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By S. C. Dhara

The recovery of Platinum Group Elements from various industrial scraps and spent materials in the form of high and low grade, such as, impure metals, matte, catalysts and other ceramic substrates, etc., has .been described by using high pressure reaction method. Nickel, Stainless Steel, Titanium and glass lined reaction vessels? are used in the reaction process. Primarily, the method involves either direct leaching of the substrates from the metal value or dissolving the precious metal from the substrate. Both acids and alkalies are used along with other reagents in the reaction process. The temperature and pressure of the leaching process are the main criteria for the reaction kinetics.

Jan 1, 1989

By A. P. Paiva

Studies focused on the recovery of precious metals by solvent extraction have recently increased. either to devise suitable solvents or to clarify the involved extraction mechanisms and kinetics. In this work, a comparison of the performance exhibited by triphenylphosphine (TPP), bis-(penty1thio)-ethane (BPTE) and triisobutylphosphine sulfide CI"I'BPS) in the extraction of silver from acidic chloride media is carried out. Extraction and stripping isotherms involving the three extractants are presented together with the results obtained on the selectivity of silver extraction against high contents of iron, copper and lead. Attempts to clarify the mechanism of silver extraction by TIBPS were performed by studying the distribution coefficient dependence on ligand and chloride concentrations. The effect of temperature on extraction and stripping is also considered. The interfacial tension for the system, measured with different concentrations of extractant in the organic phase, is analysed.

Jan 1, 1994

By Nobuhiro Kuriyama

Electrochemical activation behavior of an AB2-Laves-phase type hydrogen storage alloy, Zr0,9Ti0.lNi1.lCo0.1Mn0.6V0.2 was studied to make clear activation process of pellet-type metal hydride electrodes. An alkaline treatment of the electrodes with heated alkaline solution gave alloy surface enriched with nickel, and the treated electrode was more easily activated. The treated electrode desorbed more hydrogen during the first charge-discharge cycle, and was activated without induction period. A cross sectional view of the activated electrode showed finer pulverization of alloy particles than the annealed alloy, and impedance spectroscopy indicated larger surface area of the electrode using the as-cast alloy. Since the as-cast alloy contains inhomogeneities, multi-phase microstructure and stress in the particle, the finer pulverization of alloy particles with hydrogenation are considered to increase surface area in an earlier cycle in the case of the as-cast alloy, which leads larger reaction area and faster activation of the as-cast alloy electrode.

Jan 1, 2002

By G. T. Lapidus

One of Society’s major concerns with hydrometallurgical processing is the large amount of water that is quintessential to its nature. This is especially troubling in arid areas, where the population struggles to procure potable water for their daily needs. For that reason, it has become our responsibility to conceive, design and implement processing schemes that not only use as little water as possible, but recycle streams within the plant itself and minimize waste that exits its perimeter. With this in mind, the conference will center on the importance of selecting the appropriate chemical systems and integrating material balances to avoid reagent overkill and to detect impurity accumulation. The three “R’s” (reuse, recycle and recovery) of aqueous solutions within the processes are emphasized. Examples of processes for the recovery of lead, copper, precious and PG metals from minerals and waste materials will be presented.

By Suguru Kohno, Yoshihiro Momose, Masakazu Honma, Tokirou Kamosawa

Copper metal surfaces have been examined by an extremely sensitive surface analysis technique called temperature programmed photoelectron emission (TPPE). The surfaces were ultrasonically cleaned and subsequently abraded by a screw in organic solvents and water. The TPPE apparatus is composed of a Geiger counter with Q gas (He+ iso-C4H10). The curve of photoelectron emission (PE) intensity vs. wavelength from 300 to 170 nm, termed PE spectrum, was repeatedly measured at different temperatures in the temperature- increase process from 25 to 350°C. The number of emitted electrons in a PE spectrum (PE total count) increased, reached a maximum at-250°C, and decreased with increasing temperature. With the surfaces cleaned alone in the liquids the maximum PE total count decreased in the order C3H70H > (CH3) 2CHOH > C2HpH > CHPH > H2O. With the mechanically abraded surfaces in the liquids the maximum PE total count changed as a function of the abrasion period and the maximum tended to appear at higher temperature with increasing abrasion period; the maximum value at 10-min abrasion decreased in the order H2O > CHpH > C2HPH > (CH3) 2CHOH > n-C3HpH. It was suggested that the TPPE behavior can be related to the acid-base interaction between the alcohols and the abraded metal surfaces and the presence of a contaminant over layer on the surface. From the XPS analysis of the 01 s spectra it was suggested that the chemical change of the adsorbed oxygen to oxide oxygen with temperature plays a substantial role in the appearance of the maximum PE total count.

Jan 1, 2000

By V. Montenegro

Smelting of copper concentrates in Teniente Converter produces highly oxidized slag, containing from 4 to 10 % Cu and from 15 to 25 % of Fe304. Copper recovery requires magnetite reduction at a level of 5%, determining the degree of cuprous oxide co-reduction and the liberation of copper matte inclusions. The rate of slag reduction is controlled by the mass transfer to the reaction interface. Slag stirring affects the rate of reduction and enhances coalescence of mechanically entrained copper matte inclusions. Slag reduction and sedimentation in the AC electric furnace is a commonly used method of slag cleaning. Utilization of DC electric furnace creates beneficial conditions introducing slag electrolysis additionally to chemical reductions with carbon of coke and electrodes. Application of external magnetic field, interacting with a direct current in an electric furnace, induces magnetohydrodynamic phenomena, such as intensive stirring and electromagnetic buoyancy force acting on inclusions. Laboratory scale research in simulated DC electric furnace with a superimposed magnetic field showed a significant acceleration of the rate of slag reduction and copper removal. Continuous measurement of gas flow and composition allowed for determination of the reduction rate along the time. Application of external magnetic field in the reduction of the industrial slag in a crucible simulated DC electric furnace results such as the increase of the reduction rate from 2 to 3 times, compared with the identical conditions in the AC electric furnace. Interaction of non- homogeneous electric field with crossed permanent magnetic field induces vigorous slag stirring, enhance mass transfer and accelerate the rate of the slag reduction. Additional participations of the slag electrolysis in the magnetite and cuprous oxide reduction as well as the acceleration of the settling of the inclusions by the electromagnetic buoyancy force affect the slag cleaning intensification.

Jan 1, 2003

By V. Montenegro

Smelting of copper concentrates in Teniente Converter produces highly oxidized slag, containing from 4 to 10 % Cu and from 15 to 25 % of Fe304. Copper recovery requires magnetite reduction at a level of 5%, determining the degree of cuprous oxide co-reduction and the liberation of copper matte inclusions. The rate of slag reduction is controlled by the mass transfer to the reaction interface. Slag stirring affects the rate of reduction and enhances coalescence of mechanically entrained copper matte inclusions. Slag reduction and sedimentation in the AC electric furnace is a commonly used method of slag cleaning. Utilization of DC electric furnace creates beneficial conditions introducing slag electrolysis additionally to chemical reductions with carbon of coke and electrodes. Application of external magnetic field, interacting with a direct current in an electric furnace, induces magnetohydrodynamic phenomena, such as intensive stirring and electromagnetic buoyancy force acting on inclusions. Laboratory scale research in simulated DC electric furnace with a superimposed magnetic field showed a significant acceleration of the rate of slag reduction and copper removal. Continuous measurement of gas flow and composition allowed for determination of the reduction rate along the time. Application of external magnetic field in the reduction of the industrial slag in a crucible simulated DC electric furnace results such as the increase of the reduction rate from 2 to 3 times, compared with the identical conditions in the AC electric furnace. Interaction of non-homogeneous electric field with crossed permanent magnetic field induces vigorous slag stirring, enhance mass transfer and accelerate the rate of the slag reduction. Additional participations of the slag electrolysis in the magnetite and cuprous oxide reduction as well as the acceleration of the settling of the inclusions by the electromagnetic buoyancy force affect the slag cleaning intensification.

Jan 1, 2003

By Yuuki Hagio, Hiroyuki Tobo, Michihiro Kuwayama, Yasutaka Ta

"Reduction of CO2 emission is necessary to remedy global warming, however, promising approaches of CO2 separation require a large amount of energy. Molten slag, which is generated as by-product of steel production, has high temperature, but its energy has not been harnessed. To recover the thermal energy from the slag and to apply to separation of CO2 are economical and environmental conscious ways. We propose a new heat recovery system, in which, molten slag is solidified continuously on water-cooled roll and the solidified slag plates are charged into counter-current heat recovery equipment. In laboratory scale experiments, heat recovery ratio of more than 30% was acchived by controlling the thickness of slag.IntroductionThe steel industry in Japan has been working on the projects of ""Environmentally Harmonized Steelmaking Process Technology Development (COURSE50)"". COURSE50 aims at developing technologies to reduce CO2 emissions by approximately 30%. One of the main technologies is to capture and recover CO2 from blast furnace gas using chemical absorbents to regenerate CO2-laden chemical absorbents by separating CO2 from the absorbents. As one of the solutions, JFE Steel Corporation has been developing sensible heat recovery process from steelmaking slag. It is effective to recover and use unutilized high temperature waste heat within a steel plant as the thermal energy required."

Jan 1, 2012

By John Fallavollita

Conventional gas atomization produces powders that vary widely in size distributions and microstructures, thus making it very costly to produce powders tailor made in a narrow size distribution and microstructure. Furthermore, it is difficult to determine the relationships between atomizer operating conditions and resulting powder characteristics. The Impulse Atomization Process (IAP) was developed at the Advanced Materials and Processing Laboratory to produce powders with narrow size distributions. Powders produced by the IAP were reproducible and their sizes could be easily controlled by adjusting experimental conditions. Characteristics of Zn, Sn-Pb, AI-Cu, and Cu powders will be described to illustrate the flexibility of the process to tailor-make powders.

Jan 1, 1994

By Zhang Jianliang, Xu, Zuo, Runsheng, Haibin, Kexin, Jiao

Full oxygen blast furnace iron-making is one of the new technologies, which is most likely to realize large-scale application. In this paper, based on the technology of full oxygen blast furnace, the reduction behavior of pellets is studied systematically by using the analytic method of non-isothermal dynamics on the different atmosphere(CO,H2) and the dynamics model of gas-solid reduction reaction is constructed, which lay the foundation of reduction model establishment of full oxygen blast furnace burden. The result shows that the time of pellets which began to react is delayed with the increase of the content of H2. When the temperature is between 650 'C and 1050 'C, the content of H2 in the reduction atmosphere is larger, and the rate of the reduction pellets is larger. The reduction rate changes at 780 'C, and a certain amount of H2 in the reducing atmosphere will significantly improve the reduction reaction when the temperature is above 780 'C. Non-isothermal reduction behavior is controlled by interfacial chemical reaction and internal diffusion under high reduction potential. H2 ratio in reducing atmosphere increased from 0% to 100%. The reduction reaction of the apparent activation energy decreased from 49.03kJ-mor1 to 33.74kJ·mor1.

Jan 1, 2013

By A. Siegmund, Gerhard Martin

The recycling of metal containing scrap is a common practice in the industry and has a long tradition. . In rec~nt years, this philosophy has been transferred to organic materials, in particular to thermoplastic polymers. BSB . Recycling GmbH, a company with a long experience in the treatment and recovery of lead from battery scrap,· had recognized this exploitation at an early stage and challenged it by a consequent continuation of the idea to recycle materials other than metals without degradation and maintaining the quality. These efforts resulted in an economic and environmentally acceptable solution producing high quality polypropylene compounds at BSB beside lead and lead alloys from battery scrap. The raw material fair the production of polypropylene compounds is shredded plastics from the separated casings of spent lead-acid batteries. The production of polypropylene with specific physical and mechanical properties is carried out by the accurate dosing of organic as well as inorganic additives. The result of the procedure is a novel product group "Seculene PP", a registered trademark of BSB Recycling GrnbH.

Jan 1, 2000

By G. H. Khoe

Although some hydrometallurgical process liquors contain significant amounts of ferrous and arsenate ions, no reliable thermochemical data for the aqueous complexes and the solubility of the ferrous arsenate precipitate are available. The complexation of iron(11) with arsenate has been investigated using the potentiomemc titration method. The results indicated that virtually no complexation of iron(@ with arsenate has been observed. This is in contrast to the significant complexing reported for iron(1n) with arsenate. The solubility product of the precipitate was calculated using the concentrations of appropriate arsenate species pertaining to the observed precipitation pH's. The fit of the observed precipitation points on the solubility curve of the computed stability diagram was used to assess the appropriateness of the equilibrium model.

Jan 1, 1991

By Martin B. Schranz

Copper sulfate pentahydrate is recovered from the spent etchant waste stream of a printed circuit board manufacturing facility by cooling crystallization. The fluidized bed crystallizer contains submerged cooling surfaces which are bathed in a stream of air. The air bubbles provide agitation which improve heat transfer, reduce fouling and maintain crystals in suspension. The recently patented apparatus (US 5,523,064) has advantages when compared to a conventional surface cooled crystallizer including capital cost, ease of operation and production of larger more uniform crystals

Jan 1, 1997

By A. Valenzuela

During the last years, Chile has been the largest copper producer, either as concentrates or cathodes. Copper obtained via pyrometallurgy is produced by seven smelters, which have carried out modernization plans to increase smelting capacity or to achieve environmental regulations established in the Chilean legislation. Thus, the present work updates technological innovations in smelters, environmental regulations and presents solutions for S02 handling, particulate matter and arsenic. Also, the authors emphasize the important role of CODELCO Chile, the most important state-owned copper company, in developing technologies such as El Teniente Converter and El Teniente Slag Cleaning Furnace.

Jan 1, 2003

By Halvor Dalaker, Pål Tetlie

The decomposition of methane has been studied experimentally in contact with various oxides at elevated temperatures. For each oxide, the temperature at which the cracking starts has been determined. No correlation was found to exist between the temperature for the onset of cracking for a given oxide and the affinity for carbon of the oxide's metallic component. In terms of potential for using methane as a reducing agent, calculations are presented that indicate that the suitability of an oxide for such reduction depends on the desired methane+oxide reaction being more energetically favourable than the methane+methane=ethylene/acetylene reactions.

Jan 1, 2014

By Fashina Olugbenga Emmanuel, Ghazali Akeem, Adegbola Adekunle Amos, Omotoyinbo Joseph Ajibade, Olaniran Oladayo

"Modern engineering materials are required to be light weight and corrosion resistant, coupled with high strength and hardness. In this work, Al formed the parent metal and alloyed with 2.03% of Copper by sand casting process. The cast product 2024 was warm worked at various temperatures ranging from 300 to 5600c at 5%, 10%, 15% and 20% deformation respectively and aged accordingly. The results showed that the mechanical properties vis-à-vis hardness, tensile improved with increasing % deformation at a higher temperature. This was due to the progressive close-up of the voids emanated from casting by increasing deformation which is evident from the micrographs. MATLAB was also adopted to generate a model capable of determining the trend of flow of stress at operating temperatures. This was of immense value due to an increasing impact at higher percentage deformation with temperatures. Hence, Al -alloys will find applications in land vehicles, ships, trains, and aircraft, at elevated temperature.INTRODUCTIONThe problem of safe vehicle design with maximum impact energy absorption is a significant subject in structural crash worthiness design [1]. All engineering designs are expected to ensure the safety of users' life. This informed several studies meant to probe the causes of component failures in equipment, vehicles, and aerospace design and decide on appropriate solutions through materials selection techniques. A common example is in the design of crankcases and heads, piston, and cylinder blocks. As with engine blocks, cylinder heads can be made of Cast Iron or Aluminium Alloy. A head made of Aluminium alloy is lighter in weight than if it were made of Cast iron [2]."

Jan 1, 2013

By Shaolong Chen, Carl-Gustav Berg, Hannu Mansikkaviita

Kumera Steam Dryer has been developed particularly for nonferrous metal concentrates with steam as heating source generated from waste heat boilers. Its unique structure enables the dryer to work at high capacity, up to 240 t/h, and high availability, over 95%. With half a century of engineering experience, and more than twenty industrial steam dryer installations worldwide during last 15 years, Kumera has demonstrated significant benefits of the steam drying technology in terms of energy efficiency and emission reduction to the end users. The dryer of this type can also be applied for other suitable mineral materials.

Jan 1, 2015

By Michael D. Odekirk

The U.S. Bureau of Mines investigated solvent extraction methods for recovering scandium from water leach filtrates of sulfated tantalum tailings. These complex solutions typically contained 20 or more metals in significant quantities. Two commercially available organics, DEHPA and PC-88A, were identified as effective scandium extractants. The two organics were tested in continuous solvent extraction circuits to compare loading and stripping kinetics, recyclability, and general processibility. Results showed that 95 pct of the scandium, greater than 80 pct of the zirconium, and only small amounts of other solubilized metals were extracted. Scandium was stripped directly as a 3.6 pct Sc precipitate when a 3n NaOH liquor was used as the stripping agent. This precipitate was subsequently upgraded to 94 pct ScE3 via a selective HE leach.

Jan 1, 1993

By Y. H. Wang, S. Kou

"Three-dimensional weld pool convection was computer simulated using dimensionless variables. The electromagnetic force, the buoyancy force and the surface tension gradient on the pool surface were treated through the use of the dimensionless electromagnetic force, the Grashof number and the Marangoni number. Other typical dimensionless numbers such as the Prandtl number and the Peclet number were also used. The calculated and experimentally observed fusion boundaries were compared. The convection patterns were shown and the effect of the Marangoni number was demonstrated. IntroductionSeveral weld pool convection models have been developed by Oreper et al. (1,2), Chan et al. (3) and Kou et al. (4). These models describe two dimensional convection in stationary weld pools in a semi-infinite workpiece. Since the vast majority of arc welding practices involve a moving heat source and weld pool, and the workpieces are finite in thickness rather than semi -infinite, a 3-D convection model for a moving heat source and a workpiece of finite thickness is expected to be much more useful.Weld pool convection can strongly affect the structure and properties of the resultant welds. Variations in weld characteristics which are likely to occur from changes in weld pool convection are: weld penetration, macrosegregation, gas porosity, solidification structure, undercutting and surface smoothness. Apparently, the quantitative understanding of convection and heat flow in weld pools is of considerable practical interest. Mathematical models describing convection and heat flow in weld pools are essential, not only because of the quantitative understanding they provide, but also because of the difficulties associated with the experimental measurements of weld pool convection. These difficulties are mainly due to the fact that only surface flow, rather than the overall convection pattern in the weld pool, can be observed. In fact, due to arc glow even the observation of surface flow can be rather inconvenient."

Jan 1, 1986

By Gökhan Demirci, Ishak Karakaya

"Energy consumption in electrolytic magnesium cells is well above the theoretical values. However, the mechanism of the back reaction, the main cause of the current losses, has not been fully understood yet. Magnesium dissolution into the melt is generally regarded as the limiting step for the back reaction. Accordingly, present cell designs are made with priority given to fast magnesium removal from the cell. However, experimental data and modeling results in this study indicate that the limiting step for the back reaction between magnesium and chlorine is the chlorine dissolution into the electrolyte when physical contact between electrolysis products was eliminated. Effects of chlorine bubbles on the current efficiency and the cell potential were investigated. Results show that the extent of back reaction is proportional to the chlorine surface area in contact with the electrolyte per unit time, and the cell potential increases with the amount of chlorine bubbles inside the electrolyte.1. IntroductionMagnesium is less dense than the electrolyte in electrolytic magnesium production. Therefore, both electrode products, magnesium and the chlorine gas, move upwards inside the molten salt electrolyte during electrolysis. The upward motion of electrode products promotes the most important current loss mechanism, the ""back reaction"". Separation of the highly reactive species; liquid magnesium and the chlorine gas in the cell, to prevent their recombination is one of the main concerns in cell designs. The employment of large inter-electrode distance or a separation wall in early cell designs; decreased the extent of recombination, but increased the cell voltage and energy consumption. Recent cell designs, on the other hand, make use of lifting action of chlorine gas [1,2] by utilizing smaller inter electrode distances to separate the magnesium and chlorine gas faster. Although energy consumption was reduced, but more physical interactions between electrode products make electrolytic magnesium cells still highly inefficient when energy consumptions are compared with the theoretical values. Today, the most efficient industrial cells utilizing high purity feed operate at 10.5-11.5 kWh kg-1 Mg [3-5] and it is considerably higher than the theoretically attainable value of about 6.0 kWh kg-1 [6]. This large gap demonstrates the necessity of more research on physics and chemistry of magnesium cell electrolysis."

Jan 1, 2011