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By E. Petrakis, K. Komnitsas

The main objective of batch grinding modeling is the estimation of the product particle size distribution over time or specific energy input to the mill. So far, the developed analytical methods require often complicated calculations which are timeconsuming. Thus, more simple approaches that allow the reliable prediction of the complete product size distribution need to be developed. In the present paper, an approach, based on the population balance model (PBM), that reliably predicts the product size distribution is proposed. In order to enable this, the simplified form of the fundamental batch grinding equation was transformed into the well-known Rosin–Rammler (R-R) distribution, thus allowing the determination of the breakage rate for each grinding period. A time-dependent breakage rate framework was developed where the traditional linear theory of the PBM is considered a partial case. This approach allows the deviations from the linear theory to be categorized and the degree of the acceleration-deceleration of the breakage rate to be predicted. Modeling results were validated by laboratory grinding studies using two homogeneous materials, quartz and marble, and one heterogeneous, a limonitic laterite. The experimental data revealed that grinding exhibits non-first-order behavior and the degree of deviation from the linear theory depends on the tested material. The reliability of the proposed model was validated with the use of the distribution modulus n, the a value of the breakage rate parameter, and the optimum n values that minimize the sum of the differences between the experimental and estimated particle size distributions.

Feb 8, 2021

By William Gleason

The numbers tell the story of this one. More than 50,000 people and 1,890 exhibitors took over the Las Vegas Convention Center Sept. 24-26 for the largest mining trade show in the world ? MINExpo. Inside the convention center, some of the largest machines used in mining were on display. Caterpillar, Liebherr, Komatsu and Hitachi displayed ultraclass offroad mining trucks and shovels. Atlas Copco and Schramm were among companies that rolled in mining drills and Bridgestone, Goodyear and Michelin were among the companies showing off the massive tires used by the trucks. Throughout the three halls and an outdoor display area, just about every kind of product, gadget or service used in the mining industry could be found on display somewhere.

Jan 1, 2012

By James J. Scott

I welcome this opportunity to speak before the Coal Division of the AIME in such an attractive setting as the Pacific Northwest. With the development of the Centralia project, the Pacific Northwest will have its first major coal-fired thermal electric generating plant. This State has a long history of coal mining that diminished with the passage of coal-fired steamships and locomotives but is now reviving with the growth of electrical power demand. Because this 1,400 row plant is to be supplied with surface-mined coal, it is particularly appropriate that this area be the setting for a talk on factors influencing the growth of surface coal mining in the West. During the course of my talk, I will touch on a number of factors including electric power demand, coal resources, production trends, environmental considerations and trends in State and Federal activities that I feel will influence surface coal mining in the West. Total electric power consumption by the year 2000 is expected to reach 9.4 trillion kilowatt-hours. Predictions of total coal consumption for electric power generation by that year range from a low of 845 million tons to a high of 1,520 million tons, or 2.6 to 4.7 times the amount used for this purpose in 1970.

Jan 1, 1971

By Shuie Li, Taibai Li, Tao Hu, Zhongjie Wang, Xiang Ge

As one of the main power sources, lithium-ion batteries (LIBs) will continue to be applied on a large scale in the future market. Commercialized LIBs cathode materials contain various valuable metal elements including Li, Co, and Ni. The development of green and efficient recycling technology is essential. Deep eutectic solvents (DESs) have recently emerged as a new class of green solvents that could potentially be applied for the LIBs recycling industry due to their capability to leach the active materials without the introduction of environmentally hazardous reagents as used in conventional hydrometallurgy process. Considering the rapid progress, a critical review focusing on the progress and fundamentals about the overall efficiency has practical significance for the further advancement of this field. Herein, we briefly introduce the overall process of using DESs for LIBs recycling and specifically focus on the efficiency of each step. Current fundamental understandings and new experimental approaches to enhance the efficiency of the leaching process, the extraction process, and reusability are summarized. We expect this review article to inspire scientists to use DESs as powerful tools for advancing the frontiers of LIBs recycling.

Jul 30, 2022

By M. J. Gregory

The Pebble Cu-Au-Mo deposit in southwest Alaska is one of the world's largest porphyry deposits. The western part of the deposit was discovered by Cominco America in 1987, who sold the project to Northern Dynasty Minerals Ltd., in 2001. Northern Dynasty discovered the high-grade eastern part of the deposit in 2004 and went into a 50:50 partnership with Anglo American PLC in 2007, forming the Pebble Limited Partnership (Lang et al., 2008). The Pebble Limited Partnership has continued to delineate the deposit through diamond drilling with the most recent resource estimate released in February 2010 (Pebble Limited Partnership, 2010). The Pebble deposit mineral resources comprise 5.94 billion tonnes of measured and indicated resources grading 0.78% Cu EQ, containing 55 billion pounds of copper, 67 million ounces of gold and 3.3 billion pounds of molybdenum. Also delineated are 4.84 billion tonnes of inferred mineral resources grading 0.53% Cu EQ, containing 25.6 billion pounds of copper, 40.4 million ounces of gold and 2.3 billion pounds of molybdenum (Pebble Limited Partnership, 2010). Resources are calculated using a 0.3% Cu EQ cutoff. GEOLOGY AND MINERALIZATION Deposit Geology The Pebble deposit is located in the Kahiltna terrane, between terminal strands of the north-east-striking Lake Clarke strike-slip fault. This fault represents an accretionary boundary and separates the Kahiltna terrane to the north-west from the Peninsular terrane to the south-east (Lang et al., 2008). The Pebble deposit represents a large magmatic-hydrothermal system centered on a group of 90 million year old porphyritic hornblende granodiorite intrusions. An east-west cross section through the southern part of the deposit (Figure 1A) shows the typical relationships between the various rock units which host sulfide mineralization. Sub-parallel ~96 million year old granodiorite and diorite sills were intruded into siltstones of the Jura-Cretaceous Kahiltna flysch. In the west, these sills were cut by a ~96 million year old alkalic intrusive complex composed of porphyritic monzonites and monzodiorites and related intrusion breccias (Bouley et al, 1995). The mineralized 90 million year old hornblende granodiorite intrusions cut all rock types and comprise four small stocks in the western part of the deposit and a larger pluton in the eastern part of the deposit. Recent deep drilling indicates that these intrusions coalesce at depth. The strongest porphyry-style mineralization is centered on the eastern granodiorite pluton and extends into the surrounding rock units (Figure 1A). The western half of the deposit crops out at surface, whereas the eastern side is un-conformably overlain by a cover sequence of Late Cretaceous to Eocene sedimentary and volcanic strata. The deposit was tilted 20º to the east during the Eocene.

Jan 1, 2012

By Paul F. Ziemkiewicz, Aaron Noble, Christopher R. Vass

The conventional rare earth element (REE) industry has historically sought to develop ore deposits where geologic processes have produced mineralized zones with commercially attractive REE concentrations. These deposits are extremely uncommon, particularly in the USA. Given the criticality of these materials and the need for sustainable domestic supply, the current research seeks to leverage other autogenous processes that lead to concentrated REE resources. One such process is the generation of acid mine drainage (AMD). AMD is very common in many coal mining districts and results from the exposure and oxidation of pyrite during mining. During the generation and migration of AMD, liberated sulfuric acid mobilizes several metal ions including REEs. Treatment of AMD is required under U.S.C §1251, the Clean Water Act, and often consists of neutralization, oxidation, and metal hydroxide precipitation. To investigate the deportment of REEs during this process, a field sampling campaign was undertaken, whereby the concentration of REEs in AMD and AMD precipitates was measured directly. In the nine sites evaluated in this study, the REE concentrations of the precipitates varied from 29 to 1286 ppm with an average of 517 ppm among the sampled sites. The individual elements were enriched compared with the associated bulk Northern Appalachian (NAPP) coal material by factors ranging from 3 to 15. Furthermore, the distribution of REEs in all precipitate samples favored the heavy REEs (HREEs) when compared with traditional REE ores. This research represents the first part of multi-part research endeavor to characterize, classify, and determine the practicality of refining REEs from AMD and its by-products.

By T. M. Yegulalp

A short review of the current practice and recent developments is followed by a description of a newly developed approach for the solution of the optimum ultimate pit limit problem. The new approach utilizes the network modeling of the problem for solution by maximum flow algorithm. The latest developments in the implementation of maximum flow algorithm present significant time and memory savings as compared to initial development due to Ford and Fulkerson. Results of a series of computational tests are presented to demonstrate how this approach performs as compared to the well-known Lerchs Grossman algorithm. It is also shown that the solution by the new method will automatically include several optimal solutions based on predetermined number of benches to be included in the analysis.

Jan 1, 1993

By Andrew Scogings

The current edition of The Australasian Joint Ore Reserves Committee (JORC) Code was published in 2012 and, after a transition period, the 2012 edition came into mandatory operation on Dec. 1, 2013. There is a significant change between JORC 2004 (Clause 44) and JORC 2012 (Clause 49) for the reporting of industrial mineral resources and reserves, which should be addressed by ASX-listed players in the industrial minerals space.

By Christopher J. Vise

Although production operations at mines, representing the extraction and removal of the mined material, often appear to receive the greatest amount of attention, the emphasis given to auxiliary operations is continually increasing. This is due to the changing economic, social, and environmental climate in which modern mines must operate. Auxiliary operations can best be described as those activities that are not directly related to the extraction and removal of the mined material, but must receive proper attention if recovery is to take place in a safe, efficient, and socially responsible manner. In fact, certain mining auxiliary operations, such as strata control and ventilation, are considered to be of such importance that they warrant separate sections in this Handbook. Judging from a mine-personnel standpoint, it is not uncommon for a mine to hire the same number or more individuals responsible for auxiliary operations as the number assigned to production.

Jan 1, 2008

By Jr. Goller

You and I can visit cement plants, inspect the various rotary kiln systems and find some equipment or some burning techniques that waste energy--fuel and power. After we have made such a visit and studied a few ideas, we could recommend ways to eliminate much of this waste. Probably every idea would cost money to bring into action. For our discussion, let us arbitrarily set an upper limit of $1,000,000 on the recommendations that we are allowed to make. Call these "low-cost" or "short-term" measures. They are improvements that do not require more than say, three months to complete; they do not require a major revision to the process. Other recommendations are "high-cost" or "long-term"; they are outside the scope of this discussion. Some of our "low-cost" recommendations would offer a satisfactory return on the money that they cost; the remainder would not. Now, is there some way that we can rather quickly pick out the "low-cost" measures that will show a satisfactory return and spend our time making these improvements first? Can we separate these items from those where the return is less likely to be good? I feel that we can pick some of these items quickly if we have a kiln system that has consistently non-uniform day-to-day operation. If the operation is uniform we probably cannot pick them quickly.

Jan 1, 1977

By RIINA SALMIMIES, Paula Vehmaanperä, Antti Häkkinen

The dissolution of iron oxides in mixtures of acids is fairly uncommon but can result in a more efficient dissolution process. The objective in this work was to investigate the dissolution of synthetic hematite powder in mixtures of oxalic and sulfuric acid. Experiments were done at different acid ratios and temperatures. An increase in temperature from 15 to 35 °C increased solubility, whereas an increase from 35 to 50 °C did not change the solubility but had a profound effect on the kinetics. An important finding was that oxalic acid advanced the dissolution process since increasing the amount of oxalic acid in the system resulted in faster kinetics and higher solubilities. The dissolution kinetics were well described with the Kabai model, which was the only studied model able to describe the whole reaction time. However, the solid specific constant a varied for the different acid ratios and this is argued to be a result of changes in the solid phase. The changes in the constant a were not in line with the original study of Kabai, which indicates that a cannot be the solid specific constant but it can be the constant connected to dissolving media describing the changes in the dissolution mechanism.

Sep 23, 2020

More than 1,200 professionals from the global tunneling and underground space industries are expected to be on hand for the 2009 Rapid Excavation and Tunneling Conference to be held at Caesars Palace in Las Vegas, NV. The conference, set for June 14-17, is sponsored by the Society for Mining, Metallurgy, & Exploration, Inc. (SME) and the Construction Institute of the American Society of Civil Engineers. The four-day conference will feature more than 100 technical papers in 19 sessions. Two one-day short courses are also planned, as are a pair of field trips. And the show?s exhibit will feature more than 120 of the industry?s leading equipment and service suppliers.

Jan 1, 2009

For nearly two decades, MINExpo International has held the title to the biggest show in mining. The 2012 MINExpo is expected to be the biggest yet, with nearly 1,800 exhibitors rolling out the newest equipment and services across 12 halls. From September 24 to 26 in the Las Vegas Convention Center, MINExpo will present the newest in everything from automation and robotics to safety and communications equipment to reclamation services, and much, much more. The last MINExpo, in 2008, had nearly 38,500 visitors. The show?s sponsor, the National Mining Association, expects this year will be even bigger, with more than 40,000 visitors over three days. Twenty talks on the issues facing mining today are scheduled for Tuesday and Wednesday mornings, but the real action will happen out on the floor. That?s where ultra haul trucks big enough to carry as much as 363 t (400 st) of rock will be assembled next to underground loaders able to lift more than 20 t (22 st) in one scoop. Caterpillar, Komatsu, Liebherr, Sandvik, Atlas Copco: all the big names in mining equipment will be there. Their massive earthmoving equipment and mining machines are the centerpiece of the show. Preassembly for the largest pieces begins on August 6, 2012.

Jan 1, 2013

By M. L. Harris, J. Organiscak, S. Klima, I. E. Perera

"The National Institute for Occupational Safety and Health (NIOSH) Pittsburgh Mining Research Division (PMRD) conducted underground evaluations in an attempt to quantify respirable rock dust generation when using an untreated rock dust and a rock dust treated with an anti-caking additive. Using PDM 3600s and 3700s, these evaluations measured respirable rock dust levels arising from a flinger-type application of rock dust on rib and roof surfaces. Rock dust with a majority of the respirable component removed was also applied in NIOSH’s Bruceton Experimental Mine (BEM) using a bantam duster. The respirable dust measurements obtained downwind from both of these tests are presented and discussed. This testing did not measure miners’ exposure to respirable coal mine dust under acceptable mining practices, but indicates the need for effective continuous administrative controls to be exercised when rock dusting to minimize the measured amount of rock dust in the sampling device. INTRODUCTION Two factors have combined to renew concern regarding respirable dust measurements and compliance. This renewed recognition is due to two regulations that have modified operators’ rock dust schedules. First, the 80% incombustible requirement in intake entries has increased both on-section and outby-the-section rock dusting. Secondly, the recent respirable dust regulation change that has increased the number of respirable dust samples taken per sampling cycle. Previously, when only 5 samples were needed bi-monthly, rock dusting could be scheduled to not interfere with the respirable dust sampling schedule. The significant number of samples now required under new regulations combined with the need to maintain 80% total incombustible content in active mining areas require the schedules for respirable dust sampling and rock dusting to intermix. This raises concerns about the amount of rock dust that potentially is included in the sampler weight gain. Additionally, the respirable dust maximum was lowered from 2.0 mg/m3 to 1.5 mg/m3 (effective August 1, 2016) increasing concern that rock dust contamination may be an issue. Currently, the acceptable practice is to apply administrative controls such as keeping the miners upwind during rock dust application or to schedule rock dusting during a maintenance shift when the number of miners present is lower. NIOSH’s research examining the quality of rock dust has led to the development of hydrophobic rock dusts."

Jan 1, 2017

By C. C. Jobes

Operating large face equipment, such as continuous mining machines, is one of the most basic and most dangerous elements of an underground coal mining operation. The operator usually performs cutting and tramming tasks in a restricted workspace with reduced visibility. During the execution of these tasks, operators often cannot see all of the locations needed to safely operate the continuous mining machine (CM ), which has sometimes resulted in accidents. In an effort to prevent these accidents, researchers at the National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Laboratory, examined the continuous mining machine operator?s current information cues, or visual attention locations, so that risk of injury relative to the task, equipment and workplace environment can be evaluated in the future. The eventual goal is to develop interventions to enhance the information cues, and thereby increase the safety and health of machine operators. This paper details the operator interview process, determination of visual attention locations (VALs) and simulation of various mining scenarios.

Jan 1, 2011

By V. Svalbonas, S. M. Jones, A. Boughey

In June 1998, the world's largest grinding mill, the 40 ft (12.2 m) diameter 20 MW Cadia gearless SAG mill, was commissioned. This was a leap of over40% above the largest operating SAG mill. A significant saving in capital cost gave the incentive necessary for a single mill line at Cadia, resulting in the selection of the 40 ft (12.2 m) diameter mill. Now, after 18 months of operation, this paper will review the significant items involved in the development, design, manufacture, installation, and operation of this mill.

Jan 1, 2000

By Howard W. Adam

Mill length was the primary variable investigated in an autogenous pilot mill circuit. The 5-1/2' diameter mill had both pebble ports and 1/2" wide slotted grates. The plus 1/2" mill product was crushed in a cone crusher and returned to the mill feed along with the minus 1/2" plus 4 or 6 mesh fraction. Tests were run with a short mill, inside length of 26-3/8", or diameter-to-length ratio of 2.50 to 1. The same mill was then lengthened to 48-3/8", diameter-to-length ratio of 1.36 to 1. The effect of mill length on circuit product characteristics was studied. Results show that (1) circuit throughput or grinding rate is lower per foot of mill length in the longer mill, (2) the long mill product is finer than the short mill product, and (3) KWH per ton of circuit product is slightly higher with the longer mill; however, KWH per ton of minus 200 mesh material (finer fraction) produced is essentially the same in the long mill as the short mill, It is not known whether the relationships found for the pilot mill are valid for commercial size mills.

Jan 1, 1973

By S. M. Carpenter

In an ever increasing ?carbon? society; management and growth will be measured by one?s carbon footprint (or output). Industries, especially mining, are under an ever increasing scrutiny of carbon, water and environmental mandates. These mandates are measured by the emissions caused by the combustion of fossil fuels. The fundamental building-block for any business, strategic or management decision must be based on an understanding of one?s ?footprint?. The scrutiny is most stringent for the commodities producers, power producers & fuel suppliers in the energy market. An overview of currently acceptable standards, application of those standards and nuances experienced in collecting the data necessary to analyze and complete a company?s carbon footprint will be presented. A lack of regulation, the fear and expectation of new and ever constraining rules, regulation and a change in the federal administration is a recipe for uncertainty in the marketplace.

Jan 1, 2010

By B. C. Paul, R. Q. Honaker, K. Ho

Recent research has shown that froth flotation is not effective at treating fine coals (-28 mesh) containing a large portion of middling particles. Due to their relatively large density differences, middling particles can be separated more efficiently using gravity-based processes. The ability of gravity separators to treat fine particles has been limited by the lack of particle inertia relative to the surface drag forces. However, particle inertia can be enhanced by the application of a centrifugal field. A commercial-scale centrifugal Falcon concentrator capable of treating a mass flow rate of greater than 1 tph continuously has been used to evaluate its feasibility for treating fine coal as an alternative to froth flotation. Tests conducted on a -28 mesh fine coal circuit feed have found the Falcon concentrator to be very effective at cleaning the 28 x 325 mesh size fraction. For an Illinois No. 5 coal sample, the ash content was reduced in the 100 x 325 mesh size fraction from about 18% to 8% while achieving a high combustible recovery value of nearly 97%. In addition, the total sulfur content was substantially decreased from 2.6% to 1.7%. The effects of the critical operating parameters on separation performance have been studied and their values optimized.

Jan 1, 1995

By Charles T. Steuart

The Arkansas Novaculite of Devonian and Mississippian age is the most distinctive formation in the central Ouachita Mountains of Arkansas from the standpoint of both topography and lithology. The formation typically forms precipitous, narrow ridges (hogbacks) which reflect the steepness of dip and the resistance and thickness of the rock units. The Arkansas Novaculite varies from less than 200 feet thick in the north to locally over 800 feet thick in the south and outcrops over an east-west distance of 360 km (200 miles) in the Ouachita Mountains of Arkansas and Oklahoma. Most of the rocks of the formation are highly siliceous with novaculite predominating, and lesser quantities of chert, siliceous shale, conglomerate and rarely sandstone. Novaculite is commonly defined as a homogeneous mostly white rock, translucent on thin edges with a dull to waxy luster and composed almost entirely of microcrystalline quartz. The word novaculite comes from the Latin word novacula, meaning razor hone. This term was first used by Richard Kirwan in his mineralogy text of 1784. The origin of novaculite remains controversial but we believe it was a primary silica derived mostly from the alteration of submarine volcanic-rich materials, with numerous fine biogenic components and some minor clastics (derived mostly from foreland facies via turbidity currents) and deposited as an amorphous siliceous ooze in the deep Ouachita trough. It was subsequently converted to microcrystalline quartz during diagenesis by the compaction of the overlying rocks and the intense Late Paleozoic Ouachita Mountain tectonism. In the central and southern portions of the region three divisions of the formation have been defined: a Lower Division predominantly of light-colored novaculite; a Middle Division of interbedded dark chert and shale; and an Upper Division of massive often calcareous novaculite. In the northern exposures the formation is thinner and contains more black chert and shale, chert-shale conglom¬erate, sandstone and less novaculite. The massive novaculite of the Upper and Lower Divisions is a source of high purity silica (99+%). Indians were the first to use novaculite. They made their various tools and hunting implements from the weathered broken rock until they learned the quarrying techniques. The first white men in the area recognized the use of novaculite for sharpening their tools and knives: previously whetstones were obtained in small quantities from Europe. To this day whetstone is quarried mostly in areas which the Indians and possibly the Spanish previously worked. Some of the current mining practices have changed very little from those of the early quarryman. In areas where the novaculite of the Upper Division is poorly cemented, this friable tripolitic material has found applications in such uses as an abrasive, as a filler or extender in paints, plastics and other purposes. Some of the dense novaculite is suitable as a filler in fire bricks and also in plastics. Because some of it has the tendency to decrepitate when heated not all novaculite can be used for these applications. Several quarry operators are crushing novaculite for road, concrete, and other aggregate. This use was formerly rather limited due to the abrasiveness of the novaculite on crushing and screening equipment. Further potential uses of novaculite are speculative but include application of high purity silica in the production of silicon metal for solar cells, seed or "growing", and fusing quartz for electronics.

Jan 1, 1985