Search Documents

By Girley Ferreira Rodrigues, Crocce Denise Romano Espinosa, Victor Bridi Telles, Eduardo Junca, Jorge Alberto Soares Tenorio

"Steel sector is responsible for the generation of solid waste, liquid and gaseous effluents. The Solid waste are mainly composed of slag, dust, sludge and scrap. The industry generates approximately 650kg of solid waste per tonne of steel. Approximately 10% of this waste is in the form of dust and mud. The basic oxygen furnace dust is a waste generate by steel sector. Each tonne of produced steel generates 10 to 20 kg dust. Thus, the aim of this paper is study the reduction of pellets made with BOF dust using hydrogen and study kinetic during the reduction. The tests were performed in a netzsch thermobalance to obtain the data of lost mass. This loss mass is coming from iron oxides present in the BOF dust.IntroductionThe generation of solid waste is a problem for many companies in the steel sector. The main solid wastes generated are slag, dust, sludge and scrap [1]. Beyond solid waste liquid and gaseous effluents are also generated.The basic oxygen furnace is responsible for 60% of all steel produced. This sector is the second largest generator of solid waste from an integrated steel mill, contributing with 27% of solid waste generated in a plant ( 5-7 million tons of waste generated annually worldwide) [2,3,4]."

Jan 1, 2013

By P. J. Mackey

New and emerging, as well as proven technologies for the smelting of copper, nickel, lead and zinc are briefly reviewed. The number of new technologies available today is greater than at any time in the past, and interest and development activities remain high despite the economic dif-ficulties faced by the non-ferrous metallurgical industry. Part of the impetus is provided by the realization that only the most cost effective producers will remain competitive, and that new technology is one key to cost effectiveness. The commercially proven "new" copper smelting processes can now be considered to be conventional- technology, and are expected to dominate copper smelting for acme time. There is a growing. interest in continuous copper converting, although direct smelting and converting to copper in one vessel remains the- ideal. There is little activity in nickel smelting. After many years. of development, it appears that several new direct lead smelting processes will soon be a commercial reality. The electrolytic zinc process is expected to continue its dominance, although there is a renewed interest in pyrometallurgical approaches. One of the new zinc processes, and a molybdenum smelting process, illustrate the possibilities of using plasma technology in non-ferrous metallurgy. In the area of complex sulphides, there is perhaps less interest in the treatment of bulk con¬centrate, and more in the treatment of so-called dirty copper concentrates. Much of the technology ancillary to smelting has remained relatively unchanged, and more effort must be made to advance the technology in areas such as materials handling, gas cleaning and sulphur fixation, and energy recovery. More attention to engineering design is also needed. Escalating capital costs may make mini-smelters attractive, but imaginative technology and innovative engineering will be required to make them cost effective. Finally, a glimpse is offered of the smelter of the future.

Jan 1, 1983

By Ahmad-Bitar¸ Riyad N., Shadia J. Ikhmayies

"CdSi-xTex thin films with O<x<0.3 were prepared on glass substrates by the annealing of CdS:In thin films produced by the spray pyrolysis technique. The annealing was performed in nitrogen atmosphere at 400 --,C in the presence of Te vapor. The compositions of the films were determined by energy dispersive X-ray detection (EDAX) measurements. Scanning electron microscopy (SEM) was used to investigate the morphology of the films. The transmittance of the films was measured at room temperature in the wavelength range 400-1100 nm and used to produce the absorbance of the films. The first derivative of the absorbance was used to estimate the optical bandgap energy Eg by using the minima in the first derivative. The relation between the bandgap energy and the fraction x was found to fit with a parabola and bandgaps in the range 2.196: =Eg: =2.480 e V were obtained. Urbach tailing in the bandgap was also investigated.IntroductionPolycrystalline thin film CdS/CdTe solar cells are promising candidates for low cost and high efficiency photovoltaic applications. The fabrication process of these cells involves the deposition of a p-type CdTe absorber layer on top of an n-type CdS one which acts as a window. The efficiency of the solar cell is affected by the method of preparation of both layers [1, 2].Interdiffusion processes taking place at the CdS/CdTe interface have largely been realized to significantly affect the device performance [3] by changing the bandgap of both CdTe and CdS which modifies the spectral response of the solar cell [ 4]. The formation of a mixed crystal or a graded layer causes a reduction in the lattice mismatch at the CdS/CdTe junction [5] which is about 9% [ 6] and then a reduction in the number of interfacial states and recombination centers, thus enhancing the solar cell performance [7, 8]. A complete understanding of the properties of the intermixed layers CdSxTe1-x that usually constitutes the interfacial region in the CdS/CdTe solar cell is essential. According to our knowledge, a lot of research was devoted to the investigation of the diffusion of S into CdTe [3-5, 9]; but little on the direct investigation of the diffusion of Te into CdS [6]."

Jan 1, 2011

By Susumu Nagae, Hajime Ikeda

Recently, a number of mine development projects have been setback by social, economic and, environmental circumstances that had not been seen before. Many of these problems do not always originate from direct mine pollution. Typical examples of these are· conflicts between the exploration company and the local residents, sudden objections just before the development is to begin, and unexpected tightening of environmental regulations. The common background to these problems is expanding global environmental awareness. This includes complex factors ·such as the expansion of exploration to remote regions, the brisk activities of environmental NGOs, the increase of international environmental laws and, governmental policy changes. Today, the range of issues concerning mine development is widening significantly. The participation of local residents arid NGOs in the development planning, together with the company and government, has become essential for smoothly carrying out mine projects and making them more beneficial for stakeholders. Introduction The common image of the environmental problem with respect to mining is direct mine pollution, such as the collapse of tailings dams, pollution from refineries, and acid mine drainage. All over the world, the mining industry has made large investments in capital and technology to solve and prevent mine pollution, and these efforts have been making steady achievements. However in recent years, new cypes of environmental problems which are not originating directly from mine pollution are emerging frequently. Most of the problems are concentrated at the exploration stage to early stage of development, which have less impact on the environment. In the worst case, mining project may be forced to cancel and could cause serious damage to the industry because they could not collect their investment. I would like to take a general view of the examples of new types of trouble, their characters, background, and strategies against these problems.

Jan 1, 2000

By Johne Jesus Mol Peixoto, Ciro Azevedo Silva, Itavahn Alves da Silva, Weslei Viana Gabriel, Leticia Queiroz Ribeiro, Carlos Antonio da Silva, Varadarajan Seshadri

In this study,the influence of the immersion depth, casting speed on the flow characteristics in a beam blank mold with two tubular nozzles have been investigated using a physical model as well as CFD simulations.The results of CFD simulations were found to be consistent with the results of experiments in the physical model.The liquid jet spreads faster the flange region compared to the web region. This can lead to a non-uniform shell thickness along the cross section resulting in uneven solidification of the skin. The jet penetration depth ranged between 66 and 77 cm. The average intensity of meniscus fluctuation was 0.22 mm, and the maximum fluctuation was found to be 0.85 mm. Based on these results, the suggested optimum operating parameters for immersion depth and casting speed were 75 mm and maximum casting speed of 1 m/min.

Mar 1, 2017

By John R. FitzPatrick

The separation and purification of uranium from either nitric acid or hydrochloric acid media tan be accomplished by using either solvent extraction or ion-exchange. Over the past two years at Los Alamos, emerging programs are focused on recapturing the expertise required to do limited, small-quantity processing of enriched uranium. During this period of time, we have been investigating ion-exchange as a method for extraction/purification of uranium from acidic media. In addition, waste stream polishing is associated with this effort in order to achieve more complete removal of the uranium prior to recycle of the acid. Extraction chromatography has been demonstrated&apos; to further polish the uranium from both nitric and hydrochloric acid media thus allowing for a more complete recovery of the actinide material and creation of less waste during the processing steps. We will discuss contact experiments for evaluation of eleven different resins for uranium removal from nitric acid, the evaluation (again by contact experiments) of uranium elution from the ion-exchange media by various chemicals, and small-scale experiments for the removal of 235U from nitric acid. Larger-scale (100-gram) flow experiments using depleted uranium, were done after the small-scale evaluation Of the selected resin. A discussion is also included concerning the shortcomings of the contact experiments and how the flow experiments were modified in order to overcome these problems. We will also discuss the application of ion-exchange for some specific process needs at Los Alamos Contact experiments were used to evaluate some commercially available solvent-impregnated resins in addition to evaluation of several resins of this type synthesized in our laboratory. These experiments&apos; involved both nitric and hydrochloric acid media. The data from these experiments will be used to determine the column size and&apos; amount of resin required to polish the waste stream produced by the ion-exchange process described above. Small-scale flow experiments will be described and data given on the mass balances achieved using this two step process. Future work for evaluation of new ion-exchange and solvent-impregnated resins as well as the search for new eluants will be discussed. Other future experiments for both processes, including large-scale experiments, will be discussed in detail.

Jan 1, 1996

By Xiang Li, Merete Tangstad

Currently, the main carbonaceous material for Mn-alloys production is solid carbon, i.e. coke, charcoal and petroleum coke, which is produced with large CO2 emissions. Due to the simple purification, high carbon activity and low CO2 emissions, natural gas has some advantages compared with conventional reducing agents. The aim of the present project is to develop a new technology for production of Mn-alloys using natural gas as a source of carbon. Experimental results indicated that injection of CH4 gas directly into melted slag reduced slightly the MnO and SiO2. However, the metal yield was much less than the theoretical value due to a relative low residence time of CH4 in the slag. The alternative approach was to use carbon black as reductant, produced by CH4 decomposition. The preliminary experimental results showed a high reduction rate using carbon black.

Mar 1, 2017

By Felipe Perissé Duarte Lopes

The tensile properties of DGEBA/TETA epoxy matrix composites reinforced with different amounts of curaua fibers were evaluated. Tensile specimens with up to 35% in volume of long, continuous and aligned curaua fibers were room temperature tested in an Instron machine. The fracture was analyzed by SEM. The results showed significant changes in the mechanical properties with the amount of curaua fibers. This was compared to other bend-tested composites with distinct matrices. The fracture analysis revealed a weak fiber/matrix interface, which could be responsible for the comparatively low performance of some properties.

Jan 1, 2010

By Xi Zhang

A technique for fabricating free-standing, high-aspect-ratio porous and pillar-type Ni structures has been developed using wet Si processing. A wafer of (100) Si was initially etched in HF solution to form deep pores with micron-sized diameter. The aspect ratio can exceed 200. By introducing the as-etched Si into a defined aqueous Ni2+ solution, Ni deposits grew rapidly onto the sidewalls and replaced the Si. Long-time immersion allows the Si sidewalls to be completely converted and thus form a metallic Ni structure with high-aspect-ratio pores. It is known that close-packed submicron Si pillars can be formed by oxidizing and subsequent etching of the macropore sidewalls. Treated in the same Ni solution, high-aspect-ratio Ni pillars were correspondingly emerged by replicating the original pillar-type Si structure.

Jan 1, 2006

By J. W. Bridge

Triaxial compression tests at various confining pressures and temperatures, as well as tangent modulus tests using ultrasonic waves, were conducted for wax-coated granular composite materials. The material used is a surface for Thoroughbred horse racing. The purpose of these tests is to examine how track shear strength and tangent modulus at a range of loads respond to changing temperatures. Previous work has shown that a wide range of operational temperatures are experienced which have been reproduced in the lab. Using differential scanning calorimetry, it is confirmed that these operational temperatures correspond to distinct thermal transition regions for the wax that is used to coat the sand in these surfaces. Preliminary results show that both shear strength and tangent modulus are sensitive to temperature changes with maximum strength and modulus correlating with major DSC wax transition regions.

Jan 1, 2010

By J. M. Tannenbaum

A depth-sensing micro-indentation technique is developed for evaluating mechanical properties of materials at elevated temperatures (to 1200°C). System description and design considerations of the test apparatus are described. Based on Hertzian spherical indentation approach, the micro-indentation test apparatus is capable of determining Young?s modulus and creep strength of test materials with flat, tubular, or curved architectures from room to 1200°C under either air or controlled gaseous environments. Calibration tests were conducted on a H13 Tool Steel coupon from 22°C to 500°C and single crystal Haynes 230 alloy at 1000°C with excellent agreement to the literature values. Indentation creep tests of Haynes 230 alloy were carried out at 1200°C with preliminary results showing good correlation to creep exponents. Further system refinements will be investigated, and additional testing will be conducted.

Jan 1, 2010

By Daniel S. Gwinner

The tolling, or processing for a fixed fee, of aluminum drosses to recover the metal units is a common practice in the Aluminum Industry. The Dross Toller is acting for the owner, and since most dross processes result in material going to landfill, it is important for the owner of the dross to insure that the toiler is processing the material and handling waste disposal in an environmentally responsible manner. The paper discusses the Dross Toiler Audit Program, first from the Reynolds Metals Company perspective. Included are the reasons the company deems it necessary to audit and a description of the items covered during the audit. Finally, there will be a discussion of the audit from the Tollers perspective - what the Toiler can expect when the auditor arrives.

Jan 1, 1995

By G. Granata

In this work, we studied the recovery of copper from AMD by cementation with iron powder. To control the size of copper particles within the nanoscale range, we tested the use of the anionic surfactant sodium dodecyl sulfate (SDS). We tested three concentration levels (0.2, 0.4 and 0.6 M) and temperatures (25, 50 and 75 °C). The activation energy of cementation was also assessed by fitting the experimental data with the Arrhenius equation. Under all investigated conditions, the cementation reaction was found to be a diffusion-controlled process. Without surfactant, the activation energy was 19.9 kJ/mol. In the presence of SDS the activation energy increased up to about 35 kJ/mol. With or without SDS, the particle size of the copper product was strongly affected by the cementation temperature. Without SDS, the cemented product aggregated into micro-sized clusters of about 15 μm at 25 °C, 2–3 μm at 50 °C and 1 μm at 75 °C. The addition of SDS resulted in a dramatic decrease of copper particle size up down to the nanoscale range. Under the best operating conditions, the particle size of copper was <100 nm.

By Maria das Graças da Silva-Valenzuela, Mathilde Julienne Gisele Champeau Ferreira, Simeão Lopes Ferreira, Francisco Rolando Valenzuela-Díaz

The use of clays to formulate powder coating can improve physical properties, besides a final product with more sustainable characteristics due to the elimination of some additives, which may be substituted for the clay. We investigate the use of a modified smectite clay to formulate powder coating based on polyester resin. Four compositions of incorporated claywere evaluated (0, 4, 7, and 10wt%). Powder coating were prepared in a twin-screw extruder at 105 °C, and characterized by XRD, FTIR and SEM. Tests of flexibility, adhesion and impact strength in accordance to ASTM standards were performed. Diffractograms of the samples showed the characteristic peak of the modified smectite in d(001) * 37°(2h), indicating exfoliation of the clay. Micrographs by SEM showed the presence of lamellar structure for the clay-based powder coating.Mechanical assays were found for all analyzed coatings, indicating that sample containing 7% of clay presents the best performance.

Mar 1, 2018

By J. Samir

The objective of this study is to simulate the isothermal filling up of moulds by a RTM process when adopting CV/FEM and VOF method and when also taking into account the presence of obstacles coupled to the effect of the thickness and reinforcement layers variation. The codes developed intended to ensure an optimal positioning of the injection points and of the vents and also to determine optimal injection pressures, in order to minimize the cycle times. These codes use a mesh generator proper to the team, allowing a discretization of the domain in triangular unstructured elements, with the possibility of a local refinement and inserts inclusion.

Jan 1, 2009

By Peter Willbrandt

The flash smelter at NA was commissioned in March 1972 with an initial throughput of 50 tons of dry copper concentrate per hour. As a result of various measures, for example, oxygen enriched process wind, extension of the radiation part of the waste heat boiler, etc., the throughput could be increased to the present 70 tons per hour of dry concentrate. NA&apos;s plant is located on the outskirts of the city of Hamburg. The flash smelter&apos;s location and the growing awareness of the German population as regards environmental issues necessitate again and again considerable capital expenditure being spent on environmental protection. Thanks to the numerous small and large measures taken to protect the environment the emissions of dust, heavy metals such as arsenic, copper, lead, etc., and as well SO, could be drastically reduced. This paper will be giving an overview on the present state of the flash smelting process and the impact of the increasing environmental awareness at NA.

Jan 1, 1993

By Teuku A. R. Putra, Patrick R. Taylor

Various pyrometallurgical methods for treating copper concentrates that contain appreciable arsenic are reviewed. Various aspects of the engineering of these treatment methods are discussed. The methods discussed include: complete oxidation with arsenic fixation; selective volatilization of arsenic; acid baking, soda ash roasting, and others methods. Methods for the ultimate disposal, or marketing, of the arsenic are discussed.

Jan 1, 2014

By N. G. Azeredo

This work dealt with the evaluation of engineering structural clay brick samples that were sintered at estimated temperatures of 700 and 800°C. They were collected in a red-brick plant in Campos dos Goytacazes, RJ, Brazil. From a lot, a sample already sintered in its kiln at 700°C were collected and also a sample from the same lot only dried by the air, which were then sintered at 800°C controlled temperature. The samples were subjected to Brazilian Standard tests (ABNT NBR 15270:2005) to determine their geometric, physical and mechanical properties. In order to be classified as structural clay brick it is required minimum 3.0 MPa for the characteristic compressive strength (fbk) to be suitable for up to five floors structural building applications. We also used the Weibull Probability Plot and Weibull Maximum Likelihood Estimation to evaluate distribution parameters in order to compare the results of compressive strength obtained in the tests.

Jan 1, 2015

By Dong Joon Min, Joo Hyun Park, Mi Sun Choi, Jae Hong Shin

Sublimation of ZrCl4 is important for the production of nuclear grade metallic Zr in Kroll’s process. The sublimation kinetics of ZrCl4 was investigated by TGA under both isothermal and non-isothermal conditions. The sublimation rate of ZrCl4 increased with increasing temperature under isothermal conditions. ZrCl4 sublimation was confirmed to be a zero-order process under isothermal conditions, whereas it was first-order kinetics under non-isothermal conditions. The activation energy of ZrCl4 sublimation under isothermal conditions was 21.7 kJ/mol. The activation energy for non-isothermal sublimation was 101.4 kJ/mol and 108.1 kJ/mol with the Kissinger method and Flynn- Wall-Ozawa method, respectively. These non-isothermal activation energies were very close to the heat of sublimation (103.3 kJ/mol). Sublimation occurs by two elementary steps: surface reaction and desorption. Therefore, the overall activation energy of ZrCl4 sublimation is 104.8(±3.4) kJ/mol. The activation energy of the surface reaction and desorption steps are proposed to be 83.1 kJ/mol and 21.7 kJ/mol, respectively.

Jan 1, 2014

By A. M. Ramalho

In the synthesis and sintering processes to obtain superhard materials, such as diamond and cubic boron nitride, deformable ceramic capsule is used as gasket to transmit and support the required high pressures and high temperatures, HPHT. The ceramics materials for these capsules should have special physics and chemical characteristics such as refractoriness, shear strength and compressibility. In this work, Bridgman?s anvil made of hard metal or speed steel was used to characterize some ceramics materials in terms of their maximum compressible thickness. Tests were also performed with different resin polymers used as binding mixture with ceramics powder. Chemical analyses and investigations through scanning electronic microscopic (SEM), X-ray and real tests for the synthesis of diamond were also performed. The results showed that local Brazilian calcite can be successfully used in the manufacture of HPHT gaskets.

Jan 1, 2006