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By Baptiste Laubie

Agromining is a phytotechnology aiming at producing commercial metal compounds from low-grade ores thanks to hyperaccumulating plants. The fern Dichranopteris dichotoma is a rare earth element (REE) hyperaccumulator, which naturally grows on former mine tailings in China. It accumulates up to 0.35% of REEs in its aerial parts. Different hydrometallurgical processes are currently developed to recover these elements directly from the biomass or from ashes after combustion. The process presented here consists of a direct extraction by EDTA solution, followed by precipitation with acid oxalic. Optimal precipitation pH and influence of organic matter are determined by modelling and by experimental studies. The final solid contains 4.3% of REEs, with calcium as the main cationic impurity (0.45% of the precipitate). The recovery yield is similar for major REEs and is around 70%. After optimization, upscaling of the process will allow the agromining development to recover REEs from secondary resources with more environmentally friendly techniques.

By J. B. Wiskel, H. Henein

"A study was conducted to establish the effective heat transfer coefficient for a single molten droplet moving in a gaseous medium. Towards this objective, a series of quench experiments were performed on molten droplets of AA6061 aluminum generated with the Impulse Atomization technique (IAP). IAP is a single fluid atomization process capable of producing powders with a predictable mean particle size and a relatively tight standard deviation under controlled atmospheric conditions. Microstructure analysis of the atomized powder was used to establish the extent of pre-quench solidification. A mathematical model was then employed to correlate the Ranz-Marshall and Whitaker equations with the observed particle cooling behaviour. These equations were found to provide a reasonable estimation of the heat transfer conditions only when the variation in gas thermophysical properties across the boundary layer was accounted for in the model. This model formulation of droplet heat transfer has important implications with regards to active sprays and atomization processing operations IntroductionAn understanding of droplet cooling is important in atomization powder production. It is well understood that dendrite arm spacing is inversely proportional to cooling rate during solidificationl1l. Through modification of the heat transfer conditions during metal atomization, the microstructure of a powder maybe tailored to the end user. However, owing to the complexity of gas flow it is difficult to determine a heat transfer coefficient for a moving droplet. This difficulty is further compounded when complex jets and/or streams and their interactions are considered. To provide a base for these more complicated types of analyzes, two approaches have been employed to calculate the effective heat transfer conditions for a single droplet. In one approach, Megardis [ZJ developed a numerical model to investigate the heat transfer process of a free falling droplet undergoing laminar convective cooling. The effective heat transfer coefficient as a function of angular position was determined by numerically solving the fluid and energy equations for the system."

Jan 1, 1999

By Zhang Libo, Wang Xin, Peng Jin-hui, Ju Shaohua, Guo Sheng-hui, Xu Lei, Huang Meng-yang

"China is lacking high grade titanium ores. This work intends to leach impurities such as Fe, Ca and Mg from a low grade titanium ore, to increase the grade. The original material contained 65% TiO2 , 16.12% Fe, 9.4% CaO + MgO, 4.2% SiO2, 1.25% A12O3, and the particle size is between 0.053-0.045mm. Microwave energy was used to enhance the leaching effect. The results showed that when normal heating was used to leach the mineral, the extraction of impurities Fe, Ca and Mg was very low. However, when microwave energy is introduced, the extraction of Fe, Ca and Mg increased dramatically. The optimized conditions are: relative power 5W/g, the ratio of concentrate to HC1 isl5%, leaching at 160°C for 20 min with a ratio of liquid to solid 12:1 mL/g. The material obtained under these conditions contains 92.73% TiO2, 0.207% Ca + Mg, 0.8% Fe, with 94.6% Ti recovery. The poduct meets with the quality for boiling chlorine.IntroductionThe resources of titanium are very abundant, and are distributed all over the world. There are almost 140 minerals containing TiO2 with a content of more than 1%. However, there are only several minerals which can be used for producing sponge titanium. They are mainly rutile and ilmenite. The grade of nature rutile concentrates is higher than 95% TiO2, and it is a high quality raw material. But the resources of nature rutile are relatively low; after mining for many years, its resources are exhausting gradually. Although ilmenite reserves are great, ilmenite cannot be used as a raw material because of its low content of TiO2, only 45-70%; also it has a high impurity content of Ca, Mg and Fe. In these years, there is a tendency for titanium industry to use high grade concentrate."

Jan 1, 2012

By Eduardo Juncal, Jorge Alberto Soares Tenorio, Jose Roberto de Oliveira, Denise Crocce Romano Espinosal

"Steel industry has been expanding every year, consequently there has been an increase in waste generation in this area. Thus, companies in this sector are finding it difficult to give a correct destination of waste. For example, only in a basic oxygen furnace (BOF) converter are generated about l8kg of dust per ton of steel. The aim of this work was the characterization of dust generated in the BOF converter. The characterization was performed by chemical analysis (titration for iron and its oxides and Inductively Coupled Plasma Atomic Emission Spectroscopy for other elements), scanning electron microscopy, size analysis using Mastersizer 2000 equipment and X-ray diffraction. It was observed that dust is composed mainly iron in form of magnetite, metallic iron and wustite with approximately 99% of the particle size below 100 µm.IntroductionToday, steel is a important metal for the world. It can be produced for two routes, blast furnace/ basic oxygen furnace (BOF) converter and electric arc furnace (EAF) [1].First route, the iron is produced from the reduction of iron ore and coke for fuel injection and! or natural gas for a production of pig iron in blast furnace. The pig iron is sent until BOF converter to perform the blowing of oxygen to obtain the steel. In the second route, the steel is produced using scraps or direct reduced iron (DR!) using electric arc.During steel production are generated a lot of wastes like slag, sludges, scraps and dust [2]. Only in the first six months of201O, world steel production totaled 706 million tons [3]. According to Watson and Wang [4], some 10 to 20 kg of dust is generated per tonne of liquid steel produced. Thus, the reuse of these wastes can be a great to companies, because it reduces the amount of raw material to be extracted and reducing disposal costs [5,6]."

Jan 1, 2012

By R. Cameron

The growing use and acceptance of electric vehicles (EV), as evidenced by the record sales of over 750 thousand vehicles in 2016 and a current global EV stock of 2 million vehicles, is putting pressure on sourcing raw materials such as cobalt, and to a lesser extent, nickel. Global supply is poorly diversified, with 50– 60% of global cobalt production sourced solely from the Democratic Republic of Congo (DRC). One potential source for cobalt and nickel are low-grade nickeliferous pyrrhotite tailings, of which 50–100 million tonnes are present in the Sudbury area alone. This paper presents the extraction of cobalt and nickel from this material using a combination of flotation and bioleaching technologies. The findings of a high-level techno-economic analysis of the proposed processing flowsheet are presented.

By Anxiang Wang, Kunhua Wu, Yifu Li, Junjie Xu, Yongnian Dai, Bin Yang, Lingxin Kong

In this study, the saturated vapor pressures of tin (Sn) and antimony (Sb), the separation coefficient and the vapor-liquid phase equilibrium of Sn-Sb alloy were theoretically analyzed, which demonstrate that it is possible to separate Sn and Sb by vacuum distillation. The process parameters of vacuum distillation, including the distillation temperature, distillation time and alloy mass (thickness of raw materials) on the direct yield of Sn and the content of Sn in liquid phase were investigated by using single factor experiments. The preliminary results show that the direct yield and the content of Sn are 98.77 wt.% and 96.01% with the optimized distillation conditions of a distillation temperature of 1473 K, a distillation t ime for 45 min and a Sn-Sb alloy mass of 125 g ( thickness o f 8 mm). The distillation parameters in the study provide effective and convenient conditions on separation of Sn-Sb alloy.

Jan 1, 2016

By Helvio P. G. Santafé Jr., Ruben J. S. Rodriguez, Sergio N. Monteiro, Teresa E. Castillo

"The coir fiber extracted from the husk of the coconut fruits are worldwide available in tropical regions as a low cost lignocellulosic by-product for many applications including composite filler in automobile parts. Possible uses above room temperature require information on the thermal behavior of these coir fiber composites. Therefore, the objective of this work was to perform thermogravimetric, TGA and DTG, analysis on polyester matrix composites incorporated with different volume fractions of coir fiber. In general, it was found that thermal degradation associated with weight loss occurred in three stages. Changes were also observed in the DTG peaks that could be attributed to the coir fiber participation through the decomposition of its lignocellulosic structure.IntroductionThe development of new materials has always been motivated by the need of improved properties. This was the case of modem composites with combination of properties that surpass those of conventional monolithic metallic alloys, ceramic or polymers, from which composites are made. A typical example is the synthetic fiber reinforced composite with specific strength i. e, ultimate stress divided by density, higher than any other monolithic material. Today, however, our global society is concerned with serious environmental problems and thus demanding that new materials be developed with distinct characteristics. They are known as environmentally correct and are expected to be sustainable, which corresponds to the condition of being biodegradable, renewable, recyclable and neutral with respect to C02 emission, considered the main responsible for global warning [1]. Synthetic fiber composites cannot meet these requirements. Consequently, new composite reinforced with cellulose-based natural fiber are being developed [2-8] and are already replacing the synthetic ones in several engineering fields including the automobile industry [9-11]. These composites have additional advantages owing to the lignocellulosic fiber benefits of being diversified, abundant, less expensive, lighter and of societal interest [8]. In some cases even technical advantages such as non-abrasive effect to processing equipments and more flexibility exist in comparison to synthetic fibers."

Jan 1, 2011

By Henry Hu

In high pressure die casting processes, proper control of temperature die yields a high casting production rate and superior quality components, Die temperature is usually influenced by various die design and process parameters such as size and location of intemal water cooling lines, flow rates of cooling lines, and pouring temperature of molten metal. Among them, the cooling water flow rate plays a major role in controlling thermal pattern of the die_ In order to develop an effective control strategy, data of local die temperature must be collected and analyzed, In this study, a PC-based data acquisition and control system (DACS) for die temperature control has been designed, and established, The developed DACS has three input channels for temperature signals and one input channel for water flow rate signals, as well as one output channel for a water pump, and is capable of displaying data in both curve format and value format. Implementation of the DACS in a laboratory setup has also been attempted, It should be pointed out that more advanced control mechanisms can be potentially integrated into this system in future,

Jan 1, 2003

By Liang Li

Thermodynamic analysis and experiments were conducted in order to verify the feasibility of preparing crude titanium tetrachloride (TiCl4) via the carbochlorination of low-grade titanium slag in molten salt. Titanium slag, assaying 74.6 wt% TiO2 with high calcium and magnesium oxide impurities, was treated by an optimized carbochlorination process in NaCl molten salt. These impurities in the titanium slag were chloridized simultaneously, and chlorination products FeCl2, MnCl2, MgCl2, CaCl2 and CrCl3 were collected in the furnace slag. XRD and SEM/ EDS analysis of residue shown that SiO2 and Al2O3 in titanium slag were difficult to chlorinate completely. Theoretical calculations and industrial-scale experimental studies reveal the content of TiCl4 in the products was more than 98.8 wt% and thus proved the feasibility of utilizing low-grade titanium slag for TiCl4 preparation by molten salt chlorination technology.

By J. -P. Nepper

It has been possible to largely contain converter aisle emissions of SO2 and fumes in the case of batch-wise operated Peirce Smith converters during normal blowing periods with the help of suitably designed primary hoods. Controlling the escape of off-gas during the periods of turning the converter in or out of the stack has been problematic in the past. Effective automated control systems have been developed for the purpose and successfully applied in smelter operations in Spain, Taiwan and Germany. This has led not only to an effective reduction of emissions in the converter environment but also to an improvement in the converter operation.

Jan 1, 1992

By Manoj Kumar, Vinay Kumar, Nikhil Dhawan, Manish Wadhwa

"Electronic waste (e-waste) is a collective name given to discarded electronic devices such as Television, Cellular Phones and Personal Computers. Among the heterogeneous metals present in the e-waste are the base metals: copper, aluminium, nickel, tin, zinc, iron and precious metals: gold, silver, palladium, platinum apart from several hazardous and halogens metals. Hence there is a need to recover these metals from electronic scrap by recycling and then re-use, which can meet large amount of metals demand. Hydrometallurgical processing was employed for the recovery of metals from television printed circuit board (TV PCB). Different lixiviants such as hydrochloric acid, Sulphuric acid, and nitric acid were used to understand the dissolution behavior of copper, iron and lead present in the TV PCB. Effect of increasing concentration of nitric acid was also studied. Selective recovery of tin over 95% in the form of tin oxide was precipitated. The precipitated tin oxide was identified by X-ray diffraction technique. Tin oxide of purity more than 99.9% was obtained.IntroductionThe electrical and electronic industries comprising computers, television, mobiles, etc, which are manufactured utilizing printed circuit, boards, capacitors, resistance, soldering material etc. During production, at the end-of service life and degradation due to the advanced version with latest features generate valuable metallic and non-metallic constituents. European Union Council on waste electrical and electronic equipment (WEEE) has classified these into different categories as listed in Table 1 [Streicher-Porte et al., 2005]. Among these the information technology, telecommunications and consumer equipment constitute electronic waste (e-waste) [EC, 2002]. Almost all e-waste consists of an integrated part of printed circuit boards which is a valuable source of several metals such as copper, tin, lead, aluminium, iron, silver, gold, platinum etc. [Relay et al., 1990]."

Jan 1, 2008

By Carlos M. Fontes Vieira, Ruben J. Sanchez Rodriguez, Carlos E. Gomes Ribeiro

"In this study we attempted to model a response surface for the apparent dry density of ternary blends of calcitic marble particles. The crushed marble was divided into three granulometric ranges. Simplex network methodology was used to determine the mathematical relation between granulometric ranges and apparent dry density (ADD) of particle mixtures. A highly significant regression was obtained and the simplex network methodology proved to be able to predict high packing particle compositions.IntroductionProblems with packing and expected porosity of particles are common and widely recognized to be important in terms of both fundamental physics and engineering applications. For example, densification of a powder mass is important in the shaping of solids in ceramics, powder metallurgy or composite synthesis; chemical processes such as solid-liquid separation (sedimentation, thickening and filtration), raw material handling (stockpiling, blending, drying, storage and transportation) and pyrometallurgical processes (agglomeration, coke making, ore sintering, blast furnace iron making and new iron making processes) [1,2].Many factors can affect particle packing, but in practice, there are three main factors: (dimensionless) particle size distribution, particle shape and absolute particle size [2].Geometrical and practical methods were developed to predict properties in mixtures. Zou, Gan and Yu [2] present a paper treating a prediction of the porosity of multi-component mixtures of cohesive (fine) and non-cohesive (coarse) particles. Bahiense et al. [3,4] used a simplex network to determine a mathematical model for obtain the optimal compositions between aggregates to a greater packing of a ternary particles mixture. Despite these techniques for predicting particle packing, some studies in particulate composites production don't present clear criteria for choice of particle distribution [5,6]. As the best particle packaging depends on the size, distribution and shape of these particles, individual models can be constructed for specific combinations of these factors."

Jan 1, 2014

By Jing Zhan, Chuanfu Zhang, Yonglin Yao

"The Ni/Co arbitrary ratios of fibrous precursor were investigated during coordinated coprecipitation by changing the precipitating medium. The results show that the original molar ratio ofNi2+ to Co2+ in reaction solution can be maintained in the coprecipitate at pH'.'05.0 and the coprecipitate is single phase solid solution using water and water-X precipitating medium. But the original Ni/Co ratios are no longer kept and composition of the coprecipitate is not uniform at pH>5.0 in water precipitation medium. In order to obtain the precursors with the required morphology and accuracy Ni/Co ratios, the optimum conditions of fibrous precursors were chosen as follows: ammonia used as complex agent and pH adjustor, water-X solvent as precipiting medium, oxalate as coprecipitated agent, 8.0-8.4 for pH value, 50-70°C of reaction temperature, 0.5-0.8 mol/L of initial nickel and cobalt salt concentrations and excesses of oxalic acid of 10% - 20%.IntroductionNi-Co alloy as an important transition metal alloy with high mechanical strength, good anti-deformation, corrosion resistance, thermal conductivity, thermal stability, electrical conductivity, electrical contact, and special magnetic properties indicates that it can be used as high-temperature catalyst, special magnetic material, high-temperature electrochemical devices, and so on [1-6]. An ideal composite powder should have an appropriate stoichiometric ratio, good uniformity of chemical composition, appropriate phase, low impurity content and small particle size [7]. Similarly, the composition of nickel-cobalt alloy powder has an important impact on its crystal structure, properties and applications. Guo[8] found that magnetisms of CoxNi1-x such as magnetic anisotropy, curie temperature, and the shifts of the spin steering are very sensitive to the composition of alloy powder."

Jan 1, 2013

By Alice Barreto Bevitori, Frederico Muylaert Margem, Noan Tonini SImonassi, Caroline Oliveyra, Sergio Neves Monteiro, Isabela Leão Amaral da Silva

"The mechanical behavior and the fracture characteristics of composites with DGEB/TETA epoxy matrix reinforced with up to 30% in volume of continuous and aligned ramie fibers were evaluated by tensile tests. Specimens with selected thin fibers aligned along the tensile axis were room temperature tested to rupture. The fracture surface was analyzed by scanning electron microscopy. The results showed significant increase in both the ultimate tensile strength and the elastic modulus. The fracture analysis indicated the possible mechanism for the fiber/matrix interaction, which could be responsible for the composite performance.IntroductionSince the middle of last century, polymer composites have substitute many conventional monolithic materials in applications ranging from aerospace to sport [l]. The main advantages of these composites are the low density and flexible properties specially using fiber as reinforcement to suit the mechanical performance requirements [2]. These are usually high strength and stiffuess requirements that could be reached with synthetic fibers such as gloss, carbon and aramid fibers. Its most commonly used example is ""fiberglass"", i.e., a thermoset polymer matrix composite reinforced with glass fiber. Indeed, ""fiberglass"" has a specific strength of the order of 500 MPa.cm3/g, which is the double of the strongest steels like the maraging. This motivated, at earlier times, ""fiberglass"" to replace many conventional materials including wood and natural fiber composites. Today, ""fiberglass"" has a wide range of uses from aerospace systems and appliances to sport and leisure components. However, its fabrication as well as those of any synthetic fiber such as carbon and aramid composites, requires a relatively large amount of energy. Presently, a growing concern exists regarding the consequences to the environmental by gases like C02 associated with both the energy consumption and the processing of synthetic fibers and their composites. These gases are well known responsible for global warming [3]."

Jan 1, 2013

By M. E. Myers

An experimental program is being carried out to determine the thermodynamic characteristics of zinc solubilization in high-temperature iron and iron-carbon alloys. Two versions of an isopiestic technique are being used, with zinc at a lower temperature being equilibrated with pure iron foils or molten iron-carbon alloys at a higher one. The lower temperature sets the partial pressure of zinc vapor, and thus the activity relative to a given reference state. Initial results show Henrian behavior for dilute zinc solutions in austenite and a molten 4.6% C alloy, with unit-pressure solubilities in pure Fe that closely match the predictions of Wriedt.

Jan 1, 1992

By Mark Cross, Andrew P. Campbell, Koulis A. Pericleous

"Computational Fluid Dynamics (CFD) modelling is being used to simulate the freeze layers formed within direct smelting processes. There has been some concern whether water-cooled elements can withstand the p~ocess conditions and in particular abnormal cases where they may be splashed in molten metal.To validate the models being developed, two cases from literature have been modelled for solidification and stress analysis. The solidification case is presented in detail and is for hot molten metal flowing through a cylindrical pipe. The walls are at a temperature below the melting point for the metal. The resulting solid (or freeze) layer is within 3% of the value calculated by Sampson & Gibson9 •Preliminary modelling of the refractory-slag interactions is presented. Although three basic mechanisms: Penetration; Corrosion; and Erosion will eventually be modelled, only the penetration is considered here. The corrosion mechanism is to be modelled by tracking the time that the penetrated refractory is at the required temperature.Future work, after adding all the required physics, will focus on the modelling of a water-cooled element placed lower in the smelter. Process perturbations will be simulated to examine what these elements will withstand."

Jan 1, 2001

By Colin Dessemond

Since 1950, the traditional process has been dominating the production of lithium compounds from spodumene ores to sustain the lithium market because of its economic viability and the markets need for technical grade (99.5% purity) product. This traditional process includes thermal conversion, acid roasting and lithium leaching. However, this process has not been challenged and very few studies have tried to explain its limitation (95% lithium yield) or optimize the thermal treatment. Here, α to β spodumene conversion and lithium extraction were performed in a rotary kiln on a 2 mm to 2 cm spodumene concentrate instead of a micrometric one using a 1050 °C, 30 min conversion treatment and 250 °C, 30 min, 30% H2SO4 excess leaching treatment. X-Ray Diffraction analyses were performed on the converted material to determine the conversion rate by Rietveld analysis. It was observed after thermal treatment that the α-spodumene particles fractured and divided while the impurities remained compact. A sifting was performed after thermal treatment and it was determined that 65% of the initial mass became finer than 180 μm. X-Ray diffraction analyses and lithium content measurement were performed on both fractions and it was determined that the finer fraction had a very high lithium content of 3.24 wt%. Lithium extractions were performed on both fractions separately. While the coarser fraction’s lithium yield was only 61% the finer fraction’s lithium yield went up to 99% without any additional treatment. These observations may open more economical ways for the traditional process by potentially bypassing two third of costly steps such as grinding.

By Mônica Suede Santos Silva

This work describes characterization of the performance of the tundish of a six strand continuous casting unit of the Companhia Siderurgica Belgo Mineira, Joao Monlevade, Brazil using physical modeling. Permanent and transient conditions, due to ladle metal composition changes are considered. Pulse and step tracer addition techniques are employed to assess the control variables. For transient conditions the degree of inter-mixing and the minimum residence time are determined with a view to optimize the process especially during the grade changes of steel.

Jan 1, 2003

By Camila Martini Matos, Maria das Graças da Silva Valenzuela, Francisco Rolando Valenzuela Diaz, Lucy Gomes de Sant' Anna, Orley de Oliveira Magalhães, Flavio M. S. Carvalho, Isaac Jamil Sayeg

"Kaolin clays are widely used in various industry segments. Its main properties are fine granulometry, chemical inertness and whiteness. In general, kaolins are not easily organophiilized as a result of its 1: 1 structure. The aim of this paper is to describe the modification of a Brazilian kaolin sample, in order to obtain an organophilic kaolin of high performance. The clay as received was identified by X-ray diffraction and characterized by optical microscopy, cation exchange capacity and swelling tests for observation of their performance in water and organic solvents. Then, the sample was treated with a 10% sodium carbonate solution and with ammonium quaternary, washed several times with distilled water, dried at 60°C, and characterized by XRD and swelling assays. Our results show that the clay was organophiilized and its ability to swell in organic solvents has increased.IntroductionThe kaolin clay, also known as ""china clay"" is chemically a hydrated aluminum silicate characterized as a very fine powder and lamellar structure (1:1), being constituted mainly by kaolinite [l]. Kaolin is a mineral extremely used as raw material. Its properties such as color, softness, small particle size and chemical inertness make it a suitable material for several industrial applications. The desired properties of kaolin varies widely for each application, beginning with its largest use in the paper industry until minor uses in the sectors of cosmetics and pharmaceutics. These two last applications require purified kaolin with defined functionality [2]. To find improvements in the functionality of kaolin for specific applications is important for many industrial uses. Sometimes the way to find these improvements might be modification of the kaolin clay by treatment with a chemical substance as ammonium quaternary, causing surface modifications [3,4]. In this work is described the modification of a Brazilian kaolin sample by treatment with cetyl trimethylammonium chloride (CTAC). The properties of the modified kaolin are being assessed by characterization and essays to understand its functionality and industrial application."

Jan 1, 2013

By Lanre M. Oshinowo, André Bakker

"An understanding of the parameters that govern the just-suspended impeller speed, Njs, and the distribution of solids, is critical to the efficient operation of hydrometallurgical and other processes involving solid-liquid suspensions. In this paper, the distribution of solids in stirred tanks under a range of solids loadings (0.5 to 50 vol%) was predicted using CFD and validated against experimental data obtained from the literature. The multiphase flow is modeled using the Eulerian Granular Multiphase model. This paper will also review the established design parameter Njs in the context of scale-up and compare it to the quality of solids dispersion as a means of assessing correct scale-up in suspension tank design. The results of this study will describe a straightforward procedure to obtaining comprehensive information about reactor behavior with complex CFD models.The performance of hydrofoil impellers and a 45° pitched-blade turbine at suspending solids under different agitation speeds was studied. Both single and dual impeller operation have been evaluated. The settled solids fraction for speeds below N js, and the cloud height for impeller speeds above Njs were predicted. The CFD predictions are in good agreement with experimental literature data on velocity distribution and cloud height."

Jan 1, 2001