Search Documents

By H. Hinds

Plant testing of DuPont's Activator Technology in the vat leach circuit of the Homestake mine shows increased gold recoveries of 3-5%. Activators are catalysts of gold dissolution in cyanide solution. DuPont received the patent for this technology in January, 1996. The test was run in the west sand plant alternating control and activated vats to reduce the variability in head grade and cyanide consumption. Activated vats had gold in the preg solutions earlier, higher gold recovery, and lower gold residuals. Activator addition did not adversely affect mill operations or the environment. Optimization of the technology continues.

Jan 1, 1997

By R. Hogg, R. C. Klimpel, D. T. Ray

The sedimentation and dewatering characteristics of flocculated slurries are determined by the size and density of the flocs. Studies of the formation and growth of flocs reveal that floc size is limited by breakage of the agglomerates due to shear in the suspension. Floc density measurements indicate that there is an inverse relationship between size and density. This relationship appears to be determined primarily by the nature of the solid particles, especially the size distribution, but it appears that agitation of the suspension can lead to some densification of the flocs, in addition to breakage. It follows that both size and density can be controlled to a significant extent by regulating the physical conditions (agitation, method of flocculant addition, etc.) during flocculation. The use of physical floc conditioning to control the sedimentation and dewatering (filtration) behavior of flocculated, fine-particle suspensions is evaluated in terms of its effects on floc size and density.

Jan 1, 1988

By Susan T. Bagley, Linda D. Gratz, Kirby J. Baumgard

The extensive use of heavy-duty diesel engines in underground mines has raised concerns about the potential adverse health effects to miners exposed to diesel particulate matter (DPM) which contains mutagenic and carcinogenic organic compounds. The purpose of this study was to compare the levels of DPM, biological activity, and polynuclear aromatic hydrocarbons (PAH) attributable to diesel engines in underground coal mines and similar data collected in engine laboratory facilities to assess whether laboratory data could be used to predict in-mine levels of diesel emissions. Mean in-mine DPM and SOF concentrations varied from 0.90 to 1.9 mg/m3 and 0.08 to 0.40 mg/m3, respectively. DPM-associated mutagenicity (mean) levels at two of the mines varied from 400 to 970 revertants/m3. Concentations of three PAH differed by up to four-fold between two of the mines, largely reflecting differences in DPM and SOF levels. The laboratory raw exhaust data were divided by 100 to obtain expected or predicted values for in-mine concentrations. The predicted DPM, SOF, mutagenicity, and PAH values based on laboratory samples were not significantly different from many of the in-mine values. Using a potential in-mine dilution ratio range of 20 to 200:1, virtually all in-mine data fell within the predicted range. Therefore, an estimate of in-mine concentrations can be determined by evaluating laboratory data. This will allow for extrapolations from laboratory tests with particulate emission control devices to assess potential health-related benefits due to their in-mine use.

Jan 1, 1991

By Joel L. Morrison

Wet bituminous coal fines from active and abandoned slurry impoundments are currently being examined as a recoverable feedstock for the production of coal water slurry fuel (CWSF). Preliminary analysis indicates that these coal fines can be converted into low solids, low viscosity CWSF with acceptable stability without the use of viscosity modifiers (dispersants) or stabilizers. Efforts are now underway to determine if the impounded coal fines can be economically cleaned by froth flotation to an ash level of < 12 wt. % and a total sulfur content of 1.2 wt. %.

Jan 1, 1995

By Ziyan Ouyang, Haotian Zheng, Spencer Quiel, Mike Mooney, Clay Naito

This paper summarizes the results of an experimental program conducted to characterize the moment-rotation behavior of skewed flat radial joints from large diameter (45 ft) tunnel lining. Both positive and negative joint moment-rotation behaviors were measured experimentally using two-segment joint combination assemblies. The results are compared to closed form methodologies used by designers, e.g., the Janssen method. The differences in observed and model behavior are discussed within the context of design practice.

Jun 23, 2024

By Todd S. Harris

Industrial minerals or non-metallic minerals are loosely used terms applied to a diverse assortment of materials which, in many cases, have nothing more in common other than the fact that they are neither metals nor fuel minerals. To help bring order to this otherwise random assortment of minerals, we have grouped these materials into two main categories; chemical and physical minerals, and nine sub-categories based on end-use applications as shown in Table 1. Chemical minerals are products which are principally used for the specific chemical elements they contain, whereas physical minerals are products which are used to meet specific performance specifications. The latter part of the 1970?s, in particular 1978, were considered peak years in terms of production and sales for many industries, By using 1978 as a base year, we can evaluate wherethese markets stand today after the recession of the early 1980&apos;s and the recovery which began several years ago. From this historical overview and appraisal of the current situation, various assumptions can be drawn as to which markets are expected to perform well into the 1990&apos;s.

Jan 1, 1987

By J. C. Weimer

The goal of Bethlehem&apos;s mining research program is to improve both the safety and productivity of our mines through the use of new equipment, new technology and new mining methods. Although we can all agree on the value of such goals, achieving them can be a costly, time-consuming and sometimes frustrating experience. However, the potential benefits of lower costs per ton and better safety in an increasingly more stringent and confusing regulatory environment make the expended effort worthwhile. At Bethlehem we feel that the mining companies are in the best position to determine the needs of the industry, and coal companies have the incentive as well as mine sites at their disposal for testing. Therefore, the mining industry should be leading the research effort

Jan 1, 1979

By Nathaniel Arbiter

In attempting to assess the contributions of Antoine Gaudin to the profession which he illuminated for almost a half-century, we will need to examine a very broad canvas. He was active in three significant areas: as a teacher; in research, both through his own endeavors and those of his students; and as a consultant to the mining industry and to the Government. Beyond these specific contributions, there was the major personal influence he had on scores of students, friends, and colleagues in the profession. If a single measure of the man&apos;s contribution is to be found, it will be the extent and direction in which he influenced the practice of his profession. To find this we should examine the state of miner- al processing when he began his activities in the 1920&apos;s, the progress which has taken place over the past half-century, and the part his activities played in this advance. However, there is a provocative and broader examination which I have chosen to make instead. This is to examine the past century in mineral processing through the lives of three men who, by common agreement, stand on the heights, both in teaching and in their contributions to industry: Robert H. Richards, Arthur F. Taggart, and the man whose memory we honor this evening, Antoine M. Gaudin. Their careers, by coincidence, cover just a century. This is also AIME&apos;s first century, and the first century of mineral industry education in the United States. In fact, mineral processing itself on any significant scale in the country encompasses only a century and a quarter. BEGINNINGS OF PRACTICE IN THE U.S. Before the 1840qs, U.S. mining, except for coal and iron ore, was on a small scale and was confined to the eastern states, with processing practically nonexistent. The 1840&apos;s saw the beginning of Michigan native copper production, including ore dressing; the 18501s, iron ore production in Minnesota; and the 18601s, lead production and processing in Missouri. But the most explosive event was the California gold rush after 1848, which not only brought tens-of-thousands of fortune hunters to the West, but also catalyzed broad mining activities and processing within the following decades. This was not only in Calif-

Jan 1, 1976

By S. Peng, N. Vayenas, A. Farah

"While genetic algorithms have been widely adopted in ore grade estimation and optimization, mine design, and production scheduling in the mining engineering field, reliability and maintainability analysis of mining equipment using genetic algorithms has been a relatively new research area in recent years. This paper presents an application of genetic algorithms using case studies with seven underground scoop trams whose maintenance records have been collected over a period of 12 months from an underground mine in the Sudbury mining area. Based on the assumption that various factors that contribute to machine failures resemble the biological evolution process, the authors have developed an in-house PC software application called GenRel which adopts genetic algorithms in its programming. In this study, the authors feed the historical maintenance data into GenRel in order to predict future maintenance characteristics of mining equipment in a time period of three months. Then the predicted maintenance characteristics are compared to the actual maintenance records in the same time period. A statistical study is then used to examine the similarity between the predicted data and the recorded data.INTRODUCTION Today maintenance costs of sophisticated engineering systems are so high that maintainability draws great attention from scientific researchers to operations managers. For instance, a study by [1] shows that American manufacturers spend more than 300 billion U.S. dollars on plant maintenance and operations. Therefore it is understandable that the main objectives of applying maintainability principles to engineering systems are to reduce projected maintenance costs, to use maintainability data to estimate system or equipment availability/unavailability and to determine labor-hours and other related resources needed to perform the projected maintenance. A system with better maintainability would inherently provide the benefit of lower maintenance costs, less time to recover with lower breakdown frequency (design for simplicity), less complexity of maintenance tasks and relatively reduced man-hours [2]. Most maintainability functions use the Time To Repair (TTR) as the independent variable. It is common to use probabilistic or statistical concepts to define a maintainability function, for example, the probability density function. Let t denote the time. Assuming a repair starts at t=0 and completes at time T, the maintainability can be mathematically defined [3] as in Equation (1)."

Jan 1, 2015

By Leo J. Laughlin

In recent years, heavy mining applications have put an increasing demand on conveyor pulleys. This has resulted in the increased usage of turbine pulleys. The designs of these pulleys are often based upon the failures seen in the conventional welded designs, overlooking the interaction of pulley-shaft system components as the profile of the disc is modified. This paper will focus on the development of balanced design philosophy using case studies of turbine pulleys in heavy mining applications, evaluated with FEA.

Jan 1, 2002

By Wen L. Cai

This paper examines the effects of different block dimensions and cone bases on the economic open pit limit design based on case studies on a coal deposit consisted of two west- east elongated, near vertical thin seams starting with a base model dimension of 200x170x50 (NX*NY*NZ) with a block dimension of 10mx5mx4m (DX*DY*DZ), the blocks were combined along easting, northing and elevation directions. Two cone bases were used, one with a base radius of 10 meters, the other with a base radius of 0. Two pit design algorithms, one is the floating cone algorithm, the other is an optimum algorithm, were used to see which one of the two pit design algorithms is more sensitive to block dimension and cone base variations. The results are presented and analyzed.

Jan 1, 1992

By J. Hoover

Real growth in the economy, increasing demand for electricity, and consumer stockpiling for a possible United Mineworkers of America (UMW) strike in October made 1984 a banner year for coal. Production and consumption climbed to record heights. Precautionary purchases brought inventories close to the peak levels of early 1981 when coal miners walked out for 72 days. Production slowed in the fourth quarter after labor and management concluded negotiations without a walkout. But output in every major coal producing state showed significant gains during the year US coal production totaled 807 Mt (890 million st) in 1984. This is a 13.8% increase over 1983 output. Lower production rates, principally in Appalachia, and sustained demand in the final quarter put downward pressure on coal stocks by the end of the year. Demand All market sectors experienced greater requirements for coal in 1984. Electric utility coal consumption increased 6.3%; exports climbed 4.8%; coke plants consumed 18.9% more coal; coal requirements in the other industrial sector expanded by 11.8%; and consumption in the residential/commercial sector rose 8.1%. Domestic consumption of coal reached a record 718 Mt (791 million st) in 1984. This is a 7.4% gain over the previous consumption high of 668 Mt (737 million st) in 1983. Electric Utilities The 4.6% increase in electric power generation in 1984 was coupled with expanding coal use relative to other energy sources. This resulted in a 6.3% rise in coal consumption, totaling 603 Mt (664 million st) for the year. Thirty-eight of 45 states where coal-fired electric power plants were operating shared in the 36-Mt (39 million-st) increase in electric utility coal consumption

Jan 5, 1985

By Tom Bruington

This paper discusses the accuracy of determining the quantities of gold and silver on activated carbon in various stages of process for typical precious metals flowsheets. Accurate plant performance evaluation depends upon reliable estimates of carbon and precious metals inventories. The sources of sampling error are identified and methods of reducing them discussed. Several case studies illustrating the sensitivity of flowsheet performance to sampling error are presented.

Jan 1, 1991

By D. A. Wheeler

Invented by Pierre Boutin in the early 1960s the column was a complete break from the conventional flotation cell. 1. When used as a rougher-scavenger, the column is excellent. 2. When used as a cleaner, the results can be spectacular. The very first column tests were carried out using it as a rougher-scavenger in a reverse float where silica was floated from iron. It produced a concentrate underflow as good or better than that produced from roughing and scavenging stages in cells, The froth tailing overflow was better than that produced by several stages of cell cleaning. Column scaleup progressed rapidly from the two inch diameter unit to a semi automated 12 inch diameter column on material from the Iron Ore Company of Canada. A change in operating philosophy within IOCC brought all flotation development, column or conventional, to a halt. At that time, IOCC had an exclusive right to the use of the column in Canada in the field of iron ore. We moved into the field of sulphides. A Canadian copper producer sent ore for testing and the results led to their purchase of the first commercial size of column - a 36 inch diameter machine. It was a mechanical disaster. It took several years to raise sufficient funds to return to that mill with our basic 18 inch square unit. It was to be tested and modified in order to learn how to properly design a large column. Originally used as a rougher- scavenger, it had to produce tails equal to the final tailings from this well run plant. It did, and did so while producing a rougher-scavenger concentrate almost equal to the plant final concentrate. It was finally used as a cleaner and produced concentrate 5% higher in copper than the plant final concentrate with equal cleaner tails. This phase of the column development was carried out under very difficult circumstances. The mill superintendent had realized that if he took the froth removal system from our original mechanical disaster and applied it to a conditioner while injecting air, he would have a flotation cell. He had personally applied for patents on this Maxwell Cell. Our development work was done in his mill and as our results became better and better, our difficulties became worse and worse. We finally had to terminate this work. The 18 inch column installed at Mines Gaspé 14 years later was identical to the one removed from Opemiska. The 18 inch column was tried on various ores over the following years and always produced excellent results. However, it was not really a production size unit. We had always aimed for the 72 inch column (72" x 72" x 44&apos; 9"). Prior to this huge machine, we needed the intermediate 36 inch column. The failure of the original 36 inch diameter unit at Opemiska had raised the possibility of short circuiting inside the column as the cross section increased. The first 36 inch square unit was tested in parallel with the proven 18 inch column. If the underflow of the 36 incher was not as good as that of the 18 incher, short circuiting was a possibility in the larger unit. It had been designed for insertion of drop in partitions, four feed points had been provided and the 36 inch column would have become a modular unit of four 18 inch columns. Testing showed the underflows of both columns to be identical. There was no short circuiting in the 36 inch column. Once we had the 36 incher, we had no fear of the 72 inch column. It is permanently partitioned into four 36 inch columns but uses only one set of instrumentation. All the component parts of the 72 inch column come from the 36 inch unit. In spite of our results, the mining community did not believe the column could work. Finally, in 1980, Mines Gasp6 ordered an 18 and 36 inch column for their byproduct molybdenum

Jan 1, 1988

By Cyril W. Draffin

Introduction Americans have long been proud of their ability to recognize a need, define it, and then develop workable solutions. The U.S. underground coal conversion (UCC) program is a good example. In 1974, the need to utilize coal resources that could not be mined was recognized, and Congress gave the Bureau of Mines $1.7 million to gain a better understanding of the UCC technology and its potential applications. Since 1977 when the U.S. Dept. of Energy (DOE) was formed, workable technologies have been tested, the market for underground coal conversion has been recognized, and extensive industrial interest has developed. Perspective The U.S. is blessed with extensive coal resources. Coal supplies about 19% of our national energy needs, yet recently promulgated environmental standards and increasing mining costs have limited direct coal use. UCC potentially can use coal that is economically or technically infeasible to mine because the coal is too thick, deep, dirty, high-ash, and wet; has an excessive angle of dip; or has unpredictable and poor over-burden characteristics that make mining unsafe. Coal can be gasified underground or perhaps liquefied below the earth&apos;s surface. Underground coal gasification (UCG) is the prime element of the underground coal conversion program. It enables coal to be converted to gas underground. UCC Coal Resource Recent data show a total U.S. coal resource base of about 6.4 trillion tons. Of this, 1.8 trillion tons might be accessed by UCC, including some minable coal. A commercial UCC process could quadruple roughly the 450 billion tons of U.S. coal reserves, which presently are recoverable by mining. The U.S. coal resources are divided into five sectors. The two most eastern sectors contain relatively thin, swelling bituminous coals that are difficult to gasify. Of the two, the bituminous coal in the Eastern Province is the most difficult because it is deeper than in the Interior Province and the terrain is more rugged. The sector along the Rocky Mountains contains huge amounts of thick low-rank coals that are the most promising for early development by UCC. The coal has good continuity and the terrain is suitable. Low-rank coals such as subbituminous and lignite are highly reactive and tend to shrink and disaggregate when heated. Most of the coal in the Pacific

Jan 9, 1980

By John Dean

"Pumping backfilling medium used to fill in holes and caverns in mines is challenging. The often viscous, high solids materials are extremely abrasive and can destroy pumping systems in a matter of days. While a number of options are available, using a progressing cavity pump can often be the best solution. High pressure and capacity capabilities, coupled with low wear rates, ensures reliable cost effective operation.Thickened slurry backfilling for underground/excavation mining applicationsVoids and caverns develop as a result of mining operations penetrating deep into the earth seeking natural resources. After extracting all the ore from a mine, operators need to fill in these voids to preserve the integrity of the mine structure. They do this by pumping in a backfill medium. Each mine uses a different mix of components for backfilling, depending upon the mine’s specific structural requirements and environmental concerns, particularly water requirements. Most backfill mixes contain cement, or another cement-like substance, that acts as a binder to hold the backfill medium together. This is combined with tailings (unused rocks and waste from processing and/or extraction), and may also include chemicals or other binders to increase the material’s strength.Backfill pumping challengesPumping the backfilling medium can be a significant undertaking. This process involves transporting very viscous and high solid materials; the mix may contain 60-80 percent solids. These backfill slurries are extremely abrasive and the viscous material can wreak havoc with pumping systems. The material’s paste-like consistency presents problems for standard centrifugal pumps often used in other mining applications.Added complexity is posed when trying to achieve the required pressure, which depends upon how far away the material has to be pumped. It is not difficult to meet the pressure requirements if mixing the backfill material close to the area to be filled. However, pumping from extreme distances can be problematic — a great deal of pressure is required to transport the material from the mixing area to a distant backfilling site. Ideally, operators should be as close as possible to where they are filling, so they can use a smaller pump with lower power requirements."

Dec 1, 2018

By D. A. Harman

The U.S. Environmental Protection Agency recently recognized Newmont and other mining companies, along with the Nevada Division of Environmental Protection for their voluntary work in reducing mercury air emissions. One example of this voluntary effort is the installation of a reactive scrubber to capture mercury vapor from the exhaust of a carbon regeneration kiln at Newmont’s Twin Creeks Mine. After considering the available technologies, a proprietary reactive scrubber, developed by ADA Technologies, Inc., was selected and is currently being commissioned. Mercury removal rates greater than 90% have been documented.

Jan 1, 2004

By T. S. Lundström, B. D. Marjavaara, I. A. S. Larsson

"The flow field in a rotary kiln, used in an iron ore pelletizing process, was investigated using a three-dimensional computational fluid dynamics model. The model is isothermal, downscaled and simplified. The objective was to examine the possibility of capturing the unsteady motion of the flame seen in the real kiln. The results from the simulations were compared with recorded images of the real process. The results demonstrate the possibility of quickly getting an overview of the flow field in the kiln. The main, unsteady behavior of the flame was captured. The model may be used as a tool in the ongoing work of improving and optimizing the pelletizing process.IntroductionThe pelletizing process, in which the crude iron ore from a mine is upgraded into pellets, is a process involving large amounts of hot air flowing in complex geometries. Flow control is a crucial factor in this process to maintain high pellet quality. The rotary kiln is one of the last steps in the pelletizing process, and this is where the pellets are sintered to increase their strength and metallurgical properties. The kiln burner produces a flame that supplies the entire pelletizing process with the necessary heat.Kiln burner flames are large diffusion flames arising from a jet of fuel from the burner issuing into a concentric confining cylinder with a surrounding coflow of air, called secondary air. To enable combustion, the secondary air needs to be entrained into the fuel jet. This mixing of the fuel and air is the slowest step in the combustion process and therefore affects the efficiency of the combustion. The rate of entrainment depends on the momentum ratio between the burner jet and secondary air. The higher the momentum ratio, the faster the entrainment rate and, consequently, the faster is the fuel/air mixing.The kiln of interest in this study differs from kilns used in other industrial processes in both geometry and operating conditions. A distinguishing feature is the large amount of secondary air being induced through the kiln hood and then transported to earlier stages in the process as air or exhaust gas. The secondary air therefore has a substantial momentum, implying that the resulting flow field has a significant impact on the mixing and combustion process in general and the flame shape and stability as well as combustion efficiency in particular. A systematic study of the factors influencing the dynamics of the flow field in the kiln, neglecting the combustion, is therefore justified."

Jan 1, 2016

By H. H. Murray

Industrial usage of clays for current and new applications will continue to grow into the next century. The rate of growth will be highest in the less developed areas of the world. Transportation costs are a significant part of the delivered price, so the location of reserves and processing facilities for kaolin, bentonite, and palygorskite (attapulgite) are reviewed relative to serving these emerging markets. New value added applications will increase in the more developed areas which will require high quality raw materials, more sophisticated processing, and rigorous quality control.

Jan 1, 1998

By Richard Giffen, Martha Gross, Luca Pellegrini, Pa Ousman Njie

The Hampton Roads Bridge-Tunnel (HRBT) Expansion project in Virginia includes parallel 1.5- mile (2.4 km) tunnels constructed using a tunnel boring machine (TBM). The TBM launching and receiving shafts were excavated within the footprint of two reclaimed islands abutting the navigation channel for the Port of Virginia. The shaft excavations—a circular tri-cell shaft at South Island, and a circular-rectangular twin-cell shaft at North Island—were supported by slurry walls up to 190 feet (58 meters) below the island surfaces. This paper describes specic design considerations for these shafts, as well as construction and uality-oversight aspects of their excavation and construction.

Jun 23, 2024