Search Documents

By Dean Brox

Tunnel boring machines (TBMs) have been used for the construction of various tunnels for mining projects for the purpose of access, conveyance of ore and waste, drainage, exploration, water supply and water diversion. Several mining projects have seen the successful and economic beneficial use of TBMs, and there is an increasing awareness of the benefits of TBMs for mining projects. Key technical considerations for the use of TBMs for the construction of tunnels for mining projects include geological issues (rock type, rock alteration, rock strength, rock abrasivity, durability, ground water in flows), depth of cover and the potential for overstressing/rockbursts, site access and terrain, portal locations, TBM constraints, minimum tunnel size, tunnel support requirements, contractor and labor experience, and project schedule demands. TBMs offer key project schedule benefits with high rates of progress, which is a unique economic advantage recognized for mining projects where timing is of the essence in order to advance mining development and achieve early startup for operations. A thorough evaluation of the anticipated ground conditions should be performed as part of the decision to adopt a TBM for a mining project. Minimum specifications for TBMs are necessary in order to prevent the incorrect type of TBM from being used. Appropriate geotechnical investigations are necessary in order to provide key information on the anticipated subsurface conditions for careful planning and design of the proposed tunnel alignment. The overall site and geological conditions associated with some projects may suggest that it is not appropriate to use TBMs for some mining projects due to a perceived higher risk. Key words: TBM, Tunnel boring machines, Tunneling in mining

Feb 1, 2014

By Dean Brox

Tunnel boring machines (TBMs) have been used for the construction of various tunnels for mining projects for the purpose of access, conveyance of ore and waste, drainage, exploration, water supply and water diversion. Several mining projects have seen the successful and economic beneficial use of TBMs, and there is an increasing awareness of the benefits of TBMs for mining projects. Key technical considerations for the use of TBMs for the construction of tunnels for mining projects include geological issues (rock type, rock alteration, rock strength, rock abrasivity, durability, ground water inflows), depth of cover and the potential for overstressing/rockbursts, site access and terrain, portal locations, TBM constraints, minimum tunnel size, tunnel support requirements, contractor and labor experience, and project schedule demands. TBMs offer key project schedule benefits with high rates of progress, which is a unique economic advantage recognized for mining projects where timing is of the essence in order to advance mining development and achieve early startup for operations. A thorough evaluation of the anticipated ground conditions should be performed as part of the decision to adopt a TBM for a mining project. Minimum specifications for TBMs are necessary in order to prevent the incorrect type of TBM from being used. Appropriate geotechnical investigations are necessary in order to provide key information on the anticipated subsurface conditions for careful planning and design of the proposed tunnel alignment. The overall site and geological conditions associated with some projects may suggest that it is not appropriate to use TBMs for some mining projects due to a perceived higher risk.

Jan 1, 2013

By H. Huang, R. N. Gow

"The reactivity of an enargite mineral electrode was investigated spectroelectrochemically under conditions typically found in alkaline sulfide leach solutions, with pH 11-13 and Na2S additions of 50 and 250 gL-1. A bulk enargite electrode was cycled between 0 and -1,000 mV for each set of solution conditions. Raman spectroscopy was used to determine and compare surface formations against species in mass-balanced EH-pH diagrams generated using STABCAL. Previously, it was determined that arsenic could be selectively leached under alkaline conditions at an average solution potential of -300mV, across the pH range 11-13. Operating under such conditions allowed for the selective leaching of arsenic with elemental sulfur formation. From several of the voltammograms obtained during this current testing, the formation of elemental sulfur appeared at increasingly reducing conditions with increasing sulfide concentration. At high concentrations, copper started to dissolve, possibly as a bisulfide complex, reducing the selectivity of the leach, unlike previous studies. However, the presence of the higher sulfide concentration is also anticipated to prevent passivation by consuming any surface formation of elemental sulfur. This study provides insight into the operating parameters of alkaline sulfide leaching in regards to the selectivity of arsenic leaching, as well as guidance for control of reagents and solution potential and, of course, the need for water treatment afterwards.IntroductionEnvironmental limitations on the pyrometallurgical processing of arsenic-bearing concentrates have forced operations to consider other solutions. Attempts to hydrometallurgically process enargite (Cu3AsS4) fall into two categories: the co-dissolution of arsenic and copper under acidic conditions, and the selective leaching of arsenic under basic conditions. The authors believe that the selective leaching of arsenic is more amenable because it produces a solid copper phase, preferably chalcocite (Cu2S) or covellite (CuS) that could then be processed using conventional methods already in place in the copper and gold industries. Potential leaching methods include alkaline sulfide leaching (Achimovicovica et al., 1999; Anderson and Twidwell, 2008a,b; Tongamp et al., 2009 and 2010), hypochlorite leaching (Vinals et al., 2003; Curreli et al., 2005; Mihaljovic et al., 2007), ammoniacal leaching (Gajam and Raghavan, 1983), and acid leaching (Gow et al., 2014b) with or without fine grinding to mechanically activate the enargite surface and increase normally slow leach reaction kinetics (Achimovicova et al., 1999; Balaz et al., 2000; Balaz and Achimovicova, 2006). In this study, the reactivity of enargite under alkaline sulfide leach conditions was examined."

Jan 1, 2015

By Christophe Bragard, Marte Gutierrez, Haotian Zheng, Michael Mooney

This paper proposes a framework for applying surrogate-based approaches to evaluate SEM construction, which can both benefit the uncertainty analysis in the design stage and real-time calibration during the construction process. The performances of four surrogate modeling approaches, namely back-propagation neural network (BPNN), support vector regression (SVR), random forest (RF), and polynomial chaos expansions combined with Kriging (PCK), were evaluated and compared. A variance-based global sensitivity analysis (GSA) was performed on the surrogate predictor to quantify the impacts of geotechnical parameters on the deformation responses induced by SEM tunneling. The Regional Connector Crossover Cavern project constructed in Downtown Los Angeles was set as the benchmark problem to demonstrate the efficiency and reliability of the proposed procedure.

Jun 13, 2021

By O. Babak, O. Leuangthong, M. A. Cuba

Integration of data from multiple sources and/or multiple scales is a common, yet challenging aspect of geostatistical resource modeling. Common approaches to data integration are based on a cokriging framework that assumes a consistency of scale in the information that leads to a requirement to composite the data prior to model construction. It is well known that the geostatistical model parameters are scale dependent. In particular, the volume variance of integrating these various scales has a direct impact on the semivariogram that should be used in model construction and/or the assessment of volume-variance relations as it affects resource estimation. This paper reviews and compares two different approaches for semivariogram upscaling. The first approach is the scaling laws. It is an empirically derived approach, involving several simplifying assumptions, one of which is a strict assumption of invariance of the semivariogram shape. The second approach is a theoretically derived direct upscaling of the semivariogram. This approach has been around for a number of years, but is seldom implemented due to software limitations. In this paper, we present a numerical integration approach to facilitate direct semivariogram upscaling. The advantage of direct upscaling over the scaling laws approach is shown by considering a synthetic example and a case study. Further, in the case of multiple codependent random variables, the extension of the direct semivariogram upscaling to the cross semivariograms is derived and an upscaled consistent linear model of coregionalization is presented.

Jan 1, 2013

By K. C. Liddell

Chemical processing research made notable advances during 1986. This overview is necessarily brief. It is intended, though, to give the flavor of selected areas where recent activity has been high. At the 1986 Annual Meeting of The Metallurgical Society, a symposium was held on hydrometallurgical reactor design and kinetics. R. G. Bautista, R. J. Wesely, and G. W. Warren edited the resultant proceedings volume. This is the first available volume on this subject. It includes 26 papers on fundamental kinetic studies, modeling of reaction kinetics and reactor performance, and pilot and production-scale operations. Metals discussed include silver, gold, platinum, titanium, cobalt, nickel, zinc, copper, manganese, and iron. Agitated tanks, heaps, dumps, pachucas, pressure auto-claves, electrolytic reactors, liquid membranes, and fluidized beds are among the reactor types covered. An international symposium dealt with iron control in hydrometallurgy. It was sponsored by the Metallurgical Society of CIM, the Institution of Mining and Metallurgy, The Metallurgical Society of AIME, and Gesellschaft Deutscher Metallhutten and Bergleute. J. E. Dutrizac and A. J. Monhemius edited a proceedings volume containing 41 papers. These covered many areas of process chemistry, solvent extraction, precipitation, treatment of pickle liquors, impurities, residues and the environment, and process selection. Precious metals Concerning precious metals processing, the US Bureau of Mines IC 9059 is noteworthy. It includes papers presented at a USBM briefing at the Western Mining Conference in Denver. Topics covered included ion exchange, staged heap-leaching direct-electrowinning, and mercury precipitation during cyanide leaching of gold ores. Also dealt with were carbonaceous gold ores, carbon adsorption and desorption, heap leaching, the carbon-in-pulp process, and precious metals recovery from electronic scrap and solder. R. C. Sandberg and J. L. Huiatt (Journal of Metals, June 1986, and USBM RI 9022) developed a method to recover silver, gold, and lead from a complex sulfide using ferric chloride, thiourea, and brine-leach solutions. Gallium Gallium recovery was also a subject of considerable interest. Much information on this topic is proprietary. But two papers described solvent extraction of gallium. V. P. Judin and R. G. Bautista (Metallurgical Transactions B, 1986) developed an equilibrium model to separate gallium chloride from aluminum chloride. Tributyl phosphate was the extractant studied. T. Sato and H. Oishi (Hydrometallurgy, 16, 1986) investigated gallium extraction from sodium hydroxide by using Kelex 100. Data were given on the equilibrium distribution and the extraction kinetics. Galena Interest continues in recovering lead by hydrometallurgical processing of galena. J. E. Dutrizac; S. H. Kim, H. Henein, and G. W. Warren; and M. C. Fuerstenau et al. (Metallurgical Transactions B, 1986) all investigated leaching of PbS by ferric chloride. Dutrizac reported parabolic kinetics and reaction control by outward diffusion of lead through a porous layer of elemental sulfur. Kim, Henein, and Warren, however, reported that two leaching reactions occur. A nonoxidative reaction produces H2S and there is an oxidative leaching by ferric ion. Acid dissolution was found to predominate when the acid activity to ferric activity ratio is high. Surface chemical reaction was reported to be controlling. Fuerstenau et al. also reported that mass transfer through the sulfur layer is rate determining. But they believe that the species transferred are chloro complexes of ferric ion. In other work on lead, A. Y. Lee, A. M. Wethington, and E. R. Cole, Jr. of the USBM described an environmentally acceptable hydrometallurgical alternative to the smelting of lead concentrates (RI 9055). Uranium In spite of depressed prices, much work has been reported on uranium processing. R. G. L. McCready, D. Wadden, and A. March-bank (Hydrometallurgy 17, 1986) described the nutrient needs for in-place leaching by T. ferrooxidans. They reported the optimal conditions for uranium solubilization. L. E. Eary, H. L. Barnes, and L. M. Cathles (Metallurgical Transactions B, 1986) carried out an experimental and modeling study of uraninite dissolution. They concluded that ferric ion preferentially leaches uraninite in pyritic ores. Hydrogen peroxide was found to be less selective. A. Vuorinen, P. Hiltunen, and O. H. Tuovinen (Hydrometallurgy 15, 1986) studied redox and precipitation reactions of iron and uranium in leach liquors. P. T. Chiang (Hydrometallurgy 17, 1986) reported on the effect of uranium loading in the DEPA-TOPO process to separate uranium and iron from wet-process phosphoric acid. F. J. Hurst (Hydrometallurgy 16, 1986) conducted a fundamental study of the separation of uranium from phosphoric acid by DEPA and TOPO. D. E. Chia and W. C. Cooper (Hydrometallurgy 16, 1986) reported on bench and pilot scale work to recover uranium by the HIMIX process. They reported that the acid consumption to produce an eluate suitable for yellowcake

Jan 5, 1987

By R. John Caulfield

The primary water supply system for the City of San Francisco and adjacent peninsula areas consists of aging and deteriorated pipelines crossing under the San Francisco Bay (the Bay). This system is highly vulnerable to seismic damage from the nearby San Andreas and Hayward fault zones. The Bay Tunnel Project will replace the existing system with a 8-km-long (5-mi-long) tunnel underneath the Bay. The tunnel will be constructed using earth pressure balance methods and will have a two-pass lining system of precast concrete bolted, gasketed segments for initial support, and a welded steel pipe final lining. The project challenges include tunneling through both soft ground and rock conditions without any intermediate shaft access over the entire alignment. Seismic performance criteria include maintaining service flows after a large earthquake.

By Antonio Nieto

According to the analysis of surface powered haulage accidents involving off-highway haul trucks in openpit mining, the U.S. Mine Safety and Health Administration (MSHA), reported 1,300 fatal accidents from 1990 to 2005. Of these, 163 were considered off-highway truck haulage accidents, and at least 23 involved collisions of an off-highway truck with a neighboring vehicle or a worker on foot (Nieto and Dagdelen, 2006). In general, an average of 18 nonfatal accidents and three fatal accidents occurred in openpit mining per year when equipment backed over the edge of an embankment, stockpile or dump point (Fessak, et al., 2003). The specific problems that need to be solved can be determined by carefully studying the accidents involving haulage trucks (Marrara, et al., 2004). Solutions to haulage truck safety must consider the human factors affecting each task even when engineering solutions seem most appropriate. In surface haulage, human performance becomes a critical issue because of the unusual demand the vehicle?s places on their human operators: ? Roadways and working areas change frequently in mining operations. ? The sheer mass of mining equipment such as trucks requires control inputs (e.g., braking) far in advance of the desired action. ? Rough roads, loading and unloading impacts can subject the driver to dangerous shocks and vibration. ? Visibility is sharply curtailed by the bulk of the vehicle generating large blind spots. All of the above issues can be attributed partially to the lack of visibility (Pyles et al., 2003). Driver visibility and communications are key issues to reduce mining truck accidents. Analysis of fatalities and injuries involving mining equipment demonstrates the need to develop new intervention and control strategies to mitigate the risks associated with mining equipment operation. Ongoing development of these and other new strategies is required to achieve a reduction of injury in the mining industry

Jan 2, 2010

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 Diler Katircioglu-Bayel

This manuscript aimed to examine the impact of operating parameters on the wet grinding of talc in a vertical-type stirred media mill. Within the scope of the research, the effects of operating parameters including media filling ratio, solid mass fraction, grinding media size, and grinding time were studied. The findings were assessed based on the product particle size (d50, d10), surface area (Sw), and energy consumption (Em). As a result of the present research, the following optimum grinding test conditions were determined: 65% media filling ratio, 40% solid mass fraction, 1 mm grinding media size, and 120 min grinding time. After determining the optimum grinding conditions, the Box–Behnken statistical design was used to determine the effect of parameter interactions on the d50 size. The media filling ratio was found to significantly affect the decrease in d50 compared to the other two parameters. Furthermore, the minimum d50 size was also achieved under optimum grinding conditions.

Aug 12, 2020

By Carlos Kovacs-Figueroa

Because of air pollution control regulations in the early 701s it became necessary to clean effluent gases from the Morenci Reduction Works Smelter. Feasibility studies indicated that this could be accomplished most efficiently by using the smelter gaseous effluent to feed a sulfuric acid plant. Complying with air pollution control regulations thus created the need to dispose of relatively large amounts of concentrated sulfuric acid. Typical Morenci ores contain substantial amounts of oxidized copper minerals which are not recoverable by flotation. In addition, there is low sulfide, high oxide material which can be leached, but is not suitable for flotation concentration. Early in 1971 sufficent data had been accumulated to show that a leaching plant for the Morenci tailings could use a large portion of the sulfuric acid produced by the Smelter. It was determined that for all practical purposes leaching of the available copper was complete in two hours or less. Capital expenditures could not be justified for more than two stages of counter current decantation for recovery of the leached copper, and the plant was designed with these criteria in mind.

Jan 1, 1976

By A. K. Raina

Blast induced damage to the final wall of rockmass in any civil or engineering application is a major concern to the rock excavation engineers. There are at least four distinct techniques practised by blasting engineers to minimise the damage to the parent rock during blasting that are classified as contour blasting. One of the methods to achieve a smooth wall or rock surface in blasting is pre-splitting, where blastholes in the final row are mildly loaded with explosives and fired first in sequence before the rest of the holes in a round of blast to achieve a split in rockmass. Since blasting is one of the most adopted methods for achieving a final wall in a desired shape, while maintaining the rockmass integrity, the design of pre-split blast assumes importance. There are several variables that determine the final shape of the pre-split face including the rock type, the drill diameter, the explosive characteristics, the orientation of major joints with respect to drill hole, the linear charge density, the spacing of drill holes and inclination of the drill holes. This study attempts to determine the importance and sensitivity of variables in pre-split blasting using historical data from open excavations of a hydroelectric project in India. Keeping in view the multitude of variables, low correlation of independent variables with responses and high level of interactions between the variables that define the blast results, it was found suitable to use ANN to determine the importance and sensitivity of the variables involved. A new method to determine the blast induced damage to rockmass, namely, undamaged area (AUD%), is introduced. Half Cast Factor (HCF%) and AUD%were calculated for a high wall and trenches by digital image analysis technique using the Fragalyst software. Joint spacing and linear charge density emerged as most controlling variables in determining the final result of pre-blast. The relative importance of other variables assuming significance in the case of both the designed outputs is also discussed. A comparative analysis of HCF%and AUD%on the basis of results obtained from ANN analysis is also presented. A futuristic approach concept has also been introduced.

May 30, 2021

By Charles H. Minott, Michael J. Markow, Robert D. Wyatt, Fred Moavenzadeh

The substantial investment in tunnels anticipated in the next twenty years has focused new attention on the economics of tunnel construction itself and on some costly problems associated with underground work: the uncertain geologic conditions, the performance and adaptability of men and equipment, and the need for quicker, more efficient excavation methods. There also exists a need to develop better ways of estimating tunnel construction. Inaccuracies in current bid estimates stem from a number of causes, among them (1) the effects of geologic conditions, which are not adequately known prior to construction, (2) the dependence of actual cost on the construction method used and on the interactions among the operations occurring underground, and (3) the reliability of tunneling equipment. Inability to estimate final costs for conventional tunneling more accurately has in turn caused difficulty in gauging the costs and benefits attributable to new tunneling technologies either under development or for which R&D programs are planned. ATTRIBUTES OF THE TUNNEL COST MODEL This paper presents a computer based Tunnel Cost Model (TCM) which quantitatively assesses the uncertainties inherent in underground work, and is detailed enough to aid in preparing estimates or bids. The model employs appropriate techniques of subjective (or "degree of belief") probability and computer simulation of tunnel construction operations to estimate distributions of total tunnel

Jan 1, 1974

By Erik Westman, BEN WESTON, SETAREH GHAYCHI AFROUZ, KATHRYN DEHN

This study investigates the changes in seismic velocity of rockmass before and after three major seismic events to determine any potential identifiable precursory velocity changes associated with these events. Induced stress measurement is one of the challenging tasks in deep underground mining, with extreme impacts on the safety and stability of the mine. This study used p-wave passive seismic tomography to image the velocity redistribution within a rockmass, which can indicate induced stress level changes in the rockmass and detect the velocity changes that might precede a major seismic event or a rockburst. The ultimate goal of this research focus is to develop another tool for the deep-mining community that will help to increase safety and efficiency. For this purpose, the hypothesis of conventional mechanics, which implies induced stress at the hypocenter (as inferred by the p-wave velocity) increases until the seismic event occurs, is evaluated. It is found that the p-wave velocity did not increase at any of the three hypocenters prior to the seismic event occurring; however, the p-wave velocity did increase in the closest “zone center” for two of the three events. 

By K. Kim

A site characterization strategy formulated for the probabilistic design of underground structures is presented, which takes into account the variability of rock properties and the stochastic nature of the rock failure process. It entails determining probability distributions of rock properties by utilizing the theory of extremes and Monte Carlo simulation. Laboratory and field test data are analyzed and presented to illustrate the methodology. The results indicate that the distributive characteristics of rock mass properties can be estimated using empirical relationships currently available. This results of analyses can be incorporated into the design of underground structures, and then, the relative uncertainties of the failure probability of the structures can be assessed.

Jan 1, 1995

By R. Kealey, D. Huo, Q. Zhang, Y. A. Sari

Greenhouse gas (GHG) emissions from primary mineral and metal production account for ~10% of global GHG emissions. One of the main sources of GHG emissions in mining operations is fuel consumption by haul trucks. Given their size and carrying capacity, the fuel consumption of haul trucks can approach 250 liters per hour. An average of 30% of the idle time of the trucks is spent while waiting in the queue. Inefficient truck dispatch planning can waste resources, cause dilution and elevate GHG emissions. In this research, a machine learning based truck dispatch approach was developed to dynamically route the haul trucks based on the loaded material, the road traffic, the estimated wait time, and the maintenance needs of the trucks. The GHG reduction potential of this smart fleet management approach was estimated by calculating and comparing the related carbon emissions versus scenarios using traditional fleet allocation approaches. Results suggest that this dynamic fleet allocation approach can significantly reduce GHG emissions at mineral production sites by optimizing waiting times and the overall distance travelled while achieving the same production levels.

Mar 2, 2022

By James Corcoran, Richard McLane, Matt Neuner, Joseph DeMello, Hugh Davies

The Los Angeles County Metropolitan Transportation Authority (LA Metro) Purple Line Extension Section 1 (PLE1) is a $3.12 billion USD design-build, underground heavy rail project, connecting an existing station at Wilshire Blvd. and Western Ave. and extending 3.92 miles under Wilshire Blvd, terminating approximately 550 feet west of Wilshire and La Cienega Blvds. The project alignment runs immediately adjacent to the La Brea Tar Pits, world renowned for Pleistocene fossils and continuous seepage of asphaltum (locally known as tar) and gas in an urban setting. This paper presents a successful case history of the planning, design, and construction efforts to safely construct the bored tunnels through Reach 3 of the alignment (between Wilshire/Fairfax Station, and Wilshire/La Cienega Station), in a designated Methane Zone in the City of Los Angeles. Historical context on decades of challenges and studies is summarized. Further, this paper outlines the pro-active partnership between the Owner: LA Metro, the Design Builder: Skanska-Traylor-Shea Joint Venture, and geotechnical design services provided by Golder Associates to safely manage pressurized face tunneling through a confined gas zone near the La Brea Tar Pits. Specifically, a program of in-situ oxidation and soil gas extraction was designed to test and analyze risks associated with pressurized face TBM tunneling through the complex subsurface geological conditions, then implemented during construction. In advance of tunneling, a network of wells was used to draw air into the gas zone to oxidize the 6,500 ppm hydrogen sulfide gas, as well as determine methane recharge rate. During TBM tunneling, the wells were converted to a gas extraction system to evacuate, filter (H2S) and burn (CH4) the gas as the Tunnel Boring Machine passed, providing a preferential pathway for the gas to migrate toward extraction wells, and preventing the migration to adjacent buildings. The team extracted and treated 3,857,000 cubic feet of mostly methane gas over 40 days as the TBMs passed through the zone. Gas behavior, pressures, and concentrations were monitored not only from the extraction system, but also in basements and utility vaults along this section of the alignment.

Jun 13, 2023

By Charles H. Wells

This paper describes a commercial installation of a sophisticated instrumentation and control system designed to maximize the performance of heavy medium cyclones. Samples of plant feed and its products were collected and analyzed for ash content so that measures of efficiency could be determined for plant operation under (1) manual control and (2) automatic (computer) control. The heavy medium cyclone control strategy and its digital computer implementation are discussed in detail. The sample results are analyzed and the economic benefits of automatic control are discussed. Results from the initial data sets quantify the economic benefits of automatic closed-loop control; viz, increased recovery and reduced clean coal variability have been clearly demonstrated.

Jan 1, 1981

By S. G. Malghan

Flotation is the primary method for copper minerals separation from porphyry ores. The need to process difficult-to-float porphyry copper ores presents challenges to engineers and scientists in several areas. This paper is concerned with summarizing generalized problems faced in the processing of porphyry ores and treatment methods to overcome the specific problems. Though some of the problems are interrelated the problems have been classified into three broad catagories. The case studies of some of the successful applications of innovative methods to solve problems related to ore mineralogy, metallurgical aspects of ore treatment and process variables show that quite often the problems are solvable by a judicious choice of flotation variables.

Jan 1, 1984

By Cengiz Karagüzel, Ömer Canıeren

The mobility of gold and silver metals from refractory ores is very low due to free metal ions in their bodies that bind the transportable and free metal molecules or they are encapsulated in minerals such as sulfides, arsenosulfides, carbonaceous, and clayey materials which make it difficult to extract them. As known from the literature, the enrichment of oxide refractory gold, silver ores, Ag, and Au-rich flotation concentrated from sulfur refractory ores can be leached in the chloride-hypochlorite solutions. In this work, the leaching approach was studied to extract silver ions from refractory ores in the presence of hypochlorite media under high pressure. The mineralogical and scanning electron microscopy analysis of the sample indicated that the silver was encapsulated in barite and quartz minerals in fine sizes. In order to obtain the optimum leaching conditions for the silver ore, the effects of several parameters, namely, temperature, leaching time, NaCl and NaOCl concentration, solid ratio, and particle size on the leaching recovery were investigated in detail. The leaching experiments showed that the highest silver recovery of 62.35% was obtained under the following conditions: temperature of 150 °C, oxygen pressure of 1800 kPa, leaching time of 2 h, concentrations of 2 mol/dm3 and 0.4 mol/dm3 for NaCl and NaOCl, respectively, the solid ratio of 30%, and particle size (d80) 15 μm. The results obtained from this study indicated that the enrichment of refractory silver ores to extract the silver encapsulated in barite and quartz minerals could be possible in the chlorite-hypochlorite under high pressure, a relatively shorter leaching time compared to conventional cyanide leaching.

Jan 28, 2021