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By S. N. Monteiro, C. M. F. Vieira, M. M. Ribeiro

"This work has as its objective to evaluate the effect of incorporation of the powder waste retained in the eletrostatic precipitator of the sintering stage from an integrated steel making plant on the physical and mechanical properties of a red ceramic. Formulations were prepared with incorporation of the waste in amounts up to 20 wt.% into a kaolinitic clay. Rectangular specimens were prepared by uniaxial mold-press at 20 MPa and then fired at 750, 900 and 1050°C. The evaluated physical and mechanical properties were: linear shrinkage, water absorption and flexural rupture strength. The results showed that the waste has a potential to be used into red ceramics. The incorporation of the waste enhanced the properties of the ceramic, decreasing the water absorption and increasing the mechanical strength at all investigated temperatures.IntroductionThe sintering stage of an integrated steel-making plant is dedicated to the agglomeration of a mixture of iron ore, coke or coal, fluxes and water [1]. It is a common practice in this stage to use of solid wastes with great amounts of iron in the form of sludge and powder. One of the atmospheric pollutants generated during the sintering process is the particulate material, which is normally retained in an equipment denote as electrostatic precipitator. This equipment retains very small particulates, present in the gaseous emissions by application of an electrical potential difference in between the plates that the fluid is forced to go through. [2]."

Jan 1, 2011

By Jiang Feng, Zhang Libo, Peng Jinhui, Guo Zhanyong, Ju Shaohua, Lei Ting

The clean utilization of the residue containing chloride, CuCl residue, produced from zinc hydrometallurgy is very important for the recycle of valuable metals. And drying is the main process in recycling. In this study, response surface methodology was used to optimize operating conditions of the drying of CuCl residue in a convection oven and desirability function used as the methodology for the optimization. Optimization factors were air temperature (80–100°C), material thickness (10–25mm) and process time (80–120min) while investigated responses was final moisture content. The optimum conditions were found to be the temperature of 95.48°C with the material thickness of 13.47mm for the process time of 89.48 min. Under optimum conditions, the predicted moisture content of CuCl residue was 4.11% while the experimental date was 4.13%. The experimental value after process optimization was found to agree satisfactory with the predicted value. After drying, XRD was used to analyze the main phases of CuCl residue. The CuCl residue is made up of CuCl,Cu2O, ZnS and other compounds.

Jan 1, 2015

By Richard D. Hagni

Although the economically important uranium minerals are difficult to recognize under the ore microscope, they can be identified by a combination of qualitative and quantitative techniques. Useful quantitative techniques include indentation hardness, percent reflectance, spectral reflectance curves, and color coordinates. The latter two properties are especially distinctive for the primary urahlferous minerals uraninite, coffinite, brannerlte, and davidite. Together with the quantitative properties of indentation hardness and reflectance, the character and color of internal reflections are distinctive for many of the secondary uranium minerals. Ore microscopic techniques also provide an excellent means for determining the intergrowths of these minerals with other ore and gangue minerals. Such intergrowths are important to an understanding of the genesis of uranium deposits, and they may be important to uranium extractions.

Jan 1, 1981

By Zhou Jun

Water-quenched samples were taken from a commercial flash furnace at three levels along its reaction shaft during operation at high feed rate. The samples were subjected to a series of analysis and observation. Such processes of the feed in reaction shaft as oxidation, desulfurization, melting, slag and matte formation and etc., variations of particle size along axial and radical direction of the shaft are investigated. The following smelting mechanism in reaction shaft named as “Multi-particle and multi-phase fusion model” is proposed: (1) Fragmentation and collision of concentrate particles take place simultaneously in reaction shaft with particle size growing up. Collision produces large-size “unit melt” which falls into the reaction layer in the settler bath. (2) In the settler reaction layer below the shaft, weak bath smelting reactions take place among the shaft products, producing final matte and slag which separate into two layers. (3) The processes in the shaft are all progressive along the whole height of the shaft. The predominant reaction in the shaft is oxidation, not reduction.

By S. I. Sobol

The results of the study of the mechanism of a cathode process of cobalt electrolysis to explain disagreements in a form of kinetic equations of autoclave reduction of nickel and cobalt have been used.

Jan 1, 1993

By T. T. Natarajan, Nagy EI-Kaddah

"Numerical simulation of electromagnetic confinement systems generally requires large CPU time due to the strong coupling between the electromagnetic and the free boundary problems. The present paper examines the accuracy and the computational efficiency of the most common numerical schemes used in modeling such systems. Levitation melting was taken as a test case. In this study, a comparison was made between the finite element and surface integral methods for electromagnetic field calculations. The computational efficiency of Lagrange and the modified Hestenes methods for solving the free boundary problem were investigated. The convergence of the Lagrange method was found to be much faster than the modified Hestenes method. It was also found that finite element method not only gives accurate solutions, but faster convergence to the final equilibrium shape than the surface integral method. The applications and the limitations of these techniques in modeling electromagnetic confinement systems will be discussed.IntroductionIn recent years there has been a growing interest in the use of electromagnetic forces for confinement of molten metals as a means to eliminate molten metal contamination during melting and to improve surface quality of cast products. Continuous casting of metal without contact of a mold is now a reality, and is being commercially applied for casting of aluminum slabs /1/, and copper rods /2/. New applications of electromagnetic confinement in melting and casting include containerless melting (Magnetic Suspension Melting) /3/, edge containment in twin roll casting, and meniscus shape control in continuous casting of steel /4/.Modeling of confinement systems involves the determination of the electromagnetic field and the equilibrium shape. These two problems are strongly coupled due to the dependence of the field on the shape of the melt. While significant advances have been made in computational electromagnetics /5/, the application of developed computational techniques to electromagnetic confinement problems is not a simple task. The principal difficulty in using these methods is that the solution domain is not known a priori. due to coupling between the electromagnetic field and the free boundary problems. These two problems have to be solved simultaneously, leading to an iterative solution procedure. As a result, numerical simulation of electromagnetic confinement systems are computationally intensive with computational time at least an order of magnitude larger than the fixed domain problems."

Jan 1, 1994

By K. S. Raja, M. Misra, S. K. Mohapatra

"Ordered arrays of TiO2 nanotubular photocatalysts were prepared by a simple anodization process. Band gap states of the TiO2 were altered by controlling the anodization electrolyte composition and thermal annealing conditions that resulted in enhanced photo activity. These nanotubes were used for reducing CO2 to methanol either by photochemical or photo electrochemical routes. Pd nano-particle loaded TiO2 nanotubes were employed for photochemical reduction of CO2 to methanol that showed a conversion rate of 12 x 10-3 mol m- 2h-1. Carbon modified TiO2-xCx type nanotubes were used as photo anode and Ti as cathode for photo electrochemical reduction of CO2. The potential of Ti cathode was maintained at -0.5 V SCE. The formation rate of methanol was determined as 13 x 10-3 mol.m-2h-1.1. IntroductionGlobal warming due to emission of carbon dioxide is a serious environmental concern. The atmospheric concentration of CO2 is about 384 ppm by volume and about 3 x 1012 tonnes by weight. Burning of fossil fuels and deforestation are the leading causes for increase in the anthropogenic CO2. More than 32 x 109 tonnes of CO2 are released per year (based on 2006 data) worldwide from the fossil fuel. Pumping CO2 from the fossil fuel power plants into deep ocean basin is one of the most discussed disposal options. The other potential option is converting this green house gas into valuable fuels.Carbon dioxide feed stock can be converted into fuels of solid, liquid or gas phase by chemical, electrolytic, photocatalytic and photo-electrocatalytic methods. Reduction of CO2 to fuel form of any phase requires energy. The reduction process should be energy efficient so that we do not spend more energy and emit more (indirect) CO2 in the process of converting CO2. From this point of view, conversion processes occurring at room temperature look attractive.Electrolytic conversion of CO2 into various forms such as methane1, ethane2, ethylene3, methanol4,5, ethanol6, n-propanol, formic acid7, and formaldehyde has been widely reported. The standard equilibrium potential (at pH: 0) for reduction of CO2 to methanol is 0.14 VSHE and to methane is 0.2 VSHE which is thermodynamically more favorable than hydrogen reduction. However, the gas phase reduction is kinetically complex requiring effective electrocatalyst. The major issues with electrolytic conversion of CO2 to useful products are:"

Jan 1, 2010

By Bernd Kos

The management of waste materials in the aluminum industry is as important as in other basic industries. Due to the high value of the-by products of the melting process and their toxic properties we took the challenge to develop a process technology to reduce the environmental impact and to help industry to get a better yield of their by products/raw materials. In melting operations metal losses due to oxidation are nearly unavoidable, the amount of such losses, however, can be controlled. Aluminum dross actually is a by product and any shop would like to get rid of it in the most economic way. This by product still contains up to 70% valuable metal! In the present work we describe possibilities to separate metal and residues for further processing. Recycling of metal concentrates, selling of dross and dumping of the residues have been the typical solutions up to now. But there are technologies available which are designed to reduce the waste to a minimum or even avoid it altogether. Such alternatives are processing of the dross into materials which can be reused in other industrial processes in order to avoid any dumping. This can be done by separating the metal and the residues by centrifuging and further use of the residues in the chemical or refractory industry. ECOCENT means economical and ecological recovery of aluminum by centrifuging of hot dross. This process, developed by FOCON Austria, is based on the idea of treating the hot dross as quick as possible in a single operation to avoid exothermic losses, intermediate storage and unnecessary handling as well as to save energy. In the ECOCENT process the hot dross is fed without any fluxing salt additions into a converter where the relevant parameters for separation, like temperature and viscosity, will be adjusted. Further big lumps of dross are ground into smaller pieces in order to improve the later separation of the metal. After homogenizing and adjusting the temperature, the hot dross is poured as quickly as possible into a centrifuge. In the ladle or alternatively the mould of the centrifuge the centrifugal forces are used for the separation of aluminum from aluminum oxide, the major constituents of dross. The separated pure metal can either be discharged liquid or as solidified aluminum ring. The design of the device for the production of liquid or solid metal is almost identical. As soon as the centrifuging is finished the liquid aluminum can be poured back into the furnace or can be used for ingot pouring. After the pouring of the metal the "dry" residues are removed just by turning the ladle. Alternatively the aluminum solidifies in the mould and is discharged as a compact ring. The separation of the residues from the aluminum ring is automatic. Due to the batchwise operation the composition of the metal is the same as in the skimmed furnace of origin. The complete treatment cycle needs about 40 minutes. The recovery rate of aluminum is better than 90% of pure metal. This technology is highly flexible by its nature and can easily accomodate various operational requirements. The consumption of energy is more than 50% lower compared to conventional dross processing as the ECOCENT process is using the inherent energy of the hot dross. These extremely good results are not dependent on the aluminum content of the dross even from very dry dross most of the metal can be recovered. The main advantages compared to conventional dross processing are the high recovery rate, the known analysis of the metal and the immediate reuse of the recovered aluminum. The high recovery rate and the pure metal result in a short amortization period. The compact ECOCENT unit needs a minimum of space since extensive handling can be avoided. The electronically controlled process needs no cooling water and is simple, safe and environmentally sound. The residues are free of fluxing salts, their content of metallic aluminum is low and the environmental problems are thus greatly reduced.

Jan 1, 1995

By E. Kuzeci, R. Kammel

"Lately various voltametric methods have gained increased attention as an analytic tool in hydrometallurgy. Voltammograms with mercury drop electrodes or glassy carbon electrodes provide information about the electrocrystallization of cathodic deposits and allow calculation of kinetic data by means of characteristic parameters like the peak potential and peak current and their variation with the voltage scanning rate.Cyclic voltammograms are also suitable for identification of reaction sequences. Voltammograms with carbon paste electroactive electrodes containing metal sulphide additions reveal information about the dissolution behavior. The stripping voltammetry can be applied to analyze metal ions and organic additives (e. g., thiourea) in extreme low concentration. Typical application of the various methods studied with microcomputer controlled measurement system are explained by examples selected from copper hydrometallurgy.IntroductionThe use of electroanalytical methods in metallurgical process control can be dated back to the starting period of industrial copper refining, when the deposition of the metal ions was followed electro-gravimetrically by weighing the electrode with deposits (1). The principles of metal deposition and dissolution have not changed but the methods to follow these phenomena were subjected to noticeable developments and especially the introduction of polarographic investigations by Heyrowsky (2) has greatly contributed to the progress in electro-analysis. A review about the fundamental work on the electrochemical kinetics in earlier time is compiled in a monograph of Vetter (2). With the steady improvements in the instrumental techniques, it is nowadays possible to apply several current and potential modulations for measurements with improved selectivity and sensibility. There is however, still a lack in theoretical interpretation of the data obtained. More theoretical information are already available for linear voltametric methods for systems where reduced as well as oxidized species are dissolved in the electrolyte (4, 5). Some recent investigations have also shown the reliability of these techniques to study electro-crystallization (6, 7). Main fields of the application in the hydro - and electro-metallurgy are:"

Jan 1, 1989

By B. J. Elliot

The Outokumpu Oy flash smelting furnace was designed for a capacity of 69,5 mtph of concentrate. The history of developments on the flash furnace, from the original operating capacity of 55 mtph to a proven capacity of 115 mtph of concentrate, is summarised. The new feature of operation at BCL Limited is ?the use of screened lump coal reduction in the settler region of the furnace. This paper considers the effects of settler bath reduction on the furnace smelting capacity, the condition of the furnace ?lining and bath, and ,the slag losses generated from the flash furnace and ultimately to discard. By using the settler bath reduction technique the capacity of the furnace for smelting new concentrate has been increased by 15% and hearth accretion has been eliminated by direct reduction with coal, which has also allowed the generation of a substantial protective lining on the furnace walls and roofs. As a result of improved slag losses from lump coal charging the metal recoveries on the flash furnace have increased from 70% to 87% for nickel, 68% to 82% for copper, and 28% to 45% for cobalt.

Jan 1, 1983

By Priscilla Aki Mori de Hanashiro, Viviane Tavares de Moraes, Denise Crocce Romano Espinosa, Hugo Hashimoto

"The LCDs are used in televisions, calculators, mobile phones, computers (laptops and tablets), video games and other electronic devices. The advancements in technology make obsolete these devices, causing excessive disposal of LCDs and therefore decreasing life span of landfills. In this context, the LCDs from LED LCD TVs arise as an additional source of waste electrical and electronic equipment (WEEE). Thus, it is essential to develop LCDs recycling methods, beginning with the LCD characterization followed by displays processing, aiming the materials separation and using some Ore Treatment Techniques, and finally, the recovery of indium using acid leaching. The analysis methods that will be used in this work are: Fourier Transform Infrared (FT-IR) and Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES).IntroductionLiquid Crystal Display (LCD) technology is applied in modem televisions, calculators, mobile phones, computers and a wide range of electronic devices. It has replaced Cathode Ray Tube (CRT) technology as the most advantageous display product, due to lower electrical power consumption, size and weight reduction, and no radiation emission [ 1]. The constant improving of LCD screen technology reflects on its growing contribution to the amount of waste electrical and electronic equipment (WEEE): an estimated 50 million tons of WEEE are produced every year [2]. Once the most common method of its disposal are landfills, the LCD technology therefore became an environment issue [3].LCD structure is composed by components made by different materials. In order to develop a LCD recycling methodology that gives the right destination to these materials, a previous characterization stage is required. This characterization includes a disassembly process and material identification analysis. One of the LCD components is the screen, which is composed by polymeric and glass layers. The liquid crystal glass was the starting material of this study. It contains indium in the form of indium tin oxide (ITO) film. This ITO film is deposited in the glass by a sputtering process and acts as the electrode material [4,5]. It has in its composition 90% ofln203 and 10% ofSn02 [6]."

Jan 1, 2014

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 J. Tang, B. Q. Li, R. Akarapu

"An integrated model is developed to represent the three-dimensional electromagnetic wave propagation and thermal phenomena during microwave heating of ceramics and dielectric/biological materials. The model development is based on the edge finite element formulation for electromagnetic fields and the node fmite element formulation for thermal phenomena. Results are presented and compared well with available analytical solutions and experimental measurements. With the model, the effect of sample positions on the electromagnetic and thermal field distributions is studied.IntroductionMicrowave, as an electro-heating source, has been widely used in the processing industries for packaged foods and other materials. The commonly used household microwave oven is a typical example of microwave heating processes. Other industrial microwave processing systems include large-scale microwave guides and cavities, which are used for the sintering operations as required for making ceramic components or for sterilizing the packaged foods."

Jan 1, 2004

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

By Bo Zhou

During secondary aluminum recovery, complex aluminum scraps are melted and refined often in a rotary melting furnace and the aluminum metal has to pass through a molten salt layer and melt down in a bottom aluminum bath. Previous experimental study and industrial observations have indicated that salt shell formation and re-melting on the metal solids in the early stage plays a critical role in the overall melting process of the scrap. In the present paper, mathematical models are developed to simulate the process of salt shell formation and its re melting, as well as aluminum melting in the molten melt. Influence of the salt layer properties, the residence time of the metal particles in the salt layer, the particle size, the temperature of bulk melt were investigated. Reasonable agreement with the measurement data was reached. The developed melting model will be used to construct a population balance model of the scrap melting behavior for a rotary melting furnace, taking into account the distributed characteristics of the scrap. Finally, an overall process model based on Computational Fluid Dynamics (CFD) for the rotary furnace will be constructed, coupling with the population balance model for the scrap melting.

Jan 1, 2003

By T. Watanabe, T. Fujiwara, S-Wan Song, Y. Nakagawa, R. Teranishi, M. Yoshimura

"We have tried a new method to fabricate cobalt oxide films onto porous films directly by an electrodeposition method at low temperature. The porous substrate films (membrane-filters and paper) were placed between a LiOH solution and a CoSO4 solution and treated under electricalcurrents of ~1 mA/cm2 using carbon cathode and anode. Effects of temperatures, flow rates and electrical currents have been investigated. As a result, we found that the LiCoO2 films and Co3O4 films were successfully fabricated on paper and/or porous PTFE filters at 120 °C, while CoOOH films were deposited at 80 °C. Furthermore, LiCoO2 films did not cover whole the substrates, but was fabricated just over the anode. The chemical reactions of electrodeposition were also considered from these results.IntroductionRecent agreements on global environment require rapid progress of low energy and low waste processings for the fabrication of thin films that succeed to the mass production with the high consumption of the fossil fuels (such as physical vapor deposition°, chemical vapor deposition2), dip coating with firing3) etc.). The total energy consumption in aqueous systems should be the lowest among all these processing routes, because a much lager excess of energy is necessary to create melts, vapor, gas, or plasma than to form an aqueous solution at the same temperature4)The ""Soft Solution-Process"" (SSP) was one of the best concepts to realize the low energy and low waste fabrication of inorganic materials. 5) Generally speaking, SSP gives similar results to any other processing using fluids (such as vapor, gas plasma) and/or beam/vacuum processing. However, the total energy consumption of all these possessing routes should be the lowest in aqueous systems, because a much larger excess of energy is necessary to create melts, vapor, gas or plasma than to form an aqueous solution at the same temperature (Fig. 1). This idea can be easily demonstrated, using the simple example of BaTiO3. The energy diagram for the formation of BaTiO3 from various precursors is shown in reference 4. The driving forces (AG) for representative synthesis reaction of (1), (2), (3), (4) and(5) are 38, 727, 3685, 17 and —14kcal/mol, respectively at room temperature. 6' 7"

Jan 1, 2000

By Guanghui Li

Nickel pig iron (NPI), used as a substitute for electrolytic nickel, is able to reduce the production cost of stainless steel greatly. Aiming for preparing NPI from nickeliferous laterite ore, a pilot-plant scale test of coal-based rotary kiln direct reduction of laterite ore was performed and reported in this study. In this process, the ground laterite sample (18.85% TFe and 1.52% Ni) mixed with additives, pulverized coal and binder was briquetted into briquettes with the size of 40mm×40mm×31mm, laterite ore briquettes and reducing coal were charged into a rotary kiln with the diameter of 1.6 m and the length of 16 m, for a retention period of 6~7 hours, in which reduction section temperature was ranging from 950~1050 oC. The reduced briquettes were water quenched, ball mill ground and beneficated via low intensity magnetic separation. A magnetic concentrate, Ferronickel powder, with 86.9% TFe and 8.0% Ni was obtained, and the corresponding magnetic recovery of iron and nickel are 75% and 96.3%, respectively.

Jan 1, 2014

By Claudia Gasparrini

Uranium occurs in a variety of minerals, the more common primary ones of which are uraninite-pitchblende, coffinite and a group known as the complex multiple oxides. Identification and description of the uranium-bearing and associated minerals in ore samples may give a preliminary indication of the potential economic importance of the deposit and may also suggest initial approaches to metal extraction. The present paper reviews the common uranium minerals, describes their manner of occurrence and compares the types of deposits with which they are associated. Methods and techniques for their identification are described and their leaching characteristics discussed.

Jan 1, 1981

By Xiaoyan Xiang, Wenqiang Yang, Wentang Xia

Magnesium aluminate spinel is widely used in the metallurgical industry as refractory material, however, natural magnesium aluminate spinel is rare and most of the magnesium aluminate spinel is synthetic. The traditional synthesis of magnesium aluminate spinel often needs high temperature, which leads to more energyconsumption. In this article, solid phase sintering process was employed to synthesize magnesium aluminate spinel, in which, magnesium and aluminum oxide were used as raw materials and magnesium and aluminum powder were used as composite additives. The mass ratio of magnesium and aluminum on the effect of synthesis of magnesium aluminate spinel and the characteristic of the synthesis at different temperature and time was discussed. Experiment found that the synthesis temperature was observably lowered when the addition of magnesium and aluminum was 2.0% and 1.0% respectively.

Jan 1, 2016

By José Brant, Douglas Torres, Rogério Navarro, Rodrigo Souza, Eduardo Brocchi

The steelmaking process requires the input of ferro-alloys to implement the adjustment of some elements composition in the final product. In the particular case of stainless steel production, the high carbon FeCr alloy stands out as one important precursor. However in the production of this material a certain quantity of fine powder with remarkable chromium and carbon content is also generated, which, in turn, could be processed through alkaline roasting in order to selectively recovery this element in a subsequent aqueous route. In the present work, this process is investigated, using excess of NaOH as oxidizing agent, and H2O2 for precipitating chromium as Cr(OH)3, which is next calcinated to Cr2O3. According to the results, the global achieved recovery has shown to be around 98%, suggesting that the proposed route can be seen as a potential process for chromium oxide production from the mentioned fine powder.

Jan 1, 2015