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By S. C. Tadolini, P. Mills

"INTRODUCTION This research produced a shotcrete formulation that extends beyond stabilization and can be used to restore the structural integrity of damaged infrastructure. The primary challenge was to develop a shotcrete or gunite with structural strength within a few minutes to prevent parasitic loading and allow ingress into damaged structures within a few minutes of the mix formulation being applied. This also applies to mining conditions where rapid support of progressive failures can minimize failure. An additional benefit was the discovery that the product had extremely high adhesion properties in addition to high flexural strengths. The approach to product design was the development of “single bag” dry mixes that are entirely self-contained, can be rapidly transported anywhere in the field or underground, and be deployed using simple equipment. Dry mix eliminates issues relevant to high shear water mixing, as water is added in the form of a mist at the point of delivery; thus low W/C can be achieved. However, as there is no onsite powder mixing, the product must have a high degree of inherent homogeneity. A commercial version of this material is currently offered as Minova’s Tekcrete Fast® product which has been successfully deployed in the mining industry and is currently being used in civil, construction and tunneling operations. The material can rapidly stabilize unstable ground in metal/nonmetal and coal mines. This paper described the technology development, product testing results and applications in mining and civil applications. BACKGROUND The original development of this product was to complete rapid stabilization of shock damaged structures, which falls outside the purview of normal construction and mining practices, due to the critical time issue and the nature of the damaged structure. The stabilization of damaged structures requires materials and equipment that can be rapidly deployed to place materials that have very rapid strength development. These materials need to be placeable at a distance to provide some degree of safety to the responders. In addition, the materials must be able to adhere to structural surfaces that have not been specially prepared and conditioned, and may also be highly fractured, dusty, wet, and quite possibly hot or extremely cold. The technology for the rapid delivery of large volumes of cementitious materials to vertical or even overhead surfaces currently exists. Pneumatic delivery (shotcreting) has been used in construction for over 100 years (American Shotcrete Association, 2014). Shotcreting has played a major role in structures like the Washington D.C. Metro subway system and been used in underground mining applications routinely to serve as part of the primary and secondary support system when used in conjunction with traditional roof bolts. Numerous rapid setting cements are commercially available. They are used for rapid repair of surfaces such as bridge decks, pavements, and commercial floors, as well as structural repairs of vertical and overhead surfaces. Few of these products are specifically marketed for use in shotcrete applications. The majority of rapid setting cements are based on, or at least contain, Portland cement as a principle component. Other components are added that help provide early strength, such as high alumina cement (HAC), organic polymers, chemical accelerators (which can also be added during concrete batching), and calcium sulfate hemihydrate (e.g. gypsum plaster) (Lea, 1971). Cementitious mortars prepared with some of these cements can achieve compressive strengths of 6.8 – 13.8 MPa (1,000-2,000 psi) within 1 hour. However, Portland cement mortar and concrete typically require many weeks of proper curing to reach significant levels of their ultimate strengths, even when used with set accelerators. Also, high early strengths require the use of large proportions of Portland cement in the concrete mix, which can lead to high heat evolutio"

Jan 1, 2017

By William W. Shriver

When the Henderson Project is completed in 1975, it will become one of the Free World's largest primary molybdenum producers. The Henderson Mine will be located approximately 50 miles west of Denver, Colorado, on the eastern slope of the Continental Divide. Ore reserves are currently estimated to be 303,000,000 tons with a grade of 0.49% MoS2. The mill and tailing area will be located approximately 14.5 miles from the mine in the Williams Fork Valley, which is on the western slope of the Continental Divide. Ore haulage from the mine to the mill will be by ten miles of underground railroad and 4.5 miles of surface railroad. The concentrator has been designed to mill 30,000 tons per day and will yield approximately 50,000,000 pounds of contained molybdenum per year. This paper is concerned with the tailing and water supply system for the Henderson Project and in particular the environmental considerations affecting their design.

Jan 1, 1970

By William F. White

It is a pleasure to have the opportunity of being here today to discuss the application of horizontal filters in the metallurgical industries. The use of horizontal type filters has been limited in metallurgical plants. However, in the recent past there have been new designs of this type equipment which greatly broaden their field of application. Through their use in many applications, important economies can be achieved over more conventional methods. The first of the modern continuous horizontal filters was initially developed by Oliver United Filters as their scroll type horizontal filter. This was an outgrowth of the old Oliver Sand Table that was limited to very coarse, free filtering pulps containing no appreciable amount of fine particles. The sand table was rather limited in application. The later continuous scroll type horizontal filter provided for a reverse air blow after discharge which reslurried the heel remaining and permitted the filtration of pulps containing finer particles. In the manufacture of phosphoric acid by the ?wet? process, the filtration of gypsum from the strong acid presented an extremely difficult filtration problem due to blinding of the filter media caused by crystallization of the soluble salts contained in the acid. A filter which allowed for continuous cloth washing was required, and this led to the development of the continuous pan type, and travelling belt type horizontal filters which provided for this need. Among the filters developed were the Prayon by Engineering and Industrial Corporation of Luxembomg for use in their phosphoric acid plants. They are one of the largest manufacturers of phosphoric acid in Europe. The Dorr-Oliver Traveling Pan Filter was also developed by Mario Giorgini, Manager of Dorr-Oliver?s Italian subsidiary, for use with the Dorr Company?s phosphoric acid process. Basically, there are four existing types of horizontal filters in commercial use at this time: The scroll discharge non-pan type, the continuous belt type (Lurgi), rotary pan type, and the traveling belt type. The construction and principle of operation of these various filters will be discussed.

Jan 1, 1958

By James Yancik

The Howe Coal Company located in Leflore County, Oklahoma is mining the Oklahoma Lower Hartshorne Coal bed which ranges in thickness from 38" to 42" and dips approximately 7 degrees to the Northeast. The Lower Hartshorne bed lies within the Hartshorne sandstone in Oklahoma but is as much as 60 feet above this sandstone formation in Arkansas. This coal bed extends throughout the Arkansas Oklahoma coal basin, which is about 50 miles wide and 180 miles long and progresses from a semi anthracite in Arkansas to a low-volatile coal in the eastern part of the Oklahoma to a high-volatile coal in the western area. The Howe Mine #1 in the eastern area is mining a low-volatile bituminous coal which has been used as metallurgical coal since the early 1900's as evidence of Bee-hive coke ovens still remain near the town Howe, a few miles northwest of the mine site. The Howe Mine is the first mine in the area to use modern mining equipment, however, numerous punch mines have been worked along the outcrop south of the mine site dating from 1900 with the last closing in 1965. The coal characteristics of the Lower Hartshorne rival the Pocahontas seam in chemistry and coking qualities. This paper will be concerned with the preparation of the coal for the Japanese steel market. The three man crew necessary to operate the plant are the operator, the helper, and the equipment operator needed to feed the raw coal hopper. An additional equipment operator is available on the day shift for coal loading and moving the clean coal to the storage pile as the area under the clean coal belt is only large enough for 1 shifts production. We are at present running the plant on a 2 shift per day basis.

Jan 1, 1969

By Arthur R. MacPherson

Este capítulo revisa las etapas que deben seguirse desde el momento de considerar la molienda autógena en el desarrollo de un nuevo depósito de mineral o en la expansión de una planta existente, hasta la compra de un molino autógeno. En este caso el término autógeno incluye: semi-autógeno, molinos de pebbles secundarios y molino de bolos (trozos), así como los sistemas de molienda autógena total. También se han incluido las alternativas por vía húmeda y seca. Antes de programar el ensayo debe decidirse cuantas muestras brutas son requeridas para calcular propiamente las posibilidades de molienda autógena del depósito. También ha de tomarse la decisión, de como y donde deben tomarse las muestras, por ejemplo: planta piloto situada en el sitio de localización de la planta o en otro lugar establecido; molienda en húmedo y/o en seco....etc. En el mismo programa del ensayo se obtendrán ciertos datos fundamentales. Los ensayos deberán incluir un trabajo suficiente. para determinar cuál de las moliendas, totalmente autógena o semi-autógena, debe utilizarse; y qué tipo produce la máxima eficacia en la potencia consumida. También, los otros datos pertinentes deben ser recolectados, como por ejemplo: potencias, tonelajes, alimentación, carga, tamaño del producto, carga circulante, etc. Si es necesaria una molienda secundaria para obtener el tamano final, la decisión de qué molienda debe emplearse (molino de pebbles o molino de bolas) puede requerirse un ensayo de trabajo adicional. Finalmente, la concentración del mineral puede jugar un papel importante en la selección del circuito y debería ser una parte del ensayo final una vez que se ha establecido la molienda. Para determinar qué tipo de molinos pueden satisfacer los requerimientos establecidos por la planta piloto, debe tomarse una escala para ciertos datos como: potencia del molino, consumo de acero, simple o doble etapa de molienda, tipo de molino secundario. Para asegurar un posterior entendimiento del depósito de mineral y sus características de molienda, deberán efectuarse algunos trabajos adicionales a pequena escala utilizando pequeñas muestras y molinos para producir unos datos comparables de molienda. También, algunos ensayos tales como medio de molienda óptimo, e índice de trabajo, deberán ser completados.

Jan 1, 1982

By M. N. Herrera

The bioleaching of mineral sulfide pulps in a bench-scale rotating drum reactor has been studied. The reactor includes horizontal paddles in the inner wall for lifting of the mineral pulp. The performance of the reactor was tested in the bioleaching of a refractory pyritic gold concentrate in the presence of pure Thiobacillus ferrooxidans strain (ATCC 19859). The concentrate was efficiently bioleached at 50% pulp density with the drum operating at 0.5 -1.0 rpm Attempts of bioleaching the concentrate at the same pulp density in conventional stirred reactor showed severe inhibition of bacterial activity. The results demonstrated that the drum reactor allows to operate at much higher pulp densities than the conventional stirred tank reactor. This behavior is explained in terms of an improvement of the bacterial activity due to a better control of the attrition of the mineral particles.

Jan 1, 1997

Teeter-bed (i.e., hindered-bed) separators are used throughout the mineral processing industry for both classification and density separation. The high capacity and sizing characteristics of these units make them ideal for feed preparation prior to coarse flotation (+0.100 mm) circuits. Teeter-bed separators are typically easy to control with two basic operating parameters including fluidization water rate and bed level. However, data show that these two parameters greatly interact with one another. Given this finding, a high-level automatic control scheme was developed and implemented on a full-scale separator. In addition, dialogue with plant operators has led to several simple changes to an already established design that improves operational and maintenance characteristics.

Jan 1, 2010

By A J. Jonaitis

The DENVER Tube Press is a simple, high pressure (1500 PSI (100 bar» filtration unit, developed for processing difficult-to-dewater materials and to produce a handleable filter cake and clear filtrate product. Lab and pilot testwork conducted in Australia on coal fines (55-70\ -35 micron (400 mesh)) have shown that total moisture contents of less than 20\ are consistently achieved in the final cake products from the Tube Press. Currently, these coal super fines are sent to waste due to uneconomical mechanical dewatering methods, which were only able to reduce total moisture levels in excess of 30%. Calculated, throughput rates for the 500 Series Tube Press exceeded 1700 kg/hr (3750 lbs/hr). Feed solids concentration requirements are between 45 and 50\ to achieve these results.

Jan 1, 1993

By Lawrence S. O’Rourke

Pricing for tantalum raw materials experienced explosive increases in the period 1978-1979, and-similar declines over 1980-1982. The causes for this are examined. Negative effects on the industry are highlighted. Analysis is provided of subsequent structural changes within the industry which minimize probability of future pricing excursions. Data on markets, sources of material, and outlines of concentration and extractive processes are reviewed. The conclusion is reached that expanded sources, future flat demand, and a broader international base of industry participants are principal forces in this restructure. Flat demand is reviewed as a function of increasing application of tantalum, but in more cost effective forms. This is driven by technical advance, notably in electronics applications.

Jan 1, 1986

By R. Y. Wan

Recent research efforts have shown have shown selective solvation extraction of a gold cyanide ion-pair complex from alkaline cyanide solution is possible with organic phosphorus esters. These alkyl phosphorus esters such as tributyl phosphate (TBP) and di-n-butyl n-butyl phosphonate (DBBP) can selectively load gold to rather high levels, even in excess of 30 gpl. However, traditional stripping techniques are not particularly effective. In this regard, gold recovery by direct electrolysis of the organic phase has been found to be an interesting possibility. Further, the rate of direct electrodeposition from the organic phase can be improved significantly by using an aqueous/organic mixture. Direct electrodeposition of sheet gold from loaded DBBP was successfully accomplished at a current density of 8x10 4 amp/cm2 and 55°C from such a two-phase mixture with the aqueous phase as the continuous phase. No appreciable degradation the DBBP was found after 5 cycles of extraction and, electrodeposition. Finally, the applicability of the process strategy for an industrial situation was demonstrated by the successful treatment of waste gold cyanide electroplating solutions.

Jan 1, 1986

By Cayo Soto

Mining activity is important for the development of humanity. This development must be understood from the Academy where it allows showing alternatives for the industry performance. Likewise, these mining companies need to improve their results. Historically, a few years ago the application of the ESG (Environmental, Social and Governance) criterion was verified, which is positioned as a factor/regulator in the design of the performance of industries in general. ESG as an integral part of the concept of sustainability serves as a tool to conceive mining without conflicts and with a reputation based on trust in the interrelation of the university, industry and society. Therefore, the academy must strive for new knowledge in a way that allows it to continue in the virtuous circle of constantly feeding it. In this context, the best mining practices are implemented in constant questioning of their activities. The scientific essence of the industry supported by the academy developed in an operational dynamic is addressed. Finally, the objective of this research work is to interrelate 3 variables: ESG, Academia, and the Mining Industry, where the transition of knowledge and the role of each variable in relation to each one can be understood. This allows for an additional understanding of mining in the future with new mental attention.

Feb 1, 2025

By J. C. Edwards, C. C. Hwang

A computational fluid dynamics (CFD) program was applied to fire spread along combustibles in a ventilated mine entry. The rate of flame spread was evaluated for the ribs and roof of a coal mine entry; timber sets; and a conveyor belt. The CFD program models char forming materials with temperature dependent thermal properties. The program solves three dimensional time dependent flow equations with a mixture fraction model for the gas phase reactions. Radiant heat exchange is evaluated for non-scattering gas. The CFD program predicted a flame spread rate of 0.0145 m / s for an actual coal mine fire in which the estimated flame spread rate was 0.0086 m / s. This overestimated flame spread rate was a possible consequence of the presence of inert materials in the mine entry’s roof and ribs. CFD fire spread rate predictions of 0.043 m / s and 0.73 m / s bounded the measured value of 0.27 m / s for fire spread along Douglas Fir timber sets in a tunnel.

Jan 1, 2006

By B. T. Dawson

In today's work world, constant changes are a fact of life. Downsizing and technological advances are two of the most prominent concerns for employers and employees alike. In this article, the author addresses some of the emotional consequences of these changes and offers a new, empowering perspective for coping with them.

Jan 1, 1998

By R. W. Smith

The electrokinetic and flotation behavior of the green alga Chlorella vulgaris was studied in the absence and presence of Pb(II), Al (III) and flotation collectors. It was found that the presence of Al (III) is necessary for good flotation of the organism whether or not Pb(II) is present when dodecylammonium chloride or sodium dodecylsulfate is used as collector. Best flotation using dodecylamine is at about pH 8 and best flotation when using sodium dodecylsulfate is at about pH 4. It appears because of the small size of the organisms that the Al (III) is necessary for flocculation to enhance bubble-cell contact and C. vulgaris removal from water. When N-dodecyl-2-aminoproprionic acid is used as collector good flotation occurs at about pH 4 without the addition of Al (III).

Jan 1, 1990

By Theodore H. Budd, Austin M. Cooney

The paper discusses the background and theories of the conditions that led to the settlement of a Lovat TBM mining in an earth pressure balance mode on a recent project in Milwaukee, Wisconsin. The settlement occurred independent of human error and caused the cost of the project to increase 50 percent. The project was mined in the highly congested downtown area in alluvial and estuarine deposits, 7.6 m below the water table with a prescribed contract requirement that precluded dewatering in deference to concern for foundations of adjacent existing buildings.

Jan 1, 1989

By James E. Lonergan

Linear goal programming is a multi-objective optimization technique where the constraints of a linear programming formulation of a problem are considered as additional objectives. The optimal solution is the one that comes closest to satisfying all the objectives. An interactive computer program was written to utilize this technique in solving the feed blending problem faced by power plants de- pendent on multiple sources of coal supply. This program determines the amount of coal from each supplier to utilize in the blend. Examples of the use of the program in both long and short term coal procurement planning scenarios are given.

Jan 1, 1984

By Q. Xu

The adsorption behavior of gold in ammoniacal solutions on to activated carbon has been studied. The gold loading capacity of the activated carbon used in the system and the recovery efficiency by the adsorption were examined. The parameters affecting the adsorption of gold on to activated carbon included temperature, agitation speed, concentration of 'cation and anion as well as that of ammonia. It was found that the maximum gold loading on activated carbon used was about 10 kg of gold per ton of carbon. The recovery of gold by the adsorption from ammoniacal solutions was dependent upon the initial gold concentration in the solution. A recovery of 98% of gold was obtained on to the activated carbon under experimental conditions after 120 hour adsorption. It was also found that the initial adsorption rate was relatively fast compared to the whole period of the adsorption. The apparent activation energy for the adsorption was measured to be 15.8 kJ/mol. It was believed that the kinetics of gold adsorption on activated carbon was controlled by pore diffusion.

Jan 1, 1995

By Fritz Kleiner, Walter Meintrup

On Nov. 4, 1981 A/S Sydvaranger's 1-kt/h (1,100-stph) wet-process, iron ore ball mill completed its first four months of uninterrupted, full-load operation in Kirkenes, Norway. This 6.5-m-diam (21-ft-diam) mill is driven by a gearless ring or wraparound 8.1-MW (10,860-hp) motor at 13.1 rpm-a first of a kind in this segment of industry. This article examines reasons for selecting this type of drive over more conventional schemes, lists specific advantages of such large mills, and describes the installation in Norway. History For almost a decade, good operating experiences have been gained with 28 gearless ring motor drives in the cement industry, driving 2.5 to 4-m-diam (8.2 to 13-ft-diam) tube mills with drive powers ranging from about 3-4 MW (4,000 - 8,000 hp). Why then did the mineral ore processing industry hesitate until 1980 to adopt this successful concept for similar applications on ball, semiautogenous, and autogenous mills? There are a number of good reasons in the eyes of conservative mill builders and operators, the most commonly cited ones are: • No operating experience in this segment of specialized industry. • More severe environmental conditions in the wet ore grinding process. • An indifferent attitude of mill builders and electric motor manufacturers towards new drive technologies. • Limited confidence in solid-state power supply systems, such as frequency converters of the required size. There have been and still are numerous problems associated with low-speed geared mill drives of any kind, especially with individual motor/gear sizes approaching or exceeding about 4 MW (5,360 hp). Every mill builder knows about them, but operators learn to accept them as inevitable. The Decision to Change Three things combined to break this technological stalemate: the courage and progressive spirit of one major iron ore processor in Scandinavia, the cooperation of three experienced manufacturers, and an unusual application problem that could not be solved by any conventional approach. The last factor was surely the decisive one, but the first one does not come as a surprise either. The Swedes near Kiruna and the Norwegians around Kirkenes are experienced ore miners and processors, and much credit goes to them for technological breakthroughs in the industry. At A/S Sydvaranger in Kirkenes, above the Polar circle at about the latitude of Alaska's northern tip, the existing grinding facilities, with a total of 14 100 to 240-t/h (110 to 264-stph) ball mills, can not be expanded. Nevertheless, to increase mill throughput, only installing a larger mill in place of an existing smaller one was a practical alternative. For this replacement, the owners set requirements that seemed impossible to meet: • The old 100-t/h (110-stph) ball mill should be replaced with a new ball mill with 10 times the rated throughput, without significantly impairing the operation of the remaining mills, and without significantly changing the mill building. • The new mill should have a variable-speed drive to ultimately optimize the grinding process by means of a closed-loop process¬computer-controlled grinding cycle, and to minimize the specific energy consumption. • Availability, efficiency, and life expectancy of all new components must be higher than those being replaced. • Inrush-current and harmonic loads on the rather weak electric supply line must be minimized to ensure safe plant operation. All old ball mills at A/S Sydvaranger are the geared type, using single synchronous and wound-rotor, slow-speed motors with ring-and-pinion gears. Operators are familiar with the limitations and problems associated with such drives, and they are aware that the following items become major concerns when drive powers are drastically increased: • Gears are subject to wear and tear, require frequent maintenance, and eventual replacement of major parts. • Gears are sensitive to misalignment, overload, and thermal distortion, limiting their useful life. • On dual or quadruple drives, load-sharing and torque oscillations between motors can be a major reason for concern. • At these speeds, ring-and-pinion gears reach their torque transmission capabilities altogether at around 4 MW (5,360 hp) per motor/pinion. To obtain the desired variable-speed performance of the new drive, the only practical and economical conventional solution would have been a frequency-controlled, low- or medium-speed dual motor drive with about 8 MW (10,720 hp) of power. This, however, was not feasible because of limited floor space. Therefore, bids were solicited for the alternative drive method, the gearless ring motor. General Considerations Why are such large mills considered? After all, one could avoid all the problems by simply staying with smaller mill unit sizes. Under competitive pressures of free markets, however, grinding efficiencies and specific energy consumption become key factors in selecting new equipment. Specific energy consumption of ball mills decreases with increas-

Jan 9, 1982

By Jennifer B. Leinart

With the signing of the North American Free Trade Agreement (NAFTA), Canada, the United States and Mexico entered into an international experiment in economics amid a cloud of controversy that still lingers. Central to the controversy are the disparities in wages that exist among workers in the signing countries. Wage surveys completed by Western Mine Engineering show the degree of disparity that exists among the mining industries of those three countries. Labor costs constitute 30% to 50% of operating costs. So these wage differences are a matter of interest to the mining industry. It is unclear how much of a factor they are in determining where companies search for and develop new mines. That depends on where minable deposits are expected to be found. However, a deposit that may not be minable in the United States or Canada may be minable in Mexico because of lower labor costs. Some adjustments are anticipated for the Mexican mining industry if and when its wages begin to approach comparability with US and Canadian wages. Table 1 combines the results of four recent surveys. It lists benchmark wages for mining job titles common to all the countries. About 220 mines are covered by the combined surveys. Canadian miners' wages, converted to US dollars, are typically 75% to 95% of US wages, while Mexican miners' wages are less than 10% of those in the United States. Table 1 also shows that wage disparities are not confined to international borders. In fact, the difference in average wages between the US coal industry and the US metal and industrial mineral industries is greater than between the Canadian and the US mining industries overall. Table 2 shows that managerial, technical and administrative salaries show similar, but less pronounced differences among the three countries. Salaried personnel at Canadian mines earn 80% to 90% as much as their US counterparts, while those in Mexico earn 20% to 30% as much. Here again, average US coal salaries exceed average salaries for the US metal and industrial mineral industries.

Jan 1, 1998

By M. Misra

The coral contaminated with plutonium at Johnston Atoll UA) was subjected to gravity and flotation separation processes at the Soil Washing Laboratory (SWL) and also at the Johnston Atoll UA) site. Tests were conducted with the contaminated coral fractions referred to as the "HP-l" ( hot particles) and the "sludge". The gravity process tested was centrifugal gravity separation and the flotation processes were conventional Denver mechanical flotation and tall column flotation. Flotation tests were conducted using both fresh and sea water. Industrial fatty acid (anionic collector) was chosen as collector to make plutonium-enriched particles hydrophobic. The use of flurosilicic acid and sodium silicate made the clean coral hydrophilic. The results show that each of the processed when tested with appropriate size fraction and operating conditions resulted in passing the success criteria. It was possible to obtain more than 80% weight of the original coral as "clean sand" having activity below the JA site "soil screening level" of 13.5 pCi/gm. The field tests spiked with plutonium particles showed remarkable success. The effect of depressants, flotation medium and the coral pretreatmentis described. Finally, a flowsheet developed by the University of Nevada, Reno to treat 8000 tons of HP-l pile presently stored at JA is presented.

Jan 1, 1996