NON-FERROUS METAL EXTRACTION AND PROCESSING: PRINCIPLES, TECHNOLOGIES AND INDUSTRIAL PRACTICE

The effects of various experimental parameters were investigated using a batch adsorption technique. Adsorption of Cd and Zn by pure palyorskite as a function of pH (pH 6, 8 and 10), EC (EC 4, 6 and 8) and the amount of Cd added range from 0-100 mg/L to this mineral were studied. In this study, a natural palygorskite clay from (Dogtown, Florida USA) was selected as an adsorbent, and the adsorption capacity of Cd (II) and Zn (II) onto the adsorbent was investigated. The effects of parameters such as EC, pH of suspension solution, and amount of particle size of the adsorbent on adsorption capacity for Cd (II) and Zn (II) were studied. To understand the adsorption mechanism, the variation of the pH and EC (S•m-1) of the Cd (II) and Zn (II) solution in the adsorption process and the different adsorption models that can describe the adsorption of Cd (II) and Zn (II)) onto natural palygorskite were determined. The shape of the isotherm were L1 and L2 type isotherm for the sorption of Zn (II) and L2 type isotherm only for the sorption of Cd (II). The basic mechanism governs the Cd adsorption characteristics of palygorskite at studied pH is adsorption and ionic exchange. However, for Zn (II) the adsorption on the pure palygorskite show similar trend as Cd at low pH and EC but at high pH values the adsorption of Zn was minimal comparing with Cd suggesting a precipitation. The results were fitted to both the Langmuir and Freundlich isotherms. A satisfactory agreement between experimental data and the model-predicted values was expressed by the correlation coefficient (R2). The fitness of the adsorption data of the adsorption of Cd and Zn on palygorskite into the Freundlich isotherm confirmed its heterogeneous nature. Data from this study proved that metal cations from aqueous solution can be adsorbed successfully in significant amounts by palygorskite.

Whereas demand of ferrosilicon with high purity for electrical uses has been increased, the continuous degradation in raw materials, quartzite or quartz and reductants like coke and coal impose a heavy burden on its refining step. In principle, although it is difficult to refine ferrosilicon with high silicon content in ladle treatment, some basic smelting treatment like gas injection or slag addition into ferrosilicon was tested for the first trial of high efficient method exploration. Ferrosilicon with 75% of silicon content(FeSi75) alloy was treated with gas atmosphere in various oxygen potential, and CaO-SiO2-Al2O3 slag was equilibrated with same alloy in order to investigate the refining ability of impurities.

Measurement and control of elements in metal refining are critical in order to achieve optimum properties. Solid electrolyte sensors for monitoring oxygen are well established and have made major impact in the metal industry. Potential developments in measuring a number of other elements are discussed in this paper with examples drawn from real industrial trials and applications. Recently sensing of dissolved hydrogen has been advanced. These sensors rely on proton conducting high temperature oxide electrolytes with metal / metal hydride sealed reference electrodes. Furthermore, a sulfur sensor based upon strontium -alumina solid electrolyte has been developed and tested in carbon saturated liquid iron. The -alumina electrolyte was optimised for thermal shock resistance and toughness by incorporating partially stabilised zirconia. A mixture of molybdenum and molybdenum sulfide was used as the reference electrode, while SrS, sensing auxiliary electrode was allowed to form in-situ during the sensing process. Implications for further future developments are discussed.

The bioleaching is a biochemical process that is based on the capacity that certain microorganisms have to transform insoluble elements present in certain sulphide minerals in soluble elements and easy to be extracted from the leachate in conventional downstream processes. The leaching microorganisms are characterized by a unique capacity to grow in environments virtually uninhabitable for the majority of microorganisms, as they live in places with extremely low pH and in temperature that can vary between 25 to 80 oC. In a process of leaching, sulphide minerals are used to obtain a flotation concentrate so as to recover a large part of the metal of interest bearing sulphide minerals. In the case of copper, for instance, its main sulphides are the chalcopyrite, bornite, chalcocite, enargite, tenantite and covelite, being chalcopyrite the most abundant copper sulphide and the most important economically. This research work aims at controlling, in an orderly manner, the biological processes that occur in a heap of copper sulphide minerals-bearing flotation concentrate. In a bioleaching heap without external control, it is observed that mesophile microorganisms are acting in the most external areas of the heap, i. E., in areas where there is more heat exchange, and the moderate and extreme thermophilic ones act in the inner parts of the heap, in their acting corresponding temperatures. The oxidative processes that occur have exothermic character and there is a trend of intense rising of temperature inside the heap, which may occur, as a result of this heat intensification, the death of part of these microorganisms. However, a temperature control, in combination with an up-flow of air can prevent the death of microorganisms and reach a significant extraction of those metals of interest, without mentioning the redox potential monitoring, which gives a quite reliable indication of the sulphide minerals oxidation process efficiency.

The possibility of using Electric Furnace gases as combustible inside a Rotary Kiln is described through proper control and optimization. According to the theoretical investigation, in controlled properly the Electric Furnace gases can be used as combustible inside of a Rotary Kiln. The benefits of this procedure are the drastic reduction of the production cost per ton of nickel, the reduction of mazut consumption in Rotary Kiln and the improvement of the quality of refined Fe-Ni by having less sulfur. Furthermore, the use of electric furnace gases inside the Rotary Kiln will decrease the environment pollution, since it releases less quantity of gases that pass through Electric Furnace scrubber. This paper describes the control and optimization of the use of electric furnace gases in Rotary Kiln.

The blast sintering process considered in this paper is based on a Dwight-Lloyd sintering machine and all the peripheral sections of the process. The study of sintering process has attracted interest, not only in iron and steel industry, but also in nonferrous industry. An Automation Master Plan was conducted to achieve the control optimization, based on an integral approach, in which is recognized that lead sintering process automation and optimization is crucial for future competitiveness within non-ferrous industry; Considering that optimization means improving productivity, subject to different constraints within the plant operation. In the pursue of this goal it is necessary to use an engineering and scientific approach in order to evaluate all the factors influencing the production rate, quality and SO2 emission, among others, on the sintering plant. Once all those conditions were identified, it was necessary to conduct a technology assessment in order to select and implement the most appropriate tools to accomplish the optimization goal. The technology implemented covered all aspects from selecting the distributed control system technology, smart process measurement instruments, digital communications protocols (Fieldbus, Devicenet, Ethernet), digital motor control technology, PID controller tuning software, Model Predictive Control, Expert Systems, Neural Networks and Fuzzy Logic in order to run the plant as efficient as possible. The Automation Master Plan has been applied with a scope of five years, and the results achieved have clearly demonstrated that benefits obtained significantly improve production economics and maximize long-term return on investment.

The secondary copper anodes are electro refined in an electrolytic system, where the electrolyte is an acid of copper sulphate solution. During the electro-refining process the anode slime as fine material falls in the bottom of the electrolytic cells. The anodic slime introduces a multi-component secondary product of electro - refining process of metals composed of insoluble components of Cu, Au, Ag, PGM etc. The composition of the anode slimes varies according to the composition of the anodes. The experimental part is developed in lab-scale electrolysis - cell made of acryl glass. The anodes are secondary copper produced during the gold electro-refining process. For chemical and physical characterization of the anode slime XRD, XRF methods are used. The qualitative preparation of raw material - anode slime of secondary Cu and its rational utilization will result the optimization of process of gaining metals for which it is dedicated. This study has shown that the complex anode slime containing gold, silver and these metals can be separated. The anodic slime processing is controlled and optimized with the aim to recovery Au, Ag metals. During the anode slime processing carefully planned leaching procedure is required and different methods and equipment are used as well.

3D computer models of phase diagrams may be designed as an assemblage of surfaces or phase regions. In the last case, the 3D model is able not only to fulfill the functions of visualization and correction, but also to analyze the mass-balances of components, phases and the phase microconstituents. For instance, 3D models had been designed for 10 phase diagrams, published in the Atlas for lead-free soldering (COST 531. European Science Foundation, Czech Republic, 2008. Vol. 1): Ag-Au-{Bi, Sb}, Ag-Cu-{Ni, Pb, Sn}, Ag-Bi-Sn, Au-Bi-Sb, Au-In-Sb, Bi-In-Sn, In-Sn-Zn. There are some disagreements at least in three systems, described in this book. One of three invariant transformation of the system Ag-Bi-Sn is denoted as the degenerated one, and it requires to get more exact data of temperature and concentration of all four phases, which participate in this transformation, and the univariant ones, connected with it. The 3D model also helped to find two surfaces and two phase regions in sections of the Au-Bi-Sb T-x-y diagram, missed in the Atlas. Analogous model of the Ag-Cu-Sn T-x-y diagram showed a mistake in one of three isotherms, and five problem places were found within one of its isopleth. 3D computer models of phase diagrams may serve for searching for mistakes in projections and sections, designed by thermodynamic methods, and for correction of experiment data interpretation.

As one of the alternative technological route for copper recovery, hydrometallurgy has experienced high use intensity and a significant impact due to its ability to process ore with average and low grades at competitive prices compared with other metallurgical routes. In spite of instrumentation in pyrometallurgical and concentrators plants; Developments in agglomeration and heap leaching instrumentation has not reached the required level for a fully automated control system. Variables such as agglomerates moisture content, size, shape, flowability, and internal and superficial moisture heap leaching content are difficult to measure in real time hindering the implementation of an automated control system. Since closing an automated feedback loop is not possible, a powerful Hydrometallurgical Decision Support System (HDSS) has been developed that recommends control actions to operators of primary and fine crushing, agglomeration and heap leaching in an integrated manner. Also, the HDSS, which is connected to the real time plant information system, gathers the information by sensors and laboratory analyses to suggest to the metallurgist both curing and leaching rates, and if he approves, this new rates will be informed on the operator’s interface. The HDSS main goal is to stabilize and increase the plant production while minimizing the energy consumption. To assess the HDSS performance, different strategies commonly used by the operators against the HDSS recommendations have been simulated. Results show that the HDSS achieves the proposed goal, decreasing the overall specific energy consumption and stabilizing the plant operation by reducing downtimes due to equipment failures.

A dynamic simulation tool was used to quantify the benefits from the implementation of an advanced control system for a low grade Nickel sulphide ore beneficiation plant. In order to obtain a consistency between the simulation and the process a database that represented the natural variability of the ore was used. The information consisted of laboratory analyzes every 2 hours for the concentrations of nickel in the feed, product and tailings from the plant. In addition, variability in the feed rate was included in order to simulate the performance of the circuit. Empirical and phenomenological mathematical models, of each unit operation of the processing circuit, were calibrated in the simulator. The representativeness of the tool was proven by the confrontation of the results obtained against the data from the laboratory. The variables of the models were changed during the dynamic simulation to reproduce the usual control done by the operators. To provide comparison data another scenario was simulated with advanced process control. This was possible due to the fact that the simulator has a data manager performed by an artificial intelligence that allows configuring process control strategies, such as an expert system. After the analysis of simulation results, it was possible to estimate the improvement obtained with the implementation of an expert system through evidence of increased Nickel metallurgical recovery. There was also reduction of the variability of product quality. The above mentioned results show that techniques for advanced process control are among the most effective methods in cost and time to improve plant performance.

The quaternary intermetallic compounds Al9(Mn, Fe)xSi are very important in structural applications, since they have a high mechanical resistance, high hardness and excellent resistance to corrosion compared to other materials. In this work, small samples were produced from reactive sintering of a mixture of powders Al, Fe, Mn and Si at temperatures between 1073 and 1123 ° K and under application of pressure between 5 and 20 MPa, which was observed by SEM of the intermetallic quaternary of type AlFeMnSi. It is important to highlight that the pressure is the variable that has higher effect on the quantities of the phases alpha-AlFeMnSi and beta-AlFeMnSi formed at a temperature of 1073 °K and clearly when you apply a force of compression during reactive sintering, there is, as a result, a greater contact between particles of the different phases, thus obtaining mostly densified samples. Therefore, the microstructure after sintering reactive 1073°K and 15 MPa leads to the formation of mixtures of intermetallic either cubic or hexagonal (alpha-Al9(MnFe)Si and beta-Al9(Mn2Fe)Si respectively). The results showed that the amount of hexagonal phase increases as it increases the pressure and temperature.

Large Metallurgical Complexes are large users of Energy, Water and Assets. There are 1000 thousands of meters to manage the information at the local and enterprise level. To improve the effectiveness of energy and assets the quality of the data and events, it becomes a paramount for real time operational management. The lack of resources at the local operations and at the enterprise to process the sea of information becomes impossible and many projects have failed. As such, a novel approach for implementation of continuous improvements at the local level and innovations at the strategic level was implemented at all operating plants at AngloPlats. The new capability of an enterprise real time monitoring and diagnosis software infrastructure was available to implement many business strategies in tandem. As such, asset monitoring, energy, production and process control management was implemented in an integrated approach reusing the same data but with different context and time horizons to have standard methodology for local root cause analysis. At the same time, real manufacturing services to support operations and keep the continuous improvement and innovations found as new opportunities at the enterprise are found in industry. This paper will highlight the required computer architecture, data hierarchies’ approaches for adaptive reporting, condition based event management and notifications. The results based on the integrated and collaborative team efforts will be presented. PI System for a targeted reduction in energy consumption of 15% by 2014.

The BF regime and its thermal state are functions of the following parameters: Blast hot air temperature; Blast air volume; Coke, coal and CH4 consumption; O2 and H2O injection rate; Charge volume and materials structure; The quality of raw materials; The quality of coke and coal. Under the conditions of a given charge, a combination of the above parameters will lead to a specific regime of the BF and its thermal state, represented by the following indexes: Pig iron and slag temperature; Flame temperature; Top evacuated gas temperature; The distribution of Fe direct reduction; Gas yield CO2/(CO2+CO); BF productivity; The thermal balance of the BF inferior zone; Gas composition (CO2, CO, H2, H2O); Slag yield; Slag basicity; Pig iron and slag composition; Which lead to short production cost variance. Most important variable parameter is energy consumption as function of raw materials and variance of input of the oxygen. The determination of this complex function in BF process will be the object in our study. In first stage of our study there will be a static model, establishing the quantitative relations between input elements and the reactions’ finished products, without being involved in their kinetics.

The processing response of magnesium alloy WE43 to hot working was studied by conducting hot compression test at five different temperatures and strain rates. Using this data, a Strain Rate Sensitivity (SRS) map was developed to have a basic idea about hot working domain of the alloy. The results from the SRS map were applied and the alloy samples were rolled at 350oC and 400oC. Various characterization techniques such as optical microscopy (OM), scanning electron microscopy (SEM), Electron Back Scattered Diffraction (EBSD) and X-ray Diffraction (XRD) were used to analyze the samples. The solutionized alloy was also subjected to Multi Axial Forging (MAF) to evaluate the effect on grain size and the texture.

Al-Si alloy A356 was modified by TiC nanoparticles. First, the nanoparticles were mechanochemically activated together with aluminum powder. Next, the activated particles were hot extruded in a home-made extruder. Finally, nanoparticles thus prepared in the aluminum matrix were added to the liquid Al-Si alloy, which was then cast into sand molds. A comparison of the microstructure and mechanical properties of the modified alloy thus produced with those of the alloy without the nanoparticles demonstrated that the grain size of the modified alloy decreased. The mechanical properties determined after T6 heat treatment indicated unusual behavior, where the elongation of the modified alloys increased by 20-50% in different regions of the cast, while the tensile strength remained unchanged and the hardness increased by 18%. An electron microscopy study revealed concentration of dislocations near grain boundaries in the modified alloy samples. These grain boundaries serve as obstacles to dislocation motion. It was therefore concluded that the improvement in the mechanical properties of the aluminum alloy modified by TiC nanoparticles was caused by the grain-size strengthening mechanism.

Elemental mercury in flue gas of coal-fired plants was concerned as another serious pollution when sulfur dioxide pollution is now controlled. The adsorbent made from fly ash by thermal precipitation sulfur to remove mercury in fuel gas from coal combustion plant, SEM, BET, TGA and other measurement methods were used to characterize the effect on surface morphology, sulfur distribution and specific surface. High temperature deposition furnace was applied to increase sulfur content in fly ash based adsorbents produced in lab. The study found that sulfur attached to the adsorbent surface, mesopore structure, microporous structure, increases its sulfur content of adsorbent. Sulfur was filled in interspace as small molecule S2, S5, increased their surface area and enhanced their adsorption capacity. The specific surface area increased by thermal precipitation sulfur, and specific surface area which increased with increasing temperature.

Advanced Process Control using expert systems has been proved as extremely efficient in controlling many different ore treatment processes. However the control can only be as efficient and reliable as the measurements of process variables supplied to the system. Several times, flotation processes are controlled solely on lab results that may come every few hours. During this period the operator is essentially blind to process variations and disturbances. Furthermore, if the lab fails to supply the results on time, the operator may take decisions that yield in lower recovery, high consumption of reagents and so forth. An automated image processing system designed to operate continuously to measure froth speed, bubble size and color in combination with an expert system may be implemented to improve operation efficiency, reduce the stabilization time of the process by disturbances in the ore, increase product recovery, thus resulting in lower operation costs and higher profit. This paper presents a successful case using CEMI’s OptVision Froth Imaging System and OptProcess Expert System to Control a non-ferrous ore direct flotation process.

A new improved method for the treatment of molybdenum sulfide concentrates by water vapor is developed, which ensures high level of the extraction of molybdenum (in the form of technical molybdenum trioxide) with 98.5% recovery, together with rhenium (90%), selenium (90%), tellurium (90%), and sulfur (in the form of sodium sulfide or elemental sulfur) with 99.5% recovery. The developed technology provides a successful solution of problems associated with the comprehensive, environmentally safe and highly efficient processing of molybdenum and other metal concentrates. Particularly the desulphurization problem is solved. The design of the pilot plant, optimal operation regimes and processing parameters are presented in the paper.

As an alternative to pyrometallurgy, hydrometallurgy is being used in an increasing number of copper mining operations as the main route for extracting copper. Hydrometallurgy is typically divided in three stages: Leaching, solvent extraction and electrowinning. Prior to the leaching stage, copper ore undergoes preparation through comminution, followed by agglomeration. This preparation process is highly energy intensive, mainly due to crushing, screening and transportation of the copper ore in conveyor belts. Due to environmental, social, technical and economic considerations, energy availability is becoming one of the main constrains in mining operations. This situation has generated a growing interest in automation and control technologies and developments in order to reduce energy consumption while maintaining a certain level of production. This paper presents the design and implementation of a plant wide control system for the crushing, agglomeration and leaching processes. Different control strategies with distinct objectives are developed for each process, with the overall goal of minimizing energy consumption and maximizing copper recovery while keeping a stable and robust operation of the plant in the presence of disturbances and changes in the characteristics of the ore. The proposed control strategies, ranging from expert control to multivariate predictive control, are validated with a dynamic simulator.

Selenium is an important VI group semiconductor, which has found applications in rectifiers, solar cells, photographic exposure meters, data storage devices, xerography and anticancer agents. It is also used in the glass industry to eliminate bubbles and remove undesirable tints produced by iron. In addition, selenium also has a high reactivity towards a wealth of chemicals that can be potentially exploited to convert selenium into other functional materials such as CdSe, ZnSe, Ag2Se and so on. Here, we report a review of structural investigations of the Selenium based materials in glassy and nanostructured forms. L-edge XANES (X-ray Absorption Near Edge Structure) spectra of doped As2Se3 and Se-Te glasses have been acquired experimentally using synchrotron radiation. The experimental L- edge spectra of As and Se is compared to the theoretically calculated spectra by two ab-initio methods: The self-consistent methods of DFT (Density Functional Theory) and RSMS (Real Space Multiple Scattering). On the nanoscale, we report the shape and structure controlled synthesis of chalcogenides such as Lead sulfide and Selenium in the presence of water soluble protein Bovine Serum Albumin (BSA) keeping in mind their wide applications in preventive and therapeutic drugs for cancer treatment and as antioxidant agents. BSA has been used as a shape directing agent to synthesize crystalline Se nanobars (NBs) and amorphous nanospheres in aqueous phase at relatively low temperatures. Well defined multifacet NBs are produced when the amount of Na2SeO3 is at least six times greater than that of BSA, while amorphous spheres are formed with nearly 1:1 ratio. Both morphologies have been fully characterized by FESEM, HRTEM, EDX, and XRD analysis.

The oxidation of sulfides is a complex process involving gaseous products and intermediate species given rise to emission and absorption spectra which carry out important information about the reaction process. This information could be used for on line monitoring of pyrometallurgical reactor if the appropriate sensors were available. We present in this paper an analysis of the concept that has been successfully applied in iron and steel making industry, as well on fuel combustion control, where the spectra measurement gives the possibility for online monitoring and automatic control of high temperature processes. This concept has not been widely applied in the nonferrous pyrometallurgical primary production. The design of new sensors is discussed from the analysis of spectra measurements during flash combustion of copper concentrates at laboratory scale.

T-x-y diagrams with liquid immiscibility are employed widely as a solution of the problem associated with a high-melting compounds obtaining (borides, silicides and intermetallides). Besides the well-known flax method with only one solvent, the immiscibility gap method for the metallic systems was offered in the third millennium. In this method, the synthesis and crystallization of compounds have place on the border of two solvents. This technology includes many unknown details. The purpose of this work is to simulate the computer models of phase diagrams with the formation of liquid immiscibility cupola within the primary crystallization surface of one component or adjacent to one, two or three sides of triagonal prism. The software "Constructor of Phase Diagrams", based on the kinematical method of surfaces description, is used for the construction of phase diagrams models and its following investigation. The simulation of phase diagrams models makes possible to analyze the geometrical structure and sections as well as to obtain information about the crystallization paths and compositions of conjugated phases. These models are the templates for phase diagrams with the similar topological structures, when a real system is produced by entering the experimental data (coordinates of binary and ternary points on the surfaces contour, information about curvature of surfaces).

In order to solve certain problems in the gold-mining industry the authors have proposed new technology for integrated processing of gold-bearing antimony ores which apart from recovery of gold, allows obtaining associated products – antimony sulfide (Sb2S3) and metallic antimony (Sb) and is based on the use of vacuum thermal processes. In this connection the authors have solved several theoretical and application-oriented problems. Namely, computational methods have been developed for determining values of thermodynamic functions. Unknown values of thermodynamic functions of some compounds (FeSb, FeSb2, AlSb, etc.) have been obtained by calculation. Full thermodynamic analysis of the Sb – S; Sb – S – Fe; Sb – S – Al systems has been conducted. The results of calculations are presented diagrammatically (the temperature dependence of components’ composition). The kinetics of the extraction process of antimony sulfide from the Zopkhito ore deposit (Georgia) was studied for various fraction ores. Optimal conditions for obtaining Sb2S3 have been determined. Commercial-purity (92%) antimony was obtained through the reduction of Sb with iron under vacuum followed by sublimation and condensation. As is known from international best practice the main method of recovery of gold from ores and concentrates is the cyanide method, which is characterized by high toxicity and furthermore does not produce economically acceptable results in the case of gold-bearing antimony ores. An alternative path to solve this problem is proposed by the authors: The process of gold recovery was carried out using chemical (thiourea leaching) and electrochemical (electrochlorination) methods. An installation has been constructed and technical recommendations have been issued.

The mechanism of dysprosium chloride complexes electroreduction on the silver and tungsten electrodes in equimolar NaCl – KCl melt at 973 K has been studied by linear and cyclic voltammetry. The kinetic parameters of processes were calculated. Using data on the structure of rare earth chloride complexes, and in particular, dysprosium, under which there is a pure dysprosium chloride melts in the form of a complex DyCl63-, electroreduction process can be represented by the following reaction: DyCl63-+ 3e = Dy + 6Cl- (1)On the base of our research, the mechanism of dysprosium chloride complexes discharge on the tungsten electrode was described by a three-electron step when the steady-state conditions of polarization is limited by the mass transfer stage, and under the conditions of nonstationary polarization, the slowness of charge transfer stage has become. The diffusion coefficient of dysprosium ions was calculated. The process of electrochemical reduction on a silver electrode, in contrast to the tungsten electrode, is complicated by alloy formation with the cathode material. The directly proportional dependence of the current on the concentration of electroreduction DyCl3 melt at different rates of polarization was observed, which indicates the nature of the diffusion control of the electrode process of recovery.

The mechanism of gadolinium chloride complexes electroreduction on the tungsten electrodes in equimolar NaCl – KCl melt at 973 K has been studied by linear and cyclic voltammetry. The investigation was carried out in three-electrode quartz cell, where the cathode was the tungsten rod; Reference electrode – quasi-stationary glassy-carbon plate; Both the anode and the container – glassy-carbon crucible in the atmosphere of purified and dried argon. The kinetic parameters of processes were calculated. It is shown that the mechanism of gadolinium chloride complexes discharge on the tungsten electrode is described by a three-electron step when the steady-state conditions of polarization is limited by the mass transfer stage, and under the conditions of nonstationary polarization, it was noticed the slowness of charge transfer stage. The diffusion coefficient of gadolinium ions was calculated. The process of electrochemical reduction on a silver electrode, in contrast to the tungsten electrode, is complicated by alloy formation with the cathode material. On the base of this research, the mechanism of gadolinium chloride complexes discharge on the tungsten electrode was described by a three-electron step when the steady-state conditions of polarization is limited by the mass transfer stage, and under the conditions of nonstationary polarization, it was noticed the slowness of charge transfer stage.

This work presents the results of joint electroreduction of fluorborate and dysprosium-ions, and determines the conditions of high temperature electrochemical synthesis of dysprosium borides. The dysprosium and boron combine electroreduction was investigated on the background of KCl-NaCl melts at the temperature 973K on different electrodes by the linear and cyclic voltammetry. As a result of this research, it was found that under certain conditions, the concentration of dysprosium and boron and certain anionic composition of the melt it is possible their joint electroreduction. Based on the analysis of voltammograms, it was shown that the electrosynthesis of studied systems proceeds in the kinetic mode. Synthesis of dysprosium borides ultra-disperse powder was carried out by potentiostatic electrolysis of molten equimolar KCl-NaCl, containing DyCl3 and KBF4. Electrolysis performed on tungsten and silver electrodes in the range of -2.5 to -2.8 V relatively of the quasi-stationary glassy-carbon electrode. The electrosynthesis can be represented as a sequence of stages: Allocation of more electropositive component (B); Allocation of more electronegative component (Dy) on pre-selected boron; Mutual diffusion of dysprosium and boron to form the different composition of boride phases. The influence of the electrolyte composition, temperature, current density, voltage on the bath, the duration of electrolysis on the synthesis products were studied. An optimal parameter for getting higher dysprosium boride DyB6 was found.

This paper presents the results of joint electroreduction of fluorborate and gadolinium-ions, and determines the conditions of low-temperature electrochemical synthesis of gadolinium borides. Previously, the gadolinium and boron combine electroreduction has been studied on the background of chloride CsCl-KCl-NaCl melts at the temperature 823K on different electrodes in the atmosphere of purified and dried argon by the method of linear and cyclic voltammetry. Based on the current-voltage measurements, it was shown that under certain conditions, the concentration of gadolinium and boron and certain anionic composition of the melt it is possible to implement their joint electroreduction. Based on the analysis of voltammograms and conducted thermodynamic calculations it was shown that the electrosynthesis of studied systems proceeds in the kinetic mode. And so, the electrosynthesis can be represented as a sequence of stages: Allocation of more electropositive component (B); Allocation of more electronegative component (Gd) on pre-selected boron; Mutual diffusion of gadolinium and boron to form the different composition of boride phases. The influence of the electrolyte composition, temperature, current density, voltage on the bath, the duration of electrolysis on the composition of the synthesis products were studied. An optimal parameter for getting higher gadolinium boride GdB6 was found.

The granulation of nickel sulphide alloys results in formation of the ultrafine structure because of their reactivity is increased in the hydrometallurgical processing. The phase composition and phase size of nickel sulphide alloys granulated were studied by X-ray and optical microscopy methods. It is shown the high cooling rate leads to the crystallization of non-equilibrium phase and dispersion of a metal component. The parameters of the electrochemical oxidation of nickel sulfide granular alloys in sulfuric acid solution were estimated. The initial potentials of phase components oxidation of nickel sulfide alloys granulated were defined. The rate of electrochemical oxidation of nickel sulfide alloys granulated is higher than slow-rate cooling. Using a data of the research, an electrochemical method of extraction of nickel from sulphide materials was proposed. The advantage of the method is the limit of the sulfur dioxide. The method includes granulation of nickel sulphide material and electrolysis to produce cathode nickel, nickel solution and sulfur-sulphide sludge.

Campaign life of furnaces play a vital role in profitability of copper smelters. Besides good quality refractories, improved operational practices can also increase the furnace campaign life. One such practice has been started in Mitsubishi copper smelter of Hindalco Industries Limited (unit-Birla Copper), Aditya Birla Group, India to keep the C – furnace blister siphon open, which not only increased the furnace campaign life, but also improved the working environment. The implementation cost of this practice is less than one dollar and it can save millions of dollars to the organization. It is a cost effective, environmental friendly and very safe practice. The C furnace of Mitsubishi copper smelter works strictly on level difference where stringent level control is must. Any imbalance in level between blister and slag may cause serious explosion due to contact of blister copper and water cooled copper jacket. These types of explosions cease the plant operation for at least 10 days and require huge amount to repair the damage apart from production loss. It affects the plant profitability adversely. Birla Copper, India and LS Nikko, S. Korea, experienced respectively 5 and 3 such explosions so far. The improved practice of C furnace operation reduces the magnetite in blister siphon mechanically as well as chemically and thus prevents siphon clogging, which is the main reason for increase in blister level inside the furnace. This practice also helps to operate C furnace at lower temp (1215 deg C) with high Fe/CaO ratio (2.7 to 2.8). It creates thick coating in front of furnace wall and protects refractory erosion. We have observed absolutely no erosion of refractory during April’2010 shutdown in C furnace at Birla Copper, India. The new practice to keep furnace level well under control and make Mitsubishi Smelters more profitable is nothing but unlocking the operations potential.

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