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By C. A. Nogueira, F. Margarido

"A research work has being carried out annmg at evaluating the possibility of treating simultaneously several electrochemical systems of spent batteries using the same process, in order to overcome the high costs and difficulties of selective collection and sorting. Zn-Mn02 systems, representing more than 75% of portable battery market, shall be treated in dedicated processes. The treatment assessment using a single hydrometallurgical process of the other major systems (NiCd, NiMH and Li-ion), having Ni and Co as main metals, was the aim of the research work here reported. Sulfuric acid leaching was demonstrated to be adequate for dissolving more than 90% of the metals of interest contained in batteries. The subsequent separation of metals by solvent extraction, using organophosphorous extractants like DEHPA and Cyanex 272, allowed the production of pure solutions of rare earths, cadmium/manganese, cobalt, nickel and lithium, enabling their further recovering.IntroductionRecycling is the best approach for end-of-life management of spent batteries mainly by environmental reasons but also motivated by resources conservation and, in some cases, by economic profits. Most relevant electrochemical systems of portable cells are Zn-Mn02 (ZMB, alkaline and saline), nickel-cadmium (NiCd), nickel-metal hydride (NiMH) and lithium-ion (LIB). These batteries are collected, sorted and usually treated separately, applying for pyrometallurgical or hydrometallurgical technologies, the former being the most common.Several processes have been developed and some of them industrially applied, as described in some available review papers [l, 2]. In Europe for ZMB systems the oldest processes are Batrec [3] and Citron [4]. Although having differences in details, both are based on pyrometallurgical recovery of zinc by distillation, in metallic or oxide forms, being manganese retained in the slag together with iron. Hydrometallurgical alternatives are also available, like Zincex [5] and Recupyl [ 6] processes, both using sulfuric acid solutions as leachant. The application of the existing technologies to battery recycling, instead of using dedicated processes, is other alternative already tested, being the Waeltz furnace or the Imperial Smelting some examples."

Jan 1, 2012

By R. Nilsson

In the present work, an assessment of the sulphide capacities of a number of binary and ternary slag systems have been carried out in the light of a sulphide capacity model. The model is based on the expression: {CS- exp (-A G °/R T) ? ao2 / fs2-} where AGO is the standard Gibbs energy change for the above reaction, ao2 is the activity of oxygen ions and f, is the activity coefficient of the sulphide ion in the slag. In the present model, the ratio (ao2/fs2) is optimized for the experimental data available in literature. The systems assessed are the binaries MnO-SiO2, CaO-SiO2, Al2O3-CaO, as well as the ternaries CaO-Al2O3-SiO2 and CaO-MnO-SiO2. In the case of all these systems, the experimental data available in literature were complemented by measurements carried out at the Division of Theoretical Metallurgy. The sulphide capacities of some FeO- containing binary, ternary and quaternary slags are also examined. The potentiality of the model to estimate the sulphide capacities of complex slag systems from binary and ternary data is demonstrated.

Jan 1, 1996

By Vaughan R. Voller

"Numerical methods for dealing with a temperature dependent conductivity are discussed. An approach based on a local application of a Kirchhoff transformation at the discrete level is presented. The application of this transformation - that does not require any inversion- is demonstrated on solving a two-dimensional test problem.IntroductionMuch is said in the recent literature on the modeling necessity of obtaining appropriate thermo-physical properties; in particular the requirement to account for properties that are ""strong"" functions of the depended variables, e.g., Temperature. Of course obtaining appropriate thermo-physical properties serves no purpose unless they can be accurately integrated into a discrete numerical calculation. The purpose of this paper is to examine how temperature dependent conductivities that exhibit discontinuities or rapid changes can be handled in a numerical code.The discussion will be made in the context of a control volume finite element method [1]. After a brief outline of control volume finite element fundamentals basic methods of dealing with discontinuous or rapidly changing thermal conductivity are discussed. This is followed by the presentation of the recently proposed local Kirchhoff method [2,3], The paper concludes with an investigation of the performance of the various conductivity schemes in solving two dimensional problems. This testing clearly shows the advantages (accuracy and implementation) in using the local Kirchhoff method."

Jan 1, 2001

Primary sulphidic gold ores in the Archean provinces of Western Australia can be broadly sub-divided into pyritic, pyrite-telluride, arsenical and antimonial types. Pyritic ores contain only native gold, and are essentially not refractory. Arsenical ores almost always carry some invisible gold, and may vary from mildly to highly refractory. Pyrite-telluride ores contain gold-bearing tellurides, and are refractory to varying degrees. Antimonial ores usually contain aurostibite, and may be very difficult to process. A classification scheme for metallurgical processing, based on mineralogy, is proposed for the ores, and implications for processing are discussed.

Jan 1, 1995

By J. Rastas

The recovery of lead, silver and gold from existing and potential zinc process residues using a sulfidization-flotation method was investigated on a laboratory scale. The following residues were tested: neutral leach residue, high acid leach residue, and hematite residues. The sulfidization of lead and silver is carried out at low pH by the addition of a stoichiometric amount of sulfide at a controlled rate. To increase the particle size of the sulfides, seeding with synthetic lead and silver sulfides -is employed. The flotation is carried out at pH 2-4 using low pH-collectors such as dithiophosphates and dithiophosphinates. Special attention must be paid to the role of oxygen in the conditioning stage. The effect of different parameters on both the sulfidization and the flotation has been evaluated. Recoveries of 85-90, 90-95 and about 80 % were obtained for lead, silver and gold, respectively. Typically, concentrates containing 50-60 % lead, 3-5 kg/t silver and 10-15 git gold were produced.

Jan 1, 1990

By V. A. Luganav

The behavior of arsenopyrite under heating has been studied by many scientists. It has been already established that under heating at more than 650°c and without air access the arsenopyrite dissociates with the formation of one atom arsenic. Under vacuum the dissociation process begins at 5500C with the formation of elemental arsenic. The residue of dissociation process contains pyrrhotite and throilite. In the presence of pyrite, arsenopyrite dissociates under lower temperature and with a higher velocity than without it. The industrial realization of fool scale processing of arsenic bearing raw materials is possible only by the use of standard equipment and oxygen containing blast. In this view the paper presents the results of the study on the effect of oxygen in the gaseous phase and its addition into the charge of pyrite in the process of arsenopyrite decomposition. Thermodynamic analyses showed that under thermal processing of arsenopyrite in the presence of pyrite and limited quantities of oxygen in the gaseous phase the formation of arsenic sulfides is possible according to the following reactions:

Jan 1, 2003

By Eric J. Beckman

Recovery of metals from dilute solution, whether the matrix is solid, or liquid, remains a considerable technical and financial challenge. Methods currently exist whereby metals can be extracted from either type of matrix, yet these methods consume significant quantities of reagents and can also generate multiple waste ,streams in the process. Technology developed in our lab allows efficient application of environmentally-benign CO2 to a number of separation problems involving metals. For example, we have employed biphasic mixtures of C02 and water as a green acid leach medium. Metals have been extracted from a steelmaking process residue and then recovered as metal carbonates through depressurization. In this process, metals are extracted and recovered without the use of reagents other than CO2 and water, and CO2 is sequestered as a solid. In addition, through synthesis of Cal-miscible phase transfer agents, we have shown that CO2 can replace the organic solvent currently used in refining of precious metals, The sensitivity to pressure of phase behavior in a CO2-mixture may allow significant streamlining of the process as well. Finally, CO2 soluble chelating agents have been used to extract toxic metals from acidic effluent such as that found in plating facilities.

Jan 1, 1999

Several processes are now available for the recovery of free and WAD cyanide from gold plant solutions and pulps. In the past, the incentive for evaluating cyanide recovery in gold plant flowsheets has been economic. In many cases, it has been possible to demonstrate (at least in the laboratory and on paper), an improvement in process economics by; (i) reducing the costs of tailings detoxification, (ii) recycling cyanide at lower cost than the purchase/delivery price of new cyanide, and (iii) generating additional revenue via by¬product sales. Despite these convincing arguments, few cyanide recovery plants have been built at operating gold mines. Also, there is arguably an even more compelling reason for mining companies to consider cyanide recycling. With the growing storm of negative public opinion that the use of cyanide in the mining industry is attracting - following several highly publicized spills over the last couple of years - the time has come for the gold industry to demonstrate environmental diligence and stewardship in the use of this commodity that is so vital for their industry. There is no doubt that the widespread implementation of cyanide recycling will reduce the impact of the cyanidation process on the environment, both by reducing the risk of spills (with less cyanide being transported from manufacturing plants to gold mines), and by reducing the loading of toxic and non-toxic metals and ions in the tailings. In this paper, the various processes that are available for cyanide recovery are discussed, along with the process chemistry. Results of several laboratory and pilot plant trials that have been conducted over the last few years are also presented.

Jan 1, 1998

By Zhao Guangwen, Wu Tan, Qiuzhan Tian, Duan Shuzhen

"A thorough study of lost currents in bipolar cells has been made for the development of the great potential of bipolar cells in energy saving. A proper equivalent circuit for bipolar cells has been found, and mathematic methods for computing lost currents at all kinds of polarization have been developed.At linear polarization, the lost currents can be computed by solving either a tridiagonal matrix or an ordinary differential equation of second order. This kind of values can be used to evaluate the minimal lost currents at given conditions. At other kinds of polarization, the lost currents can be computed by the same methods as above if the necessary experiments of measuring the cell voltages of every electrolytic compartment have been made. This kind of values can be used to design bipolar cells at practical conditions.Extensive experiments have been made to evaluate the effects of electrode polarization, emf of galvanic cell for the formation of electrolyzed substance, gaseous products, geometric dimensions of electrolytic cells, special resistance of electrolyte used, and the total and ordinal number of electrolytic compartments on lost currents. It is the first time to make such a systematic research by experiments in the world. Experiments showed that theoretic models were in good agreement with measured data. Experiments also showed that D.C. energy consumption of 0.45 kwh/kg of Pb for lead electrolysis from molten chlorides could be achieved in a cell with 7 bipolar electrodes.IntroductionIt is very promising to apply bipolar electrolytic cells to electrolysis of aluminum, magnesium, lead, zinc and perchlorinates for their great potential of energy saving for example, bipolar cells had been used in the production of magnesium and saved more than 30% of energy, being one of the three main techniques of energy saving in the production of titanium sponge (1)."

Jan 1, 1988

By M Philip Schwarz

"This paper reviews the status of computational modelling of a variety of common metals reduction processes, namely the blast furnace, rotary kiln and fluidised bed, and one new process not yet commercialised, namely smelting-reduction as in the HIsmelt Process. In each case, the last decade has seen the emergence of the capability to simulate the processes using multi-phase reacting computational fluid dynamics techniques. In some cases this capability is still in the process of being developed, and the next few years will see the maturing of the modelling techniques. As they become established, it will be possible to apply them to further refine the older technologies such as blast furnaces and rotary kilns, and assist in the optimisation, commercialisation and acceptance of the newer technologies such as fluidised bed and molten bath reduction. The development of a computational fluid dynamic model of bath smelting-reduction is described in some detail to illustrate how a large number of complex and interacting phenomena can be successfully simulated within a CFD framework. IntroductionPyrometallurgical reduction processes, such as the iron blast furnace, have become increasing more sophisticated through the centuries, so that today they are often highly efficient. There are continuing pressures, however, to refine existing processes and develop new ones. The imperatives are often economic, given that the long-term trend in the price of metals is always downward. In recent times, there has been the additional need to improve the environmental impact of metal production. Given that they almost inevitably require the use of carbon, metal reduction processes are large sources of greenhouse gases, and even a relatively small improvement in efficiency can be valuable in reducing CO2 production. Local environmental issues, such as the need to control of particulate emissions, are also driving incremental improvements in equipment.In addition to the economic and environmental drivers mentioned above, new process development is also being driven by the need to process new ores, and the need to produce unrefined metal in a form more compatible with alternative routes for downstream processing. An example of the latter is the production of DR! (Direct Reduced Iron) as a feed for EAF Electric Arc Furnace) in mini-mills.Further improvement of processes that have already been honed by continual plant experimentation over many years is not an easy task. To deliver further gains in efficiency, throughput, or product quality requires a highly sophisticated tool: one such tool· is computational modelling."

Jan 1, 2001

By S. Mondon

Hibi Smelter which is a Copper Smelter lining a blast furnace, produces 2,700 metric tons of anode copper per month. Generally, in a copper refinery, arsenic and antimony are considerably troublesome impurities. With regard to the elimination of antimony, Hibi Smelter has two handicaps described as follows. (1) Smelting under the slightly oxidizing atmosphere in the blast furnace. (2) Recycling the converter slag to the blast furnace after cooling. Therefore antimony and arsenic, mainly antimony, elimination tests, in which the alkaline flux was injected through the two tuyeres in the blowing stage, were carried out in the rotary anode furnace. Antimony and arsenic were respectively removed more than 90 96 from the molten copper, and their high eliminations are discussed by application of the transitory and permanent reaction model with the flux injection, which was presented by T. Lehner.

Jan 1, 1983

By Chuanfu Zhang, Liwei Liang, Yanxin Wu, Jinliang Wang

"According to the reaction shaft operation characteristics during the flash smelting process, 15 groups of slag samples containing high Fe3O4 were prepared by some chemical reagents, and then the slag viscosities were measured using a RTW-10 type synthetic test instrument for melt physical property by the rotating cylinder method. The effects of Fe/SiO2 ratio (mFe/mSiO2), Fe3O4 content (wFe3O4), Cu2o), MgO content (WMgO) and Cao content (wCaO) on the slag viscosity were also studied. Results show that slag viscosity is decreased with the increase of temperature, mFe/mSiO2, wCu2o, wMgO and wCao, and with the decrease of wFe3O4, under the range of slag contents: mFe/mSiO2 1.36~1.78, wFe3O4 17.83%~21.18%, wCu2o 3.51%~8.34%m wNgI 2.21%~6.57%m w/caI 6.22%~9.387% and temperature range if 1250 o/c~1450 oC. Only wFe3O4m and w/caO have great influence on the slag viscosity when temperatures as high as 1400 oC. Only wFe3O4 and wCaO have great influence on the slag viscosity when temperatures as high as 1400 oC or so. To form a freeze slag with higher viscosity inside the reaction shaft, wFe3O4 should be more than 20% and wCaO should be less then 6%.IntroductionSince its appearance in 1949, Outokumpu flash smelting technology has making continuous innovation and has become the most competitive intensified smelting technology [1], widely considered to be the standard clean smelting process [2]. At present, flash smelting technology is adopted to newly build or reconstruct most of the world's copper or nickel smelting enterprise [3]. Reaction shaft is the most important part of the flash smelting furnace. During the flash smelting process, reaction shaft must be able to withstand the following harsh conditions at the same time: 1) high temperature varying from 1400 °C to 1500 °C. 2) strong oxidative atmosphere containing 50% - 80% oxygen. 3) solid particles and melt with speed up to l00 m/s. 4) high acidic or basic slag with strong chemical corrosiveness. 5) smelting gas containing 50% - 80% SO2. 6) matte with strong dissolution."

Jan 1, 2012

By Bing Gao, Zhe Wang, Xiangdong Xing, Xueqi Zhang, Shan Ren, Jianliang Zhang

"In sintering, the flame front speed (bed permeability) and sinter qualities are greatly depended on the feed size, especially coke breeze and limestone particle size. It is well known that coke breeze provides sinter bed with heat to meet the demand of partial fusion and diffusion bonding while limestone reacts with iron ore to generate bonding phase in the sintering process. Accordingly, it is necessary to find the optimum combination of different particle size of coke breeze and limestone to yield sinter associated with better qualities. In this study, sinter was produced in the sinter pot with varying coke breeze and limestone particle size together in sintering of a coarse hematite iron ore. The sintering productivity was measured and all of the result sinters were examined by microstructure analysis and reduction degradation test (RDI test). For the sintering of a coarse hematite iron ore, it was found that the optimum mean particle size combination of coke breeze and limestone was 1. 71mm and 1.55mm in the sinter mix. On such a circumstance, sintering productivity was higher and the properties of sinter were better.IntroductionNowadays, as the main iron bearing burden material of modem blast furnaces, sinter has a great influence on the blast furnace operation. Sintering is a greatly complex process involving various chemical reactions to form kinds of mineral phases [1, 2]. In the sintering process, coke breeze is used for fuel and it generates heat to raise the green bed temperature. Limestone serves as flux and it reacts with iron ore to produce various mineral phases. On one hand, during the sintering process, the particle size of coke breeze can have an effect on temperature, atmosphere, the flame front speed and all of them act on the microstructure and mineral constitutions of sinter [3, 4]."

Jan 1, 2013

By D. J. Murdock

Cominco Ltd. has developed a number of innovative technologies for electrowinning. The paper discusses the application of these technologies to the copper industry. Tankhouse and cell design will be discussed in addition to anode cleaning and cathode handling. Specific examples of the application of this technology to the copper industry are cited.

Jan 1, 1987

By San-chuan Tang, Wen Chen, Shun-ming Ning, Kan-ping Yu, Qiang Zhao, Xue-yong Xing

"A new type of desilication agent (PA-2) was selected by experiment based on the analysis of the characters of silica gel, and the influence of desilication type, desilication dosage, pH value, temperature and aging time on the desilicating effect was studied. The test results showed that on the conditions that pH was 2.0, temperature was 20""C, aging time was12 hours and the dosage of desilication agent was 0.23%, the desilication rate was higher than 93% in solution.IntroductionVanadium is an important strategic resources, which applies to steel industry and petrochemical industry. The main materials for vanadium product are steelmaking vanadium slag, stone coal and containing vanadium waste catalyst, etc. And stone coal is a low-grade carbonaceous silicified vanadium resource, which is unique material for vanadium extraction in China. Meanwhile, our stone coal reserves is No.l throughout the world.The silica acid solution containing vanadium is produced by acid leaching of raw stone coal or its roasted ore. The silica content of this solution is mostly high, besides, when pH is higher than 2 , the solution is unstable. Furthermore, it is very easy to generate gel substance with the increasing of pH value and standing time. 'Ibis silica gel is composed of colloidal particles with the size in 0.001 - 0.1 um. As a result, it is very hard even impossible for the following operation of solution."

Jan 1, 2013

By Bryce Clark

Cobalts history from the 14th Century is outlined, with a look at its various sources over that period. The present sources and quantities are given, when in 1994 it is an equal co-product of copper in Africa and nickel elsewhere (Canada, Australia, Russia). Future trends in this scene are also examined. The final section deals with cobalts uses in superalloys, magnets, colours, electronics, chemicals, and examines trends in its markets. Supply and demand in co-product cobalt are shown, based on the latest production figures.

Jan 1, 1995

By Z. Yang, R. W. Smith, Jr. Wharton

"Microorganisms have the ability to remarkably adsorb and/or absorb heavy metal ions. Hence they are being studied widely as a means of removing metal ions from aqueous solutions both in order to clean up toxic streams and to recover valuable metals from these and other streams. It is often difficult to harvest organisms such as bacteria and unicellular algae since they are usually too small to be readily screened out. Froth flotation may prove to be a feasible method to harvest such organisms subsequent to the ad/absortion of the metal Ions. The present paper discusses the surface/electrokinetic properties of microorganisms and the modifier-collect conditions under which they should float. The zeta potential of the green alga Chlorella vulgaris was measured in the presence of AI(III) and Pb(II) ions and in the presence of dodecylammonium chloride and sodium dodecylsulfate. Present and past data suggest that the organisms should behave similarly to other finely divided, charged (polar) solids with their behavior sometimes modified by the non-polar surface regions present.IntroductionThe overall field of bioengineering is growing at a remarkably accelerating rate. Hydrometallurgy and mineral processing are included among those disciplines where there has been actual or proposed commercial use of bioorganisms. Further, the actual or proposed use includes bacterial enhancement of leaching of a number of different types of ores (1-5), modification of the flotation or oil agglomeration separation of minerals by bacteria (6,7) and microorganism (algae, bacteria or fungi) concentration of metal ions present in effluent or other mineral processing or hydrometallurgy aqueous streams (8-23)."

Jan 1, 1988

By Dong Joon Min, Joo Hyun Park, Mi Sun Choi, Jae Hong Shin

Sublimation of ZrCl4 is important for the production of nuclear grade metallic Zr in Kroll’s process. The sublimation kinetics of ZrCl4 was investigated by TGA under both isothermal and non-isothermal conditions. The sublimation rate of ZrCl4 increased with increasing temperature under isothermal conditions. ZrCl4 sublimation was confirmed to be a zero-order process under isothermal conditions, whereas it was first-order kinetics under non-isothermal conditions. The activation energy of ZrCl4 sublimation under isothermal conditions was 21.7 kJ/mol. The activation energy for non-isothermal sublimation was 101.4 kJ/mol and 108.1 kJ/mol with the Kissinger method and Flynn- Wall-Ozawa method, respectively. These non-isothermal activation energies were very close to the heat of sublimation (103.3 kJ/mol). Sublimation occurs by two elementary steps: surface reaction and desorption. Therefore, the overall activation energy of ZrCl4 sublimation is 104.8(±3.4) kJ/mol. The activation energy of the surface reaction and desorption steps are proposed to be 83.1 kJ/mol and 21.7 kJ/mol, respectively.

Jan 1, 2014

By M. Girgis

The behavior of arsenic III during electrolytic refining of copper in acidic copper ?sulphate electrolytes was studied by different electrochemical methods such as, linear potential sweep, cyclic voltammetry, chronoamperometry and chronopotentiometry. The study showed that arsenic behaves as a depolarizing ion and has a deleterious effect on copper deposit. Three substrates; Pb, Cu and Ag were used during the refining process and the electrode kinetics were found similar for both Cu and Pb electrodes while a little difference was found for the Ag electrode. A microscopic study by scanning electron microscope was undertaken to show the influence of arsenic on deposit's morphology. Surface analyses of the deposit were carried out by some electronspectroscopic techniques such as Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). The results showed that arsenic coexists with copper deposit at potential?~ -0.25 V.

Jan 1, 1987

By A. H. Castillejos E., F. A. Acosta G.

Filtration is widely used as a terminal refining step for metals, particularly for the casting of aluminum alloys, but still more knowledge is required to understand how several factors affect the efficiency of removal of inclusions. In this study, both, initial and long term filtration efficiencies of a ceramic foam filter have been obtained from the computed trajectories of solid particles suspended in molten aluminum. The complex structure of the foam filters is represented by a unit cell which is formed by a pair of pores with average dimensions. The fluid flow field was determined from the numerical solution of the Navier-Stokes equation, and periodic fully developed flow was assumed at the inlet of the calculation domain, as a boundary condition. This flow field corresponds to laminar flow as that found in ceramic filters operating under normal conditions. Computed initial filtration efficiencies showed that filtration efficiency decreases sharply with fluid velocity for particles larger than 30 µm, but smaller particles are better trapped at higher fluid velocities. Finally, it was found that long term filtration efficiency for particles of 8 µm decreased with time, in spite that perfect particle-wall attachment was assumed. Filter aging was considered in this study, and it was found that the distorted flow field, around the already trapped small inclusions prevented further collection.

Jan 1, 1999