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By Graham Davey

"Low speed stirred milling has been employed for many years in the metalliferous and industrial minerals industries. High speed stirred milling is a relatively new method of grinding in the metalliferous process industries. However it has been it has been in wide spread use in the industrial mineral field for over 30 years for various minerals. Many existing metallurgical operations are looking to maximize economic return from existing deposits, requiring new thinking and technologies. By combining low speed and high-speed milling fine and ultrafine grinding efficiency and operating costs can be improved.The correct selection of different fine grinding technologies is covered, when each mill is applicable and when a combination of the VERTIMILL® Grinding Mill and SMD provides the best economic solution.INTRODUCTIONUltra-fine grinding of minerals has been in wide spread use in the industrial mineral field for over 30 years. Within the last 10 years the metalliferous industry has shown interest in the ability to produce ultrafine particles, as chemical, physio-chemical and physical separation processes have advanced to be able to treat ultrafine metalliferous particles. Also as the primary mineral deposits, around the world are depleted, new more difficult deposits must be mined. Existing operations are also looking to maximize economic return from existing deposits, requiring new thinking and technologies.The traditional approach for gold containing refractory material has been to liberate the locked gold by chemically destroying the pyrite through oxidation. Roasting, pressure oxidation, and bacterial oxidation all employ various degrees of temperature, pressure and catalysis to react the pyrite with oxygen to produce iron oxide and sulfur by-products. However all of these methods are economically impacted due to specific operational added requirements and emissions controls. Pressure and bacterial oxidation have very high capital and operating costs."

Jan 1, 2006

Sishen Iron Ore Mine previously used only A-grade material (>60% Fe in situ value) from the pit for beneficiating in the DMS plant to a final product grade of 66% Fe in lump and 65% Fe fine ore. The B-grade (between 50% and 60% Fe) and C-grade material (between 35% and 50% Fe) were stockpiled separately, owing to the inability of the existing DMS plant to beneficiate material at densities higher than 3600 kg/m3. The ability to beneficiate the B-grade material at densities higher than 3600 kg/m3 was evaluated, and air-pulsed jigs were found to be techno-economically feasible and value maximizing. The beneficiation of B-grade material would add to the existing DMS production of 28 Mt/a, with no additional mining cost and only limited costs for the handling of waste and B-material. The objective of the Sishen Expansion Project (SEP), i.e. the jig plant, was to produce 10 Mt/a of saleable product with six modules to the set physical and chemical specifications by 2009. During the start of construction, it was decided to add another two jig modules to the plant to increase production to 13 Mt/a. During commissioning and ramp-up the shortcomings and advantages of the jigs were fully experienced and understood, resulting in many changes to optimize jigging performance..

Jan 1, 2014

By Taylor R. G

This paper reports a biogeochemical study of the Siberia lode of the Herberton tin field. Soil near the orebody contained high levels of Fe, Cu, Pb, Sn, As, Mld Mn. Polycarpaea spirostylis and Indigofera dominii were associated with these high levels but several other species apparently could not tolerate them. The potential of these species as indicator plants is discussed.

Jan 1, 1975

By Ian Martin

A precious metals refinery’s switch to personal computer-based, three-dimensional piping design saved many hours in the design of a South African precious metals refinery. Bateman Minerals and Industrial provided engineering, procurement and construction management services for Impala Platinum Limited-Refineries’ new $60 million refinery in Springs, South Africa. This project is one of the largest platinum refineries in the world. Bateman evaluated a new design method during this project that involved developing a three-dimensional model for the project. The new method saved time by reducing the man-hours required to generate complete project documentation, including plans, sections, isometrics and material takeoffs. The new method also saved design and construction time by allowing designers to detect clashes before construction began.

Jan 1, 2000

By Robert C. Bates

Variations in water percolation rates through saturated cohesionless hydraulic backfill (mill tailings) have been studied in relation to the many physical aspects of the system to determine the most important factors in causing these variations. A multivariable least-squares regression analysis of 135 separate tests shows that a reliable estimate of the water percolation rate through typical hydraulic backfill can be made if the bulk density (unit weight), specific gravity, and grain-size distribution are known or can be estimated. Equations for predicting percolation rate, coefficient of permeability, and seepage velocity are developed both for the range of data analyzed and for extrapolation. The prediction equations for use within the range of data studied are quite accurate, while the ones developed for extrapolation are less accurate but still give reasonable approximations of flow rates. The equations given are valid for cohesionless materials that are free of clays and micas, exemplified by classified mill tailings. The equation developed for predicting percolation rates is as follows: 1nP20 = 11.39147 + 2.853422 1n(VR X D10) + 0.1747436 VR X Cu -178.8039 D10 X D50 + 311.7034 (DSO )3, (1) where P20 = percolation rate, inches per hour at 20° C; correction factors for other temperatures are given in the text, VR = void ratio, dimensionless, D10 = effective size (diameter in millimeters of the 10-percent-finer grain size), Cu = coefficient of uniformity (ratio of the diameter of the 60-percent-finer grain size over D10), D50 = average size (diameter in millimeters of the 50-percent-finer grain size), and In = natural logarithm (log to the base e). The prediction equation for percolation rate is rather complicated, so for practical use a nomograph that simplifies the solution of the prediction equation was developed.

Jan 1, 1967

By P. Golledge, A. D. S. Gillies

An investigation has been carried on samples of three Queensland coal dusts to determine the potential explosibility of dust-gas mixtures. The explosion potential of the samples was classified by the lean and rich limits of explosibility and the limiting oxygen concentrations for each sample. Plotting of these points showed 2-dimensional flammability limit surfaces for coal dust/oxygen, methane/oxygen and coal dust/methane mixtures. From these plots the 3-dimensional flammability envelopes defining the explosibility of the mixtures were defined. The explosion limits of the coal dust/methane/oxygen system were seen to be influenced most by the explosibility characteristics of coal dust. Methane exerted a stronger influence over the explosion limits when the coal had a low volatile content

Jun 19, 1905

By W. E. Coughlin, R. L. Faverty, F. H. Lightner

Introduction The intent of this paper is to present the general strategy and method of implementation to achieve a "fast-track" mine development. The major objectives of a "fast-track" or rapid development schedule are to minimize front-end development expenditures and to realize an early cash flow from operations. The Borealis project of Houston International Minerals Corp. (HIMCO) is used as the working example to illustrate the development schedule. Borealis is a 2.3 kt/d (2,500 stpd) gold-silver heap leach operation near Hawthorne, NV, Pre-Feasibility Planning Proper early planning and identification of priority items were necessary to expedite project progress. On April 1, 1978, HIMCO leased the rights to the Borealis prospect and initiated exploration activities almost immediately. Since Borealis was showing excellent potential for mine development, an effort to clear the way environmentally was initiated during the summer of 1979. With the Borealis properties located within the Toiyabe National Forest, the US Forest Service (USFS) was recognized as the "lead" or respon¬sible agency for addressing the environmental issues. Early scoping of the environmental issues by both HIMCO and the USFS allowed HIMCO to take the initiative and address two potentially critical issues-archaeological and biological. Third party consultants, agreed upon by HIMCO and the USFS, were contracted to conduct archaeological and biological surveys. Desert Research Institute of Reno, NV, provided archaeological services, and JFL & Associates of Boulder, CO, provided biological services. These efforts began in the fall of 1979 and continued through the summer of 1980. Conservative Design Criteria By adoption of conservation design criteria, flowsheets and processing data required for detail engineering were firmly established with a minimum of impact on schedule. On Oct. 21, 1980, HIMCO formally initiated a feasibility study to evaluate the Borealis project. Four organizations were contracted for particular scopes of work: • John T. Boyd Co.: Ore reserve estimation, preliminary mine plan, and mine capital and operating cost estimation. • Bechtel Civil and Minerals: Conceptual engineering, processing capital and operating cost estimation. • Hazen Research Inc.: Metallurgical testing. • Sierra Pacific Power: Cost estimation for power supply. Metallurgical testing and conceptual engineering of both heap and agitation leach flowsheets were investigated concurrently. Numerous economic evaluations were conducted for both heap and agitation leaching at varying production capacities. The results indicated a heap leaching flowsheet treating 454 kt/y (500,000 stpy) yielded the best economics and was compatible with the "fast-track" development goal. Conservative design criteria was established to provide operating flexibility and ensure plant productivities. A summary of major design criteria is presented in Table 1. HIMCO assembled the results of the studies of the various consultants along with internally generated studies to produce the feasibility document. The decision to supply 100% equity by HIMCO rather than arrange project financing help to expedite the project. Cooperation Between HIMCO and Regulatory Agencies With cooperation and mutual trust established between HIMCO and regulatory agencies, the time required for environmental permitting was streamlined as much as practical. To expedite the required construction permits, HIMCO proposed to the USFS that HIMCO fund the total cost of an Environmental Assessment Report (EAR) and that issues be addressed at the technical level of an Environmental Impact Statement (EIS). The previous studies on the critical issues of archaeology and biology provided HIMCO with the information to satisfy the proposed approach. Houston International Minerals and the USFS agreed to have Environmental Research and Technology (ERT) of Fort Collins, CO, prepare a draft EAR for the USFS.

Jan 11, 1983

By E. Kamon

This report summarizes completed research pertaining to the reaction of human subjects exposed to Self-Contained Breathing Apparatus (SCBA) stressors during escape conditions (viz., resistance breathing, C02 breathing, hot air breathing, and static positive facepiece positive pressure breathing) and the development of an automated breathing and metabolic simulator (ABMS). Volume I contains summarizes of the studies performed under this contract. Volume II is an appendix which contains more detailed descriptions of these studies.

Jan 1, 1984

By T. W. Beck

Overexposure to respirable dust remains a widespread health hazard to roof bolter occupations in underground coal mines. Recently implemented mist drilling technology was evaluated for its effectiveness in controlling respirable dust exposures for roof bolting personnel. This work presents the findings from NIOSH field and laboratory studies comparing respirable dust levels on mist drilling roof bolter machines to dust levels measured on machines using a conventional vacuum drilling system. Gravimetric and instantaneous respirable dust samples were collected for multiple drilling cycles. These dust measurements were used to assess the potential dust control capabilities relative to conventional drilling. Controlled laboratory tests found 0.3 mg/m3 more respirable dust with mist drilling than with the conventional vacuum method. A separate field investigation of the two techniques observed higher dust levels around the mist bolting machine.

Jan 1, 2008

By G. X. Wang, R. E. Siemens, M. C. Fuerstenau, D. Chandra

Soda roasting of concentrates from Mouat, Montana, was performed in a temperature range of 450 to 650 degrees C and chromium was solubilised by water leaching at room temperature. It was found that high extraction yields of chromium were primarily dependent on the conversion of Cr3+ to Cr6+ during the roasting step, and this was enhanced significantly by simple attrition of chromite particles during this step. Gangue impurities (mainly Si) were more detrimental to Cr extraction than lattice impurities such as Al or Mg. It appears that oxidation proceeds into grains along a preferred crystallographic plane in the cubic lattice of the chromite. The effects of roasting time, temperature, soda to chromite ratio and particle size on the extraction of chromium are presented

Jun 18, 1905

By Jose Luis Sosa, Marco Surichaqui, Ramirez Marcelino

El proyecto permite obtener resultados de operación que no siempre son los esperados en cuanto a calidad y recuperación, aquí es donde destaca el programa; tiene una data que PRONOSTICA estos resultados, con el control de parámetros, corrigiendo estos resultados al valor óptimo esperado, haciendo que su empleo permita obtener en “tiempo real” excelentes resultados en cuanto a calidad y recuperación del licor lixiviado y se refleja en costos.

Sep 1, 2017

By Desiree Willis

One of New York City?s largest subway projects is under way 43 m (140 ft) beneath the surface of downtown Manhattan. The East Side Access project, more than 30 years in the making, was halted after a partial excavation in the 1970s due to a lack of funding. The project, once dubbed the ?Tunnel to Nowhere,? has been revitalized into a groundbreaking subway line that includes unique tunnel boring machines (TBM), construction methods and muck removal systems. Project overview The East Side Access project involves construction of a new 6.7-km (4.2-mile) subway line needed to relieve heavy traffic congestion between the boroughs of Queens and Manhattan. The line will serve approximately 160,000 commuters daily between Grand Central and Sunnyside rail stations. Manhattan and Queens will be connected under the East River by the 63rd Street tunnel, a submersed double-decker tube. The submersed tube consists of reinforced concrete sections barged in place on the riverbed. The tube contains operational subway lines on the top deck, while the bottom deck (the ?Tunnel to Nowhere?) will become operational when the East Side Access project is completed in 2013.

Jan 1, 2008

By J. D. Stone

This paper briefly reviews the adequacy of existing management theories and practices and the managerial proficiency or competency in the South African mining industry. The investigation revealed that existing management practices are totally inadequate to enable all employees on all the levels of the mining industry to achieve the results required from them, in all aspects, at all times. As a result, the South African mining industry is gradually losing its long standing reputation as a relative cheap, competitive, and reliable supplier of minerals to the local and global markets. According to some prominent management authors and theorists, an all-inclusive unified management theory does not exist at present. In this paper the authors summarize the main aspects of a newly developed comprehensive, practical, and integrated management method. It is believed that the application of this method would significantly improve the future performance and competitiveness of the South African mining industry

Jan 1, 2010

By T. Wettainen

Malmberget town is located in northern Sweden, approximately 70 km north of the Arctic Circle. Parts of the town overlie more than 20 iron orebodies, consisting mainly of magnetite with smaller quantities of haematite. The mine is operated by the mining company LKAB. Mining started in the 17th century, but not until the railway to the coastal city of Luleå was completed in 1888 did large-scale production commence. Around 1920, mining proceeded underground and today sublevel caving is the only mining method used. Sublevel caving causes subsidence of the ground surface, and buildings and residential areas have been relocated due to the mining activities for more than 50 years. The number of seismic events accompanied by strong ground vibrations is now increasing. In 2008 the mine received a permit from the Environmental Court of Sweden to increase production to 20 Mt of crude ore per year. A prerequisite for the permit was that the mine conducts a number of investigations regarding the environmental impact on the residents of Malmberget. One of these investigations concerned how seismicity will change as production increases and what measures could be taken to reduce inconvenience to the town residents. Today the mine possesses an extensive seismic monitoring system with more than 180 underground and surface geophones. For this study, eleven seismically active volumes in Malmberget mine were identified, and for each of them, a yearly future maximum magnitude interval was estimated based on the current production plan. Relationships between historical seismic events and measured ground vibrations in the town of Malmberget were established, and future ground vibrations caused by expected seismic events were estimated using a probabilistic approach. The outcome was the number of intervals of expected ground vibration per year and per monitoring point. Possible measures to reduce inconvenience for the town residents include blast restrictions, sequencing, and possibly preconditioning. The ultimate long-term solution is an almost complete relocation of Malmberget town. This process has recently been formalized and LKAB is taking an active part in realizing this goal.

Jan 1, 2014

By Scott G. Britton

Microcomputeranalysis has long been a technique for engineering professionals to improve the theoretical and practical design of continuous mining systems. Such work has been typically composed of modeling observed events and then introducing a variety of known elements with predicted results to compare against the results of the model. Programs written in BASIC, Cobol, Fortran or other language dominated such efforts. These programs have taken years to develop and prove out. This article explores a new management tool used daily at Tanoma Mining Co. (TMC) to track and improve continuous mining systems through the use of microcomputers and Lotus l-2-3 software. Data provided by section foreman, shift foreman, and maintenance personnel are analyzed against predetermined goals. In this way, new production targets are developed, weaknesses in the current mining systems are identified, and the results of changes are measured. The current results of this system on the productive output of TMC systems is on the order of 10% improvement. Thin seam coal mining is an industry within the broader industry of coal mining. Thin seam mining faces the same cost pressures and engineering problems as its higher-seam competitors without the advantages of moving volume per foot of extracted material to stay at an economic parity with others requires additional creativity within the management teams to extract higher productivity gains from the existing workforce and mining systems. TMC operates a deep mine in Indiana bounty, PA, about one hour northeast of Pittsburgh.

Jan 1, 1991

By D. Chetty

The characterization of platinum group minerals (PGMs) from concentrator flotation circuits provides valuable information towards understanding PGM recovery under given milling and flotation conditions. Additional mineralogical characterization also provides information on ore variability, which may affect recovery. Considering the low grades involved, automated scanning electron microscopy (SEM) characterization of PGMs has enabled relatively quick analyses, compared with older, time consuming and less accurate optical microscopy methods. Over the years, parameters, such as species, size distribution, liberation, gangue and base metal sulfide (BMS) associations, have been used to characterize the PGMs in a process mineralogical context, to aid metallurgical interpretation. This paper considers whether flotation indices determined for PGMs can be empirically validated, using initial results from analysis of PGMs in a concentrate bank from a South African concentrator treating UG2 ore from the western limb of the Bushveld Complex. The aim is to determine whether floatability is adequately described by these parameters, or whether other mineralogical factors must be considered when assessing PGM floatability, and hence accounting for recovery vs. losses to tails. The data obtained to date, show that flotation parameters (including liberation index, BMS/gangue relationships and size distribution) have merits where large changes in PGM concentration occur, as observed in the first four cells of the concentrate bank. Larger data sets, however, are required to assess floatability, particularly where concentrate cell grades are similar, as observed in the last six cells of the concentrate bank. Furthermore, the floatability indices could be enhanced by the incorporation of selected associated gangue mineral information, chief amongst these being the content and mode of occurrence of naturally floatable talc and associated orthopyroxene.

Jan 1, 2009

By Victor V. Nazimko

Multiple mining generates gob-interaction displacements. They redistribute stress m strata and obey laws of irreversibility thermodynamics. An irreversible state causes inhomogeneity of the stress distribution on the mass. A destressed zone develops along a working panel, and worked out panels are deprived of the destressing. The inhomogeneity is smoothed out during elapsed time.

Jan 1, 1996

By Ralph B. J, Sadler W. R

Thiobacillus ferrooxidans was shown to catalyse biodegradation of chalcopyrite concentrates. The process was growth associated at normal temperatures (30°C) in dilute acid solution (pH2, H2SO4) in submerged cultures. Approximately 20% of the copper dissolved in 22 days in the presence of T ferrooxidans while less than 0.6% was released when bacteria were absent. In ore column leachates, the iron and sulphur oxidizing species T ferrooxidans, ranged from I04 to I06 cells/ml while exdusively sulphur oxidizing species ranged from I02 to 104 cells/ml. T ferrooxidans predominated below pH 3 while other sulphur oxidizing bacteria favoured higher pH. Organisms were distributed vertically in ore columns according to pH differences, resulting from gradual acid consumption by gangue, during trickle irrigation.There was a sequential development of bacteria in leachates from fresh ore irrigated with water only. High pH sulphur oxidizers were always present, low pH sulphur oxidizers appeared within a week while T ferrooxidans took 50 days to show up. Routine monitoring of bacteria in dump leachates provided a qualitative indication of events in otherwise inaccessible ore bodies.

Jan 1, 1981

By B. E. Warren

Jan 1, 1965

By Dennis P. Martin, Michael M. Fitz, James E. Friant

Methods for reducing the cyclic nature of drill and blast tunneling operations have been long needed. A miniature blasting system using 10 mm (.375 in.) holes, 0.91 m (36 in.) deep, and blasting only one hole at a time makes it practical for men to work behind a shield, remaining at the face during the entire process. A prototype automated module was developed to drill, load the hole and initiate the detonation without moving from the hole. A unique cost effective gell explosive and a novel, low cost initiation method were developed.

Jan 1, 1989