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By Yan Fu, Chuanlin Fan, Xiujing Zhai, Yongfeng Chang, Binchuan Li

"The mechanism of the selective chlorination of nickel and cobalt in reduced limonitic laterite was investigated. Reduced ores were obtained from the reduction roasting of a limonitic nickel laterite. The thermal decomposition of related chlorides and the selective chlorination of the reduced ore were carefully studied using Differential Thermal analysis - Thermogravimetry (DTA-TG), X-Ray Diffraction and chemical leaching methods. In the temperature range of 300 - 500 °C, aluminum chloride hexahydrate was chosen as chloride agent. During the selective chlorination, reduced ore was partly chlorinated by hydrogen chloride generated from the thermal decomposition of chloride agent. Then the oxydrolysis of ferrous chloride re-generated hydrogen chloride was used to further the chlorination. Finally, iron was mostly rejected as hematite, while nickel and cobalt were selectively chlorinated. More than 91 %Ni , 90%Co and about 4%Fe in the chlorinated ore was extracted using a water leaching method.IntroductionLimonitic nickel laterite is an important nickel reserve, which is rich in iron in the form of goethite and has low contents of magnesium, aluminum, silicon, and other elements. Goethite is the main nickel-bearing mineral in the laterite [1]. Nickel is generally present in goethite in three modes: (a) associated with amorphous or poorly crystalline goethite, (b) weakly adsorbed to the crystalline goethite surface, and ( c) as lattice substituents [2]. In addition, cobalt in limonite was found to be associated with a manganese phase rich also in nickel [3]. These results indicate that the extractions of nickel and cobalt are highly dependent upon the degree of the decomposition of the nickel, cobalt-bearing minerals.For the selective extraction of nickel and cobalt from limonitic laterite, the ore is usually processed by hydrometallurgical methods, including high pressure acid leaching (HPAL) [4] or reductive roasting - ammonia leaching (Caron process). However, there are still some disadvantages in these processes, such as the expense of autoclaves and scaling problems in HP AL [ 4, 5], and relatively low overall metal recovery, large energy and reagent requirements for the Caron process."

Jan 1, 2011

By Henrique Ventura Oliveira

Continuous casting is the most important process for solidification of steels. In this process, the fluid flow pattern in the tundish and in the mould have significant effect on the product quality. Problems associated to fluid flow in the tundish include surface turbulence, ?short-circuits?, formation of dead zones and vortexing. During grade changes, mixing in the tundish plays a significant role in determining the length of the intermixed slab. All these flow aspects can be studied by means of mathematical and physical models. In the last years, numerical simulation of fluid flow has become a very popular tool in the analysis of the performance of continuous casting tundishes. In setting-up these numerical simulations, special care should be taken in choosing the appropriate mesh distribution, the interpolation scheme, the adequate location of the inlet boundary and the turbulence model. In the present paper, turbulent fluid flow in different configurations of tundishes was simulated. Different turbulence models were used in the simulations. Residence time distribution (RTD) and mixing curves during grade changes were predicted and compared to results obtained in physical models. The performances of the different turbulence models were evaluated. For the tundishes that have been studied, the performances of the different turbulence models tested in the present work were similar. There is no evidence that any of the models provided sustained improvement when compared to the well-established standard k- model. All turbulence models tested presented limitations in simulating flows under low turbulent Reynolds numbers.

Jan 1, 2006

By Leijun Li, M. M. Mahapatra

"A three-dimensional finite element model with moving heat source was developed for pulsed-laser powder deposition (PLPD) process. Experiments were conducted to study the repair of superalloy components using the PLPD process. During the experiments, IN 625 powder was deposited on a superalloy substrate similar to IN 738. The process was modeled using three-dimensional finite element analysis. Element birth and death technique was used in the finite element model for simulating the deposition of powder layer on the substrate. A moving distributed heat source was used in the thermal model for realistic simulation of the process. Temperature dependent thermal material properties including enthalpy were used for the powder and the substrate in the transient thermal analyses. The fusion zones and peak temperature distributions of the deposits were predicted from the transient thermal analyses.IntroductionPoor weldability is a critical issue of superalloy repairing. The microstructural directionality of the superalloy components are disrupted when repaired by the fusion welding processes. Currently there is no widely accepted method to economically and reliably repair directionally solidified superalloys components. Pulsed laser powder deposition process (PLPD) is a promising repairing technique as the substrate is not severely affected by the heat source.In this study PLPD technology is used as the tool for superalloy repairing. In most of the land based turbine engines the directionally solidified nickel based superalloy similar to IN 738 [1] is used as the bucket material. The turbine engine blade tips are subjected to a combination of extreme operating conditions and corrosive environment. The tip of the nickel based turbine engine blades can be repaired using IN 625 material as suggested in the literature [1-2]. IN 625 is considered to be ductile and strong enough for the purpose of Ni based turbine engine blade tip repair[1-2]. During the present PLPD investigation, IN 625 powder was used as the deposit material on an experimental super alloy substrate similar to IN 738 superalloy used as the cast superalloy for the turbine engine blades."

Jan 1, 2012

By Dachun Liu, Yifu Li, Baoqiang Xu, Yongnian Dai, Bin Yang

"The removal of impurity arsenic from crude tin is one of the major problems in the process of tin refining. Through a thermodynamic analysis on vacuum refining process of crude tin, the vapor pressure of impurity arsenic under different temperatures can be obtained, which demonstrates that it is possible to separate tin and arsenic by the vacuum refining process. This paper attempts to verify the behaviors of impurity arsenic. The experiment result shows that through vacuum distillation, crude tin with 0.16% arsenic can be refined from crude tin with 0.96% arsenic, and about 50% impurity arsenic can be collected in the form of metallic arsenic.PrefaceThe crude tin obtained by the reduction process is insufficiently pure for most applications, even smelting from tin concentrate. Arsenic is a common impurity in crude tin and also one of the predominant elements to affect tin performance. Arsenic is a poisonous metal that has long been linked to an increased risk of cancers, diabetes, thickening of the skin, diseases of the liver and digestive complications, so there is a mandatory limit on the amount of arsenic (<0.015%) in tinfoil wrapper and tin layers for food packaging. Arsenic causes a poor appearance and plasticity, and increases viscosity. The impurities content of crude tin fluctuate over a wide range; a lot depends on composition of tin ore concentrate, treatment method and technological process before reduction smelting. And the content range of arsenic is usually 0.5~4%, but it is higher in some factories."

Jan 1, 2012

"An experimental study has been performed to investigate the dispersed phase holdup induced by a high-strength submerged gas injection in a bottom blown air-stirred one-seventh water model of CLU (Creusot-Loire Uddeholm) reactor using two different tuyere configurations. The air flow rates varied from 0.00599 m3/sec to 0.01312 m3/sec. In these series of experiments, water height and kerosene height were kept constant at 0.23m and 0.02m respectively. The dispersed phase holdup was determined at various gas flow rates, and tuyere orientations by using water and kerosene.The dispersed phase holdup increased with gas injection rate and decreased with vertical distance from the original interface. At constant gas flow rate, as the vertical distance increased in the centerline, off-center configuration of nozzles displayed higher values of the dispersed phase holdup than those of the center configuration. The variation of the dispersed phase holdup with the dimensionless axial distance and the gas injection rate was correlated by using the Modified Froude Number. The experimental values of the dispersed phase holdup were found to be in good agreement with the calculated values obtained from the correlation equations."

Jan 1, 1999

By A. V. Tarasov, V. M. Paretsky

"A mathematical model of the low-temperature (soft) nickel oxide reduction (SNOR) in a tubular kiln has been developed including an equation describing changes in the nickel oxide content of the solid material along the length of the kiln; an equation describing the changes in the content of reagents ensuring nickel reduction (i.e., hydrogen and carbon monoxide) in the gas phase along the kiln length; as well as the temperature along the kiln length. The kinetic relationships used for the development of the model had been determined based on experiments conducted specially for this purpose. Model investigations were conducted to determine the distribution of such parameters along the length of the kiln as the contents of metals oxides in the solids, partial pressure of hydrogen and carbon monoxide, variations of the temperature depending on the SNOR process conditions, including the kiln rotation speed. Based on the data obtained, a simplified regression model of the reducing roasting process was developed.IntroductionAt the SeveroNickel complex (Russia) a technology has been developed and is being introduced on a commercial scale for low-temperature (soft) nickel oxide reduction (SNOR) in tubular kilns.The SNOR process has a number of advantages, the main of which are the higher degree of metallization and higher chemical activity of reduced nickel oxide attributable to the lower fusion of the surface of the grains of reduced material due to lower process temperature (800-1000°C) and improved reducing ability of the gaseous phase. However, the fact that the process is conducted in a gaseous phase sets higher requirements to the consistency of its composition necessitating careful continuous monitoring and control of the main process parameters."

Jan 1, 2001

By M. I. Novgorodova

Most of the gold in the earth&apos;s crust occurs as finely-dispersed gold and accounts for much of the gold lost in extraction processes and during exploration for gold. The Compositions, sizes, and morphology of fine gold particles (0.01 to 10 ~m in diameter) were studied with high resolution electron microscopy coupled with electron microprobe and microdiffraction devices, using colloidal carbon replicas. Correlations were made between fine gold, mineral associations and ore genesis. The results provide qualitative information on the proportions of finely dispersed, invisible and visible gold distribution in ores. Such knowledge is fundamental when planning an optimum technological recovery process.

Jan 1, 1991

By Tao Jiang

Germanium is widely used in many fields, and the production of germanium is very important. The effects of initial sulfuric acid concentration, liquid to solid ratio and other parameters on the leaching rate of germanium and zinc from germanium-bearing zinc oxide has been studied. The occurrence and form of germanium and other elements in the leach feed and the leach residue were studied by EPMA, XRD and chemical analyses. The experiments showed that the leaching rate of germanium and zinc was 91% and 88%, respectively under optimal conditions. Wurtzite was the main limiting factor for the leaching rate of zinc while the leaching rate of germanium was limited by insoluble germanium compounds. Furthermore, it was found that some germanium was bound up in galena in the leach residue. These results may be helpful for further improving the leaching rate of germanium in germanium-bearing zinc oxide.

By Pranav Deshpande

The wear behavior of metal matrix composites differs from that of the monolithic metallic counterparts because composite materials have multiple constituents in their structures and these constituents wear at different rates. It was observed that under low wear stresses, abrasive wear prevailed. As the wear stress increases, pullout of reinforcement occurs and both abrasive wear and wear due to pullout contribute to the overall composite wear. A model of wear taking into account both types of wear has been developed. A critical pullout wear stress was suggested for each composite. Below the critical wear stress, no pullout of reinforcement occurs. It turns out that the critical wear stress simply equals to the ratio of the interfacial strength between the matrix and the reinforcement to the friction coefficient between the reinforcement and the wear counter surface. The critical wear stress is independent of the particle size of the reinforcement. From data on wear of 53% WC composites, the equation of wear for 32% WC composites was obtained. Experimental results agreed well with the predicted wear rate of this composites. This provides an excellent verification of the wear model developed by Lin and Deshpande. Wear data from Modi et al. in the literature were also perfectly fitted with the model.

Jan 1, 2006

By W. R. Opie

Fundamentals of blast furnace smelting of low grade copper and precious metal scrap and residues are reviewed with emphasis on emission control, by-products produced, slag cleaning for high recovery of metal values and the evolution of an off-gas system to eliminate hydrocarbons that result from decomposition of plastics in the blast furnace- charge. Problems with tin, antimony and nickel in the smelter-refining cycle are discussed.

Jan 1, 1985

By G. Cifuentes

It&apos;s know that the cathodic purity and the electrolyte treatment is affect for the solid present in the electrolyte. Anodic slimes properties (f.e.: chemical composition, crystalline composition, sedimentation) was studied in copper electrorefining, this properties were modify through by anodic composition and current density. In this paper will be present only the preliminary anodic slimes relationship at different lead anodic composition. The anodic material was doped during the poured process with lead at different composition. It&apos;s confirm the apparition of the (Bindheimitte) SMbz07. The specific gravity of this specie is approximately 7.3 - 7.5, with this values is biggest the probability of sedimentation and smaller the slimes not sedimentabel.

Jan 1, 1999

By Kouji Mimura, Masahito Uchikoshi, Minoru Isshiki

"HfO2 is expected to be a gate dielectric used in ULSI alternatives to S1O2. Although the materials used in ULSI are required to be significantly pure, commercial Hf contains > 2 mass% Zr. It is important to establish a process for removing Zr from Hf. In the present study, anion-exchange separation using a multi-column method was employed. The separation tests were carried out at variety of temperatures and flow rates. The decrease in the flow rate of the mobile phase made the elution curves of both Hf(IV) and Zr(IV) broaden contrary to the case of Co(II), Cu(II), or Fe(III). This is caused by the difference in adsorption rate on the anion exchange resin. In addition, more than one column was connected in series in order to enhance the separation. As a result, the content of Zr(IV) was successfully reduced to 1/100 of that relative to the raw material.IntroductionHafnium is one of the most important materials in modem society. The main applications of Hf metal are as a control rod in a nuclear reactors because of its large neutron-capture cross-section and as an additive to various alloys because of its corrosion resistance [1]. In addition to those applications, attention has been recently paid to HfCh as a high-x"" dielectric used in ultra large scale integration, ULSI, as well as ZrCh, AI2O3 and La2C>3, which are expected to be alternatives to conventional S1O2 thin films [2].The materials used in ULSI are required to have a high purity in order to avoid unexpected errors due to impurities. Furthermore, high purity Hf is indispensable for investigating the intrinsic properties of Hf metal. Thus, it is significant to establish the purification process for Hf from both the industrial and academic perspectives."

Jan 1, 2012

By Li Yuhai

Kinetics of non-isothermal precipitate process and crystal growth of perovskite (CaO ? Ti02) phase in CaO-TiOz-Si02-AlP3-MgO system were studied. The experimental results show that the relative volume fraction can be described by the equation given by K. Matusita et at. and the experiential expression of average crystal radius was obtained. The particle coarsening in non-isothermal process has important effects on the crystal growth of perovskite phase.

Jan 1, 2000

By W. D. Cho

Fast dissolution of nonmetallic inclusions such as alumina particles in molten slags has been required in secondary steelmaking -ladle and tundish - to minimize the amount and the size of nonmetallic inclusions in steel products. In the present work, the dissolution behavior of alumina particles in molten CaO-A12O3 and CaO-A12O3-SiO2 slags at the temperatures between 1450 and 1550°C have been investigated in terms of kinetics and mechanism. Alumina particles were added directly into the slags and the variation of the particle size with time was determined using optical and electron microscopies. The conventional types of slag for ladle and tundish were included in the dissolution study. The effects of Al2O3, Siq, CaF2 and MgO contents on the dissolution rate of alumina particles have also been determined. The diffusion boundary layer between alumina particle and bulk slag phase has been observed and analyzed using SEM and EDS. Based on the analysis of kinetic data and the boundary layer, the dissolution mechanism has been discussed.

Jan 1, 2002

By E. Allaine

Carbochlorination kinetics of pure MoO3, Nb2O5, Ta2O5 and V2O5, by Cl2+CO+N2 gas mixtures was investigated between 380 and 1000 °C. Standard free energy of carhochlorination reactions and phase stability diagrams of these refractory metal compounds were calculated. The influence of total gas flow rate, temperature, reactants partial pressures on the reactivity of these oxides were investigated. The apparent activation energies were found to be about 83, 75, 110 and 100 kJ/mole below 650°C for MoO3, Nb2O5, Ta2O5 and V2O5, respectively. Above this temperature, the Arrhenius plots exhibit a rate anomaly attributed to thermal decomposition of COCl2 and/or structural changes of these refractory metal oxides. The apparent reaction order of carbochlorination of these oxides with respect to Cl2+CO was determined. For these refractory metal oxides, the reaction rate was maximum for a Cl2/CO ratio of about 1 in the chlorinating gas mixture. Results of carbochlorination of these oxides are compared and discussed.

Jan 1, 1995

By Wentao Guo, Xuefeng She, Qingguo Xue, Jingsong Wang

By the coke gasified reaction device and online measurement high-temperature compressive strength apparatus, the variation of pore structures of coke after gasified reaction with CO2 and H2O was investigated. Research illuminating the influences of solution loss rate, temperature, and carbon species on compressive strength of coke was also carried out. The results showed that the total compressive strength was higher than for the reaction with CO2. The high-temperature compressive strength of coke decreased with the increasing of solution loss ratio or temperature after reacting with CO2 and H2O. At the same solution loss ratio, the damage of pore structure to coke strength after gasified reaction with H2O was relatively smaller and the deformation resistance was stronger when compared with that in CO2.

Jan 1, 2016

By Liangju He, Peixuan Ouyang, Peijie Li

Single-pulse laser ablation of aluminum and titanium alloys under glass confinement is investigated. Processing parameters such as laser intensity and gap width between targets and glass are varied. Surface morphologies and crater profiles of the alloys after laser ablation are studied by SEM and white-light interferometric microscope, respectively. The effects of gap width and laser intensity on surface morphologies and crater profiles of targets are systematically analyzed. In addition, the generation of porous surface structures in Ti target is regarded as the result of phase explosion in the molten surface layer of targets and the thermodynamic condition in our experiment for phase explosion is evaluated.

Jan 1, 2016

By R. P. King

The central idea presented in this paper is straight forward. Some fairly obscure mathematical techniques are presented from the fields of integral geometry and stereology and these techniques are shown to provide workable quantitative relationships from which the liberation spectrum of an ore after comminution can be determined. The experimental data that is required can be obtained very accurately and conveniently by image analysis of polished sections of the original ore. This quantitative mineralogical analysis provides a bridge that can link the worlds of the mineralogist and the mineral process engineer. This paper has been written to introduce this quantitative approach to a wider audience in the hope that the approach will be used more widely and that the basic linear intercept analysis data will be measured for a wider range of mineralogical textures. This could lead to a more comprehensive characterization of typical mineral ores that will be of considerable use in practical mineral processing.

Jan 1, 1991

By Dan A. Mackie

Continuous leaching of precious metals ores in a vat is possible using a jigging technique. This patented method promises to be competitive with heap leaching, particularly in northern climates, difficult terrain, high precipiptation regions, and environmentally sensitive areas. The paper discusses test work to date, plans for pilot plant testing and basic economics

Jan 1, 1990

By P. Chris Pistorius

"Ilmenite smelting involves partial reduction of iron oxide from a slag consisting mainly of T1O2, T12O3 and FeO, yielding as products iron (with approximately 2% carbon) and titanium slag. Slag purity requirements preclude any fluxing additions, and the aggressive nature of the slag necessitates a furnace freeze lining. Large departures from thermal and chemical equilibrium hold in the smelter, with possible implications for process stability. The slag is approximately 150K. hotter than the metal, which means that the metal temperature is below the slag melting point; this difference in temperature has been shown to lead to formation of a solid TisOs-rich layer between the slag and metal. Recent equilibrium measurements have confirmed that the slag and metal are not in chemical equilibrium either, with significantly more reducing conditions in the metal than in the slag. After solidification, the pseudobrookite slag structure is metastable below approximately 1400K, and may transform upon slight oxidation.IntroductionThe natural mineral ilmenite is the main source of titanium, which is mainly used to produce Ti02-based pigments. Ilmenite has the ideal formula FeTiC>3, but natural minerals can be partially oxidized (to contain some Fe3+), and typically contain MnO and MgO as well, together with associated silicate minerals. Smelting is one of the methods to upgrade ilmenite for subsequent T1O2 pigment production; smelting involves partial reduction of FeO to form metallic iron as a byproduct and titanium slag as the main product. Reduction is typically controlled to yield a slag which contains around 10% FeO, 85% (Ti02+Tij03) and 5% impurity oxides (mainly MnO, AI2O3 and S1O2). An example of a typical average slag composition from reduction of South African ilmenite is shown in Table I. As this indicates, a significant side reaction is reduction of some T1O2 to T12O3. The relative extents of reduction of FeO to Fe and of Ti02 to T12O3 are such that the slag stoichiometry is close to that of the pseudobrookite phase [1]. Pseudobrookite has the structure AB2O5 (where ""A"" and ""B"" are different cation sites); the phase which makes up the bulk of solidified titanium slag has the AB2O5 structure and stoichiometry [2], and can be viewed as a solid solution of FeTi20s, T13O5, ÌçÔÀ2è5, MgTi20s, AI2T1O5 and C^TiOs [1]. This solid-solution phase is referred to as ""pseudobrookite"" or ""M3O5"" in this paper."

Jan 1, 2012