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By C. A. Pickles

At the present time, pyrometallurgical processes are employed for the recovery of lead from battery scrap. These processes have serious pollution problems, primarily due to the emfssion of sulphur dioxide and airborne lead in the form of dust and fume. In addition it is necessary to dispose of solid wastes and liquid effluents which contain lead and in some cases sodium sulfide-containing compounds. In this work an improved process was investigated for the recovery of lead from battery residue. This involved pelletization of the residue with sodium carbonate and moisture. Then, the pellets were melted without carbon and the .sodium sulphate salt was removed. Subsequently, the molten lead oxide was reduced with carbon. This process minimizes the sulphur dioxide emissions and leads to very low sulfide contents of the sodium sulfate salt

Jan 1, 1992

By Paykan Safe

Computational Fluid Dynamic (CFD) modeling provides a powerful tool to assist with the design of ventilation and fume control systems in smelters and other high temperature metallurgical facilities. For this paper, this tool has been used to analyze the off-gas flow patterns exiting the mouth of a Peirce-Smith converter into a water-cooled hood and drop out box. The effects of various process and physical plant design parameters on process gas and fume capture and potential build up on the converter hoods was examined, and the optimum design and operating parameters were determined.

Jan 1, 2000

By L. Katgerman, R. Van Toi, H. E. A. Van den Akker

"Mould filling simulations are powerful tools for optimizing the characteristics of castings. The robustness of calculational methods for mould filling simulations is generally tested in simple geometries. While a vertical plate has been used often for validation studies, this paper aims at mould filling simulations of a horizontal thin wall casting. Such castings exhibit a strong interaction between heat transfer (solidification), surface tension and gravitational force.The results are presented of a study to validate numerical simulations of mould filling phenomena in a thin wall horizontal casting. Solidification during mould filling is studied computationally. Velocities are measured using Particle Image Velocimetry.INTRODUCTIONIn foundry practice Computational Fluid Dynamics (CFD) is being considered a promising tool to arrive at a better understanding of casting defects introduced during the mould filling period of a casting. The use of CFD is believed to be advantageous in predicting possible defect locations, pouring times, and the lowest possible casting temperature without the risk of cold shuts. In addition, CFD may be used to optimize pouring system geometries [1,2]. As opposed to experimental studies in, e.g., cold water models, CFD allows for the flexible modification of the casting geometry and the pouring system, and for the inclusion of physical effects such as solidification and heat transfer. Thus, a proper use of CFD may lead to a reduction of the casting rejection rate without expensive trial-and-error procedures, and to a decrease of production costs in foundries. Mould filling simulations take a special place in CFD, because a free surface tracking algorithm is required. Over the past decade methods, MAC [3] and SOLAVOF [4], have been extended to 3-D. The robustness of computational methods for mould filling simulations is generally tested in simple geometries [5,6]. While a vertical plate has been used often for validation studies, this paper concentrates at mould filling simulations of a horizontal thin wall casting. Thin wall horizontal castings exhibit a strong interaction between heat transfer (solidification), surfaces tension and gravitational force. The gravitational force in this setting is orthogonal to the plane of flow and has therefore no influence on the shape of the free surface in the plane of flow. Mould filling numerical methods and algorithms have been recently reviewed by Chen et al.[7]."

Jan 1, 1999

By Sanaz Mosadeghsedghi

The feasibility of the application of electrodialysis in separation of light and heavy rare earth elements (REE) in synthetic solutions was investigated. The experiments were carried out using single and binary solutions of a light (cerium) and heavy (ytterbium) REE. The effects of electrical voltage, electrical current, and the addition of complexing agent (EDTA) to increase the separation selectivity were investigated. Separation of Ce and Yb was achieved in binary solutions with and without the addition of EDTA. Higher degrees of separation were seen at higher voltages. Ce–Yb separation was more significant in the presence of EDTA. The separation factor of Ce–Yb and Ce–Yb-EDTA were 1.44 and 2.60, respectively.

By Tom Lewis

This report discusses the evaluation of the ENVIRO-CLEAN PROCESS, a technology developed by Lewis Environmental Services, Inc. for the recovery of metals such as chromium, mercury, copper, cadmium, lead, and zinc from surface and groundwater streams. This new heavy metal removal process (patent-pending) utilizes granular activated carbon with a proprietary conditioning pretreatment to enhance heavy metal adsorption combined with electrolytic metal recovery to produce a saleable metallic product. The process generates no sludge or hazardous waste and the effluent meets EPA limits. A 50 gpm system was installed for recovering hexavalent chromium from a ground water stream at a site located in Fresno, California. The effluent from the activated carbon system was reinjected into the ground water table with the hexavalent chromium concentration < 10 ppb. The system simultaniously removed trichloroethylene (TCE) to concentrations levels < 0.5 ppb. The activated carbon is regenerated off-site and the chromium electrolytically recovered. The full scale system has treated over 5 million gallons of ground water since installation.

Jan 1, 1996

By P. Maraboutis

Iron removal by precipitation as jarosite from Fe-Ni-Co sulfate solutions, (synthetic or real, resulting from laterites leaching) has been investigated. Precipitation was carried out at 95 C, and at an initial pH 1.6, which was either kept constant with CaCO3 or Li2CO3 additions, or left to drift with the evolution of the reaction to lower values. The precipitation of K-, NH4- and Na- jarosite was initially examined using synthetic solutions. In all cases, hydronium ions were incorporated into the precipitate as well. Residual iron in solution was lower (0.2-1 g/1) and equilibrium was achieved faster (within 4-8 h) when precipitating K¬jarosite at constant pH, using CaCO3 for neutralization. Nickel and cobalt losses were small. Na- jarosite precipitation was also studied from real solutions with high initial iron content, under constant pH=1.5, controlled with CaCO3 additions, and it was shown that low residual iron concentration in solution (0.3-0.5 g/1) can be achieved again, with relatively small nickel and cobalt losses. The thickening and filtration characteristics of the precipitates were excellent in all cases examined.

Jan 1, 1988

By Matti Leiponen

During the last few years Outokumpu Oy has put forth efforts to develop the material handling in the Pori tankhouse. The final objective is full automation including cell loading. The fully automated material handling provides high quality anodes and cathodes as well as equipment and handling systems capable of very accurate cell loading. The new machines and equipment for accurate cell loading and the methods to produce high quality anodes and starting sheets are described in this paper.

Jan 1, 1987

By Tsutomu Yamamura

The electrolytic reduction mechanism of rare-earth chlorides such as LaCl3, CeCl3, NdCl3, ` SmCl3 and DyCl3 in alkali chloride baths has been investigated in NaCl, KCI and eutectic LiCI- KCI by means of electrochemical transient methods. The thermodynamic behaviors of rare-earth containing species have been discussed in the frame of Electrode potential - P02- diagram. Low current efficiency found in the case of Nd electro-winning has been attributed to the dissolution of Nd into the bath. The analyses of electrochemical measurement required the elucidation of the effects of the factors such as under-potential deposition, metal dissolution, moisture and oxygen partial pressure.

Jan 1, 2003

By G. Kugler, M. Tercelj

"The 1.2690 high alloyed tool steel is usually applied for cold working and is alloyed with carbide-forming elements Cr, V, W and Mo. It exhibits very poor hot deformability. Since there is no enough available data in literature for elucidation of this problem, hot workability and development of microstructure during hot deformation was studied. Hot compression tests were carried out in temperature range 850-1150 °C and strain rates range 0.001-6 s-1. SEM and OM were used for observation of microstructure. Results revealed very complex precipitation of carbides that depends on deformation temperature as well as on strain rate. It was found that especially at lower temperatures of hot working range the precipitation of carbides strongly depends on strain rate. Three different hot deformation behaviors’ were observed depending on temperature and strain rate range.IntroductionThe hot workability of highly alloyed high speed steels is usually described as relatively poor in comparison to other steels due to their tendency of cracking during hot working especially when inappropriate hot working conditions are applied. Alloying elements such as Cr, W, Mo and V in ledeburitic tool steels form carbides that improve hardenability, strength, hardness, wear resistance, etc., but they decrease hot workability and narrow hot working temperature range in comparison to conventional steels. The size, distribution, type and fraction of carbides, as well as the thermomechanical history of material and hot working parameters have major influence on the hot workability. The microstructure of ledeburitic tool steels during hot deformation can be characterized as a two-phase system consisting of an austenite matrix and a combination of ledeburitic carbides [1-4]. In the soft-annealed condition the total volume fraction of carbides is in the range 19-30% and in the quenched condition in the range 9-25%, depending on the chemical composition. During heating before deformation a large quantity of carbides dissolve, but non-dissolved carbides can have an extremely diverse influence on the hot workability due to variations in their composition, size, distribution, hardness and shape, and their different behavior during the deformation phase [5-7]."

Jan 1, 2011

By Jing Zhang, Qing Xiao, Xulong Liu, Qiuju Li

"Pickling sludge generated from stainless steel production process contains large quantity of Cr, Ni, and Fe. The disposal of and fill sludge directly not only leads to the heavy metal dissolves in the soil and underwater, but also loss value metals. However, the major mineral phases of value metal are hydroxides and there are lots of calcium fluoride and water in the sludge. So the pickling sludge has to be pretreated before reduction-magnetic separation. The TG analysis, reduction reaction and magnetic separation were all used to study the pickling sludge. The result indicated that up to 900°C the total weight loss of pickling sludge was 22.32%. The mass contents of Fe, Cr and Ni in the tailings (non-magnetic) were 4.27%, 0.067% and 0.041% respectively.IntroductionSince 21st century, the stainless steel production in the world has been continuously increasing because of its excellent performance [1]. However, high stainless steel production means a high pickling sludge production. For example, in a stainless steel plant with waste water quantity of 100m3 /h, the production of pickling sludge will exceed 15 Kt/a. Pickling is essential for generating of a homogeneous and corrosion-resistant surface during stainless steel production subsequent process. Pickling of stainless steels is predominantly carried out with an aggressive solution, sulfuric acid H2S04 or composed of nitric acid HN03 and hydrofluoric acid HF [2]. During the pickling process, the pickling acids are recovered through ion exchange and metal ions such as Fe3+, Cr3+ and Ni2+ get into the acids forming the pickling waste water [3]. Then, the pickling waste water is precipitated with lime, forming pickling hydroxide sludge. It is not feasible to recycle or treat the pickling sludge using conventional methods, because the sludge has high contents of calcium fluoride and water but low contents of iron, chromium and nickel. However, it would also pose a potential environmental problem if deposited outdoors over a long term because it contains heavy metals such as Cr and Ni. At present, solidification/stabilization (S/"

Jan 1, 2014

By T. Lezhava

A new reactor model with rotating cathodes has been developed where various forms (dendrite, spongy) of metal depositions and their uninterrupted removal are accomplished by the realization of high current densities and low energy consumption. At the same time in contrast with the existing methods a high quality metal powder may be obtained from concentrated electrolytes without any specific organic or inorganic additives, which allows raising the intensity of the process. The reactor can be used for electrowinning of metals with low adhesive capacity (Pb, Ag, Cu, Zn, Ni, Co, etc.) and the powders. The obtained products may be utilized in general metallurgy as well as in powder metallurgy.

Jan 1, 2006

By S. Z. El-Tawil, K. A. El-Barawy, M. B. Morsi, M. M. Nasr, Z. I. Zaki

"Tue sulphatization of zinc concentrate produced from heated zinc concentrate of Um Ghieg area, eastern desert by ammonium sulphate as sulphatizing agent is carried out at different conditions to achieve the appreciable formation of soluble sulphates. The maximum zinc recovery as soluble sulphate equfils to 95% upon using 1.5 stoichiometry ammonium sulphate at 600 °C for one hour. Tue obtained leached zinc sulphate solution is subjected· to purification process to prepare high pure zinc metal and zmc compounds such as pure zinc sulphate, zinc caibonate and zinc oxide. The products obtained are analyzed chemically and identified by X-ray analysisTue mechanism and kinetics of the sulphatization process of zinc concentrate are considered where the activation energy is calculated and equals to 33.3 K.J.mol""1 A process flowsheet for the overall sulphatization process of zinc concentrate by ammonium sulphate is proposed.IntroductionConsiderable reserves of zinc ores are present in Um Ghieg area eastern desert, Egypt. The possibility of extraction zinc from these ores and preparing its valuable compounds by choosing a more feasible technology become of vital importance. An attention is focused on the sulphatizing roasting processes (1-9) to achieve the appreciable formation of soluble sulphates. Previous publications are reported in our division by El. Tawil and others (10-16) using ammonium sulphate as sulphatizing agent for the successful treatment of nonferrous bearing materials.Therefore, the present work aims to study the different factors affecting the sulphatizing roasting process of local zinc coocentrate by anunonium sulphate to extract completely zinc and preparing its main compounds. Tue mechanism and kinetics of the different chemical reactloos that 1ake place in the process are considered."

Jan 1, 2000

By Peter K. Liaw, Charlie R. Brooks, David C. Joy, Wei Zhao

In this paper, effects of oxidation, porosity and fiber-fabric stacking sequence on flexural strength of a continuous silicon carbide fiber (SiCr) fabric-reinforced SiC ceramic-matrix composite (CFCC) were studied. The failure mechanisms were correlated with flexural strengths of CFCC samples, both before and after oxidation. Microstructures and fractography were investigated using scanning electron microscopy (SEM). The chemical change after oxidation, such as Si, C, and 0, and their distributions, were detected by the SEM energy-dispersive X-ray spectroscopy (EDXS) line-scan chemical analysis technique. These effects on the strength of the CFCC can be attributed to following reasons: (i) The decrease in the flexural strength after oxidation is mainly due to degradation of the strength of Nicalon fibers and the damage of fiber/matrix interface both caused by high-temperature chemical reactions, (ii) Porosity is not too important in affecting the strength of the CFCC, when the bonding of the forced flow chemical vapor infiltration (FCVI)-SiC matrix is stronger than that of the fiber/matrix interface. However, a higher porosity content will be harmful, because higher porosity will both decrease the effective elastic modulus of the FCVI-SiC and make pore-linkage easier to occur, which is more likely to cause premature failure, (iii) The variation in the lamina stacking sequence of the CFCC changes the elastic stress distributions along the thickness direction of specimens, the magnitude of ceramic matrix-cracking stress, the effective elastic moduli of the laminate, and different crack initiation sites as well as different failure modes, and thus, leading to the scatter in the flexural strength of the CFCC.

Jan 1, 1998

By Chunhua Liao, Chao Peng, Guangsheng Huo

To get the separation of tungsten and molybdenum, we adjusted the pH of the solution to 7, at which tungstate (WO4 2-) will be polymerized into HW6O21 5-, while molybdate will still exist in the form of MoO4 2-. Two strongly basic anion exchange resins (D201, D213) were experimented for the separation of tungsten and molybdenum. The results of condition experiments indicate that D213 resin performs better in the treatment of lower concentration solution A (WO3 10g/L, Mo 4.12g/L) with a separation factor as high as 10.64. While D201 resin is more suitable for the high concentration solution B (WO3 70g/L, Mo 28.97g/L) with a separation factor of 6.9. The results of column testing performed on D213 resin show that the solution after loading process with a mass ratio of Mo/WO3 = 50 and the desorption solution with a mass ratio of WO3/Mo = 27 can be obtained

Jan 1, 2014

By Ximeng Zhu

The electrochemical behavior of mineral and coal pyrites in stirred and quiescent alkaline boratelsulfate solutions @H 7.9-10.5) have been investigated using cyclic voltammetry. Significant differences in the electrochemical response of these pyrites were observed. At the mineral pyrite surface, three anodic peaks at about -0.8 V, -0.1 V and +0.5 V (SCE) have been detected along with their corresponding reduction peaks. The first two peaks correspond to FeIFeOI) and FeOI)lFe(III) oxidation. The third peak is present for quiescent conditions but disappears as a distinct peak when the electrolyte is stirred. In the upper voltage region +0.30V (SCE), the current increases markedly during stirring and the reactions correspond to the oxidation of pyrite with the formation FeOII) oxides plus elemental sulfur. Also there is evidence that Fe oxy-ions form. Coal pyrites, under rapid sweep conditions display only the first two anodic peaks, the associated reduction peaks and an additional reduction peak corresponding to one or more of the high voltage oxidation products. After prolonged exposure to high potentials, coal pyrite displays reactions similar to those of mineral pyrite but at much higher current densities demonstrating the much higher reactivity of the coal pyrite. The reactivity sequence was Upper Freeport coal pyrite > Pittsburgh coal pyrite > mineral pyrite.

Jan 1, 1991

By M. M. Swan

A stratiform gold occurrence of Precambrian age located 20 miles southeast of Prescott, Arizona, within the Agua Fria Mining District, displays chemical, mineralogical, structural and lithological patterns indicative of a distal, exhalative volcanogenic environment. Metavolcanic and metasedimentary rocks of the Proterozoic Yavapai Series (1775-1820 m.y.) host the mineralization and are&apos;characterized by greenschist grade metamorphism, steeply-plunging penetrative folds and steeply-dipping schistosity. Mineralization is confined to a 100m thick stratigraphic section that is comprised of a series of thin auriferous massive sulfide beds and intercalated schist .containing disseminated sulfides. The mineralization extends more than 4km along strike. Coincident with, and largely confined to the mineralized strata, are anomalous amounts of As, Sb, Cu, Pb, Zn and Ag and associated silicification, sericitization and carbonatization. This exhalative mineralized system is interpreted to have been deposited in a paleo topographic low on the distal flank of a submarine rhyolite dome and to represent the final episode of a Precambrian volcanic cycle.

Jan 1, 1981

By Petre Stelian Nita

In small steelmaking shops, in foundries and forging plants, there are not too many option to recycle the basic slags, which are not suitable for many purposes of recycling, because of their low chemical and structural stability. A solution of an adequate recycling is a direct recycling in EAF. Several quality requirements, physico-chemical properties and proportions of slags must be analysed. The progress in this fields permites to establish an adequate proportion of recycled slag, based on enough exact computation of the related property. For oxydizing slag, obtained during melting and in the first part of decarburization operation, the problem of phosphoms contents can be analysed using the phosphate capacity (C PO34-). For reducing periods, during deoxidization operation, desulphurization also occurs and the problem of the sulphur contents can be analysed using the sulphur and sulphide capacities ( Cs / Cs) Between this two complex thermodynamic indicators of the slags. a direct relation is established, using thermodynamic aspects, resulting from the equilibrium constants for dephosphorization and desulphurization process and also, using the optical basicity of slags, computable from the chemical analysis of the slags. On this basis starting from the steel quality requirements. adequate strategies can be established in order to obtain high rates of recycling (between 50-80%) of steelmaking slags. Important cost savings are obtained through this procedure, based on the correct amounts of the fresh lime, iron ore and fluidizers. Keywords: Slag, Properties, Recycling

Jan 1, 2003

By H. Senoh

For the purpose of clarifying the reason caused a drastic decrease of discharge capacity for MmNi3.6Mn0.4Al0.3Co0.7 electrode at relatively low temperatures, various factors influencing the charge-discharge processes were investigated in the temperature range of 25°C to -40°C. The charge efficiency obviously decreased at low temperatures less than 0°C due to a decrease in the rate of the charge-transfer reaction on the electrode surface. Moreover, both the rate of the hydrogen diffusion from the alloy bulk to surface and the rate of the charge-transfer reaction significantly influenced the high-rate dischargeability. The addition of Mo to MmNi3.6Mn0.4Al0.3Co0.7 alloy was found to be effective for improving the electrocatalytic activity, leading to the improvements of the charge efficiency and the high-rate dischargeability at relatively low temperatures.

Jan 1, 2002

Mineralogical and metallurgical scoping testwork were carried out to investigate the production of separate, marketable gold and platinum concentrates. The study utilized a flotation concentrate assaying approximately 5 wt% gold and 5 grams per tonne platinum. The gold-platinum mineralization was recovered from a placer deposit. Optical microscopy and scanning electron microscopy with energy dispersive x-ray analysis identified gold as zoned Au- Ag and Au-Ag-Cu alloys. Platinum primarily occurred as weakly zoned, variably magnetic Pt- Pd-Fe alloys. A combination of gravity and magnetic separations resulted in a gold concentrate grading 86.9 wt% Au (and 9.lwt% Ag) and a separate platinum concentrate grading 400 g/t Pt with recoveries of 94.5% and 96.7%, respectively. Magnetohydrostatic separation (MHS) using the Magstream 200 Separator indicated promising results.

Jan 1, 1994

A simulation of a capper concentrate smelter was built with a capacity of 450,000 tons per year. The system&apos;s components to simulate were three : a Reverbetory furnace, a Wiente &apos; s modified converter ( TMC ) and two cranes. The system was classified as dynamic, stochastic and discrete. In the simulation language choice it was concluded that the most advantageous one was GPSS/H. The model verification was done through the interactive Debugger that the language has and the statistical validation was done through the result variables of sane activities, that as a whole characterize the system (charged matte and charged concentrate to the TMC, skimming white metal and skimning slag). The validation was done comparing the simulation results of these variables with the ones obtained for those variables in a specific month in the smelter. The comparison consisted in a difference of means test and in all cases the equality was accepted with a 95% of confidence. The animation tool was PROOF, a general purpose animator, that is used after processing the simulation.

Jan 1, 1994