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By Kang-In Rhee

A series of processes to recover the gold from electronic scrap which contains initially about 200-600 ppm Au have been developed. First, mechanical beneficiation including shredding, crushing and screening was employed. Results showed that 99 percent of gold component leaves in the fraction of under 1 mm of crushed scrap and its concentration was enriched to about 800 ppm without incineration. The scrap was leached in 50% aqua regia solution and gold was dissolved completely at 60°C within 2 hours. Other valuable metals such as silver, copper, nickel and iron were also dissolved. This resulting solution was boiled to remove nitrous compounds in the leachate. Finally, a newly designed electrolyzer was tested to recover the gold metal. More than 99% of gold and silver were recovered within an hour in electrowinning process.

Jan 1, 1995

By Hector M. Henao

The FeOX-CaO-SiO2 base slag at intermediate oxygen partial pressures is very often used in non-ferrous smelting processes. This slag would also contain Al2O3 and MgO because these compounds are normal components in the ore and the refractory of a furnace. The objective of the present work is to determine the effect of Al2O3 or MgO addition on the liquidus temperatures of the plain FeOX-CaO-SiO2 slags in the atmosphere between intermediate pO2 of 10-6 and that of iron saturation at 1250 and 1300 °C. The experiments were carried out at given mass%CaO/(mass%CaO+mass%SiO2) ratios ranging from 0 to 1 and at spinel-tridimite double saturation. The experimental results show that the effect of Al2O3 or MgO addition on the plain FeOX-SiO2-CaO slag is not uniform and depends on the content of Al2O3 or MgO, the oxygen partial pressure and the mass% CaO/mass% SiO2 ratio. It is apparent that Al2O3 or MgO addition enlarges the spinel or wustite saturation area at almost all the oxygen partial pressures and temperatures of this research. The obtained phase diagrams will be useful in the metallurgical industry to assist in the selection of slag chemistry, operation condition and development of new processes.

Jan 1, 2006

By Chao Du, Xiaohui Ning, Hongmin Zhu, Qiuyu Wang, Shuqiang Jiao

"TiCxOl-x solid solutions were synthesized by sintering a mixture of titanium carbide and titanium monoxide at 1600 °C. The corresponding structures and morphologies of the TiCxOl-x solid solutions were characterized by XRD and SEM. A series of tests has been performed on the electrochemical dissolution behavior of TiCxOl-x solid solutions in NaCl-KCl molten salt. The influences of synthesis time and electrokinetic parameters on the anodic dissolution behavior were also investigated. The results showed that TiCxOl-x solid solutions can dissolve as Tin+ into alkali chloride melt. Titanium ion species dissolved from TiCxOl-x solid solutions changes between Ti2+ and Ti3+ depending on the applied potential. The tail gas on the anode was monitored by a mass spectrometer. It was found the synthesis time significantly affects the components of the anodic gas.IntroductionTitanium and titanium alloys have been desired greatly because of their many uses. The critical factor that restricts the range of uses for Ti is its high cost of extraction. The primary titanium metal, sponge titanium, is still produced industrially worldwide by a process invented by Dr. Kroll in the 1940s[1] •Since the early 1970s, the research focus of the titanium industry has been directed towards developing a continuous process to produce high purity titanium at low cost. [2-10] Of the many alternative methods that have previously been investigated, the electrolytic process has been considered a promising method for titanium metallurgy [4-10]. Recently, several electrolysis and related methods such as the PFC-Cambridge process[11-15], calciothermic reduction[16-18], USTB [19,20] and MER[21] process were extensively investigated.The USTB process is a new approach where the pure titanium can be directly obtained by the electrolysis with an anode of titanium oxycarbide in molten salts[19, 20]. The titanium oxycarbide was produced by carbothermal reduction of titanium dioxide under vacuum at a temperature"

Jan 1, 2011

By W. C. Hellyer

The papers in this section provide several examples of the application of Process Mineralogy to metallurgical problems. Any experienced metallurgist could cite numerous other examples when process mineralogy has, or could have, provided data of value in his understanding of metallurgical processes. The data developed by mineralogic techniques may supplement conventional chemical analyses, but cannot be replaced by assays. Mineralogic and chemical analyses each provide different types of information. In order for the process mineralogist to interpret his results in the most useful manner, it is desirable that he should have some knowledge of metallurgical processes. Conversely, the metallurgist should have some knowledge of mineralogic techniques to understand the scope and limitations. Mineralogic examinations are time-consuming and expensive. To ensure the effort is not wasted, and indeed does not generate misleading information, the utmost care must be taken at every stage of sampling and sample preparation. The mineralogist may examine microscopically or by x-ray diffraction a one-gram sample representing a flow of possibly thousands of tons per day through a concentrator. Conditions in a concentrator change continually in response to changes in feed rate, feed characteristics, grind, reagent additions, temperature, circulating loads, etc. Lengthy sampling periods are required to ensure the samples examined are representative of average conditions. The sampling program should be drawn up jointly by the metallurgist and mineralogist. Sampling points should be selected with a view to ease of sample cutting. The sampler should be instructed in the method of cutting the samples, the weight or volume of sample to be taken at each cut, the sampling frequency, and sampling period. The sampling period required depends on the scope of the investigation. For example, if a complete survey is to be made of all final and intermediate products of a flotation concentrator, samples should be cut at not more than two-hour intervals, twenty-four hours per day, for not less than one week. For a more limited investigation of one circuit or one section of a concentrator, 'the sampling frequency could be increased to every hour and the sampling period reduced to one or two days.

Jan 1, 1981

By V. I. Lakshmanan

"Historically flowsheets are developed for efficient separation of metals for economic recovery. With increasing emphasis on reduction, reuse and recycle (3Rs) efficient methods are sought to recover values from a variety of feeds where cost of collection, transportation, local consumer behaviour and regulatory guidelines dictate the development of economically viable flowsheets. Innovative understanding of potential market applications can provide means to develop value added end products. The paper with examples will discuss the use of innovative-separation technologies to obtain value added end use materials from secondary sources.IntroductionFlowsheets are developed for the efficient separation of materials of value for economic recovery. However with increasing societal pressures and regulatory initiatives for stricter environmental guidelines, there is strong need to provide focus to recover materials efficiently and economically in an environmentally accepted manner. North American industries are increasingly caught between demands for high technology value added products and responsibility for environment. An aspect that is receiving increasing attention is Design for Environment'. This incorporates a system wide approach for product design and incorporates environmentally preferable features such as recyclability, disassembly, maintainability, reusability and use of safe materials as part of a product's design objectives.The present paper with case histories will address innovative flowsheet development to convert wastes into recyclables value added products or for minimising generation of waste materials. Case HistoriesProcess for Separating Fibres from Composite Materials 1In the automotive industry, sheet molded compound (SMC) is used to produce panels, bumpers and the like. During the manufacture and at the end of life, considerable waste materials are generated which are potentially recyclable. Fibre reinforced plastics where fibre substrate impregnated with thermosetting resin, find applications in several manufacturing processes and are potentially recyclable at the end of life."

Jan 1, 1996

By M. I. Novgorodova

An overview of the systems Au-Ag and Au-Cu is given. The nature and levels of concentration of various elements occurring with native gold is reviewed. The examples cited are mainly from the USSR. The lack of homogeneity within naturally occurring Au-Ag solid solutions is examined.

Jan 1, 1991

By Jae-Ho. Lee

For some electronic applications where a dispersed electrically-conductive particulate-phase is employed, the conductivity of the surface (or near-surface region) of the particles provides for the primary mechanism which determines its electrical conductivity. Particles of a less expensive material, which may have desirable thermal-expansion properties, when coated with silver offer a means of also obtaining desirable electrical properties and at low cost. The research conducted was focused primarily on the development of silver-coated tungsten particles for thick-film polymeric conductors. The ammoniacal electrolyte was formulated from silver-nitrate, glycine inhibitor and formaldehyde reductant. The reduction, and subsequent deposition, of silver occurred selectively on the surface of the tungsten particles. Coated particles were assessed by SEM imaging. The thickness of the silver coating was estimated to be approximately 100nm on the basis of a mass account and the coating being uniform. The electrical conductivity of a silver-coated tungsten-powder pellet was found to be similar to that of a silver-powder pellet, of identical geometry.

Jan 1, 1997

By A. E. Torma

In recent years the copper industry has gained considerable economic stability. An essential part of this industrial wealth is attributable to the successful application of bio-mediated heap and dump leaching techniques in the recovery of copper from low-grade resources. This study evaluated the leachability of a chalcopyrite conlentrate using naturally occurring mixed culture of predominantly Thiobacillusferrooxidans and Thiobacillus thiooxidans. For the effects-of pulp density, the overall reaction rate constant (k) and the order of reaction (n) have been determined to be 1.93 h-1 and 1.36, respectively. Cyclic voltammetric measurements revealed that intermediate reactions are involved in the chalcopyrite oxidation. Using the Price approach, it was shown that the dissolution of chalcopyrite is solid state diffusion controlled.

Jan 1, 1992

By John A. Thorpe, Gary R. Maxwell, Kirk M. Schall, Kenneth A. Brunk

"Gold ores containing oxide and some sulfide copper minerals incur significant cost penalties when leached with cyanide, because 4-5 moles of cyanide are consumed for each mole of leached copper. This equates to ~4 kg of NaCN per kg of leached copper. Total cost of excess NaCN consumption plus CN destruction can exceed $4.00 per tonne of ore. AuGMENT Technologies has patents pending on a process that can 1) economically recover 70-80% of the cyanide that is fed to a mill, 2) produce salable copper cathodes, and 3) reduce the need for a cyanide destruction facility. Standard equipment for resin processing and electrowinning are used to recover the cyanide and produce the copper cathodes. Steps have been taken to determine: 1) how to develop the resin kinetics, 2) how much savings are incurred at a mill site, 3) how the novel 'electro-elution' circuit achieves efficient operation.IntroductionWhen gold ores containing nuisance copper are leached with cyanide, a significant cost penalty is incurred because 4-5 moles of cyanide are consumed for each mole of copper that leaches. This is equivalent to the use of -4 kg of NaCN per kg of copper that leaches. The total cost of excess NaCN consumption plus cyanide destruction can exceed $4.00 per tonne of ore.AuGMENT Technologies has a patent pending on a process that can 1) economically recover 70-80% of the cyanide that is fed to a mill, 2) produce salable copper cathodes, and 3) reduce the need for a cyanide destruction facility. This ACCS (Au-.C.u-.C.N Solution) Process Technology involves the novel application of copper cyanide chemistry. Standard resin processing and electrowinning equipment are used to recover the cyanide and produce the copper cathodes."

Jan 1, 1997

By Toshiaki Tsuru, Takeshi Ohgai, Hisaaki Fukushima, Shigeo Kobayashi, Tetsuya Akiyama

"Electrodeposition behavior of Zn-Cr alloys from the methanol baths was investigated. In the methanol baths of low Cr3+ concentration, Cr (III) compound was incorporated in the deposits and no lusfrous Zn-Cr alloys was deposited. However, Cr was existed as metallic state in the deposits obtained from the baths of higher Cr3+ concentration. With an increase in water content in the baths, the chemical state of Cr in the deposits changed from metallic to trivalent state. Under the condition that metallic Cr can be electrodeposited, Zn deposition was significantly polarized to the potential of Cr deposition.INTRODUCTIONAn attention has been paid to Zn-Cr alloy plated steel sheet because of its excellent properties for body panels of automobile and electrical appliances [1]-[4]. This plating process can be operated using the sulfate solutions containing Cr3+ ion [1] - [6].In decorative single Cr plating, on the other hand, many attempts have been made to electroplate Cr from trivalent electrolytes, which is motived by environmental deficiencies of the presently used hexavalent process [7]. [8]. However, it has been reported that in the aqueous solutions the behavior of the electroreduction of 0 3+ is atypical due to the complicated nature of the chemistry and electrochemistry of cr3+ species [9]-[11]. Even in Zn-Cr alloy plating, it is difficult to codeposit metallic Cr with Zn in simple sulfate electrolytes [l]-[4], [12]. Therefore, it can be expected that the electrodeposition behaviors of Zn-Cr alloys as well as Cr are significantly changed when the electrodeposition is conducted in non-aqueous plating solutions.In this study, the electrodeposition of Zn-Cr alloy was conducted from methanol solutions to clarify the electroreduction mechanism of Cr3·-Cr0 in the alloy deposition process."

Jan 1, 2000

By A. V. Tarasov, A. D. Besser

A processing flowsheet has been developed for treating substandard lead-containing polymetallic bulk concentrates and intermediate flotation products containing precious metals, which comprises oxidizing roasting in a calcination kiln and electrothermic smelting generating low volumes of off-gas. The proposed flowsheet also incorporates a dust collection system and sulfur dioxide recovery from off-gas. It is proposed to implement this process by using a reaction smelting technique. For this purpose, the charge to be fed to the smelting furnace after its calcination in a drum-type rotary kiln must have a ratio of sulfide sulfur to sulfate sulfur of at least 1 :2. Electric smelting makes it possible to produce lead bullion that also collects the precious metals contained in the feed, as well as copper-lead matte and slag containing zinc. The recovery of lead into lead bullion and into matte is approximately 83% and 14%, respectively (thus the overall recovery is 97%); the total recovery of gold and silver into lead bullion and matte is 98%; th\lt of copper into matte is 89%; the recovery of zinc into slag is 96%; and that of sulfur into sulfuric acid or gypsum is 90%. After the recovery of zinc from slag, the latter can be utilized in the construction industry.

Jan 1, 2000

By Shadia J. Ikhmayies

CdSxTe1-x and CdS1-yTey solid solutions are usually formed in the interfacial region in the CdS/CdT thin film solar cells during the deposition of the CdTe layer and/or the processing steps of the device. It is well known that CdCl2 heat treatment encourages the formation of the CdSxTe1-x alloy which improves the solar cell performance. In this work, indium doped CdS1- yTey thin films are produced by first producing CdS:In thin films by the spray pyrolysis (SP) technique on glass substrates, then annealing the films in nitrogen atmosphere in the presence of elemental tellurium. The films are characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and transmittance measurements. The transmittance is used to deduce the optical parameters such as; the extinction coefficient, refractive index, besides to the real and imaginary parts of the dielectric constant. The dispersion parameters such as Eo (single-oscillator energy) and Ed (dispersive energy) of the deposited films are also estimated and discussed.

Jan 1, 2015

By J. W. Matousek

Copper losses in smelter slags are :typically normalized with some form of the distribution coefficient, written as the ratio of the weight percent assays of metal in slag to the metal in matte or its inverse: L(s/m) = %(Cu)/%[Cu] or L(m/s) = %[Cu]/%(Cu) However, this simple approach ignores the dynamics of the smelting process. It overlooks the effect of the chemical work done in producing a given matte grade from concentrates of different grades -- or from a single concentrate blended with varying quantities of copper bearing precipitates or reverts. This paper examines the combined influences of matte grade and the work done in smelting on the copper content of smelting furnace slags. A simple model for the relationship is proposed.

Jan 1, 1999

By Dianyuan Dang, Guihong Han, Wenjuan Wang, Tao Jiang, Yanfang Huang

In this study reduction kinetics and swelling behaviors in "two-step process” were investigated by weight-loss technique and visualizing physical changes of pellet. Results showed that reduction degree (r) increased with increasing temperature and time. According to the dynamic calculation, when reduction temperature was lower than 1000°C the reduction process was controlled by chemical reaction with apparent activation energy of 72.27 kJ/mol. When reduction temperature was higher than 1000 , the equation of t/[1-(1-r)1/3] against [1+2(1-r)-3(1-r)2/3]/[1-(1-r)1/3] followed straight lines, demonstrating that reduction was mixed-controlled. Swelling experiments indicated that the maximum swelling index increased with the increase of reduction temperature and CO content.

Jan 1, 2016

By S. B. Bortnikova

This paper presents the results of an investigation of the gold-silver oxidized ores at the Salair mine. West Siberia. High losses of precious metals during primary ore processing are the result of outdated technology that is not suited to treat the present ore compositions. The main mineralogical forms of gold and silver and their confinement to different grain size fractions have been determined. About 50% of gold in the slime fraction and 60% of the silver in the form of acanthite that are scattered from the secondary minerals are lost to the waste. The results of these investigations have provided the basis for the recommendation of a new technological process to upgrade the current practice of the gold extraction plant and for methods to reprocess the concentrates.

Jan 1, 1995

By Xirneng Zhu

The electrochemical behavior of Pittsburgh and Illinois coal pyrite in basic and neutral borate/sulfate solutions was investigated. In the transpassive region, aggressive oxidation of pyrite occurred. The reaction products in this region were Fe(III) oxide, sulfate ion and partially oxidized sulfur intermediates. The formation of sulfur and polysulfides was identified by in-situ Raman spectroscopy. The growth kinetics of the reaction product film, resulting from transpassive oxidation of coal pyrites, were studied using chronoamperometry measurement with both stationary and rotating disk electrodes. The reaction rate was well correlated by a paralinear rate equation. The effects of electrode rotation speed, solution pH and temperature were examined. The kinetics were compared to those for mineral pyrite.

Jan 1, 1994

By Pinakin C. Chaubal

Today?s steel industry is in a vibrant and resurgent mode. This transformation has been in the making for some time now. Over the last few decades, the industry was steadily transforming itself into becoming a high tech industry. New technology was adopted, efficiencies were enhanced, lean manufacturing concepts were brought in and a strong customer focus was developed. Today?s mills employ sophisticated instrumentation, computerized monitoring, on-line smart systems etc. driving processes that are producing at rates of many tons/minute. All this is not possible without judiciously using the latest available technologies in various fields and developing a more sophisticated work force. Prof. Sohn has been a pioneer in driving the concept of process engineering in process metallurgy. In this paper the focus is on some aspects of process engineering ? primarily process modeling - as applied to iron and steelmaking processes. Examples are shown to demonstrate how problems have been addressed. Some thoughts on future directions are presented.

Jan 1, 2006

By Pinakin C. Chaubal

Today?s steel industry is in a vibrant and resurgent mode. This transformation has been in the making for some time now. Over the last few decades, the industry was steadily transforming itself into becoming a high tech industry. New technology was adopted, efficiencies were enhanced, lean manufacturing concepts were brought in and a strong customer focus was developed. Today?s mills employ sophisticated instrumentation, computerized monitoring, on-line smart systems etc. driving processes that are producing at rates of many tons/minute. All this is not possible without judiciously using the latest available technologies in various fields and developing a more sophisticated work force. Prof. Sohn has been a pioneer in driving the concept of process engineering in process metallurgy. In this paper the focus is on some aspects of process engineering ? primarily process modeling - as applied to iron and steelmaking processes. Examples are shown to demonstrate how problems have been addressed. Some thoughts on future directions are presented.

Jan 1, 2006

By Suzzann Nordwick

Over the past decade, significant advances have been made in the development of sulfate-reducing bacteria (SRB) technology to treat acid mine drainage (AMD). Bench-scale testing, field demonstrations, and engineered applications of SRBs for the treatment of AMD will be presented. Designs include an in situ bioreactor installed in the subsurface workings of the Lilly Orphan Boy Mine in 1994, the SRB bioreactors installed at the Calliope Mine from 1998 to 2001, the integrated biological reactors built at the Surething Mine in 2001, and the ongoing development of a replaceable cartridge system. SRB technology benefits include the reduction of dissolved metal ions to insoluble metal sulfides and the neutralization of the AMD resulting from the production of bicarbonate from the oxidation of organic nutrients. This paper will address engineering design criteria including the selection of organic media and system permeability and complete mitigation of AMD. Research was funded under Interagency Agreement No. DW899388-70-01-1 between the US EPA and the US DOE and was conducted by MSE Technology Applications, Inc., through the National Environmental Technology Laboratory (DOE Contract No. DE-AC22-96EW96405) at the Western Environmental Technology Office located in Butte, Montana.

Jan 1, 2003

By René Bustamante

The subject of this paper is a comparative evaluation of different copper smelting gas cooling techniques, using "productivity and quality" criteria. The first section presents a brief description of the operation of the radiant and the evaporative cooling systems, focusing on the differences between each other, in particular regarding. a) mass and energy balances; b) gas flow, temperature and composition; c) dust concentration and recovery. This section includes a brief discussion of the "client-server chain", i.e. the links between the cooling equipment and the down-and up-stream operations. More in particular, the up-stream server relationship impacts on the operating stability of the furnace, and in turn on furnace down-time and Cu production losses; and the down-stream client relationship affects the operation of the electrostatic precipitators, in terms of workload and cost of handling larger quantities of dust of a given dust size The second section deals with the development of indexes to measure and compare value added through the "utilization, productivity and quality" that can be expected of both cooling methods at the physical and economic levels, and the impact on the overall smelter productivity and the final cost composition of copper. The final section presents the results and includes a discussion of the comparative advantages and disadvantages of both cooling systems.

Jan 1, 1999