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By Charles B. Carpenter

For many years, studies of ground movement and subsidence accompanying subsurface mining operations have been part of the research program of the Bureau of Mines. Periodic observations by engineers of the Mining Division of the Bureau of man-built structures beneath which mining operations are conducted offer indisputable evidence of subsidence in the form of creeks in masonry structures and fractures and depressions in tie surface of the earth. As the removal of subsurface rock and earth material by mining, especially by the room-and-pillar method, is equivalent to withdrawing some of the foundation of a building, subsidence of the formations above, the mining levels in certain air-as is easily understood as a gravitational adjustment of the overlying earth formations.

Jan 1, 1940

By J. E. Forciea, O. E. Palasvirta, L. G. Hendrickson

AH pilot and commercial plants working with Mesabi Range taconite employ wet magnetic separation. Progress is being made with a dry magnetic process, but this has not yet been applied to taconite except in the laboratory and pilot plants. Flowsheets in all five plants are similar, including multiple stages of grinding, each followed by magnetic separation, which rejects a finished tailing. The flowsheet in Fig. 1 is used in the preliminary and commercial plants of the Erie and Reserve mining companies and in Unit C of Oliver's Pilotac plant. At Erie the desliming operation is omitted. In the Reserve plants two ball mills are used with each rod mill. Pilotac uses flowsheet 2 in Unit A-B and has also tested flowsheet 3. Principal differences in the three flowsheets are the number of grinding stages and the type of roughing. The terms open-circuit roughing and closed-circuit roughing are best defined by the diagrams. Special Test Data Given in Table I: For the Erie and Reserve commercial plants, Table I reflects routine conditions. Pilotac, the experimental plant, has been run with several flowsheets, including those followed at Erie and Reserve's commercial operations. Pilotac data for these last two flowsheets are similar to commercial plant results and are not repeated in Table I; statistics are given, however, for special test conditions. using other flowsheets. when the objective was to 'to extra-grade concentrate, Variations Among Taconites: Although crude ore tributary to these plants is generally classified as taconite, there are important differences in mineralogy and fineness of dissemination.

Jan 1, 1959

By Leopoldo Mariscal

El presente trabajo describe los aspectos más importantes del proyecto de Fundición de Ilo como son: la tecnología, el desarrollo de la ingeniería y construcción, el impacto económico, social, tecnológico y ambiental de su ejecución y los planes de entrenamiento y comisionado de la nueva planta. Asimismo considera entre los equipos principales: un horno de fusión en baño ISASMELT asociado a un caldero de recuperación de calor y un precipitador electroestático, cuatro convertidores Peirce Smith, dos electroprecipitadores, dos plantas de ácido, dos plantas de oxigeno, dos plantas de efluentes, una planta de moldeo de ánodos, dos hornos de limpieza de escoria, y varias plantas auxiliares más.

Sep 12, 2005

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 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 M. Scaggs, K. Phillips

"Coal Worker’s Pneumoconiosis (CWP) is an occupational lung disease caused by chronic exposure to respirable mine dust. After decades of steady decline, CWP incidence appears to be on the rise since the mid-1990s, particularly in some regions of Appalachia. Alarmingly, many of these cases have rapidly progressed to the most advanced form of CWP, referred to as Progressive Massive Fibrosis (PMF). Most of what is currently understood about respirable mine dust has been gleaned from routine regulatory monitoring, which tracks total mass concentration of respirable dust (mg/m3) and, less frequently, silica mass content. This paper focuses on the use of thermogravimetric analysis (TGA) as a way to provide basic characterization of the whole composition of the dust, allowing it to be classified into three mass fractions – coal, carbonate, and non-carbonate minerals. TGA was conducted on 59 dust samples collected by miners from eight coal mines in central Appalachia, and the results are discussed in terms of differences between mines, regions, and primary occupations. Consistent with prior results on area dust samples from some of the same mines, results of the personal samples generally show that the coal mass fraction of the dust is relatively low. Carbonate and non-carbonate minerals thus tend to make up the bulk of the dust mass, and vary across occupations and specific mines. INTRODUCTION After nearly four decades of decline, the prevalence of Coal Workers’ Pneumoconiosis (CWP, or “black lung”) in the US has been on the rise since the mid-1990s (Laney et al., 2014; Laney et al., 2010; Suarthana et al., 2011; Pollock et al., 2010; Antao et al., 2005; Blackley et al., 2016). Particularly alarming is the number of cases of progressive massive fibrosis (PMF), which is the most advanced form of the disease (Pollock et al., 2010; Antao et al., 2005; Blackley et al., 2016; Laney et al., 2017). A recent study by Laney et al. (2017) observed 192 US coal miners participating in the Coal Workers’ Health Surveillance Program (CWHSP) who had been diagnosed with PMF since 2000. Of the 163 (85%) that had a normal radiograph on file to use as a baseline, 27 (17%) of these individuals had progressed from a normal radiograph to PMF diagnosis in less than 10 years. Moreover, 162 (84%) of the individuals in that study worked in KY, WV or VA, and 169 (88%) had only ever mined underground. Blackley et al. (2016) also reported on a group of 60 PMF cases that were discovered by a single black lung clinic in eastern KY. Since seeking care at such clinics and participation in the CWHSP are voluntary, and could be influenced by a number of factors, these recent reports may well overestimate the degree of resurgence in severe disease (i.e., versus disease that was previously under-reported). Even so, they highlight a critical need to better understand the cause(s) of disease development and progression – such that effective interventions can be devised."

Jan 1, 2018

By V. M. Shick

For practical purposes of the use of information resources in the field of geomechanics and mine surveying with accepted mining technology in mines, the authors have developed the packaged software programs of the survey-geomechanical information system with database objects of mine field. This system enables to execute the graphical representation of workings layout in preset scale, axonometric projection, the zones of higher ground pressure: program packages for calculations of rock pressure manifestations and for selection of suitable support facilities for the permanent, development and active workings and vertical shafts based on the information resources of the State Research Institute of Mining Geomechanics & Mine Surveying (VNIMI). The program packages are applied at coal mines in Russia and in Kazakhstan. The profitable operation of coal mines can be reached only by the combined optimal engineering decisions in mine working's laying-out and their reliability and safety at the stages of their designing and exploitation, and with minimal harm of the environment as well. This problem is being complicated by the fact that today the mining-practicing engineers and designers are ordinarily facing the problem " of an information barrier", when the complexity of controlling systems exceeds the potentialities of traditional management of production practice. Coal mine is a typical representative of complicated systems, because the information about geological structure, physicomechanical properties and stress-strain state of rock mass are of fragmentary character and insufficiently reliable. A mine has a developed network of interrelated workings, by the way, some of them are productive ones being subjected to control to a certain extent, and some of them are abandoned ones being noncontrollable and hazardous in rushes of water, gas, pulp and fire. The ground pressure forces cause the disintegration of rock mass growing with depth. The progress of mining operations constantly changes the geomechanical situation forming the zones of bearing pressure, stress relieving, coal falling, as well as it leads to the pulp movement on the earth surface, breaks the ground water flow, causes deformations and changes in stability of buildings, constructions and natural objects on the earth surface. One should take into account the existence of hazardous zones within the mine field, i.e. the zones of elevated ground pressure, geological dislocations and those ones under natural water reservoirs, ponds, etc. Major coal seams are prone to rock bursts, sudden outbursts, bleeding, endogenic fire. It is obvious, that in practice it is extremely difficult to account for the mentioned above factors in their interrelation.

Jan 1, 1996

By R. Patterson

Tracer gases have been utilized successfully in a variety of industries, each with specific releasing and sampling methods. The various attributes of tracer gases are dependent on the industry the tracers are utilized in. Tracers must be chemically and thermally stable, safe, odorless, detectable at low concentrations, have a low background concentration, and should not be naturally occurring in the environment if they are utilized in underground mining applications (Thimons et al., 1974). In addition, the tracer gas should be inexpensive, non-corrosive, non-toxic, easily transportable, readily attainable, and non-radioactive (Kennedy et al., 1987). Sulfur hexafluoride (SF6) met many of these above requirements and therefore was introduced as an ideal tracer gas to use in mining industry in the early 1970?s (Thimons et al., 1974). Due to the nature of underground mining including complicated geometry, irregular flows, turbulent flows, obstructed airways, and leakages it is difficult to use conventional anemometer and smoke tube techniques to accurately measure the effectiveness of ventilation controls (Thimons et al., 1974; Klinowski and Kennedy, 1991). There have been several applications of SF6 as a tracer gas in underground metal/non-metal and coal mines. Thimons et al. conducted early testing of SF6 in an underground limestone mine and determined that it is an effective technique for evaluating auxiliary fans, estimating volumetric flow rates in large areas, and measuring low flow velocities. A rapid face ventilation measurement method (FVM) utilizing SF6 was developed by the Bureau of Mines to make face measurements in underground coal mines (Timko and Thimons, 1982). When measuring the effectiveness of jet fans in dead headings SF6 was proven more effective than smoke tubes (Timko and Thimons, 1982). Experiments related to determining methane liberation in the gob were also conducted by injecting SF6 into a borehole (Timko and Thimons, 1982). Also, in an emergency situation where the gob had to be sealed due to a fire, SF6 was released to determine the effectiveness of the seals (Timko and Thimons, 1982).

Jan 1, 2011

By Steve Kral

For an industry that provides more than half of the nation’s energy needs, the U.S. coal industry still attracts negative publicity. However, the nation’s energy appetite continues to increase. And political leaders and the public are beginning to understand that alternative fuels will not be enough to keep up with that appetite. Does that mean the nation will now embrace the coal industry? No, according to speakers at the Rocky Mountain Coal Mining Institute (RMCMI) meeting. The industry still needs to sell the public on coal’s advantages over other fuels. And the industry must continue to develop technology that will allow coal to meet and exceed strict clean air and clean water regulations.

Jan 1, 2002

By M. Brozek

The constant of flotation velocity is the value characterizing the kinetics of cyclic flotation. In the statistical theory of flotation its value is the function of probabilities of collision, adhesion and tearing off the grain from the air bubble. The grain ? air bubble collision plays a key role since there must be a prior collision before the grain ? air bubble adhesion happens. The probability of such an event to occur is proportional to the relation of the grain diameter to the bubble diameter. When the grain sizes are given, it is possible to control the value of collision probability by means of the size of air bubbles. Consequently, it is significant to find the effect of physical and physicochemical factors upon the diameter of air bubbles in the form of a mathematical dependence. In the pneumo-mechanical flotation machine the air bubbles are generated by the blades of the rotor. The dispergation rate is affected by, among others, the rotor rotational speed, the amount of air transported to the flotation chamber an time and the liquid surface tension, depending on the type and number of applied flotation reagents. In the proposed paper the authors will present the distribution of air bubble diameters on the grounds of the above factors, according to the laws of thermodynamics. The correctness of the de-rived dependences will be verified empirically.

Jan 1, 2014

The Electricity Generating Authority of Thailand (EGAT) Mae Moh coal mine is an open-cut coal mine in Thailand that produces about 16 Mt of lignite annually to generate 2400 MW of electricity. The surface mine pit covers is 4 km by 7 km with mining depths ranging up to 260 m. A large pit slope is formed with the progression of the mining operation. However, massive slides in the pit slope occur often due to the existence weak planes such as faults and bedding, and the weak mechanical properties of the rocks. Hence, 200 m to 300 m boundaries of rock block including coal seams are left in front of faults in order to prevent slides and maintain the stability of the pit slope. As a result, there are significant coal reserves beneath the abandoned area along the pit slope. Moreover, the mined coal seams are very thick and their thickness range from 15 to 30 m.This paper discusses the application of multi-slicing highwall mining system with stowing to this very thick coal seam left around large pit slopes by means of numerical analysis.

Dec 6, 2010

By Robert D. Coyle, David L. Emmons

Introduction The Cove gold-silver deposit is located in Lander County, NV about 50 km (30 miles) southwest of Battle Mountain, NV (Fig. 1). The deposit is in the north-central part of the Fish Creek Mountains within the McCoy mining district. Gold was first discovered in the McCoy district in 1914 by Joseph H. McCoy (Vanderburg, 1939). From 1928 to the early 1930s, minor production occurred from shallow underground workings. Total gold production was less than 311 kg (10,000 oz; Stager, 1977). The district was inactive until the mid-1960s when it was explored by Bear Creek Mining, Summa Corp., Houston Oil and Minerals Corp., Gold Fields, and Tenneco Minerals. Tenneco began a detailed reevaluation of the McCoy deposit in the fall of 1984. Tenneco's decision to place the deposit into production was based on a geological reserve of 8.7 t (280,000 oz) of gold (Kuyper, 1987). Subsequent exploration and development drilling of the McCoy skarn deposit has more than doubled the mineable skarn reserves to 19 t (615,000 oz) of gold. In September 1985, Tenneco began development work on the McCoy gold-skarn deposit. The project is an open-pit, heap leach mine. The first gold was poured in April 1986. Echo Bay Mines acquired Tenneco's precious metals properties in October 1986. The mining operation and district exploration started by Tenneco is continuing under the Echo Bay's ownership. The Cove deposit was discovered in January 1987 and production began in February 1988. The deposit will begin as an open-pit, heap leach operation. It will be converted into an open-pit and underground mine with a 9-kt (10,000-stpd) mill. Geologic setting The Cove gold-silver deposit is situated on the east flank of the Fish Creek Range. Surface elevations range from 1460 to 1680 m (4800 to 5500 ft). The deposit is 1.6 km (1 mile) northeast of the McCoy gold-skarn deposit. The Cove deposit is hosted by the Augusta Sequence of Triassic age. Three formations of the sequence are mineralized at the Cove. In ascending order they are the Favret, Panther Canyon, and Augusta Mountain formations. The Favret formation is a gray, locally silty limestone that is commonly fossiliferous. The base of the formation is not exposed. Exposed and drilled intervals are more than 60 m (200 ft) thick. Conformably overlying the Favret formation is the Panther Canyon formation. This formation is 215 m (700 ft) thick and consists of a siliclastic and carbonate sequence of conglomerate, quartzite (sandstone), mudstone, limestone, and dolomite. It is a distinctly coarsening-upward sequence of rocks. The top of the unit is conglomerate with chert and quartzite clasts up to 150 mm-diam (6 in.-diam). The Augusta Mountain forma-

Jan 8, 1988

Three stages are involved in the complete design and evaluation of an open cut mine. These are:1. design of the optimu,m ultimate pit, and selectionof the optimum mill capacity,2. development of production schedules, with intermediate pit designs, and3. evaluation of the project, based on factors from stages 1 and 2, by means of discounted cash flow analysis.Stage 1 requires relatively complete information on metal distribution, metallurgical performance, and cost factors, which is used to design a series of pits, corresponding to a range of milling rates.For each milling rate considered there is a unique pit design which maximizes operating profitability. The computer outlines this design (in terms of size, shape, and location; tons and grade of ore; and tons of waste), by considering the effect on profitability of mining each block in the mineralized inventory in relation to every other block which would be affected by its removal.The computer selects only those blocks for mining which result in an overall increase in profitability, maintaining pre-determined wall slope conditions throughout.Both operating profitabilities and capital costs increase with throughput, and the two curves will combine to produce a flat peak in net profitabilities at a certain rate, with its associated pit design.Stage 2 can maximize head grades early in the life of the operation. This increases the projected present value, but there are good arguments for maintaining steady head grades throughout the life of the mine.A modification of the programme used in Stage 1 is used here.Stage 3 is a conventional discounted cash flow analysis, using factors obtained in stages 1 and 2. It can be computerised, but a manual treatment is probably just as fast overall.

Jan 1, 1970

By H. M. Breza

Recovery of phosphate concentrate has received increased attention as the existing mine and plant production capacity limitations of the Texasgulf Inc. Aurora, North Carolina Mine are reached. Improved mining techniques and mineral processing of waste streams offer a potential to increase overall phosphate production without major expansion of the Mining facility. Innovative processes have been or are being identified to maximize pit mining recovery and to minimize losses in waste streams, resulting in more effective use of the valuable phosphate natural resource. This paper will describe the various continuous recovery improvement programs being implemented to achieve this goal.

Jan 1, 1994

By D. Brunner, G. R. Baiden, H. J. Yazici

System simulation is an increasingly popular technique for analyzing and improving existing as well as newly designed underground mining operations. An engineering firm that specializes in simulation helped a major metals producer build a long-range planning model of an existing underground mine. Subsequently the team adapted this model to assess technology alternatives in the design of a new mine. The two models differ in the level of detail used for modeling the development process. This paper discusses the differences in approach between the models along with the experiences gained and challenges faced during the construction and use of the models.

Jan 1, 1999

By Richard Goodridge, Stephen Thomsqn, S Rodgers, D Tunaley

The mining, quarry and construction industries are facing’new challenges everyday. These challenges can be imposed by economic objectives or through external factors such as extreme geological conditions. Simultaneously, all mines, quarries and construction sites are facing more and more stringent environmental requirements.

Jan 1, 1998

By A. V. Z. Brink

Rock engineering risk is defined in this paper as a function of the potential ground motion; the vulnerability of the workplace; exposure of people; and a general term – quality of information. The paper describes the development of prototype software that is a combination between an expert system approach for determining overall risk assessment, a risk control recommendation and a basic GIS (Graphic Information System) approach for graphically overlying input parameters and the output risk. The expert system uses a Bayesian probabilistic approach to combine various workplace-related information, a quantified seismological environment and the exposure of underground staff to provide an overall RE risk rating. The risk assessment is dynamic in that it is recalculated each time that any of the input parameters change, for example each time a seismic event is recorded in the area of interest. The code was tested on a data set from Savuka Gold. As risk assessment is not an absolute prediction of a specific outcome, it is therefore not possible to relate to individual case studies and the reliability of this method would only be determined after an extensive period of use with appropiate back-analysis. Le risque dans le génie minier est défini dans cette étude comme une fonction du mouvement potentiel de terrain ; la vulnérabilité du lieu de travail ; l’exposition des personnes ; et un terme général – la qualité de l’information. L’étude présente décrit le développement d’un logiciel prototype qui est une combinaison entre une démarche de système expert pour déterminer une évaluation générale du risque, une recommandation pour le contrôle du risque, et une démarche de SIG (Système d’Information Géographique) pour superposer graphiquement les paramètres d’entrée et le risque de sortie. Le système expert utilise une méthode de probabilité bayésienne pour combiner des informations variées sur le lieu de travail, des données quantifiées sur l’environnement sismique, et l’exposition du personnel travaillant sous terre, pour finalement produire un classement général de risque minier (RE). L’évaluation du risque est dynamique en ce sens qu’elle est recalculée à chaque fois qu’un des paramètres d’entrée change, par exemple à chaque fois qu’un évènement sismique est enregistré dans la région. Le code fut testé sur un ensemble de données obtenues de Savuka Gold. Comme l’évaluation du risque ne constitue pas une prédiction absolue d’un résultat spécifique, elle est par conséquent difficile à rattacher à des cas individuels et la validité de cette méthode ne pourrait être déterminée qu’après une longue période d’utilisation avec analyse rétrospective appropriée. Das Gesteinstechnikrisiko wird in dieser Arbeit als Funktion einer möglichen Bodenbewegung definiert; die Anfaälligkeit des Arbeitsplatzes; das Ausgesetztsein der Belegschaft; und ein genreller Begriff - Qualität der Informationen. Das Papier beschreibt die Entwicklung einer Prototyp-Software, die eine Kombination zwischen einem Expertensystemzugang für die Bestimmung der gesamten Risikobeurteilung ist, eine Empfehlung zur Risikokontrolle und eines fundamentalen GIS (graphisches Informationssystem) Zuganges für graphisch darüberliegende Eingangsparameter und das Outputrisiko. Das Expertensystem verwendet eine bayesische Wahrscheinlichkeitsannäherung, um verschiedene mit dem Arbeitsplatz in Verbindung stehende Informationen, ein quantitativ bestimmtes seismologisches Umfeld und das Ausgesetztsein des Untertag-Personals zu kombinieren, um eine gesamte RE-Risikobewertung zur Verfügung zu stellen. Die Risikobeurteilung ist insoferne dynamisch,daß sie stets nachkalkuliert wird wenn sich irgendeiner der Eingangsparameter ändert, z.B. jedesmal wenn ein seismischer Fall im Interessensbereich aufgezeichnet wird. Der Code wurde auf einem Datenbestand von Savuka Gold geprüft. Da die Risikobeurteilung nicht eine absolute Vorhersage eines spezifischen Resultates ist, es ist folglich nicht möglich, sich auf einzelne Fallstudien zu beziehen und die Zuverlässigkeit dieser Methode könnte nur nach einer umfangreichen Benutzungsdauer mit geeigneter Postanalyse bestimmt werden.

Jan 1, 2003

By David Smith

Construction of a new transportation link frequently requires crossing under an existing highway or railroad. Although traffic diversions may permit a cut and cover structure to be built, ‘zero impact’ tunnel solutions are becoming increasingly popular. The vertical clearance between the new tunnel structure and the existing highway or tracks may be very low; sometimes less than two meters. This leaves little room for error since any ground loss can rapidly translate into surface settlement. Problems can be avoided by maintaining the stability of the tunnel face and by minimizing ground movement around the tunnel lining. This paper examines construction methods that have been used to construct short tunnels with shallow cover, and highlights factors to be considered for future projects.

Jan 1, 2005

By Jon Y. Kaneshiro, Eric Dawson, Pooyan Asadollahi, Steven Hunt

This paper provides updates to the paper published by the lead author at RETC 2011 with a summary of developments in technologies, products, and approaches to corrosion analyses of gravity sewer tunnels and microtunnels. This paper presents approaches in evaluating degradation of reinforced concrete liners. Also, the carbon footprint of conventional concrete liners and alternative “green” liners are compared and their life cycle costs are considered. A few case histories from the past decade are provided indicating the latest and emerging trends in liner protection.

Jun 13, 2023

By David Rahal, Des Erasmus, Ken Major

"Over the past twenty years there has been an increased emphasis on fine grinding in the minerals industry. This spurred the development of a range of new fine grinding equipment in the 1990s. At that time, the Knelson-Deswik mill was developed in South Africa for the pigments industry.Knelson Milling Solutions currently offers a wide range of laboratory, pilot and production scale mills. These mills bridge the gap between traditional low speed vertical mills and the high speed horizontal mills (tip speed < 3 and > 15 m/s respectively). They are designed to run at tip speeds between 10 and 12 m/s and are capable of operating with very dense grinding media. The result is a power intensity that is higher than the low speed mills and overlaps that of the high speed mills. This allows the mill to be customized for a wide range of grinding applications.A case study at Aquarius Platinum’s Kroondal Mine shows that the Knelson-Deswik technology can produce a consistent product size despite feed variations. It also shows that the throughput was proportional to the slurry density at Kroondal. The case study identified increasing the slurry density as a process change that can increase throughput and reduce the specific energy consumption.INTRODUCTIONThe increasing complexity and finer grain sizes of modern ore bodies have increased the importance of effective mineral liberation in obtaining acceptable grades and recoveries (Jankovic, Valery and La Rosa, 2003; Lichter and Davey, 2006; Napier-Munn, Morell, Morrison and Kojovic, 1996). This trend has increased the significance of fine grinding technology because the input energy increases exponentially as the required product size decreases from 100 to 10 microns (Gao and Weller, 1993a).The US Department of Energy recently provided the context for the potential energy savings in the US Mining Industry (BCS, 2007). They reported that grinding consumes approximately 494 TBtu/year. This was over double the consumption of the second highest equipment category, diesel materials handling systems (211 TBtu/yr). The proportion of grinding energy allocated to fine grinding can only be expected to increase as finer ore deposits are mined. It is therefore critical that fine grinding efficiency continue to improve through the selection of appropriate equipment and the development of best practices for existing applications."

Jan 1, 2011