dipping northeast striking veins may exist elsewhere in Otago, and this deposit type is most prospective. Steeply dipping quartz veins formed during post-metamorphic un-roofing of the Otago Schist strike northwest to west and occur as clusters of near-parallel structures in east and central Otago. These veins consist mainly of massive quartz, although some prismatic quartz occurs also. Breccia fragments in veins are common and these are generally silicified, with some gold. Wall rock alteration is negligible, and vein margins are sharp. A set of middle Tertiary veins occurs in northwest Otago. Most of these also strike northwest and dip steeply, but some strike northeast. These veins contain abundant ankeritic carbonate as well as quartz. The carbonate pervades adjacent wall rock as veinlets, but gold mineralisation is confined to veins. Quartz is commonly prismatic and vuggy, and contains gold, which is commonly coarse grained especially in silicified breccia zones. Associated veins contain stibnite. This vein type formed close to the paleosurface (>2 km). Mineralised veins in Marlborough currently strike northwest, but these have been rotated from northeast strike during Alpine Fault displacement of Marlborough from Otago. Some of these veins were formed under late metamorphic conditions and are similar to the north to northeast striking veins in Otago. As in Otago, this type should be considered to be most prospective if they have associated schistosity-parallel shears.

Jan 1, 2000