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By Mike Adams

A comprehensive pre-feasibility study has been conducted by Companhia Vale do Rio Doce CVRD) for Niquel do Vermelho nickel laterite deposit. Within this study, five integrated flowsheet options were evaluated via batch and pilot campaigns at Lakefield Oretest, over an intensive six-month period from receipt of ore to final reporting. Key technical objectives set by the client included demonstrating the technical viability of the beneficiation of several ore types, processing through integrated pressure acid leach/mixed hydroxide precipitation (PALIMI-IP) and mixed sulfide precipitation (PALIMSP) circuits, and the treatment of barren liquors to meet stringent environmental requirements. Refining of the MHP was by ammonia re-leach and solvent extraction (SX) to produce LME-grade nickel cathodes, NiCO3, NiO and CoS. LME grade nickel and cobalt was also produced by oxidation of the MSP and hydrogen reduction on the leachate. The database and data acquisition system, along with web-based reporting, enabled rapid turnaround on both daily and more comprehensive run reports, making it possible for speedy and confident decisions on operating conditions of the complex flowsheets. The high value of developing such data is emphasized and discussed as pivotal in the successful progression of laterite projects through to sustainable commercial viability. Keywords: Flowsheet, CVRD, Nickel, Piloting, Pressure, Leach, Refining.

Jan 1, 2004

By Jianxun Song, Hongmin Zhu, Qiuyu Wang, Jungang Hou, Shuqiang Jiao, Xiaobo Zhu

This work presents the results of a study on the Ti3+/Ti2+ couple redox potentials vs. Cl–/Cl2 at the temperature range (673 to 1073 K) in fused LiCl-KCl eutectic by direct potentiometric method. Initial concentrations of TiClx in solvents did not exceed 5.0 mol%. Basic thermodynamic properties of the reactions TiCl2+1/2Cl2(g)=TiCl3 were calculated using the temperature dependencies of apparent standard potentials of the couples E* Ti3+ /Ti2+.

Jan 1, 2014

By G. Brooks, J. Naser, M. A. Sattar

CFD models have been developed and numerical simulations have been carried out to predict the formation of foam in oxygen steelmaking. Foam was considered as a separate phase comprising a mixture of gas and liquid. Bubble break up and coalescence models have also been incorporated in a CFD model to predict the number density of individual bubble classes. A population balance equation was used to track the number density of each bubble class. Decarburization with heat generation from chemical reactions was integrated in the process. User subroutines were written in FORTRAN to incorporate the foam formation, the bubble break up and coalescence rate and decarburisation in the main program. The model predicted the foam height, bubble number density, velocity of phases, decarburization, and turbulence. The result from the model has been compared with available data from literature and found to be in reasonable agreement with the experimental and plant data.

Jan 1, 2014

By Y. Moriya, Y. Sadayoshi, Y. Nonogaki, Y. Takeda

"Preparation and growth processes of CaF2 on Si(111) and of . InxGa1-x,As islands on CaF2 by molecular beam epitaxy (MBE) are described. It was found that first of all the Si(111) surface treatment process to obtain the 7x7 reconstructed structure was necessary to ensure the cleanness of the surface and to grow a flat and high quality CaF2 on it. Growth of InxGa11-x,As islands on CaF2 was tried by droplet heteroepitaxy using the same MBE reactor. In,GaxGa1-xAs islands were successfully grown epitaxially, and the size and density of the islands dependent on the In composition were investigated.IntroductionThough semiconductor/semiconductor heterostructures are widely used for many device applications, small band off-sets of the conduction bands and the valence bands restrict the utilization of the intra-subband transitions to far-infrared regions. With InAs as the quantum well and fluorides as the barrier layers, we can design three-electronic-level systems in the infrared region, which is the low loss transmission window of the silica optical fibers. To realize those structures, we have grown InxGa1-xAs islands on CaF2 thin films that were epitaxially formed on Si(111) substrates by molecular beam epitaxy. By the droplet heteroepitaxy that we invented, the InxGa1-xAs islands with height of -10 nm have been obtained successfully. Optimum processing to obtain atomically smooth surfaces of Si and CaF2 and high quality InxGa1-xAs islands is reported.ExperimentsMBEMachineCaF2 was grown on Si(111) and InxGa1-xAs islands were grown on CaF2 successively by MBE. The MBE machine consisted of a growth (or reactor) chamber and a loading chamber. The reactor chamber was equipped with Ga, In, As and Er metal source cells and CaF2 and BaF2 source cells. Cell materials were P-BN for Ga, In and As metals, and were graphite for CaF 2, BaF 2 and Er to avoid reaction with BN cells. The electron gun and screen were attached to the reactor to observe the RHEED pattern during the substrate surface treatment and the growth of CaF2 and InxGa1-xAs islands. The substrate manipulator was designed to heat up the Si substrate up to 1,200°C for the surface cleaning. The QMS was also equipped to analyze the residual gas species in the reactor chamber. The base pressure of the reactor chamber was 2-5x10-11 Torr, being pumped by ion pump and the liquid nitrogen shroud"

Jan 1, 2000

By Lifeng Zhang, Zineb Benouahmane, Yaqiong Li

Experimental oxidation tests at high temperature (1000-1200 °C) on SiC samples have been respectively performed under wet and dry air atmosphere for different holding times. The thickness of thermally grown oxide was experimentally measured by DEKTAK Stylus Profilometry. The results showed that the oxidation rate was increased with temperature and holding time, corresponding to a passive oxidation regime which led to the formation of SiO2 layer. The sessile drop method was employed in order to measure the contact angles between Si and SiC at high temperature. Contact angle can be varied from 39.6° to 75.6° by controlling the atmosphere. The deoxidation of the oxide layer and infiltration of liquid silicon caused a decrease in the contact angle.

Jan 1, 2016

By Wei Yin, Bin Xu, Qian Li, Yongbin Yang, Tao Jiang

Copper anode slime is an increasingly significant resource for precious metals such as Au, Ag and Pd. The extraction of Au, Ag and Pd from decopperized anode slime by different pretreatments and different lixiviants including cyanide, chloride, thiourea and thiosulfate have been investigated. When oxidizing roasting pretreatment was carried out under the conditions of roasting time 120min and temperature 625 ℃, the removal ratios of S and Sb could reach 82.18% and 98.52%, respectively. And the following alkaline leaching of calcine could result in the dissolution of 46.40% Cu and 98.48% Pb. The optima leaching ratios of Au, Ag and Pd reached 99.48%, 97.69%, 94.79% by cyanide leaching, and 95.01%, 79.84%, 96.59% by chloride leaching, and about 95.21%, 95.66%, 48.79% by thiourea/thiosulfate leaching.

Jan 1, 2015

By Jun Iwai, Osamu Takai, Yasushi Inoue, Hiroyuki Sugimura

"Infrared reflection absorption measurement was performed during plasma-enhanced chemical vapor deposition of silicon dioxide films at room temperature. Hydrocarbon contaminants adsorbed onto growing film surface are oxidized by oxygen radicals in plasma resulting functional groups which include C=O and C-O bondings. These groups exist only near the surface and are hydrolyzed rapidly after exposure to air.IntroductionRecently low-temperature silicon dioxide (SiO2) deposition has been in a growing industrial demand in pa1ticular, polymelic substrates such as polycarbonate and polyethylene telephthalate, which have poor heat resistance, need low process temperature (near room temperature) in coating of SiO2 which is a suitable material to improve optical and mechanical properties of polymenc products. Plasma enhanced chemical vapor deposition (PECVD) using organosilicon reactants is one of the most promising technique for lowering process temperature, so that it has been extensively studied1-12. In the present; however, hydrocarbon contaminants and a plenty of Si-OH termination in Si-O-Si networks tend to exist in the films, which degrade mechanical, optical and electrical properties of the films. It is necessary to understand the deposition mechanism at, low temperature in order to solve the problems. We have studied the low-temperature PECVD of Si02 by spectroscopic diagnosing techniques such as optical emission and mass analysis6-7, 11- 12Infrared reflection absorption spectroscopy (IR-RAS) has been a well-established technique for characterization of thin films on metals as· well as on semiconductors and insulators13-17. In this paper, we report on' the surface reaction of room-temperature PECVD of Si02by using in situ IR-RAS."

Jan 1, 2000

By S. G. Kumar, R. G. Reddy

"Niobium aluminides offer the advantage of higher high temperature capability compared to other intermetallic aluminides due to the refractory nature of niobium. However, the reaction sequence in Nb-Al system is sluggish and currently there is a great interest in the processing aspects of these materials. In the present study, a systematic investigation was undertaken to compare the effect of different powder metallurgy processing routes on the phase relations and microstructure of 66Nb-22AH2Ti (in atom percent) alloy. The three different process routes adopted were: (i) cold pressing followed by reaction sintering; (ii) cold pressing and hot pressing followed by sintering; and (iii) arc melting, hydride-dehydride process to make the alloy powder followed by cold pressing and then sintering. The samples are analyzed by XRD, Optical Microscopy, SEM-EDS and EPMA. The analysis showed that alloy pellets made from pre-alloyed powders i.e., arc melting followed by hydride-dehydride process, gave good densification and more Nb3Al formation.1. IntroductionTo improve the performance standards of turbine engines, materials scientists are challenged to develop materials that have· high thrust-to-weight ratio with high specific strength, high specific modulus and good environmental properties at elevated temperatures. The conventional high temperature materials like nickel based superalloys are high in density and hence many of the high temperature materials scientists have focussed their attention on intermetallic aluminides like Fe-AI, Nb-AI, Ni-AI and Ti-AI in recent years. The phase relations and properties of alloys based on Fe-AI, Ni-AI and Ti-AI are fairly well known whereas little is known about the alloys based on niobium aluminides."

Jan 1, 1996

By Veneta Groudeva

A pyritic ore containing zinc, lead and copper as? the relevant primary sulfide minerals, .as well as gold and silver finely disseminated in the sulfide matrix, was? leached in percolation columns. Each column contained 30 kg of ore crushed to minus 10 mm. Firstly, zinc and copper were efficiently leached by means of chemolithothrophic bacteria? in acidic sulfate bearing medium. Zinc was leached more rapidly than copper but the final extractions of these metals were similar (about 75% in 300 days). A part of the galena was oxidized to the. insoluble lead sulfate during the leaching. The pyr:ite was, however, relatively slightly attacked. The ore was then leached by means of FeC11 - HCl solutions both in the presence and in the absence of bacteria to solubilize the lead. The chemolithotrophic bacteria grew in media containing both chloride and sulfat~ ions and maintained a high ferric to ferrous ion ratio in the percoiating solutions. The chemical leaching was, however, more efficient since ft was possible to carry it out at higher chloride ion concentrations. About 10% of the lead was leached in this way in 90 days. Finally, the ore was leached by thiourea in the presence of a gold-oxidant (oxone) to extract the gold and silver. Over 60% of the gold and over 55% of the silver were extracted from the ore in 150 days, while. the extractions of these precious metals from an untreated ore sample were lower than 25%.

Jan 1, 1991

By P. M. Swash

This paper reviews the application of some mineralogical techniques in the evaluation of the Uitkomst Ni-Cu deposit, South Africa. The low grade of the ore necessitates detailed and representative characterisation in order to establish the prospects viability. The relevant mineralogical information is generated by using optical microscopy, magnetic and heavy liquid . separations, XRD. SEM and EMPA. Methods used are briefly reviewed. The cost savings and metallurgical understanding that is provided by the mineralogical work is described especially with regard to milling, flotation and the presence of by-products (PGMs and chromite).

Jan 1, 1991

By Sung Tae Kim

The viscosity is one of the most critical properties of slags and thus its influence on the physicochemical phenomena in metallurgical processes has been issued for last decades. The viscosity of ferrous- and non-ferrous metallurgical slags can be understood via structural investigation with spectroscopic methodologies including x-ray photoelectron spectroscopy, infrared- and Raman spectroscopy, and solid state nuclear magnetic resonance spectroscopy, etc. Therefore, the reaction kinetics such as desulfurization in ladle metallurgical furnace, reduction of FeO and MnO in electric arc furnace is strongly dependent on the viscosity of the slags. The rates of oxide (inclusion and refractory) dissolution into the slags and fluxes are governed by the viscosity. Alternatively, the structure of aluminosilicate melts also affects the thermochemical properties such as sulfide capacity, etc. These diverse applications of the viscosity-structure relationship to ferrous- and non-ferrous metallurgical processes were reviewed.

By Guo Xian Jian

In this paper, an alternative process to recover the value metals from polymetallic gold ore by FeCh leaching was proposed. In the process, gold was recovered by direct cyanidation from the leaching residue, the isolative electrolyte in chloride solution was selected to recover lead, the cementation with copper powder was used to recover silver and the solvent extracting was applied to recover copper and zinc. The total recovery of gold, lead, copper, silver and zinc in the process is 90.8%,96.05%,84.3%,81.98% and 54% to the bullion of gold, lead and silver and sulfate of copper and zinc, respectively. The process conditions selected for FeCh leaching are the temperature of 104°C, leaching time of 6 hours, Fe3+ content of 140 g/l and stoichiometry of FeCl3.

Jan 1, 1996

By Dirk Bergmann

During the spray forming process, a continuous molten metal stream is atomized by impinging high speed inert gas jets. In the generated spray cone, the resulting metal droplets are rapidly cooled by the huge temperature difference to the surrounding gas phase and thereby partly solidified during flight. After a certain flight and residence time inside the spray cone, the droplets impinge onto the solid substrate and form the product (deposit) by compaction. Material properties of this preform strongly depend on several process parameters and especially on the thermal and kinetic state of the deposited droplets at the point of impingement. Smaller droplets may cool very fast due to their low mass and impinge onto the product in a completely solidified state as solid metal powder particles. Larger droplets with big mass contain a higher amount of thermal energy and impact during the state of phase change or still as completely liquid. It is obvious, that a certain amount of liquid content in the droplets is needed for forming a homogeneous deposit. Therefore, the thermal history of metal droplets during flight in the spray cone is of great importance for overall process modelling and control. Modelling the effects of the impinging droplet mass on the formation and heat balance of the deposit, the thermal conditions of the droplet stream need to be temporary and spatially averaged at different locations. Averaging may be achieved in different ways, giving alternative results. A first method is averaging over the droplets total enthalpy which consists of the thermal content and the remaining latent heat of fusion within the droplets. A second method may yield the average over the heat content and the solid fraction separately. Results of these two methods depend on the application and the kind of information which one wants to achieve and show some deviations, which will be discussed in terms of consolidation and energy conservation of the deposit.

Jan 1, 1999

By Seung-Chul Lee

Transparent conducting tin(1V) oxide thin films have been studies and developed for the electrode materials of solar cell substrate. Fabrication of tin oxide thin films by sol-gel method is process development of lower cost photovoltaic solar cell system. The research is focused on the establishment of process condition and development of precursor. The precursor solution was made of tin isopropoxide dissolved in isopropyl alcohol. The hydrolysis rate was controlled by addition of triethanolamine. Dip and spin coating technique were applied to coat tin oxide on borosilicate glass. The resistivity of the thin film was lower than 0.18-cm and the transmittance is higher than 90% in a visible range.

Jan 1, 1999

By K. Santowski, S. B. Breyner, T. Prietl

"The material properties of alumina products can be significantly improved by adding Cr203 containing raw materials. Cr203 and Alz03 form an alumina-chromia solid solution during firing, reducing the solution potential when in contact with acidic slags. During service, both a high chemical and high thermomechanical load are present for example in the tuyere zones and taphole areas of metallurgical vessels. For such applications conventional alumina-chromia products suffer from discontinuous spalling as a result of high and frequent thermal shock. Therefore, alumina-chromia materials were developed that exhibit improved thermal shock resistance, compared to the standard products, combined with sufficient corrosion resistance. Laboratory tests evaluated the physical properties of the newly developed alumina-chromia grades and a field test in a Peirce-Smith copper converter demonstrated that the material properties meet the corrosion and thermal shock resistance required for this application. IntroductionTo develop refractory products tailored to specific service conditions it is important to have a profound knowledge of the metallurgical processes and furnace conditions [l]. This enables the specific refractory consumption to be minimized and increases the overall operational efficiency. Economic considerations such as steadily increasing energy and resource costs have resulted in companies investing in recycling processes. In the base metal industry for example, recycling operations involve modifications to the smelter feed, process conditions and chemical composition of the process slags. This adversely affects the performance of standard linings and drives refractory producers to search for material innovations."

Jan 1, 2013

By Yongqi Sun, Zuotai Zhang

Our study investigated the influence of P2O5 and B2O3 on the viscosity and crystallization behavior of Ti-bearing blast furnace (Ti-BF) slags for the purpose of Ti extraction. The investigation of the crystallization behaviors were carried out using a single hot thermocouple technique (SHTT) and the viscosity was obtained by rotating cylinder method. For the viscosity, the results showed that P2O5 substantially increased the slag viscosity. P2O5 is a network-forming oxide, which increased the degree of polymerization of slags and accordingly increased the slag viscosity. However, both of slag viscosity and apparent activation energy for viscous flow remarkably decreased with B2O3 addition. As a typical network forming oxide, B2O3 was introduced into the network and existed dominantly as 2-D structure, BO3 triangular, which caused a simpler structure and a decreasing slag viscosity. As for the crystallization behaviors of Ti-BF slags, both P2O5 and B2O3 enhanced the crystallization trend of rod-shape rutile and suppressed the crystallization trend of dendrite CaTiO3. Therefore the added P2O5 and B2O3 caused the primary phase change from CaTiO3 to rutile. Additionally, it was found that the rod-shape rutile showed a 1-D growth, whereas the dendrite CaTiO3 showed a 3-D growth style.

Jan 1, 2015

By W. L. Cornell

Ore microscopy was used in support of both bench-and large-scale continuous beneficiation testing programs. Reflected light microscopy and Vickers hardness measurements were utilized to help identify problems relating to mineral identification, mineral association, mineral liberation, mineral distribution in product streams, and froth entrainment. Specimens studied were size fractions of concentrates and tailings resulting from Bureau of Mines research to recover a siegenite-enriched product by beneficiating chalcopyrite concentrates. Other specimens were size fractions of bulk sulfide concentrates recovered during the enhanced amine scavenging of final tailings by froth flotation. The findings from studies directly affected flowsheet development.

Jan 1, 1987

By Huang Kai

Uniform needle-like and spherical nickel oxalate particles were prepared by the chelating precipitation process, which was based on the reaction of oxalate acid and the solution of ammonia nickel chloride. The molar ratio of ammonia to nickel ion in the mixed solution is essential to determine whether the spherical or needle-like particles are formed, which means actually the concentration of ammonia is the key to determine the growth mechanism. When oxalate acid is added in the form of solid, it may act as the nucleation interface for the eariy-precipitated substance and so induce the formation of spherical particles. The PVP agent can improve the dispersing degree of the needle-like particles and higher reacting temperature leads to larger particles. The composition of the needle-like particle consists of ammonium and nickel oxalate instead of the pure nickel oxalate.

Jan 1, 2003

By S. W. White

Plasma arc technology is increasingly being used to process a number of waste materials. In present research, plasma technology is being investigated to treat waste magnesium baghouse dust, which is a waste material from the Magnetherm process. This dust contains mostly MgO, but also contains NazO, CaO, and KzO. Plasma energy is to be used along with a reducing agent to produce pure gaseous magnesium while keeping the other materials in a slag. The magnesium will then be collected by rapid quenching. A non-transferred arc plasma torch is ideal for this reaction because of its high enthalpy and improved energy efficiency over conventional methods. Another advantage of plasma is that it allows for the pre-heating or pre-reacting of fine particles before contact with the melt. Thermodynamic calculations using the Gibb energy minimization method were used to determine the most stable compositions of the materials at various temperatures. Energy balances have also been calculated. These results conclude that we can recover approximately 98% of the magnesium with a proper quenching technique. The calculated results are compared with the experimental data, and good agreement between them was observed.

Jan 1, 1999

By P. M. Tyroler

At INCO's Copper Cliff Nickel Refinery, nickel is extracted by using the INCO Pressure Carbonyl (IPC) process. The resulting IPC residue containing copper, nickel, cobalt, iron, sulphur, precious metals, selenium and tellurium is further processed at a hydrometallurgical plant. This plant treats approximately fifty metric tons per day of IPC residue. The components of the feed are separated in a number of steps and a precious metals concentrate, nickel-cobalt carbonate, a selenium-tellurium intermediate and copper cathodes are produced. An iron-arsenic waste stream is also produced and discarded to tailings. The hydrometallurgical processes include pres- sure leaching, cementation, precipitation, thickening, filtration and electrowinning. This paper describes in detail the individual steps of the flowsheet.

Jan 1, 1988