Search Documents

By M. J. Nicol

The kinetics of the dissolution of colloidal silver in aerated cyanide solutions has been investigated with the aim of developing a relatively rapid and convenient method for monitoring the ?leaching power? of solutions typically used in the cyanidation process. Experimental results obtained are consistent with an electro-chemical model, in which the mixed potential is set up in the active region of the polarization curve for the anodic dissolution of silver, giving rise to a rate of dissolution which is controlled by the rate of mass transport of either cyanide or oxygen to the surface of the silver. The rate of dissolution of colloidal silver was found to respond to variations in the reactant concentrations in a similar manner to gold (and silver) in a typical free-milling ore. The use of this technique for the monitoring and control of the cyanide leach process is discussed.

Jan 1, 1998

By Dale S. Preece

The computer program. DMC Qistinct Motion &de), which w&s developed for simulating the rock motion associated with blasting, has been used to study the intluence of row delay timing On rock mOtiOn. The munerical simulations correspond with field observations in that vmy short delays (< 5Oms) and vety long delays(> 3oOms) produce a lower percent-cast thao a medium delay (100 to ZOO ms). The DMC predicted relatio&lp between row delay timing and percent-cast is more complex than expected with a dip in the auve where the optimum timing might be expected. More study is required to gain a full undasranding of this phenomenoo.

Jan 1, 1994

By Waldemar W. Koczkodaj, William O. MacKasey

Abstract - A consistency-driven pairwise comparisons method for mineral potential assessment is presented, using a simplified case of volcanic-associated massive sulfide type deposits as an example. Geological, geochemical, and geophysical criteria are considered on two levels: local and regional. The local geological criteria are subdivided into stratigraphy, lithology, alteration and/or mineralization, and structure. The concept of geomerit index and a procedure for computing this index are introduced. The method of consistency-driven pairwise comparisons can be combined with other quantitative and qualitative assessment methods, enhancing them by incorporation of nonmeasurable geological criteria (e.g., stratigraphy or lithology) and by computation of weights. The consistency-driven approach allows experts to refine at-times subjective judgments concerning exploration and land-use planning, and contributes to the improvement of mineral-potential assessments.

Jan 1, 1997

By Napitupulu P

PT Freeport Indonesia currently operates a concentrating complex capable of milling 127 000 metric tonnes per day of copper and gold hearing ore. The facilities consist of both a conventional crushing, ball mill and flotation circuit and a SAG, ball mi

Jan 1, 1997

By Joseph D. Lessard

A process simulation of the conversion of molybdenum disulfide concentrates into molybdenum dioxide via the Looping Sulfide Oxidation process has been performed using HSC 7.1 thermodynamic software. By decoupling molybdenite conversion and molybdenum oxidation, Looping Sulfide Oxidation changes the paradigm by turning molybdenite processing into an energy generator while producing a molybdenum dioxide, which has a lower vapor pressure and lower oxygen content than molybdenum trioxide. The Looping Sulfide Oxidation process selectively produces molybdenum dioxide over molybdenum trioxide. This process uses a stoichiometric mixture of oxygen and molybdenum trioxide as oxidants in the conversion of the molybdenum sulfide to the molybdenum oxide. The model simulates the two reactor scheme required by Looping Sulfide Oxidation and incorporates thermodynamic equilibrium simulations performed in FactSage 6.3.1 thermodynamic software. Energy capture is also maximized with heat exchanger systems to transfer heat released in reactions to preheat air.

Jan 1, 2014

By Anthony (Sam) J. S. Spearing

Backfilling using coal waste is not a novel means for waste disposal throughout the world; yet, backfilling using a high density (paste) backfill is relatively new, except in Germany and Poland. One of the main benefits of a high density backfill, as opposed to a low density (slurry) backfill, is that, if placed at a low permeability and low moisture content, the risk of water table contamination can be relatively low. In addition, if paste backfill can be placed cost effectively, environmental benefits are huge because the surface impoundment footprint can be greatly reduced or even eliminated. This is especially true in room-and-pillar applications. In its current state, backfilling is considerably more costly than surface disposal. This is mainly because paste, as opposed to slurry, significantly increases backfill placement costs; however, this could be offset by increasing the achievable extraction rate. Overall, such a system could potentially improve the public?s image of coal mining in the US for a myriad of reasons. This paper discusses a proposed backfill system for a typical room-and-pillar coal mine in the Illinois Basin of the US and clearly shows the technical advantages, although costs are still higher with fill. The cost differential will likely reduce over time, in favor of the backfill option, as costs of traditional surface disposal increase, due mainly to ever-restrictive disposal regulations.

Jan 1, 2013

By J. A. Mielczarski

Surface properties of minerals could be modified selectively and very specifically by adsorption -desorption (dissolution) processes. This requires a monitoring and control of the outermost surface layer at a molecular and atomic level. The nature and structure of self-assembled submonolayers and monolayers at the interface of minerals were studied by infrared reflection spectroscopy. The external reflection spectra of the adsorbed monolayers on any type of minerals: transparent, opaque or non-transparent, recorded at different angles of incidence and for two polarizations are an excellent source of information about the nature and surface distribution of the adsorbed species. The developed method allows to obtain detailed information at a molecular level about the adsorbed surface species. By combination of the simulated and experimental data, the qualitative description of the adsorbed species as well as quantitative evaluation of orientation and the thickness of the adsorption layers were obtained. This fundamental knowledge allows to determine the mechanisms of surface phenomena which govern selective separations. Examples of different surfactant - mineral systems and industrial applications will be discussed.

Jan 1, 2000

By John Latilla

Exxaro Mining?s Matla Coal situated in Mpumalanga, South Africa operates two shortwall faces on the No 4 and No 2 seam while the No 5 seam has also been longwalled in the past. Severe strata loading events have lead to a number of serious roof falls on the wall face (facebreaks) resulting in safety threats as well as considerable production losses. In 2002 the No 4 seam shortwall suffered a facebreak restricted mainly to the tailgate side of the mining panel due to a thick, near surface dolerite sill not breaking properly. This was partly due to the premature suspension of longwalling in the overlying No 5 seam. The resultant overloading lead to severe pillar damage and subsequent bord collapse. Surface pre-split blasting was successfully used to relieve the pressure as well as to pre-condition the dolerite above the following two panels. The shortwall on the No 2 seam has experienced mid-face loading due to No 4 seam chain pillars lying over this area and creating a secondary cantilever effect. Pre-split blasting of the solid rock above the No 4 seam pillars has resulted in a significant reduction in the number of facebreaks. The panel layout of the No 2 seam was subsequently changed so that the chain pillars on both the No 4 and No 2 seam are superimposed whereas previously they were offset.

Jan 1, 2007

By H. G. Denkhaus

Please allow me the temerity to reply to your reply to my contribution as follows: A fracture is brittle if plastic deformation is absent or, conversely a fracture is ductile if plastic deformation is present. Consequently, brittleness is specified by the degree of plastic deformation at fracture. This is the generally accepted definition. If other material properties (e.g. the quorient or the product of the uniaxial compressive and tensile strengths) under certain conditions are influenced by brittleness, or brittleness by them, these should not be called brittleness. If the one or the other author does that, he simply uses imprecise language. Even your remark, that ?Inyang and Pitt (1990) stated that the ratio of the compressive strength (sc/st) is directly proportional to brittleness?, confirms that the two quantities are not considered the same. For example:? The well known definition that a material is linear?elastic if the strain is directly proportional to the stress?does not mean that stress (measured in MPa) and strain (measured in %) are the same thing.

Jan 1, 2003

By Jan E. Nesset, Phillip J. Mackey, Joo Y. Kim, Giovanni Di Prisco, André R. Laplante

Understanding the appropriate gold recovery to associate with copper recovery when assessing laboratory testing on porphyry deposits is often complicated by several factors including variable and/or complex mineralogy, and the variability contributed by the low Au content of the various flotation products. As a result, gold recovery is often underestimated and the value contributed by the gold to project economics is less than it should be, a problem that could influence overall project viability. Typically, for these types of deposits, the gold recovery is found to be lower than the copper recovery. In this unique project, having the objective of seeking a better understanding of gold recovery relative to copper recovery, mill feed samples from a selection of six operating world-class Cu-Au low-grade deposits were collected along with the mill metallurgical results for the corresponding sample periods. The samples were subjected to laboratory flotation tests, as well as the Laplante gravity recoverable gold (GRG) test, mineralogical assessment and cyanidation leaching. The aim was to better understand the copper and gold recovery relationship, the links between laboratory and plant flotation performance, the influence of mineralogical differences, and the potential for enhancing gold recovery by gravity recovery techniques. A new correlation of copper and gold recoveries based on the results is presented in the paper. The results showed that the link between copper and gold recoveries established in the best laboratory tests were maintained in the plant results, and further, that the potential for improving Au recovery by gravity or flash flotation methods is directly proportional to the amount of gold greater than 75 microns.

Jan 1, 2005

By Richard J. Mainiero

The Bureau of Mines has developed a prototype nonincendive explosive rock-breaker charge that can be fired unconfined in underground bituminous coal mines without the danger of igniting a flammable atmosphere that might be present. At present, unconfined shooting in underground coal mines is prohibited, but there are situations where the use of such shots would yield an overall improvement in safety. The charge consists of l-1/2 lb of permissible water gel explosive in the form of a short cylinder 7 inches in diameter and 7/8 inches high, surrounded by a l/2-inch-thick layer of damp salt, and encased in latex rubber reinforced with cheese cloth. The latex rubber housing provides a charge package that is strong enough to resist rough handling yet is pliable enough to conform to an irregular stone surface. A charge of this shape was found to be more effective at breaking rock than charges with lined or unlined cavities. Incendivity tests in a gallery have shown that the prototype charge will not ignite a flammable methane-air atmosphere when fired. Rock- breaking tests made with limestone boulders indicate that the charge will satisfactorily break stone slabs weighing 1 to 2 tons, and that two or more charges might be effective for slabs weighing up to 10 tons. In cooperation with the Mine Safety and Health Administration (MSHA), a test protocol for the certification of these charges as "permissible" for use in flammable atmospheres is being developed.

Apr 1, 1982

By J. P. Theron

Paper written on project work carried out in partial fulfilment of Phd.(Process Engineering) degree Process modelling is an essential element in the development of advanced (model-based) process control systems, accounting for up to 80% of the cost of development. Often, models based on historic process data are the only viable option when dealing with processes that cannot be modeled cost-effectively from first principles. Despite major advances that have recently been made in the field of nonlinear process modeling, some basic idea of the dynamic behaviour of a process system is important prior to system identification. While many process systems seem unlikely to be linear, the possible nonlinear aspects of their dynamics are not necessarily supported by the data. This may have significant implications for subsequent system identification or interpretation of the data. For example, it is quite possible that an underlying nonlinear deterministic signal may be obscured by a high degree of measurement or process noise, to the extent that it may be critical in the choice of model to fit to the data. The method of surrogate data analysis has recently been proposed as a means to classify the underlying dynamics of complex systems, and in this paper the use of Fourier transform surrogates to classify process systems is explored. Keywords: modelling, process control, simulation, surrogate data analysis, nonlinear systems.

Jan 1, 2004

By Clifford B. Farris

Introduction Shale Mining Problems The mining problems an oil shale operator will face are largely determined by the process. Candidate oil recovery processes are surface (above ground processing of mined oil shale), modified in situ (underground with some shale removed), and true in situ (completely underground with no shale removed). The shale removed for modified in situ (MIS) is generally processed by surface techniques. The mining problems are different for each category. Fig. 1 depicts the diversity of western shale deposits. Mining for surface operations will employ underground mining techniques in common use but the scale will be larger. A typical oil shale operation is expected to require 75,000 to 250,000 st (68 000 to 226 800 tons) a stream day of crushed oil shale. This is above the upper limit of current mining operations. Major problems include: (1) lack of good engineering design properties for oil shale, especially when interbedded with saline minerals at depths below 1,000 ft (305 m); (2) presence of water, hydrogen sulfide, and methane in some areas; (3) necessity for mine disposal of as much retorted oil shale waste as possible; and (4) control of environmental impacts of mining. Portions of the oil shale deposits in Colorado, Wyoming, and Utah and significant portions of the Devonian shales in the eastern U.S. are adapted to surface mining. No major technological problems are apparent outside overburden thicknesses up to 1,000 ft in the West. However, numerous political and environmental difficulties have arisen. One major oil shale developer cancelled a planned surface mining operation and currently is pursuing a modified in-situ plan. The eastern shales are closer to the surface than the western, but suffer from many of the same environmental and political problems. Modified in-situ operations face much more severe mining problems than surface efforts. Because the mined stope (called an in-situ "retort" by processors) acts as a retorting process vessel subject to gas flow, combustion, and temperatures between 1,500° and 2,000°F, mining is under highly restrictive limitations. This processing method involves removing between 20 and 40% of the shale deposit and then blasting the roof and walls into the mined space, where the oil is recovered by retorting. Major problems are: (1) swell factor severely limited; (2) need for consistent size distribution of blasted shale; (3) even filling of stope (in-situ retort) by blasted shale with consistent permeability throughout; (4) scaleup of blasting techniques, after optimization; (5) protection of retort pillars and roof during and after retorting; (6) prevention of groundwater percolation; (7)use of ANFO explosive in wet holes; (8) disposing of surface-retorted shale waste in stope; and (9) restoration of site. True in-situ operations are less well developed than surface or MIS processes. No actual mining is done, as the true in-situ processes generate permeability in the highly

Jan 9, 1980

By Clifford B. Farris

Introduction Shale Mining Problems The mining problems an oil shale operator will face are largely determined by the process. Candidate oil recovery processes are surface (above ground processing of mined oil shale), modified in situ (underground with some shale removed), and true in situ (completely underground with no shale removed). The shale removed for modified in situ (MIS) is generally processed by surface techniques. The mining problems are different for each category. Fig. 1 depicts the diversity of western shale deposits. Mining for surface operations will employ underground mining techniques in common use but the scale will be larger. A typical oil shale operation is expected to require 75,000 to 250,000 st (68 000 to 226 800 tons) a stream day of crushed oil shale. This is above the upper limit of current mining operations. Major problems in¬clude: (1) lack of good engineering design properties for oil shale, especially when interbedded with saline minerals at depths below 1,000 ft (305 m); (2) presence of water, hydrogen sulfide, and methane in some areas; (3) necessity for mine disposal of as much retorted oil shale waste as possible; and (4) control of en¬vironmental impacts of mining. Portions of the oil shale deposits in Colorado, Wyoming, and Utah and significant portions of the Devonian shales in the eastern U.S. are adapted to surface mining. No major technological problems are apparent outside overburden thicknesses up to 1,000 ft in the West. However, numerous political and environmental dif¬ficulties have arisen. One major oil shale developer cancelled a planned surface mining operation and currently is pursuing a modified in-situ plan. The eastern shales are closer to the surface than the western, but suffer from many of the same environmental and political problems. Modified in-situ operations face much more severe mining problems than surface efforts. Because the mined stope (called an in-situ "retort" by processors) acts as a retorting process vessel subject to gas flow, combustion, and temperatures between 1,500° and 2,000°F, mining is under highly restrictive limitations. This processing method involves removing between 20 and 40% of the shale deposit and then blasting the roof and walls into the mined space, where the oil is recovered by retorting. Major problems are: (1) swell factor severely limited; (2) need for consistent size distribution of blasted shale; (3) even filling of stope (in-situ retort) by blasted shale with consistent permeability throughout; (4) scaleup of blasting techniques, after optimization; (5) protection of retort pillars and roof during and after retorting; (6) prevention of groundwater percolation; (7)use of ANFO explosive in wet holes; (8) disposing of surface-retorted shale waste in stope; and (9) restoration of site. True in-situ operations are less well developed than surface or MIS processes. No actual mining is done, as the true in-situ processes generate permeability in the highly

Jan 1, 1980

By Edward F. Redente

Several research projects have been conducted in the western United States to determine the optimum soil replacement thickness for reconstruction of rangeland and cropland. However, the information gained from these studies tends to be site-specific and not broadly applicable. Moreover, the possible interaction between soil thickness and mechanical and fertilizer manipulation of the overburden has not been adequately studied. To meet these information needs, research was initiated at Trapper Mine in northwestern Colorado in 1980 to study vegetation response to soil thicknesses of 15,30,45, and 60 cm and five manipulations that included disking, ripping, and fertilizing. All crops were harvested at peak standing crop and then weighed in the laboratory. Wheat grain yields were highest when soil thickness was 45 cm and the soil and overburden were ripped. Alfalfa yields appeared to be highest when overburden was disked and fertilized and soil was replaced to a thickness of 60 cm. For range vegetation, standing crop biomass was highest when overburden was ripped and soil was replaced to 60 cm thick. However, optimum performance was obtained from the maximum number of species and life forms by disking overburden and replacing 15 cm of soil. The performance of most range plant species has improved over the three years of the study. When the results of this study are compared to the results of other soil thickness studies, we can conclude that selection of management practices should be influenced by local climate, local soil and overburden conditions, type of crop or vegetation to be grown, and specific management goals for that crop or vegetation.

Jan 1, 1984

By D. François-Bongarçon

When it comes to sampling theory, a bad sampler is a bad sampler, no matter what, and a sampler is either bad or good. It also is of critical economic importance to tell and understand the difference, especially in a metallurgical plant. In this paper, the grand principles of Sampling Theory are first recalled, then the most popular types of sample cutters for plants are critically reviewed. It is concluded that the industry has a lot of progresses to make in that direction, although improvements usually pay for themselves very quickly.

Jan 1, 2002

By Michael Amick, G. Swan, R. Hill, C. Pritchard

Falconbridge, a major base metal producer in the Sudbury Basin of Ontario, identified a need to find a safe and cost effective replacement for welded-wire mesh used to support loose ground during underground nickel mining. Falconbridge took a methodical approach to the concept of a spray-on liner as a screen replacement proving the strength characteristics of the liner as a safe, cost effective, and suitable method of supporting ground. Compact, hydraulic mixing and spraying equipment have been developed and are in use at the Fraser mine. The Tekflex material has been approved as a wire-mesh replacement and has been in use since November1998.

Jan 1, 2000

By A. G. Pasamehmetoglu, N. Celebi, K. Erarslan

A deposit evaluation system has been developed for a proposed new mine in the basin around Collolar in Turkey. It includes compositing, gridding and reserve estimation facilities and takes account of the economic value of the pit and the pit bottom elevation

Sep 1, 1991

By E. R. Packer

"The mill of Anaconda Britannia Mines is located on the eastern shore of Howe Sound, approximately 32 miles north of Vancouver, British Columbia. The mill has a daily capacity of 3400 to 3500 tons and at the present is treating chalcopyrite-pyrite ore from which only the copper mineral is concentrated. For a clear conception of concentrate filtering and shipping practice at Britannia perhaps a bit of past history should be related.For many years the mill concentrated copper and zinc minerals and intermittently a pyrite concentrate was produced. It was general practice to ship copper concentrate by towed barge down Howe Sound, across Juan de Fuca Strait and thence down Puget Sound to Asarco's smelter at Tacoma, Washington. Zinc concentrate was loaded in hopper bottom rail gondolas spotted on rail barges and towed to rail heads in Vancouver, thence by rail to Anaconda Reduction Works in Great Falls, Montana. Most of the pyrite produced was shipped by ocean freighters to Japan and Taiwan with an occasional barge load of 2000 to 4000 tons to nearby customers in Vancouver and the state of Washington.In recent years, because of smelter shut-downs for one reason or another, mostly strikes, a considerable amount of copper concentrates has been shipped by ocean freight to Japan and in 1971 several lots were loaded in gondola cars and shipped by rail to the Anaconda smelter in Anaconda, Montana, because Asarco's smelter was forced by municipal and state anti-pollution laws to limit the amount of S02 emission from the smelter stacks. Zinc concentrate production was halted in the early part of 1Y70 because of zinc depletion in the ores and pyrite production was stopped in May, 1971, because of a lack of markets.Filter equipment in the Britannia mill consists of conventional disc vacuum filters and reciprocating vacuum pumps. The copper concentrate filter was installed in 1923 as a 6 x 8'6"" American disc type manufactured by United Filter Corporation, The zinc concentrate filter, now converted as a spare for copper concentrates, is also a 6 x 8'611 American disc manufactured by Traylor Engineering and Manufacturing Company and was installed the same year. Formerly, there were, in addition, two 4 x 6' disc filters for pyrite and two 6 x 6' disc filters to de-water bulk flotation concentrates ahead of the regrind mills. Installed vacuum pumps were two Ingersoll Rand 22"" x 811 and one 22"" x 9"". One of the smaller machines has since been scrapped.At the time of the writer's transfer to Britannia in 1965, the entire filter system was operating as a unit using two vacuum pumps and a common filtrate tank with a 2"" SRL filtrate pump for five operating filters. The regrind and pyrite filters were in continuous operation and the co11p('r concentrate filter alternated with the zinc concentrate filter because both copper and zinc concentrates were transp0rted to storage by the same conveyor belt."

Jan 1, 1972

By William R. Yernberg

Most citizens take it for granted, but minerals produced in the mines of the western United States, including Colorado, are crucial to nation’s standard of living and quality of life, said Colorado’s Gov. Bill Owens in his welcoming remarks at the 106th National Western Mining Conference. The conference, which was organized by the Colorado Mining Association (CMA), was held Feb. 4-6, 2004, in Denver. Attendance was425, up substantially from last year’s meeting. The meeting included the CMA annual membership meeting as well as the CMA chairman’s and president’s reports. The meeting also included awards presentations in which companies were recognized for their efforts in pollution prevention, health and safety, and reclamation. The conference also included a tradeshow.

Jan 1, 2004