Search Documents

By E. Salinas Rodríguez, I. Rivera Landero, E. G. Palacios Beas, J. Hernández Ávila, E. Cerecedo Sáenz, M. A. Mesinas Romero, M. I. Reyes Valderrama

For this study, a sample of 5 g of copper powders obtained by grinding printed circuit boards of computers fixe to 50 mesh (270 μm) according Tyler® series was used. This sample was wholly characterized by XRD, SEM–EDS and AAS. The leaching medium used wasO2S2O3 2. From the evaluated variables it was obtained an apparent order of the reaction of n = 2.34 s−1, whereas according the effect of partial oxygen pressure it was obtained an apparent order of reaction of n = 0.9516 and the activation energy of system was of 6.5 kJ mol−1, the results so achieved suggest a transport control to the solid–liquid interface. Under certain work conditions such as: S2O3 2 ¼ 0:5M, 500 mL, 750 min−1, P/PO2 = 1 atm, 338 K, 5 g of sample and 9000 s of reaction time, it is possible get up to 97.35% of leached copper.

Mar 1, 2017

By B. C. Blakey

The economic feasibility of the sulphuric acid pressure leaching route for the extraction of nickel and cobalt values from limonitic ores is highly dependent upon the behavior of aqueous aluminium. This is primarily due to its precipitation as hydronium alunite ((H30)A13(S04)2(OH)6), which is one of the major scale-forming compounds found in autoclaves used for pressure leaching. As a result of renewed interest in the pressure leaching process, an investigation of the aqueous-solid eqilibria in the aluminium-sulphate-water system under acidic (< pH l), high temperature (230 to 270°C) conditions has been conducted. Pure hydronium alunite was synthesized in an autoclave by leaching boehmite (A100H) at elevated temperatures in sulphuric acid solutions initially 0.25 to 0.75 m H2S04 in concentration. Spontaneous, in situ precipitation of hydronium alunite followed. A high temperature solution speciation model was used for the analysis of the resulting solubility data in order to calculate equilibrium constants for the precipitation reaction.

Jan 1, 1994

By José Antonio, Silva Souza, Luis Alves Venancio, Emanuel Negrão Macedo, Antonio Ernandes M. Paiva

"The production of alumina from bauxite using the Bayer process generate 1.25 ton of the residue known by red mud and 460 kg of CO2 per ton of alumina.The direct use of exhaust gases from the alumina refineries to react and neutralize the bauxite residue may allow a double gain: open a wide range of new applications for bauxite residue reducing the reactivity of red mud and sequester approximately 15% or 67 kg of CO2 per ton of alumina.This paper shows the reaction of a suspension of bauxite residue-water with a simulation of the calcinator exhaust gases of the refinery. The influence of the temperature and the ratio water red mud is also analyzed.2 IntroductionThe production of millions of tons per year of alumina around the world generates around 1.25 tones of the residue known as red mud and 0.4 ton of CO2 per ton of alumina . The vast majority of the red mud is stored in large sealed lakes. Due to the high reactivity is considered dangerous and currently there is no operating process capable of reuse all the material at any refinery. These lakes after filled of solid material eventually have the surface revegetated. Otherwise will need monitoring for decades and remain as an environmental passive. The search of a industrial process that combine the reduction of the CO2 emission and the reduction the pH of the red mud opening the possibility of use in large scale in a economically viable way is the main objective of this work.The use of the exhaust gases of the refineries to neutralize the bauxite residue may allow a double gain: Open a large array of new applications for the residue with the reduction of its reactivity and sequester million of tones of CO2 plus other gases like SO2 [7] and NOx.This project main objective is to study the reaction of the CO2 with the Bayer process residue in order to obtain the basic parameters to design an equipment capable of process this reaction on a pilot scale. With this objective compositions of red mud on spray were processed with flow of gas containing CO2 at different temperatures and with concentration similar to the exhaust gases of the calcination process of the refineries. With the results, basic concepts of a pilot scale equipment were evaluated.A revision of the work already done on this type of residue were done [3, 9, 10]. Alternatives and potential barriers on chemistry and environmental fields were discussed. With the objective of industrial application the potential use of these materials were evaluated through the pH control, mass balance and x-ray diffraction."

Jan 1, 2010

By Satu Strömberg

Four different nickel concentrates were oxidized in a laboratory scale laminar flow furnace in simulated flash smelting conditions. The major nickel- and iron-bearing minerals in the con- centrates were pentlandite, violarite, gersdorffite, and pyrite and pyrrhotite, respectively. Thermal decomposition, ignition and oxidation behavior of nickel and iron sulfides were examined by using optical and scanning electron microscopy. General reactivity of the concentrates was monitored with sulfur removal which was most effective in violarite-based concentrate. Pentlandite-concentrates needed higher experimental temperatures for complete desulfurization and gersdorffite-based concentrate contained 5 - 10 % of the original sulfur even in the most oxidizing conditions studied (1 100°C, 50 vol-% 02). The reactivity of the iron minerals was found to depend on the other minerals present in the concentrate. In this paper, the observed re- action products and mineralogical changes are presented and preliminary conclusions of possible reaction mechanisms of nickel-bearing minerals are discussed.

Jan 1, 1997

By G. G. Barbante

Copper anode slimes are a valuable source of the precious metals, and selenium and tellurium. They are mineralogically complex and this has led to a great variety of process flowsheets for treating them. The traditional pyrometallurgical method utilises oxidation in a reverberatory furnace, but has numerous shortcomings. Recently deep-bath intensive smelting methods have been developed for use in the larger refineries. Despite these process advances, the thermodynamics of the reactions involved remains poorly understood. An initial description of the thermodynamics of slimes smelting is presented, but is severely limited by a lack of basic data. It is shown that slimes smelting is superficially similar to copper converting, but has many unique features. More basic thermodynamic data on selenium-based systems are needed before the process model presented can be further refined, and work in this direction has already commenced.

Jan 1, 1994

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 R. M. Reynolds

Engitec Impianti, S?.p.A. of Milan, Italy has successfully designed, constructed and has in operation state-of-the-art battery breaker systems at two European locations. A third facility i:s partially completed in Toronto, Ontario, Canada. The CX system crushes whole batteries, separates the various components and desulfurizes the battery paste. The system also produces sodium sulfate from the sulfuric acid and lead sulfate contained in the batteries. Actual plant operating data indicates that the desulfurized paste contains less than 0. 6 percent sulfur and less than 0. 5 percent antimony. The CX system utilizes mechanical screening and an up-flow hydrodynamic separator to accomplish the component separation. Sodiwn hydroxide or sodium carbonate is used for desulfurization. The sodium sulfate brine is evaporated and crystallized to produce clean anhydrous sodium sulfate suitable for use by detergent or glass manufacturers. Plant data also indicates that an increase in furnace productivity of about 25 to 30 percent is achieved using feed from the CX system. The desulfurized paste is very suitable for electrolytic processing as an alternative to pyrometallurqical processing.

Jan 1, 1990

By Bin Xu, Qian Li, Qiang Zou, Yongbin Yang, Long Hu, Tao Jiang, Xuefei Rao

The recovery of palladium from the chloridizing leaching solution of spent Pd/Al2O3 catalyst was studied mainly by sulfide precipitation tests and chemical composition analysis. The effects of key parameters including sodium sulfide concentration, pH, addition rate, temperature, and stirring speed on palladium precipitation efficiency are systematically investigated and optimized.

Mar 1, 2017

By C. E. M. Meskers, U. Boin

"The increasing use of coated magnesium in consumer products results in creation of coated Mg scrap during product manufacture and after End-of-Life product treatment. Currently this material is generally not recycled, leaving a material resource unused. Closure of the magnesium cycle in a sustainable manner is necessary. In order to do so, the effect of coatings on the recycling process has to be quantified, predicted and minimized. For this purpose metrics have been developed, based on first principles supported by detailed understanding of the recycling process. The developed 3D metric enables quantitative assessment of the recyclability and links coating design, product design and recycling to each other in a visual manner. The parameters that form the metric can be measured and predicted, hence an engineering basis for Design for Sustainability of coated magnesium is provided.IntroductionEvery product progresses through the four phases of the product life cycle depicted by figure 1. In each phase residues are created. Their amount and composition is largely determined by the complex material combinations created/invented during product design in the manufacture phase. Compared to the ideal cycle the magnesium cycle is far from closed (fig. 2). Most noticeable is absence of the link between the EoL phase and raw materials production. A closed cycle only exists for class 1 scrap, which goes from the product manufacture phase directly to production from industrial material and returns to the manufacture phase as magnesium alloys. The four problematic streams are marked by ???. Coated semi-products are present in two of the four residues, namely in rejects and collected scrap. When these semi-products are recycled the amount and composition of the dross and salt slag residue is affected as well.During product design selection of the coating takes place, fixing the coating character¬istics and properties from this moment on for the rest of its life cycle. The choices made in the manufacturing phase are therefore critically linked to the recyclability of coated semi-products as well as the sustainability of the magnesium cycle as a whole. Sustainable closed life cycles, in which the quality of materials is preserved and residue creation and resource depletion are minimized, can be attained by selecting the appropriate alternative during product design. To realize this the effect of design choices on the life cycle and more specific the recycling process has to be known and quantified."

Jan 1, 2008

By Ruixuan Zhang, Yan Li, Shusen Cheng

The measurement of raceway temperature in the blast furnace is a critical issue, which is very significant for judgment of, prediction and diagnosis of the racewa yburning state. This paper deals with mathematical models by Monte Carlo method to approximately simulate the radiation heat transfer in the race-way and establish matrix equations using CCD cameras, which are solved to obtain the three-dimensional temperature field. Due to the existence of fluctuation error, CCD camera measurement error and others,this is analyzed and random error is added in the measurement data to demonstrate the effectiveness and stability of the reconstructed temperature field. The results show that the reconstructed three-dimensional temperature field of the raceway is very close to the exact temperature.

Mar 1, 2017

By Wang Yun-yan

In order to examine the adaptability and the kinetics of leaching different gold ores in alkaline thiourea system, six kinds of gold concentrate and/or calcine with different physical and chemical properties were chosen as objects. The leaching behaviors in alkaline thiourea system with high stability, acidic thiourea system and alkaline cyanide system were compared. Changes of phase, surface appearance, particle distribution and specific surface area of six kinds of gold ores before and after leaching were studied in virtue of modern analytic techniques, e.g., XRD, SEM, and so on. The results indicate that alkaline thiourea solution can be used to leach gold ore, for oxidized gold concentrate removed arsenic by microbe pretreatment(4#) the leaching rate of gold is up to 82.68%, such conclusion overthrows the parlance reported that pH value must be less than 1.78, or gold can not dissolve in thiourea solution. Chemical components and phase are related to gold leaching rate, different gold ores are fit for different leaching system, and alkaline thiourea solution is suitable for the pretreated oxidized gold ores with low content of sulfur and in which the main phase was SiO2, phase almost does not change after leaching basically. Generally speaking, when leaching in alkaline thiourea solution, surfaces of gold ores with glaze change greatly to ones with coarseness, distinct trace and holes of corrosion. Particle size decrease and specific surface area increase of gold ores after leaching in alkaline thiourea solution with high stability except gold concentrate of Zhongyuan gold smelter(5#).

Jan 1, 2006

By Jilai Xue, Jun Zhu, Baisong Li

"TiB2-C/C Function Gradient Materials (FGM) is used in cathode materials to improve aluminum wettability and melt penetration in aluminum electrolysis. In this investigation, FGM was tested for use as part of the cathode materials, where a 10 mm thick TiB2-rich layer was on the top as an Al-wettable surface, the TiB2-C layers in the middle as a gradient layer and the carbon on the bottom as a base. Electrical resistances ofFGM were determined in the temperature range of25- 9600C in argon atmosphere. The results show that the present of TiB2-C gradient layer can reduce the open porosity and the electrical resistance of the cathodes materials at elevated temperatures. The cathode samples after aluminum electrolysis usually demonstrates an increase in electrical resistance, but the application of FGM layer can compensate such an increase for certain extend due to less variation in porosity and lower the level of melts penetration.IntroductionCarbon is still used for aluminum reduction cathodes dominantly, but it has a poor wetting properties by liquid aluminum and the anode-cathode distance has to be kept about 4-5cm with an additional 1.3-2.0 V voltage drop [l]. TiB2 has better wettability by liquid aluminum with higher electrical conductivity and stronger chemical resistance to the electrolyte attack. And the wettability ofTiB2-C composites cathode on liquid aluminum can be also improved, while liquid aluminum can completely wet the cathode surface ifTiB2 content exceeds 27% [2-4]. However, during the process of TiB2-C composites cathodes preparation and aluminum electrolysis, the deformation by temperature variation or sodium penetration are great disparity between TiB2 and carbon due to their physical properties difference. This will accelerate the cathodes cracking and deterioration."

Jan 1, 2013

By Juliana Augusto Molari, Deborah Dibbern Brunelli, Leonardo G. de Andrade e Silva, Patricia N. S. Poveda

There are several additives aimed on improving the processing characteristics as well as mechanical properties of the plastic materials. Being polypropylene is one of the main polymers used in the plastic processing industry due to its easy processability and application versatility, was chosen as the base resin for this study. Additives can aid the processing of polypropylene, either by promoting a better slip between the chains (lubricants), or by contributing to nucleation and crystallinity (nucleating). In this study, the raw materials copolymer polypropylene, lubricant (internal and external action), organic nucleating agent (metallic salt) and inorganic nucleating agent (metallic oxide) were considered. Mechanical tensile tests, Charpy impact and spiral flow to verify melt index were performed to characterize the samples with additives and standard (copolymer polypropylene). The interference of these additives with polymeric matrix was observed.

Mar 1, 2018

By Guiming Yang, Xiaoxian Huang, Zhiyun Ji, Min Gan, Lishun Yuan, Xiaohui Fan, Zhiyuan Yu

"The roasting characteristics of hematite pellets containing MgO were studied where magnesia powder, serpentine and magnesite were used as magnesium-additives respectively. The mechanical strength of both preheated and roasted pellets decreased when MgO content increased, which implied the addition of MgO had an adverse effect on pellet consolidation. By adding flux containing CaO, the mechanical strength of both preheated and roasted pellets were improved. The addition of calcium flux facilitated the formation of calcium ferrite and provided a certain amount of liquid phase, resulting in faster diffusion ofMg2+ and Fe3+. The result showed that diffusing speed of Mg2+ was enhanced by 1.48 times, and rate constant of Fe203 crystalline growth was enhanced by 62% when basicity was around 0.4. Improvement of mineralization degree and recrystallization of Fe203 assisted in consolidation of hematite pellets containing MgO.IntroductionOxidized pellets are ideal iron-bearing burdens in blast furnace. At present, magnetite is the main raw material for oxidized pellet production in China. However, as the rapid development of iron and steel industry, resources of magnetite have been depleted and cannot satisfy the requirement of pellet production. Using hematite concentrates to produce oxidized pellets has become a trend [1, 2]. Many pellet enterprises abroad nowadays have adopted high proportions of hematite concentrates when producing oxidized pellets, e.g. the percentage is 100% in a lot of Brazilian factories [3, 4]. But high proportion of hematite concentrates will lead to low mechanical strength and high reduction swelling index of pellets. Some studies show that Mg-bearing pellets have excellent metallurgical properties, and the reduction swelling phenomenon can be solved by adding fluxes containing MgO [5, 7]. However, there are problems such as low pellet strength and bad roasting characteristics for MgO-bearing pellets, which remains an obstacle in pellet industry. Hence, it's vital to undertake the study on strengthening measures for indurations of Mg-bearing hematite pellets."

Jan 1, 2013

By Sibin Zhang, Shengli Wu, Youhao Yin, Yuandong Pei, Zhixing Zhao, Jiangshan Shi, Zhengyun Fan

Spraying medium to achieve an energy-saving and emission reduction for iron ore sintering has been researched, such as spraying natural gas, coke oven gas, oxygen, sintering flue gas and gas from annular cooler. This paper focuses on effect of spraying steam on sintering surface on reduction of NOx and dioxin emissions in practical sintering production in Shougang Jingtang. It can be found that, with the increase of sintering bed spraying steam amount, NOx and dioxin of flue gas showed a decreasing trend. As spraying steam 1 t/h for 550 m2 sintering machine in Jingtang, NOx content decreases 2.6–9.5 mg/Nm3, and dioxin decreases 0.007–0.014 TEG ng/Nm3.

Mar 1, 2018

By M. Firdaus, M. A. H. Shuva, M. A. Rhamdhani, G. A. Brooks, S. Masood, M. A. Reuter

Declining grade of primary ores and resource efficiency have led us to process more alternative metal resources such as e-waste. One of the processing routes for extracting valuable metals from e-waste is through the black copper smelting. However, the underlying knowledge of the thermodynamics behaviour of the valuable metals contained in e-waste during smelting are limited which prevent us from developing an optimised process to recover all the metals. These different metals clearly will have different favourable conditions for their extraction. To illustrate this, the distribution behaviour of germanium (Ge) and palladium (Pd) between liquid copper and ferrous-calcium-silicate slag during black copper smelting was analysed. It was demonstrated that oxygen partial pressure and slag composition affect the partitioning of these metals to the copper phase and the favourable slag chemistry for recovering these metals is opposing. Considering the available thermodynamic data of these metals, an analysis for the optimum conditions is presented.

Mar 1, 2017

By Lin Li, Wen Shi, Hua Wang

"Specimens of the ultra-low carbon bake hardening steel were soaked for 1 min to 5 min, and then cooled by water quenching. The internal friction experiments were carried out to detect the spectra of the specimens. Results show that Snoek peaks are present in all the specimens, however, an obvious Snoek-Koster peak is found only in the 5 min-annealed specimen. Besides, tensile results indicate that the bake hardening values increase with the annealing time prolonging from 1 min to 3 min, but decrease as the annealing time prolongs further to 5 min. The solute distributions in the specimens were characterized by three dimensional atom probe. Some segregated C and V are found in the 1 min-annealed specimen, and the C and V contents decrease as annealing time prolongs to 5 min.1. IntroductionAs an excellent member of automotive body panel materials, various types of bake hardening (BH) steels have been developed since 1980s. Bake hardening property, as one of the most important mechanical properties, has been studied by many researchers [ 1-5]. As is known, BH phenomenon is generally controlled by the interaction between solute C and dislocations. The Snoek peak of internal friction (IF) is very popular in the investigation of solute C [6-9]. However, result of internal friction cannot suggest the distribution pattern of solute C as well as its influence on BH phenomenon.Three dimensional atom probe (3DAP) can diagnose solute element atoms as well as nano-sized precipitates, and it is the only instrument that currently can identify the identities of individual atoms in a material and measure their spatial coordinates with the resolution close to 0.3 nm [10]. There have been a number of studies about using 3DAP to detect solute elements as well as nanometer sized precipitates [11-19]. For example, Hono et al. [16] used 3DAP to determine the solute elements in an age-hardened Mg-Ca-Zn alloy, and they also obtained the distribution patterns of the observed elements."

Jan 1, 2011

By Wei Yu, Tiejun Chun, Jian Pan, Deqing Zhu

In this paper, improving the pelletization of Brazilian hematite by adding a boron bearing additive was carried out, and the pelletization parameters were also optimized. The mechanism of boron bearing additive was revealed in the kinetics of crystal grain growth by using LEICA microscopy and its software to measure hematite grain growth. Good qualities of green balls are manufactured with drop numbers above 5.7 times/0.5m, compressive strength higher than 13 N/pellet and thermal shock temperature over 620? under the following conditions: 1.2wt% bentonite, 0.4wt% boron bearing additive, 7wt% moisture and pelletizing in disc for 15 min. When the green balls were preheated at 1000? for 8 min and fired at 1280? for 15 min, the compressive strength of the fired pellets containing boron bearing additive is about 3096 N/pellet, which is far beyond the standard requirement for good quality pellets. Compared to the fired pellets without adding any boron bearing additives, the compressive strength of fired pellets containing boron bearing additive is increased by 1225 N/pellet. It is revealed that adding boron additive into the hematite pellets help to form more liquid phases, lower the activation energy of the hematite grain growth by 135.2 kJ/mol and increase grain growth rate by 33.6%, leading to higher strength of fired pellets due to forming more coarse and dense recrystallized hematite and energy saving by firing at lower temperatures for shorten time.

Jan 1, 2011

By Kuniaki Murase

Cadmium telluride (CdTe) semiconductor has been well investigated as a CdS/CdTe heterojunction solar cell material since its band gap is suitable for energy conversion from sunlight into electricity. In this paper a new electrochemical processing of thin-layered CdTe using basic aqueous electrolytes is reviewed from the standpoint of thermodynamics using a potential-pH diagram. The cathodic electrodeposition of the stoichiometric CdTe with a flat surface morphology took place at more positive potentials than that of the Nernst potential for the bulk-Cd deposition and at more negative potentials than that for the hulk-To. In this potential region deviation from the stoichiometric composition of eleetrodeposited CdTe was controllable by the Cd(II)/Te(IV) concentration ratio, pH, or concentration of complexing agent for Cd2+ ions of the electrolytes, The deposition behaviors for ammoniacal media were well accounted for by the potential-pH diagram of the Cd-Te-NH3-H2O system devised by a combination of those of the Cd-NH3-H20 and the Te-H2O systems, Diagrams for other complexing agents, ethylenediamine and diethylenetriamine, were also constructed to investigate and discuss the electrodeposition conditions regarding the corresponding media.

Jan 1, 2003

By Mark Cross, Diane McBride, Nick Croft

Extractive metallurgical processes rate amongst the most complex from the perspective of computational modeling. They typically involve multi-phase and multi-component fluid flow in very complex geometries, heat transfer driven by a number of interacting phenomena, solidliquid- gaseous phase change and mass transfer together with complex thermodynamics and associated chemical reactions. Beyond the model building itself, key challenges have always involved being able to identify the phenomena present together with interactions to characterize processes and experimental laboratory and plant data to parameterize the arising models – it is in this milieu, which require considerable process understanding and subtlety of thought, that David Robertson has made his contributions. We will review the achievements, over the last couple of decades, in computational modeling of extractive metallurgical processes and address some of the remaining challenges to enable simulation based process design, as we move through the 21st century.

Jan 1, 2014