Search Documents

By S. Torizuka, I. Mizushima. Kawasakitohri, A. Ohmori, K. Nagai

Strain (work)-hardening in tensile tests were examined for low carbon steels with various ferrite grain sizes ranged from 0.4µm to 16µm. The steels had microstructures composed of ferrite grains and dispersed cementite particles. They were fabricated through warm caliber rolling with an accumulative area reduction of 93%. Strain-hardening rate at a given strain increased with an increase in volume fraction of cementite particles. The balance of yield strength and uniform elongation for ultrafine-grained structures could be improved by the dispersion of cementite particles. Effects of the cementite dispersion and the ferrite grain size on the strain-hardening rate can be roughly explained by the work-hardening model with GN-dislocation density. Strain-hardening design using dispersed cementites was proved to be effective in controlling ductility of the ultrafine-grained steels.

Jan 1, 2004

By Akira Fujisaki

"The oil crisis accelerated the change of non-ferrous metals' demand structure. Maturing societies in developed countries and preference for lighter, thinner and smaller products are eroding the non-ferrous metal industries' growth potential. Inventory-control, stockpiling and developing new demand are measures Japanese smelters have taken to cope with the changing demand.The most effective means for risk management of product demand lies in the cooperation between ore producing countries and metal consuming developed countries to assist developing countries in their efforts to ""take-off"", which in turn will bring about a surge of demand for metals.SummaryThe non-ferrous metal industry in the world is suffering its most serious slump since the war. With some of the markets of the advanced industrialized countries approaching saturation point and economized usage of natural resources and substitution growing, the possibility of a quick recovery of the demand for base metals is dim.To cope with the changing product demand Japanese producers have had recourse to such measures as strict inventory control and stockpiling for the purpose of stabilized imports. They have also tried hard for securing raw materials and promoting new field s of demand but the very core of ""risk management"" has been the diversification of line s of business to bolster and stabilize the foundation of management of the non-ferrous metal industry in Japan.To see the demand for nori-ferrous metals recover from the slump and be put on a path of solid development, we have to wait for the economies of the developing countries to ""take off"" and for its realization the economies of the developed countries must be reactivated with new growth industries playing a leading role, and the transfer of technology and money recycling must be carried out smoothly under an orderly international trade system."

Jan 1, 1983

By Jaeheon Lee

"Biooxidation of gold ores or concentrates could be a very attractive alternative to pressure oxidation (POX) or roasting to liberate the gold grains from various sulfides. Crushed heap bioleaching was successful in US and many operations using tank bioleaching of gold concentrate are currently running around the world. Many parameters need to be considered during the project of sulfidic refractory gold ore process. Capital and operation costs are among the most important ones. Run-of-mine heap biooxidation could be very inexpensive and the smaller the crush size (particle size), the more expensive the capital and operating costs for biooxidation application are expected. The capital cost of biooxidation could be a fraction of the cost for building POX plant or roaster and the operating cost could be 1/3 of POX or roasting depending on the method utilized. A new biooxidation process, Sand Farming, is introduced as an alternative to POX and tank biooxidation process. A relatively coarser particle size (P80 = 650 µm) of the process benefits the low cost of grinding against the conventional grinding size (P80 = 75 µm) for other options. The cost of Sand Farming is less than 40% of that of pressure oxidation with comparable gold recovery from the downstream process. This paper will review the laboratory scale testwork for various biooxidation process of sulfidic refractory gold ores and concentrates and provide the economic evaluation showing the biooxidation could be the most economic method without much sacrificing the overall gold recovery. INTRODUCTIONThe decreased availability and lower grade of raw materials has motivated industries to consider recovering values utilizing low cost process options. The process may treat high grade concentrates or submill grade ores that cannot be processed economically by conventional milling-flotation or leaching. Sulfidic refractory gold ores/concentrates have been economically processed by roasting, pressure oxidation, and biooxidation in stirred tank reactor. The process selection is based on a series of studies including multi-year long ore characterization and metallurgical investigations."

Jan 1, 2016

By H. Nejati

Experimentally, the Semi-Circular Bending Moment (SCB) fracture toughness test results of Basalt Specimens Under Illumination (BSUI) have shown reduction in fracture toughness and failure force as a result of micro-cracking. The fractographic investigation of BSUI confirms initiation and extension of micro-cracks. Determination of a relation between strength reduction (herein fracture toughness reduction) and density, location and orientation of thermo-mechanical induced cracks due to microwave radiation is critically important. Numerical modeling can bridge strength reduction and the density of thermal microcracks generated due to microwave radiation. Discrete Element Modeling (DEM) is a power tool for simulation of micro-crack initiation, coalescence into macroscopic fractures and failure mechanisms in brittle rock specimens under different stress regimes (herein combination of pure tensile stress due to SCB testing, and thermal stress due to microwave radiation). For this purpose, a DEM modeling of SCB testing of basalt using EDEM (i.e., a DEM based software). DEM models are calibrated according to results of experimental SCB testing as reported in previous papers. This paper first reviews some background data on SCB fracture toughness, and experimental results of fracture toughness of microwave treated SCBs. Then it proposes a new methodology for simulation and validation of rock samples exposed to microwave illumination with regard to experimental results, and discusses the correlation between fracture toughness of BSUIs and density of micro-cracks, which is attributed to applied microwave power and duration of illumination.

Aug 1, 2013

By Jorgen Elbrond, Yve Lizotte

"A mine evaluation method based on the use of a computer program that models mining with an open-ended dynamic program is presented in this paper. It is demonstrated with an example how the method is applied, how some of the decision variables are related in the particular industrial environment and how these decision variables affect the economic benefits of mining.IntroductionTwo distinguishing characteristics make mining a particular industrial environment: exhaustible resources of a given ore deposit and heterogeneousness of the ore grade spatial distribution in the ore deposit. These characteristics, inflation, uncertainty and cyclical price variations which greatly affect estimated cash flows also contribute in rendering difficult the evaluation of the economic outcome of mining at the preliminary planning stage.Decision variables and their ranges are associated with the mine plan; basically, they include choices of the mine's nominal capacity (mining and milling), the sequencing of mining through the deposit, the ranges of possible production rates and cutoff grades, and the stockpiling policies. The mine's nominal capacity must be decided at the planning stage, but this capacity choice must take into account flexibility to modify other decision variables as mining commences and uncertainty resolves.Although it is generally accepted in discounted cash flow analysis that the sequence of mining must proceed from the richest to the lowest-grade stopes (with correspondingly ajusted cutoff grades), this may not produce optimum benefits when cyclical price variations are considered.Mining rates and cutoff grades can also be adjusted to changing economic conditions, taking into account the limited resources of the ore deposit. Thus, when prices are thought to be in the trough of a cycle, production can decrease to preserve ore for expected greater future profits. When prices rise, mining rates can increase possibly even over the mine's nominal capacity. In both cases, the machinery's effectiveness shall not be-optimally utilized; this will be reflected particularly by the variations in the concentrator's metal recovery and the concentrate grade output."

Jan 1, 1982

By Andrew L. Mular, Robert P. Edwards

"The operation of flotation circuits is often regarded as a combination of art and science. Expert systems offer a method by which the art may be captured and supervisory control of flotation circuits fully realized. Operating knowledge, the art, can be consistently employed to enhance regulatory control through the judicious application of an expert system. Using an expert system, a supervisory control routine was developed, and success- fully implemented, in the copper flotation circuit at Brenda Mines Ltd.The expert system ran in conjunction with regulatory PI controllers on a personal computer. The expert system received assays via an on-stream analyzer and adjusted regulatory loop set points as required in real-time. From its commissioning in November, 1989, to the end of the mine 's operation in June, 1990, it was enthusiastically embraced by the operators and attained operating levels superior to those achievable manually.IntroductionExpert system (ES) software springs from research into artificial intelligence and is currently making significant inroads into business and industry. ES proponents make many attractive claims; they are a means of capturing the knowledge of experts and they can be programmed by non-programmers. To date, most uses of this software in the process industry are in off-line applications, meaning that the applications are not tied directly to operating (on-line) environments. Moreover, in on-line environments, they are typically employed as advisors and only suggest changes. Human operators are required to close-the-loop to the process. Yet, an ES should be applicable to operating environments and, if the claims of the proponents are valid, should also be better than existing tools. As an intelligent controller an ES must use the knowledge of experienced operators, apply it directly to a process and do this without the intervention of human operators. On-line applications have been successfully employed in the closed loop control of SAG circuits (Herbst et al., 1989) and flotation circuits (Hales, 1989). Harris and Kosick (1988)detail an implementation for flotation control at the Polaris Mine."

Jan 1, 1992

By M. A. Bérubé

Le but principal de cette étude était de vérifier certaines hypothèses de nature minéralogique susceptibles d'expliquer en tout ou en partie les variations importantes observées au concentrateur no 1 de Mines Gaspé quant aux performances du circuit B de broyage et de flottation. A cette fin, nous avons examiné six séries d'échantillons prélevés lors d'une campagne de mesures effectuée au cours de l'été 1980. Ainsi, la capacité du circuit de broyage semble dépendre principalement devariation s dans les caractéristiques minéralogiqu es et texturales du minerai, par exemple du rapport grenat/quartz, le grenat ayant une influence néfaste sur le rendement de cette étape, contrairement au quartz . Quant au processus de concentration, la fraction du cuivre sous f orme de minéraux difficilement récupérés par flottation, en particulier des carbonates de cuivre, varie de façon significative dans le minerai, et cela peut certes expliquer en partie des récupérations parfois plus basses. Malgré ces variations important es de la composition minéralogique globale du minerai et de sa broyabilité, le degréde libération des sulfures de cuivre dans le produit de broyage dépend presque seulement de la granulométrie de ce produit. Afin de garantir des performances égales à l'étape de concentration, il est fortement suggéré de contrôler cette granulométrie à un niveau constant.

Jan 1, 1984

By Patrick J. Williams

Outline -An Australian View On: ?IOCG defining features and occurrence ?Variable exploration characteristics ?Extracting value (gold metallurgy) ?Recent exploration experience(case study)

Apr 1, 2005

By Yasuo Iizuka

We have had studied CO oxidation on unsupported Au powder (mean particle size, ca.100nm) manufactured by evaporating ultra high purity gold metal (>99.99%) in inert gas and reported that it showed some activity after oxidizing pretreatment in O2 at 423 K?453 K. However, recent XPS analysis of the Au powder revealed that it contains much amount of impurity metals such as Ag and In at levels which far exceed those expected from the impurity level of raw gold metal in the bulk. Several samples of Au powder containing different amount of impurity metals were prepared to examine whether the activity depends upon the existence of surface impurity or not. Activity measurements were performed at 273 K after undergoing the powder under various pretreatment conditions. Although the activity of Au powder varied to some extent according to the pretreatment condition, it is strongly correlated to the surface concentration of Ag. Such dependence was not found for In, indicating that the activity of unsupported Au powder is mainly due to the existence of Ag in the surface layer. The activity attributable to ?particle size effect? was not recognized for Au powder with a mean particle size larger than 80 nm.

Oct 1, 2003

By K. T. Aye

An investigation into the leaching of chalcocite and covellite in cyanide solutions at concentrations typically encountered daring gold cyanidation has been conducted. The results indicate that, for both minerals, the extent of leaching is greater under anoxic conditions, but is still incomplete even in the presence of free cyanide ions, with undissolved copper solids remaining in equilibrium with solution species. The speciation of the sulfur and cyanide reaction products in solution are interpreted in terms of the fast formation of a copper(I)- cyanide complexes in solution and a sulfur-rich copper(I) polysulfide solid phase, which then reacts more slowly to produce thiocyanate ions.

Jan 1, 2011

By K. S. Coley, M. A. Rhamdhani, G. A. Brooks

Interfacial phenomena in high temperature reactions such as between iron alloy and slag is well documented but not fully understood. It is believed that a gradient of oxygen concentration plays an important role to the occurrence of such phenomena. This article describes the results from the continuation of the study of interfacial phenomena between Fe-Al alloy droplets and CaO-SiO2-Al2O3 slag. Materials characterization techniques involving microscopic observations, depth profiling, bulk, point analysis and were carried out. The roles of oxygen as well as other factors that contribute to the interfacial phenomena were evaluated. The results and their implications to steelmaking will be discussed.

Jan 1, 2004

By J. B. McKenzie

Since connnencing underground prcxiuction in 1979, the Ruttan Mine has been prone to secon:iacy sulphide dust explosions. Al though infrequent during the early years of prcxiuction, these occurrences did result in major damage and lost time injuries. 'As the mine exparrled and developed to further depths, sulphide dust explosions occurred on a more frequent basis. Incomplete ventilation se:rvices, required to exhaust the affected areas, caused frequent delays resulting in lower prcxiuction rates due to the time required to ventilate the affected areas of the mine. CUrrent procedures to minimize the effects of secon:iacy dust explosions evolved from practical suggestions arrl examining methcx:ls other mines have developed to cope with the problem. Procedures and regulations to protect errployees from exposure to hazards of sulphur dioxide are time consuming, expensive and counter prcxiuctive in their present fonn. This paper describes the history of secon:iacy sulphide dust explosions at the Ruttan Mine and the methcx:ls and proced.ures currently in place to minimize and contain the effects of dust explosions.

May 11, 1988

By J. C. Kurnia

Methane is recognized as one of the prime causes of underground mine disasters around the globe. A cost-effective mine ventilation system and methane control is required to ensure a safe and productive environment in an underground mine whilst keeping energy usage and operating cost at minimum. Typically methane enters a mine environment or tunnel from localized distributed sources at high initial concentration. Hence, an understanding of its dispersion from discrete sources is important to design a methane management system via effective ventilation. This study employs computational fluid dynamics to model methane dispersion in an underground tunnel which has a number of discrete sources of methane and effective ways to dilute and or disperse it. Air flow distribution within the tunnel as well as methane dispersion is simulated by solving the governing transport equations subject to appropriate boundary conditions. First, the effectiveness of ventilation duct placement is examined. Several possibilities are explored and investigated. It is found that the common configuration utilized in underground mine performs best as compared to other configurations in maintaining the concentration of methane below permissible levels. Next, a novel intermittent airflow ventilation system is proposed and evaluated via simulation with the goal of reducing the energy cost whilst maintaining methane level in the mining face below the allowable level. Parametric studies are conducted to investigate effects of various factors influencing the effectiveness and performance of this novel intermittent ventilation system. This study will provide some new ideas for designing an efficient and effective underground mine ventilation system by lowering the net average amount of air that needs to be circulated in the tunnel for a safe operation. KEYWORDS

Aug 1, 2013

By E. Contestabile, T. R. Craig

"This report describes the development and effective use of shaped charges as part of the Elliot Lake Mine Roof Stability Project to remotely remove the heads from roof bolts. With a slight modification, these same shaped charges are being recommended f or use to the Brunswick Mining and Smelting Corporation Limited (Mining Division), to cut steel cable bolts.IntroductionThe Canadian Explosives Research Laboratory (CERL) often receives requests to cooperate in solving problems encountered in private industry or other sectors of the government. CERL is equipped to design and test explosive and pyrotechnic devices and the policy is to treat each case individually.The first case reported evolved from a request from a sister laboratory at Elliot Lake. The intent was to remotely remove the head s of roof bolts as part of a mine roof stability project. The device designed for this use was 1000,70 effective in the laboratory and 80% effective in the mine.The second case reported results from a request from a private mining company knowledgeable of the Elliot Lake Project. Their requirement was to remotely cut cable bolts. This request was first treated as presenting a new problem. The solution, however, proved to be very similar to the former."

Jan 1, 1985

By D. A. Beattie

Talc is a commonly encountered gangue mineral in metal sulfide flotation. Talc is naturally hydrophobic, resulting in high recoveries if polymeric depressants are not used to specifically reject this MgO containing mineral. We have studied the adsorption of a selection of polymers onto talc using a variety of techniques. Adsorption isotherms have been determined using ex situ depletion techniques and in situ ATR-FTIR spectroscopy has been used to determine adsorption kinetics. Adsorbed layer thicknesses have been determined for the polymers on cleaved talc surfaces using the AFM. The effect of the adsorbed polymer layer on the properties of the talc surface has been quantified through contact angle measurements and single mineral flotation tests. Distinct correlations are observed between the adsorbed layer properties and the flotation performance of the polymers. These observations are discussed with reference to the bubble-particle attachment process and the molecular structure of the polymers.

Jan 1, 2006

By J. Thiriar

The electrolytic tan/chouse at CCR was recognized by management as lagging behind modem refineries in terms of productivity, energy efficiency and controls. The operation was also burdened by high maintenance costs of cells, floors and electrolyte recirculation systems. A bench marking program was started in 1986 to evaluate processes and other technology by visiting major copper refineries in North America, Europe and Japan. The basic principles necessary to optimize the operation were defined, and a program called CCR 2000 was prepared for approval of the necessary capital investments. This paper describes the results obtained to date and outlines the remaining work to complete the modernization program, in particular, the control of electrolytes, the elimination of the Baltimore groove and studies to modernize the stripping operation or adopt permanent cathode technology.

Jun 1, 1993

By W. Yang, R. Rajasingam, K. Mohanarangam

"Copper Electrowinning (EW) is a complex electrochemical process that involves the production of LME grade copper from copper rich electrolyte. The process involves the deposition of the copper ions onto the cathode from copper rich electrolyte with the production of oxygen bubbles at the anode. The process setups up a complex flow pattern within the cell as it is subjected to varying density gradients due to the deposition process along with oxygen bubble driven flow. It is a necessity to understand and quantify the flow behaviour within these cells in order to maintain the production of highest grade copper. In fact, the oxygen bubbles originating from the process is responsible for the generation of acid mist which is a designated as a carcinogen a major health hazard around EW tank houses. Hydrodynamic assessment of the process has so far been restricted to simple mass balances and some limited numerical modelling. All the models are based on assumed boundary conditions which has not so far been verified by any real-time physical measurement. This apparent gap has led to models which could not be directly used to track process changes or troubleshoot problems in EW tank houses. In order to address this gap, CSIRO has established a full size (width and height) transparent cell capable of simulating plant operating conditions (across the range currently used). With the use of sophisticated diagnostic analytical tools and measurement techniques it was possible to study all the operating variables (current density, flow rate, temperature, etc.) independently and their effect of bubble size, bubble velocity, gas hold-up as well as acid mist generation and its size. In order to address safety concerns in tank houses around acid mist early results outlining the factors contributing to its generation as well as the effect of various barriers to mitigate acid mist is outlined below.INTRODUCTIONA significant part of today’s copper production is through hydrometallurgical route which predominantly involves leaching, Solvent eXtraction (SX) followed by ElectroWinning (EW). Producing copper using this approach have shown to be environmentally friendly (Dresher, 2001) compared to the traditional smelting process. EW is the final step in the production of LME grade copper using the hydrometallurgy route. The electro-chemical process involves the use of a lead anode (Pb-Sn-Ca) and a stainless steel cathode to produce copper sheets using the copper rich electrolyte from the SX process and with the applications of direct current to the electrodes. This electro-chemical reaction results in the deposition of copper ions on the cathode with oxygen released from the anode as a by-product. Hydrodynamically, the oxygen bubbles create a bubble driven flow within the EW tanks with the surrounding electrolyte. A direct result of this could be seen from the quality of the copper deposited on the cathode. Most of the copper plates produced from the traditional tank houses have a rough texture at its bottom one-third while the top two-thirds have a smooth finish with a finer grain structure."

Jan 1, 2016

By A. M. Reyes

Flow field hydrodynamics of serpentine flow channels was investigated numerically using computational fluid dynamics (CFD). The velocity profile simulated by the CFD model was evaluated with respect to experimental results from the literature. Rectangular and tapered flow channels were compared with respect to mixing and water management capabilities, and pressure drop. The CFD model was further developed to account for electrochemical reaction on the cathode side to determine which channel configuration was most effective in reactant conversion. The velocity profile differences between the channels were found to impact reactant conversion, as the rectangular channel had the highest conversion. With respect to water management, although the tapered channel was found to have a higher overall pressure drop, the rectangular channel was found to have higher shear and pressure forces acting on simulated liquid water droplets in the channel.

Jan 1, 2005

By R. Kamguem

The surface of a mechanical part plays an important role in determining performance in service. The presence of scratches left by the cutting or tearing of the material on the surface of the workpiece supports the concentration of stress and strain. This article presents the experimental study for high speed milling of the aluminum alloy 7075-T6, using cutting tools different by the nose radius and coatings (TiCN, TiAIN, TiCN + A12O3 + TiN). A multi levels factorial design of experiment (DOE) and statistical analysis was used. The roughness parameters investigated are Ra, Ra, Rv, Rc, Rsm, and Rk. The results show that the feed rate, the types of coatings and the geometry of the cutting tools have the most significant impact on the surface roughness profil. Surface finish charts according to feeds and cutting speeds were established for each tool tested.

Jan 1, 2011

By R. D. Studer

"The Snow Lake massive sulphide deposits are hosted by Aphebian volcanic rocks of the Flin Flon - Snow Lake greenstone belt, which in this area were deformed and metamorphosed to the amphibolite facies during the Hudsonian orogeny. All the known deposits occur in felsic rocks a short distance below the contact with an overlying mafic rock unit.The Stall Lake copper deposit occurs close to the top of an explosive felsic volcanic sequence. Rocks stratigraphically underlying the deposit have been hydrothermally altered by the mineralizing fluids. The sulphides were probably deposited from submarine volcanic vent(s) on the flanks of a felsic dome. The ore has been tightly folded, flattened and elongated parallel to the northerly trending lineation of the surrounding rocks during the several periods of deformation. Strike lengths of the lenses range from 60 to 300 feet and plunge-to-strike ratios are as much as 15:1.Ore lenses 1 to 4 typically consist of massive coarse-grained pyrrhotite, chalcopyrite and pyrite. A stratigraphically higher lens differs in that it contains fine-grained pyrite and chalcopyrite, with an increase in sphalerite toward its hanging wall. The No.4 orebody has a distinct footwall alteration zone characterized by brecciation and abundant chlorite-staurolite-garnet schist, with minor kyanite, anthophyllite, cordieriteand anhydrite, as well as sulphide minerals. Chemically, the alteration zone is distinguished from the unaltered felsic rocks by Na20 depletion and Mg-Fe enrichment.IntroductionThe Stall Lake copper deposit is located aproximately 4 miles southeast of Snow Lake in northern Manitoba (Fig. 1). The Snow Lake district has been a producer of gold (Rex, Bingo, Laguana and Nor-Acme Mines) and, since the fifties, of copper and zinc from deposits of Hudson Bay Mining & Smelting Co., Ltd . The district is located near the eastern limit of the Flin Flon - Snow Lake greenstone belt, which contains Amisk metavolcanic rocks of Aphebian age."

Jan 1, 1982