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By Carlos Schvezov, Eliana Agaliotis, Alicia E. Ares, Mario Rosenberger

"The interaction between a solidification front and a spherical particle was modeled and simulated in order to study the phenomenon of ""pushing"". Finite element methods were employed in axisymetric domains. The drag force is calculated from the calculated fluid flow field and the repulsion force is the Lifshitz-Van der Waal force. The thermal field is decoupled from the force field. The model is applied to a metallic matrix containing particles with similar, lower or higher thermal conductivities than the matrix, resulting in planar, convex and concave interface shapes, respectively.The results show that the critical velocities for pushing for concave and convex interfaces are about one order of magnitude larger and one order of magnitude lower than the critical velocity for flat interfaces, respectively. The simulated results were in very good agreement with reported experimental results.IntroductionThe solidification interface of materials containing spherical particles in some cases can push the particle ahead the interface. This phenomenon generally occurs during the solidification of different materials such as, metallic alloys containing native particles, metal matrix composites containing particles or fibers as reinforcements and crystallization of semiconductor, optical, optoelectronic or biological materials. In all cases the interaction strongly determines the distribution of particles and the resulting physical and physic-chemical properties of the resulting material. The phenomenon has been investigated for many years both experimentally and by mathematical modeling [1-21]. The process is complex due to the variety of phenomena involved during pushing. In all cases, the physical problem depends on the properties, nature, and morphology of the interacting media; the particle, melt and solid; and external fields such as gravity, thermal and electromagnetic fields."

Jan 1, 2012

By Klaus Gamweger

There are different reasons for purging a metal bath. The operations are varied, for example the purging gas can be used as a reactive gas being part of the metallurgical process or as an inert gas using the rising gas bubbles for agitation only. The different purposes for agitation, chemical and thermal homogenization or a preferential movement of the slag to the slag skimming door have to be considered. It depends on the furnace type and its dimensions as well as the process characteristics what the focus is on. For an optimized arrangement of numbers and position of all single plugs in the furnace, mathematical modeling - the CFD Computational Fluid Dynamics method - is used. This paper shows how the operation of purging plugs can influence the metallurgical process of an anode furnace by the example of Jinchuan Copper in China. The potentials for savings in energy consumption as well as in time for oxidation and reduction are presented.

Jan 1, 2006

By M. GONZALES-FERNANDES M

Natural rubber/organophilic clay nanocomposites were prepared and characterized. A brown bentonite from Paraiba’s State, Brazil was modified with a sodium salt and treated with quaternary ammonium salt hexadecyltrimethyl ammonium chloride. The clay in its natural state, after cation exchange with sodium and after organophilization was characterized by XRD, IR, SEM, thermal analysis. Nanocomposite samples were prepared containing 10 resin percent of organophilic clay. The vulcanized samples were analyzed by XRD, SEM. The nanocomposites obtained showed improvement in their mechanical properties in comparison with samples without clay.

Jan 1, 2015

By Ho Jung Heo

The proper control of slag composition is a dominant factor affecting yield of iron as well as dephosphorization efficiency in an electric arc furnace (EAF) operation. Moreover, thermophysical properties of slags such as viscosity are strongly affected by the changes in slag composition. Slag foaming, which is also a function of viscosity, is directly connected with the yield of iron and thus optimum slag chemistry are highly required in view of thermodynamics and physical properties. Therefore, we analyzed the slag composition in commercial melt shop (70 ton EAF) with the aim of higher yield of iron as well as higher dephosphorization during EAF process.

By He Zhi-jun, Ning Zhe, Pang Qing-hai, Zhang Jun-hong, Zhan Wen-long

The effect of microwave irradiation on grinding property of coal was studied by using Hardgrove grindability index tester. Superior grindability of coal was obtained to varying extent after microwave irradiation treatment. The variation in microstructure of pulverized coal during microwave irradiation was observed by utilizing scanning electronic microscope (SEM). The results indicated that the different microwave absorbance of minerals and carbon matrix led to cracks on their interface, by which coal particles were further pulverized and therefore the granularity of coal powder was reduced. Due to the different formation process of various coals, bituminite and anthracite are very different in physical and chemical properties. According to the content of coal pulverization, it can found that microwave irradiation has a stronger pulverizing effect on bituminite in comparison to anthracite.

Jan 1, 2016

Bath smelting options for recovering valuable metals from jarositic residues containing 22-28% lead and 16-30% sulphur obtained from pressure leaching zinc-lead-copper bulk concentrates were investigated using thermochemical computations and crucible-scale experiments. Direct fuming of lead and zinc from a slaglmatte bath at 1250-300°C was demonstrated successfully. Up to 93% of the lead was recovered in the fume and steady-state recoveries of zinc were predicted in the range 82-95% under these conditions. The energy required for the fuming reactions was supplied by partial combustion of the fuel, added as char, with air. An important feature of the process is that the recoveries to the fume are not significantly affected by changing: the fuel:air ratio over a wide range. Thermodynamic computations, confirmed by experimental results also showed that the presence of a matte phase is not essential for high recovery of lead and zinc to the fume. Operating conditions which produced a matte ensured that about 70% of the silver and 80-90% of the copper were recovered into that phase. Approximately 98% of the arsenic in the residue was fumed. In the absence of matte the slags contained high arsenic levels (260-330 ppm) but low arsenic (20-60 ppm) levels were achieved when matte was produced.

Jan 1, 1994

By Jorge Alberto Soares Tenório

Electronic components have precious metals like Au and Ag. These metals have a high performance in electric conductance. The recycling of the scrap, however is too difficult because of the presence of other metals like Fe, Al, Zn, Sn, ceramics and plastics, all together in electronic components. The aim of the present work was to define one way for physical separation to have metallic non-ferrous concentrates. It was used three kinds of scrap. I was used conventional equipment for mineral processing like hammer mill; screens, electrostatic and magnetic separation.

Jan 1, 1997

By Pranav Deshpande

The wear behavior of metal matrix composites differs from that of the monolithic metallic counterparts because composite materials have multiple constituents in their structures and these constituents wear at different rates. It was observed that under low wear stresses, abrasive wear prevailed. As the wear stress increases, pullout of reinforcement occurs and both abrasive wear and wear due to pullout contribute to the overall composite wear. A model of wear taking into account both types of wear has been developed. A critical pullout wear stress was suggested for each composite. Below the critical wear stress, no pullout of reinforcement occurs. It turns out that the critical wear stress simply equals to the ratio of the interfacial strength between the matrix and the reinforcement to the friction coefficient between the reinforcement and the wear counter surface. The critical wear stress is independent of the particle size of the reinforcement. From data on wear of 53% WC composites, the equation of wear for 32% WC composites was obtained. Experimental results agreed well with the predicted wear rate of this composites. This provides an excellent verification of the wear model developed by Lin and Deshpande. Wear data from Modi et al. in the literature were also perfectly fitted with the model.

Jan 1, 2006

By C. Twigge-Molecey

All projects that are implemented, have been given corporate go-ahead on the basis of a set of clearly defined targets. These are typically a production goal at a capital cost, operating cost and production schedule, that will yield an acceptable return on investment by the companies internal criteria. The challenge for the implementation team is two-fold, firstly to properly define the project criteria prior to board approval and secondly to deliver an operating facility that meets these objectives, in particular the ROI. The paper addresses the issues a project team and the company management must address for a successful project. Key questions that will be explored are: ? What is the status of key technologies? Are they well proven in commercial practice, completely novel or in between? ? Is the project schedule driven by market constraints or cash flow constraints? ? Are the risks of fast tracking worth the potential rewards? ? For a retrofit project, are all the technical and production interfaces and issues known at the time of approval to proceed? ? How much should be invested in technological development and engineering and at which phase? ? For an owner-operator, how much responsibility is it wise or appropriate to push down to vendors? The answers to these questions for a specific project will define how you go about a project, the resources required, the contracting strategies, the phasing and the appropriate level of investment in the definition and procurement phases, prior to starting major capital commitments and construction.

Jan 1, 1999

By R. W. Hammack

Results for the treatment of a problematic mining wastewater using bacterial sulfate reduction (BSR) are presented. Specifically, a BSR pilot treatment plant (250 L per day) was used to treat Berkeley Pit simulant to discharge standards with the selective recovery of separate Cu- and Zn-sulfide concentrates. Concentrates recovered in these tests contained greater than 50 % of the target metal and met specifications for sale to existing smelters. The biological component of the treatment was found to be surprisingly robust. Scaling and solid/liquid separation problems were encountered but considered normal for sulfide treatment. For Berkeley Pit water, capital costs for BSR treatment was found to be comparable to high-density sludge lime treatment. The value received from the sale of recovered copper ands zinc concentrates paid for all the operating costs.

Jan 1, 1999

By Laurentiu Nastac

"An advanced casting simulation-based optimization approach was applied in this study to assist in the improvement of the mold design of aerospace components made of A3 56 alloy. By using this approach, mold filling and solidification related defects (including macro-shrinkage and shrinkage porosity) were significantly minimized and hence it helped in cost reduction, performance enhancement and quality assurance of complex A3 56 cast parts.An experimental validation and detailed calibration procedures of the models for prediction of macro-shrinkage and shrinkage porosities were performed using A3 5 6 plates cast in fiiran-silica sand molds using the Prometal's Rapid Casting Technology (RCT) - mold printing technology. Correlations between Niyama values and the pore percentage were also developed. Thus, the severity level of shrinkage porosity can be determined via the Niyama criterion. Predictions were then compared with the macro-shrinkage and porosity measurements in plates of various plate thicknesses and in other commercial A3 56 casting components.IntroductionThis paper describes the process modeling approach used in the development of the mold design technology used to produce assist in the improvement of the mold design of aerospace components made of A356 alloy. Nova Flow&Solid™ software [3] was applied in this study. This casting simulation software was previously validated for several alloys including Ti, steel and superalloys [1-4]. The objective of this paper is to calibrate and validate the simulation software for A356 alloy sand mold castings. For this purpose, an experimental validation and detailed calibration procedures of the models for prediction of macro-shrinkage and microshrinkage (e.g., shrinkage porosities) were performed using A356 plates cast in fiiran-silica sand molds using the Prometal Rapid Casting Technology (RCT) mold printing technology. The details of the RCT technology are shown in Fig. 1 [5]. Prometal's RCT technology is used for rapid production of sand molds and cores directly from CAD files. The RCT technology relies upon ink jet printer technology to selectively bind the grains of sand to create three-dimensional sand molds and cores. Mold filling and solidification modeling as well as stress analysis are typically performed to properly design the casting and the rig system of each prototype component."

Jan 1, 2012

By A. M. Strachan

The arising and behavioural pattern of polonium-210 in the Capper Pass & Son Limited non-ferrous metal smelting and refining circuit is briefly discussed. The process developed for the removal of polonium from lead, solder and bismuth is discussed in detail, together with the essential personnel safety and environmental protection precautions which must be taken during the refining and subsequent storage of the active dross.

Jan 1, 1992

By Norbert L. Piret

During smelting of copper, arsenic in the feed reports to a large extent to the gas phase and some enters the anode copper. From the gas phase it is transferred during wet gas cleaning directly, or indirectly after dust processing, to aqueous solution. During the electrorefining and anode slimes processing, the anode arsenic content is also transferred to aqueous solution. Technology for the efficient removal of arsenic from process streams and cleaning of aqueous effluents is well established. However, the arsenic-bearing products, which thereby are generated, can vary widely in consistency, quality and quantity, from large amounts of gypsum contaminated with water-soluble arsenic compounds to residues with high arsenic content ' or arsenic products. Arsenic management in a copper smelter not only is involved with the duty of compliance to the gaseous and aqueous emissions standards but also should have as objective the minimization of the generation of arsenic-bearing and, in general, heavy metal-bearing solid waste. The present paper outlines options and the associated economic aspects for minimization of arsenic-bearing solid waste generation, for improvement of the environmental compatibility of the residues to be deposited and for the .production of commerciable arsenic compounds under appropriate market conditions.

Jan 1, 1999

By P. K. Jha, M. M. Mahapatra, H. K. Mohanty, Pradeep Kumar

"During friction stir welding, the tool geometries affect the weld together with the process parameters like welding speed, vertical pressure and tool rotational speed. The present investigation deals with the three dimensional computational fluid dynamics modeling of friction stir welding process considering material flow around the tool, welding speed with respect to tool geometries. Friction stir welding tools with different tool geometries were used for the experiments to achieve acceptable aluminum welds. The temperatures near the welds for each tool were experimentally observed. A 3-D computational fluid dynamics (CFD) model was developed. Temperature-dependent material properties of the aluminum alloy were used in the CFD model. Thermal analysis was carried out considering rotational speed, vertical pressure and traverse speed for the tool geometries. The numerically predicted stirring patterns and temperature profiles closely matched with the experimental ones. IntroductionThe friction stir welding (FSW) is a solid state welding process where generally the metallic materials are joined by the combined action of frictional heating and weld zone stirring by a rotating tool [1]. The heat generated in the process is much below the requirement of melting the plates; hence the FSW process is devoid of harmful effects those are observed during arc welding. The FSW process utilizes a tool which has a shoulder and a protruding pin known as the probe. The shoulder is responsible for frictional heating while the pin probe facilitates stirring of the joint material. A schematic of FSW process is shown in Fig. 1."

Jan 1, 2012

By Richard LeSar

Sustainability requires more from engineering than the development of technology. Engineering must also take into account the effects of that technology on the integrated social, economic, and environmental processes that constitute our society. Schumacher introduced the powerful concept of an appropriate technology, by which he meant a technology that is appropriate to the environmental, educational, cultural, and economic situation for which it is intended. While the principles of appropriate technology have been most commonly applied in the developing world, they are equally valid in the developed world as well. In this paper we will review appropriate technology and discuss its role in helping to define a way to think about this broad view of sustainable engineering. We will end by presenting one strategy for introducing the concepts and applications of appropriate technology in an engineering curriculum.

Jan 1, 2010

By D. J. Goodwill

BHP Copper operates a 3,400 tpd dry concentrate, single burner, Outokumpu flash smelting furnace (FSF) at their San Manuel copper smelter in Arizona. The very fine (-325 mesh), dry concentrate is fed to the burner from a 550 metric ton (nominal) capacity furnace feed bin via two drag chain feeders. During the 10-year history of the furnace, operations have been plagued by serious flooding problems. The fine concentrate sometimes becomes aerated during discharge from the bin and flows like a fluid at very high uncontrollable rates to the burner. This results in upset conditions at the concentrate burner leading to poor furnace metallurgy. This paper will examine the problems of uncontrolled feed from the furnace bin (i.e. flooding), and' instantaneously feeding a flash smelting burner. It will show that a drag chain is a poor choice of feeder when high rates are needed, and that drag chains always produce a funnel flow pattern in a bin. BHP's drag chains cause narrow diameter, high velocity flow channels within the stored material. Consequently, there is insufficient residence: time for the concentrate to fully de-aerate before discharge, hence flooding occurs. In addition to the flooding problem, drag chains create a pulsating flow to the concentrate burner due to the tendency for material to slough off in discrete chunks at the discharge end of the slow moving chain conveyor. During the scheduled FSF rebuild in May 1999, BHP intends to remove the drag chains, modify the bin to a mass flow design and to use STAMET® multi-disc feeders to accurately and instantaneously control the rate of discharge from the bins. Air slides will be used' to convey the concentrate to the burner.

Jan 1, 1999

By Takashi Yoshida

"This paper will discuss the recent situation and future of the zinc industry from the technical point of view. It includes recent problems faced by the zinc industry and technological developments. One of the biggest problems of the zinc industry is raw materials. Traditional zinc concentrate becomes much complicated with respect to its chemical and physical properties. Thus, each process faced various problems. Also, secondary resources, generating so called recycling processes, become much more important. Recycling is, of course, a very important aspect for sustainable development of society. Secondary raw material also includes a great variety of impurities not included or very low levels in traditional zinc concentrate. Some problems are caused by these impurities. To overcome these problems some technological challenges have been taking place. Details will be discussed in the symposium.IntroductionZinc is a very useful metal based on its elechtro-chemical, chemical and physical properties. The most important usage is galvernizing of steel which is used for automobile, construction and a very wide range of other indutries. Also, zinc is used for dicasting and other alloys such as brass. Smelting of zinc is different from other metal because of its electro-chemical properties. Many parameters should be controled compared with other metals such as iron and copper. Typical zinc smelting processes are the Imperial Smelting Process (ISP) and the electlolytic process. The ISP process is a pyro-metallurgical process using a blast furnace. The electrolytic process is a hydrometallurgical process. Both processes are energy intensive, and the smelting process cost is increasing because of higher energy costs. The situation of the ISP is very severe because of higher coke prices. Recently, many ISP plants have been shut down because of economic reasons"

Jan 1, 2012

By Robert W. Hyers

Electromagnetic levitation has proven important in a wide range of experiments, all affected by fluid flow. For some experiments such as viscosity measurements, only whether the flow is laminar or turbulent must be established. For other experiments, however, quantitative assessments of velocity, shear stress, or shear strain rate are required. In most cases it is difficult or impossible to measure the internal flow in levitated droplets directly. The samples are usually small, opaque, reactive, high-temperature, metastable, or all of these. Furthermore, recirculating flow limits the utility of tracking surface particles, since they collect in stagnation points ratherthan following the flow. Most research groups have chosen mathematical modeling to assess the internal flow in levitated droplets. A variety of analytical and numerical methods have been applied, including both laminar flow and various turbulence models. A number of these models are reviewed and their impact on different containerless experiments is assessed. Much of the research reviewed here was performed by alumni of Professor Julian Szekely, and by others using similar methods.

Jan 1, 2006

The entrainment of copper matte in the slag during the slag skimming stage of a Peirce-Smith converter was studied with a dam break model. Experiments were carried out with a range of fluid pairs where the lighter fluid was allowed to overflow a weir and the amount of entrained heavier fluid measured. The resulting entrainment is measured as the ratio of the heavy to light fluid withdrawn. The fluids include oil-water, water- glycerol and salt solutions-water pairs to cover a wide range of densities and viscosities. It was found that the Richardson number, Ri, correlates the entrainment well. For the case of the liquid-liquid interface initially at the same height as the weir, the entrainment was found to vary with Ri-1/3. The transient flow was simulated with a volume of fluid (VOF) code written in-house and used a stairstep approach to represent flow obstacles. The code was validated against the experimental results with good agreement for the variation of the heights of the two fluid with time. The simulation showed that the prevailing mechanism for entrainment is due to a pressure differential created across the liquid in the converter during pouring resulting in the heavier liquid being rotated upwards and over the weir.

Jan 1, 1999

By B. Yalamanchili

Gerdau Ameristeel Beaumont presents its systematic approach for upgrade decisions that has developed over 30 years of ongoing capital projects for quality and cost improvements. This system serves to identify product needs, select process improvement strategies, justify them, and assist multi-department communications and decision-making. This is illustrated with Beaumont mills? last Stelmor upgrade and leads to a discussion of the need to consider Life Cycles of both products and technologies as we move to answer the challenges of the future.

Jan 1, 2006