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By R. G. Reddy

The Margules .equation is used for interpreting excess Gibbs energy of several ternary systems. In the present study activity coefficient of 'a dilute solute, 2, in a binary solvent 1-3 was derived. The derived expression is used to interpret logarithmic activity coefficient of oxygen and sulfur in several metallic systems. Self interaction parameter of the solute is derived from the partial function of solute using constant compositional path. An expression for logarithmic activity coefficient and self - interaction parameter of solute is also derived using Maclaurin infinite series. The derived equation is based on Maclaurin infinite series used successfully to deduce thermodynamics of self interaction of oxygen as a interstitial atom in two metallic systems. The predicted thermodynamic parameters values using Maclaurin infinite series and Margules. equations, are in excellent agreement with the experimental data and also our predictions are far more accurate than the predictions made by other models.

Jan 1, 1996

By P. D. Navarro

The behavior and operability of LIX 1104SM extraction was studied at laboratory scale on the Solvent Extraction at Sb3+, from high concentration sulfuric acid. In order to evaluate the reactant batch tests were made at laboratory scale as well for extraction as for re-extraction of Sb3+. Experiences achieved were: extraction kinetics, temperature effects, selectivity tests and re-extraction selectivity. A extraction kinetics was found, reaching equilibrium in 2 min, high selectivity of Sb3+ extraction in front of Cue , existing As5+ co-extraction and Fe3+ At the re-extraction stage, equilibrium was reached in 3 min, getting high Sb3+ re-extraction efficiency with HCl concentrations within 6 and 8 M. A high selectivity was achieved on Sb3+ re-extraction in front of As+5, existing Fe+5 re-extraction.

Jan 1, 1999

By Harsh Deep Chopra, Jason N. Armstrong, Susan Z. Hua

"Existence of anisotropic Curie temperature materials [E. R. Callen, Phys. Rev. 124, 1373 (1961); J. Appl. Phys. 32 S221 (1961)] is a longstanding prediction - materials that become paramagnetic at a lower temperature along certain crystal directions while remaining magnetically ordered in other directions up to a higher temperature. Validating Callen's theory, we show that all directions within the basal plane of monoclinic F e1Ss (pyrrhotite) single crystal remain ordered up to 603 K while the c-axis becomes paramagnetic at 225 K. Results prompt a re-evaluation of existing magnetic materials with a focus on magnetic characteristics along different crystal orientations above instead of below the ordering temperatures. Theoretical guidelines for identifying new materials with large anisotropy of Curie temperature are also given, and analysis protocol to characterize them in a self-consistent manner is discussed. Materials with such a large directional dependence of Curie temperature open the possibility for uniquely new devices and phenomena, including energy storage and spintronics devices.IntroductionThis paper is an overview of our recently published work on anisotropic Curie temperature materials [l]. As a background, ferromagnetic and ferrimagnetic materials are characterized by a critical temperature below which magnetic interactions prevail over thermal agitation, leading to the appearance of a spontaneous magnetization. Above this critical point, called the Curie temperature, thermal energy eventually overcomes magnetic interactions and the material becomes paramagnetic.It is less well known that the Curie temperature varies with the orientation of the crystal. In ordinary ferromagnets this orientation dependence of Curie temperature is negligible because of the vanishingly small ratio of anisotropy to exchange energy, i.e., the spherical or isotropic exchange term dominates. Thus Curie temperature in ordinary ferromagnets appears to be an isotropic property, and assigning it a single characteristic ordering temperature suffices. However, a 'small' difference is not equivalent to being the 'same', and under appropriate set of conditions the anisotropy of Curie temperature is predicted to become appreciable, as discussed in the following.In formulating the theory of 'anisotropic magnetization' [2, 3] E. R. Callen and H. B. Callen first discussed the ""interesting possibility"" of anisotropic Curie temperature [2] or ACT; Callen and Callen noted that it was W. J. Carr, Jr. who initially raised this question, and they discussed it in detail at the Conference on Magnetism and Magnetic Materials (NY, November 1960), see footnote on page 320 of Ref. [2]. Soon thereafter, E. R. Callen developed the theory underlying the anisotropy of Curie temperature and conditions conducive to its observation [4, 5]."

Jan 1, 2013

By Boxun Lu, Juan Wei, Kun Chen, Wanlin Wang, Lejun Zhou

"Slag system is an indispensable part during the continuous casting process, and playing various important roles like absorbing inclusions, modifying heat transfer rate, preventing oxidation of molten steel, etc. to ensure the smooth process and excellent slab quality. However most slags contains more than 8% fluorides which tend to introduce a series of environmental and health problems. This study involves the research of the removal of fluorine through the chemical composition optimization. Through the studies of CCT, DHTT, XRD and SEM, it has been successfully founded that the crystalline phase of Ca11Si4B2O22 discovered in this study shows very similar crystallization property as Cuspidine (Ca4Si2O7F2), which is the most important crystalline phase in the current fluorine bearing slags. Moreover, the optimized free/low fluorine slag shows the opportunity to replace conventional high-fluorine mold slag for casting medium carbon steels that is regarded as the bottleneck of green slag development for continuous casting.IntroductionMold flux has been widely used in continuous casting to control heat transfer, lubricate the strand, absorb inclusions, provide insulation and prevent oxidation of the molten steel[1-3]. It usually contains fluorides, like CaF2, NaF etc., which are used to control the viscosity and solidification temperature of mold fluxes [4-5]. However, the presence of fluoride leads to corrosion of equipment, serious environmental pollution (toxic volatiles and water pollution), and high processing cost of cooling water[6-7]. Therefore, the study of low or free fluorine mold flux is of interest and attracts worldwide attention.S. Y. Choi et al. [4] used B2O3 as a substitute for cuspidine in steel B2PB2) however, B2O3 content was extremely high (up to 30 w%). Other studies have investigated F-free mold flux by adding or optimizing components as MgO, Li2O, B2O3 et al[8-11]. However, most of these focused on the melting and viscosity issues or for low or ultra-low carbon steels, where crystallization tendency is not significantly strong. Very few studies regarding to the development of low/free Fluorine mold flux for casting medium carbon (MC) steels have been conducted, due to the difficulty of the crystallization and heat transfer control without the formation of cuspidine."

Jan 1, 2014

By M. Nilmani, J. Sofra

The transverse distributions of the solids discharge velocity and mass flux at the discharge end of vertical and inclined lances were measured in order to detennine the transverse distributions of the axial momentum flux, which is a dominant factor influencing the penetration behaviour of particles into melts during submerged injection. The effects of gas velocity (10 - 30 m/s), solids loading (5 - 10), lance length (0.15 - 1.0 m), lance inclination (vertical downward - horizontal) and particle density (2500 - 8900 kg/m3 ) were investigated, while the lance diameter and particle size were fixed at 10 mm and 220 µm respectively. The particle velocities and mass fluxes were measured by image analysis of particles illuminated in a laser-generated light sheet aligned vertically through the axis of the lance at the discharge point. The particle discharge velocity profiles for vertical downward flows were synunetrical about the centre-line of the lance, with the maximum velocities occurring at the centre-line. The velocities increased with increasing gas velocity, increasing lance length and decreasing particle density in accordance with previous observations. The transverse mass flux profiles were also synunetrical for vertical downward flows, however at the lower gas velocities the peaks in the profiles were displaced from the centre-line of the lance by a fractional diameter of about 0.15. The particle discharge velocity profiles become increasingly asynunetric as the lance orientation was changed from vertical to horizontal, with higher particle velocities present near the top wall of the lance. The mass flux profile also became asyrrunetric as the horizontal orientation was approached, however in this case, the profile became biased towards the bottom of the lance. The effect was much more pronounced for a gas velocity of 10 m/s than for 30 m/s, showing the relatively stronger gravitational influence as the velocity was reduced.

Jan 1, 1996

By J. P. Evans

The modem 'copper smelter today utilizes tonnage oxygen for smelting concentrates. ,generating a high strength S02 off-gas leaving the smelter vessel. This gas stream. which also contains any unreacted oxygen, plus CO2; N2 and H20. also carries with it the volatilized portion of heavy metals in the feed, plus partly oxidized sulfide concentrates, The time/temperature history and subsequent treatment of this off-gas stream emerging from the smelting furnace exit up to the acid plant can influence the partitioning and segregation of heavy metals, in the off-gas circuit. Depending on this history. the type and characteristics of the chemical and physical reactions which occur in the gas handling system 'can be influenced. This fact can also be used as a tool to adjust the separation of copper from heavy metals. In this paper, the impact of different time/temperature histories of the gas, due to different furnace geometries and design. on the subsequent formation and characteristics of the smelter dust is examined. Based on the available data. several case histories drawn from examples using both bath and flash smelting technologies are analyzed from this perspective.

Jan 1, 1992

By J. P. Evans

The modem copper smelter today utilizes tonnage oxygen for smelting concentrates, generating a high strength S02 off-gas leaving the smelter vessel. This gas stream, which also contains any unreacted oxygen, plus C02, N2 and H20, also carries with it the volatilized portion of heavy metals in the feed, plus partly oxidized sulfide concentrates. The time/temperature history and subsequent treatment of this off-gas stream emerging from the smelting furnace exit up to the acid plant can influence the partitioning and segregation of heavy metals in the off-gas circuit. Depending on this history, the type and characteristics of the chemical and physical reactions which. occur in the gas handling system can be influenced. This fact can also be used as a tool to adjust the separation of copper from heavy metals. In this paper, the impact of different time/temperature histories of the gas, due to different furnace geometries .and design, on the subsequent formation and characteristics of the smelter dust is examined. Based on the available data, several case histories drawn from examples using both bath and flash smelting technologies are analyzed from this perspective.

Jan 1, 1992

By Wayne C. Stewart

Freezing of high pressure air lines and pneumatic equipment has been a recurring problem in the Thompson Smelter. The particular severity during the winter of 1989-90 resulted in costly process disruptions and repairs. A process improvement team with representatives from operations, engineering and both maintenance supervision and the shop floor was established to develop solutions. Their mandate included process evaluation, design, equipment and in-plant commissioning. In 1990, upon recommendation of the team, we installed three Refrigerant/Desiccant air dryers with a total capacity of 20,000 S.C.F.M. to service the Smelter. This paper discusses processes and process improvements associated with this installation.

Jan 1, 1993

The oxidation of zinc vapour plays a very important part in the operation of the Imperial Smelting Process. The kinetics of the reoxidation of zinc vapour by carbon dioxide and water vapour onto quartz and zinc oxide substrates is qualitatively understood and this pertains to the conditions found as the gases are being transferred from the furnace to the splash condenser. However, re-oxidation also occurs in the shaft of the furnace where the solid substrates are sinter and metallurgical coke. It was found that there was a threefold increase in the rate of oxidation on sinter, compared to quartz and a 30 to 300 increase in rate on the coke. This was attributed to the high surface area offered by these materials.

Jan 1, 2003

By Markus A. Reuter

In this paper, the kinetics of phosphorous production in submerged-arc furnaces will be discussed as a function of temperature, as well as various ore and reductant types. Interesting positive synergetic effects on the rate of reaction could be observed when mixing different types of ores. The results will be discussed with reference to a kinetic model, microprobe analyses, etc. The effects these results have on the control of the furnace will also be discussed in detail, indicating how these could be incorporated into the electrode and metallurgical control systems for submerged arc-furnaces.

Jan 1, 2000

By Kimberly Conner-Mills

Due to increasingly stringent worldwide environmental regulations for gaseous, aqueous and solid waste emissions, conventional smelting technology cannot effectively process arsenic containing materials. Many globally significant copper properties have copper sulfide mineralogy that has a high arsenic content present as enargite with significant contained precious metals. As global copper, silver and gold demand increases while significant world resources decrease, treatment of sulfide orebodies with enargite is becoming increasingly important. Methods to selectively dissolve and fix arsenic, leaving behind clean copper and precious metals-bearing concentrates could effectively treat these ores.

By C. Dresen

This paper discussed the reaction kinetics of the reduction of industrial phosphate pellets for P4 production. In the reduction process of various phosphate ores, the following parameters were investigated: Diffusion of the phosphorus oxide and other gaseous products from the reaction mixture after having been reduced on the reductant (coke) surface. Influence of silica on reaction kinetics. Temperature influence. Influence of mineralogy and morphology (different ores). Particle size influence of silica and coke. Experiments were carried out in a vertical tube furnace with 2 ores, 2 types of silica and one type of coke. Selected experimental conditions simulated furnace conditions. The following conclusions could be made: Reaction rate increases with the addition of SiO2 into the pellet. The reaction rate increases above 1350°C (melting temperature of the slag). Mixing different ore types in the pellets leads to differences in reduction kinetics. Particle size of the coke particles influence reduction kinetics. The amount of slag formation is influenced by silica addition, coke size and temperature.

Jan 1, 2002

By Corby G. Anderson

Today, with a stringent economic and environmental climate prevailing in the copper business, there is increased interest in evaluating new processing alternatives for production. Hydrometallurgical pressure oxidation of copper concentrates is one of the more viable approaches and several technological candidates have emerged. Of these, an overlooked but, ironically the first industrially proven methodology, utilized nitrogen species catalyzation in the oxidizing pressure leach system to produce copper via SX!EW. Given its many inherent process advantages, this may prove to be a feasible process alternative for the future. In this paper, the history of the system and its application to chalcopyrite concentrates will be outlined. In particular, a novel methodology for effective recovery of precious metals from chalcopyrite concentrates will be discussed. Finally, the perceived economics of this unique industrially proven process will be delineated.

Jan 1, 2000

By Minjun Tang, Jianfeng Zhou, Linjiang Qing, Yufeng Guo, Tao Jiang

"For the comprehensive recovery ofV, Ti, Fe in vanadium-titanium magnetite in the process of pre-reduction-electric furnace smelting, it is expected that vanadium oxide is reduced into molten iron and titanium oxide is available in the slag. Thus the effect of slag basicity, the content of MgO, MnO and CaF 2 of slag content on the separation of slag and molten iron and the comprehensive recovery of V, Ti, Fe were investigated. The results show that increasing slag basicity, MgO, MnO and CaF2 are all beneficial to the separation of slag and molten iron. Higher slag basicity and the addition of CaF2 strengthen the reduction of vanadium oxide, and inhibite the reduction of titanium oxide, which are in favour of the recovery ofV and Ti. However, the addition ofMgO, MnO was not efficient for the comprehensive recovery ofV, Ti, Fe. For the vanadium-titanium magnetite of Panxi in China, the recovery of Fe was over 98%, the recovery ofV in molten iron was over 85% and the Ti02 content in slag was about 43% under the optimal conditions of slag phase type.IntroductionIt is well known that there are abundant vanadium-titanium magnetite resources which are located in Panzhihua of Sichuan Province[!]. At present the vananium-titanium magnetite concentrates are smelted in the blast furnace, which just make use of iron and vanadium, but lots of titanium is discarded in the slag. At the same time, the process has a large number of disadvantages, such as low recovery of vanadium, long route, pollutions, large investment and expenditure of energy[2-3]. In recent years, in order to efficiently utilize the vanadium-titanium magnetite concentrates, several new non-blast furnace processes have been proposed, such as pre-reduction-electric furnace, pre-reduction-grinding separation and so on[4]. Especially pre-reduction-electric furnace is operating well in South Africa and New Zealand,However,Du to the high slag basicity of the slag, the grade ofTi02 of slag is Corresponding author:Minjun Tang.E-mail:450435123@qq.com. Tel:13627429224."

Jan 1, 2013

By Jie Li, Zhongliang Tian, Xun Hu, Kai Zhang, Yanqing Lai, Hongliang Zhang

The Al-Sc Alloys show many advanced properties for a wide range of engineering applications. But the metal Sc must be added into the metal Al in the form of the Al-Sc master alloy, which is usually produced by the thermal reduction process. In this paper, the decomposition voltages of Sc2O3 and Al2O3 in Na3AlF6-K3AlF6-AlF3 melt were calculated based on the Nernst equation. And the Al-Sc master alloy was prepared in the melt at 950°C by electrolysis. The results show that the Al-Sc master alloy can be prepared by the co-deposition of Sc3+ and Al3+ at the cathode if the concentration ratio of Sc2O3 to Al2O3 in the melt is more than 2:1 under the condition of the aluminum electrolysis. SEM and ICP analysis of the product indicates that the Al-Sc master alloy is made of the phase Al and the phase Al3Sc.

Jan 1, 2016

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 T. T. Chen

Gold in the Twin Creeks ore is primarily associated with arsenian pyrite. During pressure oxidation, the sulphides are solubilized, but part of the dissolved iron reprecipitates as jarosite and as an iron sulphate-arsenate-phosphate phase. The pressure oxidation products are subjected to cyanide leaching. The cyanide leach residues consist of quartz, gypsum, bassanite, anhydrite, small amounts of jarosite, an iron-sulphate-arsenate-phosphate phase, as well as trace amounts of orthoclase, rutile, pyrite, hematite and monazite; all these particles are dispersed in a fine grained matrix of illite-muscovite. The autoclave leach residues contain a small amount of carbonaceous matter. Many gold grains are detected on the surfaces of the carbon particles, and these gold particles are not leached during cyanidation. The gold particles are typically 0.1-0.2/Lm in size and commonly are embedded in the carbon surface or are coated with a K-AI-Si-S-O phase on the surface of the carbon. The gold grains are consistently associated with elevated CI contents (50-300 ppm Cl). The poor gold cyanide leach recoveries, which initially occurred in the Twin Creek developmental circuit under certain operating conditions, are attributed to the presence of chloride in the feed. This results in the formation of soluble gold chlorocomplexes in the autolcave and the subsequent sequestering of the gold on the surfaces of the carbon particles.

Jan 1, 2000

By B. C. Blakey

The economic feasibility of the sulphuric acid pressure leaching route for the extraction of nickel and cobalt values from limonitic ores is highly dependent upon the behavior of aqueous aluminium. This is primarily due to its precipitation as hydronium alunite ((H30)A13(S04)2(OH)6), which is one of the major scale-forming compounds found in autoclaves used for pressure leaching. As a result of renewed interest in the pressure leaching process, an investigation of the aqueous-solid eqilibria in the aluminium-sulphate-water system under acidic (< pH l), high temperature (230 to 270°C) conditions has been conducted. Pure hydronium alunite was synthesized in an autoclave by leaching boehmite (A100H) at elevated temperatures in sulphuric acid solutions initially 0.25 to 0.75 m H2S04 in concentration. Spontaneous, in situ precipitation of hydronium alunite followed. A high temperature solution speciation model was used for the analysis of the resulting solubility data in order to calculate equilibrium constants for the precipitation reaction.

Jan 1, 1994

By James E. Simpson, Suresh V. Garimella, III de Groh

"An experimental and numerical study of the horizontal Bridgman growth of pure succinonitrile (SCN) and of a succinonitrile-1.0 mol. % acetone alloy (SCN-1.0 mol. % ACE) has been performed. Experiments at growth rates of 0, 2 and 40 µmis were investigated. The solid/liquid interface was stable (non-dendritic and non-cellular); however, it was not flat. Rather, it was significantly distorted by the influence of convection in the melt and, for the growth cases, by the moving temperature boundary conditions along the ampoule. For the alloy, the interface was determined to be unstable at growth rates greater than 2.8 µmis, but stable for the no-growth and 2 µmis growth cases. When compared to the pure SCN interface, the alloy interface forms closer to the cold zone,· indicating that the melting temperature has been suppressed by the addition of the alloying element. Two-dimensional computer simulations were performed for the no-growth case for both the pure and alloy materials. These simulations indicate that a primary longitudinal convective cell is formed in the melt. The maximum magnitude of velocity was calculated to be 1.515 mmls for pure SCN and 1. 724 mm/s for the alloy. The interface shape predicted by the computer simulation agrees well with the experimentally determined shape for the pure SCN case. In ongoing work, numerical simulations of the process during growth conditions are being performed.IntroductionIncreasingly, advanced materials used in the aerospace, automotive, optics and electronics fields require low levels of defects and high levels of solute uniformity. Directional solidification by the Bridgman process is widely used for synthesis of these high-quality materials. During Bridgman crystal growth, heat and mass transfer by both thermal and solutal gradient-driven convection and diffusion influence the shape of the solid/liquid interface and dopant segregation levels, and hence, directly determine the final crystal quality. Key process parameters include the applied furnace temperature distribution and rate of translation, ampoule properties and furnace orientation."

Jan 1, 1999

By G. G. Krishna Murthy

Interactions of wustite and hematite pellets with Fe-C melts were investigated experimentally by examining the effect of pellet size and bath temperature on the reduction rates of the pellets. Experiments were carried out in the temperature range 1473-1923 K. A flash X-ray equipment was used to obtain images of the melt surface during its reaction with an oxide pellet. The reduction rates were calculated using experimentally estimated time for complete reaction of a pellet, tR. The value of tR was determined employing gas mass flow rate, or pressure rise in the sealed furnace, versus time traces. The value of tR was the same for both wustite and hematite pellets of equal weight at or above 1723 K and it decreased with increasing melt temperature. But the reduction rate was substantially lower at temperatures below 1651 K, the melting point of wustite. The rates were defined as the rate of moles of oxygen removed from the pellet per unit area of bath free surface and it was found that the bath surface area affects the reduction rates. It was established that the overall reaction followed nth-order rate kinetics with the values of n falling between 0.3 and 0.4 for temperatures above the melting point of wustite. The apparent activation energy determined using the apparent rate constants obtained from the experimental data was 76.2 + 27.7 kJ/mol-O.

Jan 1, 1992