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By Yongzhong Xiao, Tiejun Chun, Jian Pan, Deqing Zhu

"An innovative process of reverse floatation-direct reduction-low intensity magnetic separation was developed to effectively beneficiate the superfine run-of-mine (ROM) ore mined from Hunan Province, China. Mineralogy was measured that the ROM ore is of superfine low grade hematite ore type, assaying 27.2wt%Fetotal and with main valuable minerals of hematite occurring at size between 3 to 5µm. The upgrading results show that the final iron concentrate, assaying 88.3wt%Fe total and 94.5% metallization degree was obtained at an overall iron recovery of 69.9% under the following conditions: rough concentration by grinding of ROM up to 88.7% passing 0.074 mm and reverse flotation at pH=9.4, 100 g/t starch and 200 g/t dodecylamine (DDA), and coal reducing the rough concentrate pellets containing 12% calcium containing complex additive at 1200 oC for 120 min, and finally magnetic separation of the reduced pellets by grinding up to 89.2% passing 0.043 mm at 0.08 T field intensity.IntroductionWith the rapid development of iron and steel industry in China, there has been a soaring demand for iron ores in the past decade. The imports of iron ores have increased from 148 million ton in 2003 to 628 million ton in 2009 [1]. Iron making industries increasingly demand for high grade raw materials to improve product quality and reduce operation cost. However, availability of high grade natural ores is limited and enrichment of lower grade ores is necessary to meet the demand. Therefore, large quantities of superfine low grade iron resources are necessary to utilize in China at the moment."

Jan 1, 2011

By Joner Oliveira Alves

The aim of this work was to study the use of steelmaking slag as raw material to the production of rock wool and glass wool. Firstly, the chemical composition of the slag was analyzed. These results were used to infer the amount of additives to assemble the charge for the experiments. A laboratory-scale electric furnace was used to melt the mixtures used as charge. The melt material were turned into a water filled recipient, this process was performed in order to impose a fast freezing that is a characteristic of mineral wool production. Finally, with the rest of the melt material it was performed the Herty Viscosity Test. Samples of the produced material were characterized by different analyses. The results found in this research may lead to a technological innovation, because they indicate that the use of steelmaking slag to produce rock wool and glass wool is possible.

Jan 1, 2009

By C. Allen

A series of zinc chloride electrowinning tests was carried out in a laboratory scale cell to evaluate the effect of temperature, current density, electrolyte composition, gas sparging and additives on the performance of the cell with respect to current efficiency, voltage, specific energy consumption and deposit morphology. The anode material was DSA for chlorine evolution and the cathode was made of aluminum. At 400 A/m2 current density, a current efficiency of 90.9%, a voltage of 3.4 V and an energy consumption of 2.78 kWh/kg were observed. Air sparging was found beneficial but was not pursued for health and safety reasons. Various additives in the same chemical family as tetrabutyl ammonium chloride (TBAC1) were tested. Both TBAC1 and tetrabutyl ammonium bromide were found to be equally effective. Attempts to carry out the electrolysis at 1200 A/m2 were not as successful.

Jan 1, 2000

By Wei-ling Wang, Ryosuke O. Suzuki, Xiang-ning Meng, Miao-yong Zhu

"A finite-element thermal-stress model of continuous casting mold is conducted to predict deformation of copper plates and its change with different cooling structure. The results show that deformation behavior of copper plates is mainly governed by cooling structure and thermal- mechanical conditions, deformation amount is related to structure geometry, and a small deformation mutation occurs in cooper-nickel boundary due to different properties. The maximum deformation of hot surface centricities of wide face locate at 100 mm below meniscus and that of narrow face locate at meniscus and terminal of water slots and significant curvature fluctuations on both sides of copper-nickel boundary. The maximum deformation of centricities is increased up to 0.05 mm with thickness increment 5 mm of copper plates, and maximum deformations are only depressed 0.01 mm and 0.02 mm with increments of 1 mm nickel layer thickness and 2 mm water slot depth respectively.IntroductionIn conventional continuous casting of steel, a large amount of sensible and latent heat of molten steel dissipate in primary cooling zone and make continuous casting mold under enormous heating load giving rise to thermal stress, deformation, high-temperature fatigue and creep not only depress mold life-span, but reduce casting stability [1] Many studies focused more on heat transfer, solidification and shrinkage of solidifying shell to provide inverse proposals for optimizing cooling system and even designing new taper of mold [2,3], but it is generally useless to those of having been manufactured or being put into production. Therefore, mold-related forward problems show necessity to be discussed deeply, and stress and deformation distributions based on special thermal conditions in mold should be analyzed in order to explore suitable cooling structure of mold directly. Samarasekera et al. [4] examined heat flow and distortion of two-dimensional longitudinal sections and investigated effect of cooling water velocity, copper plates thickness and carbon content on formation of rhomboidity and longitudinal comer cracks. O'Connor et al. [5] developed a three-dimensional mathematical model to compute thermo-mechanical state in thin-slab mold and calculated temperature and deformation of mold wall to assess roles of various process parameters on impacting mold life. Thomas et al. [6] predicted temperature, distortion and residual stress in mold and indicated increased distortion requires increased remachining, which reduces mold life and increased residual stress increases the probability of a catastrophic crack failure. Park et al. [7l determined heat-flux profiles in funnel-shaped and parallel thin-slab molds based on an inverse heat conduction model and thermocouple temperature measured in-plant and put them into three- dimensional finite-element thermal-stress model to predict temperature, distortion and residual stress of mold wall. Korie et al. [SJ focused on prediction of temperature, distortion and residual stress in mold and in particular to clarify that mold life is significantly affected by temperature and its rigidity, but little effect by mechanical including clamping force, bolt prestress, friction and ferrostatic pressure. Meng et al. [9l predicted temperature and thermal stress in a slab mold and analyzed effect by cooling system geometry and casting speed quantitatively. In present study, a three-dimensional finite-element thermo-mechanical model with type-switched element is transformed from previous heat-transfer finite-element model [9l, and mold deformation is simulated in order to shed light on thermo-mechanical behavior with special thermal conditions and different mold geometry at high casting speed."

Jan 1, 2013

By WU Jian-hui

Keywords: metallic material; nickel powder; thermal decomposition; precursor; fibrillar powder; nanometer scale; passivation treatment The precursor thermal decomposition process of fibrillar nanometer scale nickel powder and passivation treatment of obtained powder are investigated, and the composition and morphology of the products are characterized by use of IR, TGA/DTA, XRD and SEM. The results show that the precursor morphology is a decisive factor to the product morphology of the nickel powder. The morphology of the product derived at low decomposing temperature is irregular. The nickel powders produced at the temperature higher than 480 coheres seriously. The product particles are reunited with the decomposition time prolong. The powder prepared under the optimal condition is fibrillar like woolen yarn; the grain diameter is less than 50nm.

Jan 1, 2005

By P. Henry

A novel electrochemical cell has been developed for the recovery of MnO2 from residue of pyrolusite ore leading loaded with Fe, Al Ni, Co and Si impurities, This new process can be considered as an alternative to the traditional methods : S02, H2O2 or bioleaching. It has been observed to proceed fairly rapidly and could prove to be a more economically viable process, as well as being more environmentally acceptable. Electrochemical characterization and kinetic studies have shown that MnO2 is effectively leached by electrogenerated ferrous ions at high current density from a pulp containing less than 5 g8 Fe. The chemical reactions are : Cathode (inox) : 2F23+ + 2e ? 2 Fe2+ Bulk: MnO2 + 2 fe2+ 4H+ ? Mn2+ + 2 Fe3+ + 2 H2O Anode (Pb-Ag) : H2O ? ½ O2 + 2H+ + 2e Global: MnO2 +2H+ Fe2+ = Mn2+ + H2O + 1/2 O2 The catholyte (MnO2 pulp) circulates upward in the expanded mesh cathode separated from the sulfuric acid solution anolyte by a separator which shows high mechanical resistance, low porosity, low potential drop, and reasonable cost. Laboratory and mini-pilot tests have led to the construction of an OT crating pilot plant (100 kg/hr) able to leach more than 95% of Mn, Ni, Co at 1000-1200 A/m2, 50°C with high faradic yield (> 95 %) and low power consumption (3.2 kWh/kg kWh/kg &4D). New applications like the treatment of spent Zn-Mn batteries, polluted soils, spent catalysts and oxide ore (cobalt, nickel) with electrogenerated redox species are now investigated at a laboratory and mini-pilot scale.

Jan 1, 2000

By Hande Cavus, Ibrahim Yusufoglu, Cem Kahruman

"In this study, ammonium tetramolybdate (ATM) was obtained as the intermediate product of ammonium heptamolybdate tetrahydrate (AHM). The thermal decomposition mechanism of ATM was investigated under nonisothermal and isothermal conditions in air and inert gas atmospheres. Nonisothermal experiments were carried out by TGA/DTA/MS while TG was used for isothermal conditions. Characterization of the decomposition products were carried out by XRD and FT-IR. The thermal decomposition of ATM in air proceeds in a single step and forms M0O3 while [(ÍÇ4)2è]ïïï83Ìïè3 and molybdenum suboxide (Ìïè3.÷, ÷=0.025) were obtained in the first and the second steps of thermal decomposition in He, respectively. Activation energies, frequency factors and kinetic model equations were determined for thermal decomposition reactions. Fractional conversion-time diagrams were compared with diagrams drawn according to kinetic model equation.IntroductionM0O3 is usually used as catalyst in industry [1]. AHM is the basic source to produce molybdenum containing catalysts used in petrochemistry [2]. The oxides of Li, V, W, Te, Bi and Sn are doped in M0O3 to produce catalysts, which find commercial applications in the industry. The properties of M0O3 are affected by dissolution, settling, calcination, drying and thermal decomposition processes [1]. There are several studies in the literature about the thermal decomposition of AHM and the characterization of the decomposition products in different gas atmospheres and at various heating rates [3-19]."

Jan 1, 2012

By Yotamu Stephen Rainford Hara

"The aim of our work is to investigate a low energy and clean route for the recovery of copper and cobalt from complex sulphide mineral concentrates. The mineral concentrates were roasted in air, in the presence of CaO (MS + CaO + 202 =MO+ CaS04) at temperatures below 973K. The roasted products containing CuO, CoO and Fe203 were carbothermically reduced at 1073K within an hour to preferentially reduce copper and cobalt. The kinetics of reactions were studied using the thermogravimetric technique and by characterisation ofreaction products using the XRDSEM-EDX techniques. The effects of MS:CaO ratio, roasting temperatures and physical nature of the mineral concentrates were analysed. The method for capturing S02 by forming CaS04 was analysed for reuse in the process. The energy balance for the above process is compared with that of conventional continuous smelting/converting process.1.0 IntroductionCopper sulphide mineral concentrates from Zambia contains substantial amouot of cobalt. The cobalt metal content in the concentrates ranges between 0.7 and 2 % weight, which corresponds to 3 and 9 % weight copper, based on the spot price of copper ($7 386/tone) and cobalt ($31 000/tone). Although the traditional approach using a combination of roasting-leaching-electrowining steps can be applied to recover copper and cobalt from sulphide mineral concentrates [1-4], there are two major draw backs of the traditional process: (i) the S02 emitted during roasting is too lean for economical conversion for sulphuric acid manufacture, which causes serious environmental pollution. (ii) silver and gold which are normally present in the sulphide concentrates are lost out [5] because they are not leachable by H2S04 or HCl which are the common leachants. The above two problems have been overcome by adopting flash smelting in which a rich S02 gas above 20% is produced [1, 5] and successfully converted into sulphuric acid. The precious metals tend to partition to blister copper and recovered during refming. However, nearly all cobalt is lost into the slag phase uoder oxidising condition which prevails during flash smelting. It is important to note that the cobalt content in the slag can be up to 2.6 % weight [6]. The recovery of cobalt from the slag is a process which requires huge amouot of energy since the slag is smelted above 1873K [6]. With a view of minimising the amouot of energy and S02 emission during metal recovery, our investigation involves roasting the sulphide concentrates in the presence of lime and reducing the roasted samples with carbon."

Jan 1, 2013

By Linda C. White

The use of red mud, a waste product of the ?Bayer? process for bauxite refining, was investigated for its arsenic removal effectiveness from aqueous solutions under various conditions. Red mud efficiently removed As(III) between a pH range of 7.6 and 9; and As(V) in the pH range between 5.5 and 6. Pre-washing of the red mud with salt water considerably improved its arsenic adsorption capabilities. With appropriate red mud dosage, the residual arsenic in solution was decreased below the regulated acceptable arsenic limit (0.1 mg/L) from aqueous industrial wastes. The arsenic adsorption followed first-order rate kinetics and fitted the Langmuir isotherm model. Results suggest that red mud is potentially a useful adsorbent for removal of arsenic from contaminated water or industrial waste solutions.

Jan 1, 2003

By Liyuan Chai

In this study, spent grain was used as an adsorbent for the removal of Hg(II) from aqueous solutions, the process parameters such as contact time, solution pH, adsorbent dose, and initial Hg(II) concentration were studied in batch experiments. The initial adsorption process was fast, 91.08% of adsorption occurred within 5 min and equilibrium was reached at around 30min. Adsorption process was found to follow pseudo-second-order kinetics. The equilibrium data were better fitted to Langmuir isotherm than Freundlich isotherm with the maximum adsorption capacity 41.36 mg/g. The structure and component of spent grain before and after adsorption of Hg(II) were investigated using scanning electron microscope(SEM) and energy dispersive X-ray analysis(EDAX), these analysis also confirmed the adsorption of Hg(II) onto spent grain. The results indicated that spent grain had potential as a new inexpensive adsorbent for Hg(II) removal from aqueous solutions.

Jan 1, 2009

By Hamed Mirzadeh

The hot working behavior of 17-4 PH stainless steel was studied using the hot compression test at temperatures of 950-1150 °C with strain rates of 0.001-10 s-1. A step by step procedure for data analysis in hot compression test was given. The work hardening rate versus stress curves were used to reveal whether or not dynamic recrystallization (DRX) occurred. At low Zener- Hollomon (Z) parameter, this material showed a new DRX flow behavior, which was called Multiple Transient Steady State (MTSS). At high Z, as a result of adiabatic deformation heating, a drop in flow stress was observed. The general constitutive equations were used to determine the hot working constants of this material. Moreover, after a critical discussion, the deformation activation energy of 17-4 PH stainless steel was determined as 337 kJ/mol.

Jan 1, 2010

By Hwasoo Park

Keywords: FC mold, Argon, Magnetic, Solidification Fluid flow plays a significant role for steel surface quality in continuous casting. Although water models are able to model fluid flow, the flow pattern is not of practical interest since the moving solidifying shell cannot be accounted. Computer modeling has become a popular and dependable tool to analyze the complex phenomena occurring in continuous casting. In this numerical simulation we coupled momentum and energy equations considering the solidification of steel along with turbulence ?-e model. The vertical bending mold is equipped with bifurcated nozzle with 15 degrees of port angle. FC mold is supplied with DC induced magnetic fields. Influence of argon and magnetic fields on molten steel flow and heat transfer is investigated by solving momentum equations adding source terms due to multiphase ? magneto hydrodynamics. The results show that magnetic fields reduce the jet velocity from port by lower magnetic core induced field but the influence on meniscus velocity is complex to describe. Magnetic fields increase surface temperature and homogenize its distribution on surface and inside a mold.

Jan 1, 2005

By Sadegh Firoozi

Experiments measuring the kinetics of oxidation and making visual observations of the oxidation of approximately 6 g static lead baths containing arsenic, antimony and tin were conducted in the temperature range from 500 to 600 oC. A range of repeatable behaviours were observed, notably: the formation of a coherent, solid oxide layers on pure lead and lead-tin alloys; the formation of liquid oxide droplets during the initial oxidation of lead-arsenic and lead-antimony alloys and the eventual formation of a complete oxide layer covering the entire free surface of these alloys. Thermogravimetric measurements revealed that the rate of oxygen uptake was strongly influenced by the form of oxides being generated at the melt/gas interface. Compared to the rates of oxidation of pure lead, arsenic increased the rate of oxygen uptake throughout the temperature range via the formation of liquid oxidation products. The presence of antimony resulted in a moderate increase in the rate of oxygen uptake as compared to arsenic. Tin was effective in lowering the rate of oxidation even in the presence of arsenic because the oxidation product was always a coherent layer that acted as a physical barrier to oxygen transport to the underlying alloy.

Jan 1, 2006

By Yahui Feng, Zhiwen Wu, Chen Chen, Xin Hong

Large amounts of copper slag containing about 40 wt% iron is generated during the process of producing copper. Recovery of iron from the copper slag is very essential not only for recycling the valuable metals and mineral resources but also for protecting the environment. The purpose of this study was to investigate the possibility of separating fayalite by oxidation-reduction process into Magnetite and silicate phases in intermediate temperature condition. Experimental results show that when the oxidation reaction at 1000℃ for 120min and the oxygen flow is 0.1L/min, most fayalite decompose to hematite, less part of magnetite and silica. And then, the mixture of carbon and oxidation product is pressed into blocks and reduced to magnetite and silica at 900℃ for 90min. A magnetic product containing about 57.9wt% iron was obtained from the magnetic separation under a magnetic field strength of 100 mT.

Jan 1, 2015

By P. N. Anyalebechi

The effects of solidification rate (0.4-26.1 K/s) and alloying elements on the cast microstructures of aluminum alloy 5182 have been investigated with directionally cooled laboratory-size ingots. The alloying elements examined included Mg (3.6-4.7 wt.%), Mn (0.35-0.75 wt.%), Fe (0.11- 0.42 wt.%), Cu (0.03-0.25 wt.%), and Si (0.11-0.28 wt.%). These reflect the chemical compositions of AA 5182 end stocks with high recycled used beverage container (UBC) content. For a given chemical composition, the average dendrite cell and constituent phase particle size decreased with increase in average solidification rate. In general, within the level investigated, Mg did not have a significant effect on the types, volume fractions, and average sizes of the constituent phase particles. However, increase in Mn, Si, Fe, and Cu increased average sizes and volume fractions of the constituent phase particles.

Jan 1, 2010

By Teixeira

An experimental investigation on the kinetics of oxidation of As(III) with H202 in synthetic effluent solutions followed by precipitation of Fe/As (V) compounds was carried out. The variables investigated were: As concentration (200 -3000 mg/l) , oxidation pH (2.0 -11.0), oxidation temperature (25 -800C) , H202 stoichiometric excess (50% -100%), precipitation pH (5.0 -7.0), precipitation agent (Fe2+ -Fe3+). Fixed conditions were, Fe/As molar ratio (6:1) and stirring speed (560 rpm). The results were empirically modelled. The precipitates obtained were amorphous. The precipitates were checked upon their environmental stability according to the United States Environmental Protection Agency (U.S.E.P.A.) Toxicity Test, and were considered to be adequate for deposition in impermeable waste dumps. The combined Fe/H202 detoxification process, in selected conditions, was able to reduce the As contents of effluents containing 1600 mg/l As to 0.1 mg/l, in about 2 1/2 hours of total processing time.

Jan 1, 1990

By Pietro Navarra

A great deal of effort has been expended on how to optimize conventional water cooling circuits in furnace cooling elements, and the results have been largely satisfactory. However, there is a general agreement that the proximity of high-pressure water passages to the flow of molten furnace products is a safety concern. Nonetheless there exists little alternative to the formula: increasing furnace integrity implies the incorporation of more extensive forced-convection water cooling systems. Recent developments in evaporative cooling technology have resulted in the development of a high-capacity heat pipe capable of operating under the thermally intense environments of a metallurgical furnace. The system functions using several kg of a working fluid (water) in total, has no moving parts, and allows for a significant reduction in cooling water requirements. Full-scale pilot tests of a copper tap hole and slag launder were done in 2003 and2005, with detailed results given in this paper.

Jan 1, 2006

By A. J. Sideris

It is known that Mg can act as a catalyst/solvent in the high pressure high temperature diamond synthesis. However, above pressure levels of the order of 7 GPa, and temperatures from 1700 ? 1800oC, it was not possible yet to use Mg for the industrial production of diamond. A possible alternative is the use of MgNi based alloys. However, owing to the great Mg reactivity, it was consider, so far, a difficult task to deal with such alloys. The present work presents successful results regarding the production of MgNi alloys, with different composition, at high pressure conditions. The behavior of the alloys and their microstructural characterization is analyzed.

Jan 1, 2006

By Wang Jia, Chai Li-yuan, Zhang Jin-Long, Peng Bing, Zhang Qiang

"Electrolytic manganese dioxide (EMD) residue was mixed with shale and fly ash as the main materials to make solidification/sintering brick for the utilization of the residue from EMD production. The effects of sintering temperature, sintering time, solid waste content and cooling process on its mechanical properties and toxic elements solidification were investigated according to compressive strength and leaching toxicity. The results showed that the calcined residue had capability of solidifying toxic metals and exhibited perfect strength after treated in the optimal parameters of EMD residue below 50%, temperature at 1000-1100°C, time3-5h, and semi-quenched at 600°C1 InstructionSolid clay-brick holds the leading position among building materials for a very long time in China. The traditional technique of making clay-brick has the drawbacks of backward process, simple facilities and single product. Since Chinese Reform and Opening-up, urban-rural construction and real estate have been booming with the rapidly development of national economy and science technology. The problems of ruining fertile land, environment contamination and high energy consumption in the traditional technique of clay-brick making have not been solved yet. On the other hand, more than 7 billion tons of industrial wastes are accumulated over years which occupies over 6.7 million hectares filed and causes serious environmental problems[1-31. Strategy present in ""The Chinese Agenda of the 21st Century"" required the production of wall materials less energy conservation, land saving and waste recycling.Coal gangue[4-9l, fly ash[I0- 13l, sludge from waste water treatment and tailings of gypsum, pyrite, copper mine, high silicon containing iron, asbestos and ects [l4-lSJ are the solid wastes used for brick making around the world. There are two kinds of process for brick making, high temperature sintering and low temperature steam curing[19•201. Although the technology of two brick making made great progress and got widely application in construction field, no precedent for preparing sintering-bricks with EMD residue as materials occurred in China because of its complicated processing technics and lack of sufficient practical experience to guarantee the bricks' quality.In this study, EMD residue was mixed with shale and fly ash as the main materials to make solidification/sintering brick. The effects of sintering temperature, sintering time, solid waste content and cooling process on its mechanical properties and toxic elements solidification were investigated according to compressive strength and leaching toxicity."

Jan 1, 2011

By Sung Wng Kim

The binary antimonide compounds with the skutterudite structure have a potential for thermoelectric applications because of the high carrier mobility, high thermoelectric power, and relatively low thermal conductivity due to the complex crystal structure. However, the room temperature thermal conductivity of these skutterudite materials is as high as about IOW/mK with an estimated 80-90% contribution from the lattice thermal conductivity. Because the lattice thermal conductivity of related ternary skutterudite compounds can be substantially reduced due to the additional phonon scattering, a study of thermoelectric properties of these compounds is of interest. The binary IrSb3, ternary Ir1.xRuxSb3 and Ir(MxSb1.x)3(M=Ge, Sn) compounds were prepared by hot pressing of pre-reacted powders. We have measured the electrical resistivity, thermoelectric power, and thermal conductivity, in a temperature range from room temperature to 973K. The binary IrSb3 compound is found to have P-type electrical properties exhibiting a good Seebeck coefficient (up to 225µV/K around 773K), electrical resistivity(5x10-5Ohm M around 933K), and relatively low thermal conductivity(6W/mK around 950K). The lattice thermal conductivity, K[2] was calculated from the Wiedemann-Franz relationship.

Jan 1, 2002