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By Dan Wang, Yuanbo Zhang, Guihong Han, Guanghui Li, Tao Jiang, Yanfang Huang

"Hematite concentrates are characterized by bad high-temperature reactivity and poor balling index, which restrict their large-scale application in the production of oxidized pellets. An organic additive, namely MHA, was authorized and used as binder recently in China. Compared with bentonite, the effects of MHA on compressive strength of hematite pellets at various firing conditions were investigated in this study. Experimental results showed the compressive strengths of preheated pellets with different binders were increased with increasing the preheating temperature and time. The compressive strength of preheated pellets with MHA binder was lower than that of pellets with bentonite, which can be ascribed to the high porosity of pellets with MHA binder. However, the compressive strength of roasted pellets with MHA binder was higher than that of pellets with bentonite. The compressive strength of finished pellets balled with MHA binder 1.0 wt% could meet the operation requirements of grate-kiln process.IntroductionHematite concentrates are characterized by bad high-temperature reactivity and poor balling index, which can lead to the appearance of those problems with increasing the energy consumption, shortening the useful life of equipment, and finally increasing the operation cost of oxidized pellets plants [1-2]. Some investigations have been conducted based on improving the pelletizing technique of hematite concentrates, such as pretreatment of raw materials [3-7], optimization of ore proportioning [8], addition of solid fuels [9-16], and so on. Employing high pressure grinding roller for the treatment of hematite concentrates revealed that the mechanical strength of wet green pellets could be improved. However, the mechanical strength of fired pellets was not improved obviously [7]. Huang, et al., pointed out that the preheating and roasting temperature may be decreased and the compressive strength of fired pellets could be increased by blending a certain proportion of magnetite concentrates with hematite [8]. Nevertheless, there are a variety of magnetite ores different in physical and chemical properties in China, resulting in the instability operation [17]."

Jan 1, 2012

By Yuanbo Zhang, Guihong Han, Guanghui Li, Tao Jiang, Zengqing Sun, Yanfang Huang

"Because of small specific surface area and poor ballability, vanadium/titanium-bearing magnetite is difficult for production of oxidized pellet. A novel organic copolymer binder, modified humic acid (MHA), has been authorized recently in China. Effects of the novel MHA binder on the quality of V/Ti-bearing magnetite pellets are studied in this paper. Experimental results show the MHA binder can obviously improve the strength of green pellet. Because of better heat endurance, the MHA binder pellet has a higher strength than Peridur pellet under the same preheating conditions. Moreover, TFe grade of pellet with the MHA binder is much higher than that of the bentonite pellet. The strength of preheated pellet containing MHA binder of 0.25%~1.0% meets the requirements of oxidized pellet production by grate-kiln process. Comparatively, MHA is a promising orgainc binder for iron ore pellets. Its price is only one tenth of Peridur price and about 3 times of bentonite price.IntroductionThe iron-making practices show that the use of pellet is beneficial to blast furnace life, productivity and fuel savings. Therefore, many iron-making plants have expanded the production of oxidized pellets in order to meet the needs of modern large-scale blast furnaces [1]. Presently, bentonite is widely used to improve the quality of iron ore pellets. The negative effects of using bentonite include decreasing total iron (TFe) grade and degrading the metallurgical properties of the final products [2, 3]. Many studies, therefore, have been conducted on the application of organic binders to overcome the weakness of the inorganic bentonite. In comparison with inorganic binders, one of the biggest strengths of organic binders is low residual silica content [4]. However, those studies showed that the economics of foreign organic binder addition into pellets was not attractive. For example, the compression strength of preheated pellets and roasted pellets are both too low, resulting in powder generation and ring formation in the industrial rotary kiln [3, 4]."

Jan 1, 2011

By W. K. Choi

Stainless steel exposed to wet environments at ambient temperature is subject to the formation of a surface biofilm. Depending upon the prevailing environmental conditions (dissolved oxygen, pH, Eh, concentration of cationic/anionic species), the biofilm may stimulate corrosion through formation of differential aeration zones and concentration cells. Corrosion significantly impacts the United States economy, since on a yearly basis, corrosion induced losses are estimated to be over $200 billion. A large portion of this corrosion is imputable to bacterial activity, and basic information is needed for a better understanding and control of the biocorrosion phenomenon. The present study has investigated the influence of Thiobacillus ferrooxidans in the corrosion of American Iron and Steel Institute (AISI) 304, 316 and 416 stainless steel samples. The formation of biofilm and microstructural changes on the surface of stainless steel samples and their weldments were assessed by microscopic examination, and the changes in the mechanical properties by stress-strain measurements. The significance of the results will be discussed.

Jan 1, 1993

By Dongxing Wang, Zhang Ting-an, Xiaolong Li, Yan Liu

Recent years, bottom blown oxygen copper smelting process has been widely used in China. Besides many advantages such as autothermal operation, this technology is still in developing stage. This topic aims at promoting the dispersion of materials charged into the bottom blown smelting furnace used in the process. Based on the similarity theory, a 1/5 scaled physical model of smelting furnace was constructed. Polypropene particles were used as charged materials. High-speed camera was used to record the phenomenon of the particles dispersion under different gas-flow rates, nozzle diameters and installation angles of nozzles. Image processing software was used for obtaining the particles concentration under different conditions. Results show that when the gas flow rate increases, charged materials disperse better. With the same gas flow, the increasing of nozzle diameter promotes the dispersion effect of materials. The effects of installation angles are opposite for nozzles with diameter of 2.50 and 5.92 mm.

Mar 1, 2017

By Kazuki Morita

A new route to produce solar grade silicon (SOG-Si 6N) from metallurgical grade (MG-Si 98%) has been developed in Japan, which may satisfy the increasing demand for solar cells in the near future. Since some elements such as P and B have very large segregation coefficients, solidification refining is not effective for their removal and costly processes, such as electron beam vacuum melting and oxidation plasma refining, are required. According to our previous results which showed the effectiveness of leaching procedure with Ca addition for Fe and Ti removal, possibility of P and B removal by acid leaching was focused expecting that their affinities for Ca in molten silicon might be considerable. Hence, the effects of Ca addition on the thennodynamic properties of P and B in molten silicon alloys have been investigated for overall control and optimization of the SOG-Si production process in the present study. The interaction parameters between Ca and P, and Ca and B were determined by chemical equilibration techniques at 1723 K. Although the interaction parameter between Ca and B was slightly negative, that between Ca and P showed a large negative value. Also, the results for the leaching test with various amount of Ca addition revealed that the removal fractions of both elements, especially P, drastically increased with increase in the Ca content, which showed very good agreement with the prediction from the interaction parameters derived in the present work. The present results suggest that the preliminary leaching procedure can reduce the processing time and energy for SOG-Si refining. Keywords: Silicon, Solar Cell, Refining, Acid Leaching, Thennodynamics. Interaction, Phosphorus, Boron, Calcium

Jan 1, 2003

By M. Hashimoto

The equilibrium distribution ratios of sulfur between molten copper and CaO-fluxes containing caF2 and caC12 were determined in the range of 1300° to 1400° C under carbon monoxide. The rate of approach to equilibrium is rapid and increases with increasing CaCll concentration. In CaO-CaFl-CaCl2 fluxes, the distribution ratio varies in a complex way with temperature and CaFl concentration. The results are compared with those obtained with the binary fluxes of CaO with BaFZ and MgFl ?

Jan 1, 1983

By S. H. Amini

The effects of CaF2 and ilmenite on dissolution rate and diffusivity of CaO in calcium alumino-silicate based slag in a temperature range of 1500 ? 1600 ºC were studied by using the rotating disk/cylinder technique. The effect of rotation speed on the rate of dissolution in the base slag indicated that mass transfer in liquid slag played a significant role in controlling the dissolution. At a constant rotation speed, the effect of 5 wt% addition of fluxes tothe slag on the dissolution rate was investigated at various temperatures. While CaF2 had the highest effect, addition of ilmenite increased the rate of dissolution significantly. The diffusivity of lime in these slags was quantified using the dimensionless mass transfer correlations for rotating disk/cylinder in the melt. The diffusivity values were deduced using the data on dissolution rate and solubility of lime in the slags. The measured diffusivity in base slag at 1500 C was found to be about 1.32 10-5 cm2/s and increased to 3.07 10-5 cm2/s at 1600 °C. Addition of 5wt% CaF2 increased the diffusivity by a factor of 3 to 5, while 5wt% ilmenite increased the diffusivity by a factor of 2 to 3 in the temperature range of 1500 to 1600 ºC. The two examined fluxes reduced the activation energy of diffusion.

Jan 1, 2006

By D. I. Davidov, D. A. Shishkin, M. B. Rigmant, E. P. Romanov, N. N. Stepanova, N. V. Kazantseva

The Co-19 at.%Al-6 at.%W alloy was prepared by two methods of casting. We used arc melting under an argon atmosphere with casting into a copper water-cooled casting mold and induction melting furnace with casting into a ceramic Al2O3 mold. According to the X-ray and SEM analyses, phase compositions depend on the cooling rate of the ingot after melting. After arc melting, the cast alloy has a three-phase structure, consisting of  cobalt (FCC), intermetallic phases CoAl (B2) type, and Co3W (DO19) type. After the induction melting, the alloy has a three-phase structure, consisting of  cobalt (FCC), intermetallic phases CoAl (B2) type, and Co7W6 () type. All phases in the investigated ternary alloy at the room temperature are ferromagnetic. Curie temperatures of all obtained phases were defined. It is shown that the magnetic properties of the studied alloy are typical for soft magnetic materials.

Jan 1, 2015

By S. N. Monteiro, J. Alexandre, N. Cerqueira, B. C. Mendes, A. R. G. Azevedo, G. C. Xavier

Brazilian civil construction generates a huge amount of waste in different stages of construction, mainly due to the work methodology used in construction sites. The objective of this work is to study the inclusion of the residual of the civil construction in the sand mass in 0, 10 and 20%, with mortars used to cover masonry. For this study, the beneficiation of the material in crusher was obtained so that it obtained granulometry similar to sand and the most recurrent technological tests in mortars for this purpose, as the mechanical resistance (compression and flexion), water absorption and determination of the coefficient of Capillarity beyond the index of consistency, according to Brazilian norms, that define parameters of execution the technological tests. The results showed that the mortars after the incorporation presented value within the norm except the consistency and capillarity to the 20% that presented problems of fluidity and durability, hindering its use.

Mar 1, 2018

By Shunhong Huang

To improve understanding the effect of heavy metal chromium on soil biota, laboratory incubation experiment was carried out in the soils contaminated artificially with five concentrations of chromate (50, 250, 500, 1000 and 2000 mg kg_1 soil) over time (35 days). The population and diversity of bacteria, fungi and actinomycetes in soils were measured as indicators of soil microbial processes in the disturbances mentioned above. Incubation experiment results elucidated that the population and diversity of microorganisms decreased with increasing Cr (VI) concentration. Furthermore, various microorganisms showed different sensitivity to total Cr contamination. The sensitivity of microbial population to chromium contamination was in the order: actinomycetes >bacteria>fungi. The resulted implied that the microorganism can be used as an indicator of chromium contamination.

Jan 1, 2008

By Xiao Long, Ting Wu, Lilong Zhu, Qian Wang, Shengping He

"During the continuous casting of peritectic steel slabs, mould fluxes with high crystallization capacity are usually chosen for improving slab surface quality. However, the lubrication condition of casting shell also could be deteriorated. Since precipitation of crystals within liquid slag film can change the composition and property of liquid slag over solid-liquid slag film interface region, its impacts on continuous casting process also are not clear. In order to clear this phenomenon, an experiment method was put forward, and mould fluxes for peritectic steel slabs continuous casting were selected and examined. The results reveal that after crystals have been separated, the crystallization capacity of leftover liquid slag increased with different levels, which could deteriorate the lubrication condition of casting shell and cause a series of problems. Thereby, mould fluxes with high crystallization capacity at beginning for heat transfer control and then weaker after crystallization should be considered in the future.IntroductionIn the continuous casting of peritectic steel slabs, contradiction between heat transfer control and slab shell lubrication by mould fluxes has been treated as a key problem for maintaining a smooth manufacturing process [ 1]. Strong and uneven horizontal heat flux over the meniscus region will cause uneven solidification of casting shell, especially for peritectic steel slab with enormous volume change caused by phase transition. All of those could cause surface defects like longitudinal crack [2-4]."

Jan 1, 2013

By Sh. Najisi, O. Lashkari, M. R. Ghomashchi, A. Charette

"One of-the important parameters in casting and foundry technology is the fluidity of molten metal. This parameter becomes particularly important when casting thin wall parts. Therefore, understanding and controlling fluidity plays a major role in fabricating sound and defect-free cast components.Semi-Solid Metai SSM, slurry is a mixture of solid and liquid, mushy zone, with solid volume fractions of 0.1-0.5 and apparent viscosity close to oil viscosity at room temperature. It flows easily under pressure and capable of making complicated shapes with high degree of die filling and integrity.In this study, the ability of the semi-solid slurry to continue to flow is investigated through the effect of different fraction solids and holding temperatures. The results show that in mechanically stirred, MS, semi-solid 356 Al-Si alloy, increasing fraction solid reduces fluidity. Furthermore, the results of MS-alloy are compared with a newly patented Rheocasting route, i.e. SEED, Swirl Enthalpy Equilibrium Device to highlight the differences of the two processes. In addition, the interrelationships between microstructural evolution and fluidity are discussed."

Jan 1, 2004

By Onuralp Yucel, Ahmet Turan, Murat Alkan, Hasan Ozer

SHS (Self-propagating High-temperature Synthesis) is one of the important methods to synthesize B4C powders. The process contains the reaction of boron oxide powders (B2O3) with magnesium reducing agent and carbon black carburizer. SHS products are leached in HCl media to purify synthesized B4C powders in the following step. In the present study, effects of various functional additives (KClO3, KHSO4, MgSO4.7H2O, NaCl, MgO and Na2SO4) in the SHS stage were carried out. Various proportions of the additives were mixed with the initial SHS charge mixtures. Two different molar ratios were employed in the initial SHS mixtures as 1:3:0.8 B2O3:Mg:C and 1:2.5:0.8 B2O3:Mg:C. After the SHS step, HCl leaching process was applied to the SHS products. Filter cakes were dried and characterized by using X-Ray Diffraction Spectroscopy, BET and chemical analysis techniques.

Jan 1, 2015

By Chuanguang Bi, Wenbin Dai, Hongtao Wang, Mansheng Chu, Zhenggen Liu

Coke oven gas (COG) injection is considered as one of feasible measures to reduce carbon emission of BF. The effects of COG injection on the reduction of iron-bearing burdens were numerically simulated by means of multi-fluid BF model, which revealed that with increasing COG injection rate, solid temperature gradually decrease, in-furnace H2 concentration increases, the reduction of magnetite and wustite by H2 is evidently accelerated, the reaction rate of wustite by H2 reduction is enhanced and the reduction degree of mixed burdens is strengthened. Under this hydrogen-enriched condition, metallurgical properties of iron-bearing burdens were experimentally investigated. The GB/T13242-91 test results showed that with increasing COG injection rate, the reduction swelling index of oxidized pellets decreases while the reduction ratio of pellets increases. The softening-melting tests suggested that softening interval of mixed burdens increases from 163.6 to 228.3 °C while melting interval decreases from 147.3 to 92.4 °C. The cohesive zone moves downwards and becomes narrow. The permeability of mixed burdens is improved. In terms of metallurgical properties of iron-bearing burdens, COG injection benefits to improve BF performance.

Mar 1, 2017

By Jorge Alberto Soares Tenório, Denise Crocce Romano Espinosa, Luciana Harue Yamane

"The present work investigated the effect of inoculums volume on bioleaching to recover metals from printed circuit boards using Acidithiobacillus ferrooxidans-LR. Printed circuit boards from obsolete computers were mechanically processed by comminution followed by magnetic separation, and the obtained non-magnetic fraction was used in the bioleaching experiments. A shake-flask study was carried out on the non-magnetic fraction samples using a rotary shaker at 30°C, 170 rpm and different volumes of oxidized culture solution as inoculums (%v/v): 5, 10, 20, 30, 40, 50 e 60. The oxidized culture solution was prepared inoculating pre-adapted bacteria Acidithiobacillus ferrooxidans-LR (5%v/v) in 200mL T&K medium. Leaching in acidic ferric sulphate was also performerd. The analyzed parameters were pH, ferrous iron concentration and metals analysis (AAS). The results showed that using 10%v/v of inoculums were extracted 99,2% of copper and 60% of aluminum by bioleaching. Zinc, lead and tin extraction were not influenced by bacterial leaching and extractions rate were obtained by chemical leaching promoted by acid medium. Ferric iron leaching extracted less copper (35%) than bioleaching. SEM analysis shown surface difference between samples of non-magnetic fraction before treatment and after bioleaching, showing corrosion pits formed by the bacteria contact.IntroductionWaste of electrical and electronic equipments (WEEE) has been target of discussion due to environmental, political and economical issues involved. Around 17 million of computers are discarded annually in the world due to malfunctioning equipment or because technologies become obsolete [1,2]. In contrast, only the central processing unit (CPU) of computers weights around 3kg. From this data, it can be calculated that 51 million kilograms of CPU waste are discarded yearly. This calculation was performed considering only the CPUs, disregarding the cathode ray tubes and liquid crystal displays of monitors [3,4]. Because of the amount that has been accumulated, e-waste has become a global problem but also can be an alternative source to recover valuable materials [5,6]."

Jan 1, 2012

By B. Q. Li, Y. Shu, K Lynn

"This paper discusses the effects of magnetic field and internal radiation on the melt flow and solidification morphology during solidification processing of oxide crystals for optoelectronic and remote sensing applications. The numerical solution of the integral differential equation characterizing the internal radiation and the magnetohydrodynamic equations describing the magnetic and transport phenomena is obtained by applying the combined discontinuous and continuous finite element method. The results show that both internal radiation and an externally applied magnetic field can have important effects on the melt flow and solidification behavior during the melt processing of oxide materials.IntroductionOptical single crystals are widely used in optical and electronic devices. These crystals are often grown from high temperature oxide melts under strictly controlled conditions. As in the well-known single crystal growth processes for semiconductor wafers, thermal gradient in the melt is a major contributing fuctor to the oxide melt pool. Unlike the semiconductor single crystal growth processes, however, the oxide melt is semitransparent and internal thermal radiation plays an important role in redistributing the thermal energy in the melt pool. Our recent experience with pilot-scale plant measurements also shows that the oxide melt is electrically conducting, although its electrical conductivity is considered much lower than the liquid metal or semiconductor melt.The fact that the oxide melt is absorbing and emitting in the thermal radiation frequency range makes it difficult to study the thermal energy transport in the melt pool. This is because thermal radiation is governed by a hyperbolic differential equation, which is different from those describing the transport processes in liquids. Also, our understanding of how thermal radiation interacts with other transport mechanisms such as convection and conduction is rather limited at point in time, in particular in high temperature oxide melts for optical single crystal processing."

Jan 1, 2004

By Leszek Blacha

Since several years aog there is noted an increasing importance of the metallurgical vacuum technologies. This refers mainly to the extra furnace steel treatment processes, melting of steel and special alloys in the induction and arc vacuum furnaces, as well as refining processes of nonferrous metals. In the presented work, there is discussed a phenomenon of evaporation of volatile components of metal bath under reduced pressure with description of kinetics of this process. In this article are presented are the evaluation of the mass transfer coefficients in the melt and gaseous phase. Based on results of our own research on removal rate of impurities from liquid copper (bismuth, lead) in vacuum refining process, it is determined the thickness of hypothetical boundary layer in the gas phase. This allowed to formulate a general kinetic equation defining the evaporation rate of gaseous components from metal bath. The values of mass transfer coefficients determined from this equation were compared with experimental results by other authors working on the evaporation effect of melt components of metal alloys.

Jan 1, 2006

By Yuanbo Zhang, Daoyuan Zhang, Youlian Zhou, Guanghui Li, Tao Jiang

"Modified humic acid (MHA) has been developed by Central South University (CSU) and authorized in China. It has been reported that MHA is an effective binder for oxidized pellets prepared from specularite concentrates. In this research, effects of MHA binder on roasting behaviors of the specularite pellets are studied. MHA is an organic binder, containing much carbon, hydrogen, oxygen, etc. During the roasting, MHA can provide some heat because of combustion of hydrocarbon, which is beneficial for the recrystallization of Fe2O3 in the specularite pellets at high temperature. Simultaneously, part of hematite particles within the pellets are firstly reduced to magnetite, then, magnetite is oxidized into secondary hematite, which obviously improves the roasting performance of specularite pellets.IntroductionOxidized pellets have been widely used in steel production as a kind of high quality burden for blast furnace ironmaking [1]. In recent years, production of oxidized pellets is developing very fast. Therefore, the supply of high quality magnetite concentrates, which is the most suitable for pellet production, becomes scarce. It is imperative to pursue new alternative materials for oxidized pellet production [2]. Specularite concentrates have attracted widespread attention due to the advantages of high total Fe grade and low impurity content. However, due to the poor ballability and firing performance, specularite has not yet been widely applied into pellet production [3, 4]."

Jan 1, 2012

By ZhiLong ZHAO, Lin Lin, Zhancheng Guo, Jingtao GAO, Huiqing Tang

Grain sticking often occurs in the fluidized bed reduction of f ine iron ore, which is closely related to the precipitation morphology of metallic iron on the surface of ore particles. In this work, simulating the gas-solid reduction process of iron ore, in situ observations were carried out to investigate effects of doping mineral oxides on the precipitation morphology evolution of metallic iron during reduction of iron oxides with CO. Results indicate that the precipitation morphology of metallic iron is related to the quantity of doped mineral oxides. The minimum mole fraction of doped oxide ( xyOA N ) that can inhibit the growth of iron whiskers is related to its cation radius ( Ax r ), extranuclear electronic layers ( Ax n ) and valence electrons ( Ax q ). Their relation can be expressed as:

Jan 1, 2016

By W. Murray Small

Nickel plays an important role in determining the properties of many stainless steels and superalloys. Cobalt also contributes significantly to the performance of certain grades of superalloys. A major technical aspect, in which both of these metallic elements are involved, concerns the solubility of nitrogen in these classes of alloys. Beyond certain content limits, dissolved nitrogen may contribute to the deleterious mechanical behavior by these alloys. It is therefore essential to control the level of this element during alloy processing. In this paper, results from several experimental studies have been assembled and are analyzed to describe phenomena related to the individual effects of nickel and cobalt on the solution of nitrogen in several groups of alloys. Both solid and liquid alloy systems are considered. This information may be used as a guide to limit or control the presence of this interstitial element in alloys.

Jan 1, 1993