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By Abhishek Lahiri, Animesh Jha

"A new technique for the selective separation of rare earths and impurities from lower grade titaniferous ores has been developed which will reduce the overall reduction in the energy costs, and therefore the CO2 generation by at least an order of magnitude during the chlorination and waste handling stages of TiO2 to TiCl4 reaction. The process includes roasting the ilmenite ore with alkali followed by water washing step, which removes nearly 80% of oxides of lanthanide and actinide elements present in lower grades of titaniferous minerals. In the context of preferential separation of rare- 3+ + earth and actinide oxides, we have examined the roles of Al and K ions on the lattice structures of ilmenite and complex titanate as the product layer forms during the roasting in air in the presence of potash. The composition of the mixtures of oxides derived from the separation process shows that the mixture of rare-earth oxides m ay be a high-value co-product of the overall beneficiation process.IntroductionWorldwide the production of synthetic rutile is carried out either by the sulphate or the slag-making followed by fluidised bed chlorination of TiO2 enriched slag granules. The chlorinated gas is then re-oxidized to make white pigment grade TiO2. The waste generated by the sulphate process is predominantly iron sulphate, which has limited use in the water treatment plant. The remaining wastes from the sulphate process undergo further treatment using filtration followed by evaporation and thermal decomposition after which it is disposed into deep sea. On the other hand the chloride waste is extremely hazardous and requires special case by neutralisation, followed by impoundment in a managed pond, where it is monitored for long-term for potential contamination to the soil and ground water. Rare-earth and prelanthanide wastes often end up in the pond where they are diluted and irretrievably lost for further use or recycle. Certain parts of the world the chloride process wastes are pumped via deep boreholes into porous geological strata. The present techniques of disposal are not only expensive but also pose continued threat groundwater and soil and marine life in case of sulphate waste [1, 2]."

Jan 1, 2009

By Pan Gu, Zhen Zhang, Jiang Diao, Bing Xie, Hongyi Li

Viscosities of FeO-SiO2-V2O3-CaO-P2O5 slags have been measured at the temperature range of 1673 K to 1773 K (1400°C to 1500°C). This investigated system represents the major components of basic vanadium slag that is an important intermediate product of a novel vanadium extracting process, in which removal of phosphorus and extraction of vanadium can be achieved from the vanadium-containing hot metal simultaneously. It was found that higher CaO/SiO2 ratio resulted in lower viscosity in the composition range of interest. Also, the viscosities increase with the increasing P2O5 concentration. The varying viscosities can be attributed to the modification in complexity and polymerization of the slag network. The variation of apparent activation energies are in tune with the viscosity measurements. The results of this work revealed the effect of CaO/SiO2 and P2O5 on the viscous properties of FeO-SiO2- V2O3-CaO-P2O5 slags and therefore provide the theoretical foundation for the control of the coupling de-P and V-extraction process.

Jan 1, 2016

By Joo Hyun Park, Soo Sang Park

The distribution behavior of Pb between molten copper and FetO-SiO2 (-CaO, Al2O3) slags was investigated at 1473 K (1200 oC) and p(O2)=10-10 atm in view of the reaction mechanism of Pb dissolution into the slag. The distribution ratio of Pb (LPb) decreases with increasing CaO content (~6 mass pct) irrespective of Fe/SiO2 ratio (1.4~1.7). However, the addition of alumina into a slag with Fe/SiO2=1.5 linearly decreases the LPb, whereas a minimum value is observed at about 4 mass pct Al2O3 at Fe/SiO2=1.3. The log LPb continuously decreases with increasing Fe/SiO2 ratio, and the addition of Al2O3 (5 to 15 mass pct) into the silica-saturated iron silicate slag (Fe/SiO2 < 1.0) yields the highest Pb distribution ratio. The log LPb linearly decreases by increasing the log (Fe3+/Fe2+) value. The Pb distribution ratio increases and the excess free energy of PbO decreases with increasing Cu2O content in the slag. However, from the viewpoint of copper loss into the slag, the silica-saturated system containing small amounts of alumina is strongly recommended to stabilize PbO in the slag phase at a low Cu2O content.

Jan 1, 2014

By Dong-dong Liu, Jian-ping Niu, Qi Liu, Shu-sen Cheng

A numerical model was developed to simulate the three-dimensional heat transfer in the belly and lower shaft region of the blast furnace wall consisting of copper steel composite stave, packing and shell. The temperature distribution of copper steel composite stave without the slag layer or refractory lining was investigated and then compared with the copper stave. The results showed that copper steel composite stave can satisfy the requirement of overheatingfree and had an analogous heat transfer behavior as copper stave but more stable cooling intensity. This model had been validated by the good agreement between the computed and measured temperature in the thermal test.

Jan 1, 2015

By O. Ryosuke Suzuki

A new metallurgical process via sulfide is proposed: a sulfide is produced at a high temperature from its metallic oxide using gaseous CS2, and this sulfide is electrochemically reduced to its metallic state using molten salt. This combined process via sulfide is effective to obtain high purity of metallic powder, even if the metal in its oxide is strongly combined with oxygen. For example, it is not easy to reduce stable oxide TiO2, and only Ca can remove oxygen to form α-Ti. However, a fairly large amount of oxygen remains as Ti–O solid solution. Because the solubility of S in Ti is very small, this proposal was examined experimentally both on the conversion of TiO2 to TiS2 and on the successive reduction of TiS2 to Ti. TiO2 powder was exposed to CS2 gas flow at 1073 K, and the conversion to TiS2 was confirmed. TiS2 could be reduced to Ti powder either by calciothermic reduction or electrolysis in a CaCl2 melt. By Ca reduction at 1133 K in CaCl2 melt, sulfur concentration decreased to 0.03 mass%S when the amount greater than twice the stoichiometric calcium amount is added. By electrochemical reduction at 1173 K in CaCl2–CaS melt, S concentration significantly decreased to 0.01 mass% S when four times larger amount of electric charge was supplied.

By Cui Wang, Kexin Jiao, Qiuye Cai, Jianliang Zhang

Prolonging the campaign life of the blast furnace has been an important task for iron makers, and it has been studied for decades. Adding titanium-bearing materials is a generally agreed and effective technique to protect the blast furnace hearth. Titanium from titania additions in the burden or tuyere injection react with carbon and nitrogen and form scaffolds on the hearth surface to protect the hearth from subsequent erosion. In this article, the progress on blast furnace hearth protection of titania additions in Chinese steel companies and research institutions is investigated, and the difficulties in the operation and production, such as little effect after adding titaniumbearing materials and the property deterioration of liquid iron and slags, are analyzed. The future research for protection in Chinese blast furnace is proposed, and a comprehensive process which combines protection of titanium bearing materials with reasonable thermal balance and slagmaking regimes should be established.

Jan 1, 2015

By W. F. Miao

Nanocrystalline mixtures of Nd2Fe14B and a-Fe have been synthesized by mechanical milling and heat treatment. The samples exhibit isotropic behavior, with significant remanence enhancement associated with exchange coupling across the interfaces of hard and soft magnetic phases. Measurements of the effect of heat treatment on structure and magnetic behavior demonstrate the important influence of grain size on magnetic properties. The effect of alloy additions to increase the saturation magnetization of the soft phase and the magnetocrystalline anisotropy of the hard phase has also been investigated.

Jan 1, 1997

By Elli Nurminen

Sulphate decomposition was studied in the conditions of a typical copper flash smelting heat recovery boiler. The aim was to determine the kinetics of the copper sulphate decomposition reactions and to find out if they are likely to take place in the process conditions prevailing in an industrial HRB. The information is essential in CFD-modelling of the reactions taking place in the boiler and for optimising the process. Thermal decomposition of sulphates was studied by thermogravimetry. The experiments were conducted with a commercial copper sulphate, a partially sulphated copper oxide and an actual process flue dust. The main variables studied were temperature and gas composition of a N2-O2-SO2-mixture. The samples were characterized with SEM, optical microscope and XRD. Temperature affected the decomposition rate strongly but the gas composition had a minor effect on the kinetics. The decomposition was fastest in the partly sulphated oxide and slowest in commercial copper sulphate. Keywords: Sulphate decomposition, flash smelting, heat recovery boiler, flue dust

Jan 1, 2004

By Ricardo Badilla-Ohlbaum

Copper has been used by man for a very long time and unlike certain other metals, it is an essential element for life. Its toxicity arises both from a deficit and excess copper exposure/intake. The focus of the current discussions in countries of the European Union (EU) and in some USA States, is based on the concerns, independent of the scientific facts and the economic status of these claims, of the negative influence of copper and other metals on health and the environment. These discussions have influenced the new regulations of copper in drinking water, and the approach to regulate the appropriate levels of copper in surface water, soils and sediments. To illustrate the challenges ahead for copper, the evidence by which the current US Environmental Protection Agency (USEPA), the World Health Organization (WHO) and EU recommendation and regulations regarding copper in drinking water have been derived is presented and discussed. The gaps between the demands for new standards of health and the environment and the practical scientific tools to achieve these goals are presented, and the need to develop new regulating paradigms is also illustrated. The introduction of methodologies for the regulation of essential elements and acute inorganic substances in drinking water is discussed, as well as the status of the present approach contained in the International Program of Chemical Safety Environmental Health Criteria, (EHC) N° 170. The impact of the possible restrictions on the use of copper in the EU because of health and environmental concerns in terms of the world market for copper is discussed.

Jan 1, 1999

By A. E. Wraith

The tuyère flow rates of Peirce-Smith converters and bath smelting reactors are rendered particularly sensitive to accretion formation, bath depth variations and the general aerodynamic design of the blast delivery system by the limited pressure-flow properties of the conventional single stage centrifugal blower. This sensitivity is examined in terms of tuyère practice, vessel management and fixed engineering parameters for Peirce-Smith converters and the Noranda Reactor by use of the flow resistance factor, R*. New understanding of the effect of accretion growth on the flow behaviour of individual tuyères shows that blowing rates and hence throughputs could be optimised by careful attention to operating detail even within present plant constraints. The concept of the resistance vector is introduced to elucidate comparisons between different practices and to provide reference standards for optimisation. On this basis, the benefits of introducing quite moderate changes in the pressure-flow properties of the blast delivery system are considered. In view of recent developments in the flexible use of converters as hybrid bath smelting vessels for matte production, the foundation is now laid for a searching consideration of relationships between vessel volume and shape, blowing requirements, tuyère performance and production rates, the detail of which will be examined more appropriately in a forthcoming paper.

Jan 1, 1999

By Jie Li, Thomas A. Rawdanowicz, W. J. Collis, S. Venkatraman, S. Iyer

"InSb being the lowest band gap. material amongst the 111-V semiconductors with low effective mass has long attracted research interest, due to its potential application in far infrared devices and for high speed circuit elements. In this paper, we report, for the first time, Te-doping of InSb on GaAs substrate using SnTe doping source with molecular beam epitaxy (MBE) technique and its electrical characterization. The undoped epilayers are n-type in the temperature range of 10 K to 300 K investigated. The room temperature (RT) mobility as high as 64,810 cm2/V·s (1.9x1016 cm-3) have been measured on a 4.8 µm thick epilayer. Sn Te doping at different doping levels were investigated. 5. 7 µm thick doped layers with RT carrier concentrations ranging from 2x1016 cm-3 to 3.2x1018 cm-3 with corresponding full width at half maximum (FWHM) of x-ray (400) rocking curve varying from 170-200 arc-seconds have been achieved. The Hall mobility of 20,000 cm2/V·s at 1.3xl018 cm-3 carrier concentration was obtained indicating that SnTe is a good candidate as source material for n-type doping of InSb.IntroductionThe thin films of InSb and InSb-based alloys have found considerable interest because of potential applications in III-V semiconductor-based infrared optoelectronic devices1• In addition, the advantage of the small effective mass and the consequent high mobility can be utilized in high frequency and high-speed circuit devices2 InSb can also be used in magnetoresistive sensors for position sensing3. Epitaxial InSb films grown by MBE may be doped n-type with Si or Sn, or with the group VI elements, namely, S, Se, or Te. Of the group VI elements, Te may be advantageous because of its relatively low vapor pressure. However, the vapor pressure is high enough to have sufficient memory effect during MBE growth. Hence different telluride compounds such as GaTe45, PbTe6 and Sb2Te37 have been used as the dopant source for Sb-based compounds. SnTe has also been used as a successful n-type dopant in the MBE growth ofGaSb8 But, to our knowledge, there is no report on the investigation of SnTe doping of InSb. In this paper, we report the first doping characteristics of SnTe in InSb layers grown on GaAs substrate."

Jan 1, 1998

By Akihide Nagao

The behavior of impurity hydrogen that is contained in starting material or picked up during processing has been little investigated up to now. The hydrogen microprint technique is applied to determine the microscopic location of impurity hydrogen during deformation in aluminum without hydrogen charging. Three kinds of pure aluminum of 99.99% are prepared, in which hydrogen content is varied by changing the atmosphere when they are melted and heat-treated. After rolling, tensile specimens with a gage size of 4 x 4 rnm and 0.5 mm in thickness are stamped out from these three kinds of aluminum sheets. These specimens are covered with a liquid nuclear emulsion of silver bromide crystals, stretched by 5,10 and 15 percent plastic strain or fractured, developed and fixed. SEM micrographs reveal a number of silver particles on the slip lines and on the grain boundaries. Also shown is that the more hydrogen present in the specimen, the more silver grains appear on the slip limes and on the grain boundaries. Consequently, it is concluded that impurity hydrogen is transported to the surface with gliding dislocations during deformation.

Jan 1, 1998

By Zhihe Dou, Zimu Zhang, Guozhi Lv, Yan Liu, Xiaoli Jiang

"Cyclic heat stewed slag washing water carries high content of alkali and calcium and may cause serious tube scaling and impose an adverse impact on normal production. This study proposes a solution to utilize washing water by absorbing and mineralizing CO2, potentially restraining scaling and being able to create calcium carbonate powders. Effects of water flux on water quality, utilization ratio of CO2 and yield of calcium carbonate powder have been investigated; meanwhile, features of calcium carbonate powder are also represented. On the other hand, effects of factors such as as injection flux, pressure of CO2 on utilization ratio of CO2, morphology and purity of calcium carbonate are also investigated. The results show unambiguously that after soften injection of CO2, calcium ions were removed effectively via precipitation, alleviating the scaling problem. High purity yet fine carbonate powder could be achieved.IntroductionNowadays, 0.34 tons of blast furnace slags will be produced when producing 1 ton of pig iron; ensuing that, 0.12 tons of steel slag will be generated with 1 ton steel production while 1.57 billion tons of steel output all over the world in the year of 2012. It is therefore a critical issue to realize zero discharge of steel slags to achieve sustainable development and cyclic economy of iron and steel industry. In recent years, research institute of MCC and China JINGYE engineering company developed a heat stewed steel slag self-decomposition technology GENERATION III to solve the problem of instability of steel slags and realize the zero discharge. However, the problem of circulation line scaling which may cause the clogging, even exploding, need to be solved. The principles of the technology are: directly spraying water to the high temperature steel slag when it is poured into the hot closed pot, realizing the selfdecomposition via utilizing the waste heat of steel slag. The washing water is recycled to achieve a cyclic utilization. The process is shown in Figure 1."

Jan 1, 2014

By K. J. Murphy, A. R. Smith, A. P. Odorski

"The need for large quantities of oxygen for use in metallurgical processes was a major driving force in the commercialization of tonnage air separation plants. Oxygen, nitrogen and argon impact the quality, energy efficiency and environmental aspects of metals production. Cryogenic air separation processes have been used to supply most industrial requirements, however, newer technologies are available or under development to meet the needs of today's and tomorrow's metallurgical processes. This paper reviews the technical features and state of development of adsorption, chemical, cryogenic and membrane technologies. The technologies are compared in terms of plant size, oxygen purity and pressure, nitrogen and argon co-production, product use pattern and back-up requirements. Computer control systems are described that optimize operation over varying load patterns and ambient conditions; substantially lowering energy consumption. IntroductionOxygen production totalled 390 billion cubic feet in 1987. Although current production is lower than the peak of 455 billion cubic feet reached in 1979, oxygen remains the fifth leading chemical product manufactured in the u.s. (1) Metals manufacturing and fabrication accounts for sixty percent of the oxygen consumed in the u.s. Oxygen use in the steel industry consists of air enrichment for conversion of iron ore, purification of the iron in basic oxygen or other furnaces, and for cutting and welding the finished steel product. Nonferrous ores are smelted in oxygen enriched atmospheres to reduce energy consumption and increase capture of sulfur compounds to meet environmental requirements. In the future oxygen usage is expected to become even more important in metals production as energy costs increase, environmental standards become more stringent, and as new coal based processes become commercialized. Oxygen usage per ton of metal in the new direct reduction processes can be up to ten times higher than traditional steel making."

Jan 1, 1988

By Ben Q. Li

An efficient numerical algorithm for solving steady state heat transfer and solidification problems is described. The algorithm is of boundary integral type and is based on the formulation of the field variables along the boundary of the domain of interest. Compared with the familiar domain-based methods, such as the finite element and finite difference (or finite volume) methods, this boundary-based method has an advantage of solving fewer unknowns and hence has a potential for reducing computational time significantly. Another and yet more important advantage of the present algorithm is that it is a stable scheme and is not prone to numerical oscillations resulting from convective effects, as often encountered in the domain-based methods. Therefore, no numerical or artificial diffusion (such as streamline upwinding) is necessary. Numerical examples are presented that are drawn from processing systems for producing aluminum-based materials.

Jan 1, 1994

By F. G. Prado

The technology for the extraction of zinc from zinc residues, such as zinc ashes, drosses and metallurgical flue dusts, by way of ammonium chloride solutions is well established, at least at the laboratory and bench scale levels. (3, 4) Zinc is soluble in ammonium chloride solutions in the form of zinc diammine chloride. Its solubility depends upon the concentrations and temperatures employed. The procedure and the equipment required are simple, and they can be applied either to small or large operations. As a by-product, zinc diammine chloride is produced with extremely low impurities in quantities which are stoichiometrically proportional to the zinc removed. The technology has been applied experimentally to galvanized steel residues. The dezincing results, including removal performance, energy and reagents required, and by-products are summarily presented in this paper.

Jan 1, 1992

By Wenbo Luo, Kang Liu, Fusheng Mao, Jilai Xue, Jun Zhu, Chunlei Yang

Extracting alumina from coal fly ash (CFA) is of great interest for both environmental protection and recycling valuable alumina content. In this study, ultrasonic aided leaching process as an effective method was investigated to enhance extracting Al2O3 from CFA via concentrated sulfuric acid sintering. The influence of ultrasonic power and processing time were tested under the conditions as the same as those without ultrasound. It is found that the alumina extraction rate can reach 90.5 % with ultrasound assistance, while the ultrasonic treatment can reduce almost 15 ~ 30 min in leaching time and 5 ~ 10 oC in leaching temperature than those without ultrasonic operation at the same Al2O3 extraction rate. In addition, the ultrasonic can reduce calcium content by 6 ~ 8 % dissolved into the leaching liquid. SEM analysis also shows that the residue particle size with ultrasound is smaller than that without ultrasonic treatment.

Jan 1, 2015

By Bruno Augusto Batista Ribeiro, Felipe Terra Elias, Wagner Moulin Silva

In the pyrometallurgical production of copper from its sulfides, converting in the Peirce Smith (P-S) Converter is still the most widespread method to obtain white metal and blister copper from the matte. Despite the fact of being a century-old process, it is still possible to achieve improvements in the process, by the use of modern tools, one of the most valuable being numerical calculation and computer-aided simulation. The present study presents three cases in which the angle for the gas injection and the number of working tuyeres are changed during the slag blow phase of the converting process. It was noticed that a decrease of the number of tuyeres, followed by an increase in the injection gas velocity, results in improved reaction volume and less stress to the refractory lining. However, an increase in the amount of copper lost to the slag as oxide is likely to occur.

Jan 1, 2014

By Jing Zhan, Gui Li, Wei-feng Li, Li-Hua Jiang, Chuan-fu Zhang, Jian-yang Hwang

Thermodynamics analysis for processing the charge with lead concentrate and lead sulfate-containing materials in bottom blowing smelting furnace was conducted. The results show that the technology of large-scale processing PbSO4- containing materials with PbS concentrate in bottom blowing furnace under the condition of using high-iron slag type, batch heat supplement, high temperature and rich oxygen is thermodynamically feasible. The exploration test and industrial experiment confirm the results. When S content in mixed ore is 16~17% with coke foam content of about 5%, the lead paste amount can be increased up to 40%.

Jan 1, 2015

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