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By Kathryn Hindmarsh

The most common method for the concentration of cyanide in gold leach circuits is based on the titration of cyanide ions with silver ions. This can either be done manually as a titration with a visual end-point or by using one of several commercial cyanide analysers which are 'based on the same titration but use a potentiometric end point This method has 'its limitations in the case of some ores such as those containing high amounts of soluble copper and those that are treated at low (less than pH 9) pH values in that the titration results do not accurately reflect the concentration of cyanide which is available for the dissolution of gold. This paper will present the results of the development of a novel "active" cyanide analyser which is based on the rate, of the reaction between gold colloids and cyanide. Gold colloids have a deep red colour and can be very simply prepared and stored for extended periods of time when stabilized. t has been shown that colloidal gold behaves similarly to metallic gold, dissolving in aerated sodium cyanide solutions to give the colourless Au(CNh-ion, This allows the reaction between the colloids and cyanide to be monitored spectrophotometrically at 520 nm. An automated instrument has been developed around this concept which can analyse a filtered pulp stream every few minutes with periodic calibration using standard cyanide solutions, Results of test work on synthetic solutions and solutions derived from several Australian gold plants will be presented as will the results of a comparative evaluation with a commercial titration analyser on a local gold plant

Jan 1, 1998

By Shengqi Chen

The reduction smelting of nickel laterites produces slag, consisting principally of the chemical components MgO, "FeO", SiO2, and A12O3, and ferro-nickel alloy. Despite the fact that the phase equilibria for the ternary MgO-"FeO"-SiO2 up to 1500°C is well established limited experimental data are available in the MgO-"FeO"-SiO2-Al2O3 system, which is relevant to commercial operation of the process. A methodology has been developed for the experimental investigation of the liquidus temperatures for the multi-component system MgO-"FeO"-SiO2-Al2O3-Cr2O3 in equilibrium with metallic iron. Experiments have been carried out using high temperature equilibration, quenching, followed by electron probe X-ray microanalysis (EPMA). Liquidus temperatures have been determined in the silica primary phase field in the composition ranges directly relevant to the Cerro Matoso S.A. ferro-nickel smelting slag. Liquidus isotherms have been determined for temperatures between 1450 to 1600°C. The study enables the liquidus to be described for a range of MgO/FeO ratios. It was found that liquidus temperatures in the silica primary phase field decrease significantly with the addition of AI2O3. Keywords: Liquidus temperature, ferro-nickel, pyrometallurgy, smelting

Jan 1, 2004

By N. Tsuchida

Sumitomo Metal Mining Co. Ltd. (SMMC) is currently developing the flowsheet to treat stockpiled limonite, a type of laterite ore, at Rio Tuba on southern Palawan Island, Philippines. The new plant will be commissioned at the end of 2004. Rio Tuba Nickel Mining Corporation (RTNMC) has been mining saprolite since 1977, and the limonite ore located above the saprolite ore body has been stockpiled separately according to nickel and magnesium content. Ore from these stockpiles will be blended and used for the operation. The annual production of nickel will be 10,000 metric tons for the next twenty years. The proposed process consists of ore preparation, high pressure acid leach (HPAL), counter- current decantation wash, impurity removal and sulfide precipitation. Precipitated mixed sulfide will be processed to electrolytic nickel by the Matte Chlorine Leach Electrowinning (MCLE) process at Niihama, Japan. SMMC has established new technologies during the process development, such as zinc removal and sulfide precipitation. Applying this technology, preferential removal of zinc can be achieved by hydrogen sulfide gas with negligible loss of nickel. Precipitation of nickel by hydrogen sulfide gas is carried out at low temperature. Slow kinetics is selected for control of the particle size of the precipitated mixed sulfide. Keywords: HPAL, Zinc Removal, MS Production

Jan 1, 2004

By Naixiang Feng, Shaohu Tao, Zhihui Wang, Yuezhong Di

"A novel vacuum aluminothermic reduction lithium process was developed in present work which used lithium carbonate, alumina and calcium oxide as raw material. The process mainly contained three steps. The first step is that LiA102 clinker is prepared in ambient environment, then metal lithium is vacuum extracted from LiAl02 clinker with aluminum power as reducing agent, and the last step is that alumina is leached from the reduction residue with a mixture of sodium hydroxide and sodium carbonate. The results show that the lithium reduction ratio can be over 95% under the conditions of reduction temperature 1423K, reduction time 3h, and aluminum excess 20%. The main components of reduction residue are CaO· Al203 and 12Ca0·7Alz03. The alumina leaching rate of calcium aluminate in residue is over 80%. High-whiteness aluminum hydroxide can be obtained by carbonation precipitation of the reduction slag leaching solution.IntroductionWith a density about half of water, lithium is with the lowest density of all solids, mere 0.5 g/cm3 at 20 °C [l]. Lithium is widely used in aerospace, aviation, nuclear-generated power and electric battery industry. Nowadays, over 90 % of the world's primary lithium is produced by molten salt electrolysis [2-4]. But the development of molten salt electrolysis will be effected by some factors: cost, environment, and so on. Vacuum thermal reduction may be used extensively in future because of its low-energy consumption, high-purity and short-cycle."

Jan 1, 2013

By Tao Zhang, Wen-tao YU, Hai-bin ZUO, Jian-Liang Zhang

Sintering-pot tests and metallurgical performances of sinter with 4 kind of different Al2O3 contents are experimented in this paper. Results show: when the Al2O3 contents increase from 2.0% to 3.5%, acicular calcium ferrites in mine phase will be gradually replaced by plate-like iron calcium. The increase of Al2O3 contents will lead to the addition of liquid viscosity and the reduction of permeability of sinter bed. Sintering time will be prolonged. The rate of yield is stable basically but production is low; besides, the increase of liquid viscosity will decrease of drum strength. The change of permeability of the material layer will make RDI +3.15 decrease first and then increase when Al2O3 contents changed from 2.0% to 3.5%. RI of sinter shows a contrary trend because many open voids are formed by deterioration of liquidity first and then pores closed.

Jan 1, 2015

In low carbon TRIP steels, the formation of carbide-free bainitic ferrite is crucial for the stabilization of austenite. Based on experimental investigations modeling the bainite reaction is examined adopting diffusional and displacive mechanisms, as well as the semi-empirical JMAK approach. Transformation tests were carried out to study the isothermal austenite decomposition into bainitic ferrite for a model steel containing 0.6wt%C, 1.5wt%Mm and 1.5wt%Si which replicates the composition of remaining austenite at the start of the bainite reaction in a classical C-Mn-Si TRIP steel. In the diffusional approach, classical nucleation theory is employed and subsequent growth of bainite plates is modeled using the Zener-Hillert theory. In the displacive approach, the autocatalytic nucleation of bairtite plates is assumed to be rate controlling. The predictive capability of all models is evaluated for temperature ranges where different morphologies of bainitic ferrite have been detected, The shortcomings and inherent challenges associated with either of these modeling approaches will be delineated.

Jan 1, 2003

By Y. Wang, L. Liu, G. Xu, Y. Lv J. Sheng H. Zhang

In order to increase the service life of large scale coke dry quenching furnaces, the damage mechanism of lining was investigated, and the structure and properties of lining refractories used in cooling section were researched. The results showed that the abrasive wear volume of lining bricks at one fourth height section under skew tunnel was smaller than other sections. The wear loss of mullite brick and dense clay brick used in the lining of cooling section were respectively 8.02 cm3 and 11.65 cm3 in fifteen minutes. The mullite brick was laid with clay brick alternatively. By the different wear rate, the surface of lining was rough and uneven in the later service life, and short brick was easily dropped from lining. During the service, the basis wore off more easily than the aggregate. It is necessary to improve the wear resistance property, which will increase the service life of cooling section’s lining for coke dry quenching furnaces.

Jan 1, 2016

By Mike Trovant, Stavros A. Argyropoulos

"A fixed grid numerical model for phase change problems is proposed. The model solves for heat transfer and fluid flow, via the coupled solution of the energy, continuity and momentum equations. In addition, the numerical scheme accounts for temperature varying thermophysical properties and determines the shrinkage profile resulting from phase and density change. Simulations are run to determine the effect of varying model parameters and wall cooling rates on the location and shape of the shrinkage void formation in cylindrical casts. Results are shown for both aluminum and magnesium.IntroductionThe mathematical modeling of phase change processes (be they solidification or melting problems) entails solving for many interrelated phenomena. A comprehensive numerical simulation of the casting of a metal, for example, would have to account for: (a) heat transfer in both the solid and liquid portions of the metal and in the mold, (b) the release of latent heat during phase change, (c) fluid flow behavior in the liquid portion of the metal, (d) temperature induced shrinkage caused by liquid contraction and solidification contraction, and (e) the development of thermal stresses with accompanying shrinkage in the solid portion of the cast and mold. A schematic of the relationships that exist between the coupled equations which govern solidification is shown in Figure 1."

Jan 1, 1994

By G. C. Gullo, H. Wabusseg, P. J. Uggowitzer, H. Kaufmann

"The basic concept of New Rheocasting (NRC) is described and the application of wrought alloys with this process is discussed. Practical experiments with the aluminium alloy AIMgSi I are explained. For this alloy the proper NRC - casting temperature was determined by using Thermo Cale - computer software and DT A and the essential processing conditions are shown. In the experiments the melt was taken from an aluminium holding furnace and cast into NRC steel cups. After controlled cooling the resulting slurries were cast into a 4-step die on an UBE HVSC 350 Squeeze Casting machine. The characteristic microstructural values such as grain size and shape factor were measured and compared with classical casting alloys. The influence of the wall thickness of the step part (6 mm, 10 mm and 14 mm) on the microstructure is described. Tensile properties in different heat treatment states are compared with characteristic prope1ties of the same alloys in forged condition. The ew Rheocasting - process CNRC)The NRC process is a recently developed new semi-solid processing method which allows the production of pore-free, pressure tight components.In the NRC process a fu lly liquid, but only slightly superheated melt is taken from a holding furnace and poured into specially designed steel crucibles, which are placed on a carousel next to the Vertical Squeeze Casting machine. In this ,NULL,slurry maker'· globul ar a-Al grains grow, following forced homogeneous nucleation at the cup wall [ 1, 2]. In the few minutes during which the melt is cooled to sem i-so lid processing temperature, a stable ske leton of a-Al phase forms. The resulting slug keeps a cylindrical shape during its slide into the sleeve of the Vertical Squeeze Casting machine, where it is cast into shape."

Jan 1, 2000

By Andrew Case

The Port Nickel facility in Braithwaite, Louisiana, is known for pioneering hydrometallurgical processes for the 'separation and recovery of nickel, cobalt and copper. Ten years ago, in 1985, a new CRI-MET process for the recovery of molybdenum, vanadium, nickel, cobalt and alumina from spent catalysts was developed and implemented. Spent- catalysts from the petroleum industry consietute the majority of feed. These are not only a valuable-source of metals, but due to EPA regulations are frequently classified as hazardous under RCRA. Molybdenum and vanadium are selectively leached in an oxidative hydrothermal step. Alumina is then extracted in a caustic digestive leach. The unique technology produces four primary commercial products l molybdenum trioxide, vanadium oxide, aluminum trihydrate and nickel-cobalt concentrate. This paper discusses the process, modifications. during ten years of operation, and the relationship of these modifications to the future of the catalyst recycling business.

Jan 1, 1995

By Jaeheon Lee

Gold-copper alloys are shown to form during the cementation of gold on copper in a solution containing 0.25M [S2O32-] at 25oC. The alloy composition is strongly dependent on the initial Cu:Au ratio in solution and ranges from Au3Cu to AuCu3. XPS results for Au, Cu, S, and O are reported as a function of depth through an entire deposited film with an initial solution containing 20 ppm [Au] and 30 ppm [Cu]. The deposit contained about 20 atomic % gold and was predominantly Cu3Au. Underpotential deposition (UPD) theory is discussed as a mechanism for explaining the formation of these alloys. Several other systems that produce alloys during contact reduction/cementation are also discussed.

Jan 1, 2003

By Åke Saudström

An EAF dust sample generated in a scrap based steel mill was treated by a combination of hydro- and pyrometallurgial techniques. The EAF dust contained mainly ferritic spinels forming solid solution phases according to the general chemical formula (MnxZnyFe1-x-y)Fe2O4 and other oxide phases such as ZuO. CaO and Ca2Fe2O5. The EAF dust was first treated by hydrochloric acid leaching at p8=3 which dissolved 63% of the zinc. The pyrometallurgical treatment of the leaching residue was studied using an induction heating system to simulate some important operations of EAF smelting of the residue in combination with steelmaking. The leaching residue was mixed with carbon powder to obtain a mixture with 52.1% ZnFe2O4 and 175% carbon. The mixture, scrap, and slag former were charged together in a crucible and heated to attain a melt temperature around 1650°C. The effects of different amounts of mixture on the zinc balance and iron recovery were examined. Based on the test results, suggestions are made for the EAF recycling procedure of the leaching residue.

Jan 1, 2003

By Zeng Zheng, Liu Chen, Yu Xing-Fu, Tian Su-Gui, Zhang Chao

"Single crystal nickel-base superalloy is prepared by using the various withdrawing rates. By measuring creep properties and microstructure observation, the influence of the element segregation on creep properties of the superalloys is investigated. Results show that the dendrite spacing and the segregation extent of the elements decrease with the enhancing withdrawing rate. The superalloy with smaller dendrite spacing has lower segregation of the elements and better creep resistance. The dislocations climbing over the rafted y’ phase is thought to be the deformation mechanism of the alloy during steady state creep. In the later stage of creep, the fact that some dislocations shear into the rafted y’ phase may twist the rafted y’ phase. As the creep goes on, the initiation and propagation of the cracks occur up to occurring creep fracture, which is thought to be the fracture mechanism of the superalloy during creep.1. IntroductionSingle crystal nickel-based superalloys consist of high volume fraction of ?? strengthening phase and ? matrix, and possess the excellent high-temperature mechanical and creep properties, therefore, they have become the main material to make the blades of the advanced aeroengines[1-3]. Some literatures report that the temperature-bearing and creep-resistance properties of the single crystal nickel-based superalloys can be remarkably improved as the increases content of the refractory elements, such as W and Re[4-6]."

Jan 1, 2012

By Dae Jin Ha

Sticking phenomenon occurring during hot rolling of two STS 430JlL ferritic stainless steels was analyzed by hot-rolling simulation tests. The sticking started from the initial nucleation stage in which the rolled materials were stuck onto the roll specimen surface, proceeded to the growth stage in which stuck fragments grew further, and reached the saturation stage. The modified 430JlL steel had a smaller number of sticking nucleation sites and slower growth rate than the conventional 430JlL steel because of higher high temperature hardness, thereby leading to less serious sticking. When the simulation test was conducted at 1070 °c, Cr oxides were formed on the surface of the rolled materials, and thus the sticking was drastically reduced because of the increased surface hardness of the rolled materials. In order to prevent the sticking, high-temperature properties of the rolled materials should be enhanced when rolled at 900°C or 1000 °C, and rolling conditions and alloying compositions, under which the oxide formation was promoted, were more important than high-temperature properties when rolled at higher temperatures than 1000 oC.

Jan 1, 2008

By Kun Wang, Xinhui Li, Huaqing Xie, Qingbo Yu, Qin Qin

"Three typical model compounds of bio-oil (ethanol, acetone and phenol) were studied in the steam reforming process for hydrogen production. In the thermodynamic analysis, the three componds showed the similar trends. The hydrogen yields increased with the increase of steam/carbon (S/C) ratios, and the temperatures of the maximum hydrogen yields moved afterward to low temperature zone. However, the hydrogen contents were just about 70%. For improving hydrogen yield, a new system for steam reforming of bio-oil with site CO2 capture was put forward. This system required the catalst with the larger granularity having greater mechanical strength and higher abrasion resistance. So, six Ni-base catalysts loaded on Al2O3 particles prepared were used and among them, Mg-Ni/Co catalyst showed the best catalytic performance. For the simulated bio-oil (the mixture of the compounds), the hydrogen yield can attain 63% with Mg-Ni/Co catalyst with the good stability and regeneration ability.IntroductionCurrently the interest in the use of hydrogen as a clean energy carrier is increasing, and the main way for producing hydrogen is steam reforming of fossil fuels, containing steam reforming of nature gas, naphtha and coal. But this way caused substantial amounts of CO2 emitted, and these sources of hydrogen which are non-renewable energy will eventually be used up [1, 2]. As a kind of renewable energy, biomass is recognized as an attractive alternative to fossil fuels, because of its neutral CO2 emissions [3]. There are mainly two thermochemical processes using biomass to produce hydrogen, gasification and flash pyrolysis followed by steam reforming (SR) of the biooil produced in the flash pryolysis process [4]. The latter was known as one of the most promising and economically viable methods for hydrogen production [5]. In the last decades, the biomass flash pyrolysis technology was adequately developed and fairly mature [6]. But the steam reforming of bio-oil is still at the research stage and yet has been leading to more and more concerns by the researchers. In their research, the catalysts were widely studied and yet mainly were powdery[7-10], and the reactors manily were fixed bed reactors[11-13], readly causing the carbon deposition and the catalyst deactivation, against the continuous running. In this paper, a new systerm was put forward and could realize continuous production of hydrogen, yet needed catalysts with the larger granularity having greater mechanical strength and higher abrasion resistance, as well as powdery CO2 sorbents which mainly calcium oxide based ones.In this paper, the thermodynamic analysis of the steam reforming processes of three typical bio-oil model compounds (ethanol, acetone, phenol) was performed, and the effect of S/C ratio and temperature on the hydrogen yield and the compositions of gaseous products were investigated. Then, a new systerm for steam reforming of bio-oil with site CO2 capture was put forward, and the catalysts with a certain granularity were prepared and studied."

Jan 1, 2014

By C. Lupi

"The energy consumption of copper production by electrowinning, generally represents more than 1/4 of the total energy requirement in hydrometallurgical traditional process (roasting, leaching, purification and electrowinning). The considerable saving can be achieved just in this step that requires about 2.2 kWhlkg of the produced copper. To save energy the cell voltage, or more appropriately its anodic component, can be reduced: that is because the anodic voltage represents the main component of cell voltage and so it is largely responsible for the excessive energy consumption in copper sulphate electrowinning.In this work some ways are studied to lower the anodic voltage. First the cobalt ions were added to the sulphate solution in order to study the catalytic effect on oxygen discharge. Then lead alloys anodes (Pb-Ag, Pb-Sb-Ag and Pb-Ca) were used to promote a better oxygen evolution as a result of a different anodic surface. Their behaviour was compared with the PbSb traditional ones. Finally, as already pointed out by several authors for zinc electrowinning, ethylene glycol was employed as anodic depolariser in order to verify its effectiveness in the case of copper electrowinning. By combining all the above-mentioned ways, energy saving ranging from 20% to 27% is achieved.All the tests were carried out on a laboratory pilot-plant for long time to simulate the industrial conditions. The obtained copper deposits were observed by SEM to highlight their morphology."

Jan 1, 1997

By Adam C. Powell

A new Cahn-Hilliard phase field model of transport-limited electrochemistry describes phase boundary motion due to oxidation and reduction reactions at metal-electrolyte interfaces. Benchmarks demonstrating the accuracy of the method include open circuit voltage and closed circuit current in metallothermic reduction, and linear stability theory in metal electrolysis, including a new stability criterion for reduction of liquid metal from liquid electrolyte. The model is applied here to understanding cathode interface stability in titanium electrolysis e.g. in the SOM process developed with Uday Pal, and to structure evolution in subhalide reduction of titanium dichloride by magnesium developed by Toru Okabe. Potential for application to new fuel cell and battery systems is also discussed.

Jan 1, 2006

By Garry W. Warren

The brass foundry industry produces a significant amount of waste sand containing Cu, Zn and Pb which is often classified as a hazardous waste due to Pb content. The potential application of a hydrometallurgical process to treat the sand by extracting metal values and thus detoxifying the material has been investigated. The process involves leaching of metal values followed by cementation. The emphasis of this investigation was on the leaching step, although some preliminary cementation experiments have been performed. In order for any alternative treatment scheme to be successful, the smaller size fractions of the sand must be addressed. Experiments have been performed on five individual size fractions using various lixiviants HCI, acetic acid and HCI/NaCI. Cu extraction was found to be slower than either Zn or Pb. Results obtained in this investigation indicate that copper is present in two forms, an oxide form which dissolves rapidly and is insensitive to the level of oxygen, and a less soluble form, probably metallic which dissolves more slowly and requires an oxidizing agent. The presence or absence of oxygen had no influence on the rate of Zn dissolution indicating that zinc is present mostly in oxide form. Toxicity Characteristic Leaching Procedure (TCLP) tests showed that residues could be produced which meet the toxicity limit for lead. Preliminary cementation experiments have also demonstrated the feasibility of Cu and Pb recovery.

Jan 1, 1991

By Amy Nelson

In the electrolytic production of zinc, cobalt is removed from the zinc electrolyte by cementation with zinc dust prior to electrowinning. Although the thermodynamics for this reaction are favourable, kinetic barriers to cobalt reduction render the method almost useless in practice unless activators such as copper and antimony or arsenic are added. There is a large body of work studying the effect of these additives, yet the mechanism by which they act is still poorly understood. Even when the target conditions are met, zinc dust consumption is excessively high: satisfactory operation requires up to 300 times the stoichiometric amount of zinc dust. The objective of this work is three-fold: (1) to examine the effects of activators and elucidate the characteristics that make a good activator; (2) to identify new additives that could lead to a more efficient purification process; and (3) to test the new additives with synthetic and real electrolyte solutions. The present paper gives a status report on this project.

Jan 1, 1998

By Jan Petter Maehlen

Solid H-absorbing materials are in focus of ongoing R&D to offer viable solutions for the hydrogen storage and supply systems aimed on use of hydrogen as energy carrier for automotive transportation. Low operating pressures, combined with high gravimetric and volumetric efficiencies, together with fast kinetics of hydrogen release at ambient temperatures (providing conditions for a low energy loss due to decomposition), are the most important features of the ?ideal? H storage material. Hydrides of the light elements are the only possible candidates to build systems with an overall efficiency similar to those accommodating liquid or compressed (700 bar) hydrogen. One promising material from this point of view is aluminium trihydride, alane AlH3 with a gravimetric storage capacity of 10 wt.% H. This work was focused on studies of the crystal structure and thermal decomposition of alane by application of powder synchrotron X-Ray diffraction.

Jan 1, 2006