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By A. S. Hall

Significant pyrite often does not dissolve in the Sobek (1978) nitric acid extraction; therefore, the standard conservative approach is to estimate pyrite using sulfur present in the sum of the nitric acid and residual sulfur fractions. Alunite, when present, appears as residual sulfur. Because alunite does not generate acidic effluents, overestimation of AGP can occur if all residual sulfur is assumed to be undigested pyrite. Evaluation of 16 samples from the Florida Canyon Mine revealed that petrographic examination coupled with a modification of the Sobek method to include a 6 hour hot (250°F) 'nitric acid extraction resulted in a more accurate estimation of AGP.

Jan 1, 1999

By James A. Decker

Hanna has developed three production planning systems to help the mine engineers determine the sequence of mining from available ore supples. The Production Scheduling System was developed to give the staff a tool for long range planning by sequencing the removal of blocks from an open pit property. It was needed to determine the year of removal for each block so that the optimum present-valued pit limits could be established by our pit design program. Since in this type of planning short term grade control is less of a factor than it is in daily or monthly planning, the system gives the program greater control and more latitude in block selection. It permits only full blocks to be taken.

Jan 1, 1984

By A. Gupta, F. Hrach, L. R. Mendoza, K. Flynn

ST Equipment & Technology LLC (STET) has developed a novel processing system based on tribo-electrostatic belt separation that provides the mineral processing industry a means to beneficiate fine materials with an energy-efficient and entirely dry technology. In contrast to other electrostatic separation processes that are typically limited to particles >75μm in size, the STET triboelectric belt separator is suited for separation of very fine (<1μm) to moderately coarse (500μm) particles, with very high throughput. The STET tribo-electrostatic technology has been used to process and commercially separate a wide range of industrial minerals and other dry granular powders. Here, bench-scale results are presented on the beneficiation of low-grade Fe ore fines using STET belt separation process. Bench-scale testing demonstrated the capability of the STET technology to simultaneously recover Fe and reject 2 from itabirite ore with a D50 of 60μm and ultrafine Fe ore tailings with a D50 of 20μm.The STET technology is presented as an alternative to beneficiate Fe ore fines that could not be successfully treated via traditional flowsheet circuits due to their granulometry and mineralogy. INTRODUCTION Iron ore is the fourth most common element in earth’s crust [1]. Iron is essential to steel manufacturing and therefore an essential material for global economic development [1-2]. Iron is also widely used in construction and the manufacturing of vehicles [3]. Most of iron ore resources are composed of metamorphosed banded iron formations (BIF) in which iron is commonly found in the form of oxides, hydroxides and to a lesser extent carbonates [4-5]. A particular type of iron formations with higher carbonate contents are dolomitic itabirites which are a product of the dolomitization and metamorphism of BIF deposits [6]. The largest iron ore deposits in the world can be found in Australia, China, Canada, Ukraine, India and Brazil [5]. The chemical composition of iron ores has an apparent wide range in chemical composition especially for Fe content and associated gangue minerals [1]. Major iron minerals associated with most of the iron ores are hematite, goethite, limonite and magnetite [1,5]. The main contaminants in iron ores are 2 and Al2O3 [1,5,7]. The typical silica and alumina bearing minerals present in iron ores are quartz, kaolinite, gibbsite, diaspore and corundum. Of these it is often observed that quartz is the mean silica bearing mineral and kaolinite and gibbsite are the two-main alumina bearing minerals [7]. Iron ore extraction is mainly performed through open pit mining operations, resulting in significant tailings generation [2]. The iron ore production system usually involves three stages: mining, processing and pelletizing activities. Of these, processing ensures that an adequate iron grade and chemistry is achieved prior to the pelletizing stage. Processing includes crushing, classification, milling and concentration aiming at increasing the iron content while reducing the amount of gangue minerals [1-2]. Each mineral deposit has its own unique characteristics with respect to iron and gangue bearing minerals, and therefore it requires a different concentration technique [7].

Jan 1, 2019

By P. Geoffrey Feiss

The Piedmont province of the southern Appalachians is becoming the focus of interest for many exploration geologists. In the past, only those deposits with significant surface exposure have been exploited. Thus, few deposits have been found and relatively little exploration has been conducted in recent years. Modern geochemical and geophysical techniques can alleviate this problem of concentrating on exposed ore bodies by allowing us to "look through" the soil and saprolite to detect the presence of significant mineralization at depth. This paper will attempt to evaluate the feasibility and effectiveness of several geo¬chemical exploration techniques in the Piedmont, of Cabarrus and Stanly Counties, North Carolina. The area chosen for the study is shown in Figure 1, lying almost wholly within the Mt. Pleasant quadrangle, North Carolina. The area is on the eastern boundary between the Charlotte belt, a zone of plutonic and intermediate grade metamorphic rocks, and the Carolina Slate belt, a series of complexly interbedded volcanic and sedimentary rocks of predominantly low grade metamorphism. The area is now considered to be a 500 million year old active, continental margin.1 As is typical of most of the piedmont, outcrop is sparse. Figure 2 is a sketch map of the general geology of the area under study, showing the Charlotte belt rocks in the northwestern quadrant and slate belt rocks, to the east. Within the area are a number of old mines and prospects, the most famous of which are the Furniss and the Phoenix mines in Cabarrus County. All are reported to have contained Au and Cu. Ag and Pb were reported from some. A summary of the deposits is given in Table 1. Data used in this study are from three Master&apos;s theses conducted at the University of North Carolina at Chapel Hill. 3,3,6 In separate studies, well waters5, B-zone soils3, and vein and float quartz6 from the area described were sampled and analyzed. Each study concluded separately that geochemical anomalies in the vicinity of the ores justify use of that specific sample type in a geo-chemical exploration program. However, no comparative study of the methods has

Jan 1, 1977

By J. P. Hedlund

Molycorp&apos;s gravity type panel-caving operation employs a system of short raises to transfer ore from the Grizzly Level to the Haulage Level. The raises have normally been developed using a conventional drill-and-blast method or a combination conventional/raiseboring method. A new method was needed that would be less labor intensive, provide a safer work environment for personnel, provide a stable raise that could be self-supporting and a method that would be cost competitive with the conventional system.

Jan 1, 1991

By F. Woller

The territory of Czechoslovakia is well endowed in deposits of a variety of industrial minerals. At present, 29 different types of industrial minerals are mined from some 600 individual deposits in Bohemia and Moravia only. About half of those production centres involves structural materials like aggregate and common brick clays and loams. A significant proportion of industrial minerals produced in Czechoslovakia are exported. Destinations of main products are shown in Figure 1. Production of industrial minerals in Czechoslovakia has a long history. Glass has been produced since the 14th century, sulphuric acid since 1578, graphite since 1750, and chinaware since 1790, to name just a few; but most of the present production comes from deposits developed during the past forty years. For a variety of reasons, only about 30 per cent of registered and explored industrial minerals deposits in the country are in production (Table 1). Two of the reasons may be the complexity of processing or conflicting interests of parties involved, but lack of market research, investment funds, or processing capacity have also had an impact on the level of utilization of the resource base.

Jan 1, 1992

By Guy T. Jr. McBride

World food production is not matching the exploding increase in world-population. Since arable land is limited, ways are being sought to increase yields by turning_ to fertilizer. Phosphate, an essential fertilizer ingredient, is undergoing a period of growth unparalleled in history. The United States is at once the world&apos;s largest producer of food and of phosphate rock. Both food and fertilizer output in the United States are being enlarged to meet the demands posed by the threatening world food crisis. New phosphate deposits are being developed in Florida and North Carolina to assure the United States&apos; continued preeminence in this vital resource. Large fertilizer complexes are also being constructed with an eye to both domestic and foreign markets. The growth of the U. S. phosphate industry has been characterized by developing technology in the processing and distribution of phosphate raw materials. The trend from low analysis to high analysis materials accompanied by a change from a large number of small fertilizer plants oriented toward the marketplace to a fewer number of large plants located at the raw material source is illustrative. These changes in technology and distribution have also been important factors in the development of new mining areas in Florida, the Western States and North Carolina.

Jan 1, 1966

By B. J. Sauer

Misapplication of AC induction motors for mine crusher and mill applications has long been a frustration for both the driven equipment supplier and the mine operator. Proper selection of AC induction motors is critical to providing efficient production. This paper focuses on the selection of AC induction motors for gyratory crusher, cone crusher, and grinding mill applications. The criteria for motor selection includes: proper enclosure, driven equipment torque requirements, bearing life, temperature rise, starting requirements, ambient temperature, altitude and accessory requirements.

Jan 1, 1999

By B. S. Hulvey

Thin support liners are becoming more accepted and being developed with improved properties because the mining industry as a whole has been offering underground safe test trial sites. This is because of the huge potential for such products. Recent developments tend to indicate that the technology is “coming of age” and these are discussed in this paper.

Jan 1, 2003

The properties of interfacial water at hydrophilic surfaces are of great importance in many technological areas including flotation, solid-liquid separation, dispersion and emulsions, flocculation, adsorption, corrosion, and soil contamination. This paper examines the use of FTIR/internal reflection spectroscopy (FTIR/IRS) to study the spectral characteristics of interfacial water at silica surfaces. FTIR spectra were characterized by consideration of the OH stretching region (3000-3800 cm-1) associated with the vibrational spectra of interfacial water. The broad peak in this region was deconvoluted in order to isolate overlapping spectral features that describe the nature of hydrogen bonding in interfacial water. Three distinct bands were found; -3600 cm-1 (free OH), -3400 cm-1 (incomplete tetrahedral coordination), and -3240 cm-1 (complete tetrahedral coordination) and the variation of their intensities with pH was found to be significant. This spectral information helps to explain orientation and bond ordering of interfacial water molecules at hydrophilic surfaces.

Jan 1, 1998

The 2012 North American Tunneling (NAT) conference is expected to attract more than 800 tunneling and underground construction professionals. But don?t let the North American part of the meeting?s title fool you. Many of the attendees will come from all over the world. The meeting is scheduled for June 24-27 at the JW Marriott Indianapolis Hotel in Indianapolis, IN. In addition to two and a half days of technical programming, the accompanying exhibit has attracted 116 exhibitors in 140 booths. And the conference will include short courses, a field trip and plenty of social activities that will give attendees the opportunity to catch up with each other.

Jan 1, 2012

By Michael A. Trevits

A mine fire represents one of the most dangerous and challenging safety issues facing underground mine operators. Given the right circumstances, a mine fire can occur at any location in the active or abandoned mine workings, can quickly grow beyond control, and threaten the welfare and livelihood of the entire underground workforce. The National Institute for Occupational Safety and Health (NIOSH), in partnership with the Mine Safety and Health Administration (MSHA), has been conducting an in-depth program of research addressing mine fire prevention, early and reliable fire detection, and mine fire suppression technologies. One portion of this program is focused on understanding the characteristics of mine fire combustion products and flame spread through large scale deep-seated (firmly established) fire tests and use of computational fluid dynamics (CFD) modeling. In this study, two deep-seated fire tests were conducted; one fire consisted of coal material and the other utilized the two most abundant fuel sources found in a coal mine: coal and wooden cribbing blocks. The fires were burned to completion while the combustion products were collected and analyzed. In addition, an array of thermocouples was placed within the body of the material to measure flame spread rate. The coal fire test information was then used to develop a CFD model of the fire. This paper describes the fire tests, provides insight into characteristics of flame spread, and presents the CFD modeling work results.

Jan 1, 2009

By A. P. Cook

Methane Rating has been developed from a need, in South Africa, for quick and simple measurement of coal face methane characteristics. It employs proven existing direct measurement methods, adapted specifically for rapidly advancing coal face conditions, to deal with the short term high release rates encountered during continuous miner coal cutting. The Rating is a comparative value, relative to the normal or average conditions encountered within a maintained data base. The seam gas content and the initial emission rate are plotted against each other on a graph, where they are compared with the average conditions to obtain the rating. The higher the seam gas content, and the higher the initial methane release rate, then the higher the Methane Rating, on a scale of 1 to 4. Methane being released from a newly mined coal sample is measured once underground, from a sealed gas-tight canister. The sample is returned, still sealed, to surface and milled to rapidly release the remaining methane. It is later intended that the milling process is also completed underground. Applications include the identification of changing methane conditions, outburst prone conditions, methane emission against advance, and mining in devolatilised coal.

Jan 1, 1998

By Halter L. Gould

Since the turn of the century there has been a marked increase in population, industrial and economic growth, and in energy requirements in the United States. During this time our energy needs have been met largely by natural gas and petroleum, but as our reserves of these materials are depleted, we are going to depend more and more on our large reserves of coal. The mining of coal for electrical power production has increased at a rapid rate during the past decade. Over half the coal produced in the United States in 1971 came from mines utilizing surface mining operations (Paone, et al, 1974). Surface mining is expected to increase as the rising cost of oil places more demand on coal for energy. About 57 percent of the coal reserves in the United States lie in the area west of the 100th meridian. About one-quarter of this can be mined by current surface methods. This would involve the disturbance of approximately 1.5 million acres (600,000 hectares). By the year 2000, projections indicate disturbance of about 200,000 acres, or 300 square miles, in the West. Mined areas receiving more than 250 mm of annual precipitation can usually be revegetated without irrigation if the spoils are properly shaped, the surface layer consists of suitable plant growth media, and proven techniques in rehabilitating disturbed rangeland are applied. Areas receiving less than 250 mm of annual rainfall or with high evapotranspiration rates pose a more difficult problem. Revegetation of these areas can probably be accomplished only with major inputs of water and good management (National Academy of Science, 1974).

Jan 1, 1978

By P. Tsang

To gain insight into the current status of pillar design practice in the underground coal mines of United States, a survey has been undertaken in the late 1993 and early 1994. A total of 552 room-and-pillar mines and 75 longwall mines have been surveyed to collect general, geological and mine plan information. The collected information are critically analyzed with special emphasis on the pillar design criteria adopted in these mines. A safety factor analysis has also been carried out for the pillars in room-and -pillar mines.

Jan 1, 1995

By Karl J. Benecke

Though the first patent on a bucket wheel excavator was granted in 1881 in the U.S. this technology was developed in Germany to the high standards of today. However, this development was only possible in parallel with the development of shiftable belt conveyors and boom stackers. The combination of these three types of equipment in the open pits of the Federal Republic of Germany has made lignite the cheapest energy source for power generating, despite the low heating value of German lignite in the order of 8500 kJ/kg (3600 BTU/lb) only. Comparing the costs for fuels used in power generating on the basis of their heating value, the relation between lignite, high quality black coal, and imported crude oil is in the order of 1 to 1.5 to 2.5, hence highly in favour of lignite. These cost advantages for lignite in Germany are due mainly to the concentration of lignite mining in a few high-output open pit mines. The largest one, Fortuna Mine in the Cologne district, produced a, total of 45 000 000 t lignite in 1976. That equals the annual fuel need of a 5750 MW power plant running 7000 hours per year at full capacity. Altogether 95 200 000 bank m3 equal to 200 000 000 t overburden had to be removed to accomplish this lignite output. The largest BWE (Fig. 1) ever built is working in the Fortuna Mine, too. At a digging height of 51 m above crawler level, the total vertical reach in relation to the face conveyor level is 98 m by means of its conveying bridge and loading unit. The hourly output is 10 400 bank m3. Its weight in operation is 13 000 t, its wheel diameter 21.6 m, as high as a 7-storey building.

Jan 1, 1977

By P. T. Bissert, J. P. Ducarme, J. L. Carr, A. K. Smith

The continuous mining machine is a key piece of equipment used in underground coal mining operations. Over the past several decades these machines have been involved in a number of mine worker fatalities. Proximity detection systems have been developed to avert hazards associated with operating continuous mining machines. Incorporating intelligent design into proximity detection systems allows workers greater freedom to position themselves to see visual cues or avoid other hazards such as haulage equipment or unsupported roof or ribs. However, intelligent systems must be as safe as conventional proximity detection systems. An evaluation of the 39 fatal accidents for which the Mine Safety and Health Administration has published fatality investigation reports was conducted to determine whether the accident may have been prevented by conventional or intelligent proximity. Multiple zone configurations for the intelligent systems were studied to determine how system performance might be affected by the zone configuration. Researchers found that 32 of the 39 fatalities, or 82 percent, may have been prevented by both conventional and intelligent proximity systems. These results indicate that, by properly configuring the zones of an intelligent proximity detection system, equivalent protection to a conventional system is possible.

Jan 1, 2016

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 R. Eggert

Since the discovery of high temperature superconductors has led to extensive interest and conjecture regarding their potential to change contemporary technology, discussions of the impact on the metallurgical and other industries have naturally arisen. In this paper we present data showing the possible impact of these developments on the materials related to the fabrication and proliferation of devices based on superconductor materials. We observe that the largest volume of effort with LTSC will be for the demonstration of high power devices while applied research relating to processing will remain the principal HTSC activity. We also note that in the next decade copper consumption in the US is expected to remain essentially at the current level while the need for Nb and Sn,; two major components of LTSC, will grow at a faster rate both in the US and the world. Although the use of superconductor-based magnetic separation is anticipated to increase, no major impact of these components on the metallurgical industries is expected.

Jan 1, 1990

By V. Srivastava, T. Ghosh

"Modeling and Simulation of SAG Mill has been widely used in design and optimization of mill performance in terms of its power draw, processing capacity and product size distribution. However, these models are solved under steady approximation and do not provide any information on mill charge distribution in real time. This paper attempts to characterize mill contents by solving Whiten’s first order contents based model in Matlab/Simulink environment. The parameters in the model such as breakage rate (S), discharge rate (D) and appearance function (A) were estimated utilizing process and design data collected from a gold mine operating in Alaska coupled with nonlinear parameter estimation scheme. This model is then utilized to predict dynamic response of other key operational variables such as mill power, bearing pressure, charge level and product size distribution. The transient response of mill behavior with respect to changes in feed size distribution, tonnage and mill feed water is also presented. This dynamic simulation approach can be used for practicing different control strategy and training purposes. The observed response of mentioned variables was validated utilizing dynamic response data from the plant to encompass operational characteristics of SAG Mill behavior. Keywords: SAG Mill, Dynamic Modeling, Simulation, Nonlinear Parameter Estimation. INTRODUCTION Grinding in mineral industry is one the most important steps in the process of size reduction and plays a crucial role in determining the overall economics of the milling plant. Much of the efforts focused on improving the process efficiency using modeling and simulation have been practiced by researcher and engineers. However, up till now these models were simulated under steady state approximation because of their complex nature and difficulty in programming them in a dynamic framework. Steady state simulations have been successfully utilized in circuit designing, capacity planning and pre-flowsheet optimization. The maturity in steady state models is because of its applicability and regular use in steady state simulation packages such as JKSimMet, Limn, ModSim, etc. With the advent of equipment such as SAG and AG mill has been a recent shift in the simulating these models using dynamic approach. Because of the economic benefits of these devices and ability to act both as a primary grinding device and as secondary or tertiary crushing device they have gained a large popularity and are now universal to any milling plant. However, these device poses a real challenge to engineers and researchers in terms of operation and control. The major reason attributed to problems faced is because the ore constitutes the major portion of the charge in these devices when compared to ball and rod mill. This rock charge is subjected to disturbance such as changes in feed size distribution and ore hardness which results in unstable operation and frequent mill stoppages. One way to prevent this is to measure and control these external variables, however, lack of available instrumentation and unavailability of sensors to measure these variables has foiled the understanding of complete process occurring inside the mill thereby, inhibiting development of proper control system."

Jan 1, 2017