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By William Petruk

A mineralogical and image analysis study was conducted on samples of U tailings from pilot-plant runs on Midwest ore in Northern Saskatchewan. The tailings had been subjected to simulated weathering for the equivalent of 10 years in a tailings facility (lysimeter). The pH varied from 7.0 at the beginning of the test to 5.9 at the end. The results show that during the simulated weathering sane of the gersdorffite, uraninite, galena and pyrite had oxidized, with gersdorffite being the most reactive and pyrite the least. Reaction was evident at the top of the lysilleter , but was most intense at the seepage discharge. sane of the released ions precipitated as Ni, Pb, and U arsenates, sulfarsenates, sulfates and oxides on particles of all minerals. Green crystals of Ni sulfate and white crystals of ca sulfate had precipitated at the surface of the lysilleter. Clay minerals and chlorite had washed from the top of the lysirneter towards the seepage discharge.

Jan 1, 1989

Testing is in progress to address compatibility issues with regard to long term storage of plutonium in contact with two different intermetallic systems. The two intermetallic systems are: 1. dental amalgam, i.e., mercury plus silver alloy powder, and 2. liquid gallium alloy plus copper powder. Both of these are plasto-metallic materials that undergo a solidification reaction at room temperature. Each system is allowed to react in contact with both high-purity alpha plutonium and a delta stabilized plutonium alloy at varying temperatures in an argon atmosphere. Wetting characteristics and possible interaction will be studied metallographically in the post-mortem condition. Complete results including metallographic examinations will be presented.

Jan 1, 1995

By Nathanael Hudson, Ruel A. Overfelt, Sushil H. Bhavnani

"In the aerospace and automotive industries, complex shapes exist which require casting. The problem with these cast parts is the empiricism required to develop the casting process and the accompanying time and expense to develop that process.There has been an interest in using fluidized beds to allow molding sand to better encapsulate the complicated surface geometries of lost foam patterns. Fluidization coupled with a mixing jet helps to homogenize the sand through stirring and may improve the integrity of the casting.At issue is the hydrodynamics of the sand and air around the foam pattern. The commercial package PHOENlCSTM is used to simulate the flow around the pre-casting foam geometry. Employing a two fluid approach, each component is considered a fluid that interpenetrates the other phase. To this end, the kinetic theory of granular 'flow for the sand phase was incorporated into the re-compilable PHOENlCSTM code.The results of this study consist of time-averaged void fraction patterns, with voidage being defined as the fraction of air in the mixture, around the foam pattern submerged in a two-dimensional fluidized bed. The model was benchmarked against past fluidized bed experiments. In order to better understand the dependence of the void fraction pattern around the lost foam pattern, certain physical parameters are varied and the resultant void fraction maps are predicted with the model. Physical parameters such as the aspect ratio of length to width, the placement of the mixing jet, and different mixing jet velocities are varied to illustrate the dependence of the time-averaged void fraction on those variables.Results consistently indicate the presence of channeling around the lost foam pattern, with the extent of the channeling and void formation reliant to a greater degree upon the placement of the mixing jet, and to a lesser degree on mixing jet velocity and aspect ratio.The increase in radial position of the mixing jet from the bed centerline had the desirable effect of granting the churning benefits of a penetrating jet, while at the same time minimizing the formation of excess void fraction at the top of the pattern."

Jan 1, 2001

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 Maria G. Alves, Alexandre M. Stumbo, Francisca M. A. Pinheiro, Jonas Alexandre, Sergio N. Monteiro, Valdo da S. Marques, Paulo R. N. da Silva

"Brazil is among the few countries with potential for developing all sources of renewable forms of energy. In particular, the country is leading the world efforts of substituting petroleum based fuels for biofuels, such as ethanol and biodiesel. Most of the Brazilian petroleum, which has now achieved self sufficiency, is extracted from offshore wells located at the north region of the state of Rio de Janeiro. In view of the future depletion of petroleum, the State University of the Northern Rio de Janeiro (UENF) has created a Center for Alternative Energies (NEAL) to carry out R&D programs on renewable forms of energy. Today, the main project of the NEAL/UENF is a model park for generation of renewable forms of energy. The objective of this work is to present the structural concept of the park and discuss its contribution in terms of scientific, technological, economical and environmental benefitsIntroductionEnergy is presently a key issue in the world agenda for sustained development and environmental protection. It is of common agreement that the existing status of increasing use of fossil fuels, mainly petroleum, natural gas and coal will not only cause depletion of these resources with a consequent elevation in price but also climate changes, especially global warming. In fact, the humankind may be already facing an irreversible situation of climate alterations as well as reduction of conventional sources of energy. The worse predictions foreseen by specialists, still for this coming century, are dramatic disasters due to catastrophic weather in association with a profound energetic crisis. This scenario may, however, be avoided by actions that could effectively tackle the core of the problem. These actions have been suggested and discussed by scientists and leading authorities, especially in international symposia [1-3]. In particular, the Kyoto Protocol proposed goals for reduction of greenhouse gas emissions as well as a mechanism of carbon credits to allow for decreasing CO2 content in the atmosphere without affecting industrial production [3]."

Jan 1, 2008

By Wan Entong, Xie Junlin, Jiann YangHwang, Yang Chengwei, Chen Junfu, Zhang Jianjun, Cao Tongyou, He Feng, Peng Zhugang, Fang De

During the solidification process of peritectic steel (PS), the peritectic reaction often causes volume contraction which associated with surface longitudinal cracks, and using mould flux with low heat flux density help for alleviating surface longitudinal cracks. New peritectic steel mold flux with Co2O3 doping reduced the heat flux density, and the optimal content was found to be 2.0 wt %. Furthermore, basicity and Na2O addition were designed, and the minimum heat flux density required basicity of 1.4 and 10.0 wt %. Na2O content. As a result, the optimal peritectic composition was CaO(35.67wt% ), SiO2(25.48 wt %)，Al2O3(3.7 wt %)， MgO(2.53 wt %)，Na2O(10 wt %)，CaF2(14 wt %)，Co2O3(2 wt %).

Jan 1, 2015

By Suleyman Tekeli, Serdar Salman, Bulent Aktas

"The effect of La2O3 content up to 15 wt% on phase stability, sintering and microstructure of cubic zirconia (8YSZ) was investigated. XRD results showed that the specimens containing up to 15 wt% La2O3 were composed of only cubic structure. Also, the specimens doped up to 5 wt% La2O3 revealed no La2O3 peaks, indicating that La2O3 was completely solubilized in the cubic structure. However, when> 5 wt% La2O3 was added, the peak of La2Zr2O7 compound emerged, showing that the overdoped La2O3 was not solubilized in the 8YSZ matrix. The lattice parameter of the 8YSZ slightly decreased with the increasing La2O3 content up to 1 wt% but further increase in the La203 amount resulted in an increased lattice parameter. The comparison of grain size of the 8YSZ specimens with various La2O3 content showed that grain size slightly increased with the increasing La2O3 content up to 1 wt% but further increase in the La2O3 amount resulted in a decreased grain size.IntroductionAt atmospheric pressures, three polymorphic forms of Zr02 are stable at different temperatures i.e. monoclinic, tetragonal and cubic. A high-pressure orthorhombic form of Zr02 has also been reported[l]. The successful production of pure Zr02 bodies is not possible all the time due to the large volume expansion associated with the martensitic tetragonal-monoclinic transformation. This fact restricts the applications of zirconia, in spite of its excellent mechanical and thermal properties. However, the stabilization of the high temperature polymorphs at room temperature as stable phases is made possible by addition of suitable dopants. Fully stabilized cubic Zr02 and partially stabilized tetragonal Zr02 show interesting properties and are widely used as ionic conductors, coatings and gas sensors in solid oxide fuel cells and structural applications[2]. Most frequently used dopants include Y203, CaO, MgO and Ce02, although other oxides, such as those of rare earth elements, can also act as stabilizers of the high temperature structures. The incorporation of aliovalent cations to the lattice, forming substitutional solid solutions, allows to control the concentration of anionic vacancies in the structure. This aspect is particularly important in designing ionic conductors[3], and is also determinant in the stabilization process[ 4]. The process of stabilization with larger ionic radii dopants is rationalized by the crystal chemistry model[ 5], that describes the dopant cations as typical stabilizer when they have larger ionic size, lower charged state and higher ionicity than Zr4+ The ionic radius of Zr4+ is 0.84 Å and that for La3+ is 1.016 Å [6]."

Jan 1, 2012

By Daguang Lu

The section of sintering and BF (blast furnace) is very important in iron-making process. In practice, the scheduling is so extensive that three faults unfavorable to continuous product will be easier to happen. This paper introduces the integration Petri Net and GA (genetic algorithm) as suitable tools for simulation and optimization of scheduling to section of sintering- BF under a certain hot iron or-der. The situation of the iron plant Chongqing Iron and Steel Company is researched in approach above mentioned. By analysis, the conclusion is drawn that scheduling with optimized values can maintain continuity of key operations , can satisfy order of hot iron in maximal degree and can keep the best stability of key storages.

Jan 1, 2009

By Mark Jolly

"Over the last ten years or so many man hours have been dedicated to developing methods for simulating shape casting processes. The majority of the methods developed have been devised by a combination of computer, mathematics and materials specialists often with limited knowledge of foundries and foundrymen. As a result of this it would appear that although there are many software packages for the foundryman to use there still exist fundamental misunderstandings as to their usefulness and suitability within the foundry.The paper aims to identify how well current software packages perform. The relationships between physical phenomena, practical defects and software capabilities are presented. Some discussion of the use of criteria functions is also presented. Finally issues arising from the postprocessing of results are discussed as the presentation of the results to the lay-person in simulation techniques is possibly one of the most important aspects in influencing the adoption of this type of software in the foundry community."

Jan 1, 1999

By Larry M. Southwick

There is much ongoing work in research and development of new processes for the recovery and recycling of met.a.ls and other materials from various waste and scrap streams. Commercialization of such new technologies requires the bringing together and successful execution of a considerable effort involving a variety of activities. These include process conceptualization, research and development, detailed design and construction, and then plant startup and operation. Processes evolve through all of these steps by engineering due diligence, making objective and critical analyses of results, and troubleshooting processing steps to, hopefully, arrive at a sequence that has the best chance to succeed operationally and economically. After a summary review of the above steps, several processes will be described in more detail that provide mostly successful examples of the above procedures. Finally, some observations will be made on areas that will become critical in the near future to the success of new processes for wastes and residues.

Jan 1, 2000

By Musa Karakus

In an attempt to explain the phenomena of lead entrainment during Cu drossing of lead bullion, two different synthetic lead bullions were heated to 1050°C, cooled slowly to various temperatures, and then quenched. The morphology and composition of dross particles that form when Mn is used to desulphurize bullion also were examined. Polished sections of these pyrometallurgical products were examined by process mineralogical techniques to identify the impurity phases, determine their chemical compositions, examine the morphology of the impurity phases and evaluate the potential for lead entrainment in such crystals, and characterize pre-quench and quench-generated phases. The phases crystallized were metallic lead, metallic copper, galena, chalcocite, albandite, Cu14.4Pb2S9. and 5.5Pb2S3.5. Metallic copper formed isometric skeletal crystals, chalcocite formed platy and skeletal crystals, and 1formed crystals and eutectic intergrowth with chalcocite and Cu14.4Pb2S9 or Cu5.5Ph2S3.5. The pre-quench crystals are larger and usually exhibit skeletal forms; the quench-generated phases are only a few micrometers across and disseminated throughout the lead matrix. Skeletal crystals of metallic copper and chalcocite form three dimensional networks that entrain large amounts of metallic lead.

Jan 1, 1989

By Milton Manrique

The thermal decomposition of zircon concentrates in a non-transferred arc thermal plasma flow reactor was investigated. The plasma torch was operated using argon-helium and argon-nitrogen mixtures as plasma gases. The effect of power, feed rate and zircon particle size was studied. Products were characterized by XRD, SEM, TEM and chemical analytical techniques. The average size of the product was in the submicron range. Free energy minimization plots were used to predict the behavior of the system under different operating conditions. A kinetic model to describe the different stages of the thermal decomposition process is proposed. The results of this investigation showed a significant segregation process where the zirconia-rich product is collected in the reactor while the silica-rich product is collected in the filter. TEM analysis indicated that silica vapor is condensed on the surface of the zirconia particles.

Jan 1, 1996

By E. J. Peuraniemi

Primary copper production using suspension smelting techniques like Outokumpu Flash Smelting always causes some dust formation. Flue dust particles are formed when sulphide feed material reacts violently with oxygen inducing particle disintegration and total desulphurisation of fragments. In the process, flue dust follows the off-gases to the heat recovery boiler (HRB) where its sulphation takes place because of prevailing conditions. Sulphation releases heat and causes also a drop in particle melting temperature and, further, particle sticking to the walls and heat exchange tube banks. Sulphation of synthetic CU20 particles were examined using a laboratory scale fluid-bed reactor. This study aims to a better understanding of flue dust behaviour in a HRB and, thus, to a better operational practise and design of a HRB. The effect of PSO/PO2 -ratio and temperature on the sulphation kinetics were tested. Standard chemical analysis, light optical and scanning electron microscopy with energy dispersive spectroscopy were used to examine the samples.

Jan 1, 2001

By Shengli Wu, Mingyin Kou, Laixin Wang, Zhe Wang, Xinliang Liu

The sticking behavior of iron ores in the shaft furnace is one of the most important problems in the COREX melting progress, which directly influence the smooth operation and productivity of shaft furnace. Therefore, it is of great importance to study the sticking behavior of pellets in COREX shaft furnace. The results showed that porous metallic iron produced at the interface of pellets samples was the main reason for the sticking of pellets in the COREX shaft furnace. The SI (sticking index) and metallization rate increased with the reduction temperature and gas flow, and decreased with melting rate. However, the SI of pellets in the COREX shaft furnace could be decreased by the proper match of melting rate and reduction temperature, reduction temperature and gas flow, while the metallization rate of pellets were kept at a certain level. Furthermore, the matching of melting rate and reduction temperature was more effective than the matching of reduction temperature and gas flow.

Jan 1, 2016

By L. Evrard, S. Brouwer, E. Bosly, E. Boydens

"A partial desulfurization roasting process has been tested on a typical copper-zinc sulfide concentrate in a Nichols Herreshoff monohearth pilot furnace whereby the su!fµr is partially removed and iron is to a certain degree preferentially oxidized. The phase changes that occur in the particles during selective roasting at 650°C and 800°C over a range of residence times were investigated by the use of chemical analysis, optical microscopy, X-ray diffraction and electron microprobe analyses. The purpose of this work was to get an insight into the mineral assemblages formed by controlled oxidation roasting and to evaluate if this non traditional approach could be afterwards used to recover zinc, copper and iron by a physical separation method. IntroductionThere has been considerable interest over the years in improving extraction and processing procedures for recovering non ferrous metals especially from polymetallic ores containing copper, lead, zinc and iron sulfides with very fine intergrown phases. Complex sulfide ores, which represent considerable reserves and resources in copper, lead and zinc, as well as precious metals and sulfur, are difficult to treat by conventional physical processes, leading to impure concentrates at low metal recovery. Some methods that can be used to treat such ores were described by G. Barbery (1). Various metallurgical routes generally combining pyro- and hydrometallurgical methods have been explored to develop new processes to recover the metals from zinc-bearing sulfidic ores and concentrates (2, 3, 4). The feasibility of partitioning complex sulfide minerals to simpler phases in order to improve selective extraction of mineral constituents has also been investigated (5)."

Jan 1, 1999

By H. Hahn, B. H. Kear, K. Kan, S. C. Danforth, G. Skandan, W. Chang

"A new chemical synthetic process for the production of non-agglomeratednano structured ceramic (n-ceramic) powders, starting from metalorganic precursors, is described. The process combines rapid thermal decomposition of a precursor/carrier gas stream in a hot tubular reactor with rapid condensation of the product particle species on a cold substrate. Critical to the success of this Chemical Vapor Condensation (CVC) process are (1) a low concentration of precursor compound in the carrier gas, (2) rapid expansion of the gas stream through an uniformly heated tubular reactor under a reduced inert gas pressure of 1-35 mbar, and (3) rapid quenching of the gas phase nucleated clusters or nanoparticles as they exit from the reactor tube. A wide variety of metal organic precursors is available commercially, all of which can be utilized in the CVC process to produce n-ceramic powders, including single phase, multiphase and multicomponent systems.The CVC process has been used to synthesize non-agglomerated n-SiCxNy and n-ZrOxCy powders, with controlled particle size in the range 2-20 nm. Heat treatment of the assynthesized n-powders in various high purity gas streams causes compositional and structural modifications, including particle purification and crystallization, as well as transformation to a whisker-like morphology. Thus, as-synthesized amorphous n-SiCxNy particles transform to (1) cubic n-SiC particles, when heated in flowing argon at temperatures> 1350 °C, (2) hexagonal n-Si3N4 whiskers, when heated in flowing NH3IH2 at 1400 °C, and (3) cubic nSiC whiskers, when heated in flowing H2 at 1400 °C.Non-agglomerated n-ceramic powders form uniformly dense powder compacts by cold pressing, which can be sintered to theoretical density at temperatures as low as 0.5 Tm' For example, full densification ofn-Zr02 powder compacts under free sintering conditions can be achieved at 1125 °C."

Jan 1, 1994

By Xinhua Wang, Xuefeng Liu, Die Yang, Lifeng Zhang, Wen Yang

"CSP thin slab continuous casters are well used in recent years. The control of heat transfer in the mold is very important because it is correlated with several slab defects. The mean heat flux of CSP mold was studied based on the plant production data of LCAK steel and weathering steel. The effect of various operation conditions on the heat flux was analyzed and discussed. The results showed that the heat flux was 2.1-2.6 MW/m2 on the wide face and 1.2-2.2 MW/m2 on the narrow face for the casting of LCAK steels. During the casting of weathering steel, the heat flus was mostly 2.05-2.5 MW/m2 on the wide face and was 1.1-1.8 MW/m2 on the narrow face. The heat flux depended largely on the casting speed. The heat flux on the wide face increased obviously with increasing casting speed when the casting speed was relatively low; however, at high speed, the heat flux increased slowly or kept constant. At low casting speed, the heat flux depended little on the superheat of the molten steel. The mean heat flux depended little on the level fluctuation at continuous casting mold.IntroductionCSP thin slab continuous casters are used more frequently in recent years for its low cost of construction and manufacturing. The structure of CSP mold is very different from that of conventional thick slab casting mold, inducing the difference of heat flux between them. There have been some studies about the heat flux of thick and medium slab casters [l, 2]. Heat transfer in the mold is very important for the solidification of molten steel because it is correlated with several slab defects such as slab break-out, longitudinal crack, and surface depression. Moreover, higher casting speed is desired to improve the productivity. The control of solidified shell is extremely important. The heat flux is largely influenced by several casting parameters such as the cooling intensity of the mold, the casting speed[3], the mold flux powder [3, 4] and the carbon content of steel as well [5]. The investigation on the heat flux and affecting parameters can help to understand the solidification of molten steel in the mold."

Jan 1, 2013

By K. R. Barrett

The cupellation of dore/lead bullion to recover precious metals is one of the oldest metallurgical processes known to man. In recent times this has been carried out in small reverberatory furnaces but the process suffers from a number of disadvantages. A new process has been developed at the Northfleet refinery of Britannia Refined Metals Ltd, which gives much improved performance. The process depends upon the injection of oxygen through a nitrogen shrouded lance at the bottom of the furnace. The lance is consumable and of unique design. Reaction rates are high giving short process time; fuel consumption is low; oxygen efficiency is high and dore recirculation is low. The new process has resulted in substantially lower operation costs.

Jan 1, 1989

By A. Lakschevitz

The Amazon region offers a large potential for gold extraction but its peculiar characteristics such as heavy rains, lacking of roads and general infra-structure, nature of the ore deposits, etc.. do require special care in plant design. REMETÁLICA has developed a know-how is designing leaching plants which have been demonstrated to be profitable under those tropical weather conditions. The solutions adopted are related to general process route, leach liquor distribution and flow pattern, conditioning of solids and effluent treatment. These plants, now operating in South America countries, demonstrate the success for the technology developed. A tipical plant with 800 t/day ore processing capacity, may require an investment of US$ 1.200.000,00, arid have? a pay back period of a few months, depending on ore grade.

Jan 1, 1989

By C. L. Lin

Transformation of linear grade distribution to volumetric grade distribution has been used to estimate the actual mineral liberation during wet, batch, ball mill grinding of a copper ore. The degree of liberation based on the multicomponent-multisize grinding liberation model using volumetric grade is lower than the apparent degree of liberation estimated from using King's linear intercept model.

Jan 1, 1987