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By Edward M. Jacobs

In some ore grinding circuits it is desirable to make separations purely on size. The normal choice for this is vibrating screen equipment. Developments in screening process technology have led to improvements in the capacity and efficiency of vibrating screens, through the adoption "Thin Layer Wet Screening". This process can reduce recirculating loads and equipment requirements in the ore grinding circuit.

Jan 1, 1985

By E. A. Gulbransen, W. S. Wysong

THE behavior of molybdenum and its surface oxides in oxidizing and reducing gas atmospheres and in high vacua at elevated temperatures is a question of scientific and technical importance The use of molybdenum as a metal or as an important component in alloys in oxidizing atmospheres at elevated temperatures has been limited because of the unprotective nature of its oxide film and the volatility of this oxide at moderate temperatures. This communication will present results of a vacuum microbalance study 1,2 of the following problems. (11) the oxidation kinetics in the temperature range of 250° to 450°C; (2) the reduction with pure hydrogen of thin oxide films formed on molybdenum; (3) the volatility of the thin oxide films, and (4) the vacuum oxidation of molybdenum at high temperatures. Molybdenum is an interesting metal to study for the following reasons: (I) although the oxide-to-metal-volume ratio is greater than one, the metal is not considered protective; (2) the metal oxidizes readily at temperatures of 250°C and higher; (3) the oxides of the metal are reduced at temperatures as low as 500°C by pure hydrogen; (4) the oxide MoO3 melts at 795°C; and (5) the oxides of molybdenum are volatile at moderate temperatures. The following variables are studied in the oxidation kinetics. time, temperature, pressure, surface preparation, surface area, concentration of inert gas in the lattice, cycling procedures in temperature, vacuum effect and high temperature vacuum oxidation The general interpretation of many of these factors has been previously discussed. LITERATURE The oxidation of molybdenum has not been studied critically. Although" many studies have probably been made on the kinetics of the oxidation process, none has been reported in the literature available to us. The crystal structures found in the oxidation of molybdenum have been studied by Hickman and Culbransen 4 Their results showed that MoO2 is the oxide which is stable in contact with the metallic subgtrate throughout the temperature range 300 to 700°C. As the film thickens in the low temperature range, MoO3 becomes predominant on the surface. Above 400°C, Mo03 is no longer observed, Mo02 being the only oxide found. Hagg and Magneli5 have shown from an X ray study that the a-phase, orthorhombic MoO3 is stable up to 1050°C. Two other phases, ß and ß', with compositions close to Mo02 90 are also obtained The formula for the ß phase is not given but that of the ß' phase is defined as Mo9026. The ß' phase is found to be built upon a monoclinic unit cell. A -?-phase is isolated from a preparation M00275 heated for 17 hrs at 670°C. This phase is

Jan 1, 1947

By R. B. Dunn

Whilst coalmining in the United Kingdom has been synonymous with longwall mining practice there have been changes in recent times which have enabled not only an extension in the length of the face to be worked but also in the ability to extract both thick and thinner seams. Additionally the industry has taken a positive view in the extension of retreat methods of extraction applied for different reasons both to particularly thick and specially thin seams. To permit development of a flexible programme to meet these diverse needs, it has been necessary to design machinery along with mining systems specially suited to these requirements. In reviewing current UK thinking special emphasis is made on the extraction of thinner seams generally of higher quality coal at moderate depths with a commentary on some recent results.

Jan 1, 1979

By B Roache

Ground support installation into the face of development headings has become an accepted practice at many Australian hard rock mines. Ground support is installed in the development face to reduce personnel exposure to rockfall while conducting work tasks such as marking up, installing lifter tubes, charging, and face sampling. The ground support system installed in the face is typically friction bolts and mesh. This support system can be effective at reducing rockfall occurrence, but it also increases the cost of development per metre, in terms of capital for the ground support, jumbo and operator capital allocation and the installation time slowing each drill and blast cycle. Other issues associated with meshing and bolting the development face include management of rock bolts and mesh sheets in the fired dirt of every cut, damage to services such as vent duct, geometry issues when installing ground support onto irregular development profiles and operator error. Fibrecrete installation onto the development face for support is an option considered by many mines, but it can be difficult to manage due to the removal of visual indications of misfires and slowing the mining cycle due to the wait time for fibrecrete curing. The use of Thin Spray Liner (TSL) products in underground hard rock mines has been relatively infrequent in the past, mainly due to issues with cost, health and safety, and liner strength. Kanmantoo Mine investigated the use of TSLs for the purpose of development face support, while collecting data on the costs and practicalities associated with their use. Several TSL products were trialled and a preferred TSL product was selected for use as face support. Cost savings, drill and blast cycle timing improvements and other benefits were achieved while meeting the requirement to reduce rockfall risk.

Mar 29, 2023

TSL Concepts and Practical Examples of the Non-Reactive System - Meyco TSL 865 Thin Spray-on Liners (TSLs) have been intensively investigated by mining and chemical industries within the last decade. Apart from the basic concept of spraying thin liners, expectations of the product's performance vary, eg immediate active strata support is seen as a key to control the ground permanently. For many coal mines this is an important factor to reduce maintenance in their roadways and enable permanent production from the long wall. In opposition to a passive mesh system this technology offers immediate active support to the strata. But not only coal mines are interested in TSL technology, there are potential applications in hard rock mines, during shaft sinking, pillar support and as an anti-weathering sealant. This paper will explain the advantages and disadvantages of TSL concepts; it will give examples of successfully applied TSLs with a main focus on the non-reactive and flexible system MEYCO TSL 865 by BASF. Furthermore, it will indicate the limitations and discuss briefly the bearing capacity and reasonable lab testing of such systems.

Nov 25, 2010

By C. Graham

Thin Spray-On Liners (TSLs) have been researched and in development for over two decades and yet their fully functional and widely justifiable application in mining has yet to be achieved. While the explanation for this is partly technical, it is also clear that proving and communicating the operational and economic case for why a mine should change from mesh or shotcrete liners to a TSL is not a trivial matter. Evidence must be presented and communicated effectively, that is both obvious and compelling for a mine operator. The paper describes recent work carried out and directed towards this end, with funding from CAMIRO?s Deep Mining Research Consortium and additional support from 3M Canada and ABB Canada. The essential progress that has been, or is in the process of being made, will be described in providing the necessary proof of acceptable or superior TSL performance in the following areas: polymer formulation, health and safety, geotechnical specification, robotic liner application, business case economics and yielding ground support effectiveness. Future plans are also presented to demonstrate the performance of a new 3M composite TSL/yielding bolt support system in underground trials where the substrate rock is intended to fail through a number of mining-induced mechanisms.

Aug 1, 2013

By Z Li, D Chalmers, J M. Tenney

This paper presents the findings and analysis of the investigation of effectiveness of thin spray-on liners (TSLs) as a gas management tool in underground coalmines. The project involves spraying TSL on the area surrounding gas drainage holes whereby the TSL acts as a thin membrane decreasing the permeability of the coal. This restricts air migrating through the coal seam and diluting gas from the drainage holes. There are a number of potential benefits from this technique but key points are that gas drainage holes produce gas with higher concentrations of methane. The design and execution of a field trial to investigate the effectiveness of a TSL on purity of in situ methane from gas drainage holes is presented in this report. For eight drainage holes, the results show an average increase in methane purity by 9.14 per cent and a reduction in air contamination by an average 7.93 per cent. Overall methane flow rate decreased by 27.6 L/s; however, flow rates were unreliable due to poor measuring equipment. For most holes, methane purity was not changed significantly; however, certain boreholes were responsible for most of the variation in methane purity. The boreholes showing a dramatic improvement in methane purity were likely those with intersecting cleats covered by the TSL. If the TSL was sprayed over more area, specifically in areas where the cleats are intersecting with holes, it is likely that purity of methane in the drainage holes will increase.CITATION:Tenney, J M, Chalmers, D and Li, Z, 2015. Thin spray-on liners potential in reducing dilution of in situ gas in underground coalmines, in Proceedings The Australian Mine Ventilation Conference, pp 323–328 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

By Andriy Burbelko, Daniel Gurgul, Wojciech Kapturkiewicz, Marcin Gómy

"The mathematical model of the globular eutectic solidification in 2D was designed. The proposed model is based on the Cellular Automaton Finite Differences (CA-FD) calculation method. The model has been used for studies of the primary austenite and of globular eutectic grains growth during the ductile iron solidification in the thin wall casting. The model mentioned above takes into account, among other things, non-uniform temperature distribution in the casting wall cross-section, kinetics of the austenite and graphite grains nucleation, solute diffusion and non-equilibrium nature of the interphase boundary migration.Some aspects of stochastic nature of the solidification processes are taken into account. The results of the CA solidification modeling have been shown, that differences between cooling curves obtained in the same conditions of the casting solidification may be a result of the stochastic nature of the grain nucleation.The results of modeling were compared with the experimental microstructure. The model is well worked for thin walled ductile iron casting, for fast solidification process.IntroductionNodular graphite cast iron, also known as ductile iron (DI), has major applications in critical engineering parts due to its mechanical properties and castability. The mechanical and physical properties of this material depend on the shape and number of the graphite grains andmicrostructure of the metallic matrix.Solidification of DI was a subject of many computer modeling programs described in literature [ 1-5], in which the stationary conditions of carbon diffusion in austenite is pre-assumed. Recently, a tendency for production of thin-walled castings has been observed [ 6-8]. In this technology, the process of the fast solidification may be very far from equilibrium and steadystate conditions [9].The purpose of the present work is a two-dimension model development for simulation of the DI structure formation during the solidification in the condition of non steady-state temperature and diffusion fields in the thin-wall casting.Model of process The CA-FD is one of the known methods of the simulation ofmicrostructure formation during the solidification [ 10, 11]. In the CA microstructure modeling the outer grain shape is the result of the simulation and does not superimposed beforehand. The model development for a onephase microstructure evolution is a subject of the numerous researches [12 -23]. Model of the eutectic solidification of DI in the uniform temperature field and superimposed cooling rate is known [24]."

Jan 1, 2013

By John Marsden, John Mansanti, Jim Arnold, Mike Gleason

DOUG HALBE: We're not quite to the end of our session, but we're close. We've had a lot of fun with some of these spill ideas. But these are serious problems, and I think we might be able to benefit by continuing to compile these. Several years ago, the metallurgists at the various operations of Gold Fields Mining Company had a newsletter that came out every two months for several years. This publication consisted of short articles by the staff at the various operations, plus a few others, on problems they'd had and how they solved them. One very useful article, "Things We'd Have Done Differently at Chimney Creek," was written shortly after start-up. John Marsden was the editor and John Mansanti contributed to it, as did Jim Arnold (our distinguished co-chair) and Mike Gleason. I would be interested, with the permission of the audience, in editing that article to make it a little bit less abrasive and putting it into the record here. I think it's a useful SME function to maintain a list of things we've done wrong in plant design, things we don't want to do again. If we have another open session in the future, would others be willing, even anonymously, to contribute, bring slides, and say "Hey, look at the goofs we made?" [laughter, followed by support from the audience] Okay, we'll plan on that. And we'll try to include the Chimney Creek list in the transcript of this session-perhaps edited a bit.

Jan 1, 1998

By Tom Barczak

Early in my career, while giving a presentation on shield design for longwall mining at one of the International Conferences on Ground Control in Mining, the late Jim Scott told me that I was finally getting it, because ?I was starting to think like a rock!? Although I didn?t realize it at the time, those few words changed my career forever. At the start of my career, I did a lot of laboratory testing, taking advantage of the unique capabilities of the Mine Roof Simulator to study the performance and design characteristics of longwall shields. I had a pretty good handle on what made shields work and what made them fail, but I was still struggling with how and why they develop their in-service loads and what they were actually controlling as opposed to being passive bystanders in a world beyond their control. It became clear to me that the simplistic models of dead weight loading could not explain the behavior I saw and measured underground. The problem did not go away when I started studying standing support systems. Again, I learned much about the strength, stiffness, and stability of these supports and helped the industry develop several new support products that attempted to provide more efficient support designs. But here, too, the simplistic models of dead weight loading did not seem to fit for me. That?s when I began to incorporate the ground reaction concept as a way of integrating the support response and the ground behavior into a cohesive design methodology. The concept has its limitations, no doubt, but I believe some form of it will be the future of not only designing supports but also, in the broader sense, enhancing the engineering aspects of ground control. The paper presented at the International Conference on Ground Control last year by Esterhuizen (2010) on pillar behavior is evidence of this. Think like a rock. Jim Scott was right. It takes two to dance. You can?t dance alone and you will never understand ground control by thinking like a support! ?Dumb as a box of rocks?? I don?t think so. The answer lies in the rocks!

Jan 1, 2011

By Greg Smith

This paper documents the use of bench testing equipment developed to enhance the understanding of, and improve upon, common roof bolt support systems. Most roof bolt systems consist of components that are covered within the scope of ASTM (American Society for Testing and Materials) standards. However, ASTM does not specify testing methods or performance standards for complete roof bolt ?systems?. It only designates testing methods and minimum performance standards for roof bolt ?components?. Improved understanding and continuous improvement of these systems is essential given the enormous impact that they have on the safety and profitability of underground mining operations. Bench testing equipment has been developed that effectively measures and records multiple points of deformation in a rock bolt support system while load is being applied. With this testing capability, an improved understanding of component and system stress distribution can be obtained and devices and methods for visual load indication can be developed. This paper is formatted as case studies where testing was performed to demonstrate load versus deformation profiles and to develop system improvement products.

Jan 1, 2012

By B. Anderson, P. Churak, S. Dewar, A. Johnson, P. Eger

Although vegetation can be successfully established on fine taconite tailings, innovative approaches are needed to reclaim the coarse tailings used for dam construction. Through a series of cooperative projects with various government agencies and industries, EVTAC has been able to develop a unique closure plan. This plan will not only meet current reclamation standards, but also provide mitigation for a disturbed wetland and possibly create a tree plantation in the interior of the basin. By using waste products and exchanging materials, reclamation of the entire basin will be accomplised in a cost effective manner.

Jan 1, 2002

By Ronel du Plessis, John C. Davidtz, Jan D. Miller

Recent results from electrochemical measurements demonstrate that trithiocarbonate (TTC) collectors are more readily oxidized to their corresponding dithiolates than the dithiocarbonate/xanthate (DTC) collectors. Based on the traditional analysis of collector adsorption, trithiocarbonates might then be expected to be effective for bulk sulfide mineral flotation. Previous bench-scale flotation research had shown that TTC collectors are very effective for the flotation of copper sulfide minerals and PGM (platinum group metal) sulfide minerals. More recently, the TTC collectors were evaluated for auriferous pyrite recovery in benchscale plant scale flotation testing in the United States and in plant tests at Anglogold in South Africa. TTC collectors were also applied in bench-scale testing of a PGM ore. In each case an improved separation efficiency was realized. Fundamental studies at the University of Utah examining the effect of collector structure (functional group, -O-CS2 versus .S-CS2), specifically with respect to auriferous pyrite flotation, are in progress. The effect of collector structure was evaluated with air as well as nitrogen as the flotation gas medium. Experimental techniques utilized included electrochemically controlled contact angle measurements to evaluate mineral hydrophobicity and infrared spectroscopy to explain collector adsorption phenomena at the mineral surface.

Jan 1, 2003

By W B. Gregg

"A review, update, and expansion of Thiokol’s presentation at BAl’s Fiih High Tech Seminar titled ‘ADetonator - An Era of Precision in All-Electronic Detonators” is provided herein (and should be considered as a supplement to that publication). Thiokol is currently in the development and field evaluation phase of activities for our ACCUBLASTTM all-electronic detonator. The ACCUBLASTTM detonator uses a semiconductor bridge (an electronic match) in place of a conventional hot wire to initiate a safer, less sensitive material, titanium subhydride potassium perchlorate. The device is programmable to provide blast delays in one millisecond increments ranging from 1 to 500 milliseconds. The ACCUBLASTTM detonator combines an all-electronic programmable timer coupled with a semiconductor bridge to ensure detonation timing accuracy with +I00 microsecond precision. Initial development and field testing have been completed. These tests have verified ACCUBLASTTM detonators’ precision."

Jan 1, 1995

Dravo Corporation was founded in 1891 and has long been recognized as a major domestic engineering and construction firm headquartered in Pittsburgh. In 1977, Dravo had revenue of $852.2 million with international business activities contributing $248 million; quite a different picture than envisioned at the turn of the century. Engineering and construction activities still dominate Dravo's most recent history and will do so for the immediate future. However, fluctuations in capital spending by large industrial sectors of our economy during the late sixties were affecting Dravo's planning for continued growth along its traditional lines of business. Diversification was a possible solution to smooth out the upward trend in corporate earnings. One large result of these continuing efforts was the formation of Dravo Lime Company, a vertically integrated, proprietary chemical supplier for the air pollution control market. Briefly retracing the seventies, the passage of the Federal "Clean Air Act" in 1970 supplied the impetus for Dravo Lime Company. This law promulgated limits on the emissions of sulfur dioxide (SO2) from large stationary sources that would affect local air quality. The major industry that felt the brunt of this regulation was the electric utility industry, especially those generating electricity with coal-fired boilers. The law hastened the development of a new industry, flue gas desulfurization (FGD), and is composed of three major segments: (1) the electric utility, (2) the FGD equipment suppliers (the scrubbing modules), and (3) the scrubbing chemical suppliers. Dravo's experience suggested the equipment end of the business but market analysis indicated that our long range corporate goals could be better attained by investigating the chemical processes involved in the removal of the SO, gas. The result being Dravo Lime Company. This paper will briefly describe the Thiosorbic lime scrubbing process and review our innovative mine and calcining facility.

Jan 1, 1978

The mechanism of thiosulfate decomposition and the products formed were investigated in the presence of pyrite or pyrrhotite in copper-ammonia solutions used for leaching gold. The presence of the sulfides significantly increased the decomposition of thiosulfate. The sulfide-surface-catalyzed oxidation of thiosulfate to tetrathionate by dissolved oxygen or the cupric tetra-ammine complex was proposed to be the dominant thiosulfate decomposition mechanism. The catalysis of the sulfides in this reaction could originate from their strong affinity for aqueous sulfur species and their semiconducting properties. Oxygen was found to be the initial driving force for thiosulfate decomposition in the absence of cupric ions and the driving force for the continuous decomposition of thiosulfate in the presence of cupric ions. Under an oxygen free atmosphere, the decomposition of thiosulfate was limited to reduce the cupric ions and the catalytic effect of the sulfides was also marginal. The dominant oxidative product of thiosulfate was trithionate in alkaline solutions especially in an oxygen rich or cupric ion rich environment. Tetrathionate was found in relatively smaller amounts in an oxygen and cupric ion deficient environment. Tetrathionate was not stable and would further decompose after extended periods. Trithionate concentrations increased almost linearly with time.

Jan 1, 2005

By M. A. Belokrys, F. O. Milovich, D. D. Aksenova, V. A. Ignatkina, V. A. Bocharov, A. A. Kayumov

Copper remains one of the most sought-after metals in the industry. Tennantite (Cu12As4S13) and tetrahedrite (Cu12Sb4S13) that occur in pyrite copper, copper-zinc and polymetallic ores are an additional reserve for increasing technological parameters of flotation. Pyrite mass (85% and more) has similar flotation properties to other sulfide minerals, and imperfection of reagent regime is a common problem that occurs during quality copper concentrate processing. Due to tennantite's and chalcopyrite's differences in flotation properties with butyl xanthate at pH > 10, tennantite often reports to the flotation tails. Hight alkalinity of the medium increases the oxidation level of sulfide minerals, thus increasing the concentration of S2O3 2-, SO3 2- SO4 2-. At processing facilities in the Russian Federation, the concentration of thiosulfate ions in pulp is in the range of 0.5 to 1.5 g/l and higher, which leads to a decrease in flotation activity of the tennantite. The effect of butyl xanthate (as standard), thionocarbamate, dithiophosphate and M-TF (a mixture of dithiophosphate and thionocarbamate) on monomineral (tennantite and pyrite) flotation in the presence of sodium thiosulfate was studied. The variable parameters of the "thiosulfate-collector" flotation complex were thiosulfate concentration (100-900); pH (8-12,5). The scientific methods included contact angle for hydration assessment; TEM for surface studies; UV spectroscopy and iodometric titration for solubility control. Comprehensive studies have established a connection between the concentration of thiosulfate ions and tennantite flotation selectivity. Flotation activity of tennantite is higher at pH 8 with a thiosulfate concentration under 300 mg/l. Pyrite remains active with butyl xanthate under the same conditions. TEM images of the surface films of the collectors on pyrite were acquired at pH 8. The MTF provides the biggest difference in adsorption, wettability and flotation activity between tennantite and pyrite at pH 8 and thiosulfate concentration under 300 mg/l, in comparison with butyl xanthate. The results of the research will be applied to improve selective reagent regimes of tennantite minerals flotation. Keywords: Tennantite, pyrite, chalcopyrite, sphalerite, flotation, sulfhydryl collectors, thiosulfate, adsorption, mechanism, reagent regime

Jan 1, 2020

By Mark Aylmore, Guy Deschenes

"Increasing pressure are motivating the gold mining industry to develop a substitute to cyanide for leaching gold. This effort in mainly based on the high toxicity of cyanide and on the lack of efficiency of cyanide in the treatment of mildly refractory gold ores (sulfides and pre-robbing). Consequently, in only a few years, consortia have been created to elucidate and implement a new technology. The most promising lixiviant that has been selected to replace cyanide is thiosulfate. This paper will present a critical analysis on the latest developments in thiosulfate leaching and illustrate the potential and limitations of the technology with experimental data. Finally an assessment of the cost and performance of thiosulfate leaching relative cyanidation will be evaluated.INTRODUCTIONConcerns regarding the toxicity of cyanide and inability of cyanide solution to effectively leach some carbonaceous gold ore or mild refractory gold ores have made the gold mining industry evaluate alternative lixiviants to leach gold. This concern has been heightened recently by the cyanide spill at a mine in Romania, which devastated a 250-mile stretch of the Danube River and its tributaries, and the environmental damage at Ok Tedi mine in Papua New Guinea. Some countries and locations have prohibited the application of cyanidation to recover gold, such as, California and Colorado States, Japan and Turkey etc.There are several potential non-cyanide lixiviants (Sparrow and Woodcock, 1995) for gold extraction, such as thiosulfate, thiourea and halogen. A pilot feasibility test (Marchant and Broughton, 1987) had suggested that thioureation might result in acutely toxic byproducts even after treatment. Scientists of Swedish Academic of Sciences reported that thiourea is a carcinogen. Halogen is also a pollutant to the environment. Thiosulfate leaching appears to have very good potential as an effective and less hazardous procedure for gold and silver extraction from auriferous ores. In addition to being much less toxic and relatively cheap, it forms a stable anionic complex with gold but is less reactive to other metals, for instances, copper and carbonaceous materials, in comparison with cyanide."

Jan 1, 2001

By R. Y. Wan

Newmont Gold Company has advantageously used the capabilities of mineral oxidizing bacteria to develop a process for pretreatment of low grade sulfidic and carbonaceous-sulfidic refractory gold ores. The biooxidation process results in the oxidation of the sulfidic minerals with increased exposure of gold for subsequent gold recovery. The biooxidized carbonaceous-sulfidic ores cannot be heap leached with cyanide because of the "preg-robbing" characteristics of the carbonaceous matters in the ores. An alternative heap leach process using ammonium thiosulfate was developed to extract gold from the "preg-robbing" biooxidized ores. The ammonium thiosulfate leach process has been successfully practiced both in laboratory and pilot plant testing. Satisfactory test results encourage the continuation of process development.

Jan 1, 1996

By I. H. Gundiler

Although cyanidation has been universally applied in the processing of gold and silver ores, the search for less toxic alternatives continues. Difficulties encountered in processing ores containing oxidized copper minerals and the inherently slow kinetics of cyanidation have generated a renewed interest in thiosulfate leaching. This process, as well as the catalytic effects of copper ion, were well recognized and widely applied towards the end of the past century. In this study, the effects of copper, ammonia, and thiosulfate concentrations on gold dissolution were investigated using the rotating disk technique. Extraction of gold and silver from an oxidized copper-bearing ore was also studied utilizing a statistical experimental design, and these results were displayed in the form of contour plots.

Jan 1, 1993