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By Rina Kim

The addition of lead to a gold leaching reactor can effectively accelerate or retard the gold cyanidation reaction. This study explored the effect of lead on the gold dissolution kinetics using cyclic voltammetry (CV) experiments. It was illustrated that the gold leaching kinetics in the cyanide solution enhanced with the addition of lead salt in the low overpotential region (–0.35 V vs. Ag/AgCl). The similar behavior was observed in the presence of ore containing 0.25% galena. In contrast, the gold oxidation kinetics retarded at –0.35 V (vs. Ag/AgCl) in the presence of silicate and lead-bearing mineral under certain conditions. Likewise, the lead addition was not functional for the high sulfur ore. This was attributed to the oxidation of the sulfides to the elemental sulfur, which subsequently formed a passivating layer on the gold surface. The results were evidently affirmed by the electrochemical tests and X-ray photoelectron spectroscopy (XPS) analysis.

By Satoshi Itoh

Phase equilibria and activities of the components in the liquid lead-antimony-oxygen ternary system, which is of fundamental importance for discussing the' recovery of lead and antimony from a used lead-battery, have been investigated at 1173 and 1223 K. The two liquid phases of metal and oxide were observed at the temperatures studied, and the tie lines indicating isoactivities were determined. The activities of PbO, SbO1.5 and Sb2O3) in the PbO-SbO1.5 and PbO-Sb2O3 pseudo-binary systems were then obtained by applying the Gibbs-Duhem equation to the phase relation of metal-oxide equilibrium. Both in the pseudo-binary systems the activities exhibit negative deviations from Raoult's law. The vapor pressures of lead, antimony and lead oxide, antimony oxide were calculated by using the activities of the components in the lead-antimony-oxygen ternary system. As a result, an oxidation of antimony concentrated in an anode slime followed by evaporation as antimony oxide Sb406 was found to be considerably effective for the recovery of lead and antimony from a used lead-battery.

Jan 1, 2003

By C. Koopman

During the production of phosphoric acid from phosphate ore and sulfuric acid, large amounts of calcium sulfate are formed, in which impurities from the feedstock are incorporated. To use the calcium sulfate in, for example, the building industry, a lower concentration of impurities is desired. Mercury, copper, lead, and cadmium were extracted from clear industrial recrystallization acid (0.8-3.9 mol/kg H3PO4, 0.2-0:5 mol/kg H2SO4) by supported solvent extraction with the extracting agent Cyanex 302 in kerosene in a transverse flow hollow fiber module. The permeability for the mercury ion was 1.4.10-6 m/s, whereas that for the copper ion was calculated to be 1.5.10 m/s. Cadmium, lead, and copper were extracted during the recrystallization of calcium sulfate hemihydrate to dihydrate, an existing step within the ,phosphoric acid production process, by solvent extraction with the same extracting agent. The concentrations of cadmium and zinc in the newly formed calcium sulfate were proven to be decreased. Unfortunately, concentrations of mercury and lead were too low for analysis.

Jan 1, 1999

By Jukka S. Sulanto

Outokumpu has applied its well -known copper Fl ash Smelling Process also for smelting su1phide lead . concentrates. The lead in the Flash Smelting Furnace slag is recovered by reducing the oxygen potential of the slag in an electric furnace by injecting reductant into the slag bath. A series of tests have been carried out in a 1000 KVA electric furnace? adjacent to a pilot Flash Smelting Furnace. The furnace has been fed continuously with molten Flash Furnace Slag. The feed rate has varied from 0.5 to 3.1 MTPH (0.55 - 3..4 STPH) depending on the feed rate and the quality of concentrate to the Flash Smelting Furnace. The inlet slag contained 15 to 40% of lead and the cleaned slag 1. 5 to 3. 0%. The lead recovery from sol id raw material was tested in the same continuous process by feeding lead calcine into the furnace. Feed rate was 0.7 to 0.95 MTPH (0.8 - 1.05 STPH) and the calcine contained 33 to 34% of Pb. Several reduction agents and procedures were tested. The process proved to be suitable for continuous recovery of lead from solid oxide raw materials.

Jan 1, 1990

By Rui-Qing Li, John G. Peacey, Peter J. Hancock

"Noranda has been investigating a pyrometallurgical process for the direct recovery of zinc from zinc concentrate and zinc and iron containing residues. The process consists of injecting dry zinc concentrate and secondary zinc materials into a molten iron oxysulphide bath, volatilizing metallic zinc into furnace off gas essentially free of sulphur or S02, fixing sulphur contained in the feed materials as iron oxysulphide matte which is disposed, and recovering metallic zinc in an ISP type lead splash condenser. Combustion of petroleum coke with air or oxygen enriched air inside the oxygen containing matte supplies part of the heat, and the products of combustion dilute the zinc-laden gas to a desired level.This paper describes the process concept, thermodynamic background, experimental tests, mass and heat balance calculation for a conceptual flowsheet, environmental stability of the residue and advantages and disadvantages of the process. Experimental tests have successfully proved the process concept and thermodynamic predictions. Direct smelting of zinc concentrate and residues inside an iron oxysulfide bath has a great potential to become a cost effective and flexible zinc smelting process.1. INTRODUCTIONZinc is mainly produced by a roast-leach-electrowinning process route, which accounts for about 80% of the world primary zinc production. This process produces high quality zinc with very high zinc recovery (>95%) but suffers from several major drawbacks such as using high cost electricity as reductant, producing environmentally problematic iron containing leach residue (jarosite or goethite) and the difficulty in treating secondary zinc feed materials containing high impurity levels, such as electric arc furnace dusts from the steel industry, and other complex sources. Also in some areas, markets for sulphuric acid are distant resulting in negative realizations on acid sales.The Imperial Smelting Furnace (ISF) process is the major pyrometallurgical process to treat zinc-lead concentrate. The advantage of this process over the electrolytic zinc process is its flexibility in treating high-lead, bulk concentrates with high recoveries of lead, copper and precious metals. However, this is a two-stage process involving sintering of Zn-Pb concentrates followed by blast furnace reduction. The process requires large amounts of high-quality coke which is a major operation cost, and the sintering process which results in serious environmental problems."

Jan 1, 1996

By A. Rosenfeld

The feasibility of applying laser induced optical emission spectroscopy to the high speed sorting of mixed alloy aluminum scrap is investigated. The basic spectroscopy for analysing aluminum alloys for the major alloying elements over their full concentration ranges is established. Materials handling issues are also described and the components of an overall sorting system are presented.

Jan 1, 1995

By Duclerc Fernandes Parra, Luis Filipe Carvalho Pedroso Lima, Harumi Otaguro, Washington Luiz Oliani, Hélio Fernando Rodrigues Ferreto, Ademar Benevolo Lugao

The activation of three polyethylenes, the low density, the high density and the linear low density polyethylene, was determined by means of dynamic mechanical analysis (DMA). Storage modulus and tan δ spectra were obtained as a function of the temperature from −60 to 50 °C with a heating rate of 2° min−1 at frequencies of 1, 2 and 5 Hz and measurement strain amplitude of 10−5. In the tan δ spectra, a small peak in the β region of the three polyethylenes was found and substantiated by subtracting the growing exponential background. This procedure was based on a model that associates the dislocation motion on metals under cyclic stress to vibrating strings and considering the same for the polymeric chains. For the determination of the activation energy we have utilized the frequency versus the reciprocal of the absolute temperature peak of the tan δ. The values obtained for the three polyethylenes, the low density, the high density and the linear low density were, 362 ± 12, 266 ± 9 and 197 ± 6 kJ mol−1, respectively, which were compared with those presented in the literature.

Mar 1, 2017

By George Kachaniwsky

Until mid-1982 the Mines Gaspe copper smelter consisted of a fluid bed roaster, a reverberatory furnace, two Peirce-Smith converters of which only one was blowing at any one time, anode casting facilities, and a single contact sulphuric acid plant treating both roaster and converter gases. Reduced concentrate supplies have led to the shutdown of the roaster and, as a result, it was necessary to adapt the converter and acid plant operation to the new operating mode: green concentrate smelting with resulting lower matte grades and acid plant treatment of off-gases from only one blowing converter. Therefore, modifications were carried out to existing equipment and methods of operation and control. This paper describes the result of work done to obtain steady, maximum strength, converter off-gas flow and an efficient acid plant operation. Topics covered include: optimization of converter operation, tightness of hood and off-gas ducting, improvements in acid plant/converter communications and modifications of acid plant operation and control to cope with the fluctuations in converter gas flowrates and strengths.

Jan 1, 1983

By Seyed Mohammad Taghavi

In this report, the efficacy of different factors such as temperature of reaction, time of reaction and depth of bed are investigated in a process of recovery of zinc oxide from zinc ore concentration residues in a fluidized bed furnace. Under optimum conditions, there was more than 93.5% zinc oxide in products.

Jan 1, 2006

By S. K. Kawatra

A growing concern for pyrometallurgical operations is the generation of airborne particulates. These particulates can be generated by combustion processes, or by materials handling. Regulation of these particles by the EPA has become progressively more stringent, first for particulates finer than 10 micrometers (PM10), which are particles fine enough to be inhaled into the lungs. Then, restrictions were introduced on emissions of particles finer than 2.5 micrometers (PM2.5), which are fine enough to become embedded in lung tissues. The next stage of regulations is likely to be ?nanoparticulates,? particles finer than 100 nanometers, which are in a size range where their very high surface area leads to enhanced reactivity. While all of the health effects due to nanoparticulates have not yet been determined, there have been enough studies to indicate that there is a problem, and restrictions on nanoparticulate emissions are only a matter of time. In this paper, it will be demonstrated that dry handling, comminution, and combustion sources represent a significant concern for both PM and nanoparticulate emissions. In regards to dry handling, the effects of utilizing effective dust suppressants on PM and nanoparticulate emissions will be explored.

Jan 1, 2006

By Li Fangi

This paper describes the characteristics and regularities of a process to recover rare earth minerals from Baotou Ore with H-205 collector. H-205 is a kind of hydroxamic acid with amide as a polar group and poly-cycle aromatic hydrocarbon as a non-polar group, having strong ability to capture RE minerals (bastnasite, monazite). When adding a certain dosage of water glass and some other modifying agents, and maintaining pH value between 8.5 and 9.5, RE minerals can be effectively separated from calcium and barium minerals, such as fluorite and barite, etc. Under normal flotation temperature and concentration, when using H-205 to float RE minerals, it needs a bit longer conditioning time (a few minutes longer than that for the conventional collectors). It is also shown that the reagent has the property of resistance to hard water. The laboratory scale and pilot scale tests of the process have been carried out on bulk froth containing RE minerals and fluorite taken from Ore Dressing Plant of Baotou Iron and Steel Company, in both cases, high grade RE concentrates were obtained and the recovery increased remarkably. Therefore, the process has a great practical value.

Jan 1, 1989

By Alexandre Monteiro

Alumina precursor powders can be precipitated from aqueous solutions, using hydrothermal decomposition of urea to deliver base homogeneously to the system. Primary particles agglomerate early in the process, generating a wide size distribution. The presence of a polymeric surfactant such as polyacrylate can suppress or delay agglomeration, reducing particle size and narrowing the size distribution. The stabilization of commercially available a-Alp03 powder with polyacrylate was studied, investigating the effects of polyacrylate molecular weight, ionic strength and temperature. The effect of aluminum concentration, polyacrylate molecular weight and urea concentration on the precipitation of alumina precursors in a sulfate- urea system in the presence of polyacrylate/polyacrylic acid was then studied. The hydrolysis kinetics were followed, and particle sizes were determined. Precipitates were further characterized using energy dispersive spectroscopy. The particle characteristics are discussed in terms of the process conditions.

Jan 1, 1994

By Sung Wng Kim

The binary antimonide compounds with the skutterudite structure have a potential for thermoelectric applications because of the high carrier mobility, high thermoelectric power, and relatively low thermal conductivity due to the complex crystal structure. However, the room temperature thermal conductivity of these skutterudite materials is as high as about IOW/mK with an estimated 80-90% contribution from the lattice thermal conductivity. Because the lattice thermal conductivity of related ternary skutterudite compounds can be substantially reduced due to the additional phonon scattering, a study of thermoelectric properties of these compounds is of interest. The binary IrSb3, ternary Ir1.xRuxSb3 and Ir(MxSb1.x)3(M=Ge, Sn) compounds were prepared by hot pressing of pre-reacted powders. We have measured the electrical resistivity, thermoelectric power, and thermal conductivity, in a temperature range from room temperature to 973K. The binary IrSb3 compound is found to have P-type electrical properties exhibiting a good Seebeck coefficient (up to 225µV/K around 773K), electrical resistivity(5x10-5Ohm M around 933K), and relatively low thermal conductivity(6W/mK around 950K). The lattice thermal conductivity, K[2] was calculated from the Wiedemann-Franz relationship.

Jan 1, 2002

By P. A. Davidson

"We discuss the influence of a static magnetic field on jets, vortices and turbulence. This is particularly relevant to D.C. braking in slab casting. Our main conclusion is that, typically, the magnetic field destroys mechanical energy, via joule dissipation, but is unable to destroy momentum. Rather, it continually rearranges the momentum in such a way that the energy falls.IntroductionIt is well-known that a static magnetic field can suppress motion of a liquid metal. That is to say, movement of the liquid across the magnetic field lines induces a current. This leads to Joule dissipation and the resultant rise in thermal energy is accompanied by a corresponding fall in kinetic energy.This phenomenon has been exploited in a range of metallurgical processes. For example, in the continuous casting of large steel slabs, an intense, static magnetic field is commonly used to suppress motion within the mould. The objective is to keep the free surface of the liquid quiescent, thus avoiding the entrainment of surface debris. In other solidification processes, such as techniques for growing semi-conductor crystals, it is widely believed that natural convection has a detrimental effect on the metallurgical structure of the solid. Again, the imposition of a static magnetic field is seen as one means of suppressing these unwanted motions. Finally, magnetic damping is used in the laboratory measurements of chemical and thermal diffusivities, particularly where solutal or thermal buoyancy can disrupt the measurement technique.In this paper we shall look at the damping of jets, vortices and turbulence. Our aim is to present a unified theoretical framework from which the many published studies may be viewed."

Jan 1, 1999

By Zdzislaw Miczkowski

At KGHM Polska Miedz S.A, a direct flash smelting process is used for smelting of chalcocite concentrate for the production of blister copper. The paper presents a model of complex oxidation process of single concentrate grains smelted at KGHM. The description covers main chemical reactions, phenomena of heat and mass exchange inside the grains and between a grain and the surrounding space. In the model, two zones describing the course of process inside the grain were distinguished: ? The first one, which moves faster towards the centre of a grain, both organic and carbonate carbon are freed, The process takes place without the presence of oxygen and results in an increase of the temperature in the core of the particle. ?The second zone moves slower into the grain and the rate of the movement is determined by the presence of oxygen, In that zone the sulphur is eliminated and the oxidation of the organic compounds vapours moving from deeper layers of a grain takes place. Based on the results of laboratory tests, the coefficients that describe the oxygen transportation into the grain and decide the progress in the chemical reaction were determined, The paper contains the results of model calculations for single grains reacting in environment of various content of oxygen as well as the results of model calculations for the laboratory reactor system.

Jan 1, 2003

By Satu Strömberg

A single-particle laminar-flow technique was used to study oxidation of two nickel concentrates and a granulated nickel matte (43 wt% of Ni). Experimental conditions were: reaction gas from N2 to N2 + 75 vol% O2; gas preheating temperatures ranging from 500 to 1100°C. The major nickel-bearing minerals in the two concentrates were pentlandite and violarite, respectively. Chemical analysis of the particles was used to determine the oxidation degree of the materials, and optical and scanning electron microscopy were used to detect their morphology and mineralogy. Total desulfurization of the nickel concentrates was achieved under the most oxidizing conditions, while the sulfur removal from the nickel matte was not as efficient, especially with the coarse size fraction. Pentlandite-based concentrate was found to be less reactive than the violarite-based.

Jan 1, 1995

By Thomas J. Keefe, O&apos

The effects of cobalt, B-naphthol, glue and antimony on the polarization behavior of zinc sulfate electrolyte were investigated. It was found that B-naphthol was beneficial in reducing the detrimental effects of cobalt while antimony and excess glue were each harmful. Since the nu cl eat ion over potential was insensiti1ve to coba1t, other regions of the polarization curve were used to indicate electrolyte balance. The low? current density area occurring in the reverse or anodic sweep direction was? often an indicator when an ?unstable condition existed. The two parameters evaluated were the degree of inflection in the polarization curve in the low current density region during scanning and the rate of current rise observed when the sample was potentiostated at -0.781 Volts (SHE). Using this technique, a two-additive system was shown to be desirable to control cobalt and antimony containing electrolytes. The structure of the deposits was examined using scanning electron microscope techniques.

Jan 1, 1985

By W. H. (Bill) Jay

The destruction of cyanide creates a significant impost on the financial returns of gold mines. These losses increase substantially when ores containing cyanide-soluble copper are treated. Failure to remove or destroy free or WAD cyanide before it is discharged into tailings dams has, on a number of occasions, led to significant fish, bird and animal deaths. Thus, the retention of cyanide within the leach circuit and the recovery or removal of stable metal cyanide complexes needs to become standard practice for all gold mining operations. Furthermore, reducing cyanide purchases will minimise the quantity of cyanide transported to the mine site thereby reducing the opportunity for spillage of this chemical. Many different physical and chemical methods have been investigated for the removal of cyanide from process solutions. All cyanide destruction methods create a financial impost on the economic viability of the gold mine. To reduce these costs, the recycle of cyanide and the economic recovery of the metals solubilised by cyanide is of prime importance. The alternative methods currently in use, or under consideration for the treatment of copper cyanide, entail high reagent costs, produce the recovered metal in a contaminated form and require the safe handling of hydrogen cyanide. These processes will be briefly discussed within this report Environmental and financial benefits are enhanced by recent laboratory and pilot plant studies conducted by Oretek Limited. The Oretek CPC process for the recovery of copper and the recycle of cyanide from copper cyanide-containing solutions does not require pH adjustment to the alkaline cyanide leach conditions. Copper ions are coordinated to a water-soluble and/or an organic soluble polychelating agent under alkaline conditions and the cyanide ions are displaced Membrane separation, or phase separation of the polychelated copper from the cyanide ions enables the cyanide ions to be recycled and the copper to be directly electrowon from the polychelating polymer. The polychelating polymer is then recycled. Ion exchange resins and solvent extraction systems which may be incorporated into the above process will also be discussed in detail.

Jan 1, 1998

By J. Boltano

This paper discusses the study, design and implementation of the new gas handling system for the Caletones Smelter of Codelco-Chile. A discussion on design conditions for a future Sulphuric Acid Plant using Teniente Converter gases is also included. The old system which started to be modified in 1985 and relied on natural draft and used balloon flues, resulted in a limited gas handling capacity for operation under future process conditions. This system also caused excessive fugitive gases in the smelter working areas. The new system permits handling of process gases from the higher capacity Teniente Converters Installed in 1987-1989 improving the gas handling of the reverberatory furnaces and Peirce-Smith converters as well as the environmental conditions of the smelter. This system utilises improved converter gas hoods, evaporative cooling and electrostatic precipitators gas cleaning, and is based on natural draft.

Jan 1, 1992

By Kandipati Sreenivasarao

A promising method for removing heavy metal ions from dilute effluents is ion- or precipitate- flotation, in which a suitable collector is added to form hydrophobic metal-collector complexes or compounds that can be collected as foams. We have successfully removed Cu(II), Cd(II), and Pb(ll) from dilute solutions using sodium dodecylsulfate and ethanol as collector and frother respectively. However the process would not be economically viable unless the collector could be recycled, and the heavy metals recovered in a concentrated, preferably marketable, form from the foams. We investigated four different methods to decompose heavy metal-dodecylsulfate complexes, namely precipitation of hydroxides, precipitation of sulfides, chemical stripping, and electrolysis. We compare the performance of these methods. In each case the observed behavior is related to known thermodynamic data, and potential applications are discussed.

Jan 1, 1995