Search Documents

By Nicola Baldo, Marco Pasetto

"The paper presents the results of a laboratory study, conducted at the Experimental Road Laboratory of the University of Padova, in order to verify the possibility to use different types of electric arc furnace (EAF) steel slags – in substitution of the natural aggregates – in the composition of both dense graded and porous asphalt mixes for flexible road pavements. The research has been articulated in a preliminary study of the chemical, physical, and mechanical properties of the EAF steel slags, and in the following mix design and performance characterization of the bituminous concretes, through stiffness modulus tests at various temperatures and permanent deformation (creep) tests. All the mixtures with EAF slags have satisfied the requisites for acceptance standardized for the road sector, thus resulting as suitable for use in the construction of infrastructures, moreover presenting higher mechanical characteristics than those of the corresponding asphalts with full natural aggregate. IntroductionSteel is produced industrially employing two main technologies: the integral cycle, which starts from mineral iron, and the electric cycle, which uses scrap metal. A consistent amount of the steel produced in Italy (approx. 55%) comes from Electric Arc Furnaces (EAF), which every year, alongside the steel, produce approximately 2 million tons of slag. The recycling of this waste product to produce new high-quality raw materials would reduce both the exploitation of limited natural resources and the amounts of refuse. In the European Union, 60% of slag from EAF is still today disposed of in dumps. The extremely diverse origins of scrap metal (waste from mechanical manufacturing, industrial and civil demolition, car bodywork, etc.) means that the by-products generated by the smelting, slags and ashes, contain different elements, in varying composition, also depending on the type of steel to be produced and the consequent adding of binding and melting elements during the production process. For this reason, iron and steel industry electric furnace slag - unlike the blast furnace dross utilised in cement works, which has a more uniform composition as it comes from a more standardised cycle – has been viewed in the past with some diffidence and so, at least in Italy, the possibilities of its re-use have never been fully developed."

Jan 1, 2008

By Enrique Posada

"The Valle de Aburrá area, corresponds to the city of Medellín and neighboring municipalities, with more than 3 million people. The area generates a sizable amount of solid waste, which has been taken to landfills for the last 20 years. This paper proposes a model for public policy making which considers the cost and benefit of different alternatives to handle the wastes in the coming 20 years. Combinations of several alternatives: Recycling, waste reduction, waste separation, incineration, land filling with lixiviate treating and gas energy recovery, and organic waste composting are considered and modeled and the results presented as a contribution for a more rational approach to policy making than the one currently being employed.IntroductionThe author, working for INDISA S.A., acted as a consultant for the direction of planning of the Empresas Varias de Medellín in 2004. This entity has the responsibility for the handling of the solid wastes of the city of Medellín and some of the neighboring municipalities. At the present time more the 700.000 annual tons of waste are taken to the site of La Pradera, located in very rainy location (3.000 mm of precipitation per year), with complex in topography and very far away from the sources of the waste. During the work the author detected important problems that should be addressed, as follows:Lack of adequate technical administration and resources. The entity did not count with sufficient human resources to focus on the appropriate technical handling of the solid waste. The organization worked mostly with independent contractors, lacking enough coherence and integration. The internal workload was too large for the few people who had technical responsibility and this gave rise to attention problems. It is important to have clear technical procedures, technical know how and human resources, continuity in the activities. It is important to have a clear capacity to plan, to study, to make tests and monitoring, to pursuit and develop ideas, to optimize the processes and to introduce changes, to respond to environmental authorities, to the communities and to mass media and to handle the contractors. All this was basically lacking. In the case of the handling of the sanitary filling of La Pradera, for example, although the people in charge were very able and dedicated, the magnitude of the task was too large and the resources they had were insufficient. As a result, the site had at the time of the study, problems with thousands of vultures, lack of immediate cover up for the waste, uncontrolled leaching, the area being dirty and little attractive, despite being called a park."

Jan 1, 2008

By James R. Myers

A source of clean gas containing sulfur dioxide and sufficient oxygen for conversion to sulfur trioxide is essential to the production of sulfuric acid. SO2 containing gases obtained from roasting sulfide ores are heavily contaminated with inorganic dust and volatile impurities. If not removed, these contaminants will reduce product acid quality, foul the catalyst beds and mist eliminators, and accelerate equipment corrosion. This paper reviews conventional gas cleaning systems for metallurgical acid plants, followed by a discussion of modern systems utilizing DynaWave Scrubber technology. This technology is based on a unique approach togas scrubbing that can concurrently accomplish several gas cleaning/processing tasks. Scrubbing liquid is injected into the gas stream to create a "Froth Zone". This is a region of extreme turbulence, with a very high rate of liquid surface renewal. It efficiently removes both particulate matter and gas contaminants, and is also a cost effective quenching device for gases as hot as 1250 o C.

Jan 1, 1992

By LeRoy C. Prichard

The scrap based steel producers in the United States generate an estimated 650,000 tons of electric arc furnace (EAF) dust annually which is classified as hazardous waste, K061. These scrap based producers commonly referred to as mini-mills represented 39% of the steel produced in 1994. Based upon the EAF plants being installed or planned today, it is a reasonable projection to anticipate 50% of the steel produced in the United States will be by EAF's. Using a straight line projection of percent of steel produced to tonnage of EAF dust generated, this will result in 833,000 tons of dust being generated upon the completion of these new EAF producing plants, presumably by the year 2000. Because the United States is a capitalistic economy, a steel producer is in business to make a profit therefore dust management becomes a very important variable in the cost of making steel. An EAF mini-mill dust management program must consider at least three components. First the handling of the dust must be in accordance with the law; i.e., the Environmental Protection Agency rules and state and local municipalities guidelines governing K061. Second, it must be an economical solution that allows a company to manage its dust processing costs, a component of its total steel production costs while producing steel at a profit. Third, the dust management program should be one that is environmentally responsible; viz., the program should reclaim or recycle the dust constituents, as feedstock materials or saleable products. The first component, obedience of the law seems to be a relatively straight forward, common sense objective; however, as nearly every mini-mill operation will testify it has been a area of changing laws with confusing variations when it comes to K061. Even more frustrating is the fact that obedience or compliance today does not mean that the company will be considered law abiding in the future.The liabilities associated with

Jan 1, 1995

By Frederick W. DeVries

The author was invited by "60 Minutes Australia" to provide on-site technical background on cyanide, mining, and the environment, in their investigation of the January 30, 2000, spill at the Aurul gold-recovery site in Baia Mare, Romania. Some remarks on the incident ?and its implications surround a showing of the fourteen-minute telecast. The thrust of the TV reporter was that aspects of the dam implied the owners' use of standards Jess than would have been met for installations in technologically more advanced locations (like Australia). As a result, the public-relations impact is one of embarrassment for the world mining industry.

Jan 1, 1998

By S. -H. Jeon, Y. -S. Choi

"The three dimensional current distribution on the rectangular cathode is predicted using a boundary element method with a linear element of trigonal type. The effect of cell geometry and anode shape on current distribution is simulated. Calculated results compare well with experimental results. The proper combination of anode size and distance between electrodes increase the current uniformity.The importance of electrodeposition as a fabrication technology in the electronics industry is large and growing. The main advantages of this wet processing method, in comparison to other dry processing methods, lie in its high yield, rapid processing and low cost. In nearly every application of electrodeposition the pursuit of deposit uniformity, especially thickness uniformity, has been technically imperative. The thickness uniformity of the deposit depends largely on the current distribution over the cathode. The current distribution is primarily determined by the geometrical characteristics of the electrodes and the cell. Also the polarization at the electrode surface and the mass transfer affect the current distribution.The current distribution is an important consideration for those involved in designing electrochemical systems and electroplating systems in particular. Although it is important, the common practice in industry is to use trial and error method to design the cell that optimize the uniformity of current distributions in electroplating. The purpose of this paper is to illustrate the useof boundary element method to predict three-dimensional current distribution in rectangular cell.The calculation of the current distribution is possible by various numerical techniques, which include the finite difference method (FDM)1, the finite element method (FEM)2, and the boundary element method (BEM)3,4. These methods of the numerical calculation have various problems, respectively, but the BEM is considered to be the most efficient. This is due to the fact that the BEM has the advantage of solving field equations only on the surface of a calculation domain. A good comparison between the BEM and the FEM for the secondary current distribution in a Hull cell was made by Matlosz et al.5The fundamentals on the theory of current distribution in electroplating are well-established in the literature by a number of authors.6, 7, 8 However, a small fraction of these works have been specially addressed to three-dimensional analysis, and, mostly thel·10 have focused on the problem qualitatively rather than quantitatively.Extending the previous work to three-dimension, we developed the program for the quantitative calculation of 3-dimensional current distribution using a boundary element method with a linear element of trigonal type. Integrals with singularity from the fundamental solution have been analytically computed and it is shown in detail in the Iiterature11. This paper deals with the three dimensional current distribution for the electrode position of copper in a cubic type cell and the effect of anode shape, size and the distance between electrodes on current distribution is studied."

Jan 1, 1997

By Min Chen, Zhen Tian, Hongxu Cui

"The effects of adjusting technology on the phosphorous enrichment in converter slag were investigated. The results showed that the grain size of 2CaO·SiO2 with high phosphorus containing content increased slightly with the decreasing of cooling rate, and the proper cooling rate was confirmed to be about l.0°C.min-1. Moreover, the morphology of the phosphorus-rich phase of 2CaO·SiO2-3CaO·P2O 5 was changed from granular for the higher basicity of converter slag to the coexistence of granular shape and rod-like for the lower basicity of adjusted slag. With the addition of adjusting agent such as SiO2 to lower the basicity of converter slag, the phosphorus in converter slag could be transferred into 2CaO·Si02 phase effectively, and P2O 5 content in high phosphorus containing phase reached to above 30%.IntroductionThe yield of converter slag is very large in China, but most of the slag is stacked usually after the separation of iron, which not only takes up a lot of land, but also affects the ecological environment seriously. Therefore, improving the comprehensive utilization and value-added products of converter slag is of great significance to recycle the steelmaking slag[l-3]. On the other hand, the refining of hot metal with high phosphorous content is an unavoidable problem with the decreasing of high grade iron ore, and as a result, more amounts of high phosphorus containing steelmaking slag are produced. However, the current recycle of converter slag is more focused on the emission reduction and reuse of steelmaking slag inside the iron and steelmaking process without considering the recycle of phosphorous resources[4-6]. At the same time, the development and utilization of phosphate ore as a strategic resource is drawing more and more attention, but the phosphate ore in China is mostly low grade and significant amounts of tailings are produced which is harmful to the environment. Therefore, it is important to separate phosphorous resources in steelmaking slag which can be used as phosphate ore for fertilizer material[7-9].Literature studies showed that most of the phosphorus in steelmaking slag existing as 2CaO·SiO2-3CaO·P2O 5 solid solution phase in 2CaO·SiO2 particle. The P2O 5 content in the phosphorus containing phase is very low due to the fact that the basicity of converter slag is usually high and the precipitated amounts of 2CaO·SiO2 particles during cooling are very large, resulting in the fact that the P2O 5 contents in 2CaO·SiO2-3CaO·P2O 5 solid solution phase are much lower which is impossible to be used as phosphorous resources instead of phosphate ore. Thus, the enrichment of phosphorus in steelmaking slag is need[ 10-14]."

Jan 1, 2011

By David G. Dixon, Ahmad Ghahremaninezhad, Edouard Asselin

"In this study pertaining to the electrochemistry of chalcopyrite, the active/passive behavior of a chalcopyrite electrode in 0.5M sulfuric acid solution was investigated. Potentiostatic and potentiodynamic polarization and multi-cyclic voltanunetry were conducted to analyze the electrodissolution parameters of the electrode.The potentiodynamic and potentiostatic polarizations of chalcopyrite revealed the formation of a passive film on the surface of chalcopyrite. From the potentiostatic study in the passive potential region, a decrease in the dissolution current density by increasing the potential was observed. From this, it was concluded that the passive film is an n-type semiconductor and cation interstitial defects or anion vacancies are the charge carriers. From multi-cyclic voltammetry studies, four cathodic peaks at - 0.37, 0.30, -0.10 and-0.20 YsHE were detected on the surface of a passivated chalcopyrite electrode. The cathodic peaks at 0.37 and 0.30 V were connected to ferric to ferrous reduction and copper sulfide formation, respectively. The peaks at -0.10 and - 0.20 were related to chalcopyrite reduction. The products of the chalcopyrite reduction reactions were suggested to be Cu2S, Cu9fesS16 and Cu5feS4 and evolution of hydrogen sulfide gas (H2S).IntroductionChalcopyrite is the most abundant copper bearing mineral in the world and its dissolution behavior represents the most important technological consideration in the hydrometallurgical extraction of copper [I]. Since the current pyrometallurgical methods for copper extraction from chalcopyrite have environmental issues, many studies have considered the leaching and dissolution of CuFeS2 in different aqueous media [2-5]. The main problem associated with leaching processes is the slow dissolution rate of the mineral [6]. During the dissolution process, increasing the potential of the chalcopyrite in the anodic direction will cause the formation of surface layers which hinder the dissolution rate of the mineral [7]. The precise composition of the layers is in dispute. Previous studies have concluded that these layers could be sulfur [8-9], precipitated iron compounds [8], a solid electrolyte interphase (SEI) - which slows the rate of electron transfer- [10], a metal deficient sulfide [ll], or polysulfidic in nature [12-13]. In order to increase the leaching kinetics of chalcopyrite, the characterization of the layers formed during dissolution is essential and electrochemical methods are important to this end. Studies by Biegler [14] show nucleation and growth of a thin two-dimensional sulfide phase on the surface of chalcopyrite during the exposure of a polished sample in HzS04 solution or air. More studies by Biegler and Swift [15] have shown evidence for nucleation and growth of a 3-dimensional phase at low anodic potentials (around 200 mV vs. OCP). The current-time behavior of the dissolution process in this potential area has the characteristics of expansion and overlap of localized dissolution centers."

Jan 1, 2012

By Thomas Niehoff, Dave Stoffel

"Energy in the form of natural gas, oil and electricity is expensive and will continue to be a rare resource in the future. Recycling of metals, instead of primary production, is a logical and crucial step towards energy conservation. Energy consumption can be impacted by using advanced combustion systems for metals recycling. Air-fuel combustion has been the conventional method to melt and recycle metals. Global competitive pressures, “greenhouse” gas emissions, and high energy prices force melt shop operations to optimize energy usage and reduce overall operating costs. Oxy-fuel combustion and process technology can be applied to metal recycling operations to meet these objectives. Linde has converted several hundred furnaces from air-fuel to oxy-fuel technology and has extensive experience in optimizing the use of oxygen in furnaces. Additionally, Linde has the process knowledge necessary to avoid costly start-up issues that can accompany the transition to oxy-fuel technology. This paper will describe the benefits and potential issues for conversion to oxy-fuel.IntroductionThe furnace combustion system is the heart of a fossil fuel fired melting process and must be properly matched to the furnace to work as one cohesive unit. Furnaces vary widely in size, shape and features. Rotary furnaces are barrel-shaped and can be designed for tilting or nontilting operation. In a rotary furnace, the products of combustion create a single or double pass through the furnace prior to exiting. Reverberatory furnaces are box-shaped and can also be designed for tilting or non-tilting operation. Reverberatory furnaces are constructed of single or multiple chambers, with or without metal bath movement, and designed for continuous or batch processing. Different furnaces are used for different feedstock materials and products.Furnace combustion systems also vary in many ways. Combustion systems can be of air-fuel or oxy-fuel based technologies, or a combination of the two, resulting in an air-oxy-fuel system. Each of these types of systems has different combustion characteristics which can produce very different results. Here we will describe specific differences in melting processes and their associated energy requirements."

Jan 1, 2009

By Adam Powell, David Dussault

"Electric Field-Enhanced Smelting and Refining is a process for driving the reaction between carbon in hot metal and iron oxide in slag, for example, in a steelmaking reactor. This process involves inserting electrodes into the slag and metal phases, such that the overall reaction FeO + C -> Fe + CO is separated into two half-cell reactions: Fe2+ + 2e· -> Fe at the cathode in the slag, and C + O 2 • -> CO + 2e· at the anodic slag-metal interface. Without the electrodes, the reaction is very slow, but with electrodes, the additional surface area available to the ferrous ions for reduction accelerates the reaction even without any applied bias. When a bias is applied to the electrodes, the electric field across the slag further accelerates the overall reaction.With or without applied bias, the process is first-order in the ferrous ion concentration, and limited by ferrous ion transport to the cathode. To complicate matters, as the liquid iron is reduced at the cathode, the Mullins-Sekerka instability leads to formation of dendrite-like liquid iron fingers which grow into the slag. Because of this, the design of the cathode can have a significant effect on the overall process kinetics, and understanding of the dynamics of these fingers and of their effect on mass transfer is necessary for the intelligent design of the overall process and the cathode in particular.Toward this end, a detailed mesoscopic two-phase slag-metal model is presented here which describes multi component diffusion in the slag and fluid flow in both phases in the vicinity of the cathode. Diffusion in the slag is driven by chemical and electrical potentials. The phase boundary is modeled as a diffuse interface using a phase field approach. Because this electrochemical reaction occurs at high-temperature, the kinetics of charge transfer and adsorption through the double layer are fast relative to transport, permitting the use of simple linear reaction kinetics. This also eliminates the need to discretize the double layer, with the result that charge neutrality may be assumed everywhere in the domain. Introducing electric field dependence of the gradient potential and well height coefficients in the free energy function allows the model to capture electrocapillarity at the interface."

Jan 1, 2001

By A. D. Neuman, C. C. Davis, M. R. Lopez, A. C. Martinez, T. A. Nothwang, F. G. Hampel, S. L. Voit

"One of the thrust areas for the Global Nuclear Energy Partnership (GNEP) program is the development of actinide bearing fuels for transmutation in a fast reactor. Mixed Oxide (MOX) fuel has an extensive fast reactor irradiation history and thus is being considered for use as a baseline composition from which minor actinides can be incorporated for use as a transmutation fuel. The current study involves characterization of precursor powders and pellets destined for the Advanced Test Reactor in Idaho. These pellets will have three compositions: one standard MOX composition, (U0.80Pu0.20)O1.98, and two compositions of minor actinide mixed oxide (MAMOX) with oxygen to metal ratios (O/M) of (U0.75Pu0.20Am0.03Np0.02)O1.98 and (U0.75Pu0.20Am0.03Np0.02)O1.95. The precursor powders were characterized using a field emission gun scanning electron microscope (FEG-SEM) to determine particle morphology, size, and size distribution. An electron probe microanalyzer (EPMA) was used to characterize element distributions in the pellets.IntroductionThe fundamental purpose of GNEP is to enable a fuel recycling partnership between member nations. The customer nations utilize the fuel for electricity generation provided by and subsequently recycled by the supplier nation. The supplier nation recycles the actinide constituents, mainly uranium and plutonium, in advanced nuclear power reactors, and thus reducing waste volumes [1, 2]. Nuclear materials are strictly controlled through the International Atomic Energy Agency. One of the thrust areas supported by the GNEP program is the development of actinide bearing fuels for transmutation in a fast reactor under the U.S. Advanced Fuel Cycle Initiative (AFCI) in order to transmute long-lived transuranic actinide isotopes into shorter-lived fission products [3].MOX fuel has an extensive fast reactor irradiation history and thus is being considered for use as a baseline composition into which minor actinides can be incorporated for use as a transmutation fuel [4]. Irradiation performance data on oxide fuels with high concentrations of minor actinides is limited, which has prompted this study. This paper discusses the characterization results of precursor powders and pellets prepared for the Advanced Test Reactor in Idaho to determine the effects of including minor actinides in the fuel, and addresses two fuel test matrices proposed by Hilton et al. [3]. The pellets will have three compositions: one standard MOX composition, (U0.80Pu0.20)O1.98, and two compositions of MA-MOX with O/M of (U0.75Pu0.20Am0.03Np0.02)O1.98 and (U0.75Pu0.20Am0.03Np0.02)O1.95. The precursor powders, uranium oxide (depleted, DUO2 and highly enriched, HEUO2), neptunium oxide, NpO2, americium oxide, AmO2, and plutonium oxide, PuO2, were characterized using a FEG-SEM for particle morphology, size, and size distribution. The morphology of the actinide powders was studied in the areas of flowability and porosity in order to predict manufacturability. The MOX pellets were characterized using an EPMA in order to determine impurity levels and locations."

Jan 1, 2008

By Payal Bakshi, Sangeeta Tiwari, Mohini Saxena, Anusha Sharma

"Recycling and reuse is perhaps the most favorable and beneficial way to solve the problem of industrial waste disposal. However, the use of industrial wastes like fly ash, tailings etc is in practice for brick manufacturing, land filling, embankments filling etc. These existing practices do not add enough value to the wastes. Moreover, some wastes may have very good potential to be incorporated in valuable products like paints. This study reveals about the value addition of industrial wastes like fly ash, copper tailing and blue dust as an extender in paints. Comparative properties and characteristics of these three wastes for application in paints are discussed. Fly ash, copper tailing and blue dust were characterized for physical, chemical and mineralogical properties and used in different paint formulation based on their potential to the particular application. Fly ash has been found very useful in enamel, primers and flat paints while copper tailing was found suitable in oil based paint formulations. The performance of fly ash and copper tailing paints were evaluated by comparing with those of conventional whiting extender. Blue dust was compared with conventional iron oxide for use in priming coats. The extender properties of these new material and paints prepared out of blue dust, fly ash, copper tailing, were found better than the existing related materials.IntroductionIndustrial development and environmental reforms should run parallel to benefit each other. This is the best policy, which must be adopted by industries for the sustainability of the current modern life. The high degree of industrialization and urbanization adds scads of waste resulting problem of pollution and challenges of their safe disposal. The nature of waste depends on the process that produces waste as its by-product. Therefore, policies/plans are prepared by keeping the view of possible potential hazards. Among the different wastes some are generated in the industries, which have great importance in the country’s economy, like fly ash waste from thermal power industry and mining waste. In India the total contribution of thermal power in the total electricity generation is more than 70% and it produces about 123 million ton of the fly ash annually [1]. On the other hand mining plus extraction of ferrous and nonferrous metals also produce waste in million tonnes of categories [2]. Since the generation of this waste is very high they cover large land area for their disposal and dumping [3]. The storage of this waste in the dumping sites for long time duration may cause problem of land, surface water, ground water and fertile soil contamination [4]. As far as Indian fly ash is concerned it does not contain toxic element over the limits of hazardous waste [5]. However, in general most of the metals deposits are found in the form of pyrite based ores. Mining wastes contain toxic elements e.g. heavy metals in varying amount, which get mobilized when pyrite get oxidized to sulphate producing sulphuric acid [6,7]. These ores contain very less amount of targeted metals in themselves thus they require extensive preprocesses for concentration of the metals [8]."

Jan 1, 2008

By Edouard Asselin, Guikuan Yue

"In the present study, electrochemical measurements, especially cathodic potentiodynamic polarization (CPC) and cyclic potentiodynamic polarization (CPP), have been employed to study the kinetics of ferric reduction on chalcopyrite in aqueous Fe( II )-Fe(III)-H2S04 solution at 25°C and 70 °C. Results from the calculation ofspeciation in the above solution reveal that, at both 25 °C and 70 °C, the real Fe3+/Fe2+ ratio is much lower than the nominal ratio, which leads to smaller values for the reversible potential of the ferric/ferrous couple based on the Nemst equation. Exchange current densities of the ferric/ferrous couple were obtained by extrapolating the cathodic linear Tafel line to the reversible potential and are on the order of 10-7·10-6 A/cm2 at 25°C and 10·6-10-5 A/cm2 at 70 °C, respectively. The transfer coefficients were about 0.35-0.38 at 25°C and 0.35-0.45 at 70 °C. Polarization plots of CPC and CPP under different nominal Fe3+/Fe2+ ratios are in good agreement at 25 ·c and at 70 °C. Based on the obtained exchange current densities, the rate constant k, was calculated and is on the order of 10-1 cm/s at 25 °C and 10 1 cm/s at 70 °C.IntroductionChalcopyrite is the most abundant copper mineral in nature, accounting for about 70% of copper reserves in the world [I]. In recent years, the metallurgical industry has been searching for a hydrometallurgical process as an alternative to pyrometallurgical treatment due to high emissions of S02 and capital costs associated with smelting. Activity in this area has increased recently due to some inherent advantages associated with hydrometallurgical processing, such as the possibility of treating low-grade ores (increasingly more abundant in the case of copper) and easier control of waste, with the attendant benefits to the environment [I]. Chalcopyrite is highly refractory under most hydrometallurgical conditions, owing to the formation of an anodic passivation layer on the chalcopyrite surface which renders the process kinetics very slow. Most of the currently proposed processes are based on sulfuric acid with ferric ions and/or dissolved oxygen as oxidants. Sulfuric acid is preferred over all other leaching reagents in terms of cost, environmental friendliness, and ease of its regeneration during electro-winning. Some of these processes have been piloted in attempts to implement these technologies on an industrial scale,"

Jan 1, 2012

By A. R. G. Azevedo, G. C. Xavier

"This work has for objective to identify the soil of the neighborhood Codin located in a lacking area of the urban nucleus of the district of Campos dos Goytacazes - RJ, after the identification the best line was determined for the production of soil-cement blocks. In this area it happens habitational deficit and precarious constructions are also verified. The use of soil cement blocks is considered a cheaper constructive method than the conventional (ceramic block or of concrete), because one of the components of the raw material is abundant (the soil) and the constructions can be erect with certain easiness for collective effort regime. Samples of soil of this area were collected for they be characterized with relationship to the physical and chemical characteristics, with I aid of GPS the community's location it was registered. Identified the soil type, the work began the study of lines they to make possible your use in an economical and safe way. For that were made drained blocks in the format 19,5x10x5 cm, with lines containing the addition of 5% and 10% of cement in volume, and as parameter of quality the absorption of water and the resistance to the compression were measured, following the Norms of ABNT.IntroductionWe know that the use of the soil by the humanity come from the antiquity. And ifs confirmed by the archaeology places of the old civilizations of the word. The most remote constructions date from 10.000 years old in Jericoh, in the Jordan River Valley. This work became more intensive at 3.000 B.C. (Before Christ), by people who lived in those valleys with mood areas, a lot of clay and washed by the rivers.Almost all the sectors of engineering of soils choose the stability to use the local soil. Although, artificially treated, offers more economical advantages.The stability of a soil consist of endow it of the condition to resist the deformations and ruptures during the period that it is being used, because these characteristics are necessary in any construction.The application of the natural soil only is possible in places that they are of good quality and attend to the requirements of engineering to the type of previewed application. The granulemeter correction and the chemical stability include cases of inappropriate soils areas, turning the soil able to be used as construction material. Among the stability agents, usually added to the soil for stability ends, the cement is indicated."

Jan 1, 2013

By Wei-ling Wang, Ryosuke O. Suzuki, Xiang-ning Meng, Miao-yong Zhu

"A finite-element thermal-stress model of continuous casting mold is conducted to predict deformation of copper plates and its change with different cooling structure. The results show that deformation behavior of copper plates is mainly governed by cooling structure and thermal- mechanical conditions, deformation amount is related to structure geometry, and a small deformation mutation occurs in cooper-nickel boundary due to different properties. The maximum deformation of hot surface centricities of wide face locate at 100 mm below meniscus and that of narrow face locate at meniscus and terminal of water slots and significant curvature fluctuations on both sides of copper-nickel boundary. The maximum deformation of centricities is increased up to 0.05 mm with thickness increment 5 mm of copper plates, and maximum deformations are only depressed 0.01 mm and 0.02 mm with increments of 1 mm nickel layer thickness and 2 mm water slot depth respectively.IntroductionIn conventional continuous casting of steel, a large amount of sensible and latent heat of molten steel dissipate in primary cooling zone and make continuous casting mold under enormous heating load giving rise to thermal stress, deformation, high-temperature fatigue and creep not only depress mold life-span, but reduce casting stability [1] Many studies focused more on heat transfer, solidification and shrinkage of solidifying shell to provide inverse proposals for optimizing cooling system and even designing new taper of mold [2,3], but it is generally useless to those of having been manufactured or being put into production. Therefore, mold-related forward problems show necessity to be discussed deeply, and stress and deformation distributions based on special thermal conditions in mold should be analyzed in order to explore suitable cooling structure of mold directly. Samarasekera et al. [4] examined heat flow and distortion of two-dimensional longitudinal sections and investigated effect of cooling water velocity, copper plates thickness and carbon content on formation of rhomboidity and longitudinal comer cracks. O'Connor et al. [5] developed a three-dimensional mathematical model to compute thermo-mechanical state in thin-slab mold and calculated temperature and deformation of mold wall to assess roles of various process parameters on impacting mold life. Thomas et al. [6] predicted temperature, distortion and residual stress in mold and indicated increased distortion requires increased remachining, which reduces mold life and increased residual stress increases the probability of a catastrophic crack failure. Park et al. [7l determined heat-flux profiles in funnel-shaped and parallel thin-slab molds based on an inverse heat conduction model and thermocouple temperature measured in-plant and put them into three- dimensional finite-element thermal-stress model to predict temperature, distortion and residual stress of mold wall. Korie et al. [SJ focused on prediction of temperature, distortion and residual stress in mold and in particular to clarify that mold life is significantly affected by temperature and its rigidity, but little effect by mechanical including clamping force, bolt prestress, friction and ferrostatic pressure. Meng et al. [9l predicted temperature and thermal stress in a slab mold and analyzed effect by cooling system geometry and casting speed quantitatively. In present study, a three-dimensional finite-element thermo-mechanical model with type-switched element is transformed from previous heat-transfer finite-element model [9l, and mold deformation is simulated in order to shed light on thermo-mechanical behavior with special thermal conditions and different mold geometry at high casting speed."

Jan 1, 2013

A full-scale test of chalcocite heap bioleaching was undertaken at Straits? Nifty Copper Operation. Straits worked closely with the CSIRO to investigate the chemical and biological changes over the life cycle of this chalcocite heap bioleach system. Results indicated nearly 80% copper recovery was achieved in just over 300 days. Significant changes in iron chemistry and microbiological activity were detected. Temperatures in the heap reached as high as 70 ºC during the time of maximal copper recovery rate. The dominant cultivatable bacterial strains were typical mesophilic bacteria, however, naturally occurring moderately thermophilic bacteria were detected by culture and culture independent molecular (PCR followed by denaturing gradient electrophoresis [DGGE]) and signature lipid methods. Signatures for the iron and sulfur-oxidising species Acidithiobacillus ferrooxidans and Sulfobacillus spp., as well as the moderately thermophilic heterotroph Alicyclobacillus sp. were detected. Biomass was greatest in ?warm? but not ?hot? parts of the heap, and Hyperthermophilic Archaea were not detected.

Jan 1, 2003

By Kurt Westerlund

Three years operating experience of the FLUXFLOW waste heat boiler (WHB) 20.000 nm3/0h at Boliden Rönnskär Sweden on a TBRC smelting galena (PbS). Operating experience from the Kivset flash WHB 11.900 nm3/h at Samim, Porto Vesme, Sardinia, Italy. Conceptual features of the 93.600 nm3/h FLUXFLOW (WHB) on the Isasmelt smelting in melt furnace for 180.000 t Cu/a at Mount Isa, Australia.

Jan 1, 1992

By P. P. Knight

The Parkes Process is an important step in the pyrometallurgical refining of lead bullion and it is estimated that more than 50% of the Free world's primary silver production is processed by this route. The metallurgical efficiency of the process can have a significant impact on the overall refining costs, particularly with regard to zinc consumption and the costs of working up the silver-rich crusts?. Several authors have used mathematical or graphical methods in order to calculate the minimum required zinc additions and to study the merits. of alternative. operating procedures, but these methods are of necessity very cumbersome and are only able to deal with relatively simple systems. The paper explains how a computer model was developed which simulates the Parkes Process accurately and can predict the effects of changes made in operating methods. Examples are given of some of the findings and their relevance to the practical conduct of the process is? discussed.

Jan 1, 1990

Off-gas cleaning from metallurgical plants requires? in many cases very low dust contents which are difficult to achieve with conventional scrubbers, even with high energy input. Lur.gi has developed a scrubber which improves the separation of the fine dust by electrical charge prior to. the scrubbing zone. An Electrostatic Scrubber has been successfully installed for the off-gas cleaning from slag' granulation after a waelzkiln achieving less than 1 mg/m3 in the clean gas.

Jan 1, 1992

By Hang Goo Kim

A mathematical analysis based on equilibrium modeling has been developed to describe the distribution behavior of minor elements such as Pb, Zn, Bi, Sb, and As among gas, slag and recovered copper phases during the reduction of copper oxide in slag cleaning with CO gas. The results show that large fractions of the impurities transferred to slag during smelting or converting are recycled to the recovered copper metal. It is also shown that there is a limit to the recovery of copper from slag because iron oxides are also reduced to form a copper-iron alloy at low oxygen potentials. The effects of various operating parameters such as temperature, the activity of FeO, the initial amounts of the elements in the slag and CO content in process gas, on the behavior of these minor elements are discussed. The predicted results were compared with the results of a pilot plant operation in which pulverized coal was used as a reductant. Consistent trends between the two cases were obtained.

Jan 1, 1992