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By P. Kim, M. Tangstad, T. Larssen, R. Kawamoto

The reduction rates of MnO and SiO2 were investigated for various charge compositions. The empirical activation energies of MnO and SiO2 reduction from SiMn slags were calculated between 1500 and 1650 °C under CO atmospheric pressure. The amounts of metal produced at different temperatures were compared, and the Arrhenius plots were described for each slag A, slag B and synthetic slag, which shows that the raw material have significant influence on the reduction rate. The rate of Mn-produced in slag A was faster than slag B despite of the relatively lower driving force. The lower rate constant in slag B implies that other kinetic factors, such as viscosity, affects the reduction rate. The estimated activation energies of MnO were 920, 304 and 975 kJ/mol MnO for slag A, slag B and synthetic slag, respectively. The rates of Si-produced were similar and slow for all slag types. However, the different activation energies of SiO2 between industrial ores and synthetic materials implied that the trace elements can have catalytic effects toward SiO2 reduction in SiMn slags. The estimated activation energies of SiO2 reduction were around 800 kJ/mol for slag A and slag B.

Mar 1, 2017

By M. Oliazadeh

Spodumene [LiAl(Si2O6)] is the most common and desirable economic lithium-bearing mineral due to its high lithium content. In Canada, there are several spodumene deposits at the development stage that have the potential to help narrow the forecast lithium supply gap stemming from the widespread acceptance and increasing use of electric vehicles. Spodumene processing can be conducted using Dense Media Separation (DMS), flotation or combination of both. If spodumene liberation is sufficient at coarse particle sizes, DMS can be used for primary lithium concentrate production and silicate gangue minerals rejection. If liberation is not sufficient, flotation is then the main processing route for spodumene concentration. Even in cases where DMS is a viable beneficiation option, flotation may still be required to process the DMS middlings and/or the undersize fraction which is outside the particle size range for DMS. Considering flotation as a technique for spodumene beneficiation, there are several alternatives including the use of mechanical flotation cells, column flotation cells, coarse particle flotation cells, and/or Staged Flotation Reactors (SFR), either alone or in combination. Ore sorting can be incorporated at the start of the spodumene flowsheet to remove gangue minerals, particularly amphibole and pyroxene in the early stages. The main objective of flowsheet development for hard rock lithium deposits is to evaluate the ability of these options to produce a spodumene concentrate with a concentrate grade above 6% Li2O, lithium recovery of above 80%, and with the minimum operating and capital cost. This paper aims to describe the various processing options available for the beneficiation of spodumene from hard rock deposits and compare the associated operating and capital costs for each.

By Marion Dattilo

The search for an improved anode for the electrowinning of lead from fluosi1icic acid medium has led the U.S. Bureau of Mines to investigate composites. Polymer bonded metal oxide powders which may contain catalyst additions were prepared by pressing. These composites display an improved activity toward the oxygen evolution reaction over electrodeposited lead dioxide on titanium, carbon, and nickel substrates. These composite electrodes contain 5 to 10 wt. " binding polymer, with the balance being metal oxides. Lowered anodic potentials achieved using the compnsite anodes resulted in lower levels of lead dioxide deposition during electrowinning.

Jan 1, 1995

By Srinath Viswanathan, Adrian Sabau

"In general, the occurrence of microporosity during metal casting is due to the combined effects of solidification shrinkage and gas precipitation. The governing equations for fluid flow and hydrogen evolution indicate that porosity formation and fluid flow are strongly coupled. However, in most studies on microporosity, it is considered that the porosity formation does not influence the fluid flow in the mushy zone. In this study, a computational methodology is presented for the numerical simulation of interdendritic fluid flow and microporosity evolution. The solution algorithm presented includes a fully coupled, implicit treatment of microporosity and local pressure in the mushy zone. The effects of microporosity evolution due to the local pressure drop in the mushy zone, and pore expansion in casting regions where liquid feeding alone cannot compensate for the solidification shrinkage are also considered. It is shown that neglecting the effect of porosity formation on the pressure in the mushy zone yields higher pressure drops. By its growth, microporosity partially compensates for the solidification shrinkage, reducing the feeding demand. A reduced feeding demand requires less fluid flow to compensate for solidification shrinkage, and results in smaller pressure drops in the mushy zone. Therefore, in order to accurately describe casting defects, comprehensive models of fluid flow, heat transfer, and solidification must include the effect of microporosity as well.IntroductionIn the terminology commonly used by foundrymen, porosity is usually considered to be either ""hydrogen"" or ""shrinkage"" porosity. Hydrogen porosity is the term given to porosity that is generally rounded, isolated, and well distributed. Porosity that is interconnected or clustered, and of an irregular shape corresponding to the shape of the interdendritic region, is usually termed shrinkage. In general, the occurrence of microporosity in aluminum alloys is due to the combined effects of solidification shrinkage and gas precipitation [1]. Continuum models [1, 2- 7] have been used to predict the level of porosity in castings. A number of other studies have also attempted to understand the phenomena of porosity formation and pore growth [8-10] and pore morphology [11].The governing equations for fluid flow and hydrogen evolution indicate that porosity formation and fluid flow are strongly coupled. However, in most studies [4, 9, 10], it is considered that the porosity formation does not influence the fluid flow in the mushy zone. Kubo and Pehlke [3] presented a methodology for the prediction of microporosity distribution in shaped castings by considering the effects of both the hydrogen precipitation during solidification and the pressure drop in the mushy zone. In their approach, the local pressure and porosity were computed in an uncoupled manner based on a ""flux of interdendritic liquid"" criterion, i.e., either pressure or porosity was first computed using the other variable at the previous time step. Their approach has been used with little change in numerous studies [6, 12, 13]. Recently, Kuznetsov and Vafai [14] presented a fully coupled, one-dimensional model for the computation of pressure and porosity. They showed that neglecting the effect of porosity formation on the pressure in the mushy zone yields higher pressure drops and an over-prediction of final porosity. They also showed that the influence of porosity formation on the pressure is larger at lower pressures in the mushy zone."

Jan 1, 2001

By Rajesh Kumar Mishra

About 500,000 troy ounces of Platinum Group Metals (PGM) will be available for recycling each year from spent automobile catalytic converters in North America alone. Platinum Group Metals? from spent catalyst can be extracted by Hydrometallurgical, Pyrometallurgical or Gas Phase volatilization processes. This paper is a review and comparative study of various processes investigated for PGM extraction. A number of processes described in this paper have already been commercialized. The technical and environmental aspects of the important processes are discussed.

Jan 1, 1989

By T. T. Chen

This mineralogical study is based on samples from typical "wet" nickel laterites of humid tropical to sub-tropical regions. An in-situ nickel laterite sample from Goro and a transported laterite sample from Plaine des Lacs, New Caledonia, are predominantly limonitic. Two-thirds of the particles in the Goro sample are <10 um in size; they consist of skeletal goethite and serpentine, as well as minor amounts of talc, gibbsite, chlorite, quartz and clay minerals. The coarser grains are mainly Cr-spinel, serpentine, gibbsite and Mn oxide. Nickel occurs mainly in goethite, serpentine and Mn oxide; cobalt occurs in goethite and Mn oxide. The Plaine des Lacs sample is finer-grained and contains more Al and CO3, but less Mg and Si than the Goro material. The sample contains more kaolinite, chlorite, siderite and feldspar, but less serpentine and gibbsite than the Goro material. Nickel is detected mainly in goethite, serpentine, Fe-Mg silicate and Fe-Mn oxide. The Indonesian ore from Sorowako, as sampled from the reduction kiln feed containing some reverts, is predominantly saprolitic, with apparent particle sizes ranging from <100 um to > 1 cm. The sample of reduction kiln feed is rich in Mg silicates, Mg-Fe silicates and goethite, and exhibits complex alteration textures. The nickel contents vary from particle to particle. Nickel is present mainly in serpentine, olivine, chlorite and amphibole, and in subordinate amounts in goethite and Mn oxide. Cobalt is detected in the Mn oxide. Keywords: Nickel Laterite; Mineralogy; Nickel Carriers; Goro, New Caledonia; Plaine des Lacs, New Caledonia; PT Inco., Sorowaki, Indonesia

Jan 1, 2004

By D. M. Hausen

The term "auriferous pyrite" relates to an association of gold with pyrite in a variety of textural forms that affect metallurgical treatment. Extraction of the gold depends not only on the grain size and distribution of the gold in the pyrite, but also on the crystal size and surface area of the pyrite. Occlusions of medium to coarse gold may be liberated by moderately fine grinding. The amenability of finely dispersed (submicroscopic) gold depends in part on the activity of the pyrite surface for oxidation. Two types of auriferous pyrite at Carlin, Nevada, have been examined by optical microscopy and SEM methods before and after aqueous oxidation test work to show how differences in morphological features can affect rates of oxidation and amenability to gold extractions by methods of chlorination and low temperature oxidation.

Jan 1, 1981

By Hidefusa Takahara, Koichi Miyake, Dierk Raabe

"Mechanical properties of copper wires were examined. The copper wires containing 5-10 mass % chromium and 1-3 mass % silver were produced through heavily cold deformation. It was expected that the copper wire was easily fractured during cold deformation because of the existence of brittle chromium phase in the alloy. In fact, the copper wire was fractured due to large work hardening, when the true strain [n] exceeded 5. However, the copper wire annealed at 1273K for 6 ks ·in the middle of deformation process could be smoothly drawn to 11=8. After precipitation treatment for silver phase at 473k for 1.8 ks, the wire was able to further drawn to n=8.4. The final deformed wire showed tensile strength higher than 1200MPa.IntroductionDownsizing of electronic devices has led to the demand of finer and higher strength materials for cables. Conventional copper alloys have about 800MPa in ultimate tensile strength. These strength are mainly obtained by precipitation hardening. Nowadays, a process for higher strength wire has been developed, where dual phase copper alloy is used. When it is drawn heavily, the' second phase is elongated along drawing direction and the wire gets high strength due to fiber reinforcement (1). That alloy is so called in-situ formed fiber reinforced ·alloy. Cu-Ag(2), Cu-Nb(3) and Cu-Cr(4) systems are well known as such alloys. It is also well known that chromium is brittle material except single crystal and high purity of chromium. However, Mihara et al. C5l have achieved 1 GPa in ultimate tensile strength in the Cu-Cr-Zr and Cu-Cr-Ti alloys by appropriate thermo-mechanical processing.In this study, the Cu-Cr-Ag systems were investigated: The alloys contained 10 or 5% chromium and 3 or 1 % silver. It was demonstrated that silver precipitated in copper matrix contributed on further hardening."

Jan 1, 2000

By Huimin Lu, Neale R. Neelameggham, Guangzhi Wu

In China’s Inner Mongolia Tuquan County, 1.4 billion tons of reserves of serpentine deposits were found. Because serpentine belongs to magnesium silicate, there is no good reducing agent to reduce magnesium. In the local there is also a large reserves of high-aluminum bituminous coal for thermal power, power plants each year produce a large number of high-aluminum fly ash. The aluminum-silicon alloys obtained from this high-aluminum fly ash as the raw material by carbothermal reduction method can reduce the magnesium from the serpentine. In this paper, first, the feasibility of producing aluminum-silicon alloys by carbothermal reduction of high-alumina fly ash was studied, the hypereutectic aluminum-silicon alloys were obtained; and then the investigation on aluminum-silicon alloy as a reducing agent to reduce of metal magnesium from serpentine was carried out. According to the previous investigation, the optimized technical process for the extraction of metal magnesium from serpentine was proposed.

Mar 1, 2018

By Yongbin Yang, Meixia Cai, Yufeng Guo, Guanzhou Qiu, Tao Jiang, Jianjun Fan

"A series of sintering and metallurgical experiments were carried out to optimize the blast furnace burden structure in this study. The results indicated that the sinter disintegrated seriously with basicity around 1.4, and after this “turning point”, the sintering properties were improved gradually with the increase of basicity of sinter. Based on the results, an idea was put forward which focused on producing two different kinds of sinter with different basicity. Different with the original burden structure of 85% sinter with basicity 1.4-1.5 + 15% pellets, an alternative new BF burden structure was proposed by the following structure?44% sinter with basicity 1.05 + 44% sinter with basicity 1.87 + 12% pellets. This new alternative BF burden structure has been adopted by some steel plants.IntroductionIn recent years, conventional blast furnace (BF) process was put into operation to produce hot metal in “A” steel plant. “A” steel plant owns two sets of sinter strands at present. Because the sinter production capacity exceeds the actual requirements of BF, a burden structure with 85-90% self-made sinter + 10-15% purchased pellets is adopted to take advantage of the low–cost sinter. But the serious problems encountered with the BF operators are that the sinter disintegrated easily during transportation and storage process. Therefore, the rate of return fines is very high after sinter being screened."

Jan 1, 2012

By E. W. Lithgow

Commercial volumes of nickeliferous laterite ores overlie part of a 90 km long belt of peridotites in central Dominican Republic. Protores are serpentinized harzburgites and dunites, with lesser serpentinite. The ore mineralogy consists mostly of goethite, serpentine-group minerals, quartz and poorly crystallized, x- ray amorphous materials. Minor constituents are hematite, gibbsite, olivine and enstatite. In the Ore Dressing plant the mine feed is subjected initially to proper sizing and blending to produce a homogenized mix. Subsequent drying and upgrading, by selective crushing and screening of rock fragments through a Barmac circuit, complete preparation of the ore for pyrometallurgical processing.

Jan 1, 1993

By Isauro Rivera Landero, Martín Reyes Pérez, Eduardo Cerecedo Sáenz, Javier Flores Badillo, Mauricio Guerrero Rodríguez, Juan Hernández Ávila, Eleazar Salinas Rodríguez, María Isabel Reyes Valderrama

During column flotation of mining tailings of the Dos Carlos dam, it was observed that the effect of surface liquid flow (JL) is a variable that determines the rate of rise of packing bubbles and therefore, causes the generation of gas retained within the columnar system. Also overall more stable laminar flows were observed, in a range of superficial flow of liquid in the bottoms stream (JLT) from 0.446 to 0.68 cm/s, showing the stability in the range of superficial gas flow (Jg) from 0.1 to 0.5 cm/s. Observing a uniform bubble size for the three JLT evaluated, with a diameter between 0.05475 and 0.2525 cm, at all the range evaluated of Jg. Furthermore, an uniform performance was obtained, and with the same rate of rise of packing bubbles, showing a greater packing bubbles at JLT = 0.446 cm/s, due to the lesser bubble size observed, in comparison with the values of JLT of 0.68 and 1.017 cm/s.

Mar 1, 2017

By S. Chama, P. Chishimba, Tina Chanda Phiri, J. Machona, S. Parirenyatwa, G. Kaluba, Y. R. S. Hara, D. M. Musowoya

The investigation focuses on leaching of copper (2 wt%), cobalt (0.5 wt%) and iron (2.4 wt%) from complex tailings material from the Democratic Republic of Congo. The highest recovery of copper and cobalt into the leach solution were 78 and 10%, respectively, under direct leaching with sulphuric acid. Higher recoveries (90% for copper and 96% for cobalt) were attained when the material was pre-reduced with coal for 1.5 h in the temperature range of 700–950 °C. The increased recoveries were due to metallisation of all the copper and cobalt which is in the silicate matrix. The effects of pre-reduction temperature and sample to carbon weight ratios were analysed and found to be important in; (i) achieving high recoveries of copper and cobalt and (ii) decreasing the amount of iron in the leach solution. The samples were characterised by atomic absorption spectroscopy and scanning electron microscopy (SEM) techniques.

Mar 1, 2017

By T. Shibaraki

A new larger, more efficient and economical Mitsubishi furnace line at Naoshima was put into operation in May 1991. Naoshima Smelter had produced previously about 230,000 mtpy anode copper with two smelter lines, i.e., a conventional reverberatory furnace line and Mitsubishi furnace line, which had been shutdown at the same time of the start up of the new smelter. At the beginning of the operation, there were several initial problems at the area of off gas trains and feeding system. By overcoming them now the process has been continuing satisfactory operation at the design rate. The paper describes about the design concepts and the actual operation of the new smelter.

Jan 1, 1993

By Heric Henrique Souza e Silva, Johne Jesus Mol Peixoto, Natalia Barros Barony, Itavahn Alves da Silva, Weslei Viana Gabriel, Carlos Antonio da Silva, Varadarajan Seshadri

In this work the circulation rates have been determined in a 1:7.5 scale physical model of RH reactor (Ruhrstal Heraeus) and using oil/water and oil/zinc chloride solution to simulate steel melt/slag in the prototype with the objective of evaluating the influence of density and viscosity on the entrainment of oil simulating slag. A technique based on strain gage bridge and particle image velocimetry was developed to assess the circulation rate, as the usual tracer method is not feasible due to the presence of chloride ions in ZnCl2. The critical velocity and critical diameter of oil drops for slag (oil) entrainment in water/oil and ZnCl2/oil systems were estimated using equations from the literature. Due to the difference in density, the ZnCl2/oil system, showed a critical velocity that is 28% higher than the silicone oil/water system while the maximum size of the entrained droplets was about 65% lower than that for water/oil system.

Mar 1, 2017

By R. T. Seaman

Pressure oxidative treatment of whole ores and/or mineral concentrates is used to leach or liberate metals of value for downstream recovery. Silver, when present, is often lost in processing, precipitating as a cyanide-insoluble jarosite in the residue. Depending on pressure oxidation conditions, the degree of silver loss to jarosite can vary dramatically. Batch bench-scale testwork is often performed to define that loss, and then assess the implications in continuous operations. This paper focusses specifically on the impact of CESL pressure oxidation conditions on silver recovery, and discusses limitations of batch bench-scale testing as well as means of overcoming these limitations to better predict silver recovery in the scale up from bench-scale to continuous operations. Since silver is only partially soluble in both sulphate and chloride media, it will gradually leach and deport to a jarosite as oxidation progresses. When a silver-insoluble anion, for example iodide, is dosed prior to oxidation, there is a marked improvement in silver recovery from batchgenerated residue; however, that benefit is not consistently seen in continuous operations. The difference has been attributed to the dynamic solution conditions in the batch test, specifically the first few moments of oxidation. Using these principles, a predictive correlation has been established between initial leach concentrations of iron and acid and ultimate silver recovery with iodide addition.

The viscosity of high magnesium content FeO-Fe3O4-SiO2-CaO-MgO slags at nickel flash smelting conditions was investigated using a commercial rotational viscometer. The studied parameters were compositions of slag and temperature. The viscosity of these slags was measured as a function of CaO, MgO, SiO2, FeO. Fe3O4 and Fe/SiO2 in temperature range from 1473K to 1723K. These slags contained 5.81 to 10.59 pct MgO, 0 to 10.37 pct CaO, 28.21 to 36.21 pct SiO2, 39.40 to 55.42 pct Fe and 1.1 to 1.5 Fe/SiO2.

Jan 1, 1999

By Z. Jing, C. Jun

High-purity Bi2O3 was prepared via extraction-preparation stripping method use BiCl3 leaching solution. Parameters such as oxalic acid concentration, phase ration, aging duration, feeding duration, were examined for their effect on the size and morphology of precipitate. The precipitate was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), particle size analysis, differential scanning calorimetry and thermal gravity analysis (DSC-TGA) and infrared spectroscopy analysis (FT-IR). Bi2O3 was characterized by elements analysis, particle size analysis and scanning electron microscopy (SEM). Bi2O3 product of 680 nm was obtained using 15 g/L oxalic acid, 1/1 phase ration, 0 min aging duration, 0 min feeding duration and calcinating at 500 °C for 2 h.

Mar 1, 2018

By Xuan Cheng

The electrochemistry of sulfide mineral flotation is reviewed with particular emphasis on galvanic interaction among minerals and grinding media, and its relevance to flotation of complex sulfide ores is discussed. Surface alteration due to galvanic interactions among chalcopyrite, pyrrhotite and mild steel is analyzed in terms of voltammetric and chronoamperometric studies on individual minerals and through galvanic current measurements in 2- and 3- electrode combinations. The results are related to laboratory flotation behaviors of chalcopyrite-pyrrhotite mixtures simulating copper-nickel bearing Duluth gabbro.

Jan 1, 1993

By B. Erik Ydstie, Tor Lindstad, Vianey Garcia-Osorio

"As a result of the high temperatures present in a Carbothermic Aluminum Process the content of aluminum and aluminum sub-oxide in the gases leaving this process is high. These gases as well as energy must be recovered. In a Vapor Recovery Unit were the aluminum compounds react in a series of Heterogeneous Non-catalytic Reactions forming solid, liquid and gas products. The different product phases depend on the temperature present in the system. In this work we present dynamic model of the Vapor Recovery Unit of a conceptual Carbothermic Aluminum Process. Because of the complexity of the system several models are developed and coupled to capture the essential physics of the multiphase reaction problem. A Shrinking Core Model describes the reaction mechanisms. Then material and energy balances are coupled with the thermodynamics properties from the FACT database of thermodynamic properties, resulting in a system of nonlinear Partial Differential Equations. In the paper we describe the model development and governing equations for the reaction mechanisms and fluid flow. Finally we review the numerical schemes created for the solution of the model system. The model can be used for control and design purposes.IntroductionThe Carbothennic Processes for producing Aluminum can be divided into two groups (Motzfeldt et al. (1989)) In the first approach pure alumina is produced and reduced to pure aluminum. In the second approach an alloy (e.g. aluminum and silicon) is made and then aluminum is produced from the alloy. The history of both processes has been described by Ginsberg et al. (1965). At least three aluminum producers began largescale testing of this process in the 60's Alcan, Pechey-Ugine and Reynolds. Alcoa did some smaller scale experiments.Alcoa was one of the first companies to produce aluminum by Carbothennic Reduction (Foster et al. (1956)) and US Patent 2,829,961 April 8, 1958. In this process a carbon containing molten aluminum phase was a floated on top of an oxy-carbide melt. During the cooling the dissolved carbon deposited as aluminum carbide. The carbide was then separated from the molten aluminum by a fluxing agent. This process was successful but economic unfeasible."

Jan 1, 2001