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By Hongmin Zhu, Suning Liu, Kai Huang

"Recovery of silicon particles from the cutting slurry for the manufacturing of solar grade silicon is very important to recycle this kind of special resource. The challenge is to separate the silicon particles from the mixed abrasive particles which contain SiC. Various methods such as sedimentation, centrifugation, and flotation have been conducted, while in present work, a simple and effective novel method was proposed to study the separation of Si and coexisting SiC particles in the cutting slurry. The new process is based on the size difference between the two kinds of microparticles. And the membranes with the different pore sizes of 1µm, 2µm, 3µm and 5µm were used to test the pass ratio and separation efficiency of the suspension. Results shows that the effective separation of Si and SiC microparticles was obtained under the optimal conditions, and indicating great potential of practical enrichment of Si from the coexisting abrasive particles.IntroductionWith the development of the world economy, energy shortage and environment problem is becoming more and more seriously. Solar energy, which is regarded as one of the most important new energy in the word, has received much attention and interest from the scientists [1, 2]. More than 80% solar cells are manufactured by the high purity polysilicon as the raw material. The main process of producing silicon wafer is by multi-wire slicing. In this slice processing, large amount of slurry is produced. The slurry contains more than 30% wt silicon powder, silicon carbide powder as the abrasive, scraps of metal chips, as well as cutting abrasive suspension polyethylene glycol (PEG). The high-purified silicon powders are worth recycling and reusing as the materials for preparing solar-grade silicon though it is a big challenge [3].Most of the current studies were focusing on the recycling of the silicon carbide and PEG, while work on the recycling of the high-purified silicon is not so been focused since there is lacking of very effective separation and recovery technologies till up now. Nishijima utilized the method of superconducting magnetic to recycle the abrasive [4]. Wang applied a combinational process of chemical treatment, high-gravity centrifugation, high-temperature precipitation technique and directional solidification to enrich the silicon [5]. And other purification methods, such as centrifugation [6], froth flotation technologies [7], electrical filed separation [8] and phase-transfer process [9] have been employed. The disadvantages such as using poisonous media or complex equipments decrease the feasibility and efficiency of the above mentioned techniques."

Jan 1, 2014

By Alan J. Hurd

"New insights into the development of microstructure in sol-gel films have recently been revealed by several diagnostic techniques, including imaging ellipsometry, ""chemical imaging"" by fluorescent tracers, light scattering from capillary waves, and finite-element modeling. The evolution of porosity during the continuous transition from dilute sol to porous solid in restricted geometries such as films and fibers is becoming clearer through fundamental understanding of evaporation dynamics and capillarity.IntroductionWith sol-gel processing, the full flexibility of solution chemistry can be exploited to make ceramic films and fibers with well controlled compositional characteristics. No less important is the ability to tune porosity and connectivity for specific applications such as optical and electrical coatings and membranes. Since the chemical and physical factors that determine the microstructure are not entirely understood, new diagnostics applied to sol-gel processing are welcome.Sol-gel films and fibers are distinguished by processing that takes a sol through continuous stages of increasing concentration and connectivity of a solid precursor. The liquid carrier is usually volatile or, at least, volatilizable through heat treatment. During deposition through states of increasing solids concentration, this sol might gel, as in bulk sol-gel processing, however, the gel state may be a fleeting transient that quickly empties of liquid. Nevertheless, the structures formed in solution during this stage influence the structure of the final solid. In particular, porosity is likely to be a remnant of networks formed in the sol-to-gel transition. Here we report on experiments whose goal is to discover the factors involved with porosity development."

Jan 1, 1994

By Felipe P. D. Lopes, Ailton Silva Ferreira, Sergio N. Monteiro

"Environmental issues such as global warming and water pollution are motivating fast changes in scientific and technological paradigms. Special importance is now being given to the so called environmentally friendly materials, which are renewable, recyclable and biodegradable. An example is the natural fibers with increasing industrial applications beyond the conventional uses as baskets, fabrics, ropes and carpets. In addition to traditional natural fibers, others like curaua (Ananas erectifolius) are being investigated for possible use as reinforcement of industrial composites. Since epoxy matrix is not yet incorporated with curaua fibers, the objective of this paper was to study the basic properties of epoxy composites reinforced with different amounts of curaua waste fibers. A comparative analysis aiming at the use of these composites as substitute for conventional building materials was carried out.IntroductionThis new millennium, which initiates with the 21th century, is experiencing a fast degradation of the environment by pollution and climate changes. Most of the problems are related to our methods of development associated with the use of fossil fuels and the energy intensive processing and production of synthetic materials. As a consequence, environmental issues such as global warming and ocean pollution are motivating rapid changes in technological paradigms. One relevant example is the current importance given to natural materials like the lignocellulosic fibers extracted from cultivated plants or found as industrial wastes [1]. These fibers are considered environmentally correct alternatives to substitute energy intensive conventional synthetic fibers such as carbon, glass, nylon and aramid. In addition to the renewable recyclable and biodegradable nature of the lignocellulosic fibers, the low cost and abundance in developing regions are major advantages that justify their increasing application as reinforcement of composites [2,3].In fact, nowadays, the use of natural fibers is no longer restricted to baskets, ropes, clothes and carpets. Industrial composites are introducing these fibers in large technological segments associated with car making, building construction and furniture [4,5]."

Jan 1, 2008

By Tao Zeng, Jianchao Li, Chang Jie, Jieyu Zhang, Jifang Xu, Kuochih Chou

"The densities of the selected quaternary Ca0-5%Mg0-Alz03-Si02 slag with low silica were measured by the Archimedean method in a wide temperature range from l 723K to 1823K. Slag compositions were chosen based on five different levels of Si02 content between 0.00 pct and 11.40 pct. The MgO content was equaled to 5.00 pct. The mass ratio of CaO/Alz03 was varied from 0.67 to 2.14. The effects of temperature, Ca0/Alz03 ratio and optical basicity were studied. It is shown that density decrease approximately linearly with an increase in temperature. With the same Si02 content, the density decreases with increasing of CaO/Alz03 ratio and optical basicity. Based on the experimental data as the boundary of the homogenous phase region predicated by F ACTSAGE software, the mass triangle model is used to calculate the density of selected limited homogenous phase region. The results showed that the mass triangle model is working well.IntroductionIt is of great importance to measure density of slag melt not only to the theory research for melt, which that is directly amenable to the structure correlations of molten slags, but also to the industrial application. Many metallurgy phenomena such as inclusion formation in molten melt and its removing, slag foaming, slag-metal reaction are closely related to the density of slag. Density is also required to estimate other fundamental properties, like surface tension, viscosity, and thermal conductivity from thermal diffusivity so that a relatively complete picture in regard to the behavior of high-temperature molten oxides could be made."

Jan 1, 2013

By Guozhu Ye, Mikael Larsson, Eric Burström, Sten Ångström

"Increased use of scrap in steelmaking including scrap use in BOF has a high economic and environmental potential in terms of increased productivity, energy saving and reduced emission of CO2. Preheating and surface cleaning of steel scrap is a concept developed by MEFOS in a four year research program funded by MISTRA, Swedish Foundation of Strategic Environmental Research. The process concept consists of four major steps: 1) Combustion of ASR or other waste fuel and composing of the gas composition. 2) Scrap heating and cleaning in a shaft where the coated zinc is removed as ZnCl2 and scrap is heated to about 600 ºC. 3) Dust separation for recovery of metal zinc. 4) Gas cleaning. This paper will describe the process concept and highlight the major results from preliminary trials around the scrap heating and cleaning shaft.IntroductionSteel is often coated to increase the corrosion resistance. Share of coated and galvanized steel in the world marked is steadily increasing. This results in increased amounts of scrap with different types of coatings. Use of galvanized scrap in EAF plant results in an EAF dust with high content of zinc ferrite and many other impurities like Pb, Hg, Cd and halide. EAF dust is classified as hazardous waste in most of the developed countries and the steel plant has to pay for external treatment for zinc recovery. For use in BOF plant this will result in a BOF dust containing typically 1-5%Zn making it impossible for recycling to the blast furnace.Different approaches for surface cleaning have been investigated in past. Dapper et al. [1] examined the possibility to evaporate Zn, Ni, Cr, Sn from coated materials using chlorine. Chlorinated rinsing of non iron oxides and metals using HCl from combustion of PVC was discussed by Fray [2]. Further studies by Tee and Fray [3-5] have been concentrated on the possibility to vaporize coatings with an air and chlorine gas mixture. The O2:Cl2 ratio in the gas mixture was found to have great importance for control of the process. To avoid the chlorination of iron, this ratio should be kept at a level of 10:1.Scrap pre-heating up to about 600 ºC is a well known method and this alone could save up to 100 kWh per ton steel. The technology has been established since many years and efficient processes were developed in the 90’s. However, no process has fully gained the expected energy savings as the large quantity of the exhaust gas has to be reheated to over 1000 ºC again to destroy the hazardous components like dioxins."

Jan 1, 2008

By R. Boom, Y. V. Meteleva-Fischer, B. Kraaijveld, H. Kuntzel

"Segregation of impurities during refining of metallurgical grade silicon (MG-Si) is an option to produce solar grade silicon (SG-Si). Directional solidification is a last step in production of SG-Si effective for removal of metallic impurities. The possibility is investigated to use metallic impurities originally present in MG-Si for removing boron and phosphorus. MG-Si has been treated using two methods: 1) alloying with calcium and 2) refining with Na2O-CaO-SiO2 slag, both by controlled cooling. The microstructure of silicon and the impurities distribution have been studied before and after the treatments. Using EPMA phosphorus and boron have been detected in 1-2 wt% concentration range in several intermetallic compounds in grain boundaries after both treatments. This observation points to a different possible mechanism of silicon refining from boron and phosphorus. Controlled cooling improves migration of phosphorus and boron to the silicide phases in grain boundaries, which can be removed by acid leaching treatment.2. IntroductionStandards for silicon solar cells and growing demand on “green” energy require economical and efficient route to the production of solar grade silicon. Refining of cheap metallurgical grade silicon is one of the promising options, where application of existing metallurgical approaches can result in cost-efficient production on industrial scale. Focus in refining is on impurities, which are most difficult to remove: B, P, Al, Ti, due to their large segregation coefficient in silicon and low vapour pressure [1]. Moreover, more environmentally friendly technology in comparison to the traditional Siemens process [2] will be in accordance with societal needs. Based on properties of common impurities in metallurgical grade silicon, alloying refining and slag refining are suggested as competitive techniques having potential effect on removal of impurities harmful for conversion of solar energy [3, 4]. Alloying with Ca followed by acid leaching was found to be effective for removal of Fe and Ti from silicon [5] and to enhance also removal of boron [6] and phosphorus [7, 8]. In the work of Inoue et al. [8] drastically increasing removal of phosphorus from silicon has been observed with an increase of Ca content and a thermodynamics-based explanation was provided. Since phosphorus has been found to condense in the secondary precipitate mainly composed of CaSi2, it can be removed together with iron and titanium by consecutive acid leaching treatment. Slag refining is one of the metallurgical methods proposed to be effective for refining of metallurgical grade silicon from boron [9, 10]. Slags with additions of the following oxides to silica have shown positive effect on removal of boron: CaO [11-13], Na2O [11,14]. Mechanism of slag refining from boron is based on oxidation of boron followed by its incorporation in the slag network [9,11]; the same mechanism is suggested for refining from phosphorus taking into account that oxides of boron and phosphorus are known as network-formers [15]."

Jan 1, 2012

By Hiroshi Maeta, Takao Kino, Hirota Osono, Kikuo Matsusaka, Azusa Shida

"Prior to refine an ultra-high purity material, it is necessary to estimate the surface cleanness of a base material. In this report, the cleaning method of a surface for refining of an ultra-high purity aluminum has been studied. Aluminum sample of 99.999% purity was p9lished mechanically and electrically and washed with various solvents. Surface composition and a depth profile near the surface were examined. Based on the experimental results, surface structure of an ultra-high purity aluminum was discussed.IntroductionRecently, studies on high purity metals have become of interest, and we have reported .various properties of an ultra- high purity aluminum1- 2)In order to purify a metal, it is necessary to clean a work area and to make vacuous as possible. So, we are studying the purification of aluminum by an ultra-high vacuum refining system and a zone refining system set up in a clean room with cleanliness class of 1000.Now, in order to avoid a mixing of impurities into the refining metal, a surface cleanness of a base metal is very important factor. The purity of the base aluminum used our work is 99.999%, but the surface state of the base aluminum is not clear. Aims in this work .are to investigate the surface state and to obtain the cleaning method of the base aluminum.Experimental procedureSamples used in this work were 99.9% (3N), 99.99%(4N) and 99.999% (SN) aluminum produced industrially and 99.9999% (6N) aluminum purified by us."

Jan 1, 2000

By Chen Zhang

Polycrystalline Ti-rich NiTi thin films have been deposited from a single NiTi target using a DC magnetron sputtering system. Free standing film was obtained by using a single crystal silicon substrate. Thickness ofthe thin films is controlled at around 12 pm. In this investigation, the effect of deposition temperature on the microstructure and transformation temperatures of the thin films is studied. Influence of post heat treatment temperatures on the properties of the thin films is also investigated. Transformation temperatures of the thin films are determined by differential scanning calorimetry (DSC). The surface microstructure of the thin films is studied using a scanning electron microscope (SEM), and the crystallinity is determined using x-ray diffractometry. It is found that the thin film deposited on a hot substrate is crystalline even when the substrate temperature is as low as 300°C, while the normal crystallization temperature for an amorphous thin film is around 500°C. The microstructure of the film deposited on a hot substrate shows a very fine grain size. The grain size increases with increasing substrate temperature during deposition. The effect of post deposition heat treatment on grain size is minimal.

Jan 1, 1999

The purpose of this study was to investigate the immobilization as a host for metallic pollutants (Cr, Cu, Pb, and Zn) by ettringite phase. Ettringite phase is produced through hydration reaction of calcium aluminate with gypsum. From the XRD patterns, it is known that the distance between spaces in 010 planes in ettringite crystal increase with an increase of ionic radius of heavy metal except Pb; no big difference is shown. For this reason, the d-value of 010 planes in ettringite crystal increased with the substitution of Cr, Cu and Zn having a big Al ironic radius. But in case of Pb, because the substitution occurred at calcium site, it does not influence to increase d-value of 010 planes.

Jan 1, 2006

By Yan Fu, Chuanlin Fan, Xiujing Zhai, Yongfeng Chang, Binchuan Li

"The mechanism of the selective chlorination of nickel and cobalt in reduced limonitic laterite was investigated. Reduced ores were obtained from the reduction roasting of a limonitic nickel laterite. The thermal decomposition of related chlorides and the selective chlorination of the reduced ore were carefully studied using Differential Thermal analysis - Thermogravimetry (DTA-TG), X-Ray Diffraction and chemical leaching methods. In the temperature range of 300 - 500 °C, aluminum chloride hexahydrate was chosen as chloride agent. During the selective chlorination, reduced ore was partly chlorinated by hydrogen chloride generated from the thermal decomposition of chloride agent. Then the oxydrolysis of ferrous chloride re-generated hydrogen chloride was used to further the chlorination. Finally, iron was mostly rejected as hematite, while nickel and cobalt were selectively chlorinated. More than 91 %Ni , 90%Co and about 4%Fe in the chlorinated ore was extracted using a water leaching method.IntroductionLimonitic nickel laterite is an important nickel reserve, which is rich in iron in the form of goethite and has low contents of magnesium, aluminum, silicon, and other elements. Goethite is the main nickel-bearing mineral in the laterite [1]. Nickel is generally present in goethite in three modes: (a) associated with amorphous or poorly crystalline goethite, (b) weakly adsorbed to the crystalline goethite surface, and ( c) as lattice substituents [2]. In addition, cobalt in limonite was found to be associated with a manganese phase rich also in nickel [3]. These results indicate that the extractions of nickel and cobalt are highly dependent upon the degree of the decomposition of the nickel, cobalt-bearing minerals.For the selective extraction of nickel and cobalt from limonitic laterite, the ore is usually processed by hydrometallurgical methods, including high pressure acid leaching (HPAL) [4] or reductive roasting - ammonia leaching (Caron process). However, there are still some disadvantages in these processes, such as the expense of autoclaves and scaling problems in HP AL [ 4, 5], and relatively low overall metal recovery, large energy and reagent requirements for the Caron process."

Jan 1, 2011

By Mao Chen, Baojun Zhao, Zhixiang Cui, Leonel Contreras

Viscosity is one of the important physiochemical properties of metallurgical slags which is important for slag tapping, metal loss in slag, freeze lining and fluid dynamics. High temperature viscosity measurements are time- and cost-consuming and the number of experiments is limited. Viscosity model is an effective way to predict the viscosities of the complex slags at high temperature. However, a reliable viscosity model can only be developed on the base of accurate experimental data. A unique high-temperature viscosity measurement apparatus developed at The University of Queensland enabled accurate viscosity data to be measured for the “FeO”-SiO2-CaO-MgO-Al2O3 system in equilibrium with Fe. An accurate viscosity model has been developed based on Eyring’s theory and extensive viscosity measurements. The viscosities of copper smelting, converting and cleaning slags over a wide range of compositions and temperatures can be predicted and applied in the process control.

Jan 1, 2016

By Aly M. Abdel-Rehim

The present work deals with a study of the mechanical activation of processing of Egyptian monazite by its simultaneous ball-milling and pressure leaching in order to improve the recovery of thorium and lanthanides from monazite. Experiments of simultaneous ball-milling and alkaline leaching of monazite contrary to autoclave leaching were carried out in stainless steel ball-mills of cylindrical shape under different conditions of temperature, pressure, time and alkali amount and strength. The ball-mills were heated and mechanically rotated in an electric furnace by means of roll mechanism. The effective rotation speed was fixed at 130 rpm in all tests. The charge of steel balls of different diameters was equivalent to 45% of the total mill volume. Monazite was charged in ball-mill without preliminary grinding. It is found that high rate of monazite leaching by ball-milling leaching method is achieved at lower temperature, shorter time and lower expense of alkali than in autoclaves. The results obtained show that complete recovery of thorium and lanthanides from monazite (99.8%) by simultaneous ball milling and alkaline leaching is attained at 140°C within 2 h. It is concluded that processing of monazite by its simultaneous ball-milling and leaching is mechanically activated and accelerated as a result of grinding action of steel balls that caused the continuous removal of the hydroxide product from reacting particle surfaces. This leads to the exposing of fresh and activated monazite particles surfaces to alkali leach solution and consequently the acceleration of the reaction of monazite processing.

Jan 1, 2006

By I. A. Ibrahim

Ilmenite, in its natural form, is an inactive mineral from which the selective removal of iron is rather difficult. The reactivity of ilmenite. so that it can be leached with dilute hydrochloric acid, can be enhanced by chemical reduction in solution using a suitable metal as a reducing agent. The present paper aims at the evaluation of an Egyptian ilmenite ore for the production of synthetic rutile by direct leaching with hydrochloric acid in presence of iron powder. In this process, the titanium and iron contents are dissolved; meanwhile, the dissolved titanium is hydrolyzed and re-precipitated leaving mainly iron in solution. Leaching conditions were optimized to obtain less iron in the final solid product. Addition of sufficient amount of iron powder during leaching reduces the dissolved Fe3+ to Fe2+ and reduces the dissolved Ti4+ to Ti3+. The creation of Ti3+ in solution is assumed to have a role in dissolving the ferric iron and hence increasing the reactivity of the ilmenite ore. Synthetic rutile of about 90% TiO2 and 0.77% Fe2O3 was obtained from ore with a grain size 100% passing 200 mesh and a 5-hour leach time with 20% HCl at boiling temperature (110°C) and 0.11 g iron powder / g ore.

Jan 1, 2003

By Nagahiro Saito, Takashi Nishimura, Takamichi Ichikawa, Akio Fuwa

"Yttria-stabilized zircohia (YSZ) has high potential to be used as solid-oxide fuel cell (SOFC) electrolyte. However, the high efficiency of SOFC has not been yet achieved due to the high internal resistance of bulk electrolyte. The resistance becomes lower with the decrease in the electrolyte thickness. Thus, the decrease in electrolyte thickness leads to lower internal resistance. . The aim of this study is as follows: (a) to prepare the thin films of YSZ by inductively-coupled RF plasma-enhanced metal organic chemical vapor deposition (PEMOCVD) process using Zr(t-OC4H9)4,Y(DPMh and oxygeil, and (b) to reveal the relationship between the structural characterizations and the process parameters.1. IntroductionYttia-stabilized zirconia (YSZ) has, been widely used as not only heat-resistant materials but also the components in automotive oxygen sensors, electrolytes of solid-oxide fuel cell (SOFC)(1)(2) and the buffer layers for the high-temperature superconductor because of its low thermal conductivity, good mechanical properties and high ionic conductivity. However, it is said that the internal resistance of the bulk electrolyte is too high to be appropriate as a solid electrolyte for high-efficient SOFC. The authors believe that the thin YSZ electrolyte can give a high performance to characteristics SOFC, since the internal resistance becomes lower with the decrease of electrolyte thickness. Thus the process technology to prepare YSZ thin films is desirable and must be established.In recent years, the YSZ thin films have been reported by chemical vapor deposition (CVD), thermal CVD using metal chlorides (MC) of ZrCl4 and YC(3)(4), thermal CVD using metal organic compounds (MO)(5)(10) Zr(t-OC4H9)4 and Y(C11H19O2)(11) and plasma-enhanced (PE) CVD using MO. Here, these methods are called MCCVD, MOCVD and PEMOCVD. MCCVD has two disadvantages; a large quantity of chlorinated impurities in deposited films and high processing temperature (> 1273K). This high processing temperature leads to damage of substrates in particular, so the application of this technology is limited. On the other hands, the processing temperature by MOCVD becomes and is lower. Unfortunately, the accurate vapor pressures of these metal organic compounds have not been, known so: that it is difficult to control the composition and the film thickness by MOCVD method well. Moreover, the large amount of carbonic compounds in the films prepared by MOCVD method is produced. However, plasma-effect has been reported to decrease large amount of the carbonic impurities by PEMOCVD. However, PEMOCVD has many reaction parameters in plasma processing; the geometry of experimental apparatus, radio frequency, electronic power input and so on. Thus, the general understanding about the relationship among reaction parameters, the composition and crystal structure of thin deposit film by this method has not yet been established."

Jan 1, 2000

By Michal Rzyman, Nakamura Takashi, Shibata Etsuro, Grabda Mariusz, Oleszek-Kudlak Sylwia

"Thermodynamic considerations indicate that heavy metal oxides should easily react with HBr, the main gaseous product from the thermal decomposition of tetrabromobisphenol A (TBBPA), forming low boiling point metallic bromides suitable for volatile separation. Mechanisms and kinetics of the bromination reactions must be well recognized prior to developing of a new treatment for the simultaneous recycling of plastic waste containing brominated flame retardants (BFRs) and metal oxides (printed circuit boards, automotive shredder residue, plating sludge, metallurgical dusts). In this work, a differential scanning calorimeter and laboratory-scale furnace were used to investigate the possibility and conditions of the bromination of ZnO by product of thermal decomposition of TBBPA. The formed solid, condensed and gaseous products were analyzed by X-ray diffraction analysis, electron probe microanalysis, inductively coupled plasma analysis, ion chromatography and gas chromatography coupled with mass spectrometry. Introduction Tetrabromobisphenol A (TBBPA) is the largest volume brominated flame retardant (BFR) in production today and is used in more than 70% of the world’s electronic and electric (E&E) appliances [1]. The growth in the production of E&E products and the fact they become obsolete so quickly cause significant problems in the safe disposal and recycling of the electrical and electric waste (E-waste) and other BFR-containing waste [2]. Among various treatment processes, thermal methods are most useful since they allow the recycling and recovery of both the organic and inorganic fractions of the waste. However, incineration of the BFR-containing wastes results in the emission of hazardous organobromine compounds, while the main portion of bromine released from decomposed BFRs is present in flue gas as hydrogen bromide (HBr) [3]. HBr, which is known to damage incineration systems, seems to be a very effective bromination agent for many metallic oxides present in waste. The concept of this study is to take advantage this of its property."

Jan 1, 2008

By Wagner Aldeia, Duclerc Fernandes Parra, Danae Lopes Francisco, Ademar B. Lugão, Lucilene Betega de Paiva

The inorganic nanotube halloysite (HNT) is a promising type of natural occurring filler for polymers. Its characteristics, such as high aspect ratio (10–50), small size, and high strength (elasticmodulus—140GPa) suggest that HNT shave a potential use in high-performance polymer nanocomposites. Compared to other nanoclays and nanosilica the relatively low content of hydroxyl groups on their surfaces makes HNTs relatively hydrophobic, although, sometimes, this is not sufficient for guaranty a good interfacial adhesion in composite systems. Further hydrophobic treatment is required to improve HNTs compatibility with polymer matrixes, maximizing interfacial interactions. In the present study, different percentages of EPB (2,2-(1,2-ethene diyldi-4,1-phenylene) bisbenzoxazole) was used to perform anon-covalent functionalization of halloysite, based on electron transfer interactions. The functionalization is characterized by specific surface area (BET), thermogravimetric analysis (TG) and water/toluene extraction experiment.

Mar 1, 2018

By Stein Tore Johansen

Some ferro-silicon furnaces have heat-recovery equipment. Here, the recovery of electric energy from the off-gases can be increased by increasing the off-gas temperature. This is easily done by reducing the amount of air which usually is mixed into the?off?gas to cool the gas mixture. If the off-gas becomes too hot problems with severe fouling or clogging of the gas channels close to the furnace is observed. The result is irregular stops to clean the off-gas channels. The paper focuses on the nature of the clogging phenomena and some of the ways to avoid clogging. A detailed experimental study was carried out at the Elkem Thamshavn Plant. Theoretical studies were performed to understand the particle deposition, turbulent multiphase fluid flow and off gas combustion in the off-gas channels. The study has resulted in reduced clogging.

Jan 1, 1992

By Stein Tore Johansen

Some ferro-silicon fumaces have heat-recovery equipment. Here, the recovery of electric energy from the off-gases can be increased by increasing the off-gas temperature. This is easily done by reducing the amount of air which usually is mixed into the off-gas to cool the gas mixture. If the off-gas becomes too hot problems with severe fouling or clogging of the gas channels? close to the fumace is observed~ The result is irregular stops to clean the off-gas channels. The paper focuses on the nature? of the clogging phenomena and some of the ways to avoid clogging. A detailed experimental study was carried out at the Elkem Thamshavn Plant. Theoretical studies were performed to understand the particle deposition, turbulent multiphase fluid flow and off gas combustion in the off-gas channels. The study has resulted in reduced clogging.

Jan 1, 1992

By Bradford C. Wesstrom, Omar Araujo

"Impurities from an electrolytic refinery are typically extracted from the electrolyte utilizing conventional electrowinning cells. These cells are arranged in series with cascading solution flow and are commonly referred to as liberator cells. The Freeport McMoRan Copper & Gold El Paso Refinery has optimized the removal of arsenic in cascading liberator cells by utilizing two separate feed solutions. The primary feed solution is recycled liberator electrolyte and the secondary feed solution is ""neat"" tank house electrolyte. The secondary feed solution is added based on the voltage response across the individual cells utilizing independent variable frequency drive (VFD) pumps. When the voltage across a cell changes, a signal is sent to the VFD pump to maintain a cell voltage of 1.98 volts. By maintaining this voltage the copper content in each cell exits at 2-4 grams per liter. This safely optimizes the arsenic removal as copper arsenides on the liberator cathodes.IntroductionDuring the electrolytic refining of copper, impurities from the copper anode report both to the bottom of the electrolytic refining cell as slimes and to the electrolyte. The impurities which enter the electrolyte are arsenic, antimony, bismuth and nickel. The impurities that report to the electrolyte during the electrolysis process gradually increase. As these impurities increase, they are incorporated into the refined copper cathode. There are many processes that have been used to remove these impurities from refinery electrolytes. Some of them are listed as follows: solvent extraction, ion exchange, hydrogen sulfide reduction, bioreactor, adsorption onto a low - solubility metal-oxide hydrate, adsorption onto activated carbon and EMEW cells. The conventional process used by the copper refining industry for controlling the level of impurities in electrolyte involves multistage electrolytic cascading liberator cells. In these cascading liberator cells copper, arsenic, antimony and bismuth are removed as various mixed deposits from the electrolyte. Removal of these impurities is achieved through an increase in voltage resulting from the depletion of copper in the electrolyte through electrowinning. With this higher voltage, the Group Vb elements, arsenic, antimony and bismuth are deposited on the copper cathode and report as slimes to the bottom of the cells. Nickel is removed in a subsequent process."

Jan 1, 2012

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