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By Carl C. Nesbitt

A process has been developed to recover and recycle metals from wastes of brass foundries which contain copper, zinc and lead in various quantities. Tests were conducted to evaluate several leachants, including sulfuric acid, ammonia, hydrochloric acid, cyanide and acetic acid, and to determine the optimum leaching conditions, such as air flow rate, initial copper ion concentration, temperature, and agitation strength. Sulfuric acid containing copper sulfate with dissolved oxygen is the most successful leachant. More than 99% of the copper and zinc originally present in the waste was dissolved, while only 0.5% of the lead entered the solution after 14 hours of leaching. The leaching mechanisms of copper, zinc, and lead are proposed. The copper and zinc can be recovered from the solution by electrolytic processing. The unleached residue may be converted to a lead carbonate which can be converted to litharge at 400-450°C and to massicot at temperature above 500°C by calcination.

Jan 1, 1995

By P. Ret, E. Üstiindag, R. Dieckmann, R. Subramanian, S. L. Sass

"Partial reduction reactions in the Ni-AI-O system, starting with the spinel compound NiAI20 4, are used to form metal-ceramic microstructures. By suitable choice of processing parameters, such as reduction temperature, oxygen partial pressure and time, two different morphologies of nearly pure Ni particles, equiaxed and rod-like, form within a ceramic matrix, which is either a-A12O3 or a metastable ""defect spinel"". Electron microscopy studies were performed for microstructural characterization, phase identification and chemical analysis. The fracture toughness of the Ni-AI2O 3 mixture was significantly improved with respect to that of the original spinel phase. The important issues that must be addressed to form useful metal-ceramic microstructures by partial reduction reactions rue discussed. It is shown that cracking at the original spinel grain boundaries, likely due to the large volume changes associated with the reduction reaction, can be avoided by the addition of small amounts of ZrO2• Initial results illustrating effect of ZrO2 on the microsuuctures are presented.IntroductionEngineering materials used in load bearing circumstances, particularly under extreme conditions (e.g. high temperatures or stresses), generally are formulated with complex microsuuctures. Such composite-like materials can possess properties unobtainable by either of the individual constituents. With metal-ceramic composites, for example, a material can be obtained with an optimum combination of the low density and high strength of the ceramic, and the toughness of the metal. For high temperature service, where demanding conditions are often present, for example, inside jet turbine engines, a successful new material must have low density, high Young's modulus as well as good oxidation resistance, strength, fracture toughness, creep and fatigue resistance. The candidates include intermetallic compounds, and metal-ceramic, intermetallic-ceramic and ceramic-ceramic composites."

Jan 1, 1994

By Evgenii Pavlov, Ivan Tronin, Viktor Timofeev, Vladimir Kislov, Sergei Bogovalov

"Modeling of the magnetohydrodynamical (MHD) and thermodynamical processes during the industrial scale Direct Chill (DC) casting of aluminum slabs is performed using a combination of ANSYS/CFX and ANSYS/EMAG software. The electromagnetic field is modeled through ANSYS/EMAG, while hydrodynamic and thermodynamic processes are modeled through ANSYS/CFX. Both packages were modified in order to calculate MHD flows in the liquid pool that forms during aluminum DC casting, and they were unified into a software combination that provides simultaneous simulation of all the above processes. The simulation shows that the electromagnetic stirring of the molten aluminum changes the shape of the solidification front (solid-liquid interface) very dramatically, namely it becomes significantly flatter. This effect should improve the internal structure of aluminum DC slabs and allows us to increase the casting velocity.IntroductionProduction of Aluminum alloys with high mechanical properties and structural uniformity is one of the main goals of industry. The preferred production method of aluminum alloys in most modern plants is Direct Chill (hereafter DC) casting because it offers high productivity and commercial success. One important limitation of this technology is the development of centerline shrinkage in slabs larger than about 1 meter. The improvement of the internal structure of long DC cast slabs can be achieved by electromagnetic stirring (hereafter ES) of the liquid metal above the solidification front. This intensifies heat transport in the zone close to the solidification front and suppresses shrinkage formation."

Jan 1, 2013

By Katsumi Ogi, Hiroto Uchida, Masamitsu Sato, Atsushi Itsuki

"(BTMSE)Ag(hfac) (BTMSE = trans-bis(trimethylsilyl)ethene) was chosen as a suitable precursor for the XeCl laser (308nm) MOCVD of Ag. Iso-propanol solution of (BTMSE)Ag(hfac) was used as a liquid source for the liquid delivery method, high deposition rate 9nm/min at substrate temperatures of 100°C and 120°C were obtained at the vaporizer temperature of 90°C. This deposition rate is three times faster than by conventional bubbling method and life of the source and reproducibility of the deposition were also improved. Electric resistivities of the laser deposited film shows significantly low resistivity of 10-6Q-cm compared to 1 o-3Q-cm of thermal MOCVD film. These results indicates that the laser MOCVD is one of the effective method for the preparation of the high quality silver film.IntroductionSilver films are a potentially important metallization material in electronic and photonic devises due to their lowest resistivity (1.6µ0-cm) among the metals, high optical reflectance and chemical stability. The MOCVD technique has advantages to sputtering or evaporation in the point of conformal growth and better coverage on sharp steps and narrow gaps[l-2]. For MOCVD application, silver precursors must have sufficient vapor pressure without decomposition at their evaporation temperature. To achieve stable precursor gas supply, liquid delivery of precursor material is promising[3-4] especially for materials that have not enough heat stability and high vapor pressure like silver complexes[S-10]. Several new silver complexes for MOCVD and UV irradiation effect to their MOCVD silver film quality were reported by same authors[5]. In this paper new solvent system for liquid delivery system of silver MOCVD were investigated to suite XeCl(308nm) laser MOCVD application."

Jan 1, 1998

By Huimin Lu, Shi Zhou, Lisha Yang

"The Zeolitic imidazolate frameworks (ZIFs) were successfully synthesized by applying a combination of ionothermal synthesis and microwave energies for rapid synthesis. The synthesis was proceeded under various conditions including different raw materials, reaction temperature as well as microwave irradiation time. Zeolitic imidazolate frameworks (ZIFs), also known as coordination polymers, are new type of porous materials formed by inerratic polyhedral in three-dimensional. They are the ideal crystalline substances for gas separation and storage. The assynthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and C02 adsorption test. Results illustrated that the synthesized samples had stable structure, high thermal stability (up to 530 °C) and C02 adsorption capacity (10.2 cm3/g at 0°C under ambient pressure). This novel method also showed great advantage with high energy efficiency, safe synthesis conditions, and rapid crystallization time (60 minutes).IntroductionNowadays, carbon dioxide capture has become imperative due to the global warming caused by the increase of C02 in the atmosphere, especially produced by the concentrated sources such as power plants [1]. Zeolitic imidazolate frameworks (ZIFs), also known as coordination polymers, are ideal crystalline substances for gas separation and storage due to their structure diversity, high thermal and chemical stability [2-5]. They are formed by inerratic polyhedra in threedimensional with large cages and small apertures. Traditionally, ZIFs are synthesized by solvothermal method in a sealed autoclave under autogenous pressure [6-9]. However, in order to generate the products, the solvothermal temperature should not be lower than 100°C according to the sovlothermal mechanism. Moreover, at such a temperature, molecules with a low boiling point (such as water) may generate high pressure in reactor which might cause danger [9]. Thus the synthesis requires the equipment to possess resistance to autogenous pressure and corrosion. Further, conventional solvothermal methods need a long time to prepare products, usually a few days, which is a large energy consumption and inefficiency. So it is interesting to synthesis ZIFs through other ways under mild reaction condition with high energy efficiency."

Jan 1, 2012

By Jean P. Murray

The extractive metallurgical industry is a major consumer of high-temperature process heat. It is, consequently, a major contributor of C02 emissions and other greenhouse gases derived from the combustion of fossil fuels for heat and electricity generation, or from the process itself. These emissions can be substantially reduced by replacing fossil fuels with solar energy as the source of process heat. Concentrated solar radiation can supply a large amount of thermal energy to endothermic reactions at temperatures exceeding 2000 K. Another potential for C02 emission reduction exists as well. Thermodynamically, the total amount of energy required for metal production at any given temperature is the enthalpy change of the reaction, AH. Of this total, an amount equal to the Gibbs free energy AG must be supplied as high quality energy in the form of electrical work or by using a reducing agent. Many conventional metallurgical electrolytic processes and reducing furnaces are unable to add only the thermodynamically required electricaVchemical energy due to process inefficiencies. Electrical work in excess of AG for the reaction may be used to supply process heat, or excess chemical reducing agent burned to supply process heat. Besides the thermodynamic and economic drawback, this inefficiency results in excess C02 emissions derived from the combustion of fossil fuels. With these practices, energy becomes an important cost element of the metal produced. Highly-concentrated solar energy has the demonstrated potential to separate these two forms of process energies, allowing the addition of only the thermodynamically required high-quality energy while high-temperature solar process heat is provided to the reactor. Examples of metal oxide reduction processes that have been studied experimentally in solar furnaces include the production of Fe, Al, AI/Si alloy, Mg, Zn, Tic, Sic, CaC2, TIN, Si3N4, and AIN by carbothermic reduction of their oxides, and the high-temperature solar- electrothermal reduction of ZnO.

Jan 1, 1999

By Denis Shishin

The pyrometallurgical production and recycling of non-ferrous metals involves the use of complex feed stocks, having awide range of chemical compositions from sources that include mineral sulphide concentrates, high value obsolete materials and process wastes. The commercial viabilities of these operations hinge on the ability to extract value from these materials. Increasingly, modern computer-based tools are used to describe and predict process outcomes, including mass and heat balances, the partitioning of elements and phase equilibria. At the heart of these predictive tools are thermodynamic databases that describe the fundamental chemical properties of a system and all the components present. A comprehensive research program has been established to develop an accurate, self-consistent thermodynamic database describing all gas-slag-matte-metal-speiss-solid phases in the system Cu2O-PbO-ZnO-Al2O3- CaO-MgO-FeO-Fe2O3-SiO2-S-(As-Bi-Sb-Sn-Ag-Au). The database can be used in conjunction with the FactSage computer platform. The accuracy of the database and its application to industrial practice is demonstrated.

By H. K. Fouad, L. A. Guirguis

The starting mill strip solution· for this study· is an ammonium uranyl tricarbonate solution of pH 8.2 containing 20g uranium/liter, after a DEPA/TOPO extraction process from sulfuric acid leaching liquor. To the first portion of the concentrated acidified strip solution, hydrofuoric acid is added at 95°C in reduced condition to obtain uranium tetrafluoride. The second portion of the uranyl carbonate strip is subjected to a precipitation step by admixing 0.3 volume of non-solvent precipitating agent such as acetone per volume of uranium. ·Uranium oxide (U30 8) is obtained from this precipitate by calcination for half an hour at 800°C in air. The third portion of the strip solution is neutralized to a pH 6.5 with sulfuric acid to precipitate iron and other contaminants. The solution is further acidified to a pH 1.85 with continuous air bubbling to remove CO2, followed by H2Ch precipitation at pH 3.5 to obtain uranyl peroxide. The latter is reduced by stannous chloride to obtain uranium trioxide dihydrate UO3. 2H20. Identifications, characterization· and purity of these products are carried out by complete chemical analyses, Scanning electron microscope study, tap density determination, X-ray diffraction and infrared spectroscopic investigations. The achieved results agreed well with that of the published data for these nuclear grade purity products.

Jan 1, 2000

By G. L. Pedroti

With the development of industrial processes and the consequent emergence of numerous products that quickly become necessities, industrial activity has acquired an essential character today. Although its importance is unquestionable, industrial activity is responsible for generating quite a large number of residues, with different shapes and characteristics. It has been observed, in particular the grits (Kraft process in the cellulose industry) and the residue from the processing of granite. And, given the importance of Portland cement as a building material, its vast employment and waste properties that resemble components of the clinker, it was decided to produce cementitious compounds from these industrial wastes. The residues were subjected to mineralogical, chemical, physical and morphological. And, the mixing ratio between the residues in the 70% and 30% grits residue granite was sintered at 1250 ° C furnaces to burn threshold of 6 hours forming new compounds observing tri-calcium aluminate and di-calcium silicate that are compounds found in portland cement.

Jan 1, 2015

By H. Conrad, K. Jung

"The effect of an external electric field E=5(+) kV/cm applied during the solution heat treatment at 500°-550°C of three commercial Al-Mg-Si alloys (AA6061, AA6022 and AA61l1) on the asquenched resistivity Pw and hardness H.,NULL, w was investigated. It was found that the field gave a significant increase in Pw and in Hv,w, for AA6022 and AA6111, but had no clear effect on AA6061. Thermodynamic analysis gave that the effect of the field on AA6022 and AA6111 was to reduce both the enthalpy ?H, and entropy ?H, of solution. Considering the chemical composition of the three alloys it appears that the influence of the field may depend on the amount of Cu plus excess Si present in the alloy.IntroductionKlypin and Soloviev [1, 2] were the first to report that the application of an external electric field during solution heat treatment (SHT) of Al alloys gave an increase in the as-quenched resistivity and hardness. They attributed these effects of the field to an increase in solubility of the alloying constituents during the SHT. More recently Liu and coworkers [3, 4] also reported an increase in the as-quenched resistivity of Al-Li alloys with application of an electric field during SHT. Further, the present authors [5] found that the application of an electric field during the SHT of the commercial Al-Mg-Si alloys AA6022 and AA61i1 increased their as-quenched resistivity and hardness. Their thermodynamic analysis of the results indicated that the field decreased both the enthalpy ?H, and entropy ?S, of solution."

Jan 1, 2004

By Chikabumi Yamauchi

The comprehensive scientific development of conventional industrial technologies stimulates the creation of new ones in the next generation. Prof. Akira Yazawa has just accomplished such an important work in the non-ferrous pyrometallurgical field. The results of his successful research are immortal. The research group of the author has conducted since 1985 fundamental studies on the application of sodium carbonate slag to copper fire refining. In the present paper, a calculation method for the distribution ratios of impurity elements between sodium carbonate slag and molten copper will be shown. The specific treatment by sodium carbonate slag will also be presented as an effective way for reducing each impurity content in the molten copper to 0.1 mass ppm, which is the level required for the production of high purity copper. The thinking-out of this evaluation method gets a hint from the Equation (2) in the text which was proposed by Prof. Akira Yazawa.

Jan 1, 2003

By Chunyang Guan, Jilai Xue, Jun Zhu, Qiaochu Liu

"Al-Sc Alloys have showed many advanced properties for a wide range of industrial application, which is usually produced using thermal reduction process. This work is aimed to develop an electrochemical process to make Al-Sc alloy using industrial Hall aluminum reduction cells. The experiments have been carried out in a lab cell where NaF/AlF3-Al2O3-LiF as electrolyte, Sc2O3 as raw material, and liquid aluminum as cathode were used at operating temperature of 950 °C. The resulting Al contained 0.2 - 0.5 wt.% Sc that is the common range in its content for advanced applications. However, a small fraction of Sc was found from thermal reduction at Al melts interface. SEM-EDS and ICP-AES analysis showed a uniformed distribution of Sc at varying locations of the Al-Sc alloy sample. In addition, a higher Sc content in Al-Sc alloy can be obtained with introducing ultrasound through the cathode than that without it.IntroductionIn recent years, scandium has been investigated as an alloying element for aluminum alloys. With addition of a small amount of Sc, Al alloys can improve the strength, weld ability, resistance to re-crystallization and corrosion resistance [1-3]. Due to their advanced properties and potential applications, the demand for Al-Sc alloys will increase in the future. However, the difficulties in reduction technologies and the high costs in production process may limit their expansion in application areas.The current major method of producing Al-Sc alloys is to mix Sc into Al by melting Al-Sc master alloy. This alloying process has several technical problems, such as easy segregating and heavy burning loss, etc. The price of Sc metal or starting material is also high, so the mixing process is an expensive alloying method. Molten salt electrolysis is alternative method to prepare RE metal and RE alloys [4, 5]. It also can reduce the segregation of alloying elements. Sc2O3 is an ideal material as raw material with low price and decomposition voltage. Some work has proved that Al-Sc alloys can be obtained by electrolysis Sc2O3 directly in cryolite [6-8], or CaCl2 molten salt [9]."

Jan 1, 2012

By Sang Han Son

The vapor pressures of FeCI2 and ZnC12 in the FeCl2-ZnCl2 system were measured by the transpiration method at 873K and 917K. The vapor pressure data were interpreted to indicate the formation of complex ions in the FeCl2-ZnCl2 melts. It is presumed that the complex molecule FeZnCl4 as well as FeCI2 and ZnCI2 exists in the vapors in equilibrium with molten FeCl2-ZnCl2 mixtures. The activities in the FeCl2-ZnCI2 system are shown a negative deviation from Raoult's law. These results suggest the formation of complex ions such as ZnCl42- in molten FeCI2-ZnCI2 mixtures.

Jan 1, 2003

By P. Chris Pistorius

"Ilmenite smelting involves partial reduction of iron oxide from a slag consisting mainly of T1O2, T12O3 and FeO, yielding as products iron (with approximately 2% carbon) and titanium slag. Slag purity requirements preclude any fluxing additions, and the aggressive nature of the slag necessitates a furnace freeze lining. Large departures from thermal and chemical equilibrium hold in the smelter, with possible implications for process stability. The slag is approximately 150K. hotter than the metal, which means that the metal temperature is below the slag melting point; this difference in temperature has been shown to lead to formation of a solid TisOs-rich layer between the slag and metal. Recent equilibrium measurements have confirmed that the slag and metal are not in chemical equilibrium either, with significantly more reducing conditions in the metal than in the slag. After solidification, the pseudobrookite slag structure is metastable below approximately 1400K, and may transform upon slight oxidation.IntroductionThe natural mineral ilmenite is the main source of titanium, which is mainly used to produce Ti02-based pigments. Ilmenite has the ideal formula FeTiC>3, but natural minerals can be partially oxidized (to contain some Fe3+), and typically contain MnO and MgO as well, together with associated silicate minerals. Smelting is one of the methods to upgrade ilmenite for subsequent T1O2 pigment production; smelting involves partial reduction of FeO to form metallic iron as a byproduct and titanium slag as the main product. Reduction is typically controlled to yield a slag which contains around 10% FeO, 85% (Ti02+Tij03) and 5% impurity oxides (mainly MnO, AI2O3 and S1O2). An example of a typical average slag composition from reduction of South African ilmenite is shown in Table I. As this indicates, a significant side reaction is reduction of some T1O2 to T12O3. The relative extents of reduction of FeO to Fe and of Ti02 to T12O3 are such that the slag stoichiometry is close to that of the pseudobrookite phase [1]. Pseudobrookite has the structure AB2O5 (where ""A"" and ""B"" are different cation sites); the phase which makes up the bulk of solidified titanium slag has the AB2O5 structure and stoichiometry [2], and can be viewed as a solid solution of FeTi20s, T13O5, ÌçÔÀ2è5, MgTi20s, AI2T1O5 and C^TiOs [1]. This solid-solution phase is referred to as ""pseudobrookite"" or ""M3O5"" in this paper."

Jan 1, 2012

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

By P. D. Lee

The effect of strontium on porosity formation in aluminum-silicon alloys is not well understood and there is no consensus upon the cause of the effects observed. This paper describes a series of experiments where the effect of adding strontium on pore formation was observed directly with combination of a traditional temperature gradient stage and real time micro-focus radiography. These in situ observations provide a new insight into the effect of strontium on the nucleation and growth kinetics of porosity. The addition of strontium was found to have a minor effect on the growth of the pores in the mushy zone. However, strontium appeared to alter the nucleation and stability of hydrogen bubbles within the melt. The interaction of strontium with titanium-boride grain refiners produced an even stronger change in the nucleation and stability of the bubbles formed.

Jan 1, 2002

By Mansoor Barati, Shaghayegh Esfahani

"The slag from extraction of ferrous and non-ferrous metals is a potential heat source which if treated properly can contribute to recovery of a significant amount of energy. The waste heat of slag may be used to generate steam, synthetic fuel gas, or electricity. Although several technologies have been investigated for this purpose, very little has been achieved in terms implementing the technology in industry. In this article, the development and application of various granulation techniques are reviewed and the methods to recover energy from granulated slag are discussed.IntroductionEvery year, more than 422 million tons of slag is being produced around the world as a by-product of the metal manufacturing at temperatures of up to 1300-1600°C [1, 2]. Currently slags are either disposed of or treated by processes such as granulation. Through the granulation process, most slags can be converted into a material which may be fully used as a cement feedstock. Conventional cement production is an energy intensive process with large emissions of CO2; therefore, the replacement can both be energy saving and environmentally friendly. However, for this purpose, the slag should have what is known as a “glassy” content (i.e. it should be amorphous) which requires rapid cooling rates that are not easily achieved due to the very low thermal conductivity. The main challenge in all these processes is to granulate the slag at a high cooling rate while the heat is also being recovered."

Jan 1, 2012

By Sang Han Son

The vapor pressures of FeCL2 and ZnCL2 in the FeCL2?ZnCL2 system were measured by the transpiration method at 873K and 9I7K, The vapor pressure data were interpreted to indicate the formation of complex ions in the FeCL2?ZnCL2 melts, It is presumed that the complex molecule FeZnCl4 as well as FeCL2 and ZnCL2 exists in the vapors in equilibrium with molten FeCL2-ZnCL2 mixtures, The activities in the FeCL2-ZnCL2 system are shown a negative deviation from Raoult's law. These results suggest the formation of complex ions such as ZnCL14 in molten FeCI2?ZnCL2 mixtures.

Jan 1, 2003

By Y. K. Rao

In the carbonyl process for the refining of crude nickel CO(g) reacts with nickel in the 310-370K range producing nickel tetracarbonyl, Ni(C0)4(g). Iron and cobalt impurities also form gaseous carbonyls but their partial pressures are low. The carbonyl is led to a decomposer plant wherein the gas disproportionates in the 500-600K range depositing pure metal on nickel pellets that move countercurrent to the gas-flow. This system serves to illustrate the fundamental principles involved in the vapor phase mass transport of elements, against temperature-gradient, under the influence of chemical potential gradient. Unlike in the crystal growth, the source is at a lower temperature (say 350K) whereas the seed is in the hot-zone (say 550K) of the closed ampoule-type reactor. By assuming virtual gas-solid equilibria in the end zones, with diffusion of gaseous species between them acting as a slight perturbation, the quasi-steady- state mass-transport rates are computed for a range of CO-pressures and temperatures.

Jan 1, 1993

By S. A. Davis

In July of 1996, the Kroll process began production again at TIMET's Henderson, NV, manufacturing facility. This, after being shut down for several years due to low market demand for titanium. Faced with limited pond capacity and increasing costs for water and wastewater disposal and storage; process changes were made to recycle water used to wash Kroll titanium sponge back into the sponge leaching process. This idea was revisited from 1992-93, when three consecutive attempts to recycle water for this application were unsuccessful due to early pump failure. Since it was uncertain why previous attempts failed, a complete understanding of the existing system was first sought. This included reviewing piping and flow diagrams; taking field measurements for all the piping, valves, and fittings; analyzing the wastewater composition; and modeling the fluid dynamics and control of the system. The fluid dynamics of the system were modeled by breaking the piping network up into nodes and applying the Bernoulli equation to each segment. The fluid flowrate control valves were modeled for this purpose also and the models were used to help specify the required processing equipment and control ranges and tolerances. Once the project was completed, an operating procedure was prepared for operation, startup, and shutdown of the washer water recycle system.

Jan 1, 1999