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By A. V. Tarasov

In order to improve the efficiency of hydrometallurgical processing of pyrrhotite concentrates, an integrated set of research has been carried out to investigate the use of sulfur dioxide in individual unit operations and as a leaching agent in the autoclave process as a substitute for oxygen. Treating iron-containing raw materials for production of nonferrous metals are based on the selective reaction of SO2 with iron sulfides and oxides. Iron is dissolved as sulfate, which can be treated in a separate circuit to produce iron-containing pigments or it can be disposed of after neutralization. Nonferrous and precious metals contained in pyrrhotite concentrate do not react with sulfur dioxide and remain virtually completely in the solid phase, i.e. high-grade sulfide concentrate to be treated by hydro- or pyrometallurgical methods. Elemental sulfur formed in the process of leaching is separated from the pulp in granulated form as a result of the use of special surfactants. The process of sulfide concentrate leaching with the use of sulfur dioxide is conducted at temperatures above the sulfur melting point (119°C) with distributed feeding of surfactant and under a partial pressure of sulfur dioxide of up to 0.3 to 0.5 MPa.

Jan 1, 2006

Acid mine drainage containing heavy metal ions is a large environmental problem facing the mining and mineral processing industry. The femte coprecipitation is a novel technique for removing heavy metal ions from waste water, recently applied to acid mine drainage. The fenite precipitation is usually performed at high temperature and therefore if applied in conventional manner, it becomes uneconomical to treat large quantities of acid mine drainage. In this paper the ferrite precipitation at ambient temperature-is &died. The possible mechanism of ferrite formation is discussed Experimental results from Noranda Tailing and Berkeley Pit water treated by this process are presented.

Jan 1, 1994

By Chr. Kersch

This project further develops supercritlcal fluid extraction as an industrial soil remediation process. Heavy metals are removed from sand using CO2, The effect of the type of complexing ligands, pressure and water content on the extraction efficiency is investigated.

Jan 1, 1999

By Theo Lehner

The Rönnskär smelter has wide experience in the field of recycling of non-ferrous metals. Today, smelting and refining from primary and secondary raw materials are integrated in a complex flow sheet. Boliden operates a lead flash smelter, a lead refinery, a copper smelter and refinery, a sulphuric acid and sulphur dioxide plant, a slag fuming plant and precious metal plant at its Rönnskär smelter in the North of Sweden. The Business Area Smelter Operations also incorporates Boliden Bergsöe, Sweden's lead-acid battery recycler, and Norzink, Norway, where recycled zinc accounts for more than 20% of it's production. Raw materials for the Rönnskär smelter include concentrates, ashes, slags, metallic scrap, electronic scrap and electric arc furnace (EAF) steel-making dust. This paper briefly describes current operations and illustrates current measures to improve productivity. Limits to recycling as experienced by a non-ferrous smelter are, illustrated. The deportment of critical elements contained in raw materials is also discussed.

Jan 1, 1998

By Maria Cristina Ruiz

The removal of iron from the leaching circuits is a common problem in the hydrometallurgical processing of non ferrous metals. Among the currently available processes, hematite precipitation is the most recommendable from an environmental point of view. This paper is concerned with the batch precipitation of hematite from ferrous sulfate solutions. One of the main objectives of the study was to determine the effect of the experimental conditions on the extent of iron precipitation as well as the purity and the particle size distribution of the precipitates. The main variables studied were temperature (180 to 220 ºC), concentration of sulfuric acid (1 to 10 gpl), initial iron concentration (1 to 15 gpl) and partial pressure of oxygen (3 to 7 atm). The results showed that increasing the oxygen partial pressure from 3 to 7 atm produced a very small increase on the rate of hematite precipitation indicating that a large partial pressure of oxygen is not needed for an effective ferrous to ferric oxidation. An increase in the temperature produced finer precipitates with lower sulfur contents. On the other hand, an increase in sulfuric acid concentration and initial iron concentration produced precipitates with larger particle sizes and higher sulfur contents.

Jan 1, 2006

By B. J. Beaudry

The preparation of alloys containing one to two percent of the volatile lanthanide metals Sm, Eu, Tm and Yb in the high melting point (HMP) rare earth metals Sc, Y and Lu was accomplished by a vapor deposition, diffusion method without crucible contamination. The method avoids the melting of the HMP metals which would introduce impurities from the crucible, generally Ta or W. Plates of the HMP metals were hung from the lid in the upper part of the Ta crucible. The volatile metals were placed on the bottom and the lid welded in place under an atmosphere of helium. By proper selection of thee alloying temperature, the effusion of the metal vapors, through the helium atmosphere was slow enough to permit diffusion to occur and prevent refluxing of the newly formed alloy. Very volatile metals such as Mg required a Knudsen cell with a suitably sized hole to prevent too rapid transfer of the low melting metal. Electron microprobe analysis of a cross-section of the HMP metals showed a homogeneous distribution of the volatile metals. The time and temperature required to obtain a homogeneous rare earth alloy without contamination are given. The use of a Knudsen cell to form magnesium-rare earth alloys is reviewed.

Jan 1, 1992

Korea has about 68 hundreds million tons of limestone's reserves. Still, high-Ca2+ limestone containing more than 52% calcium oxide makes up for about 12% only; hence the need for securing and effectively developing limestone. The best solution is to manufacture precipitated calcium carbonate (PCC). The synthesis of PCC using high-Ca2+ limestone has several advantages including the efficient development of resources and easing the import dependence on PCC. The first step is the selection of suitable limestone for the synthesis of PCC. In this study, formation age was decided as the primary key point, with its effect on calcination, hydration, and synthesis of aragonite investigated. Results showed that the yield of aragonite increased when newer limestone was used. On the other hand, neither the activity and bulk density of quicklime nor the particle size of aragonite was affected by the formation age, although special values were registered following each formation age. Moreover, the bulk density of quicklime and particle size of aragonite tended to increase with decreasing activity. This result is different from that of the other experiment. Therefore, a suitable method for measuring the activity of quicklime for use in the manufacture of PCC must be established.

Jan 1, 2006

By Toshio Kurikami, Koichi Yamazaki

"Toho Zinc Co., Ltd Chigirishima Refinery has the production capacity of electrolytic lead for 95000t/y by sintering- blast furnace electrolytic process. Lead raw materials are lead concentrates, spent batteries and dusts that contain lead from other companies, and these are handled by existing smelting process. There are many circulation materials in the process, because the system has been constructed with improving the recovery rate and protecting the environment. This report describes material balance in each process, distribution of the lead and various components, and it examines present state of the processing. In addition, we report the result that we have tried to improve the work environment.IntroductionThe Chigirishima Refinery of the Toho Zinc Co., Ltd. is located in Chigirishima, an island 4km off the coast of Takehara-city, Hiroshima, Japan. The Chigirishima Refinery began lead smelting operations in 1951.The Chigirishima Refinery adopted the sintering-blast furnace-electrolytic process and has an electrolytic lead production capacity of 95,000 tons/year. The existing smelting process handles raw materials from lead concentrates, spent batteries, and lead-bearing dust from other companies. This system was constructed with the intentions of improving material recovery ratios and protecting the environment; therefore, there are many materials recirculating throughout the smelting process. This report describes the material balance in each process and the distribution ciflead and various components, and it examines the present state of processing. In addition, we report the results of our attempts to improve the work environment."

Jan 1, 2000

By Zhitong Sui

Based on several case studies on the precipitating behavior of valuable nonferrous metal compounds (VNMC) in molten slags a green technology for the recovery of VNMC from molten slags was proposed. This technology involves three steps: (I) The selective enrichment of the dispersed VNMC into the designed mineral phase in the molten slag; (2) The selective coarsening of the designed mineral phase to a critical grain size in the molten slag; (3) The selective separation from tailing of the grown mineral phase in the solidified slag by dressing or hydrometallurgy processes. This is a clean and low cost technique and has a great capacity to deal with a large quantity of slags. The utilization of the recovered VNMC such as Titanium, Boron, Vanadium compounds was summarized as examples of application. It was confirmed by experiments that the precipitating behavior of the designed mineral phases like Perovskite(CaTiO3), Suanite(2MgO*B2O3) and Sincosite(CaOoV2O5*P2O5) in molten slags is obviously affected by operation factors such as temperature, chemical composition, heat-treatment, additives and so on. The precipitating kinetics and mechanism of the VNMC from molten slags during solidification processes were also investigated.

Jan 1, 2003

By A. H. Rosenberger, M. A. Tschopp, M. A. Groeber, K. N. Solanki, A. L. Oppedai, J. D. Miller

"Characterizing the spacing of primary dendrite arms in directionally-solidified microstructures is an important step for developing process-structure-property relationships by enabling the quantification of (i) the influence of processing on microstructure and (ii) the influence of microstructure on properties. The research objective herein is to evaluate the capability of various conventional approaches, as well as new or modified approaches, for spatial point pattern analysis with application to characterizing experimental dendritic microstructures. Both computer-generated and experimental dendritic microstructures are used for this analysis along with numerous techniques based on the nearest neighbor spacing, Voronoi tessellation, Delaunay triangulation, or graph theory. Comparison of new metrics with traditional primary dendrite arm spacing metrics will also be discussed for both local and global measures. The current methods investigated will supply information of local spacing and coordination number while addressing edge effects, parameter sensitivity, and correlation with interdendritic features, thus providing insight into how processing affects properties.IntroductionDeveloping an enhanced understanding of mechanical behavior in materials relies upon sufficiently characterizing microstructure details at the relevant length scales that contribute to this behavior. Moreover, to truly enhance the predictive capability of processing-structureproperty models that aim to improve material performance requires a quantitative description of the relevant microstructure features and, thereby, the material itself"

Jan 1, 2013

By Anastasia Alksnis

Pyrrhotite is an iron deficient, low nickel content sulfide mineral that is commonly associated with pentlandite, a nickel-rich sulfide; and are both main components of the nickel ore mined in Sudbury. Pyrrhotite tailings generated in the concentration of Ni ores are stored in tailing reservoirs and presents serious environmental risks including acid mine drainage. This study investigated the potential of converting pyrrhotite into a valuable resource through the use of fluidized bed roasting, in which the mineral will be oxidized to produce iron oxide and SO2 gas. These products can then be used to create iron for high-grade steel and elemental sulfur. Thermogravimetric analysis of Sudbury pyrrhotite was performed to study the oxidation kinetics, supporting the feasibility of this process. Further, energy and materials balance was carried out to establish the basic parameters of a possible roasting process.

By William Petruk

The Kidd Creek base metal deposit near Timmins, Ontario contains around 0.15 wt% Sn, mainly as cassiterite. The cassiterite occurs largely as inclusions in sphalerite, with 85% being in grains smaller than 18.5 micrometres in diameter. Concentrates and tails from the company's Cu, Pb and Zn circuits were studied to determine the liberations and recoveries of cassiterite in the products. The ore had been ground to about 65.% minus 44 micranetres in diameter (-325 mesh); 55% of the cassiterite was liberated. About 92% of the liberated cassiterite and 70% of the unliberated cassiterite were in the concentrator tails, and 20% of the unliberated cassiterite in the zinc concentrate. The company had attempted to recover the cassiterite from the concentrator tails by gravitational methods but recoveries were low. The grain size of the cassiterite in the gravity Sn concentrate was similar to the grain size of the liberated cassiterite in the concentrator tails. Research on flotation of the fine grained cassiterite from Kidd Creek ore has been conducted,

Jan 1, 1990

By Florian Kongoli

The production of a homogeneous self-fluxing sinter is an important step in iron making processes. A good sinter should have good permeability and reducibility and has to keep those characteristics for a certain time. An early melt down of the sinter in the blast furnace, where its solid state reduction is essential, would cause many problems such as low permeability and reductibility. Nevertheless, the important factors that influence these characteristics, such as the chemistry of the sinter and the fluxing effect during sintering and sinter reduction conditions have not yet been clarified. In today's new reality where many new minor components such as Al2O3 and MgO enter to the sinter through raw materials, the quantification of the fluxing effects during sintering becomes even more important. In this work, the liquidus surface and phase relations of the sinter primary melts in the CaO-FeO-Fe203-Si02 system at sintering conditions have been quantified. The fluxing effect of oxygen potential, Al2O3 and MgO has also been quantified by the means of some practical diagrams that can directly help the optimization of the sintering processes.

Jan 1, 2003

By Laurentiu Nastac

"The importance of investigating solute redistribution during the unidirectional solidification of multi-component alloys is broadly discussed in the literature. A previously developed analytical model that was experimentally validated for Al-Cu, Sn- Bi and Fe-Si dilute binary alloy systems is used in this article to study in detail the solute redistribution, the liquid/solid interface stability based on an extended transient constitutional undercooling criterion and the size of the initial transient region during the unidirectional solidification of Ti-6-4 and Ti-17 alloys. A comparison between Ti-6-4 and Ti-17 alloy systems with respect to interface stability and the size of the initial transient region is also provided. The effective partition coefficients of the alloying elements in these alloys were determined based on specially designed experimental measurements.IntroductionThe importance of investigating solute redistribution during alloy solidification is broadly discussed in the literature [1-5]. One of the relevant applications of this study would be the mathematical modeling of equiaxed and columnar solidification of multicomponent alloys. This includes the instability of the solid/liquid interface. There are several mass and heat transfer processes that involve the calculation of solute redistribution during directional solidification such as industrial directional solidification processes, continuous casting, remelting processes, Czochralski crystal growth technique, floating zone techniques, etc."

Jan 1, 2012

By Jonkion M. Font, Ramana G. Reddy

A thermodynamic model for a priori predictions of arsenic and antimony impurity capacity in Ni-Cu mattes and slags was developed based on the Reddy-Blander (RB) capacity model. The As and Sb capacities were calculated a-priori considering the RB capacity model in Ni-Cu mattes and FeO-FeO1.5-MgO-CuO0.5-NiO-SiO2 slag at 1573 K and 0.1 to 1 atm partial pressure of SO2. The results showed an excellent agreement between the model calculated and experimental data of arsenic and antimony capacities between the mattes and slag. The impurity capacity model developed here, can be extended for prediction of impurity capacities in multi-component base metal slags and base metal mattes. Such a priori predictions of impurity capacities can lead to develop or improve the efficiency of impurity removal from the base metal smelting, converting and refining processes.

Jan 1, 2014

By M. Urda-Kiel

Stainless steel is increasingly used as a cathode starting sheet. It was shown earlier that even when depositing copper on copper, a substrate-influenced zone appears in the deposit structure, followed by a transition zone and finally by the electrolysis-influenced structure. On copper, the substrate-influenced zone has a thickness of twenty micrometers and on titanium, eventually more than fifty micrometers. Initial nucleation and growth have a considerable influence. In this paper, copper was deposited in a channel cell on four different 304 stainless steel substrates: mechanically polished and anodized, respectively, at 0, +400 and +800 mV/SHE in 1M H2SO4 at 20°C. Copper was deposited under electrowinning conditions after solvent extraction (SX) (40 g/l Cu++, 180 gh/l, H2SO4, 20 or 60°C). The results showed that, although Auger surface analyses of the substrates were only slightly different one from another including the oxide thickness, nucleation and initial stages of growth were very sensitive to the surface treatment of the substrate. Potential step and current step methods gave similar results : progressive nucleation followed by 3D diffusion controlled growth. The highest nucleation frequency was observed on stainless steel anodized at 0 mV/SHE, under various electrolysis conditions. The potential influence of these findings on industrial practice is discussed.

Jan 1, 1999

By Masahiro Hirasawa

"As a fundamental study on pyrometallurgical process that involves recycling steel-making dusts, of which major components are oxides of Zn and Fe, and waste polyvinyl chloride simultaneously ·at. a temperature below 1273 K, the reactions between the mixture of ZnO + Fe20 3 and PVC or the compound ZnFez04 and PVC are investigated in a series of thermogravimetric and small scale reactor experiments under inert atmosphere at below 1273 K. The reaction mechanisms are discussed· on the .basis of the thermogravimetric data. From the results of reactor experiments, it is shown that the chlorination of Zn in the oxides by Cl in PVC, the vaporization of ZnC12, the reduction of iron oxide to metal Fe by C and H in PVC, and, thereby, the separation of Zn and Fe in the oxides take place simultaneously at the temperature ~= 1200 K.IntroductionSteelmaking dusts are metallurgical wastes consisting mainly of oxides of Zn and Fe with smaller amounts of other heavy metal elements, such as Pb. In the recent investigation, [1] the present authors have investigated the fundamental aspects of a potential pyrometallurgical process· of recycling steel-making dust with polyvinyl chloride (PVC) at temperature T < 1273 K under Ar atmosphere. The performance of a similar process, in which HCl in the combustion gas of PVC is used to chlorinate Zn in the EAF dust under oxidizing atmosphere, has been investigated by Tailoka and Fray [2] with fundamental experiments. Figure 1 shows an example of the potential ·diagram of Zrt-Cl-0 and Fe-Cl-0 systems. In the figure, we can find two regions where ZnCl2(g) can be separated from Fe containing compounds. One is ZnCiz-Fe20 3 coexistence region at higher oxygen and chlorine potentials and the other is ZnCl2-Fe coexistence region at lower oxygen and chlorine potentials. The process adopted by Fray and coworkers is aimed mainly at the performance of Zn/Fe separation in the higher oxygen potential region. In the present study, the lower oxygen potential region is focused on."

Jan 1, 2000

By Yoji Imai, Akio Watanabe, Masakazu Mukaida

"To clarify the feasibility of alkoxides and acetylacetonates as precursors for laser CVD of metal oxides, vapors of tantalum or titanium alkoxides and zirconium acetylacetonate were irradiated by KrF excimer laser and deposits were characterized by XRD and XPS measurements. As for tantalum and titanium, non-stoichiometric crystalline oxides grew nearly phototropically, however, zirconium oxides deposited showed only halo-pattern by XRD measurements. Electric conductivity measurements of tantalum oxides implied the improvement of the insulating properties by the addition of activated oxygen to the ambient.IntroductionThere has been renewed increasing attention to the metallic oxide thin films because ofits promising usefulness in many applications, such as high-Tc superconductors and ferroelectric devices. A variety of thin film preparation techniques have been studied such as sputtering, chemical liquid deposition (sol-gel and metalorganic decomposition), pulsed laser deposition and chemical vapor deposition (CVD). Among them, we think CVD is the most promising method because it offers a high controllability of morphology and good step coverage at relatively high growth rate. Preparation of oxide films by CVD can be achieved using a precursor containing metallic element and oxygen containing gas such as N20 at the same time. However, metalorganic (MO) compounds which contain both metallic element and oxygen, directly bonded to metallic element, seems to be more favorable because some of MO has a good properties for CVD such as a rather high vapor pressure, stability in ambient and low toxicity."

Jan 1, 1998

By Waraporn Piyawit

Grinding sludge from the sintered neodymium-iron-boron (NdFeB) magnets production process was enriched with critical rare earth elements (neodymium, dysprosium and praseodymium), which can be up to 30% in the magnets. The demand of NdFeB magnets are simultaneously growing. Therefore, rare earths recovered from waste residue would reduce the demand of rare earth elements from primary sources. In this study, the feasibility of recycling rare earths through a hydrometallurgical process was investigated. The selective leaching of Nd from grinding sludge can successfully raise the rare earths concentration to 70%. The necessity of an oxidation pretreatment to improve the selectivity between Nd and Fe will be described.

By Pengkai Wang, Huimin Lu, Xiaoxiang Zhang

"In this paper, it was studied an electrochemical reduction process of carbon dioxide in ionic liquids such as 1-n-butyl-3-methylimidazolium hexafluorophosphate ([Bmim] PF6) as the electrolyte. The electrolysis experiments were carried out under current and potential controls. The cathode products contained carbon nanotubes, carbon nanofibers, nanographites, and amorphous carbon. To establish the actual current and potential ranges, the electroreduction of carbon dioxide dissolved in the ionic liquid was studied by cyclic voltammetry on glass-carbon (GC) electrode at room temperature. The electrochemical mechanism of carbon dioxide electroreduction was studied for explanation of all obtained results. Carbon dioxide in ionic liquids was electroreduced, similar to metals oxides being electroreduced in molten salts.IntroductionGlobal warming caused by the increase of carbon dioxide in the atmosphere has become one of the most concerning environment problems, so the solution to this greenhouse effect is very urgent. However, the carbon dioxide is also a cheap and abundant raw material that represents a potential source for the production of chemicals and fuels. Therefore, the development of the technologies that achieve simultaneous reduction and conversion of carbon dioxide to fuels is important. The electrochemical reduction of carbon dioxide is one of the effective approaches to transform CO2. Many investigations have been carried out on the electrochemical reduction of CO2 in both aqueous [1] and non-aqueous [2] electrolyte solutions with different electrodes. The solubility of CO2 in water is very low even under high pressure of CO2, and some investigators have brought focus into the electrochemical reduction of carbon dioxide in organic solvents, because they dissolved much more CO2 than water did. However, the hazardous or toxic properties of organic solvents hinder their use."

Jan 1, 2009