Search Documents

By Jason H. Nadler, Jason A. Kulpe, Stephanie J. Lin

"A numerical method has been developed to predict the microstructural characteristics of reticulated metal foam. The porosity of this foam is derived from sacrificial template particles of known particle size distribution, which are incorporated with other precursor components. In this approach, a porous structure is numerically generated starting with Powell's sphere packing algorithm. The resulting stochastic structure has characteristics similar to those of corresponding metal foam. Deterministic inter-sphere connections are calculated to more accurately model the pore morphology that evolves during thermochemical synthesis. Estimations of pore morphology and specific surface area of the simulated material are compared to lab-synthesized materials composed of equivalent constituent compositions. In addition, the effect of template particle size, inter-sphere connections, and the geometric constraints on pore morphology and permeability are investigated to refine microstructural evolution and design.IntroductionReticulated foams, characterized by their interconnected pore network, can be obtained by incorporating spherical sacrificial template particles into precursor materials followed by template removal processes. The resulting structure is composed of contiguous spherical pores whose morphologies reflect those of the original templates. Based on some of the unique features of this synthesis approach, a methodology is introduced in this work whereby these foams are digitally constructed using experimental data from the template particle sizes and precursor formulation. Digitally constructed porous structures can then be compared to their laboratory synthesized counterparts through the quantification of structural features such as porosity and surface area per unit volume, which in tum are used to inform the foam's fluid transport propertiesThe spherical template particle packing algorithm developed here is adopted from Powell's work [1], which also includes approaches to obtain percolation and density in random packings [2]. Gervois gives a mathematical development for the stereological sectioning of packed hard spheres [3]. Stereological sectioning facilitates determination of relevant three dimensional morphological properties from two-dimensional data [4]. Studies on the sphere distribution size and the related particle packing density and coordination number results are studied in [5, 6]. Lastly, Kato describes a sintered neck structure, which is used with these packings [7]. This neck structure, as a model of the particle shape following heat treatment, is implemented here in a similar manner. A strong difference between the available literature and the methodology here is that spheres are packed to ultimately represent porous space, not rigid solid space."

Jan 1, 2011

By B. S. Terry

Experiments have been conducted to assess the feasibility of capturing bearing emissions arsenic with CaO during the roasting of enargite (Cu3AsS4). Enargite/CaO mixtures have been heat treated in air, nitrogen or oxygen for various times and the products of reaction analysed by X-ray diffraction and cleaned analysis. The results show that substantial capture of arsenic can be achieved via the formation of calcium arsenates and/or calcium arsenides. In addition significant capture of sulphur is achieved by the formation of calcium sulphate andlor sulphide. Complete conversion to copper sulphide with total removal of arsenic can be achieved within 30 minutes at 700°C. Further heat treatment in air or oxygen leads to the formation of copper oxide and copper oxysulphate. Without optimisation of reaction conditions, it has proved possible to achieve retention of in excess of 85% of the arsenic content of enargite in the form of calcium arsenates.

Jan 1, 1994

By Jyri Talja, Shaolong Chen, Hannu Mansikkaviita

"Drying (water removal) prior to smelting is always economically feasible. Unnecessary heating of vapour can thus be eliminated resulting in savings of5-15 MUSD every year.Thermodynamically removal of one ton of water out of copper concentrate at 100 °C (with 10 % moisture) requires approximately 3150 MJ/tH2o, consisting of heating of the water (377 MJ), heating of the concentrate (509 MJ) and water evaporation (2260 MJ). This is quite independent of the selected drying technology. In reality some more heat is needed as higher temperature is practiced to enhance the drying performance and to reduce the equipment size.Major nominator in drying energy efficiency is amount of gases, which depends greatly on the drying technology. Dryers based on direct heating with fossil fuels have high gas flow rates, and thus they require additional energy of about 1400-1600 MJ/tH2o, compared to indirect modemsteam drying at 250-400 MJ/tH2o.Significant benefits in energy consumption (900-1300 MJ/tH2o) with additional potential for a bonus profit of 2-4 MUSD/y year, together with full elimination of some 40 000 tpy CO2 per mid-size dryer is available by selecting sustainable, energy efficient steam drying.IntroductionRemoval of water from the concentrate is very energy intensive thus having a significant environmental impact. However, drying prior to smelting is always economically feasible and very often viable also from the perspective of process operations. This environmental impact of drying can, however, be decreased or even fully eliminated with proper selection of the drying technology.Energy incorporated in drying consists always of a number of phases like liquid (water), solids (concentrate) and gases (water vapour, purging I dilution air, combustion gases). Each phase is heated to a specific temperature during the drying process.Heating of water, heating of the concentrate and water evaporation consumes more or less the same amount of energy despite of the drying technology (3150 MJ per ton of water). In conventional drying this amount of energy is achieved by combustion of fossil fuels wirg subsequent CO2 emission. Alternatively, chemical energy derived from sulphide smelting can be utilized in a form of steam thus generating zero emission ofCO2, in modem steam drying."

Jan 1, 2012

By Masaru Imaizumi, Hiroyuki Nomura, Mitsuharu Takita

"Cast iron possesses many superior characteristics caused from precipitated graphite structure, for example, castability, wear resistance, solid lubrication, damping capacity. But the more graphite hyper-eutectic cast iron contains, the lower its mechanical strength becomes, because graphite gives a negative effect to strength of cast iron. In addition, primary graphite tends to segregate during solidification, so uniform materials are difficult to be produced.In this study, authors introduced semi-solid processing in developing new and high quality cast iron. A series of semi-solid processing experiments were carried out to clarify the effect of stirring condition; solidification temperature and etc. on microstructures and characteristics of cast iron. In particular much attention is paid to the appearance of ternary eutectic zone at the final stage of solidification. As the results advanced hyper-eutectic cast iron was obtained with high quality of both the mechanical strength and wear resistance. As for the mechanical strength, 300MPa and 0.60% are obtained as the tensile strength and the elongation values, respectively, under the controlled stirring condition. This indicates that semi-solid processed hyper-eutectic cast iron is used prospectively without spheroidization.IntroductionCast iron has various good properties such as wear resistance, solid lubrication, damping capacity and machinability. The characteristics of cast iron are mainly decided by graphite structure, namely graphite shape and its distribution in the matrix. Mechanical strength of cast iron is large in the case of small quantity of graphite particles which are precipitated uniformly, however, it becomes small in the case of large quantity of graphite precipitated flakily."

Jan 1, 2000

By Yafei Xiong, Yue Wang, Guotao Xu, Shuzhong Li, Huaiyuan Li

"The composition, properties and structure of taphole clay with high strength and friendly surrounding used in a new blast furnace with 3800 M3 volume was studied. The developed taphole clay had been applied in the blast furnace for four months, pouring times were 11-13 every day, flowing rate of hot iron was 7.5 t/min and the consumption of taphole clay was 0.49Kg per ton iron, which can make the new blast furnace attach the designed production quickly and decrease the cost of hot iron. The taphole clay is easy to be opened in the channel of hot iron which can be remained in stable shape under the corrosion of slag or hot iron, and it dose not produce poisonous smoke in yellow or dark color in the use process. The development of new taphole clay is useful to improve the work surrounding of the blast furnace.IntroductionIn the iron-making process, the taphole clay's function is filling up the taphole and protecting the formation as well as the growth of the clay in the blast furnace, maintaining the enough taphole depth; simultaneously it is easily to open a hole and knock out the clay. The taphole clay has a good performance of molten slag and hot iron resistance. The traditional taphole clay uses coal tar or carbolineum as a binder, and the performance of taphole clay is good, but it has the black and yellow poisonous smoke, which is harmful for work condition. Through the investigation on the binder's composition and poisonous performance of taphole clay, the environmental taphole clay is developed by some foreign companies, which is named the third generation product with benzene is less than 300ppm, and it has been used in European steel companies. This application of the taphole clay with high strength and environment-friendly using in 3800m3 blast furnace is introduced and the performance is discussed and analyzed in this paper."

Jan 1, 2012

By Jeffrey R. Taylor

The distribution of low concentrations of Cr, Mn, Rh, Co, Ni, Ag and Fe between copper matte and bullion phases has been measured at 1200oC. These results. together with values for nine other elements, have been used to develop a simple model to describe the distributions in terms of known thermodynamic properties?. The Temkin model for ionic melts was assumed to apply to the sulphide species in the Cu-S matte? phase and it is shown that the choice of sulphide species is particularly important for successful representation of the experimental .results?. In general, the lowest sulphlde (minimum sulphur :. metal ratio)? formed by the. metal is most suitable, although Ni, Co, Rh and Pd appear to associate with more sulphur in the melt than suggested by the? composition of their lowest sulphide. A correlation between the composition of the metal sulphide species formed in the ternary system and the? position of the minimum in the free energy of mixing curve in the metal-sulphur binary -system is? proposed.

Jan 1, 1983

By L. A. Harris

The formation of coke during coal liquefaction can eventually result in catastrophic failure of the conversion system. Coking typically proceeds by the formation of liquid crystals (mesophase) and the subsequent separation of these crystals from the plastic phase formed during heating of coal. The anisotropy of the mesophase makes it readily detectable in the optical microscope under polarized light. This study examines the solids formed during coal liquefaction processing by optical and electron microscopy. Observations on the relationships between the coke morphology, minerals and inert macerals are presented.

Jan 1, 1982

By I. D. Reznik

The flowsheets of converter matte production from sulphide copper - nickel and oxide nickel ores on Severonickel and Yuzhuralnickel integrated ,;corks are given. The cobalt behaviour in electrosmelting and autogenous ore smelting, converting and converter slag cleaning is observed. A list of acticles published in the 80 th is given.

Jan 1, 1993

By Kazuteru Tozawa

Surface tension, density and viscosity coefficient of acidic copper sulfate solutions simulating electrolyte solution for electrolytic production of copper have been measured and are summarized as a function of the solution composition and temperature. Nickel sulfatc is taken to be a representative coexisting sulfate that affects the physical properties of the copper sulfate electrolyte solution. The sulfates in the solutions, including sulfuric acid, increase the physical properties under consideration. Gelatin, representing organic additives for electrolyte solution, was found to sensitively affect the surface tension of the solution at low concentration of up to 200mgIL. The surface tension was markedly lowered by the addition of gelatin and the increasing concentration of gelatin led to a more pronounced decrease in the observed values. The surface tension gradually increases with time after addition of gelatin and the increase is enhanced by higher acid concentration and higher temperature. The observed change in the surface tension is considered to reflect the preferential adsorption of gelatin to the bubble-solution interface and the decomposition of gelatin due to hydrolysis to form various molecules having smaller molecular weights.

Jan 1, 2003

By Filipe de Menezes Torres, Augusto Pereira de Sa, Itavahn Alves da Silva, Eliana Ferreira Rodrigues, Carlos Antonio da Silva, Varadarajan Seshadri

Top slag eye opening which happens as a result of gas injection is a function of the gas flow rate in addition to other factors such as ladle geometry, porous plug location as well as slag properties. Slag eye opening leads to entrapment of atmospheric nitrogen, oxygen by the steel melt affecting adversely the steel quality. In this work aspects of mixing and eye formation in steel making ladles with inert gas injection have been analyzed through physical and mathematical modeling techniques. Influence of ladle, gas flow rate and distribution and slag properties has been assessed. A correlation for estimating eye opening has been developed. Results from PIV measurements and images of eye opening obtained using a camera have been utilized to validate results from CFD simulation.

Jan 1, 2015

By I. M. Ritchie

Cyanide owes its great success as a lixivant for gold to the great strength of the Au-CN bond. A replacement for cyanide must similarly be a strong complexant for gold (I) or gold (III). The various alternatives are briefly considered and it is concluded that only thiosulfate has a reasonable chance of replacing cyanide as a relatively non-toxic lixivant at the present time. However, there are considerable technical problems to be overcome before thiosulfate can be considered to be a realistic alternative to cyanide. Firstly, the leaching of gold using aerated ammoniacal thiosulfate with copper as a catalyst is a complex process which needs to be understood and controlled carefully in order to achieve maximum recoveries with minimum reagent losses. Secondly, there needs to be an option similar to the CIP process for recovering and concentrating the dissolved gold thiosulfate complex from pulps produced in the processing of low grade gold ores. The prospects for overcoming these technical' challenges are evaluated and discussed.

Jan 1, 1998

By Hector M. Henao

To provide thermodynamic data for converting nickel matte to liquid nickel at high temperature, an experimental study was conducted on the phase equilibrium between the Ni-S alloy and the FeOX-SiO2, FeOx-CaO, and CaO-A12O3 base slag in a magnesia crucible and the CaO-Al2O3-MgO slag in an alumina crucible. All experiments were carried out at 1773 K under controlled pso2 of 0.1 atm and po2 in a range between 5x10- and 10-5 atm by using CO-CO2-SO2 gas mixtures. The dissolution of nickel in the slag was found to be minimum for the CaO-Al203¬-MgO slag with a molar ratio of NCaO/NA1203=1.7. The solubility of nickel in this slag at p02 of 6x10 atm (just before the precipitation of solid NiO) was 4 mass%. This result suggests that a CaO-A12O3 base slag could be used in converting Ni-S melt to nickel while minimizing nickel losses to the slag.

Jan 1, 2002

By Akira Yazawa

In the field of pyrometallurgy, the equilibrium evaluation has recently become easy by use of thermodynamic software, but it is strongly desired to estimate the amounts of non-equilibrium minor components to simulate practical processes. However, simple physico-chemical technique can not be applied to evaluate practical non-equilibrium components for many reasons. As an engineering solution for postulated equilibrium system, the activity coefficient is modified and introduced as the simulation parameter referred to as the "adjustment coefficient." This modified thermodynamic calculations were adopted to various sulfide roasting processes where many solid phases are participating and the system is not necessarily in equilibrium. Successful simulation was realized by assigning suitable adjustment coefficients for minor components which form a pseudo solid solution in the calcine. Some examples from sulfation roasting and dearsenizing roasting were discussed. In the smelting system, the loss of copper in slag is caused by equilibrium and non- equilibrium reasons, that is, chemical dissolution and entrainment of copper in slag. The total copper content of slag was simulated by use of the adjustment coefficient for entrained copper.

Jan 1, 1998

By Denise C. R. Espinosa

Rechargeable lithium batteries are one of the most promISIng technology in battery development. Although Li ion batteries have been used as an alternative to the more polluting and less performing Ni-Cd batteries, Li ion batteries have limited life and their disposal is uncertain. It is imperative that valuables from wastes, such as lithium, should be recovered. The main objective of the present work was to characterize secondary lithium batteries for cellular phones. This was done using unit operations of mining processing, x-ray diffraction (XRD), chemical analyses and the rmogravimetric analysis (TG). The unit operations were hammer mill grinding, knife mill grinding, size separation and magnetic separation. After the hammer grinding process, the plastic cases were almost intact, however, they have released the cylindrical lithium batteries themselves and these parts correspond to 70% of the total battery weight.

Jan 1, 2001

By Rodney Hundermark, July Ndlovu, Lloyd Nelson, Phillimon Mukumbe, Paul van Manen, Whitey Seyanund, Bart Pieterse, Bertus de Villiers, Diale Mokwena

The 2003 redoubling in power to 68MW on the Polokwane Smelter furnace represented a significant intensification in platinum group metal (PGM) smelting. Combined with onerous ‘green’ PGM concentrate smelting requirements, this yielded conditions unusually corrosive to copper coolers and refractories. This presented unexpected operational and design challenges to reliable crucible operation and maintenance. Combined with specific operational control intervention, development of protective coatings has led to the life of water-cooled copper components improving from 9 to 40 months. The furnace matte endwall was extended in 2010 to address accelerated wear of refractories and the potential risk for contact of copper components by superheated matte. An 18 month planned endwall rebuild cycle has been demonstrated (versus catastrophic failure within 9 months). Finally, benefits including lower energy consumption, improved metal recoveries and higher productivity resulting from operational and in-house design developments will be described, that justify “Celebrating the Mega-scale” in PGM smelting.

Jan 1, 2014

By José Carlos Abreu

This work presents a kinetics study covering the effects of temperature over the reduction rates of a carbon composite briquette, aiming its use as burden in some of the new alternate ironmaking technologies, such as the Tecnored process. It is reported that increases in the temperature increases the reaction rate. Additionally, the morphology of the iron phase generated during the reduction of these briquettes is presented. It was possible to verify that three types of iron morphology occurred during the process: an external, dense and continuous iron layer, the presence of iron globules at the center of the briquettes and whiskers at the briquette's core. The measurement of the carbon content on the globules and the external iron layer is also presented

Jan 1, 2003

By László I. Kiss, Verena Mackowiak, Alexandre Perron, Dominic Toulouse, Alicia Liedtke, Sándor Poncsák

"Bubbles play a very important role in different metallurgical applications like for example in electrowinning. During heterogeneous nucleation, the maximal size of the bubbles growing at the nucleation sites as well as the nucleation frequency is determined by the so-called detachment condition. Detachment occurs when the external forces acting on the bubble exceed the retaining forces along the solid-gas-liquid triple interface line. The phenomenon depends strongly on the shape and orientation of the solid surface and on the nature and strength of the external buoyancy and drag forces. In the present study the detachment conditions of bubbles from downward facing horizontal and inclined plates were studied experimentally under the effect of gravitational and hydrodynamic forces. The results show the deformation of the bubbles under the effect of the external forces and the detachment conditions as function of the bubble volume.IntroductionIn heterogeneous nucleation bubbles are generated at the so-called nucleation sites along the solid-liquid interfaces. They continue to grow there and after they reached a certain size they detach from the solid surface and leave the nucleation site. This scenario is well known both in boiling and electrolysis. During the growth period a stable equilibrium exists between the forces that retain the bubble at the nucleation site and the forces that try to remove it. This equilibrium evolves with the increasing volume of the bubble to the point when the detachment forces overcome the retaining forces.The life of a single bubble generated by heterogeneous nucleation can be divided into two periods separated by the detachment - or in other words by the departure - of the bubble: first the growth at the nucleation site and then the movement away. The knowledge of the detachment conditions makes possible the determination of the maximal volume of the bubble at the nucleation site that, in tum, makes possible the determination of the nucleation frequency. This is why so many researches have been directed toward the clarification of the details of the bubble detachment in the past decades. The equilibrium between the attaching and separating forces depend on the presence of body, surface and flow induced forces in the liquid, on the geometry and orientation of solid surface, on the properties of the solid-liquidgas system etc."

Jan 1, 2004

By K A. Pericieous

"Magnetic fields have many actual applications in the metals processing industry. Externally applied magnetic fields give rise to electromagnetic (Lorentz) forces formed by the cross product JxB, between the induced current density J and the magnetic field density B. When the metal is in liquid form, the Lorentz force generates motion in the fluid which in applications of practical interest becomes turbulent. In modelling terms, the Lorentz force appears as a source in the momentum equations. In addition, the induced current generates heat (Joule heating) in the metal that is in proportion to J2, with a corresponding source of heat in the energy equation. Whether as heat or as a force, these effects represent action at a distance - a most useful attribute when dealing with hot metal. The Lorentz force is used to stir solidifying alloys, pump liquid metal in conduits, dampen the flow in the meniscus of a continuous caster, levitate metal drops, induce artificial gravity conditions in suspensions or contain liquid metal. Elsewhere, the Lorentz force may be a by-product of some other operation, so leading to wave excitation in aluminium electrolysis cells, or altering the shape of the weld pool in arc welding. Joule heating is most commonly used with applied AC fields, to melt metal in induction furnaces.The author and his colleagues have been involved in the modelling of most of these processes in the past decade. Modelling is not however straightforward, since most of the examples mentioned represent genuine multi-physics challenges. There is a strong coupling between the flow field and electromagnetic field. The addition of a dynamically varying metal free surface and the moving solidus front means the flow, heat and electromagnetic fields need to be computed simultaneously. In situations involving metal containment, the metal free surface position is governed by the interplay of gravity, Lorentz force, surface tension and fluid inertia. Since all the interesting effects often happen in thin boundary layers at the surface due to the skin effect, mesh generation and mesh control during the computation become non trivial problems that need to be addressed. This paper presents a review of numerical methods used to model droplet levitation, semi-levitation melting and cold crucible induction melting of metals. The first method is based on spectral collocation techniques and the second is the traditional FV approach. Steps taken to validate the computations and typical transient results are also given."

Jan 1, 2001

By S. Redik, C. Wenzl, D. Gregurek, A. Spanring

Zinc is a component of many input materials used in various pyrometallurgical processes, for example primary lead and zinc production from Pb/Zn ores and recycling processes dealing with zinc-containing residues (e.g., copper recycling, WAELZ process). Hence, zinc and its compounds are present in the respective metallurgical vessels and interact with the refractory lining. In the present work the zinc attack on the refractories out of various primary and secondary furnaces is briefly introduced and discussed. At the prevailing processing temperatures in the metallurgical vessels, zinc oxide is highly corrosive for the brick components. The knowledge of the wear behavior is based not only on a detailed chemical and mineralogical characterization carried out on provided post mortem samples, but also on FactSage calculations. This together with results obtained by practical testing in the RHI pilot plant represents an important prerequisite for product development and brick selection for the individual customer application.

Jan 1, 2016

By H. Senoh

For the purpose of clarifying the reason caused a drastic decrease of discharge capacity for MmNi3.6Mn0.4Al0.3Co0.7 electrode at relatively low temperatures, various factors influencing the charge-discharge processes were investigated in the temperature range of 25°C to -40°C. The charge efficiency obviously decreased at low temperatures less than 0°C due to a decrease in the rate of the charge-transfer reaction on the electrode surface. Moreover, both the rate of the hydrogen diffusion from the alloy bulk to surface and the rate of the charge-transfer reaction significantly influenced the high-rate dischargeability. The addition of Mo to MmNi3.6Mn0.4Al0.3Co0.7 alloy was found to be effective for improving the electrocatalytic activity, leading to the improvements of the charge efficiency and the high-rate dischargeability at relatively low temperatures.

Jan 1, 2002