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By G. J. Arseneau

ABSTRACT Mineral resource statements are reported as tonnage (volume × density) and grades. Effort is expended to accurately estimate the volume and grade, but accurately determining bulk density is often overlooked. Oversimplification of density modelling can result in potentially serious errors in tonnage estimates and over- or underestimation of metal content. A reliable bulk density model requires an adequate database and a good understanding of density variability, along with grade and geology. In this paper, the author summarizes density measuring techniques, draws on examples of simple and complex grade-variable density domains, and discusses improved approaches for minimizing density estimation errors.

Jan 1, 2014

By Olaf Kessler, Jan Kalich, Michael Reich, Julia Osten, Uwe Füssel

Modern automobile bodies consist of different materials, e.g. aluminium alloys and high strength steels. Mechanical joining, e.g. clinching, is very suitable for joining aluminium and steel sheet. But clinching needs a sufficient ductility, which is no longer supplied by high strength steels. Laser-assisted clinching has been shown, to be able to join aluminium and high strength steel sheet successfully. Thereby the steel sheets were heated locally for short times to increase their ductility. Due to the thermal contact between steel and aluminium sheet the aluminium alloys also achieve a local short-time heat treatment. This fact may cause a significant impact, as aluminium sheet in automobile bodies is often used in T4 (or similar) condition and later artificially aged during the paint bake cycle. Aluminium alloys 6016 and 6181 have been short-time heat treated with heating rates up to some 100 K/s. Precipitation and dissolution processes have been monitored in-situ by calorimetry. Mechanical properties have been investigated on as well as after short-time heat treatment by deformation dilatometry. The results show, that suitable short-time annealing parameters during laser-assisted clinching can increase ductility and at the same time act as retrogression for aluminium sheets, resulting in increased strength after aging.

Jan 1, 2015

By N. Hosking, M. Nichols

Aluminum alloys are increasingly used for automotive body construction but are susceptible to filiform corrosion or paint blistering in service. Filiform corrosion resistance of two 6000-series aluminum alloys was investigated in this work. Test panels were produced with full automotive coating layers and scribed parallel and perpendicular to the rolling direction. The corrosion exposure comprised an inoculation step with acidified salt solution followed by a 6-week exposure period at 95% relative humidity and either 25°C or 70°C. Greatest corrosion activity was measured on the alloy with higher copper content, AA6111. Higher temperature exposure led to greatly enhanced corrosion activity for AA6111 compared to the lower temperature exposure. The 70°C exposure also led to greater mean corrosion-affected area measurements for the low copper aluminum alloy, AA6022, but the effect was not as stark as that observed for AA6111. Rolling direction affected the propagation direction, and possibly mechanism, of the corrosion effects. Cross-sectional analysis revealed dense corrosion products within the filament, comprising mostly aluminum and oxygen but with traces of chloride and sulphate. Development of varying filament and blister types on a single test panel and the progression of corrosion underneath a filament into the substrate indicate that several corrosion mechanisms can develop on the test panel, testament to the complexity of the corroding surface developed on an aluminum automotive body panel.

Jan 1, 2015

By H. Gharahbagheri, S. Shafiei Zadeh, H. Hassan Nejad, Reza Roostaazad

In this paper, dissolution of vanadium from mining residue, in which vanadium is associated intimately with magnetite ore, was investigated via both bacterial ( aerobic and anaerobic) and fungal activity. Although bacterial activity was tangible, it could not reduce and dissolve vanadium in both aerobic and anaerobic experiments. However, in fungal leaching, after 30 days about 36.9% and 29.7% of vanadium was dissolved for a pulp density of 10 and 30 g/l, respectively. At the end, the concentration of metabolites usually produced by fungal activity was optimized and oxalic acid was chosen as the main agent for the leaching process.

Jan 1, 2014

By W. J. Mcgaughey, M. A. Vallée

"Abstract -The application of geophysical technology to resource delineation aims to improve the quality of resource/reserve estimates by integrating high-resolution survey methods, geophysical modeling and inversion with three-dimensional representations of geological and mineral deposit data. The use of geophysics can cost-effectively improve a geological interpretation based only on geological and sampling data. Success depends upon the ability to use geological visualization and modeling software, first to develop a three-dimensional geological model and then to modify it interactively by integrating geophysical data with the geological and sampling data.The high resolution required for mineral delineation geophysics results in a focus on borehole seismic and high-frequency electromagnetic methods. Borehole wireline logging is used to develop an understanding of the relationship between physical properties and geological description. Data from core samples and borehole wireline logs allow the construction of a three-dimensional physical property distribution, consistent with the existing geological interpretation. The three-dimensional physical property distribution is used for both geophysical forward modeling (to compare to field data) and as a starting model in iterative inversions.Advanced visualization techniques allow the simultaneous viewing of the three-dimensional physical property model, the geological information and data from which it is derived, and the geological interpretation and the geophysical results. Geophysical results may be simulated responses from a forward model or the output from a numerical inversion in the form of an updated physical property distribution. Iterative refinement of the geological interpretation is required to ensure consistency with the geological and geophysical data. The key to success with this approach is that all relevant geological, geophysical, and rock property data reside in a common, visual model of the earth.Examples from massive sulfide deposits illustrate the benefits obtained by the integration of geophysical and geological data."

Jan 1, 1998

By G. Goodall, M. Muinonen, R. Pandher, R. Jabbar, S. J. Muinonen

"The implementation of a new and highly efficient converting practice at the Glencore Sudbury Integrated Nickel Operations Smelter has opened the possibility to further capacity increases by using larger ladles. To quantify the impact of increasing ladle sizes from 200 to 300 ft3, XPS constructed a detailed discrete event simulation using the commercial software package Rockwell Arena®. The challenges associated with implementing a model on an intricate and tightly scheduled process, and the solutions needed to derive meaningful results will be presented. The aisle capacity is predicted to increase by approximately 17 %, with a reduction in furnace tapping demand of 8 %. Arena modeling capabilities and the key factors contributing to the overall capacity increase at the Sudbury INO Smelter will be reviewed and presented.INTRODUCTION The Glencore Sudbury Integrated Nickel Operations (INO) comprises two Ni-Cu-PGM mines, Strathcona Mill, and the Sudbury Smelter. The Smelter has operated continuously since 1929 using different processes to produce nickel-copper Bessemer matte. Feeds to the Sudbury INO Smelter are a blend of concentrate from Strathcona Mill, Raglan concentrate produced at the mine-mill complex in Raglan, Quebec, as well as third party concentrate feeds shipped to Sudbury from around the world. In 2016, the Sudbury INO Smelter produced 75,900 tonnes of nickel and 20,000 tonnes of copper in Bessemer matte. The product matte is shipped to Glencore’s Nikkelverk refinery in Kristiansand, Norway where it is refined to produce nickel and copper cathode. A schematic of the Sudbury INO Smelter’s flowsheet is shown in Figure 1."

Jan 1, 2017

By W. N. Roman

This paper will examine the challenges involved in ventilating and cooling South African mines, with particular emphasis on solutions to the issues of heat (generally associated with depth), mechanization and energy efficiency. Comparisons will be made with other international mining areas. Some of the deepest mines in the world are to be found in the South African goldfields. The Mponeng mine is approaching 4,000 m below surface, with virgin rock temperatures (VRT) of between 60°C and 70°C. Mining at these depths has only been possible with the use of large refrigeration plants supplying cold air, water and ice to the workings. In the Bushveld Igneous Complex, where most of South Africa?s platinum mines are located, similar VRTs are being experienced at significantly shallower depths. This is due to the different geothermal properties of the host rock between the two areas. Existing mines are being forced to go deeper and new underground mines are being planned and constructed in other areas with widely differing thermal conditions. South African metal mining has traditionally been labour intensive for historical reasons as well as for the narrow tabular nature of many ore bodies. Due to cost pressures and labour problems, some mines have been investigating the possibility of using mechanized equipment, both diesel and electric, to increase production and to improve efficiency. Studies have been carried out to determine the effect of the additional equipment on the overall ventilation system and some of the conclusions are discussed. The use of diesel equipment adds heat and pollutants to the ventilation air but, although electrical equipment has a lesser effect on the ventilation systems, it is generally less favoured due to claims of lower flexibility/manoeuvrability. Mechanization holds the promise of more concentrated mining activities but, with higher localized ventilation and cooling needs. Systems which will control the provision of air and cooling more effectively are required and are being implemented. In the 1990s and early 2000s, the South African economy experienced significant growth which was not matched by the growth in infrastructure. Consequently, at present there is a shortage of electricity generation capacity which affects large industrial consumers, including mines. Increasing levels of heat and mechanization will require more electrical energy for ventilation and cooling. There are many initiatives underway to save power or to shift consumption to periods of national low demand and these will be described.

Aug 1, 2013

By A. Makinen

There is an increasing trend between increasing consumption of water and the production of metal concentrate. Along with this trend we see that ore grades are declining and getting more complex to concentrate around the world. This will not only complicate processing but also generate new requirements for the management of water and waste streams on mining sites. The mining industry is a large user of water and its water consumption is growing rapidly. The processing of lower quality ores requires greater volumes of water. For these reasons, the need for efficient use of water and water management at mine sites is becoming more urgent. The perception of water in the mining industry has changed from thinking about it only in terms of "water treatment" to actually seeing it as a valuable resource, a resource that needs proper management. This resource management needs to involve various aspects, such as optimizing water usage of the entire mine or concentrator site, minimizing fresh water usage, minimizing or eliminating waste generated in water treatment and implementing practices for water reuse and water recycling. This paper presents trends and new developments relating to waste and water management in the mining industry.

Jan 1, 2015

By S. Koppalkar

ABSTRACT: The development and evolution of the gravity recoverable gold (GRG) test procedure at McGill University is reviewed in this paper. Since the late 1980s, the research group led by the late Professor André Robert Laplante at McGill University has undertaken fundamental studies and applied research of the Knelson concentrator to develop a sustainable method of estimating GRG. Historically, a concept of “free gold” was used, and it was de?ned as the gold that could be separated and recovered from gold ore by amalgamation. Due to health and safety hazards, the practical use of amalgamation has declined. Around 1994, a methodology using a 3-in Knelson concentrator to measure gravity recoverable gold was established at McGill University. As a result of more than 10 years of improvement and optimization, this technique has become a standard method of evaluating GRG for gold ores, gold plant streams and platinum group metals. By 2006, about 200 GRG tests were carried out at McGill University on ores from all over the world. Recently, a modi?ed version of the GRG test (a simpli?ed test) was developed to provide a quick and rough estimate of the GRG in a sample; this simpli?ed test has the advantage of reduced mass, processing time and cost. To recognize and honour the contributions made by the late Professor Laplante towards the establishment of a standard test procedure for assessing gravity recovery potential, the authors propose that the GRG test be named after Laplante.

Jan 1, 2010

By P. C. M. Knops, K. Rijnsburger, R. M. Santos

To overcome the challenges of mineral CO2 sequestration, this work utilizes a unique proprietary Gravity Pressure Vessel (GPV) reactor technology, and focuses on reaction products of high economic value. The GPV provides intense process conditions through hydrostatic pressurization and heat exchange integration that harvests exothermic reaction energy. Here, laboratory-scale tests of the envisioned process was performed in tubular and continuously stirred tank reactor (CSTR) autoclave reactors. The mineral used was Olivine (~Mg1.6Fe2+0.4(SiO4) + ppm Ni/Cr), although asbestos, steel slags and oil shale residues are also under investigation. The effect of several process parameters on reaction extent and product properties was tested: CO2 pressure, temperature, residence time, additives (buffers, lixiviants, chelators, oxidizers), solids loading, and mixing rate. The products (carbonates, amorphous silica and Chromite) were physically separated (based on size, density and magnetic properties), characterized (for chemistry, mineralogy and morphology) and tested in intended applications (e.g. as pozzolanic carbon-negative building material). Economically, it is found that product value is the main driver for mineral carbonation, rather than, or in addition to, the sequestered CO2. The approach of using a GPV and focusing on valuable reaction products could thus make CO2 mineralization a feasible and sustainable hydrometallurgical process.

Jan 1, 2015

By Erik Spiller

"Water and cyanide are highly contentious and conflict issues that many gold mining companies encounter worldwide when dealing with local farming communities, industries and cities competing for water as well as non-government and government organizations. Historically, the gold industry has used processes that required minimum amounts of water to treat and recover gold at locations around the world. Examples are dry grinding for refractory gold treatment in the late 1800s and early 1900s and dry blowing in arid/desert regions to recover alluvial gold. In recent times, new dry processing equipment has been developed and include equipment such as air tables and jigs. Researchers have also modified a Knelson concentrator to concentrate gold from dry solids. High pressure grinding rolls (HPGR) with air classifiers are used to treat industrial minerals and pilot trials have shown that the technology can be applied to comminute refractory gold ores ahead of roasting. Dry stacked tailings is being applied on gold mines to reduce overall water consumption This paper will review the available technologies that in combination may be able to substantially reduce the quantity of water used in the processing of gold ores.INTRODUCTION Water makes up most of the world: the planet is 75% water. Some 97.5% is saline water largely in the oceans, so that only 2.5% is fresh water and useful for human needs. The demand for water is driven primarily by population and concomitant economic growth. Overall, some 70% of the water withdrawn from the environment is used in agriculture, 20% by industry, 7% by households and 3% for mining (Brown, 2003: Maupin et al., 2010). Whilst the water needs of the mining industry are minor compared to those of agriculture, an operating mine requires a relatively large quantity of water on a daily basis to carry out operations. Mining activities are often located in remote, arid environments, with limited access to water. There are a multitude of water resources available to the mining industry for its needs. However, much of this water is saline and over the last two decades there has been a continual decline in water quality (i.e. salinity has increased). In today‘s world, there are enormous internal and external pressures to reduce water consumption at a mine, and/or alternatively use water not considered a resource by the local community. Strategies to meet these objectives can be achieved by implementing good water management practices, by recycling process water, reducing water losses by evaporation and seepage (i.e. by increasing and improving dewatering practices) and employing new technologies such as dry stacking and dry processing (Dunne, 2010)."

Jan 1, 2017

By Lawrence Devon Smith, Keith Spence, William Roscoe

"In March 2003 the CIM Council adopted and approved the document “Standards and Guidelines for Valuation of Mineral Properties” as developed by the Special Committee of the Canadian Institute of Mining, Metallurgy and Petroleum on Valuation of Mineral Properties (CIMVal). The document is referred to as the CIMVal Standards and Guidelines. The document evolved from a specific recommendation by The Mining Standards Task Force (MSTF) of the Toronto Stock Exchange and the Ontario Securities Commission in its Final Report (January 1999) that the CIM form a committee of valuation practitioners to review and advise on approaches to valuation of Mineral Properties. The CIMVal Standards and Guidelines are organized into two parts: •,Standards which are general rules in the Valuation of Mineral Properties. The use of the Standards is mandatory if the Valuation Report is stated to follow CIMVal (although not mandatory in the sense of having regulatory authority). Definitions are given at the beginning of the Standards. •,Guidelines which elaborate on the Standards and, while not mandatory, provide guidance and best practices which are highly recommended to be followed in the Valuation of Mineral Properties.CIMVal specifies requirements for the Qualified Valuator who has the responsibility for choosing the appropriate approaches and methods for the valuation of mineral properties. With regard to the specifics of the application and practice of valuation approaches and methods, CIMVal directs the Qualified Valuator to the large body of published papers, published valuations, presentations and court judgments to guide his or her choice. This is also the approach taken by VALMIN (Australia) and SAMVAL (South Africa). To facilitate the dissemination of industry practice, the CIMVal Committee organized a “Valuation Day” at the CIM Annual General Meeting in Toronto (Mining Millennium 2000), on March 8, 2000. Industry experts presented papers on valuation of Mineral Properties which were subsequently published in a proceedings volume and individually ad technical papers in the CIM Bulletin. The Management and Economics Society of CIM has continued to identify and publish papers on valuation in the CIM Bulletin and Magazine. The present document gathers in one place the CIMVal Standards and Guidelines, the papers from the 2000 Valuation Day, and a number of subsequent papers that illustrate industry practice for the valuation of mineral properties."

Jan 1, 2003

By Alan S. Lock

Large scale feasibility studies for the establishment of oil-seed and cellulose producing crops on mine tailings have been successfully conducted over 1 growing season with the purpose of these crops to be used as feedstock to the biofuels industry. An acid sulphide tailings impoundment in Copper Cliff, Ontario and a near neutral pH goldmine tailings impoundment in Timmins, Ontario were both tested by amending half hectare plots to approximately 1 m thick with residual biosolids from the pulp and paper industry and growing canola and corn on these plots. Full scale agricultural equipment was used to cultivate seed and harvest the plots to prove the full scale feasibility of farming on these biosolids. The vegetation development, growth, yield, quality and composition were assessed to identify the best species that would maximize biomass development for feedstock to the biofuels industry and carbon credits for the mining industry. Groundwater, biosolids and tailings chemistries were investigated to identify potential deleterious impacts of degrading organic matter on tailings metal mobility. Preliminary hydrologic investigations using moisture sensor profiles elucidate potential conservation of water in amended plots. Tailings amended with biosolids have the potential to provide the mining industry with carbon credits and supply feedstock to this new industry while reclaiming brownfields to a new level, utilizing industrial and municipal organic waste material.

May 1, 2009

By Rebecca L. Jones

The paper addresses the application of XPAC AutoScheduler at the Fort Hills Energy Oil Sands Project to complete fast turn around ?what if? scenario testing of different mine schedules. Traditional scheduling approaches involve engineers making a ?best guess? at the required mining sequence, loading this sequence into a scheduling package and testing the results to determine if the schedule meets corporate objectives. This process is iterative and can be very time consuming. Autoscheduling techniques, on the other hand, are based on the engineer pre defining the mining rules and constraints of the deposit. The software then automatically selects a sequence of mining which the schedule should try and achieve, based off specified corporate objectives. Under this system the engineer is able to adjust the objectives and rules to evaluate numerous scheduling scenarios quickly and easily. An XPAC AutoScheduler model was built, documented, and implemented by Runge and Petro-Canada Oil Sands Inc. personnel in a month. It is currently being used by Petro-Canada Oil Sands Inc. to run multiple schedule scenarios, most taking less than ten minutes configure and ten minutes to schedule. The results of each schedule are tabulated with supporting graphs on; the bitumen grade profile, strip ratio, ore inventories and mined tonnage. In addition to this, the block model may be animated to show the progression of the resources mining the schedules.

May 1, 2008

By B. B. Meadows

"The Minto-Chipman Strip Mining Reclamation Project was initiated to re-vegetate the spoil piles remaining from strip mining operations.All available information was studied by the team responsible, and areas being reclaimed in the U. S. were visited, Methods applicable to the N. B. Project were noted for future use.We have both surface and underground mining operations in New Brunswick, Both deface the natural landscape and reclamation varies in difficulty, Surface operation disturbances are the most difficult to correct.Some of the surface mining is carried out next to two main highways and the results are definite eyesores, With this in mind, it was decided to landscape the spoil ground next to the highways and plant “as is"" the ground remote from the public view.The landscaping entailed various degrees of bulldozing from complete levelling to contouring, smoothing and topping, Bulldozing is, of course, the most expensive part of any reclamation project.There are two phases to the planting program; experimental and operational--experimental both prior and, later, in conjunction with the operational planting.Initially in the experimental project, the pH and composition of the spoil was determined using a grid sampling system. Soil samples were tested in a laboratory at the University of New Brunswick."

Jan 1, 1970

By D. C. McDonald

"IntroductionTHE GIANT YELLOWKNIFE property is on the west side of Yellowknife bay, Great Slave lake, N.W.T., some 600 air miles north of Edmonton. This paper deals with the underground development and mining of the complex system of orebodies which have produced, in the first fifty-six months of operation (May, 1948, to December, 1952), 652,464 tons of ore with an average grade of 0.80 ounces of •gold per ton (1).The mine has been developed from three vertical shafts designated A, B, and C. Figure l shows the positions of these openings with respect to the known ore-bearing zones and the surface plant.A shaft was sunk to a depth of 522 feet in 1945-46, primarily as a prospect shaft for investigation and development of the East Zone orebody. Drifting was carried out on the 200-and 325-foot levels. Before this development had been completed it was clear that the funds immediately available made it imperative to get revenue from production as soon as possible. By the beginning of 1946, the remarkably high-grade character of the ore in the present B Shaft area had been established by surface drilling, and the decision was made to obtain initial production from this source. Since known orebodies at shallow horizons were to be developed quickly, the choice of a suitable rock outcrop for the shaft was something of a problem."

Jan 1, 1953

The following guidelines have been recommended by the Diamond Exploration Best Practices Committee established by the Canadian Institute of Mining, Metallurgy and Petroleum. These guidelines are applicable to public companies and their consultants reporting diamond exploration results. In respect of these guidelines, Diamond Exploration Results are results derived from the initial activities undertaken to investigate a diamond bearing prospect or deposit, to generate tonnage, grade and value estimates that cannot be classified as a Mineral Resource or Mineral Reserve. They do not address the earlier stage reporting of geophysical, geochemical or kimberlite indicator mineral results. Public reports of Diamond Exploration Results relating to mineralization not classified as Mineral Resource or Mineral Reserve must address the confidence limits of the result and contain sufficient information to allow a considered and balanced judgement of the significance of the results. The objective of these guidelines is to assist public companies and consultants in making appropriate disclosure of diamond exploration results by reporting in a manner which is: ??Uniform within the diamond exploration industry; ??Consistent with reporting from other industry sectors; ??Comprehensive; ??Unambiguous. The guidelines are not prescriptive. Materiality is the overriding principle that determines the information that should be disclosed. However, where a company or consultant deviates from the guidelines, the disclosure or technical report should state the extent to which the guidelines have not been followed, and the reasons for the deviation. The guidelines do not in any way replace jurisdictional reporting requirements (For example, the requirement for Canadian reporting issuers to comply with Canadian Securities Administrators National Instrument 43-101 by having technical disclosure endorsed by a Qualified Person as defined in that legislation).

May 1, 2003

By John Shirokoff, Ladan Khaksar

"Cyclic polarization technique and also potentiodynamic measurements were applied to study corrosion behavior of 13% chromium steels in chloride containing environment. Potentiodynamic measurements were performed at 25 and 75 °C with 0, 10 and 20 g/l NaCl in 0.01 M hydrochloric acid solution. At the same time, the significant pitting parameters such as corrosion potential (Ecorr), pitting potential (Epit), protection potential (Epro) and passive current (Ipass) of cyclic polarization curves with various NaCl concentration were analyzed and compared to describe the corrosion behavior of 13% chromium stainless steel. Surface measurement techniques such as SEM and EDS were used for morphology and analysis of corrosion products. The results showed that both temperature and Cl- concentration had significant effects on corrosion behavior of 13% chromium stainless steel in acidic solution.INTRODUCTION Of all the corrosion resistant alloys (CRA) used in oil and gas developments, martensitic stainless steels (MSS) are some of the most common ones these days. These steels not only have the advantages of normal steels: high strength, cost-effective, easy to manufacture, available in a wide variety of product forms, but they also have good CO2 corrosion resistance at higher temperatures as a result of their 11% minimum chromium content. One of the most common types of MSS used in the oil and gas industry is 13% chromium steel. NACE and API standards both reference several different varieties of 13% chromium steels for use in oil and gas projects(“Corrosion Resistant High Cr Steel for Oil and Gas Wells,” 2013). All types of 13% chromium steels have about 12 to 14% chromium and other minor alloying additions, and can be placed into two general groups: conventional and modified. Conventional 13% Cr steels (13Cr) are those most common in oil and gas, some of which are CA6NM (UNS J91150), AISI 410(UNS S41000), and AISI 420 (UNS S42000). These alloys have excellent corrosion resistance when compared to carbon steels up to about 300°F (150°C) and are used for a variety of wellhead, tubular, and downhole components however they have very limited resistance to cracking in H2S (Vallourec Group, 2015). Modified 13% Cr (M13Cr) steels came from the need for increased corrosion resistance at higher temperatures, increased H2S cracking resistance, and increased yield strength above 85 ksi (586 Mpa) primarily for tubular goods and other downhole equipment. These features were developed by taking a conventional 13Cr steel and adding nickel (Ni), molybdenum (Mo), copper (Cu), and other alloying elements. M13Cr provides better corrosion resistance than 13Cr up to about 350°F (177°C), yield strengths up to 110 ksi (758 Mpa), and also improved H2S cracking resistance(“Corrosion Resistant High Cr Steel for Oil and Gas Wells,” 2013)."

Jan 1, 2017

By Vicken Aprahamian

"The Royal Canadian Mint (RCM) operates a gold and silver refining toll operation in Ottawa, Ontario, Canada. The silver refining line is a recent addition and was commissioned in 2005. One source of silver in the refinery is from gold doré which undergoes Miller chlorination before electrorefining to 99.99% cathode gold. Treatment of the Miller salt or silver-copper chloride produced consisted of a 2-stage high temperature reduction process step using soda ash prior to 2005. Copper-rich silver bars were produced and shipped offsite for further refining.The copper-rich bars could not be blended into sufficient high grade silver doré to dilute the copper and allow electrorefining in a silver nitrate medium. A new wet process was developed and commissioned to replace the high temperature reduction and allow removal of bulk copper. Thus upgraded impure silver produced was cast into anode for electrorefining to 99.9% purity silver flake. The 2005 RCM Hydromet Slag process is presented as well as its more current version. In addition, mention is made of a novel processing scenario for the introduction of Miller chlorination silver into the electrorefining circuit."

Jan 1, 2015

By I. Thobadi, C. Pawlik, K. Bisaka, S. Mokoena, M. Erwee

The PyEarth™ process developed at Mintek has been demonstrated successfully at pilot scale. Nine tons of ore containing 2.3 mass % of total rare earth oxides (TREO) from a dormant mineralogically complex iron-rich ore deposit, was subjected to a concentrating smelting step in a 200 kW DC open-arc pilot furnace and the rare earths from the resulting slag were extracted via a hydrometallurgical route. This ore deposit is practically not amenable to extraction by conventional methods. The testwork results proved that the PyEarth™ process was able to optimize the extraction of rare earths while minimizing waste through the removal of iron as a saleable iron alloy. Reduction of iron to the alloy in the smelting step was found flexible, efficient, and controllable, while rare earths were left virtually unreduced in the slag phase. The slag chemistry is selected to optimize both the smelting and leaching performances as well as the alloy composition. Leaching of the resulting slag was found possible and most efficient in hydrochloric acid amongst other lixiviants tested.

Jan 1, 2017