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By R. E. Johnson, L. V. Araújo, B. R. Palmer, L. M. Abrantes, G. W. Warren

The behaviour of chalcopyrite - mineral specimens and a Portuguese concentrate - in 2M chloride solutions prepared from hydrochloric acid and sodium chloride, has been characterized by cyclic voltammetry. The study has shown the influence of the potential and of the presence of impurities in the reaction schemes and their relative extent. The dissolution of chalcopyrite concentrate under potentiostatic control has been investigated and found to confirm the effect of the selected potential on the surface modification/rate of dissolution. An attempt has been made to correlate the information obtained with the response of the concentrate electrode to constant current treatments.

Jan 1, 1993

By T. Zoltai

Asbestos is a generic term for industrially useful fibers recovered from exploitable deposits of the asbestiform varieties of five silicate minerals: chrysotile, anthophyl-lite, actinolite-tremolite, cummingtorute-grunerite, and rie-beekite. Asbestos and asbestiform fibers of some other minerals are known to be carcinogenic. Minerals crystallized in the asbestiform habit-are characterized by unique properties (morphology, strength and flexibility, physical and chemical durability, and defect-free surface structures). The key to the unusual properties, and health effects, of asbestiform fibers appears to be in their unusual surface structure. In contrast, non-asbestiform crystals of the same minerals, including the five so called asbestos minerals, do not have these properties and are not carcinogenic.

Jan 1, 1989

By Richard J. Ebens

The trace element geochemistry of the cherty, clay-rich carbonate residuum. Covering much of southern Missouri and adjacent parts of Arkansas was investigated during the early 1970's as part of a statewide geochemical survey of Missouri-1/2/3 The study was environmentally oriented and focused on the character of the "natural' geochemical environment of the state. A great deal of effort was made to collect samples that would represent the geochemical variability of the near-surface environment in an unbiased way. In general, this was accomplished by use of randomization procedures in both collection and analysis. Most of the sampling sites were selected randomly to prevent personal bias from entering into sample selection. In the laboratory, samples were analyzed in a randomized sequence to circumvent the effects of any systematic bias that may have entered into the laboratory procedures. Several residuum samples contained 1 000 parts per million (ppm) or more of Pb, Zn and Ba. All these samples were collected in Washington County in or near the barite district. The frequency distributions shown in figure 1 indicate just how unusual the residuum in Washington County is with regard to these three metals and copper. The shaded parts of the histograms represent the samples from Washington County. The histograms are based on analyses of 141 samples from 38 localities scattered over the subcrop of the Cambrian and Ordovician Formations of southern Missouri and northern Arkansas. Eight localities were selected randomly from over each of four bedrock units--Bonneterre Dolomite, Potosi and Eminence Dolomites, Roubidoux Formation, and the Jefferson City, Powell and Cotter Dolomites. Six localities were selected randomly from over the Gasconade Dolomite. The geochemical "background" for these elements in residuum is defined by samples from outside of Washington County (unshaded part of the histogram); lognormal distribution curves have been fitted to the corresponding parts of each histogram. Clearly, these lognormal models (curves) describe well the background

Jan 1, 1977

By Y. Tao

The professional status and characteristics of mineral processing were discussed along with the importance of innovative personnel training for mineral processing engineering. Reform ideas and models for the mineral processing engineering education system were suggested to formulate and implement new training program for the mineral processing specialty. It is suggested to strengthen engineering training practices, cultivate the culture of innovation, improve innovative education system and insisting on the combination of teaching with production and scientific research as the important means of training innovative talents for mineral processing engineering.

Jan 1, 2010

By K. Sasaki, T. Murakami, S. Akibayashi, Q. Wei

A numerical analysis and an experiment were done on groundwater flow past a bore hole with a cylindrical obstacle at its center. Flow around the obstacle in the bore hole was studied in detail. Two dimensional governing equations to simulate this flow were written for the hydraulic head and seepage velocity in a porous medium and for the vorticity, stream function, and velocity in the bore hole. These equations were non-dimensionalized and solved by using the alternating direction implicit and successive-over-relaxation finite difference methods. Flow visualization experiments and velocity measurements in the bore hole were done with a two dimensional model composed of a porous medium. The numerical analysis procedures were validated by a comparison of numerical and experimental results. Effects of the Reynolds number and obstacle size on flow in the bore hole are clearly shown in the velocity and streamline profiles. The quantitative relation between the seepage velocity in the porous medium and the velocity of flow around the obstacle in the bore hole also were estimated.

Jan 1, 1996

By A. C. Smith

Although it is only utilized in a few U.S. longwall mines, a bleederless ventilation system can be an effective spontaneous combustion control method in mines with a demonstrated history of spontaneous combustion. In order to provide insights for the optimization of bleederless ventilation systems for U. S. underground coal mines, a computational fluid dynamics (CFD) study was conducted to model the spontaneous heating in longwall gob areas with a bleederless ventilation system. A single longwall panel with a bleederless ventilation system was simulated, and typical ventilation data for a longwall mine was used in the simulations. The permeability and porosity profiles for the longwall gob were estimated using a geotechnical model and were used as inputs for the CFD modeling. The effects of gob permeability and resistance of the collapsed entries on the spontaneous heating were studied. The effectiveness of nitrogen injection to prevent spontaneous heating in the gob was also examined. Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health.

Jan 1, 2008

By J. M. Gambogi

Demand for titanium minerals and pigments was nearly unchanged in 1996 compared with 1995. However, through mine expansions and process optimization by the TiO, pigment industry, the available supply of titanium minerals and pigments increased moderately. At the end of 1996, exploration, development and expansion programs were ongoing in the mining sector. But expansion projects in the pigment sector were delayed pending increased demand.

Jan 1, 1997

By C. Babbitt, J. O’Green, N. I. Jayaraman

In many mines, dust-laden air from an entry being driven by a continuous miner will contaminate the intake air to the roof bolter operator and other downwind personnel. Through a US Bureau of Mines (USBM) contract, Foster-Miller Inc. has evaluated several control techniques to reduce the respirable dust exposures of downwind personnel. One fan and tubing technique consisted of bypassing the miner-generated dust directly to the section return. The results of the evaluation of this technique revealed that reductions in dust concentrations of 90% or more can be achieved at downwind roof bolter locations. A second method was to clean the dusty air from the upwind continuous miner by using a dust collector. The cleaned air was then supplied to the bolter through collapsible tubing. An underground evaluation showed reductions of 82% to 96% when the dust collector was operating. A third method was to reduce the quantity of dust contributed by the miner to the return airstream. A water-powered scrubber was installed over the throat area of the continuous miner. More than 1.18 m3/s (2500 cfm) of dusty air moved through five tubes with dust collection efficiency exceeding 75%. Underground evaluation results showed that return dust concentrations were reduced by about 60%. This paper discusses the ventilation and dust control techniques used for personnel downwind of the continuous miner.

Jan 1, 1987

By J. P. Sieverson

The Comprehensive Environmental Response, compensation, and Liability Act (CERCLA -commonly referred to as Superfund) was passed into law in December 1980 in the wake of such incidents as Love Canal and the Valley of the Drums. Superfund was originally perceived as a way of cleaning up spills of hazardous substances and/or cleaning up abandoned hazardous waste dumpsites. In February 1981, Michael Cook, EPA deputy assistant administrator for hazardous emergency response, called Superfund "a tremendously powerful law. It could revolutionize the way the environment is protected, but we certainly don't intend to realize the full potential of the law for some time." These words have proven prophetic for Asarco's East Helena Smelter.

Jan 1, 1988

By Ludovico Sebastiao Costa, Luis Albano Tondo, Bonzi Yokomizo Santos, Nelson Roberto Garcia Munhoz

This paper focus on the productivity, cost efficiency and training programmes that have enable RPM to rank as a world class operation in production efficiency and safety achievements. The first step was to commit all senior managers to implementing the NOSA Industrial Safety System based on Management by Objectives. This focused the workforce in a specific, results-driven direction which greatly promoted subsequent performance improvements. The early operations concentrated on increasing throughput via process simplification and removal of bottlenecks. Efforts were simultaneously directed to environment, health and safety as a means to improving the quality of operations. In the last two years, improvements in mining and in-tailings dam management have further improved the cost competitiveness of RPM such as to assure its future in treating the remaining CTBl ore reserves. Promissing progress is being made in developing a viable process to exploit a remaining large resource of B2 mineralisation.

Jan 1, 1993

By Ivan Hunter, Gary Johnson

In many comminution circuits based on SAG mills, an operating cost penalty is incurred in terms of high unit power consumption. By the addition of a crusher to the circuit, to crush part of the so­called critical size fraction extracted from the mill charge, the power efficiency of the circuit can be significantly improved. Dominion Mining has now incorporated pebble crushing into three of its comminution circuits. The improvements in circuit performance have in all cases been significant, and in some cases dramatic.

Jan 1, 1991

By C. J. Lewis

Commercial lime plants in the United States and Canada are depicted in Figure 1. The sources of lime available to Nevada and bordering states are rather few. Chemstar Lime has plants at Apex, Nevada and Nelsen, Arizona. Continental Lime, Inc. has plants at Tacoma, Washington, Townsend, Montana and Delta, Utah. However, Continental Lime has a new rotary kiln installation underway near Wendover, Nevada. This plant is scheduled to come on stream in the fall of 1989.

Jan 1, 1989

By Gábor Antal, József Bõhm, Barnabás Csõke

From the waste material of the production of aluminium foil aluminium pigment is produced for the paint industry by grinding it in white spirit. During grinding 1-2 % iron impurity gets into the product, weakening its quality, from the wear of the mill armour and the grinding bodies and from the contamination of the raw material. For deironing the product, a stage-operated electrically induced magnetic filter separator was developed and put into operation. The separator was sited in an explosive environment and therefore required a special design and safety system. The paper describes the results of the development work. the device that was developed, the safety system as well as the results of and experiences with the operation of the separator.

Jan 1, 1995

By S. Polegeg

The basic principle of this separation method was already defined in the middle of the nineteenth century. However, a change over for the treatment of minerals has followed from the construction of proper machines i.e. airjigs and airtables as late as in the twenties and thirties of this century. The main application of this technology was subsequently found in coal processing and reached quite a great dimension in the two following decades. The number of applications of this method in mineral dressing plants decreased rapidly and has almost vanished in the fifties in favour of wet concentration procedures. It has been for a long period as long as up to the eighties that no more consideration was taken for applying dry gravity separation in the field of mineral processing also due to the successful introduction of flotation. Due to the fact that labour cost was increasing remarkably within the past period after the end of World War II also the economic conditions in the agricultural sector became more though. As a result there came up a great demand for harvesting machines. Since agricultural products can only be processed by dry methods in a prevailing number, highly developed machines were introduced for the dry processing of food and feed stuff.

Jan 1, 1992

By Rolland L. Blake

The Bureau of Mines is investigating the potential for in situ leach mining "(ISM) of gold and silver mineralization. This preliminary study examined samples from several types of deposits using light optical microscopy and the electron microprobe to characterize the ore and gangue minerals and their microscopic characteristics, including the spacial relations between the target minerals and likely natural fluid channelways. Low grade disseminated deposit types from the western U.S. were found to contain fracture-hosted or matrix-hosted gold and silver minerals, some of which are encapsulated by quartz or pyrite. Geologic features readily observed microscopically include ore and gangue mineral identity, size, and their association with each other and with fractures. Successful ISM application to gold and silver deposits needs this data to: (1) select the proper lixiviant based on chemical reactivity of the host rock, ore, and gangue minerals, (2) determine potential permeability characteristics when designing lixiviant flow patterns, and (3) understand potential problems of the lixiviant reaching encapsulated ore minerals. Careful examination of the geologic characteristics of each ore body is required because of the observed diversity of characteristics in deposits from the same "class" and even within the deposit itself.

Jan 1, 1989

By H. Cho, P. T. Luckie

A study was undertaken to investigate the liberation behavior of coal macerals through size reduction and density separation. It was seen that the liberation of coal macerals could be achieved by size reduction, allowing selective separation of coal organic components. However, the degree of liberation was dependent upon the comminution history. Even for the same fineness, the extent of liberation might not be the same depending on how the material was generated. The liberation of coal macerals was analyzed by examining the liberation index. It was seen that, although comminution produced fine particles enriched in inertinite (primarily fusinite and semifusinite), these particles were less liberated than coarser particles. However, the liberation of macerals increased when all the feed was ground to a finer size.

Jan 1, 1999

By C. H. Bucknam, A. M. Raichur, M. Misra

Simultaneous dissolution of mercury along with gold occurs during cyanidation of gold ores. A method has been found for the efficient removal of mercury from the gold cyanide solution by treating with dithiocarbamates which form stable compounds with mercury. The mercury concentration in the leach solution can be brought down to low levels by adopting this treatment. Furthermore, it is also possible to stabilize the mercury in the ore heap itself by addition of this reagent so that mercury does not dissolve in the cyanide solution during heap leaching. Only trace amounts of mercury were detected in the pregnant solution obtained from a heap treated with dithiocarbamates. In this paper, process parameters are discussed in detail.

Jan 1, 1997

By F. X. Meagher

Vertical slot raise driving from bottom up has always been a hazardous, inefficient, high cost operation. The introduction of the Simba 5 drill rig has enabled this type of raise to be drilled accurately from the top down and to be blasted in stages from the bottom up. Safety, high efficiency and low cost were the main criteria in opting for this method. Drop raises with the Simba 5 at Geco have been successfully drilled and blasted up to 115 feet, and this is close to the maximum length of raise that can be drilled and blasted efficiently with Simba 5. A look into the future would indicate a rig capable of drilling up to 200 foot raises with the same accuracy of Simba 5 to 115 feet.

Jan 1, 1974

By Jean-Guy Deschamps, Allen H. Gipson

Profitability of heap leaching projects could be greatly improved if heap heights were significantly increased. Currently, heaps have been designed to a maximum height of approximately 450 feet. Higher heaps reduce ore processing costs by handling greater quantities of ore per unit area of pad. In areas with high rainfall, higher heaps also offer the benefit of a reduced catchment area resulting in less meteoric water to manage. The concern with high heaps is the functionality of geosynthetics and piping under extreme loads. Knight Piesold in Denver has developed the capability to test geosynthetics and collection piping under loads equivalent to those imposed by

Jan 1, 1996

By R. H. Lien, B. T. Waterman

Passive bioremediation can be a cost effective treatment for a variety of mine waters, including final draindown of closed cyanide heap leaches and seepage from tails dams. These solutions can contain noncompliance concentrations of arsenic, antimony, cyanide, mercury, nitrate, selenium, silver, etc. Passive bioremediation involves treating the contaminated solutions under anaerobic conditions. Contaminants such as mercury and nitrate are effectively removed in passive bioreactors whereas the effect of this treatment on TDS, cyanide, and sulfate is minimal. Several waters from gold heap leach operations were treated in the column tests. These tests determined the effectiveness of contaminant removal from each water and also provided important scaleup design information.

Jan 1, 1997