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By R. Rodgers

The Pinto Valley concentrator of BHP Copper Inc. restarted its sulfide mining operations in September 2007 to produce copper and molybdenum concentrates. During the plant production ramp up, the copper/molybdenum circuit quickly reached the copper grade and recovery targets, but the production and quality of the molybdenum concentrate continued to be a challenge. Even though several improvements in the molybdenum circuit were completed, the final molybdenum concentrate did not meet contractual specifications. After reviewing several options to improve grade and reduce contaminants, the installation of three flotation columns were chosen. The column design and construction were done using in-house craftsmen and engineers. Ten days after commissioning, the columns successfully reached a steady operation and began producing molybdenum concentrate to the required specifications, that is, high molybdenum tenors and low copper and iron content. The Pinto Valley operations, are comprised of the Pinto Valley concentrator, the Pinto Valley dump leaching and a solvent extraction/electrowinning (SX/EW) plant. The concentrator operated from 1972 to 1998 when mining and milling operations were curtailed for economic reasons. The SX/EW plant continued operations for copper cathode production. After a cessation of mining operations of almost 10 years, Pinto Valley operations began a restart project in January 2007, to bring the mine and the concentrator back into production. Copper concentrate production started in October 2007 after refurbishing and upgrading the facilities with a new DCS system and filter plant. The daily targets of the concentrator were to treat 56.7 kt (62,500 st) of ore, produce 762 t (840 st) of copper concentrate containing 27.5 percent copper at recoveries of 86 percent and produce 2.2 t (2.5 st) of molybdenum concentrate containing more than 80 percent MoS2.

Jan 1, 2010

By R. C. Burtan

Long before the dawn of recorded history, man began to dig into the earth's crust in a never ending search for useful materials. It has been well established that prehistoric man discovered flint. "The Flintstones" were aptly named. The flintknappers of southern England and Wales still exist today in ever dwindling numbers as they seek out chunks of flint. It is a well known fact that more than half of the earth's crust is composed of silicon dioxide (SiO2), also known as silica. Silica and silica containing materials have a great many uses in modern society. However, this material is potentially extremely hazardous to our health. Centuries before the Christian Era, Hippocrates wrote of a lung disease common to those who mined in hard rock. It is obvious to us that he was describing silicosis. It is also apparent from ancient writings, that the Egyptians were aware of this malady. Dioscorides also wrote on this subject in the fifth century, B.C. It is undoubtedly the oldest and best studied of the occupational lung diseases. It was certainly described by Agricola in his "De Re Metallica" published in 1556, in which he described lung disease among hard rock miners. This publication, I'm sure, is of special interest and perhaps known to many of you in the mining community. The original document was written in Latin and was translated in 1912 by two gentlemen, Hoover and Hoover. One of these translators was Herbert L. Hoover, a former president of the United States, who made his living before his presidency as a mining engineer.

Jan 1, 1984

A comparison of gold, platinum and sulfide ion selective electrodes was made in this investigation for determination of Eh in solutions containing sulfide ions as a model system. The comparison was made in terms of the accuracy of the measured response, response time, pH dependence, and reproducibility of measurement. In addition, the sensitivity of each electrode towards changes in sulfide ion concentration was measured in terms of the change in measured Eh per decade change in concentration of sulfide ions. On the basis of a detailed investigation of the electrode processes occurring at the surface of gold and platinum electrodes, it was postulated that within the pH range investigated these electrodes respond to changes in the hydrosulfide ion, HS-, concentration in solution. In comparison, the sulfide ion selective electrode is known to respond to changes in the sulfide ion, S-, activity in solution. Although the potentials measured with gold and platinum electrodes were mixed potentials, pretreatment procedures can be used to obtain a signal suitable for process control. For control of sulfide ions in flotation pulps, the use of a gold electrode pretreated at 1.0 V with respect to a standard hydrogen electrode is recommended.

Jan 1, 1990

By Peter L. Dunn

With the advent of new high-strength magnetic materials, rare-earth magnetic separators have become more common place for processing heavy mineral sands. In many instances, rare-earth magnets have replaced conventional separators such as electromagnetic cross-belt and induced-roll type machines. This paper will present the results from a detailed test program developed to evaluate the performance of rare-earth drum and roll separators for processing heavy mineral sands. The effect of machine design parameters, such as magnetic element configuration and separator diameter, will be reviewed in light of these test results. The impact of basic operating parameters (i.e. feed rate and roll speed) on separation efficiency will also be presented.

Jan 1, 1999

By Joseph E. Worthington

Increases in the price of gold starting about five years ago, and rapid fluctuations since then, have caused a substantial popular interest in the noble metal. Gold prospecting had been at low ebb since the end of World War II in most of the United states except for a flurry of activity in Nevada occasioned by the Carlin and Cortez discoveries. The last five years, however, have seen a great awakening of interest in gold exploration as well as an opportunity for education for many explorationists in the geology and other vagueries of gold deposits. The present writers have participated over the last few years in a search for gold deposits throughout the United States. This search was greatly influenced by the geologic studies of Dr. Wm. Spence at the Haile Gold Mine in South Carolina as reported in a companion paper. Spence's studies resulted in definition of a geologic model that has proven useful in a number of other geologic environments in the united states. These programs were all carried out under the auspices of Cyprus Mines Corporation and permission by Cyprus to present these results is gratefully acknowledged. The writers, however, reserve for themselves all responsibility for the results and conclusions. The exploration program to be described began in the southeastern United States. Spence's studies provided a reasonable basis for interpreting and understanding the geology of the Haile deposit and also provided a means for predicting additional occurrences. This concept was then expanded to other gold occurrences in the Piedmont and became an effective tool for evaluating other prospects. Finally it became evident that the concept could be applied in some western gold districts. The following discussion will then include descriptions of other Piedmont examples and a few western districts that also appear to fit the pattern.

Jan 1, 1978

By Thomas M. Lynberg

WIDCO is a surface coal mine located near Centralia, Washington. The WIDCO preparation plant processes over 7 million tons of run- of-mine coal each year with a product yield averaging 72%. In the jig type preparation plant the fine refuse amounts to approximately 130 dry tons per hour of 28mesh by 0. This fine refuse material is thickened in a 160ft. diameter static thickener with the use of lime as a coagulant and organic polymer as a flocculant. Once thickened the fine refuse, which is predominately bentonitic clays, has been dewatered and disposed of using several different methods. These methods will be discussed and include vacuum disc filters, ponds, solid bowl centrifuges, belt filter presses and experiments with electrokinetic dewatering.

Jan 1, 1981

By L. R. Gremillion

Chemical and mineralogical data on 25 apatitic phosphate ores of diverse origins from commercial deposits around the world were widely variable. From 14 to 18 chemical constituents of each sample were determined, and each sample contained 4 to 10 mineral phases. Altogether there were 34 different mineral phases, many of which occurred in only one sample. The samples contained varieties of francolites, fluorapatites, and mixed hydroxyl-fluorapatites. The apatite compositions calculated from the chemical data showed that certain types of substitutions were characteristic of different apatite varieties, but every variety had some degree of substitution of (CO3)2 for (PO4)3 and the P2O5 contents of the apatites ranged from 35.1% for a North Carolina apatite to 41.9% for a Missouri apatite. In a concentrate with a grade of 32% P2O5, the North Carolina sample should contain about 8.7% gangue and the Missouri sample about 23.7% gangue. To optimize the digestion process of a phosphate are, it is necessary to consider the dissolution behavior of the different mineral phases during acidulation and the effects they may have on the chemical properties of a fertilizer intermediate. In the production of wet-process acids or superphosphates, the acidulation of certain minerals may cause foaming and formation of sludge, filtration, corrosion, and handling problems.

Jan 1, 1978

By A. E. Torma

The efficiency of Thiobacillus ferrooxidans in the desulfurization of a high-sulfur content New Mexico coal was demonstrated. The optimum condition of process variables were found to be pH = 2.3, particle size = 38 µm, pulp density 14.1% (W/V) and temperature 33.9°C. Larger scale experiments carried out with these optimum conditions resulted in coal desulfurizations above 97%, while in sterile controls this was only about 10%.- The rate of desulfurization was described with an exponential expression with respect to the effects of coal particle size. The effect of pulp density on coal desulfurization was quantified by a Monod type equation. The apparent activation and deactivation energies, the frequency factor and temperature coefficient were derived from the effects of temperature to be ?aE - 11720 cal mol-1 and A = 30.44 mol dm-3s-lin the range of 20 - 35°C; ?Ed = 43930 cal mol-1 and A = 9.82 x 10-39 mol dm-3s-1 in the range of 35 - 45°C; and Q10 = 1.94 in the range of 20 - 30°C. The thermodynamic values [(?G+, ?H+ and ?S+)] of the activated complex were calculated. The generalized second order regression equation relating the degree of biodesulfurization of coal to the leach parameters was shown to adequately predict coal desulfurization within the range of process variables studied.

Jan 1, 1987

By H. M. Brennecke

A new hydrometallurgical process has been developed to recover copper from sulfide ores. Copper is leached in a staged reactor system utilizing nitric and sulfuric acids at 105°C. Iron is removed from the pregnant liquor as a jarosite and cathode copper is electrowon directly from the purified pregnant liquor. The spent electrolyte is recycled. Nitrogen oxides evolved from the leach are reconverted to nitric acid and are also recycled. Sulfur is rejected as S°, jarosite and gypsum. The process is highly versatile and can recover precious metals, molybdenum and zinc, when these elements are present. Continuous, integrated, semi-pilot plant operations using chalcopyrite ores demonstrated 99% copper leaching and production of cathode grade copper. Economic evaluation shows that the process is competitive with pyrometallurgical and other hydrometallurgical processes.

Jan 1, 1978

By Jr. Raleigh

As part vi the development of the Coal Quality Expert (CQRN) --a computer program capable of predicting the impacts of coal quality on power plant performance, costs, and emissions control--several nationally important coals are being characterized to augment the coal quality database associated with the software. The project is sponsored by the U.S. Department of Energy and the Electric Power Research Institute (EPRI) under the Clean coal Technology Program. Since 1989, CQ Inc. (a subsidiary of EPRI) has characterized seven bituminous coals from Alabama, Illinois, Kentucky and Oklahoma and six sub-bituminous coals from the Powder River Basin (PRB) in Montana and Wyoming. Coals from the PRB region--being burned more frequently in Midwestern and southern power plants to reduce emissions of sulfur oxide compounds--can sometimes contain significant concentrations of potentially toxic elements. Although no limits were imposed on air toxics emissions from fossil-fuel fired utilities by the Clean Air Act Amendments of 1990, future regulations may be implemented at the conclusion of Federally-mandated emissions studies. One possible result is that any increased utilization of coals, including those from the PRB, may depend on the potential for removing toxic trace elements prior to combustion.

Jan 1, 1993

By Robert O. Vernon

Urban sprawl, and all its attendant problems, is upon us. In Florida, and much of the rest of the world, this has been intensified by a special problem - the coastal zone - a land of high-intensity urbanization localized where the sea and our citizens interact. Florida is blessed by a long coastline of beautiful beaches, indented by estuaries, lagoons and spring fed rivers. Rocky and sand covered islands invite habitation. A large and varied fauna and flora make recreation an avocation and work a pleasure. Accompanying these people are all the sustaining, and satellite industries that find the climate, labor, and commodity markets, cheap water transportation, and natural resources to be attractive. It is estimated that by the year 2008 a megalopolis will stretch down the Atlantic Seaboard from Georgia to encompass the Keys and extend along the Gulf to Alabama. This city will be fenced by the sea on one side and by the water management works, necessary to provide the water supply for this complex, on the other. What can we do about increasing the amount of water available for this population and decreasing the resultant wastes??? Rarely has there been tendered a more favorable opportunity for a coordinated planning and development project that will provide public access to beaches and multiple use of the coastal lands. Florida, as a peninsula swept by ocean breezes, having a largely indigenous water supply and only the beginning of the pollution of estuarine and coastal waters can cope with air, water and coastal dissipation and pollution, if we have a beginning at providing a constant water supply and at limiting pollution. This answer would appear to lie underground, where the porous limestones are interbedded with impervious fine-grained sediments and ground-water that circulates through these aquifers empty to the ocean and Gulf along the continental slopes.

Jan 1, 1969

By J. Larsson

In the pursuit of increased safety the mining industry has worked to develop systems for remote control and autonomous operation of both stationary and mobile equipment. This paper reports on a newly developed system for teleoperation and autonomous tramming of LHD (Load-Haul-Dump) mining vehicles that not only increases the safety of the operators, but also has the potential to increase productivity.

Jan 1, 2010

By S. K. Bhatt

This paper reviews major developments in continuous haulage technology for underground coal mines. Haulage systems, both in use and development, are investigated through a comprehensive literature search and visits to mines and manufacturers. The systems include flexible conveyor train, mobile conveyor, multiple-unit continuous haulage, extensible, and belt turning systems. Strengths and weaknesses of the systems are assessed in light of their operating under remote control and their application to the computer-assisted continuous mining machine being developed by the U.S. Bureau of mines. Through mining scenarios, candidate haulage systems are conceptualized to be consistent with the capabilities of the mining machine.

Jan 1, 1990

By Justin R. Patts, Andrew B. Cecala, A. KYLE LOUK, Emily J. Haas

The National Institute for Occupational Safety and Health (NIOSH) and the former U.S. Bureau ofMines (USBM) have given a significant effort over the past four decades in researching and developing engineering controls and interventions to reduce mine workers’ dust exposures during the bagging and palletizing of industrial minerals. Workers performing manual bagging and palletizing of 50- to 100-pound bags typically have some of the highest dust exposures of all workers at mining and mineral processing operations. This paper will provide an overview of available dust control technologies for bagging operations and present the findings of a recent case study that was conducted at four different industrial sand operations to identify the current types of bagging and palletizing technologies being used and to evaluate their effectiveness in reducing workers’ exposures to respirable crystalline silica dust. An evaluation will also be performed to determine if further reductions in respirable dust levels can be achieved by incorporating additional modifications or improvements into the existing technology.

Apr 3, 2020

By James S. Goff, Stephen J. Navin, Wesley W. Moulton

The White River Shale Oil Corporation (WRSOC), as agent for Phillips Petroleum Company, Sohio Shale Oil Company, and Sun Shale Oil Company, is developing a prototype oil shale facility on Federal Lease Tracts Ua and Ub, located in northeastern Utah and known as the White River Shale Project (WRSP). The Ralph M. Parsons Company (Parsons) has been retained as the design engineer/constructor for the project. This paper covers the successful pregrouting of the Bird's Nest Aquifer in conjunction with the sinking of a 9.2-m (30-ft)-diameter shaft and driving of a 3.89-m by 5.64-m (18.5-ft by 12.75-ft) decline. The Bird's Nest Aquifer derives its name from the ellipsidal solution cavities caused by leaching of random-size nacholite nodules. The sodium bicarbonate nodules occur as persistent bands within a matrix of siltstone and marlstone. The team, made up of the owner, engineer/contractor, and subcontractor successfully grouted the shaft down to an inflow of less than 0.06 lps (1 gmp) and the decline down to less than 0.12 lps (2 gpm) by injecting a total of 213.190 kg (470,000 lb) of Celtite Terraseal, 113,400 kg (250,000 lb) of limestone dust, and 41,730 kg (92,000 lb) of cement into the formation.

Jan 1, 1985

By W. Collingwood, K. V. Raj, S. Bandopadhyay

In the mining industry, computational fluid dynamics (CFD) modeling is used extensively to simulate air flow in underground mines. CFD modeling of pollutant transport in openpit mines is relatively new. Modeling the actual pit geometry of an openpit mine and the open domain is complex. The complexity is primarily due to the faceted geometry of an openpit mine with its numerous associated sharp features. Important issues that are not considered carefully at the geometry level are generally propagated to the subsequent processes. Several challenges and pitfalls are encountered in modeling pollutant transport in openpit mines. These challenges and pitfalls are related to the geometry, meshing, boundary conditions and turbulence modeling parameterization. An appropriate mesh selection is critical. A detailed discussion of the meshing of the domain of an openpit mine is presented in this paper. The selection of an appropriate turbulence model, such as kappa-epsilon (κ-ε), large eddy simulation (LES), Reynolds stress model (RSM), etc., to obtain the best possible solution is equally significant. This paper discusses the various challenges in modeling the pollutant transport process in an openpit and some of the approaches adopted to address these challenges.

Jan 1, 2013

By Zibo An, Yong Hu, Hao Zhang, Hong Cao, Jun Xue, Zhen Luo

Phosphogypsum (PG) is a by-product of solid waste produced by the phosphate chemical industry. Owing to large emissions and massive storage issues, it causes a potential threat to our environment. Hereby, a method based on the precipitation and crystallization properties of calcium phosphate-magnesium ammonium phosphate (CP-MAP) followed by its adsorption on active solid waste powder is used as the main principle to treat PG harmlessly. The treatment process and its influencing factors for orthogonal experiments along with the associated environmental safety have been studied in detail. The results showed that this method could simultaneously remove soluble phosphorus and soluble fluorine from PG. When ACP, FA, HBM, and Ur were added to PG at a dosage of 3%, 13.5%, 0.04%, and 0.04%, respectively, the residual phosphate and fluoride contents was 0.061 mg/L and 0.856 mg/L respectively in the PG leaching solution. Compared to state-of-the-art approaches, this method exhibited higher efficiency in removing phosphate and fluoride. Most importantly, this method does not cause any secondary pollution in the process, thereby showing a novel application in large-scale industrial treatment.

Aug 29, 2022

By Galymzhan Karamyrzayev, Rashid Nadirov

Zinc ferrite ( ZnFe2O4) is a by-product of non-ferrous metal production and is considered a promising source of raw zinc. The most efficient way to extract zinc from its ferrite is via acidic extraction, specifically leaching by hydrochloric acid. A comparative study of synthetic zinc ferrite hydrochloric acid leaching in isopropanol, aqueous, and the mixed solvent was performed. Zinc ferrite was obtained by sintering a zinc and iron (III) oxide mixture. Crushed samples were subjected to leaching in 1 M HCl at 323, 333, and 353 K and pulp density of 1 g/100 mL. The dissolution of zinc and iron into solution in organic media reached 77% at 353 K, while in an aqueous environment this value was 65%. The activation energy of 70.0 kJ/ mol was found for the leaching process in an isopropanol environment, which is lower than that in an aqueous solution by 15%. The more efficient leaching effect of isopropanol is attributed to the lower dielectric constant of the alcohol which increases the affinity of chloride anions for zinc and iron cations at leaching.

Jun 5, 2022

By Nikhil Dhawan, Veeranjaneyulu Rayapudi

This study investigates upgrading of low-grade banded hematite quartzite iron ore (Fe ~31%). Conventional beneficiation was found to be futile. The susceptibility of iron phases to microwave exposure and their selective absorption assists in the liberation of iron values. Microwave exposure of coarse particles at 540 W for 10 min yielded a concentrate with Fe 56.30% and recovery of 50.68%. Conventional carbothermic reduction at 500 °C, 60 min and 9% charcoal yielded a concentrate with Fe 57.6% and iron recovery of 68%. The presence of sufficiently bonded silica leads to an easy formation of a fayalite phase. The microwave reduction design yielded FeG of 57.6%, FeR of 47% and a yield of 24% at an optimal condition of 540 W, 8 min and 6% charcoal. It was found that a small fraction of microwave-irradiated ore-charcoal mixture melted rapidly, and pure ferrite balls were observed within 8 min. An optical micrograph of a ferrite ball reveals the retained austenite and martensite phase.

By L. Zhou, A. Martikainen, G. Goodman

Continuous airflow monitoring can improve the safety of the underground work force by ensuring the uninterrupted and controlled distribution of mine ventilation to all working areas. Air velocity measurements vary significantly and can change rapidly depending on the exact measurement location and, in particular, due to the presence of obstructions in the air stream. Air velocity must be measured at locations away from obstructions to avoid the vortices and eddies that can produce inaccurate readings. Further, an uninterrupted measurement path cannot always be guaranteed when using continuous airflow monitors due to the presence of nearby equipment, personnel, roof falls and rib rolls. Effective use of these devices requires selection of a minimum distance from an obstacle, such that an air velocity measurement can be made but not affected by the presence of that obstacle. This paper investigates the impacts of an obstruction on the behavior of downstream airflow using a numerical CFD model calibrated with experimental test results from underground testing. Factors including entry size, obstruction size and the inlet or incident velocity are examined for their effects on the distributions of airflow around an obstruction. A relationship is developed between the minimum measurement distance and the hydraulic diameters of the entry and the obstruction. A final analysis considers the impacts of continuous monitor location on the accuracy of velocity measurements and on the application of minimum measurement distance guidelines.

Jan 1, 2012