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By Carlos A. Nunes

V-AI alloys have been used commercially to produce pure vanadium by Electron Beam Melting (EBM), as well as to obtain Ti-based alloys (ex. Ti-6AI-4V). The aluminothermic reduction of vanadium pentoxide (V205) is the primary method to obtain these alloys. Concerning the obtention of pure vanadium, earlier studies have indicated alloys presenting Al content between 10 and 15wt% as the most suitable alloys for direct EBM. In the present work we investigated the aluminothermic reduction of V205 in order to define process parameters for the obtention of V-AI alloys with composition in the previously mentioned range. It was studied basically the effect of excess AI, CaO addition and reaction atmosphere (air, argon) on the alloy composition (AI, 0, N). In addition, microstructural analysis of selected alloys by SEM (BSE images) and EPMA (WDX) were also performed.

Jan 1, 1996

By Alexander I. Raitchenko

"Although one takes into account only thermal expansion usually at analysis of convection onset, the essential factors include magnetic and electric fields. If Lorentz-force originating from intercrossed electric and magnetic fields' action is directed downwards its effect strengthens gravitational action, and value of critical Rayleigh number (limit value for convection onset) must decrease; increasing of critical Rayleigh number should be observed in case of Lorentz-force directed upwards. Extent of such an influence is determined by relation of Lorentz-force to hydrostatic head in gravitational field. Competition between electromagnetic force due to nonuniformity of electroconductivity (on account of its temperature dependence) and electromagnetic buoyancy force may have ambiguous effect: both increase or decrease of critical Rayleigh numbers. Proposed conception is applicable to analysis of situations in liquid conductors and conductive gases.IntroductionStatic or dynamic situations in fluid media are determined besides properties of these media by a variety of external influences. However one correlate~ the onset of the convection and its development with influences of the minimum quantity of external causes frequently. Most known and usual factors are the gravitational and temperature fields. The number of processes includes heat generation in media volume, and theoretical analysis in these cases takes into account this interior heating together with boundary temperature conditions. But explanation of many natural and technical events is not complete and cogent within limits of thermo-gravitational terms. The whole complex of acting factors which influence convective processes in techniques and nature is greater in many cases. In particular the action of · electromagnetic nature often has not less importance than gravitation one. Stability or instability of a current layer in the plasma must be determined by non-uniformity of electroconductivity owing to non-uniformity of temperature [1]. The presence of Joule dissipation in the plasma through which the electric current flows stipulates initiation of origin of overheated instability [2]. It is known that electroconductivity of arc in the boundary zone changes sharply with radial distance [3], and this must influence its stability essentially. If the intercrossed electric current and magnetic field begin to act on an electroconductive fluid besides the non-uniform temperature field and the gravity, the conditions for the onset of the convection change radi- . cally: both the temperature field and their solutions have to be changed also. The analysis of equilibrium single-time correlation functions of fluctuations must be employed for situations with enlarged number of factors as this was in case for the Rayleigh-Benard problem where the object is a horizontal layer of liquid. This can be carried out by taking into account the detached forces' correlations [ 4, 5]"

Jan 1, 1999

By Barry J. Welch

The production of primary aluminium can potentially lead to metal that, with minimum treatment, meets a high purity standard. Smelters that can achieve a significant proportion of their production in this manner have a competitive edge which is of growing importance as the use grows for such items as compact discs and the like. Superimposed on the desire to produce high quality metal are stringent environmental requirements that the industry must adhere to. The environmental 'legislation focuses on fluoride emissions and the approach adopted is towards a zero waste management philosophy. The fluoride recycling process does, however, result in volatile impurities being captured and recycled to the cell. Aluminium has an extremely high reduction potential and this results in a significant proportion of the recycled impurities being reduced at the electrolyte metal interface and thus contaminating the metal. This paper reviews sources of impurities and the impact of the operating procedures adopted on metal treatment.

Jan 1, 1996

By Volovik A. V. Ivtan, Shelkov E. M. Ivtah

"One of the most power consumption Industrial process is production of Al from bauxites (about 45000KWt.hour electrical energy for production of 1 ton. of technical Al). This process is based at the low efficiency and productivity electrolysis technology.Last years IVTAN investigations give to .us information about possibility to use of high temperature shaft- furnaces for efficiency production of alumina (AL2O3 ) technical. aluminium and some all.oys on the base of the high temperature carbon- thermal reduction process. At this case power consumption for production of unit of last, product will be less at the 3-4 times.The carbon-thermal method is allow produce alumina (Al203 ), technical Al and its alloys not only from deficient bauxites, but practically inexhaustible reserve of other types of Al-contain row materials (cianite, sillimonite and so on/The thermal-chemical economical analises of fulfilled at the IVTAN, production of alumina. Base on facts of production and technical technology are especially for ones arguments at the high temperature shaft-furnace technical Al and its alloysIn the last decades of the 20-th century, the discharge into atmosphere of high temperature and. combustion gases places . problems before humanity more and more sharply and becomes of great importance task.But at the same time, as production of material values increases, intensity of pollution of environment increases all time. And the value of new processes and. technologies of material production, aimed at reducing the expenditure of power and pollution of· the environment, also increases."

Jan 1, 2000

By M. Girgis

The behavior of arsenic III during electrolytic refining of copper in acidic copper ?sulphate electrolytes was studied by different electrochemical methods such as, linear potential sweep, cyclic voltammetry, chronoamperometry and chronopotentiometry. The study showed that arsenic behaves as a depolarizing ion and has a deleterious effect on copper deposit. Three substrates; Pb, Cu and Ag were used during the refining process and the electrode kinetics were found similar for both Cu and Pb electrodes while a little difference was found for the Ag electrode. A microscopic study by scanning electron microscope was undertaken to show the influence of arsenic on deposit's morphology. Surface analyses of the deposit were carried out by some electronspectroscopic techniques such as Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). The results showed that arsenic coexists with copper deposit at potential?~ -0.25 V.

Jan 1, 1987

By Andrew Case

The Port Nickel facility in Braithwaite, Louisiana, is known for pioneering hydrometallurgical processes for the 'separation and recovery of nickel, cobalt and copper. Ten years ago, in 1985, a new CRI-MET process for the recovery of molybdenum, vanadium, nickel, cobalt and alumina from spent catalysts was developed and implemented. Spent- catalysts from the petroleum industry consietute the majority of feed. These are not only a valuable-source of metals, but due to EPA regulations are frequently classified as hazardous under RCRA. Molybdenum and vanadium are selectively leached in an oxidative hydrothermal step. Alumina is then extracted in a caustic digestive leach. The unique technology produces four primary commercial products l molybdenum trioxide, vanadium oxide, aluminum trihydrate and nickel-cobalt concentrate. This paper discusses the process, modifications. during ten years of operation, and the relationship of these modifications to the future of the catalyst recycling business.

Jan 1, 1995

By Xiangwen Wang

Electrochemical measurements associated with the electrowinning of lead metal from concentrated brine (NaCI) - lead chloride (PbCI,) electrolytes at temperatures in the range 328 to 353°K (55 - 80°C) were conducted. The electrodeposition of lead metal onto a lead rotating-disk electrode may be described by the electrodic reaction: {PbCl 4 2 + 2e- = Pb° + 4Cl-} The deposition-overpotential requirements are low (approximately 41mV per decade of current density - Am+), with a corresponding high exchange current (approximately 0.018 A.cm2). The diffusion coefficient of the electroactive PbC142- species in a 3.5 NaCl electrolyte at 353°K was insensitive to the total PbCI, concentration (0.01 to 0.1M), and its value was found to be (1.21*0.1)~10-5 cm2Is with a temperature-sensitivity coefficient (E,/R) of approximately 1.98x103K-1 (328OK(T<353OK).

Jan 1, 1993

By Fei Ruan, Chang Jie, Jieyu Zhang, Jifang Xu, Kuochih Chou

"Viscosity is an important physical parameter of slag in metallurgical processes. Most studies of aluminosilicate and aluminate systems assume that aluminum occurs in tetrahedral coordination. In this case, the O/Al value was utilized to describe the slag structure in terms of the network character of aluminosilicate and aluminate systems. Composition and viscosity data from the literature and the trends were analyzed according to the O/Al value and temperature. It is shown that the O/Al value explains the trends in more than ten systems, containing more than 200 data points. In aluminosilicate system, the trend that viscosity value changed with the O/Al value which implies that alumina works as network modifier such as basic oxides or works as network former. In aluminate system, irrespective of the system and temperature, viscosity decreased steadily when O/Al value increased.IntroductionMetallurgical slags, which are made of oxides and many also contain fluorides, play an important role in metallurgical processes such as iron making, steel making and secondary refining processes. Aluminosilicate slags are applied in a wide range in metallurgical processes. A polymerizing effect of the addition of aluminum and an association of aluminum with low-field strength cations is further supported by the physical variations in aluminosilicate and aluminate systems. The behavior of alumina in silicate melts has been studied by various authors [1-6]. It is generally accepted that Al2O3 is amphoteric [7] because Al3+ ions can behave in profoundly different ways in a silicate melt. When added to a pure silica melt, Al2O3 acted as a network modifier, breaking the bridging oxygen of the pure silica network, thereby decreasing the viscosity in a similar manner to other network modifiers, such as CaO, MgO etc. to form [1/2Ca (AlO4)]4- complexes. However, when added with alkali or alkali-earth metal oxides, some of the Al3+ ions assumed tetrahedral coordination and replaced Si in the liquid network, the missing charge was compensated by Me+ or Me2+ ions. Therefore Al2O3 acted as network former [8, 9]."

Jan 1, 2011

By Bin Xu, Qian Li, Xiaoliang Liu, Yongbin Yang, Tao Jiang, Yan Zhang

The cohering behavior of iron ore pellet powder in kiln cannot be reflected entirely through the conventional briquetting method, so a novel natural stacking method was proposed in this paper. The results showed that in the two methods the cohering strength of powders from different iron ore pellets (numbered A, B and C) rose with the increase of roasting time and temperature andpresented the same result, i.e., C > B > A. Comparatively, the natural stacking powders obtained much lower cohering strengths under the same roasting condition. The structure analyses of ring from the kiln tail and cohering briquette by the natural stacking method indicated that the occurrence of crystallized particles of them were extremely similar. Therefore, the initial information of pellet powder’s cohering behavior could be provided by the natural stacking method, improving the methods to study the actual ringing process and mechanism of pellet powders in kiln.

Mar 1, 2017

By Tao Zeng, Jianchao Li, Chang Jie, Jieyu Zhang, Jifang Xu, Kuochih Chou

"The densities of the selected quaternary Ca0-5%Mg0-Alz03-Si02 slag with low silica were measured by the Archimedean method in a wide temperature range from l 723K to 1823K. Slag compositions were chosen based on five different levels of Si02 content between 0.00 pct and 11.40 pct. The MgO content was equaled to 5.00 pct. The mass ratio of CaO/Alz03 was varied from 0.67 to 2.14. The effects of temperature, Ca0/Alz03 ratio and optical basicity were studied. It is shown that density decrease approximately linearly with an increase in temperature. With the same Si02 content, the density decreases with increasing of CaO/Alz03 ratio and optical basicity. Based on the experimental data as the boundary of the homogenous phase region predicated by F ACTSAGE software, the mass triangle model is used to calculate the density of selected limited homogenous phase region. The results showed that the mass triangle model is working well.IntroductionIt is of great importance to measure density of slag melt not only to the theory research for melt, which that is directly amenable to the structure correlations of molten slags, but also to the industrial application. Many metallurgy phenomena such as inclusion formation in molten melt and its removing, slag foaming, slag-metal reaction are closely related to the density of slag. Density is also required to estimate other fundamental properties, like surface tension, viscosity, and thermal conductivity from thermal diffusivity so that a relatively complete picture in regard to the behavior of high-temperature molten oxides could be made."

Jan 1, 2013

By M. Y. Mohassab-Ahmed

In an effort to develop a novel flash ironmaking process, the chemistry of selected slags was investigated. In different ironmaking processes, the molten bath (iron-slag bath) is expected to be in contact with gas atmospheres of H2/H2O, CO/CO2/H2/H2O, and CO/CO2. The latter was investigated to allow comparison with the blast-furnace conditions. The slag composition was selected to resemble that of the blast furnace with CaO/SiO2 in the range 0.8 to 1.4. The temperature range was 1550 to 1650°C. The oxygen partial pressure was maintained in the range 10-10 to10-9 atm. The effect of water vapor on the chemistry of the slag as well as the equilibrium reactions involving the slag has been studied for the first time. H2O dramatically affects the chemistry of the slag and strongly affect the phase equilibria in the slag as well as the equilibrium distribution of elements between slag and molten metal.

Jan 1, 2014

By Bora Derin

This work deals with the recovery of valuable metals from the ancient copper smelting slags located in Küre-Turkey. In this process, copper and cobalt were recovered in metallic form and/or as their compounds, whereas iron was recovered as magnetic oxide or pigment. Abrasive grit material was produced using reduced final slag. The process stages involved carbothermal reduction in a DC arc furnace, granulation, leaching, chemical precipitation, selective sulfidizing roasting and product preparations. In this paper, the process stages were described as theoretically and experimentally whereas slag and products were characterized in detail.

Jan 1, 2003

By A. V. Reddy, C. Beckermann

"The DC continuous casting of a grain refined AI-4.5%Cu round ingot with realistic boundary conditions is numerically simulated. Of particular interest are the effects of the transport of free solid in the form of equiaxed grains on the macro segregation patterns and the final grain size distribution. The study uses a previously developed two-phase model that incorporates descriptions of heat transfer, solute redistribution, melt convection, and solid transport on the system scale with microscopic models of solutal undercooling, microsegregation and grain impingement. The numerical results indicate that grain transport inhibits the formation of inverse segregation in the ingot shell and promotes negative centerline segregation. This is explained by the reduction in the solid coherency next to the mold and the advection of solute-lean grains towards the centerline. Comparisons with the experiments of Finn et al. [5] illustrate the need for considerable improvements in the model. IntroductionMacrosegregation continues to be one of the concerns in DC continuous casting of aluminum ingots. The variation in composition over the ingot cross section results in the need to adjust alloy composition in order to meet mechanical property specifications in finished products. The extent of macrosegregation is greatly affected by the casting conditions, such as casting speed, superheat, cooling rate, mold size, alloy composition, and grain refining practices. Thus, it is of great interest to develop a comprehensive mathematical model to simulate the casting process, enabling the selection of conditions that minimize macrosegregation while maintaining a high productivity."

Jan 1, 1994

By K. Mansfield

Spent Pot Lining (SPL) is an unavoidable waste product of the electrolytic process in the smelting of aluminium. SPL is considered to be a hazardous waste in various countries because it contains significant quantities of absorbed fluorides along with traces of cyanide. In 1995, Portland Aluminium undertook the investment of AUD$26,400,000 to construct a Research and Development processing facility at Portland, Victoria, Australia, to treat SPL. Extensive research, development and design were carried out over 5 years prior to the investment decision. This study led Portland Aluminium to install an Ausmelt pyrometallurgical furnace to combust and melt the SPL producing a hydrogen fluoride (HF) laden gas, which was cooled and then converted to aluminium fluoride (AlF3). Both the cooling and AIF3 manufacture were processes developed by Portland Aluminium. Many commissioning, equipment reliability and process problems have been encountered that had not been experienced in the trials at Ausmelt or in the developmental process for the treatment of the furnace offgases to form AlF3. Designs based on anticipated process expectations have had to be re-engineered by the SPL team to ensure plant and operational success. In June 2001, the installation of the final major component - a slag granulation process - was completed. This has produced a vitrified (glassy) slag that is expected to have leachability qualities acceptable to the Victorian Environment Protection Authority (EPA) to allow commercial end uses of the slag material to be developed. Today (September 2001), the smelter has successfully used the fluoride product, namely 65- 70% AIF3, in aluminium production and the SPL plant has significantly increased throughput with expectations to be at annual design rates of 12,000 tonne of SPL in early 2002. "The Alcoa Portland SPL Process" has been technically developed and is a proven process for the treatment and recovery of valuable components from SPL materials.

Jan 1, 2002

By D. J. Chaiko

Certain radionuclide ions (e.g., TcO4) exhibit unusually strong Affinities toward the polymer-rich phase in aqueous biphase systems generated by combinations of salt solutions with polymers such as poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG). Thus, aqueous. polymer ,phases could potentially be used to selectively extract these ions during pretreatment of radioactive tank wastes at Hanford. To help develop a fundamental understanding of the interactions between various ions and polymers in aqueous solution, interaction enthalpies between sodium -perrhenate and a random copolymer of PEG and PPG (UCON-50) were measured by microcalorimetric titration. An entropy compensation effect was observed in this system in which changes in enthalpic interactions were balanced by entropy changes such that the interaction free energy remained constant and approximately equal to zero.

Jan 1, 1999

By Shu Bin, Lin Chen, Tian-zu Yang, Wei-feng Liu, Wan-da Bin

"Antimony resources are rich in china, its reserves and productions are ranking the first in the world. The Chinese antimony mineral resources are mainly existed in the form of three types, such as stibnite, antimony-gold ores andjamesonite. The antimonial dust that produced from lead smelting process is an important secondary antimony resource. The different process that was adopted to extract antimony depends on the different raw materials. The process of blast furnace volatilization smelting is mainly used to treat stibnite and antimony-gold ores. But jamesonite is treated by the process of roasting-sintering-blast furnace smelting. And antimonial dust is treated in the reverberatory furnace. Many new technologies that are applied in these traditional antimony smelting processes play important roles, such as deleading agent, antimony white production, air-oxidation method, direct-blowing method, bath smelting technology, and so on. At the same time, the development of antimony smelting technology in china is prospected according to the requirement of the state environmental protection.IntroductionThere are five countries that produce antimony in the world, such as china, Tajikistan, Bolivia, Russia, and South africa, but China is the largest country of antimony production in the world. In the world, the antimony productions of 2008, 2009, and 2010 are 182,000 tons, 154,000 tons, and 167.000 tons respectively, but Chinese antimony productions are 166.000 tons, 140,000 tons, and 150,000 tons respectively. So Chinese antimony production was accounted for more than 89% of the world in 2010. It indicates that China have irreplaceable advantages in antimony resource and production all over the world."

Jan 1, 2013

By Jerold L. Johnson

Remediation of small-arms firing ranges is being investigated by the Naval Civil Engineering Laboratory and the U.S. Bureau of Mines. Scheduled closures of military installations, as well as the management of active ranges, require the development of methodologies for heavy metals removal to prevent their entering the surrounding environment. The impact berms contain high concentrations of metals, and the soil and vegetation surrounding the berms were found to have slightly elevated levels. The heavy metals characterized are in the form of whole bullets, a wide size distribution of free fragments, smeared lead on the surface of the soil grains, and very finely attached particles. Gravity beneficiation can remove liberated metal contamination effectively. Weak acetic acid leaching shows promise in lowering the final metal contamination to allow the ,soil to pass the Environmental Protection Agency&apos;s (EPA) Toxicity Characteristic Leaching Procedure (TCLP) criteria.

Jan 1, 1993

By Maryam Ghodrat, Bijan Samali

Treatment of polymer-based wastes has a tremendous potential for generating alternative energy, reducing greenhouse gas emissions, creating economic and environmental benefits, and achieving a sustainable development of the energy sector. During the past few decades, plastic waste generation increased at a greater rate than the population, with the move towards single-use products. Also with raising the cost of oil-based products, greater emphasis should be placed upon the usage of plastic/polymer in the waste stream as a supplementary source of fuel. This study presents a techno-economic analysis of the recycling potential of plastic waste in Australia by evaluating the possible use of these wastes as a reductant in steel making incinerators. The study tries to shed light on a possible cost effective alternative route in the smart treatment of waste plastic in Australia.

Mar 1, 2018

By R. Schuhmann

The thermodynamic data and calculations which underlie the design of the Q-S process for coppermaking are summarized. The efficient production of crude copper and slag of low copper content in a single con¬tinuous converter requires the establishment and control of gradients in oxygen activity and other physico-chemical variables throughout the reactor. These gradients are established by stagewise introduction of oxygen and solid feed materials to provide: (a) flash oxidation of sulfides above the bath, utilizing the great bulk of the oxygen, (b) conversion of high grade matte or white metal to crude copper by bottom blowing with restricted bath turbulence, (c) close approach to equilibrium staging of converting and deconverting reactions along the length of the slag layer, from a maximum oxygen activity near the metal discharge end to a minimum at the slag discharge end, and (d) completion of slag cleansing by deconverting. In terms of the Phase Rule, the Q-S process involves a system with a minimum of 5 components (Cu, Fe, S, O, and SiO2) and several liquid, solid, and gaseous phases. Accordingly, basic data from previously reported studies on simpler systems are utilized to prepare an equilibrium diagram for the 5-component system and to generate a quantitative thermodynamic model for the Q-S process. This model shows in particular the ranges of oxygen activities (measured by equivalent CO2/CO ratios) involved in the Q-S process and the relations of oxygen activity to temperature and other important physico-chemical variables of coppermaking.

Jan 1, 1976

By Boyd Davis, Vladimiros Papangelakis, Joshua LaMarre, Jan de Bakker

"HCl leaching using molten salt hydrates has the potential to improve the extraction of nickel from laterite ores. However, as in other HCl leaching applications, recovery of HCl is key to process economics. Spray pyrohydrolysis, which is used in current chloride-based flowsheets, is associated with a high energy cost. The authors have developed a proposed laterite leach circuit using an alternative HCl recovery route. The leach circuit envisions a leach by concentrated (33%) HCl in an MgCl2 molten salt hydrate (MSH) or brine medium, followed by Ni/Co recovery and iron precipitation. Magnesium and chloride are precipitated from solution as magnesium hydroxychloride; this hydroxychloride is thermally decomposed to produce HCl gas. The proposed flowsheet employs a chloride leach circuit with simpler equipment and lower energy cost than in the conventional practice of pyrohydrolysis. Laboratory work investigated key aspects of the flowsheet, including precipitation of magnesium hydroxychlorides and their composition; magnesium hydroxychloride thermal decomposition; and iron control.Introduction As sulphide nickel ores become harder to mine and more complex to process, laterite ores will increase in importance. Laterite ore deposits can be divided into two main mineralogies. Limonite ores consist mostly of hydrated iron oxide, FeOOH, with 1-3% nickel substituting for the iron. Saprolite ores consist of iron-magnesium silicates, (Fe, Mg)2Si04, again with some nickel substituting for the metal ions. Limonite ores can be treated using the HP AL (High Pressure Acid Leach) process, in which the ore is reacted with sulphuric acid at high temperature in an autoclave. HP AL, however, cannot in general be used to treat saprolite ores because the magnesium enters solution and consumes sulphuric acid, which results in excessive spending on lixiviant. It is therefore desirable to find a hydrometallurgical process specifically for saprolite ores that can provide better results than the treatment options currently available."

Jan 1, 2011