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By J. C. Allan

THE purpose of this paper is to outline the pogress made in the development o the gravity separation method o ore dressing known as Sink-and-Float, which, in the opinion of the writers, has now reached a stage justifying the claim that this new method marks a highly important advance in the technique . The essential feature of the newest development of this process is the extremely accurate separation achieved. This is responsible for higher extraction in the sink-and-float unit on coarse sizes and, in consequence, for substantially higher overall recoveries. Whilst this is the most remarkable feature of the new process, it has further important contributions to make to ore dressing under the following heads: (1) The introduction of the sink-and-float separator as a buffer helps to iron-out irregularities in the mill feed. By supplying a concentrate of constant grade to the flotation section, the process also indirectly improves overall recovery. (2) The addition of a sink-and-float unit to an existing mill results in substantial increase in capacity at low per ton capital cost. (3) Where the plant can be installed underground for the pre-treatment of low-grade ores, there is a saving in hoisting costs, and excellent 'fill' is provided near the point of use. ( 4) Low-grade mixed oxide-sulphide copper ores may be pre-concentrated, thereby producing a flotation feed sufficiently rich to render the oxide residue from such flotation economic for subsequent treatment by leaching or other methods. (5) Application of the process eliminates hard gangue constituents which cause high grinding costs, or gangue constituents which adversely affect flotation. The plant is compact and easily controlled. No highly skilled operators or expensive reagents are required, and the labour and power per ton are low. The separator is extremely flexible, working equally efficiently on any throughput up to its maximum capacity.

Jan 1, 1940

By Peter Broad

"Extracting any metal, especially specialty metals and rare earth elements, requires an in-depth analysis of the costs and potential revenue as well as a due diligence study of other stakeholder interests. Rare earth projects are generally in the billion dollar US range or above, and thus failure to accurately predict any loss of revenue caused by impurities within the product or additional effluent treatment costs can destroy an otherwise viable study. Two prime sources of input impurity are considered: impurities in the material feed and from reagents. The effect of these impurities factor on both the product (in reduced revenue) and on residual “tailings” that may incur additional unforeseen costs.INTRODUCTION“Truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident” – Arthur SchopenhauerThe era of unscoped, unbudgeted construction ended about 150 years ago. Today’s engineer must design with confidence; but do so amidst proprietary secrets and unfamiliar pollutants, which present a myriad of interesting challenges. Is it possible to build a viable rare earth plant to a realistic budget, without destroying that which we cherish? Some see this as contradictory but in reality it is the only viable option.WHEN GOOD PROJECTS FAILWithout rare earths the Copenhagen agreement might be null and void. Running a wind turbine with a 30 tonne conventional magnet requires some hefty engineering and prohibitive investment. Despite their ‘Green metal’ applications, production of rare earths have created environmental nightmares, as Folger stated in 2011 when visiting Baotou, or has Jaing Mainheng who has been quoted by Ambrose Evans-Pritchard 6 Jan 2013. This comment is not a criticism of China; the details are from a 2012 white paper published by the Chinese Government that initiated a $6 billion environmental clean-up. Nor is China unique; other plants have had problems as well. There were toxic leaks in the 1990s from Mountain Pass, and the Mitsubishi Bukit Merah Plant (built in Malaysia in 1958) required a $100 million clean-up."

Jan 1, 2016

By W. E. Newton

THE following notes are offered primarily to show that industrial minerals or their products have a much more important place in the metallurgical industry than is perhaps generally realized, and with the hope also that some statement by the metallurgical consumer of the relative merits of various materials for particular requirements or services will l;>e of value to the industrial mineral producer. These notes are not in any way presented as complete. Also, some of the statements made may be debatable. The grouping adopted is as follows: (1) Refractories; (2) Fluxes; (3) Construction materials; and ( 4) Miscellaneous applications. Fuels are not dealt with in the present paper. REFRACTORIES GENERAL: Refractories are materials which will withstand high temperatures with-out melting or becoming markedly soft or pasty. While their primary function is to withstand heat, they are usually called upon to resist one or more of the following destructive influences: abrasion, pressure, corrosion by slags or fluxes, and rapid changes in temperature. Refractory materials may be conveniently divided into three classes: (1) Acid refractories-consisting of silica, or containing silica as their chief constituent. They combine more or less readily with metallic oxides, forming silicates, and are hence termed 'acid'. The most important of these are quartz, quartzite, siliceous sand, tripoli, Dinas rock, and ganister. Most fire-clays, although generally considered neutral sub-stances, contain relatively small amounts of free silica and are, to that extent, acid. (2) Neutral refractories-the term is merely relative in most cases, since, at high temperature, many of the refractories that are classed as neutral will react chemically with a strong base, functioning as a weak acid; or, conversely, with a strong acid, functioning as a weak base. Chrome and graphite are the most nearly neutral of all the commonly used refractory materials.

Jan 1, 1936

By J. A. Drozdiak, W. Tse, P. P. Rosario

"In a recent publication (SAG 2015), we presented a non-conventional high pressure grinding roll (HPGR)-ball mill circuit as a lower capital cost alternative to the “standard” HPGR circuit. The circuit was designed for the treatment of a hard ore and relatively high tonnage (50,000 t/d). That paper provided details such as flowsheets, layouts, and equipment lists for the two options and compared their calculated capital costs demonstrating significant savings for the proposed circuit. This paper extends the analysis to a third option, a traditional semi-autogenous ball crushing circuit, giving the same level of details and now including the operating cost estimates for all three options for a more comprehensive analysis. Moreover, this work also provides information about the strengths and weaknesses of the non-conventional HPGR circuit when compared to the “standard” HPGR option.This study demonstrates that the proposed non-conventional HPGR-based circuit not only provides a lower overall capital costs for the project if compared to a “standard” HPGR circuit but also brings the capital cost to the level of the traditional semi-autogenous grinding (SAG)-ball mill circuits. In addition, the innovative HPGR circuit provides similar operational cost savings of the “standard” HPGR and thus a significant advantage when compared to the SAG option. With the current capital cost sensitivity for most greenfield projects, the proposed alternative circuit should help make HPGR-based circuits more competitive and thus promote the utilization of a technology that enables higher energy efficiency and reduced greenhouse gas emissions. INTRODUCTIONThe application of high pressure grinding roll (HPGR) technology in comminution circuits is well established for the processing of cement, diamonds and iron ore (Broeckmann & Gardula, 2005), and over the past 10–15 years, this technology has slowly been applied to hard ores in high-tonnage precious and base metal operations. Unfortunately, under the current economic climate, the ability to finance large capital projects has become very difficult and companies tend to have an easier time securing funding if the capital expenditures (CAPEX) are low with a proven process method. The traditional semi-autogenous grinding (SAG) mill / ball mill circuits easily fit into this mould, having been installed in countless plants around the world over the past 30 years with relatively low capital requirements. In contrast, it has been well-documented that HPGR-based circuits are capital intensive with complex material handling systems (Seidel, Logan, LeVier, & Veillette, 2006). Although these circuits benefit from reduced operating costs with the increase in energy efficiency and the elimination of steel grinding media (Rosario, Boyd, & Grundy, 2009), if the company is unable to secure financing to build the plant, these advantages remain out of reach. With the current trend to retrofit existing SAG circuits with a secondary crushing circuit to achieve design throughput, the opportunity to circumvent this gross inefficiency by making HPGR-based circuits more capital friendly would greatly benefit the industry."

Jan 1, 2016

By A. Boehm

"For recycling LD slag into the steel making process, the phosphorous containing calcium silcate phases have to be removed from iron oxide phases. One possible technical solution could be magnetic separation in a wide range of susceptibilities from ferromagnetic to paramagnetic. To check the feasibility of magnetic separation the distribution of the magnetic susceptibility in size classes as well as the liberation of the phosphorous containing phase were evaluated by a new method combining two dimensional physical property analysis with QEMSCAN analysis. The particle size classes of energy controlled comminution products were subdivided into fractions of defined magnetic susceptibility using a hand magnet of well known field properties (pick up method). On the one hand the susceptibility classes were wet assayed on the other hand analyzed by QEMSCAN followed by data evaluation using iDiscover 5.3.1(FEI), which was adapted to the data structure of two physical properties (size and magnetic mass susceptibility). The results allow the comparison of mass based (3D) cumulative distribution of grades from the wet assays with the area based (2D) distribution from QEMSCAN analysis, in order to control a systematic (size dependent) stereological error for this special type of material. As the physical separation property forms a crucial parameter the results from the liberation analysis by QEMSCAN can be interpreted more profound with respect to an expectable separation result. Once the various mineral compositions of the particles are assigned to the physical properties the Henry Reinhardt chart serves to predict the best possible separation result and thus the feasibility of a separation technique.INTRODUCTIONThe two Austrian steel plants operated by voestalpine AG produce about 650,000 t (voestalpine 2014) of LD slag in the course of steel production from pig iron according to the basic oxygen process blowing oxygen in the converter by an oxygen lance. The process is also known as the Linz Donawitz (LD) steelmaking process. By the addition of lime (CaO), carbon, phosphorus, silica, manganese and sulfur, which are present in the molten pig iron, shall be oxidized and bound in the slag either as oxide or silicate phases, or leave the slag in the gaseous phase (CO). The average chemical composition of the investigated LD slag is given in table 1."

Jan 1, 2016

By K. Matsuura, M. Ohno, T. Tokunaga

"Recently, weight saving of automobiles has been strongly required to solve the global environmental problems. Mg alloys are one of the promising candidates as a new material for automobile components. However, the application of the Mg alloys is limited due to their poor corrosion resistance. In the authors’ preliminary study, an Al/Mg/Al clad sheet was fabricated by hot extrusion and subsequent hot forging. The clad sheet exhibited a high corrosion resistance and excellent super plasticity. More specifically, the elongation of the clad sheet was as high as 550%.Importantly, despite that the elongation of Al itself was only 40%without cladding with Mg, the ductility of Al was greatly improved in the form of the clad sheet. In the present study, in order to clarify the mechanism of the superplastic deformation of the Al part in the clad sheet, the microstructure evolution of the Al during the tensile de formation is investigated. The tensile tests were conducted at a temperature of 573 K and at a strain rateof1.0×10-3s-1. The Al exhibited fiber-type texture at the beginning of the tensile deformation, and brass-type texture after the elongation of 50%.INTRODUCTIONMg alloys have been gaining attention because of their excellent properties e.g. light weight, good recyclability and high electromagnetic shielding. However, their practical applications have been limited due to their poor corrosion resistance. In the authors’ previous study, in order to solve this problem, Al coating on Mg alloy by hot extrusion has been proposed, and the Al-coated Mg alloy plate was fabricated(Tokunaga, Matsuura, &Ohno,2012). The plate was hot-rolled and an Al/Mg/Al clad sheet was fabricated. No cracks or debondings were observed at the Al/Mg interface. The sheet exhibited a high corrosion resistance in a comparable level as pure Al. Also, the sheet exhibited a large and uniform elongation of 550%in a tensile test at a temperature of 573 K and at a strain rate of 1.0×10-3s-1without any breakings or debondings of the Al part(Tokunaga, Matsuura, &Ohno,2014).Mg alloys have been known to exhibit a superplastic characteristic when the grain size is small. However, it is known that the pure Al does not generally exhibit the super plasticity. As mentioned above, the Al-coated Mg alloy sheet exhibited 550% of elongation in the authors’ previous study (Tokunagaet al., 2014). However, the pure Al itself showed only 40% of elongation, while the Mg alloy itself exhibited 800% of elongation. Thus, it has been demonstrated that the pure Al was super plastically elongated when it was bonded with the Mg alloy. Generally, deformation mechanism of the super plasticity of the Mg alloy is known as a grain boundary sliding. On the other hand, the mechanism of the superplastic elongation of the pure Al is still unclear. The purpose of the present study is investigation of the deformation behavior of the Al part in the Al/Mg/Al clad sheet during tensile de formation."

Jan 1, 2018

By L. Gawlik

Since the beginning of the 20th century, coal has been the world?s main source of primary energy. In the last few decades, consumption of coal has gradually decreased in some European countries and elsewhere due to the introduction of other energy sources. Regardless, industry continues to use solid fuels for energy production despite of their association with carbon dioxide emissions (about 7 billion Mg). For global development going forward, it is important to estimate what level of energy consumption can be expected as far into the future as the next few decades. To answer this question, specialized global institutions such as the International Energy Agency, the World Energy Council, the World Coal Institute, the U.S. Energy Information Administration, the International Institute for Applied Systems Analysis, as well as oil companies (BP, Shell), conduct periodic forecasts of world energy consumption. The development of such forecasts is very complex because their reliability is influenced by many factors that are difficult to estimate, such as economic development, population growth, climate change, and public awareness. We are all aware that the global demand for electricity will rise significantly in the coming years as a result of anticipated population growth, industrial development, rising living standards, and the general development of civilization. The world?s mineable resources in 2010 were as follows: coal 665.6 million Mg, brown coal 195.4 billion Mg, oil 163 million Mg, and natural gas 185.5 billion m3. The annual global primary energy demand in 2008 was more than 12 billion toe (12,267 Mtoe). In 2006, electricity production in the world amounted to 18,921 TW?h. The structure of the primary energy mix in TW?h (2006) was as follows: coal 41.0%; natural gas 20.1%; nuclear fuel 14.8%; hydro energy 16.0%; liquid fuels 5.8%; and other renewable energy sources 2.3%. The European Union (EU) is one of the largest coal consumers in the world. In 2010, the EU-27 produced 396.1 million Mg of brown coal, and 132.9 million Mg of hard coal; 188 million Mg of coal was imported from outside the EU. The largest hard coal producers in the EU-27 are Poland, Great Britain, Germany, the Czech Republic, and Spain; major brown coal producers are Germany, Greece, Poland, the Czech Republic, and Hungary. For many years, the Polish energy sector has been based on domestic fuel sources ? hard coal and brown coal. The characteristic feature of the Polish balance of primary energy resources is a very high share of coal ? much higher than the world average. Pursuing the decarbonisation of the Polish economy may jeopardize Poland?s energy security, leading to a significant increase in electricity prices, which would hamper the country?s economic development. Price volatility and supply uncertainty are now the dominant features of the international markets for oil and natural gas. The high share of these fuels in meeting energy needs is the reason for unrest in many countries, including those in the EU. Under these circumstances, coal may become the stabilizing element of EU energy security.

Aug 1, 2013

By W. W. Muir

"The Baker Mine used a 100-ton per day conventional cyanide leach mill located in northern British Columbia. A production decision was made in early 1980 and the mill was on fine in April 1981.Ore reserves had been estimated at 100,000 Ions averaging 0.9 oz gold per ton and 18 oz silver per ton . Mineralization consists of electrum (Au/Ag) and acanthite (Ag2S).This paper will review plant design and focus on some problems associated with start-up and early operation with the intention of assisting other mine operators by indicating potential problem areas.IntroductionThis paper will discuss operating strategies employed at Baker which improved over-all mill performance. Also included are some ideas which could be steps toward a more efficient operation in a similar setting.Actual dore production by mine life was 37,606 oz gold and 742,117 oz silver.Figure 1 illustrates the relative stability attained over the mine life. Metal recoveries for gold and silver were 92% and 85% respectively.Safety at Baker was of prime importance because of its remote location. Baker received the Mine Safety Association ""Small Mines Award "" in two of its three operating years. At shutdown in late 1983 the mill had operated for over 850 days without a lost-time accident."

Jan 1, 1985

By Takahiko Okura, Chiharu Tokoro, Shunta Shibuya

Copper concentrates bearing arsenic as enargite (Cu3AsS4) or tennantite (Cu12As4S13) have disadvantage on copper smelting environmentally and economically, so those concentrates should be treated decently. In this paper, some experiments of arsenic removal from several kinds of copper concentrates by heat treatment in an inert atmosphere were discussed. In this study, several samples in which arsenic contents varied 0.18 to 8.3 wt % were heated to the temperature range of 400 °C to 700 °C under argon gas flow during 1 hour. The heat residues and volatilized materials (V.M.) were analyzed by XRD, XRF, ICP-AES, XAFS and MLA to analyze residual concentration of arsenic and residual mineral composition. Experimental results showed that arsenic removal from copper concentrates advanced in 2 steps; at the temperature range of 500 ° C to 550 °C and of 550 °C to 650 °C, respectively. MLA analysis showed that a few of arsenic in enargite was removed by 550 °C heating and a majority of it was still combined with copper and sulfur as tennantite. On the other hand, arsenic in tennantite was removed almost completely by 650 °C heating. Furthermore, a particular type of arsenic mineral, such as Cobaltite (CoAsS) still remained after heating at 700 °C.

Jan 1, 2014

By D. Saramak, Z. Naziemiec

"Chalcedonite is an unique rock due to the relatively small area of its occurrence. It also possesses multi-raw-material features therefore it should be given a special protection aiming at its complete and optimal utilization. It is the natural sedimentary rock and the only mine in Poland, located in Inowlodz, where the opencast mining from “Teofilow” deposit is carried out.Chalcedonite mainly consists of cryptocrystalline and microcrystalline chalcedony together with small amounts of autogenous and detrital quartz. The chalcedony itself is a fairy common mineral and many forms of its occurrence is known, some of them are semi-precious minerals. Among the most popular ones following can be found: agate, bloodstone, onyx, carnelian, chrysoprase. Many countries own chalcedony deposits: Australia, Brazil, India, Canada, Namibia Russia, South Africa. However chalcedony in its pure form does not occur in the mentioned chalcedonite rock. The pores, which take usually from 5% to 25% of volume and have sizes smaller than 0.5 mm, are the characteristic feature of all chalcedonite forms. The paper presents some crucial problems of its processing together with most significant directions of its applications. New method of chalcedonite enrichment based on densimetric separation (patented in Poland) is presented. Results of investigation show that the obtained products can increase quality of concrete and filter grits."

Jan 1, 2016

By P. Mottahed, E. De Souza

One of the major unsolved problems of safe, economical roof support in the evaporite industry has been that of obtaining and maintaining anchorages in relatively soft rock. This is due to the viscoelastic and viscoplastic behaviour of salt rock and associated deposits. This paper introduces a low-cost, yieldable support mechanism, consisting of a system of buckling disks, which provides viable solutions to dynamic support. The yieldable support system offers a number of advantages in comparison with existing dynamic support systems. It is characterized by its simplicity in design and installation, repeatability in behaviour and cost effectiveness. It also has the added advantage of providing the operator with a means of assessing support behaviour and ground performance by direct visual observation of changes in disk shape. Thus, the system can be utilized as a warning mechanism of ground stress and support load conditions. Such system not only provides a feasible and more effective rock mass stabilization strategy but improves mine safety.

Jan 1, 1999

By Yufeng Yao, Robert P. Lowell

Abstract - Conductive heat flow anomalies associated with hydrothermal sulfide mounds on the seafloor have been studied. Sulfide mounds tend to focus conductive heat flow because sulfide minerals have a greater thermal conductivity than country rock. The topography of the mound above the seafloor, however, leads to a reduction of heat flow, particularly near the center of the mound. Because the focusing effect is constant, whereas the topographic effect decreases with distance away from the center, the focusing effect dominates toward the edges of the mound. The magnitude of these effects depends upon the conductivity contrast and the height/radius aspect ratio of the mound. Conductive heat flow anomalies at sulfide mounds also result from fluid circulation within the edifice. For the active and relict mounds at the TAG hydrothermal field, which have an aspect ratio of approximately 0.3 and a conductivity contrast of 3, the heat flux through the center of the mound should be roughly 70% of the background heat flux. The maximum effect of heat flow focusing is to increase the heat flux by about 30% above background. By comparing these effects with conductive heat flow data at TAG, we find that advective processes dominate conductive heat flow at both the active and relict mounds. Advective circulation can also give rise to much larger lateral and vertical temperature gradients than would result from conduction alone.

Jan 1, 1999

By D. Van Tonder

ABSTRACT The comparative economics of ion exchange and direct precipitation have been analyzed by developing indicative CAPEX/OPEX models for typical alkaline leach uranium circuits. An agitated tank ore leach application is considered, comparing resin-in-pulp and direct precipitation as recovery options. Capital and operating cost estimates are derived from rates and factors used in recent studies and projects. The analysis showed the main economic drivers to be the ore grade and resin loading. The resin loading is impacted by the prevalence of competing ions, especially chloride. At resin-in-pulp solution chloride concentrations below 3 g/L and uranium grade below 640 g/t U3O8, resin-in-pulp is more economical, whereas at chloride concentrations above 3 g/L, direct precipitation is more economical.

Jan 1, 2012

By V. Sheikhzadeh, M. Saghaeian, R. Hejazi, P. Ghobadi

Design and selection of equipment for a grinding circuit strongly depends on the mill function, ore properties and requirements of the down-stream circuit. Primary mills usually work in open circuit and size distribution of product would be controlled in the final steps using a classifier like cyclone. Although HPGRs are mostly utilized as pre-grinding mills, it is preferred to utilize them in a closed circuit due to their specific mechanism of comminution. Unique mechanical design of HPGR and its completely different crushing process than tumbling mills needs precise consideration on its circuit design. In this paper, we investigate the impact of different parameters on design of pre-grinding HPGR circuit and selection of the proper classifier. Our study focuses on iron ore properties (e.g. moisture, particle size distribution of feed and product, compatibility and de-agglomerability). We also investigated various options of HPGR circuit according the classifier efficiency and influences on down-stream processes. The optimum operating parameters of HPGR (working pressure, speed and level of hopper) for the selected circuit were also determined based on pilot and industrial data. Our pilot and industrial tests and observations revealed that HPGR should be arranged in closed circuit because of the edge effect, as a negative factor of non-uniform distribution of pressure force along the roller width and presence of non-crushed particles in the mill product. Wet vibratory screen could be the optimum option for screening of its discharge. Fine part of the wet screen discharge could be delivered to the concentration stage without over-grinding in ball mill using a hydrocyclone working in a reverse closed circuit mode. Moreover, our pilot and industrial tests during design and operation of ten HPGRs in various iron ore processing plants proved that higher pressure and lower roller speed in a fixed level of material inside the hopper could give the desired product size distribution.

Jan 1, 2016

By C. J. Sullivan

Many metalliferous ?provinces are co-extensive with particular groups of sedimentary, volcanic, or :basic plutonic rocks. Deposits may be truly syngenetic (Rand, Rhodesia-Katanga, Mans-field, Blind River, White Pine); re-. concentrated by circulating waters (Colorado Plateau, Red Bed Coppers) ; or re-concentrated thermally during metamorphism and granitization (most uranium and lead-zinc provinces ?and some copper and gold provinces). Basalts may yield important cop-per provinces when folded and re-heated. Granitization of basalts which have not reached the chlorite-carbon-ate phase of metamorphism may produce copper provinces. If they reach ?the chlorite-carbonate stage, granitization may result in a gold province. Copper and copper-nickel provinces may result if gabbros are granitized, and a ?similar alteration of per-idotite may result in asbestos or nickel ores. Many similar associations are known. Granite is not a source of ore, but a result of heat. A classification of ?ore with respect to source rocks is of greater prospecting value than are classifications based on magmatic differentiation and hydrother-mal solution theories. Volcanic centres are important ore foci because the thermally unstable metallic sulphides may be concentrated here by a distillation process. The ores found in the hot spring deposits, viz., mercury, mercury sulphide, sulphur, and the compounds of ?antimony and arsenic, are not those which are soluble in water at low temperature (epithermal sub-division of hydrothermal class), abrut those which are unstable thermally at comparatively low temperatures . Water is one of the most common thermally unstable minerals, and generally accompanies the thermally activated ore-forming sulphides.

Jan 1, 1957

By S. Kelebek, E. Yalcin

This paper reports bulk flotation characteristics of a pyritic gold ore sample from the Barry District, Quebec using isopropyl and amyl xanthates. The ore sample was highly floatable with particles showing tendencies for self-aggregation that was most apparent in the first stage of flotation. A possible reason for this is discussed. The gold concentrate grade-recovery performance with respect to the particle size is presented for the rougher-scavengers as well as for the cleaners. The effects of copper sulphate as an activator, fuel oil and NaSH as a sulphidising agent are discussed along with the recovery by size behaviour.

Jan 1, 2011

By M. J. Nicol

The leaching of gold with thiosulfate solutions in the absence of ammonia and copper ions was investigated using electrochemical and kinetic methods. In sodium thiosulfate solutions, the electrochemical oxidation of gold was hindered and the leaching rate using pure oxygen as the oxidant was very slow. It was found that the addition of a small amount of thiourea or formamidine disulfide to the thiosulfate solution greatly enhanced the oxidation of gold. However, the enhancement to the overall dissolution of gold using dissolved oxygen as the oxidant was limited. This was attributed to the fact that the oxygen reduction process was unaffected by the additives and remained slow, which limited further improvement to the overall kinetics. An alternative oxidant, the ferric EDTA complex having a reduction potential of approximately 0.12 V, was found to be promising. The cathodic reduction of ferric EDTA was fast and reversible at neutral pH. While the ferric EDTA complex was effective in oxidizing gold, it did not appear to significantly oxidize thiosulfate. A thiosulfate solution containing thiourea and ferric EDTA has been shown to quickly dissolve gold in the form of a powder as well as from gold ores. In the leaching with the ores high gold recoveries of above 90% was achieved with the best performance obtained in neutral solutions (pH 6-7).

Jan 1, 2005

By Pravin Mathur

"Praxair's CoJet® technology was introduced in 1997 to effectively inject chemical energy in electric arc furnaces. Coherent jets were invented as a revolutionary means of injecting oxygen and other gases into the EAF and into converters. Today, steel makers have widely accepted this concept in over 70 EAFs worldwide. Indeed, the whole industry has shifted to this new standard for chemical energy input in EAFs. CoJet® technology has also been implemented successfully in BOF converters.This paper will review the principles of coherent jets as applied to steelmaking. The key learnings garnered from several furnaces are also reviewed. In addition, while the CoJet® program has been widely accepted worldwide, based on steady feedback received from customers and the market place, several programs are underway in development and commercialization. These enhancements and new applications of CoJet® technology are also overviewed in the paper."

Jan 1, 2004

By G. R. McMeekin

"THE TOPIC suggested for my contribution to this Symposium was ""Lead-Zinc Smelting - 40 Years of Pollution Control"". The history of the development of smelting industry at Trail and the control of sulphur dioxide could make quite an interesting historical study. However, in the field of environmental control, the public is not particularly interested in what you did yesterday, but rather what you are doing today and what you are planning to do tomorrow. I can't fault this approach, but because there are some subject lessons that history can demonstrate, I would like to tell enough of the story (under three headings) to bring a focus on matters of contemporary concern in regard to public relations and ecology. The three general headings suggested are: (1) time before the capture of by-product sulphur; (2) the capture of sulphur; and (3) the ecological and public relations conclusions from these."

Jan 1, 1972

By R. F. Baxter, C. M. Read, R. I. McCulloch

"Globalization of the aluminium industry continues to increase the pace of change and the intensity of competition, while simultaneously, society demands better products, cleaner technologies and sustainable industries. Bechtel, a global engineering, construction and project management company, is not immune to either the opportunities or the challenges created by globalization. However, and not withstanding the challenges, for aluminium industry ""players"" with a true global perspective, globalization presents very real opportunities that may be leveraged to deliver value creating goods and services. The following paper will focus on the exploitation of one of the opportunities created by globalization in the Knowledge Management domain - the application of high level tools and methodologies to improve global delivery of greenfield and brownfield aluminium smelter construction projects. Specific examples will be presented of value driven solutions that were delivered at the early stages of project engineering."

Jan 1, 2006