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By Charles L. Richman

The effect of the addition of Silver Sulfide on the rate of Chalcopyrite (CP) of Sulfuric acid (H2SD4 leaching is discussed, Although Ag2S in an expensive addition, a theoretical explanation of it's use will aid in the development of a economic substitution. We have used cyclic voltammography to show the presence reaction species at different potentials. Cyclic Voltammography maps the surface reaction current peaks on CP, to regions on the CP Phorbaix diagram. AC Electro-lmpedance spectroscopy (EIS) models the surface impedance properties, which control the rate of electron and ion transfer, and the surface kinetic reactions, with and with out light. EIS and other measurements show that AgCuS u Photo-reactive material- The EIS results are compared with the SEM and EDXA results to show the presence of diffusion pores, and diffusion controlled reactions during CP leaching without the addition of silver sulfate. We hypothesize that AgCuS is an ionic conductor like Ag2S. EIS shows an imposed negative leaching rate greatly. Our theory shows how the formation of Silver Copper (1) sulfide layer at open circuit potential gives an effect similar to negative potential, that is enhanced with illumination. We verify that AgCuAS is an N-type semiconductor that forms a diode type junction with the electrolyte with the Mott-Schoottly relation.

Jan 1, 2001

By Mao Chen, Baojun Zhao, Zhixiang Cui, Leonel Contreras

Viscosity is one of the important physiochemical properties of metallurgical slags which is important for slag tapping, metal loss in slag, freeze lining and fluid dynamics. High temperature viscosity measurements are time- and cost-consuming and the number of experiments is limited. Viscosity model is an effective way to predict the viscosities of the complex slags at high temperature. However, a reliable viscosity model can only be developed on the base of accurate experimental data. A unique high-temperature viscosity measurement apparatus developed at The University of Queensland enabled accurate viscosity data to be measured for the “FeO”-SiO2-CaO-MgO-Al2O3 system in equilibrium with Fe. An accurate viscosity model has been developed based on Eyring’s theory and extensive viscosity measurements. The viscosities of copper smelting, converting and cleaning slags over a wide range of compositions and temperatures can be predicted and applied in the process control.

Jan 1, 2016

By Yogeshwar Sahai

Submerged gas injection into melts contained in furnaces, ladles, or similar transfer vessels is commonly used in industrial practice. In this review paper, conditions leading to gas bubble formation at the nozzle are first summarized. The increasing gas injection rates and other conditions, such as nozzle size, lead to regimes which are commonly known as "bubbling" and "jetting". These are explained. The gas/melt interactions result in energy transfer to the melt. In recent years, a large number of researchers have investigated the relationships between the energy density and the mixing times. Their work is reviewed, and the mixing mechanisms is described. Finally, computational approaches of modeling submerged gas injection are briefly presented.

Jan 1, 1993

By lchiro Aoi, Hideo Nakae, Makoto Yoshida, Makoto Ishino

"The influence 6f gravity on the microstructure of unidirectionally solidified Cu-Pb monotectic, Ag-Si and Fe-C eutectic alloys is studied. In order to examine the influence of gravity in a lg environment, both the upward (opposite to direction of gravity) and downward (direction of gravity) unidirectional solidifications are carried out. The results are as follows: (1) For the upward solidified Ag-Si eutectic alloy, the eutectic Si continuously grows. On the other hand, in the downward solidified Ag-Si alloy, the Si grows discontinuously and disperses into the ex-Ag matrix. (2) No morphological difference in the eutectic growth is observed between the upward and downward solidified Fe-C eutectic alloys. (3) In the case of the upward solidified Cu-Pb monotectic alloy, a banded structure, which consists of Pb-rich layers and Cu-rich layers, is observed. However, such a banded structure -is not observed in the downward specimen. (4) The banded structure is not found in the upward solidified Cu-Pb-0.05 mass % Al and Cu-Pb-0.1 mass % Al alloys. In the Cu-Pb-0.05 mass% Al alloy, a fibrous -L 2 phase grows continuously parallel to the growth direction at low growth rate. Only 500 mass ppm addition of aluminum induces the morphological change of the monotectic L2 phase.IntroductionThe influence of gravity on the solidification of eutectic and monotectic alloys has been investigated in microgravity environments [l-9]. The purpose of these studies was to obtain a homogeneous microstructure of eutectic or monotectic alloys, most of which alloys tend to solidify with macro-segregation under gravity. However, in most of the previous experiments, e.g., in free fall systems, in aircraft or in space laboratories, the growth rate was too high to realize a planar solid/liquid interface. This would be due to the limited time for solidification. Thus, it was difficult to examine the influence of gravity on the planar coupled growth of the eutectic or monotectic alloy. In this study, both the downward U.D.S. (unidirectional solidification by gravity) and upward U.D.S. (opposite direction to gravity) are carried out in order to examine the influence of gravity on the coupled growth in a lg environment [l0, 11]. In the case of the downward U.D.S. using the current Bridgman method, the molten alloy must be confined between the crucible and the solid."

Jan 1, 2000

The effect of change in slag composition upon metal losses to the slag and the relationship between slag composition and slag matte separation was investigated at 1400°C. The synthetic slags containing CaO, MgO, SiO2,, A1,0, and FeO were similar to those employed in the electric furnace smelting of sulphide Cu-Ni concentrates containing PGM (Precious Group Metals) from the Merensky Reef of South Africa. The matte with a grade of 9.3% Cu and 16.0% Ni was a typical electric furnace product. The results indicated that the Cu and Ni solubility in the slag increases with the increase of the basicity ratio and CaO and MgO contents of the slag. At constant CaO/MgO ratios the rise in basicity decreases the metal losses. When FeO and SiO2 contents of the slag are kept constant, the substitution of MgO with CaO decreases the metal losses. The relationship between slag composition and matte-slag separation was found to depend primarily on the basicity ratio and the FeO content of the slag. The net effect comes from a strong interaction of the two in such a way that increasing basicity and decreasing FeO contents deteriorate the clean separation of the two phases.

Jan 1, 1994

Physical and chemical properties of the salt flux phase play a significant role in the recycling of UBC in Aluminum melting processes. Particularly knowledge of several properties such as salt vapor pressure, melting temperature, loss of aluminum, corrosion of refractories are useful for the process control decisions in order to attain a good quality of aluminum produced. A literature review and analysis of several salt flux systems for the selection of a flux for the Aluminum melter (low temperature natural gas bath melting) process were made. Based on these analysis two salt flux systems are recommended for further studies. These are NaCl?KCl?LiF system and NaF?LiF?KCl system with small amounts of other salt additives. Application of these fluxes to Al industrial processes are discussed.

Jan 1, 1996

By R. Nilsson

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

Jan 1, 1996

By Katsuya Kase, Kaname Takeya, Keaji Ohmori, Yoshiyuki Asakawa

"The reduction-diffusion process (the R-D process) using Ca as a reducing agent has been practiced in industry in the production of the SmCos type, the Nd-Fe-B type and the 1b-Fe-Co type magnetic materials. The advantages of the R-D process are the generally high yield of rare earth metals and the single-stage conversion of a mixture of oxides and metal powders into a product of rare earth alloy powders. On the other hand, one of its disadvantages is the slightly high contents of oxygen and calcium. This disadvantage is remarkable in the Nd-Fe-B type. Singe-phase Nd2Fe14B alloy powders with low content of 0 and Ca, is obtained by choosing appropriate raw materials and performing the R-D process in a controlled way. These alloy powders are very suitable for the production of Nd-Fe-B sintered magnets and expected higher magnetic properties by adopting advanced magnet production method.IntroductionThe hard magnetic rare earth transition metal intermetallics, especially, have attained considerable technical importance. Examples are the alloys based on the intermetallics SmCo5[1], SmC017[2], NchFet4B[3], or the recently developed alloy SnuFe11Nx[4]. The reduction-diffusion process using Ca as a reducing agent has been well known as an economical method of producing rare earth based magnet materials[5]. The reduction-diffusion process has been practiced in industry in the production of the SmCos type, the Nd-Fe-B type and the 1b-Fe-Co type magnetic materials. The advantages of the reduction-diffusion process are the generally high yield of rare earth metals, the single-stage conversion of a mixture of oxides and metal powders into a product of rare earth alloy powders, the elimination of the crushing process of the alloy ingot, the inessentiality to special equipment, etc. On the other hand, one of its disadvantages is the slightly high content of oxygen and calcium. This disadvantage is remarkable in the Nd-Fe-B type. An outline of basic studies of the reduction-diffusion process was reviewed from the particular viewpoint of the production of magnet materials by Ogawa [6]."

Jan 1, 1998

By Shun Myung Shin, Dong Hyo Yang

Cobalt is recovered from square type of spent lithium ion batteries (LIBs) containing 5~20 % Co, 5~7 % Li, 5~10 % Ni, 15% organic chemicals, and 7% plastics together with Cu, Al, Fe, and Mn. The waste LIB was prepared by physical treatment. After screening, the crushed LIBs were separated to +8 mesh, -8/+16 mesh, and -16 mesh powder. Among these, -16 mesh powder was selected for leaching. The leaching test was investigated at 2 M H2SO4, 6 vol.% H2O2, reaction temperature 60 ?, agitation speed 300 rpm, solid/liquid ratio 50 g/ 500 ml, reaction time 1 h. The leaching efficiency of cobalt was more than 99 % and its concentration was 24.9 g/L. For removing of impurities such as copper, iron, and aluminum in the leaching solution before cobalt solvent extraction, the impurities were eliminated by pH control with alkali solution. For selective extraction of cobalt, the aqueous phase removed impurities was equilibrated with different volumes of 0.4 M Cyanex 272 saponified of 50 %. Extraction efficiency of cobalt was about 80 % at first step. Separation coefficient (ßCo/Li) of cobalt and lithium extractions was 206.5. Over 9.0 % of pure cobalt sulfate solution was obtained after stripping with H2SO4 solution.

Jan 1, 2008

By L. J. Davies

Refractories usage in furnaces for the extraction of nickel from both sulphides and lateritic ores is reviewed. Recent changes in raw materials and basic brick qualities developed to meet the increasing demands of existing and new processes are outlined. Examples of used brick examinations to establish mechanisms of wear are given. The importance of physical and chemical properties are discussed. The use of simulative laboratory testing to aid in refractories development and selection is described.

Jan 1, 1988

By Chen-Ming Kuo, Esher Hsu

"Under the 4-in-1 recycling system, Taiwan producers and importers who using packaging containers have responsibility to pay the recycling fees for recycling the waste packaging containers they produced or imported; while the collectors/recycling plants who collect/sort/recover waste packaging containers receive subsidy for conducting recycling. A reasonable pricing for recycling charge and subsidy is a way for sustainability of the recycling. The objective of this study is to provide an amending mechanism for product charge and recycling subsidy in response to the social economic changes. This study employs a regression analysis and cost adjusting model to link the factors used for calculating product charge and recycling subsidy on recycling waste packaging containers with socio-economic indicators, raw material prices, wholesale prices, and secondary material prices. Study results provide estimated models to EPA in Taiwan for amending product charge and recycling subsidy in response to the social economic changes.IntroductionUnder ""4-in-1"" recycling system in Taiwan, waste packaging containers are officially announced to be recycled. The waste packaging containers announced to be recycled include iron cans, aluminum cans, glass bottles, plastic containers, paper containers, aluminum foiled paper packs. In order to compensate the recycling system, EPA charges associated manufacturers and importers for recycling fee and subsidies recyclers to create the economic incentive for raising recycling performance. Basically, the budget for subsidy recyclers is from the recycling charge. That means if we want to increase recycling efficiency by increasing subsidy to recyclers then the manufacturers and importers have to pay more for reaching financial balance of recycling foundation. The benefit of recyclers and fee payers are always conflicted. The recycling charge and subsidy is thus argued by fee payers and subsidy receivers all the time. A reasonable pricing for recycling charge and subsidy is the only way to keep the recycling system sustainable. Moreover, a suitable mechanism has to be changed along with the changing social economic condition. The recycling performances and effectiveness of this recycling system is also highly dependent on the pricing mechanism. This study intends to provide an amending mechanism for product charge and recycling subsidy in response to the social economic change. Related previous studies about recycling system in Taiwan with its performance include Hsu and Kuo (2002, 2005), Bor, Chien, and Hsu (2004) and Hsu (1999). Hsu and Kuo [1] estimated total production values of recycling and evaluated the performance of recycling performance based upon the estimated production values."

Jan 1, 2011

By Carlos Maurício Fontes Vieira, Sergio Neves Monteiro, Diogo Neves Henriques

"This work evaluates the effect of incorporation of an ornamental rock waste into an industrial clayey body used for roofing tiles fabrication. Formulations with 0, 10, 20 and 30 wt.% of waste were prepared by replacing the sand in the industrial clayey body. The plasticity of the formulations was determined by the Atterberg limits. Specimens were fabricated by 18 MPa press-molding and then fired from 850 to 1100oC. The specimens were tested to determine the water absorption, linear shrinkage and three points bending flexural strength. The results indicated that the waste improves the extrusion performance of the clayey body by decreasing its plasticity. The use of the waste was beneficial to the water absorption and mechanical strength of the fired clayey ceramic at temperatures above 1000 ° C.IntroductionOrnamental rock is a natural resource available in the municipal area of Santo Antônio de Pádua and located 150 km from the city of Campos dos Goytacazes, northe of state of Rio de Janeiro, Brazil. Intense industrial activity related to ornamental stones, especially gneisses, is traditionally occurring in the region. After mining, the flagstone is submitted to sawing to obtain blocks and then, after a manual operation, the final products are small flagstones [1,2]. During the sawing operation, a sludge composed of water and fine particles of rock is generated. A monthly production of 1000 tons of ornamental rock waste is estimated to be produced at Santo Antônio de Pádua. The final disposal of this waste has brought serious environmental problems. Since most industries do not have an adequate sludge treatment, the waste is contaminating the soil and underground waters as well as obstructing rivers and lakes.Ceramic bodies industrially fabricated in the municipal area of Campos dos Goytacazes, 280 km from the city of Rio de Janeiro, are still empirically elaborated using a mixture of local clays. These clays are predominantly kaolinitic mineral, associated with high plasticity. Due to the excessive plasticity of the ceramic bodies, it is common to have dimensional defects in the final products after the drying and firing processes. Moreover, the kaolinitic structure and the presence of aluminum hydroxide confer a refractory behavior to the local clays. This impairs sintering during the firing operation. In the case of clay ceramics for civil construction, this results in greater porosity associated with elevated values of water absorption and low mechanical strength [3,4]. To avoid these problems, it is necessary to reformulate the ceramic body composition. The addition of both non-plastic materials to reduce plasticity and fluxes to condition the refractoriness is a possible alternative."

Jan 1, 2008

By Shengli Wu, Laixin Wang, Minyin Kou, Xinliang Liu, Weidong Zhuang, Yujue Wang

COREX process has obvious advantages in environment protection but still has some disadvantages, for example, it has a higher sulfur content of hot metal than blast furnace. In this paper, the thermodynamics and dynamics of desulfurization have been investigated to obtain the main operation parameters related to the mass fraction of sulfur in the hot metal. In addition, statistical analyses have been carried out to study the relationship between operating parameters and sulfur content of COREX hot metal based on actual plant data. It has been found that the mass fraction of sulfur in hot metal is significantly influenced by the C content in hot metal, MgO/Al2O3 in slag, the concentration of MgO in slag, the temperature of hot metal and binary basicity (R2).A linear model has been developed and subsequently used for reducing the mass fraction of sulfur in hot metal, improve the quality of hot metal and contribute to low carbon ironmaking.

Jan 1, 2016

By Takeo Fujino, Nobuaki Sato, Junichi Hasegawa, Masato Nakazawa, Kohta Yamada

"Tantalum oxide thin films were deposited on quartz substrates by laser ablation of Ta2O5 target using Nd:YAG pulse laser. Deposition-was observed when a laser light energy higher than 200 mJ and its repetition rate higher than 3 Hz. A thin film of 0.1 µm thickness was obtained by the ablation using a laser light of 300 mJ and 6 Hz for 2 sec. The thickness of the film increased with increasing energy, repetition rate and irradiation time of laser. By the SEM observation, it was found that many island-like particles were deposited on quartz substrate forming a thin film. The obtained thin film, which was identified as ? Ta-O by X-ray diffraction, was oxidized to Ta2O5 by the heat treatment in air at I273 K for 3 h.IntroductionTransition metal oxides have a potential to show special characteristics in electrical, magnetic and/or optical properties. When such compounds are fabricated in the form of thin film, the special properties would be improved or new characters would appear in comparison with bulk materials. Tantalum penta-oxide is widely used as a capacitor since Ta2O5 shows high dielectric constants up to high temperatures. The tantalum solid capacitor has been fabricated by the electrical oxidation of sintered Ta metal cylinder followed by MnO2 film coating. However, further improvements, reduction and layered structure formation, are required for compacting the devices. The layered structure of thin films would be applicable for the above requirements. The formation ofTa2O5 film by low pressure CVD1), photo CVD2) and magnetron sputtering3l were reported. The laser ablation -method is one of the most convenient techniques for the deposition of thin films from their compounds, such as oxides. Formation of Ta2O5 film by pulse laser deposition (PLD) method using ArF excimer4), Nd:YAG (533nm)5) and TEA CO2 6 lasers was reported. In these PLD studies, ablation was carried out in relatively high oxygen pressures resulting in formation of Ta2O 5 film. In this paper, the deposition of tantalum oxide thin film by the laser ablation of Ta2O 5 using Nd:YAG pulse laser was examined at a viliety oxygen pressures ranging from 10-8 to 10 Torr. The morphology of the films was also investigated in relation with substrate temperature and oxygen pressure."

Jan 1, 2000

By John Petersen

Heap bioleaching technology has become well established for the exploitation of copper sulfide ores. Still, in many operations the rate of copper extraction is rather slow, often taking two years or more to recover 80% of the copper. Chalcocite, the most common secondary copper sulfide, leaches by a two-stage mechanism. The first stage is rapid, whereas the second stage has a high activation energy and proceeds slowly at ambient temperatures. Nonetheless, this rate is still considerably faster than what is typically realized in a full-scale heap. A comprehensive column bioleaching study of a chalcocite ore has shown that the chalcocite columns are leached in a zone-wise fashion. The first zone corresponds to the first stage of chalcocite leaching, where all ferric produced by the bacteria is immediately consumed and all acid entering with the feed solution is consumed within a relatively narrow band. The second stage of chalcocite leaching proceeds much more slowly in the wake of the first stage, within a zone that grows gradually over the entire length of the column. The overall rate of leaching is thus determined by the rate of acid supply into the column rather than by mineral or bacterial kinetics, at least until the entire column is engaged in second-stage chalcocite leaching. In full scale heaps, there is evidence to suggest that solution distribution favours channelling between relatively large clusters of material which are exposed only to stagnant solution. Reagents have to migrate into such clusters by diffusion, which retards the delivery of acid dramatically. Thus, we believe that the rate of chalcocite oxidation in heaps is governed by sideways diffusion rather than downward migration. Column experimental results have been reproduced with a comprehensive heap-modelling tool. The model predicts that by simply changing the length of the average diffusion channel from column conditions (a few cm) to heap conditions (tens of cm), extraction times can change from weeks to years under otherwise identical conditions.

Jan 1, 2003

By Raj P. Singh

Applications of cementation in the recovery of metal ions from process solutions have been known for a long time. Cementation reactions involve electrochemical precipitation of a noble metal from solutions of its salts on a more electropositive metal which, in tum, progressively dissolves. For example, addition of zinc metal powder in a solution containing zinc and cobalt ions would allow for the precipitation (separation) of cobalt according to the following chemical reaction. This paper pertains to the recovery of cobalt from cobalt process solutions via a cementation reaction on aluminum shavings (metal scraps from cans etc). Specifically, we report on the characterization of cobalt process solutions, a by-product obtained from cobalt chemicals, and the kinetics of cobalt, nickel and manganese cementation from process solutions on aluminum shavings.

Jan 1, 2000

By V. L. Stolyarova

As part of an effort to develop the fluoride electrolysis route for the production of rare earth metals and alloys, a study of the thermodynamic properties of DyF3 has been carried out by Knudsen cell mass spectrometry. A quadrupole mass spectrometer QMS 420 was used in conjunction with the Knudsen cell arrangement. The experiments were carried out in the temperature range 1280-1440 K. Vaporization was carried out from platinum, molybdenum and tantalum cells. The Dy*, DyF+, DyF2+ fragment ions and the DyF3 parent ion were identified in the mass spectrum of the DyF3 vapour. The DyF, vapour pressure was obtained by the complete isothermal vaporizadon method as well as the ion current comparison method, and the enthalpy of sublimation of DyF3 was evaluated. From the DyF3 vapour pressure data obtained at different temperatures, the enthalpies of formation of DyF3 in the gaseous as well as condensed phases have been evaluated. The experimental data are compared with the thermodynamic information available in literature.

Jan 1, 1995

By Baozhong Zhao

The direct smelting of copper concentrates to copper metal in a single furnace offers environmental and energy advantages over conventional two-stage copper smelting processes. However, the direct copper making results in unacceptably high level impurities (As, Sb and Bi) in the anode copper. Experimental studies have shown that it is possible to remove these impurities from molten copper by injection of sulfur-hexafluoride. This paper discusses the experimental findings on the influence of various factors on the rate of removal of impurities, such as the impurity inter-effects, initial oxygen content in the metal and injection rate of SF6.

Jan 1, 1995

By P. Cowx

The carbothermic reduction of zinc oxide rich Electric Arc Furnace baghouse dust in the Tetronics transferred arc plasma furnace to produce a non-toxic slag and a metallic zinc product is described. In particular, the operation of the zinc splash condenser coupled to the plasma furnace is examined and the effect of process variables on zinc recovery is discussed.

Jan 1, 1990

By Marcela Morvová, Mário Janda, Morva Imrich

"The possibilities of greenhouse gas mitigation using various methods are brought out. The special case of utilization of mixture of CO2 with other greenhouse gases in a synergetic way inside non-thermal plasma based system is described in detail.Measurements on pilot system comprising pyrolysis chamber as alternative energy system (production of hydrogen and liquid tar) were made for various biomass and waste as the input material. The exhaust from this system was treated with non-thermal plasma gap suitable for up to 650Nm3/hour of exhaust gas flow. Condensable portion of exhaust is liquefied in distillation unit; produced hydrogen is stored on-line inside nano sized carbon of our own production.The CO2 removal efficiency varies depending on exhaust composition between 45 to 98%. Other oxides as CO, NOx, SOx and several hydrocarbons and VOC are also removed. The main product connected with CO2 removal is a solid powder of proteinoid nature. There exist strong probability, that precursor of the origin of life on the Earth from primary atmosphere were formed in the similar way as it is present in the electric discharge system used. Our system is equipped with on-line as well as ex-post analysis of all forms of products. We have also developed a system for recuperation of all forms of produced heat. It is stored inside as latent heat of waxes.IntroductionNatural greenhouse effect on the Earth is caused mainly by water vapour with the average absolute concentration about 4%. Other gases able to absorb long-wave radiation and thus this causing greenhouse effect are CO2, CH4, N2O, halocarbons and as precursors ozone and NOX. Some of them we produce and introduce into atmosphere in large quantities during production of energy and in transport. This factor leads to permanent increase of average temperature of air, sea and oceans, so called global warming.Nowadays large amount of data exists showing that the temperature of Earth in the last 150 years has been continually increasing. It represents about 03°C per ten years and the most of climatologist believe, that the increased concentration of greenhouse gases in the atmosphere is responsible for this effect.The most important greenhouse gas is carbon dioxide CO2. Majority of CO2 emissions comes from electric power stations working with fossil fuels, cars and industry. Burning of fossil fuels contribute up to 80% to world wide anthropogenetic emissions of CO2."

Jan 1, 2010