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By H. Fujihara, K. Uesugi, H. Toda, A. Takeuchi, K. Shimizu

"Hydrogen is trapped at a variety of microstructures, for example grain boundaries, dislocations and particles. It is thought that hydrogen trapped at trapping sites is redistributed to the other sites under loading and then brittle fracture occurs with hydrogen accumulation. In order to understand hydrogen embrittlement behavior, it is necessary to investigate the time evolution behavior of hydrogen accumulation at each trap site. In the present study, changes in hydrogen distribution are observed under stress using Kelvin force microscopy (KFM) that can visualize hydrogen concentration distribution on material surface at high resolution. Spot-like hydrogen enriched regions are observed on the surface of a material. In addition, hydrogen depleted regions are observed around those enriched regions, and the appearance of hydrogen trap due to particles existing near the material surface is revealed. On the other hand, hydrogen trapped at grain boundary can be visualized. From in this result, it was suggested that crystallographic factors influence hydrogen accumulation. The relationship between initiation and propagation of intergranular crack and hydrogen accumulation under stress will be discussed.INTRODUCTIONHydrogen present in a metal sometimes has significant effects on various properties. Hydrogen in a metal is trapped at a variety of microstructure, for example dislocations and grain boundaries. Grain boundaries, dislocations and micro pores are the major trap sites in aluminum alloys. Some researchers considered that hydrogen redistribution and accumulation between these trap sites in a material with loading plays an important role in the brittle fracture behavior. In general, in intergranular fracture and quasi-cleavage fracture, the hydrogen trapped at grain boundaries and dislocations contributes to fracture behavior, respectively. Recently some researchers have shown that the ductile fracture in aluminum alloys is resulted from growth and coalescence of hydrogen micro pores. Analysis using first principles calculation indicates that intergranular fracture occurs when hydrogen concentration reaches 20 atom H/nm2ongrain boundary. From this report, it is considered that hydrogen redistributed during deformation accumulates locally in order to cause hydrogen brittle fracture. In order to understand hydrogen embrittlement, it is necessary to investigate the time evolution behavior of hydrogen accumulation at each trap site. In the present study, we evaluate the relationship between hydrogen accumulation behavior and fracture behavior in Al-Zn-Mg based alloys. In-situ observation was made by combining the tensile test with Kelvin force microscope (KFM) that can visualize the hydrogen concentration distribution on the material surface with high resolution. We also investigate the relationship between hydrogen distribution behavior and crystal orientation."

Jan 1, 2018

By James Ransford Dankwah

High sulphur carbonaceous materials like petroleum coke and rubber tyre are unsuitable as reductants in ironmaking because part of the sulphur is transferred to the reduced metal. Globally, while large amounts of petroleum coke are produced annually from the industrial processing of crude oil, billions of end-of-life rubber tyres are held in landfills and stockpiles. This work therefore investigates the potential feasibility of utilising these high sulphur carbonaceous materials as reductants in ironmaking without transferring the sulphur into the reduced metal. Composite pellets of iron oxide containing end-of-life rubber tyre (RT), petroleum coke and blends of RT/petroleum coke and petroleum coke/high density polyethylene (HDPE) were heated under argon atmosphere in a horizontal tube furnace. Reduced pellets were analysed after 10 minutes of reduction for their sulphur content. The results showed that sulphur-free metallic iron can be successfully synthesized using RT and petroleum coke as reductants. The level of desulphurisation depends on the nature of blending of the carbonaceous materials.

Jan 1, 2014

By John D. Carriere, Jean Leung, Daniel. Laguitton, Michael .. J. Burrows

"The objective of this expert system application in a copper-zinc concentrator, is to increase the availability of assay data through substitution for erroneous data. The assay data is used by the Operations personnel and automatic process control strategies to control flotation circuit performance. Two online X-ray fluorescence analysis systems analyze 24 streams across four divisions to provide the required data. Data availability of individual streams average 90% while the resulting circuit availabilities are 70%. The unavailability of correct data results from mechanical, X-ray or process problems. The erroneous data can be identified by process experts using knowledge relating stream interdependencies and historical process behaviour. An expert system was devised to provide real time identification of erroneous data and substitute for that data with the ultimate aim of improving metallurgical response by both the operator and automatic control systems.The paper discusses the early development work and architecture of the knowledge base designed using Neuron Data's expert shell NEXPERT.INTRODUCTIONThis paper describes the early development of an expert system (ES) prototype at the Kidd Creek concentrator. The project is a joint undertaking of the Kidd Creek Division of Falconbridge Limited and CANMET. Kidd Creek entered into the project to apply heuristic rules to the XRF assay data to improve the metallurgical control of the flotation process by increasing availability of analysis data. This project provided a problem of suitable size and future expandability while making use of a wide base of in-house expertise and experience. Another important benefit is the introduction of expert system technology to the site providing tools and experience for future system selection and technology application. CANMET has an on-going interest in assessing various aspects of ES technology (hardware, software, knowledge engineering, integration) while addressing problems in process operations that could most readily benefit from the technique. CANMET's role in the project was to provide project assistance, financial support, substitution algorithm assistance and software for data substitution. The knowledge bases (rules) have now been completed and are to be tested in the online environment."

Jan 1, 1989

By R. H. McCorkell

Radon emanation rates. J. and compositions of materials from the Canadian Certified Reference Materials Project (CCRMP) indicate that the fraction of the Rn produced that escapes, E, is usually 1% to 8% and the 238U decay chain is nearly in secular equilibrium. For some Chinese ore standards, E values are higher than f or the CCRMP materials. Standard ore tailings have 2/oPb concentrations higher than expected from their 226Ra concentrations and Rn escape rates (12 - 34%) . Biological materials have E ˜100%, their ash E ˜0%. Pelletizing ore powders at 20 000 lb/in2 reduces J by only 20 - 40% but only 2% of Rn escapes from pressed Li2B4O7 pellets and 0.01 - 0.04% from fused Na2B4O7 or Li2B4O7 discs. Large, difficult-to-explain random variations in J are observed in some situations but several highly reproducible ways of measuring emanation rates have been found.

Jan 1, 1986

By J. H. Reiss, D. F. Bruhn, Idaho National Laboratory, Y. Jiao, D. W. Reed, Y. Fujita, D. L. Daubaras

"Bioleaching offers a potential approach for recovery of rare earth elements (REE) from recyclable materials, such as fluorescent lamp phosphors or degraded industrial catalysts. Microorganisms were enriched from REE-containing ores and recyclable materials with the goal of identifying strains capable of extracting REE from solid materials. Over 100 heterotrophic microorganisms were isolated and screened for their ability to produce organic acids capable of leaching REE. The ten most promising isolates were most closely related to Pseudomonas, Acinetobacter and Talaromyces. Of the acids produced, gluconic acid appeared to be the most effective at leaching REE (yttrium, lanthanum, cerium, europium, and terbium) from retorted phosphor powders (RPP), fluidized cracking catalyst (FCC), and europium-doped yttrium oxide (YOEu). The Acinetobacter isolate, BH1, was the most capable strain and able to leach 33% of the total REE content from the FCC material. These results support the continuing evaluation of gluconic acid-producing microbes for large-scale REE recovery from recyclable materials.INTRODUCTIONAn enhanced recovery, substitute, reuse or recycle paradigm is important for balancing the supply and demand of critical materials (DOE, 2011). The recovery of rare earth elements (REE) from recyclable materials is an important component in this model. REE are used in a variety of modern products. For example, neodymium, europium, terbium, dysprosium, and yttrium are important for applications such as permanent magnets, lamp phosphors, rechargeable batteries, etc. (Binnemans, Jones, Blanpain, Van Gerven, Yang, Walton, & Buchert, 2013; DOE, 2011; Graedel, Harper, Nassar, & Reck, 2013). Cerium and lanthanum are used in glass polishers and additives in fluidized cracking catalysts (FCC)."

Jan 1, 2016

By Lawrence Devon Smith

What is a Failed Project? For mining projects, some key indicators of a ?failed? project are: ? Cost is more than it should be (particularly capital) ? Schedule ? It takes longer to build than expected ? It takes longer to ramp-up than expected ? It does not do what it is supposed to do ? Poor performance; output, product specifications; ? Low revenue ? High costs ? No one is happy about it: Management, Shareholders, Bankers ? Does a project fail if it does not meet expectations that were unrealistic and unattainable? ? Caution: Failure may not become evident until years later

May 1, 2010

By R. W. Thompkins

The two largest contributors to silicosis in machine men are dust from drilling and dust from blasting. With the advent of the shatter-cut method of blasting, the evils of blasting dust were greatly reduced. The problem of dust from drilling has been attacked from two different angles: (1) The adoption of dustless frontheads or enlarged water tubes, both of which have proved capable of reducing dust concentrations; and (2) The adoption of better ventilation. Many operators are loath to adopt dustless frontheads or enlarged water tubes on Leyner drills because of the increased repair costs on drills, and also because it has been found difficult to enforce 'the proper usage of dustless machines: for example, workmen sometimes plug the vents in the fronthead.

Jan 1, 1943

By Jorge Blanco, Joaquin Gotor, Enrique Delgado, Carlos Frias

Since 2009 Cobre las Cruces (CLC) has successfully operated a sustainable mining business near Seville, Spain, applying the most advanced hydrometallurgical technologies to process secondary copper sulphide ores through atmospheric leaching in ferric sulphate media and using oxygen sparging in a cascade of ten reactors. In comparison to conventional copper smelters, the CLC hydrometallurgical process does not generate SO2 gas, airborne emissions or slags. The copper ore is ground and sent directly to atmospheric leaching reactors; flotation is not required, and consequently, copper extraction is maximized at 93-95%, while producing 72,000 t/y copper cathodes of the highest purity (99.999 wt.% Cu, Grade A). Reserves for the CLC deposit were estimated at 16 million tonnes of ore averaging over 6 wt.% Cu and containing principally a chalcocite mineralization. Other copper bearing species include digenite, covellite, chalcopyrite, bornite and enargite. Pyrite represents over 70 wt.% of the ore. In the CLC leaching process, chalcocite reacts with ferric sulphate at approximately 90 ºC and copper is released into solution while ferric ions are reduced to ferrous ions. The ferric sulphate leachant is regenerated continuously by oxygen injection and consumes sulphuric acid. It is remarked that pyrite plays a crucial role to yield high copper leaching rates. When pyrite is oxidized, a small proportion of iron is co-leached and some sulphuric acid is generated. The CLC leaching technology has been designed to allow a certain level of pyrite oxidation, which is positive in many ways: (i) to maintain a Fe/Cu ratio in solution; (ii) to facilitate Fe(II) oxidation; (iii) to produce a high redox potential; and (iv) to counterbalance a bleed solution that removes some iron. Moreover, galvanic interaction between pyrite (cathode) and chalcocite (anode) can substantially increase atmospheric leaching kinetics and efficiency (copper recovery).

Jan 1, 2016

By Jean-Luc Beaudoin

"In addition to the actual energy consumed, billing is dependent on the peak load and the power factor. The lower the power factor goes, the higher will be the penalty the consumer pays. The principles of a power factor regulator, the two ways of improving the power factor and methods for calculating the capacitor values required will be described.The rate structure of the utility company is founded on three cornerstones: the energy consumed during a given period of time and two penalties imposed when the power factor is low or the power demand is high. Even though the normal consumption of a customer might be 10 kW, with a peak demand of 20 kW only once a month, the wiring and associated equipment at the input to the customer's plant will have to accommodate this peak demand. The power company has no means of forecasting these demands and cannot therefore provide the additional equipment necessary. So it exacts a penalty, and the customer must take all possible steps to avoid these peak power demands. This can be accomplished by using an automatic peak load regulator which will selectively disconnect the loads which are not essential in the operation of a plant .The principles of such a controller will be described.Principles of power factor regulatorsThe operating principles of a power factor regulator will now be described. It might be asked why the power factor of an electrical installation in a mine, or a factory, should be corrected at all, but there is a simple answer. In addition to the actual energy consumed, the billing is dependent on the peak load and the power factor. The lower the power factor goes, the higher will be the penalty the consumer pays."

Jan 1, 1982

By J. Roth

"While not taking issue with the general thesis expressed in Dr. Ridge's analysis of the role of genetic concepts versus observational data in ore exploration (Ridge, 1983), the criticism could be offered that the author tends to slight the importance of conceptual (i.e. theoretical) models in mineral exploration.As a general rule, observational data in science lacks significance and utility without a theoretical construct to organize those observations. Theory in turn dictates what observations are made-and which ones are judged important. Thus, for example, prior to the elaboration-and acceptance- of the current model for volcanogenic base metal deposits, the structural aspect s of these deposits were most closely observed and studied by explorationists. The nature of the enclosing rocks and any attendant alteration was given minimal attention, and certainly didn't figure prominently as an exploration guide.Similarly, the importance of alteration features to exploration for porphyry copper-molybdenum deposits was only perceived when a theoretical model was developed to account for these aspects. Indeed, many of these porphyry copper deposits were regarded as epigenetic vein deposits by geologists of an earlier era observing and examining on a different physical scale-and with a different theoretical bias.In constructing and evaluating such conceptual models, explorationists primarily rely on observation data and proximate associations; speculative thoughts as to ultimate provenance or crustal evolution clearly play a subordinate role, as Dr. Ridge argues. This, however, should not obscure the fact that concepts and theories do indeed exert a major influence in mineral exploration."

Jan 1, 1983

By J .. R. Dalton

"Blasting in high sulphide content ores presents at least two major safety considerations: (1) compatibility of the explosives with the ore while resident in the borehole; and (2) introduction of a flame and shock producing explosive into this environment, while minimizing the risk of reactive ignition in the chemical reaction products/sulphide dust cloud resulting from the detonation. This paper will discuss only the second consideration, i.e. post detonation reactivity.The ETI (Explosives Technologies International) Technical organization, in consultation with the U.S. Bureau of Mines, reasoned that the most relevant considerations in the development of an explosive for this application are:• minimization of reactive gaseous detonation reaction products;• flame duration reduction;• flame temperature reduction;• increased explosive sensitivity;• reduced probability of ""low order"" detonation; and• maintenance of energy level as high as possible.Obviously, not all of these are totally independent properties, i.e. increased sensitivity will reduce the probability oj low order detonation as will higher energy levels. However, these considerations were examined separately as if they were independent."

Jan 1, 1994

By C. Chongo, L. Little, Q. Mclennan

Since commissioning in 2005, First Quantum Minerals’ Kansanshi Mine in Zambia has produced over three million tons of copper and 1.8 million ounces of gold from a deposit with highly varied copper mineralization. The processing plant is complex with three independent flotation circuits, gold gravity concentration, atmospheric and high pressure leaching, solvent extraction, and electro-winning. For the first ten years of operating the plant, copper mineralogy was inferred from total copper and acid soluble copper assays, and various misconceptions developed about the mineralogy which impacted operational strategy and project decisions. In 2015, an on-site mineralogy section was set up with an Automated Scanning Electron Microscope, the Zeiss MinScan. This instrument has provided detailed mineralogical data that have debunked some of the mineralogy myths that had developed, highlighting the key underlying issues affecting processing performance. This has enabled the development of projects targeting losses of specific copper minerals in defined size classes, unlocking significant value. This paper describes some of the early misconceptions around mineralogy at Kansanshi processing plant, outlining projects that have benefitted from understanding copper mineral distribution. Learnings from Kansanshi are to be applied at other FQM sites, with a similar mineralogy program being set up at the Cobre Panama project. INTRODUCTION The deposit Kansanshi Mine is located in the North Western Province of Zambia, and it has been the largest copper producer in Africa for over a decade. The deposit occurs within a broad northwest trending antiform that can be traced for 12 km, hosted in a zone of complicated faulting, abundant vein injection, breccia development and down-dropped rock units that lies within Kansanshi’s mining license. The copper mineralization within the deposit is predominantly vein-hosted, although some is strata-bound, occurring in thin bands and veinlets parallel to foliation, and some is disseminated associated with albite-carbonate alteration (Gray, 2015). Supergene enrichment has led to significant variety in the copper mineral speciation. This alteration is complex, and has not followed the text-book principles with a neat layer of supergene mineralization overlying fresh hypogene ore. Rather, the occurrence and extent of oxidation and supergene enrichment is highly irregular throughout the deposit, sometimes occurring at significant depth in localized pockets and along fault lines. Gold mineralization tends to follow the copper within the deposit, but it is dominated by coarse-grained, free-milling native gold. The extent of copper oxidation – measured as the fraction of total copper that assays as acid soluble – is used to classify ore into three main ore types, named Sulphide, Mixed, and Oxide, which are then fed to three different primary crushers for processing in independent circuits.

Jan 1, 2019

By H. R. Manouchehri, A. Weh

"High voltage electric pulse comminution (SELFRAG) relies on inducing electrical breakdown that occurs when the resistivity of a dielectric is insufficient to completely block all transfer of electricity while the conductivity is not high enough to fully accommodate the flow of electricity without considerable changes to the crystal lattice. The technology is based on introducing the electrical discharges into solids immersed in water and placed between two electrodes. The technology has received significant attention since investigations have revealed the potential for fully fragmenting particles or pre-weakening rocks in order to reduce the energy consumption in comminution practices, improve liberation and potentially increase the recovery in mineral processing. Mineralogical analysis of samples showed possible liberation at coarser sizes by high voltage breakage in comparison with conventional mechanical comminution.This study explored the potential of implementing SELFRAG to treat the Sandvik’s Mittersill mine tungsten ore (scheelite) for recovery improvement. Accordingly, standard SELFRAG tests were conducted on four samples from the tungsten process plant to evaluate the energy-breakage relation and potential to liberate the value minerals at coarser size fraction for recovery improvement. The size reduction of the ore after processing with SELFRAG revealed that size deportment occurs at 0.4, 0.2, and 0.1 mm, which indicated potential liberation of gangue and target minerals at respective sizes. In comparison with conventional milling, the difference is the deportment of values into 0.4 mm sizes, which was, to some extent, confirmed by SEM liberation analysis. However, more tests are needed to proof the concept. The study has indicated that, despite consuming more energy in comparison with conventional mechanical comminution, there are promising prospects in liberating the values at coarser fraction and improve recovery by making use of SELFRAG. The energy consumption can be reduced through customized generator and equipment setup, which must be further investigated."

Jan 1, 2016

Orebody classification systems ? Modern classification systems ? Genesis and environment of deposition (Important in economic geology) ? Shape and structure / Form, texture and mineral content ? Mining and geomechanics ? Size ? Massive versus tabular Requirements for mining method selection ? Classification of ore deposit ? Shape, size, attitude, continuity ? Grade and distribution, strength and large scale structures present, mineralogy and small scale structure, host rocks ? Classification of mining method ? Method of support (Stress ? strength ratio) ? The method selection ? Geographical and economic factors of the location

Feb 1, 2008

By G. Heinrich

Size by size recoveries and pentlandite liberation data from image analysis were used to evaluate plant tests of pentlandite flotation and pentlandite/pyrrhotite middlings flotation from pyrrhotite in a circuit treating low grade magnetic intermediates at the Strathcona Mill. Raising the pH with lime gave improved selectivity for liberated pentlandite but there were major losses of middlings unless the circuit was pulled hard indicating the need for finer regrinding. However, size by size recoveries at the normal regrind showed that, while the pentlandite recovery improved in the finer ranges, the pyrrhotite recovery also increased leading to little selectivity in any size range. A much finer regrind gave greatly improved selectivity in all size classes suggesting that 'surface polishing' as well as liberation effects were being seen. Using liberation data from image analysis of the products, surface polishing accounted for over 99 % of the improvement in selectivity. Unreasonable recoveries of more highly liberated particles were observed for liberation analysis by volume fraction but showed the expected trend in recovery when the analysis was based on surface liberation. The surface liberation data showed that the improved pentlandite recoveries after finer regrinding were to more than 90 % caused by improved liberation with the remainder contributed by surface polishing effects. The practical implications of this work are that i) the comparison of particle grades with product grades allows to estimate the effect of regrinding on co-flotation/entrainment, ii) surface liberation models should be used for evaluating recoverabilities by flotation and iii) regrind circuits may be set up to ensure that all particles go through the mill or that only the coarse fraction is reground depending on the surface scrubbing found to be required.

Jan 1, 1993

By R. C. Lo, M. D. Scott

"This paper reviews tailings management at Highland Valley Copper, and outlines main features of its tailings storage facility enclosed between the H-H and L-L dams. Key management focusses are: energy efficiency, cost effectiveness, safety and integrity of the tailings impoundment, environmental protection, and reclamation after decommissioning. Main features of the tailings facility include: high international standards for seismic and flood design criteria, water management and water quality monitoring, operations and construction optimization, reclamation and decommissioning plan, and geotechnical challenges associated with the complex geology of the L-L tailings dam foundation.IntroductionHighland Valley Copper stores its tailings mainly in the Highland Valley tailings facility (ultimate capacity: 1.8 billion tonnes). Smaller tailings storage facilities were operated by predecessor companies: the Number One Pond, the Trojan Pond at Bethlehem and the Highmont Pond at the Highmont operation as well as backfilling the Heustis and Jersey lona Pits at Bethlehem. These areas are currently not in use, and are in the reclamation phase prior to decommissioning. This paper focusses on tailings management in the main facility. As indicated in Figure I, the facility includes three tailings dams: these are, going from east to west, the H-H, J-J and L-L Dam, named after the alignment alternatives in the initial feasibility studies. From 1970 to 1977 Canadian Bechtel Ltd. advised Highland Valley Copper's predecessor company Lornex, on tailings storage at the H-H and J-J Dams and on the L-L Dam. Since the completion of the L-L Starter Dam in 1977, Klohn Leonoff Ltd. has provided ongoing consultation and construction monitoring of the raising of the L-L and the H-H Dams. The J-J Dams is currently buried by deposited tailings. This paper reviews key tailings management focusses and main features of the tailings facility."

Jan 1, 1992

By Zhang Wei

"Pulang Copper Mine is located in Shangri-La county, Diqing Prefecture, Yunnan Province, with currently defined copper reserve of 4.8 million tonnes of copper metal and an average grade of 0.34% Cu. The mineralized zone in a dome shape is 2,300 m long, 600–800 m wide, and 1,000 m high. At present, the project is at a construction phase, with a first-stage mining and processing capacity of 12.5 million tonnes of ore per year. Ore haulage is planned via a drift and ore pass development system. The cavability of mineralized rock is classified into three types (II, III, IV), with type III accounting for more than 98% of the total reserves. The cavability of the orebody is generally considered to be good and block caving mining method is planned. Semi-autogenous grinding and ball milling are adopted for the mineral processing. The tailing dam construction method is a center-line method.INTRODUCTIONAs the China's largest underground nonferrous mine, Pulang Copper Mine is located in the northeast of Shangri-La County, Diqing Prefecture, Yunnan Province, China. It is 62 km northeast of Shangri-La city. Shangri-La County is a Tibetan-dominated, multiple-ethnic region, with a population of approximately 163,000 in 2009. The county is rich in mineral and water resources, thriving with tourism. Its economy is also dominated by agriculture. To date, the defined copper reserves at the Pulang Copper Mine is 4.8 million tonnes of copper metal at an average grade of 0.34% Cu. In addition, it contains a gold reserve of 145 tonnes, a silver reserve of 2,754 tonnes, a molybdenum reserve of 0.19 million tonnes, and a sulphur reserve of 10.5 million tonnes. The first-stage mining and processing capacity is planned at 12.5 million tonnes of ore per year. When it ramps up to this production rate, the mine will produce copper concentrate containing 50,000 tonnes of copper and molybdenum concentrate containing 968 tonnes of molybdenum. A drift and ore pass system is planned for ore haulage and mining method is a block caving method. Semi-autogenous grinding and ball milling are considered for mineral processing. A center line dam is adopted for the tailing dam construction (Feng, 2010; Feng, Li, & Wang, 2011; China Enfi Engineering Corporation, 2014)."

Jan 1, 2016

By Mariam Melashvili, Chris Fleming, Rene Jackman

"A study was undertaken to develop a flowsheet for treating a high grade silver/gold ore body by cyanidation, CCD and Merrill Crowe precipitation, with tailings detoxification to meet stringent limits for cyanide and thiocyanate concentrations in the final discharge. In one of the flowsheets examined, free cyanide in the final leach liquor was recycled to the mill where it was hoped that it might react beneficially with fresh ore to reduce the cyanide makeup by an equivalent amount. However, laboratory results suggested that most of the cyanide recycled to the mill reacted with iron forming a soluble ferrocyanide complex. This would have had a negative impact on cost, not only because the cyanide recycled to the mill could not be claimed as a credit, but also because the presence of ferrocyanide in the final tailings meant copper sulphate had to be added to the SO2/air cyanide detoxification process to precipitate the iron cyanide. In an alternative flowsheet that was examined, recycling of cyanide to the mill was abandoned, and this allowed the milled slurry to be pre-aerated in a single mixing tank before cyanidation. During alkaline pre-aeration, any ferrous ions that are generated in the mill are oxidized to ferric ions, which, unlike ferrous ions, are inert in cyanide solution. This significantly reduced cyanide consumption and lowered costs in the detoxification of the tailings. In this paper, the cost implication of these two circuits is compared.INTRODUCTIONMost of the gold that is produced by hydrometallurgical processes is recovered by cyanide leaching. The reason for that lies in the superior thermodynamic stability of the gold cyanide complex and the favorable economics this confers on the process (Fleming, 2014). However, the gold in most of the gold-bearing ores processed is a very minor component, and therefore, the leaching response is often dominated by that of the host minerals.Many gold ores treated by the cyanidation process contain iron minerals. Cyanide reacts readily with some iron minerals forming ferrocyanide as one of the compounds. Ferrocyanide is stable when solutions are exposed to air and does not retard the dissolution of gold. In fact, it has been claimed that potassium ferrocyanide in the presence of oxygen is a weak solvent for gold (Hedley & Tabachnick, 1958). The main problem with the formation of this compound is the consumption of cyanide. Ferrocyanide contains six molecules of cyanide for each atom of iron {Fe(CN)64-} so the wasteful consumption of cyanide is greatly increased by its presence. Thiocyanate is also often produced during the reaction of certain iron sulphide minerals with cyanide, and contributes to the wasteful consumption of cyanide. In addition, environmental regulations in certain countries demand that thiocyanate be removed from the tailings, and this adds significantly to the cost of tailings treatment."

Jan 1, 2016

By M. Leroux, S. R. Rao, J. Kim, J. A. Finch

"Continuous in-plant testing of collectorless Cu/Pb bulk flotation on Lyon Lake ore at Matlabi Mines Ltd. Was conducted using a portable circuit based on 5 L mini flotation cells. It is concluded that collectorless Cu/Pb flotation is a reliable phenomenon for this ore over the usual range of plant operating conditions.IntroductionFlotation of some sulphide minerals without the use of conventional collectors (e.g. xanthates) is now widely recognized. The requirement appears to be some degree of oxidation, although the nature of the surface product formed is still uncertain (Luttrell and Yoon, 1984; Buckley and Walker, 1988). The phenomenon has been termed ""collectorless"" or ""self-induced"" flotation. One of the minerals most responsive to coUectorless flotation is chalcopyrite; in contrast pyrite and sphalerite show little response and galena usually shows intermediate response (Hayes et al., 1987; Shannon and Trahar, 1986).Most of the work on collector1ess l1otation has involved single mineral or batch flotation on ore samples. There are only occasional references to collector1ess l1otation under plant conditions (Sandstrom and Jonsson, 1988; Vargas, 1990; Boyce et al., 1970). Creating and maintaining the appropriate oxidation conditions and differences in water quality are among the reasons why the phenomenon may not transfer readily to the plant (Grano et al., 1990). Periodically from the spring of 1989, Mattabi Mines Ltd. ran full-scale tests of collector1ess bulk CulPb flotation while treating Lyon Lake ore*: the observations confirmed the laboratory finding that chalcopyrite and galena floated without collector (Leroux et al., 1989).To explore this finding continuous in-plant testing using mini flotation cells was conducted which is the subject of this paper. The main objective was to determine if collectorless flotation was a reliable phenomenon over the expected range of redox conditions in the feed pulp to bulk CulPb roughing. As background, the previous work (Leroux et al., 1989; Martin, 1988) is briefly reviewed."

Jan 1, 1994

By C. J. Li, J. L. Feng

In the present study we focuses on developing the poroelasticity model that deals with adsorptioninduced permeability change mostly occurred in porous media constituted several phases such as coal. The underlying pressure induced by adsorption is obtained by Virial expansion form, which is substantially founded on statistical physics. The corresponding thermodynamic pressure applying on the pore surface is then used to detail the pore pressure and further to evaluate the macroscopic volumetric strain and the porosity. In the process of physical adsorption, the adsorbed phase is in thermodynamic equilibrium with the gas phase regardless of pore size, and the corresponding chemical potentials are all equal. The relationship between surface strain and volumetric strain is derived under infinitesimal deformation conditions to gain an explicit formulation of pore surface area with respect to volumetric strain and porosity. After the formulation of surface stress modified by the Langmuir isothermal adsorption is derived, the differential micromechanical constitutive equations of porous media are obtained. By supposing that the ratio of current permeability to initial is equal to the cubic ratio of current porosity to initial porosity, the differential equations for permeability change is consequently derived. The numerical simulations by the present model for permeability change of coal induced by adsorption of CO2 and CH4, respectively, are presented under confined stress conditions. The predictions from the model are good in agreement with the experimental data of sorption-induced permeability change of coals in the literature.

Jan 1, 2015