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By A-A. Bogno, Ch. -A. Gandin, A. Maitre, H. Henein

Most metallic materials are produced from their liquid state. In order to control the properties of industrial products, it is very important to understand their solidification path and the resulting microstructures which can be significantly affected by melt undercooling. High undercooling results in rapid solidification and a refined microstructure with minimal microsegregation. This paper reports on the analysis of rapidly solidified Al-Cu droplets obtained by a single fluid atomization process, Impulse Atomization. A quantitative analysis by Rietveld refinement method of the Neutrons Diffraction data was carried out to determine the fraction of the intermetallic Al2Cu. Knowing the fraction of Al2Cu, the eutectic fractions and corresponding dendritic and eutectic undercoolings were estimated using the metastable extensions of solidus and liquidus lines of the Al-Cu system calculated by Thermo-Calc. In addition to this work, a model of microsegregation coupled with ThermoCalc software via TQ (application programming interface of ThermoCalc) and the Wang-Beckerman model for dendritic growth velocities has been developed for binary alloys. This has led to the development of a phenomenological relationship between primary phase undercooling and initial growth velocity. A comparison of estimated primary undercoolings using a coarsening model with the adiabatic undercoolings for each alloy composition has confirmed that solidification occurs under adiabatic conditions during recalescence.

Jan 1, 2014

By Norman O. Lotter, Virginia Lawson, Mika Muinonen, Dominic Fragomeni, Jorge F. Oliveira

Development of metallurgical flowsheets from drill core to production of finished metal involves two main domains: process mineralogy to sample the ore and develop a successful flowsheet producing saleable concentrate; and extractive metallurgy to convert that saleable concentrate to finished metal. Effective flowsheet development for a new or brown-field concentrator and processing facility is essential to project schedule and return on investment. Over the last decade in particular, the integration of geology, mineralogy, sampling, and mineral processing have empowered the development of an improved practice in flowsheet development. The use of geometallurgical units as a basis for best-practice sampling delivers representative study material to the laboratory. Modern automated mineralogy characterises the whole rock assembly and paymetal mineral hosting, to address downstream process implications. Batch scale flotation testing then uses this information to design and perform well-focused strategies. At early stages of the project, the Extractive Metallurgy team is engaged to determine processing constraints or other economic drivers in conversion of the saleable concentrate into finished metal. The team evaluates available technologies, assesses the impurities and key properties of the given concentrate. In many cases, changes to mineral processing flowsheet are required to maximize value per tonne of concentrate. Site conditions, availability of infrastructure, energy and power all play an important role. Modern metallurgical simulation tools such as FactSage™ and METSIM™ can quickly define the appropriate test program for each process. Bench scale testing and appropriate scale of piloting can confirm simulations and provide design criteria. A case study demonstrates how effective use of these tools and a multidisciplinary team can accelerate flowsheet development, while reducing costs and ensuring that the designed processing facilities maximize project value with minimum risk.

Jan 1, 2014

By S. Mostaghel, S. Nicol, M. Y. Solar

Once upon a time, the process engineer developing the design criteria for a new saprolite ferronickel smelter had it easy: most ores were around 2.5% Ni, with a Fe/Ni ratio of 4 to 5 and a SiO2/MgO ratio of about 1.6; to use the French word: garnierites. The ferronickel grade selected was the conventional 20 to 25% Ni and the impurity levels could be predicted from well established [C], [Cr] and [Si] vs (FeO) graphs. However the process engineer can no longer depend on statistics to design smelters: Ni grades are decreasing while the goethite contents are increasing; SiO2/MgO ratios vary from 1 to 3; and Al2O3 concentrations are reaching levels that cannot be ignored. Mechanistic models must be developed to select or predict essential parameters such as kiln and furnace reductions, ferronickel grade, slag losses, metal and slag liquidus, operating temperatures, etc. But these models must be simplified so that they can be used on a routine basis; and they must be calibrated against a wide range of commercial operations in order to yield the most realistic predictions possible. The present paper proposes one possible approach, using FactSage as a basic source of thermodynamic data. The predictions thus obtained are compared to actual performance for two well documented operations, as well as to the predictions made with other tools that might be more accessible.

Jan 1, 2014

By M. Y. Solar, W. G. Davenport

Most of the recent growth in nickel demand has been for the production of stainless steels and virtually all of it has been satisfied by new ferronickel and nickel pig iron projects. But "good" laterite resources are more and more difficult to find: Ni grades are decreasing while Fe contents are increasing and SiO2/MgO ratios vary from 1 to 3 and even higher if limonites are included. Predicting the smelting behaviour of such ores requires a more fundamental understanding of the thermodynamics of these systems in commercial operations. One valid question is thus whether these furnaces are at thermodynamic equilibrium or not. The present paper investigates this question, compares calculated and measured O2 partial pressures and mechanical/chemical slag loss ratios and concludes that ferronickel furnaces are not at thermodynamic equilibrium. This departure from expectation is actually to the operators’ advantage: the targeted ferronickel grades can be obtained at lower reduction potentials than calculated from pure thermodynamics.

Jan 1, 2014

By N. Behnood

"This paper describes how material selection, quality assurance, and failure investigation play important roles in the efficiency and safety of mining and metallurgical operations.INTRODUCTION Material selection, quality assurance, and failure investigation are all complementary elements of materials engineering in the application of materials technology for failure prevention. Based on commodity price increase of 300% between 2002 to 2013 [1] and increased cost ofcapital projects and operation, equipment failure, which in some cases causes complete shutdown of the operation, becomes a vital importance in mining and metallurgical plants. The following sections present a number of examples from many failure cases experienced by the author during his three decades of work as a materials engineer in the mining industry."

Jan 1, 2015

By H. Zhu, Y. Sato, O. Takeda, K. Nakano

Recycling of rare earth magnet wastes is essential to insure the stable supply of rare earth resources. For the development of a novel recycling process, the removal of rare earth oxide from an off-spec alloy magnet was investigated by melting the alloy magnet at 1503 K together with fluoride flux, LiF-50 mol% NdF3 and LiF-?25 mol% NdF3-25 mol% DyF3. After melting, the separation of magnet alloy from the fluoride flux was achieved, and neither suspension of alloy in the flux nor suspension of flux in the alloy was observed. Oxygen concentration in the alloy decreased from 5000 mass-ppm to 160 mass-ppm by utilizing 1.5 times of equivalent amount of flux needed to completely dissolve the oxide. The investigated process is suitable for mildly contaminated waste such as a used (end-of-life) magnet because of its simplicity, low energy consumption and small limitation on location for operation.

Jan 1, 2014

By Benjamin H. Clark

"For over 50 years, Derrick Corporation has been renowned for its innovative and durable fine screening equipment and screen surface technology. Derrick’s latest innovation, the patented Stack Sizer, offers mineral processors both high tonnage capacity and high separation efficiency on an extremely small footprint.The Stack Sizer is suitable for separations from 6.3 mm down to 75 microns (200 mesh). The Stack Sizer, coupled with Derrick’s patented urethane screen surface technology, offers an extremely economical alternative to hydraulic classifiers, hydrocyclones, and less efficient low volume wet screening systems. Stack Sizers have been used in feed preparation for flotation, spirals, and a variety of jigs. Mineral processors wishing to reduce grinding circuit circulating loads and generation of slimes due to over grinding, thereby enhancing the efficiency of flotation and gravity circuits, now have another technology at their disposal to perform this critical sizing and grade control function.Over 200 Stack Sizers have been installed in numerous mineral processing applications worldwide attesting to the rapid acceptance of this technology. Stack Sizers are currently screening ferrous and non-ferrous metal ores, mineral sands, silica sand, kaolin clay, feldspar, garnet, phosphate, aluminum dross, potash, coal, tantalum, spodumene, niobium, and other rare earth mineral ores.INTRODUCTIONDerrick engineers have long understood and demonstrated the importance of screen width in coupling both high capacity and high separation efficiency for fine wet sizing applications. As opposed to fine dry sizing, where the length of the screening machine is critical for high separation efficiency, introducing slurry feed to screens in a thin and even layer at minimal velocities across wider screen surfaces allows for high capacities and efficiencies, with maximum screen cloth life. This is due primarily to the combination of free liquid and high frequency vibration of the Derrick motors, which allow fine undersize material to pass through the screen apertures. Lacking either of these factors would be extremely detrimental to the screening process. Without the high frequency vibration of the motor, the screen is essentially a low efficiency sieve bend. Without the free liquid to carry fines through the screen openings, the screen is for all intents and purposes a glorified conveyor or dewatering unit, as little or no sizing takes place once the screen is devoid of free liquid. For optimal screening results, Derrick recommends feeding slurry to a screen at approximately 20% solids by volume. Figure 1 shows the Stack Sizer design concept. Note that a single feed point is used to evenly distribute the flow to the five separate feed points."

Jan 1, 2007

By G. Azimi, K. K. Varanasi1, A. T. Paxson, R. Dhiman, H. -M. Kwon

Hydrophobic materials that are robust to harsh environments are needed in a broad range of applications. Although durable materials such as metals and ceramics, which are generally hydrophilic, can be rendered hydrophobic by polymeric modifiers, these materials deteriorate in harsh environments. Here it is shown that a class of ceramics comprising the entire lanthanide oxide series, ranging from ceria to lutecia, is intrinsically hydrophobic. Their hydrophobicity is attributed to their unique electronic structure, which inhibits hydrogen bonding with interfacial water molecules. In addition, this work demonstrates that these ceramics sustain hydrophobicity even after exposure to high-temperature environment (1000 °C for 2 h in air). It is envisioned that this class of robust hydrophobic materials will have far-reaching technological potential in various industrial applications, where water repellency and dropwise condensation are desirable.

Jan 1, 2014

By Stefan Wallner, Andreas Filzwieser, Stefan Konetschnik, Reinhard Preiss, Iris Filzwieser

"Process Safety Management for METTOP means avoiding risks as far as possible - but also dealing with the residual risk by using all existing management tools or external assistance, if required. The presented paper has two parts. The first one introduces a new and very safe cooling technology for metallurgical furnaces. The second part shows how to deal with the residual risk as well as minimize it by using the tapping area of an electric arc furnace as an example.Today more and more intense furnace operations require effective cooling in order to achieve low refractory wear and good furnace lifetime, making cooling technology an important aspect of furnace operation. However, the use of water - today’s standard cooling medium - has some disadvantages, as it can cause problems both during furnace start up and operation, namely hydration problems, corrosion, and explosion.To overcome the disadvantages of water, a new cooling technology using an alternative cooling medium, namely ISIS B (a special kind of ionic liquid) was developed. The main advantage of ISIS B is the fact that no explosion occurs when this liquid comes in contact with molten metal. The working temperature range of ISIS B of 50 to 200 °C results in other advantages as there are no corrosion problems and no risks of hydration.The fact that no explosion occurs when ISIS B contacts molten metal leads to a revolutionary solution for the metallurgical industry in terms of safety. Especially in critical areas - like tap-holes - new safety standards can be achieved.Together with the TÜV Austrian Holding AG a risk analysis was done for a water cooled tap-hole as well as for a tap-hole cooled with ionic liquids. It is shown that using the new technology the risk can be decreased dramatically and the importance of a best available technology is described."

Jan 1, 2014

"The mining industry uses many types of mineral and metallurgical plants to produce saleable product from ore mined. Plant design history has left current operations with a mixture of manual operation and various forms of automated process controls. Consequently, we typically see high variability in the continuous operations together with a shortfall in the attainment of full capacity, or higher utilisation of consumables.At a level of best practice, ‘Operational Performance Excellence’ focuses on process control, using automation and control systems to deliver process optimisation. This more sophisticated delivery is a great deal more difficult than the first stage of equipment selection / installation. It includes the appropriate selection of the right instrumentation, control system, key process knowledge, individuals with a solid control engineering background / experience, and the essential backing / support of the operations management team together leading to higher value delivery. Robust solutions can be realised, considerably minimising process variation, thus leading to process optimisation. This approach results in an easier, efficient and safer process while providing considerable returns for the plant owners.How variable are your processes, and do you maintain optimised process performance with dedicated resources, modern instrumentation, ‘best practice’ control systems and performance monitoring tools? In this paper, these questions and their possible answers are discussed."

Jan 1, 2014

By Marius Jacobs

"Safety performance in many companies and even industries has stalled in the few years. Accidents rates are at a "plateau" and yet, serious accidents and fatality rates are not. In more dramatic cases, such as in the BP Texas disaster, organizations that have "exemplary" safety statistics, suddenly have a catastrophic or multi-fatality event occurring. Other classic examples are the Piper Alpha disaster and NASA’s Challenger and Columbia disasters and even the Chernobyl nuclear reactor. Looking into the root causes of these accidents provides an insight into the events and deficiencies that led up to the accident, but what are the common features in the organization’s mindset? What characterizes these organizations’ decision-making, their approach to safety and to risk and are there specific cultural features that can be delineated? The research and review presented in this paper covers a period since 1994, which started in the Australian resource industry and since then covered international events. The features of these organizations are summarized as the seven deadly delusions, based on extensiveresearch since 1997 of organizations that suffered unexpected disasters.The Piper Alpha Oil Rig disaster in the North Sea, on the 6 July 1988, was one of the most pivotal events in safety around the world. It changed the thinking and focus of governments, whole industries and led to numerous books and papers. It resulted in new legislation, textbooks and a critical self-examination by the oil and gas industry.In short, an explosion and fire occurred when a pipe started leaking gas and ignited. A temporary flange, with no safety valve, was used to block off this pipe during a maintenance operation the previous shift. The permit to advise operators not to start the pumps on this line was misplaced and lost. Several deficiencies, problems and system failures coincided. A key factor was that the water deluge system was inoperable at the time and failed to extinguish the large fire that erupted, followed by an even larger gas explosion. The accommodation unit, situated on top of the oil rig, was the main "killing field" - most men gathered here to await instructions (which never came) and where they died from smoke inhalation. Later, a large explosion of the gas pipeline from an adjoined rig exploded and killed more people.The line of events and the associated system failures are all very relevant in the analysis of the accident, and provide the only insight into what caused the accident. But much "further back", inside the organization’s culture, lurks more dark matter. The first inclination is to ask what was "deficient" in the culture. Did they not care enough about safety, or about their people? Did they have a culture where production decisions were more important than safety considerations? Did they ‘coerce’ supervisors and employees to ignore safety precautions or did they just "fly by the seat of their pants"?Not surprisingly, it is very difficult to identify the true nature of the culture in that business because in such an aftermath of death and destruction, no one dare say that the safety culture was a ‘positive one, focused and caring’ or that the company was doing well in safety and that this is only a freak accident. Indeed, there were many deficiencies in the organization’s systems and procedures, such as the permit to work system.But there are some niggling questions: How is then that the Piper Alpha Oil Rig was actually considered the company’s most productive and safest oil rig in the North Sea? Why would this rig win a safety competition, 6 months before the disaster, with the deficient permit as its most outstanding successful system?"

Jan 1, 2014

By C. Kennedy, S. Jensen

Traditionally, mineral processing plants are designed to achieve the highest recovery of valuable material with limited regard for the cost of managing waste products-both solid and water components. As an industry, we are confronting ever more stringent environmental standards and lower grade deposits requiring more intensive processing. The most profitable processing route can, in fact, lead to costly issues downstream. Issues or risks associated with waste management include water treatment and handling and storage of potentially acid generating material. The capital and operating costs of dealing with these issues are significant and should be considered as a consequence of plant design and optimisation. The authors of this paper are involved with a number of projects where process operation changes offer opportunities to mitigate risks associated with water and waste management. Examples of these changes will be discussed along with the estimated benefits to the value of the project and reduction of long-term environmental risks. Process changes include 1) the application of in-plant water treatment as opposed to dealing with the entire tailings management facility and 2) the potential to reduce metal leaching and acid rock drainage through the preferential liberation of carbonate minerals in the grinding process.

Jan 1, 2014

By R. B. Barlow, J. A. C. Fortescue

Originally developed for use in mineral exploration, regional geochemical mapping based on stream (and lake) sediment sampling is showing broader application in other areas of the earth sciences and in environmental science. The purpose of this paper is to focus attention on the role of regional geochemical mapping in relation to geological and environmental studies. This is achieved using a descriptive equation for the chemical composition of a stream-sediment sample and then relating it to the use of successive approximations in geochemical and environmental investigations. The procedure is further qualified with reference to time and process in the formation of regional geochemical patterns. Examples are included of studies based on stream sediments related to bedrock geology, surficial geology, ecology and man's effect on the geochemistry of the environment. The range of applications of regional geochemical mapping in earth and environmental studies is outlined and some conclusions drawn regarding the future development of geochemical mapping under Canadian conditions.

Jan 1, 1980

By Y. Bai, J. J. Liu, D. Q. Li, S. Z. Liu, X. T. Wang

"This paper presents the results of an industrial test using 8 t/d of Baotou concentrate (50% REO) of a clean metallurgical process, which includes: 1. Roasting with H2SO4 at low temperature (220~260 0C) in a batch roasting furnace followed by water leaching to obtain a leach liquor as feed with a yield of >95% RE and Th, recovering F as fluoride, producing a leach residue amounting to 1/3 of an equivalent high temperature residue and containing <0.03% Th and radioactivity < 3×104 Bq/kg compared to the normal high temperature residue containing 0.2-0.3% Th and 1×105 Bq/kg. 2. Separating Th with N1923 and extracting RE by P507 has been completed in mixer-settlers. Test results indicate that the ThO2 product has a purity of > 95% with a yield of 99%, and the RE has a yield of >95%, in which ThO2/REO <5×10-6, and that P507 loaded RE connect straight with separating RE using P507-HCl system. 3. Treatment and multipurpose use of "three wastes" (water, gas and solids) are discussed in some detail."

Jan 1, 2014

By Brian Hart, Roger St. C. Smart, James Francis, Mark Biesinger

"There are a number of challenges involved with the surface analyses of different mineral phases from process streams in a flotation facility. The first of course is to collect samples that are representative of the process and to ensure that they remain in a pristine condition prior to introduction into the instrument. In mineral processing, sample collection from the different streams is done on site and preservation involves simply removing oxygen from the sample by bubbling nitrogen or argon gas through the sample and snap freezing with dry ice.The second challenge in studying the surface chemistry of specific minerals is to find reliable methods of mineral phase recognition. In surface analysis of mineral particles confident mineral selection can be difficult with many multi-metal minerals (e.g. chalcopyrite, pyrite, sphalerite) and with precipitated, adsorbed, reacted and contaminant species in the outermost molecular layers.In this paper we show that principal components analysis (PCA) of ToF-SIMS data provides improvement in phase recognition, particle selection and associated variations in surface species. We will demonstrate, with specific examples, that this technique can be utilized to differentiate surface chemical factors promoting (hydrophobic species) or inhibiting (hydrophilic species) flotation.Species recognition based on the PCA method in a study of Cu transfer between chalcopyrite, pyrite and sphalerite mineral mixture clearly identified a statistical difference in copper intensities between the sphalerite and pyrite phases. A similar ToF-SIMS/PCA based study applied to concentrate and tails samples collected from the Inco Matte Concentrator demonstrated extensive CuOH and NiOH transfer between the chalcocite and heazlewoodite minerals. The statistical analysis has been able to confirm some mechanisms and deny others proposed to control recovery and selectivity giving more focus on the control factors.The ToF-SIMS PCA statistical analysis has elucidated differences in surface chemistries which illustrate the discriminating depressant action of adherent aluminosilicate (gangue) fine particles and adsorbed ions on the surface of sphalerite grains. In the flotation test concentrates, HIC conditioning resulted in the removal of these gangue fines thereby improving surface collector attachment efficiency, promoting a greater recovery of sphalerite."

Jan 1, 2007

By K. C. Viveros, R. R. Ambriz, C. García, F. De Villèle, A. Talha, D. Jaramillo

Cold hole expansion on base metal, weld metal and heat affected zone of 6061-T6 aluminum alloy welds was simulated by means of finite element method. Three dimensional compact test models with a previous fatigue crack length with a relation of ??= a/W = 0.3, were used to analyze the hole expansion process. Considering the local mechanical properties for each zone of the welded joint, the optimal expansion degree (1.64 to 2.46 %) was determined. The residual stress field, through thickness, after the expansion process in all welding zones, were correlated with the crack opening displacement obtained by finite element analysis. It was observed, that compressive residual stress fields for a post-expansion, in different crack lengths, provided a crack closure mechanism for base metal, weld metal and heat affected zone. Contrary, the crack remained open when residual stresses are positive. The results are given as tangential stresses versus distance from the edge of the cold expansion and crack opening displacement as a function of applied load.

Jan 1, 2014

By Robert Keyes, Charle Knowles, Glenn Kendall, Gary Fletcher

"The metal mining industry in Canada has been dramatically affected by the changes that have occurred in the world mineral market place. World economic restructuring in the post ""oil shock"" period of the mid-1970s, greatly increased competition from suppliers in the developing countries, and commodity price and currency pressures have all combined to severely test Canadian competitiveness. In the new mining world, the rate of growth of demand for metals has declined due to product downsizing, materials substitution, and a relatively slower growth of over-all world economic activity.The interplay of market and political factors is complex. Canadian metal mining companies must compete in world markets against low-cost producers in developing nations whose priorities often appear to be centred on maximizing foreign exchange earnings to foster development goals and debt repayment. Many of these countries have high levels of government intervention in their mining industries. The result is a greatly in-creased number of suppliers all vying for a share of a world demand growing at a relatively slower rate than in the past. To be able to compete under these circumstances, Canadian companies have had to undertake &apos;survival mode&apos; measures and look to new ways of doing things. In order to identify the effects that the recent market and economic trends have had on the Canadian metal mining industry, a study was undertaken by Canada Employment and Immigration to assess these changes and their implications for the metal mining workforce.The Canadian Occupational Projection System (COPS)—Sector Study Group with the cooperation of the Mining Association of Canada, undertook a human resource survey to gather current employment and occupation information. This formed an important part of the Canadian Occupational Projection System Metal Mining Sector Study. This article addresses the with survey results, a C.E.I.C. worker mobility study, and trends and issues that are changing the mix of jobs and the way they are being done.Figure 1 shows metal mining employment for the period from 1974 to 1984. It provides a clear picture of the employment swings that the industry has experienced especially during the recession period of 1981 to 1983. From 1981 to 1983, employment dropped by 14 000, from 68 000 to 54 764, and then dropped to its lowest point in 1984 of 52 783. We feel that employment in the medium term will be flat with growth in gold mines being largely offset by continued workforce rationalizing in other sectors.Perhaps the key point is that equivalent levels of output have been achieved in the recent period (1981-1984) with a workforce that is 25% smaller than it was in 1974. This also raises the questions which the COPS/MAC survey and COPS mobility study sought to clarify, namely, what jobs have been cut and where have these people gone? Equally important are the questions of occupational skill level changes, and what types of jobs are declining and which ones are becoming increasingly important, as economic and technological changes have altered the mining work place."

Jan 1, 1987

By A. J. MacRae

Metallurgical furnaces are made up of complex multi-component systems that must function either together or in parallel for safe, and reliable operation. Thermal expansion of single material components experience induced stresses during heating and cooling, which can lead to cracking or failure. Multi component elements and systems can experience significant thermally induced stresses during both steady state and transient temperature conditions. Examples pertaining to temperature effects on refractory, copper cooling blocks, furnace shells, and complete systems will be discussed. The purpose of the paper is to highlight how stresses and strains are developed due to differential thermal expansion.

Jan 1, 2015

By B. Lueger, D. Shen, M. Sedighy, R. Rand, R. Saleh, J. Cheung, M. Rifai, I. Khan, W. Sauri, D. Setianto

The world’s first active power demand stabilization system for a 3-electrode electric arc smelting furnace was commissioned at PT Vale Indonesia in December 2012 on Furnace No. 2 using an SPLC (Smart Predictive Line Controller). The SPLC technology in combination with the Furnace No. 2 rebuild and other upgrades has enabled PT Vale to increase the electrical input to the furnace by up to 20% on a stable and sustainable basis by eliminating peak powers that overload and trip out the electrical equipment, and by reducing power unbalances. The SPLC technology maintains smooth arc power using a continuously variable thyristor controlled series reactor. The SPLC compensates variations in the furnace arc with predictive changes in the circuit reactance at a speed of up to 60 times a second. The system started up quickly and has been shown to be easy to operate and maintain by PT Vale. PT Vale’s Operations Team has been testing the new system at set points of up to 90 MW on the newly re-built Furnace No. 2. Over the last 12 months, the throughput of Line 2 has increased by approximately 10% on an annual average; however, debottlenecking in other design areas of the operation is required in order to achieve 90MW operation on a sustainable basis. This outstanding success results from a combination of the furnace and other upgrades, the SPLC active power stabilization, and the skill of PT Vale in quickly adopting new technologies and maximizing the combined benefits of each technology in their operation.

Jan 1, 2014

By Jim Wickens, Vince Lofftus, Mark Kravetz

"This paper discusses how Bald Mountain Gold Mine (Ely, NV) dramatically reduced mercury production by treating process solutions with a liquid reagent based on organic sulfide chemistry. Cherokee Chemical Co. Inc. (Vernon, CA) markets this reagent as UNR 81 1A.A summary of the bench tests comparing various reagents is given. The ensuing plant trial is discussed and successful mercury removal results are presented. Data is presented to show that early removal of mercury in the process reduces the amount of mercury collected at retort. Data is also presented to show that use of this reagent does not reduce gold recovery. Plant trial treatment costs are discussed. Finally, the potential of this technology to substantially reduce closure costs as compared to traditional mercury removal options is discussed.INTRODUCTIONBald Mountain Mine produces gold. Mercury is a costly by-product of gold production because no revenue is generated from mercury. Traditionally, mercury leaches out with gold and follows the gold throughout the processing circuit until it is eventually condensed and collected at Retort. Minimizing or eliminating mercury production minimizes worker health and safety risks, minimizes environmental liability, and reduces costs. In the long term, minimizing mercury production will make mine closure easier and less costly.Bald Mountain Mine dramatically reduced mercury production by treating process solutions with liquid reagents called UNR 811 and UNR 811A. Several reagents were bench tested before proceeding with a plant trial. The reagent complexes the mercury to form an insoluble organic sulfide precipitate. In independent tests, the precipitate passed acid mobilization tests and is considered stable."

Jan 1, 2001