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By J. R. Parga

A shortage of landfill space and growing environmental concerns in Mexico are renewing interest in the recyclability of scrap from automobiles. This work describes a pyroumetallurgical process for the recovery of metallic lead from waste lead paste. Argentopyrite concentrate is commingled with lead paste residue and smelted in a fuming process thereby transferring the precious metals into lead bullion. The process consists of smelting lead paste and argentopyrite, sodium carbonate, and metallic iron at smelting temperatures of about 1100 T. The reaction products are slag and molten lead bullion enriched with precious metals. A major feature of this process is the removal of precious metals from the bullion by means of zinc, whereby a silver-zinc intermetallic compound is formed and floats out of the lead. The recoveries of precious metals are about 98%.

Jan 1, 1996

By K. Sanjay

Factorial optimisation technique has been used to develop regression equations at different time intervals for extraction of manganese from precipitated manganese oxide/hydroxide in sulphuric acid using charcoal as the reductant. The three parameters chosen for a 23 full factorial design were : acid concentration, amount of carbon and temperature. The regression equations were used to predict >> 90% extractions as well as kinetic data.

Jan 1, 1996

By Xu Weimin

The existing copper electrorefining tankhouse of Jinchuan Nonferrous Metals Complex (JNC) was commissioned in 1986 for refining blister copper anodes. Blister copper is produced by reverberating chalcocite separated from converter high grade nickel-copper matter by means of flotation. Special chemical analysis of the anodes shows, a composition of 93.02 - 95.72 % copper, 3.0 - 4.96 % nickel and 0.5 - 1.23 % sulfur. The wide range of composition makes the electrorefining process fairly different from others throughout the world. The initial nickel content of 20 ppm and sulfur 40 ppm or more in copper cathodes are reduced to 8.5 ppm and 11 ppm respectively. Since 1986 the tankhouse has undergone significant evolutionary modifications and implementations to ameliorate cathodes quality desirably. The important fact is that the N-additive was utilized through many studies and pilot and field trials successfully. While our primary purpose is to improve chemical quality of the cathodes, tankhouse capacity is increased considerably and the process is perfected satisfactorily. The tankhouse is described with special emphasis on JINCHUAN PROCESS. The upgrading of our product by the utilization of the N-additive is highlighted. The other aspects of the tankhouse including spent electrolyte treatment and by product nickel sulfate manufacturing are briefed as well. Key words: JINCHUAN PROCESS, anode, cathode, electrolyte, electrorefining, N-additive.

Jan 1, 1993

By M. Okido, O. Takai, Z. Zhao, M. Ishikawa, R. Ichino, K. Kuroda

"Electrolytic method was applied to calcium phosphate coating on titanium plates as an excellent technique for high density and intensive contact of coated films on biomaterials. The effect of H2O 2 as oxidation reagent on coating characteristics was examined to obtain biomineral films. Solution was containing 7.0 X 10·3 mol/dm3 ofCaC12 and 3.0 X 10·2 of Ca(H2PO4)z, kept at 55 ""C. All deposits were hydroxyapatite (HAp) in this study, independent of H2O 2 concentration, applied cathodic potential and solution pH. In the case of H2O 2 addition, an increase in cathode current started at the low potential, namely, ca. -0.2 V (vs. SCE). In contrast, the current increased at more than ca. -1.4 V in the solution without H2O 2 addition. H2O 2 appeared to be an effective reagent for increasing nucleation density and improving adhesion of deposits on titanium plates.IntroductionIn recent years, many researches have been undertaken to develop the techniques of calcium phosphate coating on titanium or bioglass for medical implantation. High density and intensive adhesion of coating are necessary for adding bioaffinity to these materials and for inducing bone morphogenesis on them when implanted in human body.1) Electrolytic deposition has been a newly developed method as high-speed deposition process. By this method, the supersaturation of calcium phosphate can be increased just in the vicinity of metal substrates and the heterogeneous nucleation is promoted on them. In this process, H2O is reduced according to eq. (1) on the cathodically polarized electrode"

Jan 1, 2000

By Xiaobing Yang, Abhishek Lahiri, Animesh Jha

"In the FFC-Cambridge process, the cathodic dissociation of oxide and CO/CO2 production on carbon anode is the basis for metal production in a CaCl2 bath. By using an inert intermetallic anode, the CO2 evolution can be eliminated altogether with acceleration in the electro-reduction kinetics. At present the process suffers from slow reduction kinetics of TiO2 to Ti metal, which can be enhanced significantly by the incorporation of alkali species in the TiO2 pellet at the cathode and in the CaCl2 bath in the presence of an intermetallic inert anode. Nearly full metallization with greater than 99% of Ti metal containing 1500 ppm of oxygen is possible to achieve in less than 16 hours of electro-reduction. Analyses of phase composition and the microstructures morphology in fully metallized pellets revealed the presence of localized solidified Ti layer, indicating that fast reduction process also involved formation of liquid phase as middle stage reaction. In addition, in situ creation of porosity and maintain higher current level during electrolysis process were two key factors to fully reduction of TiO2.IntroductionDuring cathodic dissociation of TiO2 in a CaCl2 bath and anodic evolution of CO2 on a carbon anode, which is the basis for the FFC Cambridge process [1], the rate of metallization slows down due to the formation of CaTiO3 at the reaction interface. Calcium and alkaline earth perovskites are known for their poor electrical conductivity which adversely affects the overall electro-reduction. One of the ways to increase the porosity is via the addition of polyethylene precursors in the pellet or by directly starting from perovskite [2, 3]. The experimental evidences shown in the literature confirm although the speed of reaction increases, but a complete or near complete metallization is not possible by enhancing the in-situ porosity alone, as the insulating perovskite is very slow to decompose under the equilibrium that prevails in the cell. Plethoric evidences on carbon anode show with the current decrease gradually, and finally stabilize at a very low value between 0.2 and 0.4 A, which is a testimony of the presence of perovskite insulating barrier in the current path. Our aim in this paper is to demonstrate the mechanism of enhanced electro-reduction when alkali ions are present in the oxide pellet at cathode and in the bath. We also show for the first time the use of an intermetallic anode for Ti-metal production using the FFC Cambridge process."

Jan 1, 2009

By B. R. Adams

This paper discusses the use of a reacting CFD model to determine chalcopyrite kinetics in a drop tube furnace and to predict the reaction of a chalcopyrite concentrate in the reaction shaft of an industrial smelter. Reacting CFD codes can be applied to determine the consequences of the interaction of gas with particles and therefore improve the ability to derive kinetic parameters that take into account the temperature and oxidation histories that different particles will see. This paper describes the application of such a model to derive improved kinetic parameters for the pyrolysis and oxidation of chalcopyrite. The reaction shaft model includes the effects of turbulent fluid mechanics, entrained flow mixing, turbulent particle dispersion, heterogeneous particle reactions, radiative and convective heat transfer, and' surface and bath deposition rates. Particle reaction and composition characteristics are predicted as a function of particle trajectory and deposition and are used to aid in evaluating shaft performance.

Jan 1, 1999

By Seyed Ahmad Jenabali-Jahromi

In this paper a meshless method called Finite Point Method (FPM) is developed to simulate the solidification process of continuously cast bloom steel in both primary and secondary cooling region. The method is based on the use of a weighted least-square interpolation procedure. A transverse slice of bloom as it moves with casting speed is considered as computational domain. The two dimensional heat transfer equation together with temperature dependent thermophysical properties is solved in the computational domain. The present work is verified in the mold region by the comparison of the surface temperature simulated by FPM and finite volume method (FVM) and also comparison of solidified shell thickness simulated by FPM and measured on a breakout bloom. For secondary cooling region the validation is done by comparison of the surface temperature simulated by FPM, FVM and thermovision measurements.

Jan 1, 2009

By Jesus Gonzalez

Peirce-Smith converters (PSC) are long cylindrical chemical reactors where copper matte reacts with air. Traditionally, air is injected laterally through submerged tuyeres at different subsonic velocities. However, the accumulated experience in steelmaking, particularly in the basic oxygen furnace (BOF) process, shows that the gas bottom injection may improve the mixing efficiency of a liquid pool. The aim of bottom injection is to maximize the copper kinetic energy meanwhile avoiding excessive reactor splashing. When gas is injected from a single orifice at the bottom of a liquid pool, two main gas flow regimes can be identified, bubbling and jetting. In this work, a PSC with bottom air injection is studied by means of multiphase 3D CFD numerical simulations considering multiple air velocities. Special attention is paid to the bubbles and jet formation mechanism. The mixing efficiency is measured by calculating the turbulent kinetic energy of the copper matte.

Jan 1, 2008

By Yosry Attia

Recent emphasis on environmental effects and costs of conventional mining processing, plus success in accelerating bacterial action, suggest that biotechnology be explored for gold ore processing. In our paper, the past experience with organisms in processing gold is reviewed. The use of microorganisms for liberation of gold from sulfide ores as a substitute for fine grinding is discussed. The possibility of accumulation of gold from solutions, such as cyanide solutions, is explored as a potential replacement for such processes, such as carbon-in-pulp or ion exchange. The improvement in engineering technology and kinetics needed to scale-up from laboratory experiments to production scale are outlined.

Jan 1, 1985

By David Van Aken, Arpana S. Murthy, Simon Lekakh, Von L. Richards

"Three heats of 17-4PH stainless steel: with zero, three percent, and seven percent cobalt addition were melted in a 45kg (1 00lb) induction furnace under argon; and cast into no-bake molds and preheated investment shell molds. Specimens were sealed into quartz tubes under vacuum, and homogenized at 1200°C from 2h to 72h. Computational thermodynamics and optical microscopy were used to predict and characterize the microstructures. The lath martensite packet size and the amount of 8-ferrite were observed to be inversely related. A compromise between decrease in segregation and increase in lath martensite packet size was chosen for the optimum homogenization treatment. The specimens were austenitized, quenched, and characterized for retained austenite using x-ray diffraction. Age hardening kinetics were studied at 454°C (850°F), 468°C (875°F), and 482°C (900°F); and, the activation energies for precipitation of copper were calculated. Tensile properties and Charpy V-notch impact energies were measured in the peak aged condition. Fracture surfaces were observed using scanning electron microscopy and Energy Dispersive Spectroscopy. The addition of cobalt was found to be beneficial for the improvement of strength as well as notch toughness.IntroductionSegregation in the as-cast condition is one of the drawbacks of metal casting. This paper presents a study on the homogenization treatment of 17-4 PH cast stainless steel and the effect of cobalt addition on tensile properties and Charpy V-notch toughness. Lattice dilatation studies show that additions of up to 6% Co to iron has a negligible effect on the lattice parameter, whereas both the modulus of elasticity and shear modulus increase with increasing cobalt additions5• An ordering reaction has been reported in cobalt-containing, maraging steels and contributes to the hardening during ageing1-4• Although, cobalt addition in maraging steels has been extensively researched, and has been reported to be beneficial; it has not been explored much in other age-hardening stainless steel systems. In a previous study, the addition of 3% Co in cast 17-4 PH martensitic age-hardenable steel was found to improve the strength and elongation while maintaining the charpy V-notch toughness6."

Jan 1, 2011

By Katsuyoshi Tatenuma

"In order to mitigate the effect of global warming by preventing the accumulation of atmospheric CO2, a permanent fixation method of surplus CO2 as an insoluble mineral onto the sea bottom is proposed. As the proposed reduction method of atmospheric CO2, the concrete concept of this method is to form an insoluble carbonate mineral (CaCO3) by direct electrolysis of the seawater; Ca2++2HCO3 -+OH- ? ?CaCO3(insoluble)+CO3 2- (soluble)+H++H2O <not as coral reef reaction>, are directly disposed of itself onto the sea bottom. By this treatment, a concentration of carbonate is reduced in the section of superficial seawater, and therefore the absorption capacity of atmospheric CO2 increases depending upon the shift of chemical carbon equilibrium between the mass of superficial seawater and the atmosphere. As no additives are required, or no secondary waste are produced, the proposed method assuming as green-orientated, has possibility to resolve fundamentally the problem of global warming in a green orientate manner.IntroductionRecently, the amount of atmospheric CO2 has been exponentially increasing and it is a main greenhouse effect gas causing the global warming [1, 2]. The concentration of atmospheric CO2 has increased more than 30% (370ppm in 2001) during only last two centuries, therefore approximately 750 Gton-C of CO2 currently exist in the atmosphere, in which 180 Gton-C of CO2 are accounted for the increment during two centuries [1, 3, 4]. In order to avoid the progressive increase of CO2 global abundance, 3 Gton-C of the incrementing amount per year [4], have to be removed annually from the atmosphere."

Jan 1, 2008

By Suzzann Nordwick

Over the past decade, significant advances have been made in the development of sulfate-reducing bacteria (SRB) technology to treat acid mine drainage (AMD). Bench-scale testing, field demonstrations, and engineered applications of SRBs for the treatment of AMD will be presented. Designs include an in situ bioreactor installed in the subsurface workings of the Lilly Orphan Boy Mine in 1994, the SRB bioreactors installed at the Calliope Mine from 1998 to 2001, the integrated biological reactors built at the Surething Mine in 2001, and the ongoing development of a replaceable cartridge system. SRB technology benefits include the reduction of dissolved metal ions to insoluble metal sulfides and the neutralization of the AMD resulting from the production of bicarbonate from the oxidation of organic nutrients. This paper will address engineering design criteria including the selection of organic media and system permeability and complete mitigation of AMD. Research was funded under Interagency Agreement No. DW899388-70-01-1 between the US EPA and the US DOE and was conducted by MSE Technology Applications, Inc., through the National Environmental Technology Laboratory (DOE Contract No. DE-AC22-96EW96405) at the Western Environmental Technology Office located in Butte, Montana.

Jan 1, 2003

By Pinakin C. Chaubal

Today?s steel industry is in a vibrant and resurgent mode. This transformation has been in the making for some time now. Over the last few decades, the industry was steadily transforming itself into becoming a high tech industry. New technology was adopted, efficiencies were enhanced, lean manufacturing concepts were brought in and a strong customer focus was developed. Today?s mills employ sophisticated instrumentation, computerized monitoring, on-line smart systems etc. driving processes that are producing at rates of many tons/minute. All this is not possible without judiciously using the latest available technologies in various fields and developing a more sophisticated work force. Prof. Sohn has been a pioneer in driving the concept of process engineering in process metallurgy. In this paper the focus is on some aspects of process engineering ? primarily process modeling - as applied to iron and steelmaking processes. Examples are shown to demonstrate how problems have been addressed. Some thoughts on future directions are presented.

Jan 1, 2006

By Wenjun Duan, Zongliang Zuo, Qingbo Yu, Qin Qin, Junxiang Liu

Moving bed has been widely used in the field of heat and mass transfer and reaction between solid particles and gas. In order to enhance the heat exchange coefficient, there will be tube banks inserted in the moving bed. In the process of drying ammoniates particles or heat recovery from high-temperature particles with moving bed, the particles flow behavior around the tube banks is significant. In this paper, the particles flow behavior around the tube banks is investigated, and all the results can provide guidance for the design and operation of a moving bed.

Jan 1, 2016

By Sheng-li Wu, Guo-liang Zhang, Bo Su

The mineralogical characteristics of iron ores can influence their high temperature sintering performance. In this study, eight iron ore samples from Brazil, Australia, and South Africa were characterized by their chemical composition, mineral types, particle morphology, and gangue dispersity. Meanwhile the influence rules between the mineralogical characteristics and the high temperature characteristics were evaluated and analyzed. The results showed that the effect of SiO2 on assimilation characteristic of iron ores was relatively complex, Al2O3 and LOI of iron ores had negative correlation with assimilation temperature of iron ores, the dense slab-flaky mineral granule restrained to the assimilation characteristics of iron ores; liquid phase of iron ores with high SiO2 content and low Al2O3 content had high fluidity, and the higher dispersity of gangue minerals in iron ores was good to the fluidity of liquid phase.

Jan 1, 2015

By Byung-Su Kim

The recovery of elemental sulfur from sulfur dioxide has important implications for coal- burning power plants and nonferrous metal smelters. The thermodynamic analyses showed calcium sulfide to be suitable for recovering elemental sulfur from sulfur dioxide. At the temperatures of 1023 to 1153 K under the sulfur dioxide partial pressures of 5.0 - 60.1 kPa, elemental sulfur from sulfur dioxide was recovered by its reaction with calcium sulfide. The kinetics of this reaction were measured at the same conditions using a thermogravimetric analysis technique. This reaction scheme would be attractive if the coproduct calcium sulfate can be reduced to regenerate calcium sulfide. This is the topic of another paper. At 1073 K under the sulfur dioxide partial pressure of 25.8 kPa, 48 % of the original calcium sulfide was converted to calcium sulfate in an hour. Under the same conditions, 55 % of the regenerated calcium sulfide were converted to calcium sulfate in an hour even after third regeneration.

Jan 1, 1999

By Eric J. Grimsey

Nickel smelting and converting can be viewed as processes in which iron is either partitioned or transported between matte and slag. Metal recovery depends on the mass of iron transported to slag, the thermodynamic environment in which the transport is made, and the extent to which the slag, once formed, is left in contact with the matte. The importance of these effects is discussed with reference to a new equation which describes metal recovery in terms of a mass balance and a thermodynamically related parameter which is easily measured in practice.

Jan 1, 1993

By Hiroyuki Matsuura

The effects of P2OS or Na2O addition on the reaction rate of CO2 dissociation on the surface of FexO-base molten oxides was investigated at I 773K by isotope exchange method 1-6. The rate constant decreased with increasing P2Os content of molten oxides and the residual rate constant was observed at high P2OS content. On the other hand, the rate constant increased with increasing Na20 content for FexO-SiO2 melts, The rate constant was evaluated by the composition of oxides and the rate controlling step of CO2 dissociation was discussed.

Jan 1, 2003

By L. Katgerman, H. J. Brinkman, J. Duszczyk

"The phase formation sequence in the in-situ synthesis ofTiB2 in A1 from elemental A1, Ti and B powders is identified with a combination of DSC and XRD. After the melting of A1, A1B2 and A13 Ti are formed at the contact areas between A1-B and A1-Ti. The influence of variations in starting composition on the reaction kinetics is explained in terms of there effect on the different processes in the formation sequence. Parameters in the starting composition that were investigated are; fraction ofTiB2 forming reactants, non stoichiometric Ti:2B ratio's, and addition of alloying element Cu.It was found that a liquid Al phase is necessary for the in-situ TiB2 forming reaction from the intermediate A1B2 and A13 Ti phases. If all Al is consumed by the formation of A1B2 and A13 Ti the TiB2 formation is halted until the decomposition of A1B2 and A13 Ti .Overstoichiometric amounts of B are needed for complete conversion of the Ti, present in A13Ti, into TiB2 This is explained by the fact that some of the stable A1B12 phase is formed after the decomposition of A1B2•The addition of Cu leads to an increasing reaction rate in the A1-Ti reaction. A possible explanation for this is that the A1-Cu liquid penetrates more easily between the Ti and its surface oxide than the unalloyed A1 liquid."

Jan 1, 1998

By Dae Jin Ha

Sticking phenomenon occurring during hot rolling of two STS 430JlL ferritic stainless steels was analyzed by hot-rolling simulation tests. The sticking started from the initial nucleation stage in which the rolled materials were stuck onto the roll specimen surface, proceeded to the growth stage in which stuck fragments grew further, and reached the saturation stage. The modified 430JlL steel had a smaller number of sticking nucleation sites and slower growth rate than the conventional 430JlL steel because of higher high temperature hardness, thereby leading to less serious sticking. When the simulation test was conducted at 1070 °c, Cr oxides were formed on the surface of the rolled materials, and thus the sticking was drastically reduced because of the increased surface hardness of the rolled materials. In order to prevent the sticking, high-temperature properties of the rolled materials should be enhanced when rolled at 900°C or 1000 °C, and rolling conditions and alloying compositions, under which the oxide formation was promoted, were more important than high-temperature properties when rolled at higher temperatures than 1000 oC.

Jan 1, 2008