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By Leiv Kolbeinsen, Stian Seim, In-ho Jung

"The current work presents new experimental data in the iron-unsaturated region of the FeTiO3-Ti2O3-TiO2 slag system. The samples are prepared by melting pure reactants in a high frequency induction furnace that employs a cold crucible. A similar experimental set-up has been described in literature and proven suitable to investigate high titania slags. The FeO content of the samples range from 3.7 to 21.8 wt% and the Ti2O3 content range from 3.6 to 30.1 wt%. The liquidus temperatures of the samples are measured in-situ by a spectropyrometer and range from 1450 to 1645 °C.In addition, an improved thermodynamic database for the FeO-Ti2O3-TiO2 system has been developed. Ternary parameters have been included and optimized to fit previously published experimental data. This optimization minimizes the discrepancy between experimental data and thermodynamic calculations as previously discussed in literature. New liquidus projection plots are proposed for the FeO-Ti2O3-TiO2 and the FeTiO3-Ti2O3-TiO2 systems.IntroductionIlmenite (FeTiOs) smelting is a relatively small industry world-wide. However, a reasonable focus on the process has been applied in Norway due to the location of one such smelter in Tyssedal, which is located in the western part of Norway. The process is essentially carbothermal reduction, where most of the iron in the ilmenite is reduced to its metallic state, and the titanium oxide is concentrated in the slag product. The metallic iron is sold as a high purity pig iron and finds applications in cast products. The slag concentrate is further processed for the production of TiOvpigment and/or titanium metal. This further processing can be performed through different routes according to the purity of the slag concentrate."

Jan 1, 2012

By Jamil M. Khalifeh, Shadia J. Ikhmayies, Bothina A. Hamad

"We computed the optical properties of the cubic niobium nitride (o-NbN) compound using the full potential linearized augmented plane wave (FL-LAPW) method within density functional theory (DFT). The complex dielectric function and optical constants, such as optical absorption coefficient, refractive index, extinction coefficient, energy-loss spectrum, and reflectivity, are all calculated and compared with experimental results. The behavior of the computed quantities is similar to that obtained experimentally, but the optical positions are shifted to lower energies. This shift was related to the strong interband transitions, which are located at energies higher than 5 eV for NbN- as they are for IV B transition-metal mononitrides- and they appear in the computed spectra and not in the experimental spectra. These interband transitions simply shift the position of the reflectivity edge or the screened plasma frequency to the longer wavelength side.IntroductionIn recent years, NbN, as a transition metal nitride, has become a very popular material due to its high hardness, melting point, wear resistance, chemical inertness and temperature stability, which makes it suitable for use as emission cathodes in microelectronics and sensors, optical films and micro-mechanics etc [l]. Niobium nitride has long been known as highly polymorphic material, for which several crystalline structures have been reported in the literature [2]. These structures include the well known super-conducting rock-salt (Fm-3m, or Bl) structure (o-NbN), the hexagonal structure with space group p63/mmc and prototype Fe2N (18fuN), the hexagonalstructure with space group p63/mmc and prototype NiAs ~-NbN) and others.There has been a lot of computational studies for the structural and electronic properties ofNbN [3, 4-7], but according to our knowledge there is not any computational work that has been devoted to study the optical properties of this transition metal compound. At the same time a number of authors had performed experimental work in this direction. For example, Xin-kang et. al [l] studied the microstructure and optical properties of magnetron sputtered NbN thin films. Torche et. al [8] studied the composition, structure, electrical and optical properties of nonstoichiometric niobium nitrides. Newport et. al [9] investigated the reflection and transmission spectra of cubic niobium nitride films, and Tanabe et. al [10] had investigated the optical parameters and reflectivity of reactively sputtered NbN thin films by using in situ ellipsometry."

Jan 1, 2013

By Jörg Wallner

In order to limit SO2 emissions, the Montanwerke Brixlegg AG has installed a desulphurisation plant with the primary aim of reducing the peak emissions from the copper converter that are of particular ecological concern. The author discusses the process requirements, the desulphurisation process selected and the results achieved.

Jan 1, 1996

By Lianjun Liu, Ying Li, Qianyi Zhang

"Photocatalytic reduction of CO2 by H2O for production of Cl fuels (CO and CH4) was studied using copper and iodine co-modified TiO2 (Cu-IffiO2) nanocomposites, with copper deposited on the surface and iodine doped in the lattice. The nanocomposites were prepared via a combined hydrothermal and wet impregnation process. All I-doped samples demonstrated visible light activity. Under UV-vis irradiation, co-modification of Cu and I significantly increased TiO2 photoactivity compared with bare TiO2 or those modified with only one species.IntroductionThe photoreduction of CO2 into fuels on photocatalysts such as TiO2 has been regarded as an important approach to solve both energy shortage and globe warming problems [1]. However, the wide band gap and fast recombination ofphotoinduced hole (h+) and electrons (e"") limited the application of TiO2 in CO2 photoreduction reaction. Extensive research has been conducted to improve the photocatalytic ability ofTiO2 by depositing or doping foreign ions that can enhance charge transfer and/or creates intra-band-gap states to induce visible light absorption at the subband- gap energy. Compared with mono-doping, co-doping of metal/nonmetal species has been reported to have higher photocatalytic activity for TiO2 [1-3]. Our previous studies showed that Cu deposited on TiO2 [4] or iodine doped in TiO2 [5] significantly enhanced the catalytic efficiency for CO2 photoreduction and increased the response to visible light. We hypothesize that there could be a synergetic effect if TiO2 is co-modified by both Cu and I species resulting in further improvement in CO2 reduction efficiency. In this work, we synthesized and characterized Cu-IffiO2 samples and investigated their activity toward CO2 reduction under visible and UV-vis illumination, respectively.Experimental MethodsMaterialsTitanium tetra-isopropoxide (TTIP, 98%) and isopropanol (C3HsO, 99.8%) were purchased from Acros Organic. Iodic acid (HIO3,99.8%) and Copper Chloride (CuCh, 99.9%) were purchased from Alfa Aesar. All other chemicals were analytical grade and used without further treatment."

Jan 1, 2012

By Terence Makanyire, Animesh Jha

The dissolution and chemical properties of vanadium, zirconium, and niobium in rutile lattice are analyzed by comparing the octahedral site preference energies, with respect to Ti4+ ion in the solvent phase. The oxides are often present in rutile lattice and interfere in achieving the quality of pigment grade TiO2 due to favourable Gibbs energy for dissolution in the solvent rutile matrix. Binary mixtures of V2O5 { TiO2; Nb2O5 { TiO2 and ZrO2 { TiO2 with compositions of 80, 85, 90, 95 and 97 wt% TiO2 were made, pelletized and sintered at 1100 °C for 24 hours. The solidsolution mixtures were then cooled and leached in 2M NaOH for 3 hours at 60 °C. Phase and lattice parameter characterizations, and microstructural and compositional analyses were then carried out using X-ray diraction and SEM/EDX, respectively. The leachates were analysed by Atomic Absorption Spectroscopy (AAS), using which the solute dissolution model for oxides were investigated.

Jan 1, 2014

By U. M. Mutnti

In order to meet the stringent market requirements for high purity cobalt, ZCCM commissioned the VIR plant in December 1982. The plant comprises a 4.1 tonne/heat vacuum induction furnace with a rated annual capacity of 2,500 MT of barstock. In the VIR furnace, molten cobalt is held under vacuum at 1600°C resulting in the removal of more volatile impurity elements by distillation. Operations todate have demonstrated that Pb, Zn and Cd have good distillation rates in excess of 95%, leading to cobalt containing 1 ppm or less of the above elements. Removal of other impurities such as Se, Bi is about 65% with the finished product still assaying around 1 ppm of each of these elements. Vacuum refining of cobalt offers an economic route for producing higher grades of cobalt from the type of concentrates and treatment processes available within ZCCM. The consistency of VIR cobalt quality has been confirmed by ZCCM and some of its alloy customers.

Jan 1, 1988

By Colin Dessemond

Since 1950, the traditional process has been dominating the production of lithium compounds from spodumene ores to sustain the lithium market because of its economic viability and the markets need for technical grade (99.5% purity) product. This traditional process includes thermal conversion, acid roasting and lithium leaching. However, this process has not been challenged and very few studies have tried to explain its limitation (95% lithium yield) or optimize the thermal treatment. Here, α to β spodumene conversion and lithium extraction were performed in a rotary kiln on a 2 mm to 2 cm spodumene concentrate instead of a micrometric one using a 1050 °C, 30 min conversion treatment and 250 °C, 30 min, 30% H2SO4 excess leaching treatment. X-Ray Diffraction analyses were performed on the converted material to determine the conversion rate by Rietveld analysis. It was observed after thermal treatment that the α-spodumene particles fractured and divided while the impurities remained compact. A sifting was performed after thermal treatment and it was determined that 65% of the initial mass became finer than 180 μm. X-Ray diffraction analyses and lithium content measurement were performed on both fractions and it was determined that the finer fraction had a very high lithium content of 3.24 wt%. Lithium extractions were performed on both fractions separately. While the coarser fraction’s lithium yield was only 61% the finer fraction’s lithium yield went up to 99% without any additional treatment. These observations may open more economical ways for the traditional process by potentially bypassing two third of costly steps such as grinding.

By Kimio Itagaki

The distribution ratios of Ag, Pb, As, Sb and Bi for the Cu2S-FeS or Ni3S2-FeS matte / FeOx SiO2, FeOx-SiO2-CaO or FeOx-CaO slag equilibration in a MgO crucible were determined experimentally at 1523~1573K under controlled partial pressures of S2 and O2 at given PSO2 of 10.1, 50.7 and 101.3 kPa (0.1, 0.5 and 1 atm) and be observed dependency of distribution ratio on the matte grade, SO2 pressure and slag basicity were analyzed on the basis of thermodynamics,

Jan 1, 2003

By Florian Kongoli

"Lime ferrite" slag with limited silica content has proven to be a valuable choice in the modem processes of copper smelting and converting due to several advantages that this slag offers compared to classical silicate slags. Nevertheless the liquidus surface of this slag has been experimentally measured only at low oxygen potentials such as in equilibrium with iron or near it and in air. Although most of the smelting and converting processes that use this slag occur at intermediate oxygen potentials, the liquidus surface of this slag is not known at these conditions and the effect of oxygen potential and silica has not been correctly understood. This has brought some confusion in literature as well as in the industrial practice. In this work the liquidus surface of the calcium ferrite slags has been quantified by the means of a new thermophysicochemical model and a new type of liquidus surface diagrams which are very convenient for any industrial process that uses calcium ferrite slags. These diagrams can be easily used to select the lowest liquidus temperature of calcium ferrite slags at a minimum cost and can help design several fluxing strategies in copper smelting and converting processes. The effect of the oxygen potential and silica is also quantified and important industrially related conclusions are drawn.

Jan 1, 2003

By Florian Kongoli

"Lime ferrite" slag with limited silica content has proven to be a valuable choice in the modem processes of copper smelting and converting due to several advantages that this slag offers compared to classical silicate slags. Nevertheless the liquidus surface of this slag has been experimentally measured only at low oxygen potentials such as in equilibrium with iron or hear it and in air. Although most of the smelting and converting processes that use this slag occur at intermediate oxygen potentials, the liquidus surface of this slag is not known at these conditions and the effect of oxygen potential and silica has not been correctly understood. This has brought some confusion in literature as well as in the industrial practice. In this work the liquidus surface of the calcium ferrite slags has been quantified by the means of a new thermophysicochemical model and a new type of liquidus surface diagrams which are very convenient for any industrial process that uses calcium ferrite slags. These diagrams can be easily used to select the lowest liquidus temperature of calcium ferrite slags at a minimum cost and can help design several fluxing strategies in copper smelting and converting processes. The effect of the oxygen potential and silica is also quantified and important industrially related conclusions are drawn.

Jan 1, 2003

By A. J. Schindler, F-P Sawyer, T. Logan, M. L. Shutey-McCann, R. M. Perry

"Test work on biooxidation pretreatment of low-grade refractory gold ores has been ongoing at Newmont Gold Company since 1988, including laboratory testing and pilot biooxidation heaps (360 to 23,000 tonne). Metallurgical results of the biooxidation process utilizing Thiobacillus ferrooxidans (T. ferrooxiddans) have culminated in the design, construction, and operation of a biooxidation demonstration facility. The facility has processed 708,000 tonnes of refractory ore, using a batched process with separate pads for biooxidation and ammonium thiosulfate gold extraction. Siliceous sulfidic refractory (SSR) and carbonaceous sulfidic refractory (CSR) ores are treated separately during biooxidation pretreatment unit operation. Following biooxidation, the ores are neutralization with lime and placed on oxide leach pads or stacked on the ammonium thiosulfate leach pad. Gold is leached with either cyanide for SSR ores or ammonium thiosulfate for preg-robbing CSR ores.This paper will only address the biooxidation pretreatment process of the SSR and CSR ores.AcknowledgmentsThe authors appreciate the cooperation and approval of Newmont Gold Company Carlin Operations management for its support and permission to publish this paper. The paper draws on efforts and assistance of the following people and several others which are to many to list who participated over the past five years in bringing this project to its fruition: Dr. James A. Brierley, Chief Microbiologist, Newmont Metallurgical Services; Dr. Rong-Yu Wan, Metallurgical Manager, Newmont Metallurgical Services."

Jan 1, 1997

By Gabriel A. Torma

This paper provides infonnation on selected technologies available for remediation of metal contaminated soils and industrial effluent solutions. Because some of the industrial sites are contaminated with organics (solvents, gasolines and oils), an effort has been made to introduce the most frequently used cost-effective cleanup methods, such as "bioventing" and "composting." The microorganisms involved in these processes are capable of degrading organic soil contaminants to environmentally harmless compounds: water and carbon dioxide. Heavy metals and radionuclides contaminated mining and industrial sites can be remediated by using adapted heap and dump leaching technologies, which can be chemical in nature or bio-assisted. The importance of volume reduction by physical separation is discussed. A special attention is devoted to the remediation of soils by leaching (soil washing) to remove heavy metal contaminants, such as chromium, lead, nickel and cadmium. Furthermore, the applicability of biosorption technology in the remediation of heavy metals and radionuclides contaminated industrial waste waters and acidic mining effluent solutions was indicated.

Jan 1, 1996

By Saeid Pournaderi, Ahmet Geveci, Ender Keskinkilic, Yavuz A. Topkaya

There are mainly three commercial nickel laterites in Turkey: Gordes, Caldag and Sivrihisar. The first two appear in Western Anatolia. The third one, Sivrihisar (Yunusemre) laterites have been found in the first decade of the millennium, in the Central Anatolia region of Turkey. Since then, mining facilities have been continued in Yunusemre. Calcination, prereduction and smelting of Sivrihisar laterites have been extensively studied and published. In the current work, some results of the studies related to characterization of Sivrihisar laterites will be presented.

Jan 1, 2016

By Animesh Jha, Catherine Davey

"Carbothermic reduction and nitridation reactions using synthetic kaolinite mineral were investigated for the formation of silicon based nitrogen ceramics. The temperature dependence of the reaction rate and its effect on phases formed are reported. The effect of the reactivity of carbon on the kinetics of formation of AIN and ShN4 is discussed. Using the standard Gibbs free energy values for the formation of nitrides and oxides of aluminium and silicon, a log po2 verses I/T diagram is constructed. The experimental data results are discussed and compared with the predicted phase equilibria. We also report the influence of sub-oxide gaseous species on the microstructure of the ceramic phases produced.IntroductionSynthetic kaolinite is a clay containing alumina, silica and water of crystallisation, and has a chemical formula 3(Al2O 3.2SiO2.2H2O). This mineral is relatively inexpensive and, is therefore an ideal candidate for use in the production of ceramic powder mixtures for example silicon nitride and aluminium nitride for composite material formation, When the mineral is heated, the water of crystallisation from the crystal lattice is lost via the 3(Al2O 3.2SiO2.2H2O) = 3(Al2O3.2SiO2) + 6H2O reaction. It has been shown [1·2j that on further heating to 1673K, the anhydrous kaolinite decomposes to a mixture of mulllte and silica, 3(Al2O3.2SiO2) = 3Al2O 3.2SiO2 + 4SiO2 which is consistent with the alumina-silica phase diagram, shown in figure 1.The binary alumina-silica phase diagram has a well-defined sub-eutectic immiscibility dome and this characteristic dernixing behaviour is reflected in the thermal decomposition of anhydrous kaolinite consequently the microstructural features resemble the spinodal decomposition process. It is well established that the spinodal decomposition process raises the nucleation frequency due to their low free energy barrier, (?G). The small magnitude of this barrier consequently promotes the evolution of a very fine microstructure. The process of spinodal decomposition is therefore expected to be influential during the reduction-nitridation of kaolinite minerals."

Jan 1, 1996

By Yu Yamashita

There have been increasing in melting recycled scraps in copper smelting processes, and thus growing interests in the chlorine behavior. In this study, chloride dissolution in FeO-Fe2O3-SiO2slag (SiO2sat.) at 1523 K has been measured with varying in PCl2 from 1.13x10-8 to 1.30x10-7atm. and the oxygen partial pressures encountered in typical copper smelting furnace, i.e. PO2=10-8 to 10-10 atm. Discussion is made on the chloride capacity of FeO-Fe2O3-SiO2 slag in terms of its characteristics and the dissolved chlorine species. It has been shown that the mostreasonable dissolution reaction and chloride capacity can be expressed by the following reactions, where chlorine dissolves in the form of Cl-; here, aO2-, oxygen ion activity, is shown a function of oxygen partial pressure in the atmosphere. [ ]

Jan 1, 2006

By Hiroyuki Matsuura

Treatment of electric arc furnace (EAF) dusts has become an important issue from the viewpoint of the environmental protection and recycling of variable resources because these dusts contain considerable amount of zinc and lead. A new recovery process of these metals has been proposed, in which the metals in the dusts react with waste polyvinyl chloride to form metal chlorides. Therefore, it is important to clarify the physicochemical properties and behaviors of zinc, lead and those chlorides and oxychlorides. In the present study, the kinetics of chlorination of ZnO, PbO and ZnFe2O4 mainly contained in the EAF dusts were investigated at 1023 K to 1273 K with Ar-O2-Cl2 gas. Based on these results, the selective chlorination and evaporation process of zinc and lead from the mixture of Fe2O3-ZnFe2O4-ZnO-PbO was examined and the high efficiency of selectivity has been demonstrated.

Jan 1, 2006

By J. M. Skeaff

As much as 100% of the gold and 67% of the silver in a sulphur-bearing hydrometallurgical leach residue have been transferred to copper metal at copper smelting temperatures by dissolving the partially calcined residue in an iron-bearing slag maintained in equilibrium with the liquid copper metal and matte phases. The precious metals can then be recovered by conventional refining techniques. Copper can be recycled at least four times without any detrimental effects on gold and silver transfers and recoveries. Apparent copper recovery in the .process can be over 100% because of the copper content of the residue. Based on slag analys.es, the overal1 recovery of gold in the copper metal and matte phases varies from 94% to 100% under all conditions investigated. On the? same basis, silver recovery varies .from 9S% ?to 99% under optimum conditions, but is only 4S% to 73% under other, less attractive conditions. Unaccounted for silver losses of' about 30% make it difficult to determine the major factors affecting ?silver transfer and recovery. A method for implementing the technology on a commercial scale at a Canadian copper/zinc smelter has been proposed. A preliminary economic assessment and comparison of the proposed pyrometallurgical process with conventional cyanidation indicates that either process is economically attractive for recovering gold and silver from leach residues. Although the capital costs are higher, the pyrometallurgical process is simpler, has higher recoveries, lower operating costs and no .potential environmental problems related to cyanide disposal.

Jan 1, 1989

By Carlos Ortiz

The Huelva Flash Smelting Furnace was commissioned in September 1975. The Smelter and the Acid Plant were expanded in 1995 to their present capacity of 300,000 tpa new copper equivalent and one million tonnes of concentrate per year. During these years of operational experience, most of the initial practices have been reviewed, process control has drastically improved and main process equipment has been modernised. The fourth Flash Furnace campaign lasted 9 years (1995-2004) during which 8 million tonnes of concentrate were smelted. Increasing sulphur content in concentrates and new environmental requirements imply new challenges for smelters to keep production and operation costs down. This paper is an overview of the modifications and improvements carried out in the 2007 general shutdown in Smelter and Acid Plants. Al

Jan 1, 2008

By Osamu Yamamoto

In antibacterial evaluation of carbon-ceramic composites, we prepared two type composites with emphasis on carbon-ZnO system; one was porous carbon materials containing ZnO nano-particles and another was porous ZnO coated with carbon thin film. Porous carbon samples containing ZnO at highly dispersed state were prepared by carbonizing the resin exchanged by Zn2+ ion. Porous ZnO coated with carbon thin film was obtained by the pyrolysis of poly (vinyl alcohol). Antibacterial activity of these composites obtained was evaluated by measuring the changes in electrical conductivity with bacteria growth. The antibacterial activity on the composites increased with the increase of t he amount of ZnO in composite and decreased with the increase of carbonization temperature. The antibacterial activity for Staphylococcus aureuswas found to be stronger than that for Escherichia coli. No activity of the carbon samples without ZnO was observed. The occurrence of antibacterial activity was supposed to be due to the generation of hydrogen peroxide from ZnO in composite. In the present work, antibacterial activity of carbon-ZnO composites was studied in the details.

Jan 1, 2006

By A. Haxhiaj, Mitovica, E. Haxhiaj

"The paper discusses problems encountered during the release and possibility of using the thermal gas quantity Mathematical models are used to calculate the positive thermal effects of the gases and losses of thermal quantity with gases in the melting process of electric furnaces. The paper discusses in details the percentages of CO, CO2, H2S, O2 and the humidity in gases and their impact on the technological process in electrical furnaces in Drenas. The paper also confers the quantity and temperature of gases, the transfer of thermal quantity and dust with gases in the environment. The paper presents the percentage of humidity in the load which is added in electric furnace for melting and its impact on thermal and environmental balance in the technological process of melting in electric furnaces. Key words: Furnace, load, temperature, humidity, gases.IntroductionNickel easily reacts with gases in the atmosphere of the furnace in which the nickel ore is processed. Such reactions can explain challenges in producing high quality nickel. Reductive atmosphere with the surrounding gases composed of sulphurous anhydrite has harmful effects on the production of nickel. This is mainly due to solubility of hydrogen as well as nickel oxide in the melted metal. Nickel reacts with carbon monoxide and forms carbide of nickel and nickel oxide which dissolve in the melted metal. Carbon monoxide also dissolves in the melted metal. The presence of carbon dioxide and water vapor in the atmosphere of the furnace impact the decrease of acidity in reductive atmosphere of the furnace. The carbon dioxide reacts with nickel and forms nickel oxide and carbon monoxide. Water vapor reacts with nickel and forms hydrogen and nickel oxide that have negative impact on the structure of nickel and its alloys. In this paper the analytical and experimental analyses are proposed that lead to minimization of the negative effects of gasses and humidity in the melting process. As the practical example, the electrical furnace in Drenas is analyzed.1. The Load and Its CompositionThe basic function of the rotational furnace is drying and reductive roasting of the ore which directly is loaded into the electrical furnace for melting. It is important to mention that the degree of roasting and pre-reduction of iron-nickel oxides is reached if the roasting process of the load in the rotational furnace is done at the temperature of 900°C to 1000°C, with the reductive atmosphere in the furnace and with minimal amount of oxygen in the processing gas. The optimal process of roasting and pre-reduction of the load in its mass is around 13 wt%. With the removal of the humidity and the sterile pare of the ore, with the positive impacts in utilization of the thermal and electrical energy in the melting process in electrical furnaces."

Jan 1, 2013