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By R. E. Whitehead

"The earliest gold-mining operations in Ontario included the Cordova, Deloro, and Sophia mines north of Lake Ontario (see for example, Miller and Knight, 1914). The Cordova deposit, worked intermittently between 1891 and 1940, is reported to have yielded 22 774 oz of gold from 127 670 tons of ore averaging 0.19 oz/ton Au (Gordon et al., 1979). The property remained inactive for many years. In 1988, Gunnar Gold Inc. and Mill City Gold Inc. conducted a drilling program along the main Cordova vein. The present study is based on core from three drill holes through the Cordova gabbro (Fig. 1) and the carbonate alteration zones enveloping the quartz-carbonate veins. The relatively narrow width of the alteration zone and the availability of continuous sections of core provided an opportunity to conduct a compact mineralogical-chemical study of carbonate alteration and its effect on the redistribution of rare earth elements (REEs). Although the Cordova deposit is not of great economic importance, this study has revealed a number of interesting features which are interpreted as resulting from processes that may be applicable to gold-bearing quartz vein deposits elsewhere.The Cordova gabbro is layered in places, varying from fine-to coarse-grained and in color from light gray (feldspathic) to dark gray-green (amphibolitic). However, layering within the section of the gabbro considered here and which hosts the Cordova gold deposit is mainly textural rather than compositional. Samples of unaltered gabbro selected for analyses were medium- to coarse-grained; amphibolitic and anorthositic phases were avoided as being less representative of the general chemical composition of the gabbro.The Cordova intrusion has undergone regional metamorphism and consists dominantly of actinolite and saussuritized plagioclase with smaller amounts of granular clinozoisite and flaky chlorite; minor quartz, ilmenite, titanite, apatite, and calcite are typically present. Some actinolite grains have irregular rims of pleochroic green hornblende that is optically continuous with the actinolite. Both chlorite and clinozoisite occur in two modes. Chlorite occurs as an alteration product of actinolite and as separate grains in the groundmass. Clinozoisite and albite occur together as regional metamorphic alteration products of original plagioclase crystals and as discrete grains in the matrix.The main gold-bearing quartz-carbonate occurrence occupies an easterly trending, steeply southward-dipping carbonatized shear zone up to 15 m wide and 700 m long. The gold occurs principally in irregular lenses and veins of quartz-carbonate up to a foot thick occupying the lower part of the schistose shear zone within the gabbro. This zone consists of chlorite, biotite, and carbonate and is flanked on both sides by chlorite-carbonate schist lacking biotite. The chlorite-carbonate schist in turn grades into regionally metamorphosed actinolite-bearing undeformed gabbro.The dominant sulfide within the quartz-carbonate lenses and in the surrounding schist is pyrite which occurs mainly as small cubes (1 mm to 2 mm) generally making up less than 10% of the rock. Rare blebs of chalcopyrite are present. Magnetite is common throughout the schist."

Jan 1, 2001

By Wayne F. Luinstra, Frédérique Vincent, André R. Laplante

"A test to determine the amount of gravity recoverable gold (GRG) in an ore is described. Typical GRG results are given; possible uses are discussed. A case study of how the technology was used at Hemlo Gold Mines is presented.IntroductionUsing gravity to supplement either flotation or cyanidation is a well established practice in the gold industry. It differs from most recovery circuits in that most of the gold recovered by gravity would be recovered in any case by the circuit downstream, be it flotation or cyanidation. The economic justification of gravity is therefore based on small margins (for example. a net smelter return of gravity gold of 99%, as opposed to 94% by flotation). It was easily demonstrated when either flotation or cyanidation were relatively inefficient processes, and labour costs low (as gravity can be labour intensive). Over the past thirty years, the advent of better flotation machines (flash, column, high capacity), more effective collectors, and better control systems has increased flotation's metallurgical performance, thereby decreasing the incentive for gravity recovery. Cyanidation technology has undergone similar changes, with the advent of activated carbon, oxygen and lead nitrate addition, and improved impeller design.Today, gravity could remain an attractive option only inasmuch as it can be implemented with very low capital and operating costs. This has resulted in a relative shift away from gold gravity recovery (except for alluvial deposits), in the seventies and eighties. For example, as of the early nineties, gold gravity recovery has disappeared from the typical South African flow sheet. The advent of the Knelson Concentrator, at the beginning of the eighties, foreshadowed a resurgence of gravity recovery, as gold's grinding and classification behaviour (Banisi, Laplante and Marois, 1991) makes it possible to achieve adequate gold recoveries with very simple, Knelson based, gravity circuits (Laplante et al., 1994).Consider for example the Hemlo recovery circuit, made of a single 61 cm x 122 cm (2' x 4') screen, an automated 76 cm (30"") Knelson feeding a Gemeni table, to produce a 70-80% Au concentrate which accounts for approximately one fourth of the gold production (about 3 million grams per year). The low capital and operating costs make it possible to justify the gravity circuit on the basis of savings in other operating costs (e.g. fewer carbon stripping and reactivation cycles). Any improvements in recovery, which would at Hemlo be difficult to measure, would be additional benefits. Such a circuit is rapidly becoming a standard in Canadian and Australian operations.The justification for installing a gravity circuit must be first based on an estimate of how much gold it will recover (irrespective of what the potential benefits are). This is a function of the nature of the gravity circuit to be installed; however, Knelson circuits, by their very simplicity and efficiency, limit the options. This leaves the amenability of the ore to gravity recovery as the single most important parameter. Various approaches can be used to characterize this response (Woodcock, 1993). The present work sought a route which would fulfil the following criteria:"

Jan 1, 1996

By S. E. El-Alfy, John Starkey

"The Iron Ore Company of Canada treats up to 125,000 t/d of iron ore at its Carol Concentrator in Labrador City, NF.A complete water balance study in the concentrator was done to show how to reduce the consumption of fresh water, to improve metallurgy in the magnetic separation (mag) plant, and to help reduce maintenance costs for the reclaim water and tailing pumping systems.The study showed that more than 60% of the water used in the mill was internally recycled dirty water from dewatering cyclone overflows, and that water reduction was closely tied to the effective use of these internal reclaim pumping systems. In addition, new operating parameters were set for the 4 -15,000 USGPM reclaim water pumps which should save over $100,000 per year in maintenance costs.IntroductionThe study described in this paper was set up for the purpose of lowering water usage in the concentrator, and to reduce tailing and process water pumping costs (operating and maintenance). Another benefit was also expected, namely, to improve magnetic separation efficiency through better water and density management of magnetic separator feed streams.The procedures selected to perform this work were: ( 1) to prepare accurate, as built flowsheets of the entire iron recovery process, including fresh and process water systems, (2) to calculate normal material balances in all circuits at full production, (3) to use the computer spreadsheet model so generated, to evaluate specific ways to reduce water consumption and (4) to re-evaluate metallurgical performance and operating parameters in the light of this information.Overall control of the 28 spiral iron recovery lines was found to be excellent because automated start up and shut down of the individual lines had been incorporated in the design from the start. Because production rates can vary due to sales requirements, mine and mill maintenance delays and hardness variance, the mag plant (which treats spiral tailings) must deal with a wide variety of operating conditions. Good water management therefore is a key item in achieving high recovery of the fine free magnetite which is too fine for recovery in the spirals.In order to make the study as accurate as possible, process data for major flows was reviewed by metallurgical staff and then by mill supervisors. The operating picture of the concentrator so generated was judged to be a good estimate of the mill at full production. By changing key inputs, the variance of process water demand and tailing slurry produced for several other operating conditions were studied.The usefulness of this exercise has prompted this present presentation to be made. Older plants by nature have undergone many revisions as operators have worked through ore changes, market changes, labour cost increases and the availability of new equipment, to improve their operation. Sometimes therefore it is necessary to stop and reassess what is happening in a plant in order to continue the never ending work of process optimization. The techniques used here were ideally suited to the gravity/magnetic concentration flowsheets used, but there is no reason why similar studies could not be done in other process plants.The authors of this paper hope that this experience at IOC will be helpful to others who face similar challenges in the pursuit of excellence in their processing plants."

Jan 1, 1995

By P. Nelson

Extending the campaign life of the Mitsubishi furnaces at Xstrata Copper's Kidd Metallurgical Division Copper Smelter has been a major focus of attention for many years. One aspect of this effort is real time monitoring to detect abnormal conditions and safely shut the furnaces down before significant damage occurs. Traditional real time methods of monitoring the integrity of refractory furnaces containing molten metal include alarms on individual temperatures of the refractory or cooling water. The need to set alarm limits which are not exceeded across the range of normal operating conditions leads to a system that only provides a limited warning, if any, before a failure occurs. Integrity monitoring systems that look at many different signals and alarm only changes in the relationships between the signals have been implemented on the smelting and converting furnaces. The systems are based on principle components analysis (PCA) models and implemented with the monitorMV software package. These provide much more sensitive and selective alarms so that changes in integrity are alarmed well in advance of any event. At a critical alarm level, the converting furnace is set to automatically shut down so that operating and technical personnel can review the situation. The configuration of the systems and operating experience with them will be discussed.

Jan 1, 2007

By I. Spector, A. J. Smith

In 1967, BACM Industries Limited started producing walboard at Saskatchewan's first gypsum products plant, located in Saskatoon, using, as a basic raw material, gyp-sum rock supplied from the company's mine near Amaranth, Manitoba. This paper describes the geology of the Amaranth gypsum deposit, the method of mining the rock and the manufacturing facilities used to produce wall-board.

Jan 1, 1970

By S. A. Willis

For the past several months 1 have been considering the functions of this Society and its reasons for continuance. The fact that it is now sixty years old indicates that it must have been of value and we all know that it has contributed much that was worthwhile to Nova Scotia and the Maritime Provinces. The question arises: "What is the future of the Society, and how might its activities be altered to suit present-day activities and to be of even greater value?" Let us analyse the various activities in which we are interested and determine which, if any, are of more value than others. First of all, at least once a year we have a two-day convention which constitutes a holiday for the members and their wives. This has always been well planned and has been much enjoyed. Second, there are many social and business contacts made during the meetings and interim meetings. These certainly tend toward better relations and co-operation between the various people concerned. Mine operators meet other mine operators, engineers, people from the education fields, Department of Mines, and so forth. Various sales contacts are made at these meetings which can be of value and use to both the Company selling and the customer. Third, and of greatest importance in any conference, is the exchange of ideas by the members and by authorities from outside, and the presentation of slides and drawings, or actual visits to operations. It is upon this phase that 1 wish to elaborate. These papers are not only presented to our meetings but are generally published in the C.I.M. Bulletin so that members throughout the Dominion have access to them. Many important papers describing new phases of operations have originated through our Society.

Jan 1, 1947

By J. A. Finch

Samples of feed and product from a closed grinding circuit treating a heterogeneous lead-zinc ore were taken. The feed was subjected to laboratory batch grinding in a rod and ball mill with the objective of simulating the closed-circuit size distribution. It was concluded that the batch rod mill can closely simulate this product if only the over-all size is considered, but mineral-by-mineral large differences occur. If, as is suspected, the mineral sizes are the important factor in flotation, the differences could lead to problems in interpreting flotation results. An example of mineral recovery as a function of size is described to illustrate the potential problems.

Jan 1, 1979

The use of roof bolting gave promise of substantial economic benefits to Continuous Miner operations at Michel Colliery. As the first step in the adoption of bolting, 142 anchorage tests, employing six types of anchor shells, were made in three mines. Significant differences were found in the anchorage capabilities of the various shells and the various roof rocks. Introduction S PORADIC attempts at roof bolting had been made at Michel Colliery over a period of ten years. Results were indifferent or inconclusive. A concerted effort was not made, because a compelling need for bolting did not exist. By 1962, however, the advent of Continuous Miners had brought a new significance to roof bolting and, at the same time, the increasing price and scarcity of mine timber made bolting materials more competitive in cost. A fresh appraisal of bolting, therefore, became justified and necessary. The potential benefits of roof bolting at Michel are several.

Jan 1, 1963

By W. E. Cockfield

"The Stump Lake mining camp is in Nicola mining division of southern British Columbia. It lies about halfway between the cities of Kamloops and Merritt.The deposits at Stump Lake are among the earliest lode discoveries of British Columbia, many of the claims having been staked between 1882 and 1885. A considerable amount of work was done prior to 189Cl, after which very little was done until 1916. Since that time mining has been carried on at intervals, much of it on the same deposits, by a number of companies, including the Donahue Mines Corporation, the Planet Mines and Reduction Company, the Nicola Mines and Metals Company, the Consolidated Nicola Goldfields, Limited, and others. According to the British Columbia Department of Mines, total production from the area has been: gold, 8,520 oz.; silver, 259,413 oz.; copper, 40,822 lb.; lead, 2,208,859 lb.; and zinc, 367,869 lb. Most of the production has come from the Enterprise vein and a branch of the Enterprrsethe King William vein."

Jan 1, 1954

By Robert T. McKnight

"Traditional techniques for valuing resource projects companies have been primarily based on discounted cashflow methods (DCF) or by comparison to similar projects with an apparent market capitalization. Many resource projects are really forms of options to invest rather than a future cashflow stream. Employing the DCF method to value a resource project which is really an option to invest, can dramatically underestimate the real value of the project. The analytical tools required to evaluate options, while more complicated than the usual spreadsheets used for DCF, are becoming more easily available and usable by managers. This paper will discuss the background of options valuation and some of the tools which will make it easier for managers to estimate the value of projects and companies which have significant real option values.ResumeBob McKnight is a graduate of the University of British Columbia in Geological Engineering, supplemented by an MBA from Simon Fraser University. Following several years in the oil patch with Cities Service and Brascan, Bob returned to Vancouver in 1979 to work for Wright Engineers. He subsequently went on to work for Cassiar Mining, Getty Resources and Endeavour Financial before joining Pincock Allen & Holt Ltd. in 1998. His experience ranges from exploration to feasibility studies, financial evaluations of mining and oil & gas projects, due diligence, project finance, valuations and mergers and acquisitions. He has extensive international mining experience pertaining to such countries as Chile, Mexico, Uruguay, Thailand, Indonesia, Angola, Papua New Guinea, Kazakhstan.What are Options?Options have been around for centuries. They were familiar to Roman and Phoenician traders who were shipping cargoes from Mediterranean seaports. In the financial world, options are types of contracts that generally include the right, but not the obligation, to buy or sell a share, currency or commodity. The underlying commodity price or share price changes are assumed to be lognormally distributed. In this context, options are of two general types, ""call"" options and ""put"" options. Call options have the characteristic of having the right to buy a tradable commodity or currency at a predetermined price for a specified period of time. For the owner of call options, they become more valuable as the price of the underlying commodity increases. For the seller of call options, these options become an increasing liability as commodity prices rise, since there is the obligation to sell the commodity at a predetermined (perhaps lower-than-market) price. This characteristic of call options recently became high profile with the sharp rise in gold prices last year. The value of gold call options sold by certain producers increased their associated liabilities to the point where margin calls were made."

Jan 1, 2003

By Jan Drzymala, Przemyslaw B. Kowalczuk

"Flotation is possible when the forces operating between a bubble and the attached particle are properly balanced. There are many forces operating in the bubble-particle aggregate. The magnitude, location and direction of the forces depend on the type of process. The simplest arrangement in flotation is when a spherical bubble is attached to a spherical particle and both are immersed in water. In such a system there are four essential forces which shape the stability of the bubble-particle aggregate. They are excess pressure and interfacial solid/liquid, solid/gas and liquid/gas forces. A proper analysis and balance of the size, location and direction of these four principal forces lead to a general equation delineating the stability of the spherical particle–attached bubble system. Specific cross sections of the system and solution of the general equation lead to different relationships including the Young formula as well as the well-known geometrical relation between contact angle, particle and bubble radiuses. The arrangement of forces in the proposed graphical representation of the Young law is different from that presently used in literature for a bubble attached to an unmovable solid particle. Many real solid/liquid/gas systems are more complex due to the presence of additional forces which change the regular curvature of the liquid/gas interface leading to advancing and receding contact angles.INTRODUCTIONThere are numerous papers (Athukorallage, Aulisa, Iyer & Zhang, 2015; Chau, Bruckard, Koh & Nguyen, 2009; Drzymala, 1994; Lubarda, 2012; Pellicer, Manzanares & Mafe, 1995; Wang, Cui, Zhou, Xu, Sun, & Zhu, 2014; Young, 1804) and books (Davies & Rideal, 1963; Defay & Prigogine, 1966; Lee, 2013; Lyklema, 2000) dealing with the solid/liquid/gas system. Many of them concern the three involved phases having the shape of a sphere or spherical cap and the formed contact angle. The contact angle is usually measured through the liquid phase and can be either smaller or greater than 90o. The essential part of these publications is a graphical representation of the system with the Young equation shown as a result of balance of only three forces that is the excess Gibbs (or Helmholz) free energy per unit area of the three involved interfaces (Davies & Rideal, 1963; Defay & Prigogine, 1966; Israelachvili, 1985) (Figs. 1a-c). The Young equation, when the gravity force/buoyancy is neglected, is:"

Jan 1, 2016

By Q. Li, X. -L. Lei

Accompanying global energy shortage and high energy prices, shale gas has been the focus of exploration and it has attracted great attention from both academia and industry. The combination of horizontal drilling and hydraulic fracturing enables the extraction of huge quantities of shale gas from impermeable shale formations. During the process of hydraulic fracturing, great amounts of water, sand and chemicals must be injected into the shale formation at a high pressure, which may trigger seismicity. Such events could occur due to the presence of faults or the reactivation of these potential faults. Shale is the main component of source rock in the Sichuan Basin, China, and has the greatest contribution to the natural gas of the basin. In order to investigate the fracturing mechanism of shale in the Sichuan Basin, China, a series of rock fracture tests under triaxial compression were carried out in the laboratory in order to investigate the hydraulic fracturing behavior in relation to the seismicity. Based on the high multichannel waveform recording system, the detailed spatio-temporal distribution of acoustic emission due to micro-cracking was used to examine the deformation and fracture behavior of shale. In addition, the effects of confining pressure on the deformation and fracture in shale under triaxial compression by acoustic emission monitoring and X-ray computed tomography were discussed in the paper. The experimental results indicate that the shale samples demonstrate brittle fracture behavior. The confining pressure has a great effect on the complexity of the fracture planes and the spatial distribution of acoustic emissions, but few contributions to the location of the major hydraulic fracturing plane. The foliation of shale plays a dominant role in the rupture process and the geometry of the major hydraulic fracturing plane. The high confining pressure increases the strength and restrains the deformation of shale during compression process. These results shed some light on the understanding of onset of hydraulic fracture initiation not only for shale gas exploration and production, but also for CO2 geological storage and underground energy storage.

Jan 1, 2015

By M. Fujikawa

The Kamioka Zinc Smelter was converted from the jarosite process to the goethite process in the year 2000. The reasons for the conversion of the process were that the silica content of the raw material increased and the iron content decreased. The silica easily turns to a gel in sulfuric acid solutions and this causes the solid-liquid separation characteristics to deteriorate. The basic behavior of silica in sulfuric acid solution was investigated and it was found that the goethite process is the most suitable to effectively separate and remove silica from solution. Furthermore, Fe has the capability to remove elements such as Ge that have an adverse effect on zinc electrolysis. This means that, when the Fe content of the raw material decreased, the impurity removal capability also decreased and there was a risk of a build-up of impurities in the process. Iron precipitates in many forms in sulfuric acid solutions. The capability to remove elements such as Ge differs depending on the compound precipitated. Goethite has a higher capability than jarosite to remove elements such as Ge. In this report, the results of applying the process established by investigations of the basic behavior of Fe, silica and Ge in the zinc refining plant are presented.

Jan 1, 2006

By H. W. McGerrigle

The St. Lawrence Valley of Quebec lies in an earthquake danger zone, the main centers of which appear to be Murray Bay, Montreal and Quebec City. This paper compares conditions in this "earthquake zone" with those of other, currently more active, earthquake zones of the Earth, deals briefly with the mechanics of earth movements and outlines the means by which earthquakes are re-corded. An account is then given of the earthquakes which have occurred in the Province of Quebec -from that of 1534-35 to the earthquake of 1925. A 50-year frequency cycle is implied. The general conclusion is that the 11robability of future earthquakes should be given more consideration in the construction of buildings in the St. Lawrence Valley region.

Jan 1, 1966

By W. F. James

Introduction The season of 1927, from the point of view of mining development in the area west of Rouyn, was quite satisfactory. Serious prospecting and development' were undertaken over quite a large area, though the results in the matter of discovering new deposits of economic importance were rather disappointing. A large amount of systematic prospecting and geological mapping was carried out in the course of the work, and a considerable body of information collected. A widespread occurrence of sulphide mineralization was noted, chiefly near bodies of older gabbro. The frequent occurrence of pyrrhotite in or near which local concentrations of chalcopyrite were localized, lends support to the idea that such older sulphides as pyrite and pyrrhotite are relatively easy of replacement by chalcopyrite. From the prospector's viewpoint, areas near the contacts of masses of older gabbro are favourable prospecting ground, and pyrite and pyrrhotite mineralization are favourable indications that massive chalcopyrite may be found where it has completely replaced such sulphides. Pyrrhotite being magnetic is easily located, even where drift covered, by the use of such convenient instruments as the dip-needle and the magnetometer. It is suggested that pyrrhotite bodies, when located, be thoroughly prospected because of the fairly strong probability that they may show replacement by the more valuable chalcopyrite.

Jan 1, 1928

By Fidelis T. Suorineni

The conditions for rockburst occurrence are traditionally identified as: high stress, high extraction ratio, strong brittle rocks, folding, faulting, and unfavourable excavation geometry. Based on a critical review of case histories, this paper identifies oblique loading of orebodies by the major far field principal stress as a cause of rockbursts. Orebodies subjected to this loading condition are termed orebodies in shear. Orebodies in shear are subjected to compressive and shear loads. The case histories presented unambiguously show that the magnitudes of the far field principal stress alone, and a knowledge of the conventional rockburst causing factors are not sufficient for mine planning and design. The orientation of the major far field principal stress, or for that matter the driving stress relative to the orebody axis, should be recognised as one of the causes of rockbursts. It is suggested that since stress orientation is an important factor, and orientations from stress measurements are so variable, orientations from stress measurement data be complemented with underground observations from borehole and excavation breakouts to determine the actual in situ stress orientation, whenever possible. Also stress modelling for the design of critical elements (pillars) should include a sensitivity analysis on the relative critical field stress direction. The paper emphasises that special attention should be paid to or

Jun 1, 2012

By D. Kalumba, S. Jjuuko

"Thin Spray-on Liners resist relative small deformations (< 1 mm) between rock blocks or fragments in terms of a combination of shear, adhesive and tensile-bond strengths. Shear-bond strength addresses the ability of a thin liner to resist stresses that act parallel to the rock-liner interface. Therefore quantification of shear-bond strength is essential in the formulation of design standards and requirements for Thin Spray-on Liners. In this paper Thin Spray-on Liner support mechanisms are reviewed. In addition previous methods of Thin Spray-on Liner shear-bond testing are discussed. The paper also explains the research being carried out at the University of Cape Town to investigate the effect of different parameters on the shear-bond strength.INTRODUCTIONRock surface support is widely used to combat rockfalls and resulting injuries and fatalities in the vicinity of active faces (Potvin, 2002), where workers spend most of their time (Adams & Baker, 2002; Potvin, 2002; Lacerda, 2004). The conventional (traditional) surface support systems in underground rock support include passive methods such as mesh and lacing and active methods such as shotcrete. However, rockfall sources between 1990 and 2000 in Nevada gold mines showed a steady increase in rockfall injury associated with mesh support as shown in Figure 1 (Lacerda, 2004). The conventional methods also negatively impact the mining operations with regards to costs, logistics and mining cycle times due to large material volumes (Tannant, 2001; Ozturk & Tannant, 2010; Ferreira, 2012). Therefore, these systems need to be substituted, with enhanced methods, in order to realize the business target of the mining industry of providing the planned return on investment made without harm and within budget."

Jan 1, 2015

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 B. Krysa, A. Mitsui, T. L. Koehler

The presence of arsenic, even at trace levels, in copper processing leads to the risk of arsine gas where reducing conditions exist that can reduce any soluble arsenic present to its minus 3 valance state and generate hydrogen gas from the solutions. This risk is understood to be significant within the industry, particularly in the case of liberator cells where copper concentrations in solution are drawn down to remove the copper and impurities from the bleed stream. However, there are numerous other potential areas where the arsine gas risk exists including contact between active metal such as iron, zinc or aluminum and arsenic bearing solutions in pyrometallurgical dust treatment, refining and acid plant operations. In turn this breaks down to different mitigating strategies dependent on the risk scenarios considered; for example, how this risk interacts with Change Management, Confined Space Entry or Contractor Training. The ISO 45001 is an emerging standard meant to improve employee safety, reduce workplace risks and create safer working conditions all over the world. The paper shows a case study of how a framework consistent with the tenets of ISO 45001 has been used to provide a consistent assessment of this risk for a wide variety of copper operations and the expectations of how this may be used to effectively improve the effectiveness of barriers against future incidents. INTRODUCTION Arsine gas (AsH3), first identified in 1775, is a highly poisonous, colorless, non-irritating gas with a mild garlic odor that is heavier than air. Arsine gas is generated when reducing conditions are generated in the presence of hydrogen ions and arsenic compounds. Present permissible occupational exposure limit as defined by Occupational Safety and Health Administration (OSHA) as an 8-hour time-weighted average is ppm (0.2 mg/m3). Further increasing the risk, conventional respiratory protection utilizing half or full masks with gas filtering cartridges provide minimal protection against arsine. In copper processing plants, the risk of arsine generation is well understood in liberator cells, which are part of the electrolysis process. In this process, solutions containing copper are reduced in copper concentration removing not only the copper, but also arsenic, antimony and bismuth. The residual solution can be bled to control impurity build-up in the refinery. In this process, if the copper concentration is reduced to the point where As3- can form, arsine gas is generated via reaction with hydrogen ions generated during the plating process. The copper concentration at which arsine gas is generated depends on copper concentration at the cathode surface, the temperature and the acidity. As a result, there is always a risk of arsine gas generation in the liberator cell. Process measures to minimize or mitigate arsine evolution are tight control on final copper concentration, warm temperatures, fresh feed distribution and internal acid recirculation rates. Operator exposure protection measures are hooding, ventilation, arsine detection systems, restricted personnel access, automated shutdown controls and pre-defined evacuation plans.

Jan 1, 2019

By Kremena Dedelyanova

The paper presents research of mechanism for the creation of air bubbles in vibratory a column flotation machine. Factors are discussed that influence the increase in the duration of the bubble in the area of contact with the mineral particles. Formulas are derived for the parameter effect of vibrations, applicable to the design of flotation machine. The collision efficiency of the bubbles in a vibratory column flotation machine is determined.

Aug 1, 2013