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By Xia Hong-ying, Peng Jin-hui, Zheng Zhao-qiang, Zhang Li-bo

"Preparation of activated carbon from the walnut shell by microwave assisted steam activation was studied. Influences of the three parameters, activation temperature, activation duration and steam flow rate on the adsorption capacity and yield of walnut shell activated carbon(WSAC) were investigated,optimization process was obtained by the Response Surface Methodology (RSM). The optimum preparation conditions were as follows: activation temperature of 980°C, activation duration of 41 min and steam flow rate of 1.66 ml/min. The optimum conditions resulted in an activation carbon with an iodine number of 1025 mg/g and a yield of 52.17%, while the BET surface area, total pore volume and average pore diameter of WSAC were 1328m2/g, 0.72ml/g and 2.2nm respectively. The study supported the potentiality of comprehensive utilization ofWalnut shell and the benefits of the microwave heating.IntroductionActivated carbons are one of the most important adsorbent materials in modern society because of its abundantly developed pore structure, strong adsorption ability, high surface area and thermo stability. They have extensive application in many industries fields which include gas purification [1], catalyst supports [2] and other pollutants [3]. However, in recent years, the industrial production of activated carbon is facing the problem of raw material scarcity and high cost, which limit to be widely used. Therefore, the selection of an appropriate precursor plays an important role and it has become hot sport to seek cheap raw material to lower preparation cost. As a kind of reproducible resource, the waste from agriculture and forestry is a high-grade raw material for preparing activated carbon due to is high carbon content, such as palm shell [4], rice hull [5], and coconut shell [6]. At present Walnut shell is widely accepted to be a renewable source of biomass. According to statistics, there is more than 1000,000 tonnes of walnut shells are produced in China annually [7]. As a good precursor for activated carbon production, Walnut shell is a major agricultural waste, to make better use of the cheap and abundant agricultural waste, it is proposed for activated carbon production."

Jan 1, 2014

By Lv Guozhi, Niu Liping, Liu Yan, Zhang Zhiqi, He Jicheng, Zhang Ting’an, Dou Zhihe

"CuCr alloy can be extensively used as contact materials in integrated circuit, electrodes, electric contact and high strength conductor. We proposed thermit reduction-electroslag remelting method of preparing the large scale CuCr alloy. But there are pores and oxide inclusions in CuCr alloy prepared by thermit reduction process. This paper studied mainly the effects of ratio of reactant and additive on the inclusion type and their occurrences in CuCr alloy. The slags and CuCr alloy were characterized respectively by XRD and SEM. The results show that when the additive is Na3AlF6, the slag consist of Al2O3 and Cr. When the additive is CaF2, the slag consist of Al2O3, Cr, CaF2 and CaAl4O7. The inclusions in CuCr alloy are mainly Al2O3 and pores which disperse in Cu-rich zone and Cu-Cr phase interface. When 5% CaF2 and 5% KClO3 are added, there are fewer pores and inclusions, and the more better microstructure.1 IntroduceCuCr alloy is the contact terminal material with an eximious properties[1,2], which gradually replaces CuBi alloy becoming the first choice for contact terminal material in the medium and high power vacuum switch after the 1970s. The traditional preparation methods of CuCr alloy mainly contain powder metallurgy, infiltration process and vacuum electric arc melting methods. But the above methods exist some shortcomings, such as poor product quality, high cost of production, processes complex ect[3-9]. CuCr alloy is made by the thermit reduction self-propagating method, which uses CuO, Cr2O3 and Al as raw material to get the high-temperature melt, and then casts to manufacture CuCr alloy ingot, which response equation follows as:"

Jan 1, 2012

By Qingchun Yu, Bin Yang, Yong Deng, Heng Xiong, Fei Wang, Minxiu Chen

"Metal aluminum produced by non-electrolysis process received much attention due to its lower energy consumption. In this paper, carbothermic reduction and carbothermic-chlorination of alumina in normal pressure and vacuum were studied. The products were examined by means of XRD, EDS and SEM. During the carbothermic reduction process using carbon reductant in normal pressure, no metal aluminum was found. However, when coal was used as reductant, a mixture containing metallic aluminum, A14C3, and silicon was obtained, but metallic aluminum couldn't be separated from the mixture. During the carbothermic-chlorination process in vacuum, Al404C and Al4C3 were produced by the reaction between alumina and carbon, and Al Ch gas reacted with Al404C and Al4C3 to produce Al Cl gas. Metallic aluminum was produced due to the disproportionation of A!Cl gas and condensed on the collecting plate. Meanwhile, the initial temperature of carbothermic reduction of alumina reduced in vacuum compared with that in normal pressure.IntroductionIndustrial production of primary aluminum is carried out in alumina cell by the so-called Hall- Heroult process, necessitating the use of very high currents of low voltage. The alumina from which metallic aluminum is gained must be chemically pure, otherwise impure metal results. The main drawbacks of the electrolytic production are its very high energy consumption, the release ofperfluorocarbons, and the high specific C02 emissions [1]. During the past years, there were a lot of attempts to produce metallic aluminum by carbothermic reduction of A1203 [2, 3]. Cox [4] determined the vapor pressure over the A1203-C system and performed X-ray diffraction analysis of condensed products. It was demonstrated that an increase in the carbon content in the system leaded to the sequence of transitions: A1203~Al404C~A1zoc~A14C3 ~AI [5]. In any carbothermic reduction process for aluminum, extremely high temperatures (2000 °C ) were required [6]. In spite of considerable effort, the carbothermic reduction of alumina to aluminum remains a formidable technical challenge, due to the high temperatures required, and to the formation of aluminum carbide and oxycarbide byproducts [7]."

Jan 1, 2013

By Fiseha Tesfaye, Pekka Taskinen, Daniel Lindberg

Due to increasing complexities of raw materials for base metals production the conventional pyrometallurgical processes are challenged. To make the appropriate modifications, thorough evaluations of the thermal stabilities of phases and phase assemblages which are commonly encountered in these processes are essential. In this work, phase relations and thermal stabilities of equilibrium phases in the Cu-Ni-S system have been reviewed. The calculated phase diagram of Cu-Ni system has been validated. At T < 630 K, in the Ni-rich corner, large scatter in data has been observed and discussed in detail. The other binary systems, Cu-S and Ni-S, have been also critically reviewed together with the ternary Cu-Ni-S system. The reviews were focused on compiling and discussing phase relations and thermal stabilities of the selected systems in the pyrometallurgical processes of Cu and Ni productions.

Jan 1, 2016

By A. V. Tarasov, V. M. Paretsky

"A mathematical model of the low-temperature (soft) nickel oxide reduction (SNOR) in a tubular kiln has been developed including an equation describing changes in the nickel oxide content of the solid material along the length of the kiln; an equation describing the changes in the content of reagents ensuring nickel reduction (i.e., hydrogen and carbon monoxide) in the gas phase along the kiln length; as well as the temperature along the kiln length. The kinetic relationships used for the development of the model had been determined based on experiments conducted specially for this purpose. Model investigations were conducted to determine the distribution of such parameters along the length of the kiln as the contents of metals oxides in the solids, partial pressure of hydrogen and carbon monoxide, variations of the temperature depending on the SNOR process conditions, including the kiln rotation speed. Based on the data obtained, a simplified regression model of the reducing roasting process was developed.IntroductionAt the SeveroNickel complex (Russia) a technology has been developed and is being introduced on a commercial scale for low-temperature (soft) nickel oxide reduction (SNOR) in tubular kilns.The SNOR process has a number of advantages, the main of which are the higher degree of metallization and higher chemical activity of reduced nickel oxide attributable to the lower fusion of the surface of the grains of reduced material due to lower process temperature (800-1000°C) and improved reducing ability of the gaseous phase. However, the fact that the process is conducted in a gaseous phase sets higher requirements to the consistency of its composition necessitating careful continuous monitoring and control of the main process parameters."

Jan 1, 2001

By Bingchen Chen, Zhitong Sui, Junwei Ma

"In the blast furnace slag, titanium disseminated in various mineral phases Titanium could be concentrated mainly in perovskite, which could be selectively precipitated and grown by optimizing the operation factors like the slag composition, temperature of heat treatment and additive agents. This study aims at establishing the titanium slag mineralogy and its distribution in the treated slag and the as-received slag, as well as the methods of perovskite separation. After heat treatment, the grain size was grown from 5 - 20µm to 80 - 200µm, the distribution of Ti02 in perovskite was increased from 48% to 81 %, the morphology was changed from snow-shaped grain to coarsening dendrites or equiaxed crystals. A concentrate were produced by gravity separation analyzing 35.25% Ti02 with a recovery of 68.28% and a tailing analyzing 9.53% Ti02 , and a possibility of flotation upgrading was discussed. I INTRODUCTION CHINA is rich in mineral resources of titanium, 92.4% of which is vanadium-titanium bearing magnetite. About 53% titanium were in iron concentrate after mineral processing, by which the blast furnace slag containing about 25% TiO2 were produced[11 • The content of TiO2 in such slag is too low to separate titanium dioxide, and it is also too high to produce slag cement[21. It has been accumulated to 50 million tons so far, which is still increasing at a rate of 3 million tons per year, and results in a waste of titanium resources and pollution of environment. Due to the dispersed distribution of titanium component in various mineral phases, very fine grain(<10µm) and complex interfacial combination, it is very difficult to recovery titanium component from the slag by traditional separating technique. In this paper, a novel technique to recovery titanium from the waste slags was proposed [3H4l, on which three continuous processes were involved: selective concentrating, selective growing and selective separating. Perovskite was designed as a titanium-rich phase, in which the most titanium was concentrated promptly, then perovskite could be selectively grown and coarsened by optimizing the heat treatment and the appropriate additives [ 5l[6l. The grain size of perovskite phase was larger than 80 µm, and the crystals appeared as coarsening dendrites or equiaxial grains like lump."

Jan 1, 2000

By Hiroyuki. Fukuyama

The pseudo-binary phase diagram of the cuspidine (3CaO2?SiO2?CaF2) - CaF2 system has been studied by electron probe microanalysis (EPMA) and X-ray diffractometry (XRD). To prevent fluorine loss in the form of a HF gas by a reaction of CaF2 with water vapor at elevated temperatures, the equilibrium experiments were conducted with the sample hermetically sealed in a platinum tube. By employing this technique, it was successfully revealed that cuspidine exists as a stable phase and congruently melts at 1684 ± 1 K, and the cuspidine - CaF2 system presents a simple eutectic type of phase diagram, of which eutectic temperature has been estimated to be around 1540 K, corresponding to the composition of 40 mass% 3CaO?2SiO2 - 60 mass% CaF2?

Jan 1, 1999

By Versiane A. Leão

The hydrochloric leaching of chrysotile tailings and soapstone powders) is discussed. This two materials are magnesium compounds associated with carbonates and iron oxides. In this work the chemical and physical characterization of formers is presented and the thermodynamic analyses of leaching is carried out. Magnesium extraction is almost complete for chrysotile tailings while, for soapstone powders, one can be reached 60%. The behavior of iron and calcium impurities is discussed.

Jan 1, 1997

By Zhijing Zhang

Long-term thermal stability of ionic liquids is essential for reliable performance of ionic liquids in any engineering applications. TGA studies were carried out on a series of ionic liquids with different cations and anions such as 1-butyl-3-methylimidazolium chloride ([C4mim]Cl), 1-hexyl-3-methylimidazolium chloride ([C6mim]Cl), 1-hexyl-3¬methylimidazolium tetrafluoborate ([C6mim]BF4), 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6mim]PF6), 1-octyl-3-methylimidazolium hexafluorophosphate ([Csmim]PF6), and 1-butyl-3-methylimidazolium bis(trifluromethanesulflonyl)imide ([C4mim][Tf2N]). The short-term thermal stability of ionic liquids was evaluated by measuring the onset temperature of decomposition of ionic liquids, and the long-term thermal stability of ionic liquids was also evaluated by weight loss of ionic liquids over a long period of time at various temperatures. The experimental results showed that the long-term thermal stability of ionic liquids decreased with increasing temperature and was significantly lower than the onset temperature of decomposition of ionic liquids.

Jan 1, 2002

By Masayasu Kawahara

"The extraction and separation of nickel, cobalt and copper were investigated with a solvent impregnated resin which was produced from UX84-I and XAD-4. The extraction behavior of metals with the solvent impregnated resin is similar to that with solvent extraction. The extraction ability of solvent impregnated resin improves when using finer particle resin and with a higher concentration of extraction solvent.IntroductionSolvent extraction is well known-as a method for separation of metallic elements in solution. However there are problems with intermediate phase and solvent loss. Ion exchange resin is also used in hydrometallurgy, but it is not fit for separating a large quantity of metals. Amberlite XAD-4 resin is known as a absorption agent of organic matter in water. It is expected that the resin which has the ability of extracting metals can be made by absorbing organic extractant on XAD-4 resin In this study, solvent impregnated resin (SIR) was produced from LIX84-I and XAD-4, and extraction and separation of nickel, cobalt and copper were conducted using SIR. The extraction properties of SIR were investigated, and a comparison between ordinary solvent extraction and SIR was made.Experimental ProcedureAmberlite XAD-4 was used as absorption resin for the organic extractant in this study. The physical properties of XAD-4 are shown in Table I. Amber lite XAD-4 has a large surface area and shows good ability to absorb organic matter in water, but the: resin does not have the ability of exchanging metallic ion."

Jan 1, 2000

By Nobuyuki Masuda

In Japan, the municipal solid waste, which amounts to 50 million tons, is generated every year and most of it is incinerated. The fly ash from the municipal waste incineration (the primary fly ash) contains heavy metals, such as lead and zinc, etc., and dioxins. In case of melting, the fly ash from the process (the secondary fly ash) contains high concentration of heavy metals (e.g., Zn; 1-20%, Pb, 1-10%). Metal Mining Agency of Japan launched a four-year project in 1999 to establish the integrated technologies to recover the valuable metals from, and to decontaminate, the primary and secondary fly-ashes in the practical scale by utilizing the existing metallurgical processes and facilities, along with the energy saving. The segregation, flotation and chemical treatment are applied to the treatment of the primary fly ash. The secondary fly ash is treated with MY (Mitsui-type blast furnace) Process after the chlorine removal to recover the heavy metals in the ash, In this paper, the segregation and flotation process for primary fly ash and MF process for secondary fly ash are explained. The main results of experiments done from 1999 to the mid of 2001 to design the pilot plants and to optimize the operating conditions are described. The main results of the experiments are as follows: - The segregation reaction of Cu was confirmed by the experiment on the treatment condition of 800 and 900`C with adding oil cokes and water to the primary fly ash, and 99.98% (toxicity equivalent) of the dioxins were decomposed by the treatment. - Washing tests of secondary fly ash to feed MF resulted that more than 70% of chloride were removed, but still lower than expected, and agglomeration tests were successful by the results of the sufficient strength of briquettes produced though a little more binder for the agglomeration is required than usual operation. - Smelting experiment by downsized MF showed that valuable metals, such as zinc and lead, are recoverable in the furnace dust. Recovery ratios, Zn: 58% and 67%, Pb: 74% and 83%, are accomplished.

Jan 1, 2002

By A. Valenzuela

During the last years, Chile has been the largest copper producer, either as concentrates or cathodes. Copper obtained via pyrometallurgy is produced by seven smelters, which have carried out modernization plans to increase smelting capacity or to achieve environmental regulations established in the Chilean legislation. Thus, the present work updates technological innovations in smelters, environmental regulations and presents solutions for SO2 handling, particulate matter and arsenic. Also, the authors emphasize the important role of CODELCO Chile, the most important state-owned copper company, in developing technologies such as EI Teniente Converter and EI Teniente Slag Cleaning Furnace,

Jan 1, 2003

By Edgar E. Vidal

The deposition of ceramic materials onto substrates is of special interest in the development of surface related technologies. Research interest has been placed on using thermal plasma as the deposition method, specifically inductively coupled plasmas. Many different modifications to the same basic principle of deposition have been performed through out the materials research community. Such a technique may have many advantages over more conventional techniques, such as high deposition rates, high surface area coverage, clean energy source, no contamination from electrodes and operation near atmospheric pressures. Materials deposited vary from simple oxide systems like TiO2 to more complex structures like ternary oxides and nitrides. This paper reviews recent developments relative to the inductively coupled plasma deposition of thin films.

Jan 1, 2003

By Hsi-keng Hu

"This paper deals with the flotability of stibnite and summarizes the major experiences and technological innovations of some typical practices of antimony sulfide ores in China. Experiences of cyanide-free and -less flotation of complex antimony sulfide ores and the application of the heavy media process to the preconcentration are described.Performance improvements obtained by innovations in operating techniques are also outlined and discussed. Technical innovations involve: (1) ramification roughing and differential-rate cleaning of stibnite-arsanopyrite ore; (2) the application of the new flotation reagent system; (3) process of separation flotation of Sb-Hg bulk concentrate; (4) extraction of gold from Au-Sb bulk concentrate; (5) flotation recovery of coarse stibnite particles.IntroductionChina is rich in natural resources of antimony and is one of the major antimony producers in the world. During the past several decades, a lot of research works have been done and many experiences in milling practices were gained, some of which are summarized briefly as follows.I. Heavy Media separation of Antimony sulfide Ore at Xikuangshan Hill, Hunan province (1)HMS as a technique of preconcentration of antimony ore has been performed more than ten years in China with good results.1. Ore characteristics The antimony ore of Xikuangshan belongs to the epithermal- metasomatic-filled doposit of antimony sulfide. Major minerals are stibnite (92.1%), antimony oxides (7.9%) and a small amount of pyrite and pyrrhotite; the gangue minerals are quartz, silicic limestone, calcite, hydrous kaolin, sericite, barite and others. The specific gravity of the ore is 2.8 and the specific gravity of stibnite and gangue are 4.6 and 2.654, respectively."

Jan 1, 1988

By KAGAN BENZESIK, Onuralp Yücel, Mehmet Bugdaycı, Ahmet Turan

ZrB2 and B4C are one of the most significant advanced ceramics. They are being used in various industrial areas from space technology to nuclear industry owing to their physical properties such as high melting point, high thermal/electrical conductivity and low density. Present study was conducted in two main stages: Self-propagating high-temperature synthesis (SHS) reactions and leaching. ZrO2, Carbon black, B2O3 were used as starting material to produce ZrB2-B4C powders by SHS. Also Mg powder was used as the reductant. The reaction mixtures (approximately 100 g) were mixed thoroughly 15 minutes in a turbula mixer and charged into Cu crucible and compacted. W (tungsten) wire was placed at the top of copper crucible and the reaction realized by passing current through the wire. After initiation, a highly exothermic reaction became in a self-sustaining mode and propagated throughout the SHS mixture. The samples were characterized by using AAS and X-Ray Diffraction.

Jan 1, 2016

By Guanyong Shi, Zhihe Dou, Cong Wang, Ting'an Zhang, Hongyan Zhang

We prepared the CuCr alloy by thermit reduction-electromagnetic casting. But there are the defects such as stomata and oxide inclusions in CuCr alloy. In this paper, the existing state and distribution of inclusions and stomata in CuCr alloy are systematically analyzed. The alloy was characterized via SEM, EDS and metallographic microscope, in which the existing state and micro-structural defects of inclusions are analyzed. The results show that: there are three distinct areas: copper-rich areas, chromium-rich areas and the inclusion areas. Inclusions are mainly in the form of stomata and Al2O3 phase, mainly locating in the copper-rich phase and the interface area of chromium-rich phase and the copper-rich phase. Then, the composition of phases of the smelting slags and alloy were characterized via XRD. The results show that: the slag consists of Al2O3 and a little of Cr, the alloy consists of Cr, Cu and a little of Al2O3.

Jan 1, 2015

By Sacha Neven

Submerged lance technologies combine high intensity processing characterized by rapid mixing and reaction rates using a simple reactor design. The Isasmelt technology uses a central submerged lance to inject oxygen-enriched air and fuel into a bath thus creating large gas bubbles and intensive turbulence and splash. The lance is equipped with swirlers to increase gas velocity and heat transfer. This enables the formation of a frozen slag layer on the lance which protects it from the aggressive environment. Water models as well as high temperature reactors were used to validate the Davidson-Schiiler model on bubbling. Frequencies and pressure amplitudes were measured in a wide range of gas flow rates: from m3/sec using a water model to more than 30 m3/sec in an industrial process. Agreement with the model was satisfactory. The experiments however also clearly showed that cross-flow and bubble wake induce slightly higher frequencies. No influence of the use of swirlers on the bubbling frequency was observed in the water models.

Jan 1, 2002

By Jin Yu, Fang-Qiu Zu, Yun Xi, Li-Na Mao

"According to the behaviors of resistivity-temperature of Cu-Sb70 melt, which suggests a partly reversible temperature-induced liquid structure transitions (LST) could occur in this alloy, in this paper, we investigated the dependence of solidification on the liquid state. Both resistivity and temperature were measured to track solidification process. The results show that the nucleating undercooling of the melt which experienced the LST increased and the solidified time decreased. Meanwhile, the solidified microstructures refined evidently, with the microscopic pattern of primary phase changes from disordered pillarlike dendrites into homotaxic ones. Moreover, it is verified that the microstructures would be different if the reversible part of the LST was restrained. The new phenomena and results reflected in this paper suggest that grasping the rules of melt structure change with temperature before material processing will give help for controlling the solidification more effectively and finally resulting in more ideal microstructures.IntroductionThe structure and quality of liquid alloys have a direct and important influence on the structure, performance and quality of the solidified ones. In recent years with in-depth study of liquid structure, researchers have found that some liquid structure transitions (LST) could occur on dependence of the temperature or pressure [1-5]. And the article [6] reported that a pressure-induced reversible LST was found in liquid triphenyl phosphite, which further confirmed the authenticity of the existence of the LST. Furthermore, in our earlier studies of Sn-based melts using resistivity method, some abnormal structure changes induced by temperature have been found at hundreds of degrees above liqiudus, and these LSTs are partly reversible[7]. This phenomenon has been discussed and it is suggested that the reversible LST in Sn-based melts are related to the short-range ordering (SRO) structures of Sn, which are tetrahedron structure with covalent bonding. However, does this reversible LST exist in other melts too?"

Jan 1, 2012

By M. A. Gerdel

In carboxylate collector flotation of bastnasite from other semisoluble salt type minerals such as barite various modifiers must be added in order to achieve selective flotation. One such modifier is a lignin sulfonate. It may function in part by acting as a sequestrant for metal ions present, preventing autoactivation in the system by metal ions derived from the minerals themselves. It also functions as a depressant for both bastnasite and barite, chemisorbing on both. However, it is shown that the lignin sulfonate functions as a much stronger depressant for barite than for bastnasite. It is suggested that the; strong depressing action on barite is related to a good fit of the sulfonate into the barite structure.

Jan 1, 1989

By J. Brent Hiskey

The global copper industry faces a technological challenge to develop processing schemes for more complex and impure ores and concentrates. Group 15 elements (As, Sb, and Bi) represent impurities that are troublesome both in terms of environmental impact and metallurgical processing. The so-call "dirty" copper concentrates are either unacceptable for smelting and refining or incur high penalties. The behavior of the Group 15 elements is of critical importance in maintaining product quality and process performance. During copper electrorefining, these impurities are released to the electrolyte by electrochemical dissolution of the anode. Depending mainly on temperature, concentration, and oxidation state these elements can spontaneously coprecipitate from the electrolyte. Some of these precipitates are referred to as floating slimes and their formation can have extremely detrimental effects on cathode purity. In this paper, the mechanism of floating slimes formation will be discussed and the fundamental thermochemistry will be reviewed and analyzed in relation to solubility properties.

Jan 1, 2012