DEMET - Artigos publicados em periódicos

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Lixiviação ácida de elementos terras raras presentes em resíduos de equipamentos elétricos e eletrônicos : uma breve revisão.
(2022) Gomes, Rodrigo F.; Pereira, Matheus Mello; Leão, Versiane Albis
The accelerated expansion of the use of electronic products has generated large amounts of Waste Electrical and Electronic Equipment (WEEE), which makes the use of management strategies based on Circular Economy (CE) essential. In this sense, the recycling of these residues is of great interest due to the presence of metals with high added value, such as Rare Earth Elements (REE). Given the above, this review aims to elucidate issues related to the management and processing of WEEE and to evaluate the main parameters that influence the leaching step of REE present in these wastes. From the critical analysis of the bibliographic survey, it was noted that fluorescent lamps, cathode-ray tubes, NbFeB magnets and NiMH batteries are widely studied, with the objective of recovering REE. However, considerable variations were observed with regard to the content of metals present in each of these residues. In short, it is important that the recovery of these metals is studied, not only due to economic aspects, but also aiming at environmentally sustainable recycling.
On the cobalt content upgrade in nickeliferous laterites using iron (III) sulfate : a study based on thermodynamics simulations.
(2022) Souza, Rodrigo Fernandes Magalhães de; Tavares, Mariana Aguiar de Azevedo; Cruz, Luiz Eduardo Carnevale; Oliveira, Víctor de Andrade Alvarenga; Santos, Iranildes Daniel dos; Moura, Francisco José; Brocchi, Eduardo de Albuquerque
Nickel (Ni) and cobalt (Co) are relevant technological metals for the future of the lithium-ion battery (LIB) industry. Based on the current and projected demand for these, an increased interest in developing processing routes to exploit lateritic occurrences has been observed, as these are reported as critical raw materials for future mineral–metallurgical industry. However, the content of Ni and Co in such ores is minimal and requires impracticable mineral-processing operations for concentration before metal extraction. It was identified that information regarding the sulfation roasting of this material is scarce on what concerns the iron sulfates interaction as a function of the temperature. Based on that context, the present work has its purposes associated with the proposition of an alternative chemical pretreatment to upgrade the content of metals of technological interest in lateritic ores through a simple roast–leach process. Thus, the chemical interactions between the mineral sample and iron (III) sulfate (Fe2 (SO4 )3 ) through thermodynamic simulations and experimental procedures were explored. The latter included specific water leaching practices for the selective concentration of metals. The equilibrium calculations indicate that Fe2 (SO4 )3 and FeSO4 tend to decompose at lower temperatures, and considering the higher stability of other metal sulfates, it could be an interesting reagent in this type of process. Regarding the experimental results, the characterization of materials indicates a recovery of Co as high as 73.4 wt.% after sulfation roasting at 500 ◦C followed by water leaching, with the full content of Iron (Fe) being reported in the insoluble phase. Based on these findings, the present development could be an interesting alternative to consider within operations for the chemical upgrade of cobalt in such types of mineralogical occurrences.
Diversidade da comunidade de macroinvertebrados bentônicos no reservatório de Volta Grande, Bacia do Baixo Rio Grande.
(2022) Camargo, Paulo Ricardo da Silva; Barbosa, Newton Pimentel de Ulhôa; Cardoso, Antônio Valadão; Assis, Paulo Santos; Pelli, Afonso
A comunidade de macroinvertebrados bentônicos é composta por alguns organismos mais sensíveis e outros mais resistentes as mudanças ambientais. Nesse sentido, são utilizados como bioindicador. O presente trabalho teve como objetivo verificar a diversidade de espécies local (diversidade alfa) da comunidade de macroinvertebrados em dois trechos da Bacia do Baixo Rio Grande com composição de substrato distintos. O estudo ocorreu em dois pontos da Bacia do Baixo Rio Grande. No ponto 1 foram coletadas amostras de sedimentos ao longo de doze meses, onde foram calculados o índice de diversidade dos parâmetros riqueza (S), abundância, dominância, diversidade de ShannonWiener (H'), diversidade de Simpson (D') e equitabilidade (J) e por meio da análise não paramétrica Kruskal-Wallis foram comparados entre todos os meses do ano e também estação chuvosa e de estiagem. No ponto 2 foram coletados substratos artificiais e foram calculados os índices de diversidade, compreendendo também as estações chuvosas e de estiagem. No ponto 1 não houve diferença significa entre as estações chuvosas e de estiagem, mas apresentou diferenças entre a abundância e equitabilidade entre todos os meses amostrados. No ponto 2 foi evidenciado que o valores dos índices de diversidades se apresentaram maiores nos meses de estiagem. Em síntese, foi inferido que as comunidades bentônicas podem estar sob o reflexo da homogeneização ambiental resultantes das atividades antrópicas. Portanto, esses índices de diversidades podem ser uma ferramenta adequada para compreender o ambiente, e assim fomentar decisões mitigadoras em prol da conservação das espécies mais assertivas.
The Bauschinger effect magnitude control in ultra-low carbon steel wires.
(2023) David, Felipe Farage; Cordeiro, Rafael de Oliveira; Vasconcelos, Luan Marcel Costa; Batista, Ben Dêivide de Oliveira; Liberato, Frank de Mello; Costa, Adilson Rodrigues da
The cold roller die process increases the tensile strength and decreases the ductility of steel wire. Annealing heat treatment is applied to restore mechanical properties, but this is a costly process. This research shows that it is possible to control the mechanical properties of ultra-low carbon steel wire inducing the Bauschinger effect and relieving residual steel stresses. The present study uses several pulleys to promote and control the Bauschinger effect magnitude through alternated cyclic bending. A Completely Randomized Design, a regression study, and the Akaike Information Criterion were used to understand the relationship between the quantity and diameter of pulleys and the influence on the magnitude of the Bauschinger effect. Statistical models showed that it is possible to have a maximum increase of 103% in uniform elongation and a maximum decrease of 14% in yield strength. An interaction between the factors studied in controlling the Bauschinger effect magnitude was confirmed.
Effect of thermal aging on the microstructure and mechanical properties of stainless steel UNS S31803.
(2020) Costa, Junia Maria Gândara; Lacerda, José Carlos de; Godefroid, Leonardo Barbosa; Cândido, Luiz Cláudio
Duplex stainless steel UNS S31803 exhibits high mechanical strength with high corrosion properties, due to its microstructure composed of ferrite and austenite phases, in equal proportion. When the UNS S31803 steel is submitted to high temperatures, some precipitations can occur, such as nitrites, carbides, and third phases (e.g. sigma phase -σ, and alpha prime - α'). These phases are deleterious in relation to the mechanical properties and corrosion resistance, and their effects are analyzed regarding the properties of the steel. In order to evaluate the precipitation of this deleterious phase, isothermal treatment was done at 500°C for 144 hours (α' phase) and at 850ºC for 80 minutes (σ phase). The results were obtained through the microstructural analysis and tensile tests. The presence of sigma phase was verified in the grain boundary, an increase in the mechanical resistance with a loss of toughness. There was as well as an increase in mechanical resistance with the precipitation of α', with less loss of ductility than that observed in the experiments involving the presence of sigma phase.
Effect of niobium on microstructure and mechanical properties of a hypereutectoid steel.
(2022) Pessoa, Ricardo Amorim; Porcaro, Rodrigo Rangel; Cândido, Luiz Cláudio; Pereda, Beatriz; Lopez, Beatriz
High-carbon steels have been used to high-strength steel wire and strands for prestressing concrete. The necessity of high-strength levels at increasingly larger diameters of wire rods is a technological challenge. Two steels with and without Nb were obtained in a steel mill, submitted to detailed microstructural (previous austenitic grain size, pearlite interlamellar spacing and colony size) and mechanical characterization through tensile tests and hardness. Hot torsion and dilatometry tests were performed to simulate steels processing and to verify the influence of Nb on phase transformation. Adding Nb to steel resulted in a refinement in austenitic grain size and pearlite colonies but had no effect on pearlitic interlamellar spacing. There was a decrease at the start transformation temperature austenite/pearlite and therefore an increase in the hardenability of the Nb-added steel. Finally, Nb addition proved to be a technical and economical way to increase tensile strength and to reduce the variability of the mechanical properties.
Production of a non-stoichiometric Nb-Ti HSLA steel by thermomechanical processing on a Steckel mill.
(2023) Martins, Cleiton Arlindo; Faria, Geraldo Lúcio de; Mayo, Unai; Isasti, Nerea; Uranga, Pello; Rodríguez Ibabe, Jose Maria; Souza, Altair Lúcio de; Cohn, Jorge Adam Cleto; Rebellato, Marcelo Arantes; Gorni, Antônio Augusto
Obtaining high levels of mechanical properties in steels is directly linked to the use of special mechanical forming processes and the addition of alloying elements during their manufacture. This work presents a study of a hot-rolled steel strip produced to achieve a yield strength above 600 MPa, using a niobium microalloyed HSLA steel with non-stoichiometric titanium (titanium/nitrogen ratio above 3.42), and rolled on a Steckel mill. A major challenge imposed by rolling on a Steckel mill is that the process is reversible, resulting in long interpass times, which facilitates recrystallization and grain growth kinetics. Rolling parameters whose aim was to obtain the maximum degree of microstructural refinement were determined by considering microstructural evolution simulations performed in MicroSim-SM® software and studying the alloy through physical simulations to obtain critical temperatures and determine the CCT diagram. Four ranges of coiling temperatures (525–550 ◦C/550–600 ◦C/600–650 ◦ C/650–700 ◦C) were applied to evaluate their impact on microstructure, precipitation hardening, and mechanical properties, with the results showing a very refined microstructure, with the highest yield strength observed at coiling temperatures of 600–650 ◦C. This scenario is explained by the maximum precipitation of titanium carbide observed at this temperature, leading to a greater contribution of precipitation hardening provided by the presence of a large volume of small-sized precipitates. This paper shows that the combination of optimized industrial parameters based on metallurgical mechanisms and advanced modeling techniques opens up new possibilities for a robust production of high-strength steels using a Steckel mill. The microstructural base for a stable production of high-strength hot-rolled products relies on a consistent grain size refinement provided mainly by the effect of Nb together with appropriate rolling parameters, and the fine precipitation of TiC during cooling provides the additional increase to reach the requested yield strength values.
Abrasiveness of iron ores : analysis of service-worn conveyor belts and laboratory Dry Sand/Rubber Wheel tests.
(2022) Nins, Barbara; Penagos, Jose Jimmy; Carneiro, Leandro Moreira; Münch, Daiane; Falqueto, Patrick; Viáfara, Cristian Camilo; Costa, Adilson Rodrigues da
Belt conveyors are currently one of the most commonly used technologies for transporting iron ore. Of the components of the conveyor system, the belt is the most expensive and susceptible to damage. Failures due to wear of the rubber cover lead to downtime for corrective maintenance, greater operational risks and performance and economic losses. To improve the tribological performance of conveyor belts, it is necessary to know the main parameters that influence their wear. As wear behavior is not an intrinsic property of a material, the most reliable results are obtained when the wear mechanisms produced in laboratory tests are similar to those in service. In this work, two types were investigated of belt rubber, one new and one worn in service, and four types of iron ore in two class sizes. Loose abrasive wear tests were carried out using the Dry Sand/Rubber Wheel apparatus with belt rubber test pieces and iron ores as abrasives. This work characterized the wear mechanisms that occur in service and in laboratory tests. The predominant wear mechanism found was the formation of Schallamach waves. In the wear tests, Friable Hematite samples presented the highest abrasiveness. In addition, the chemical, mineralogical and morphological features of the iron ore samples were characterized. The high abrasiveness of Friable Hematite was possibly due to the mineral assembly.
Thermal stability of copper processed by multidirectional forging : effect of deformation amplitude and cumulative strain.
(2022) Flausino, Paula Cibely Alves; Corrêa, Elaine Carballo Siqueira; Pereira, Pedro Henrique Rodrigues; Aguilar, Maria Teresa Paulino de; Cetlin, Paulo Roberto
Experiments were performed in order to evaluate the effect of deformation amplitude (Δε) and cumulative strain (ε) on the thermal stability of Copper 99.8% pure, after processing with 8 and 48 Multidirectional forging (MDF) cycles at room temperature with Δε ≈ 0.075 (MDF0.075) or 2 and 12 MDF cycles with Δε ≈ 0.30 (MDF0.30), leading to cumulative deformations of ε ≈ 1.8 and 10.8. The microstructural stability at elevated temperatures was evaluated through Differential Scanning Calorimetry (DSC) and heat treatments, combined with Vickers microhardness measurements and Electron Backscattered Diffraction (EBSD). Further analyses were carried out through thermodynamic considerations about the stored energy and driving pressures for boundary migration. The results showed that the thermal stability associated with static recrystallization decreases as ε and Δε in MDF increase, due to the presence of finer grain structures and higher dislocation density in the as-deformed material. In addition, the MDF-processed specimens deformed with high ε and Δε exhibited finer recrystallized grains than those processed with low ε and Δε as a result of their increased number of nucleation sites. Thermal stability increases in the following order: 12C-MDF0.30, 2C-MDF0.30, 48C-MDF0.075 and 8C-MDF0.075.
Slag-steel emulsification on a modified RH degasser.
(2021) Silva, Antonio Marlon Barros; Oliveira, Mateus Assis; Peixoto, Johne Jesus Mol; Silva, Carlos Antônio da
A new arrangement of RH snorkels is proposed in order to improve the slag metal interaction. According to this RHDeS design, the steel jet flowing down from the vacuum chamber discharges inside the slag layer. Physical modeling of a reactor following this concept was performed. Mixing times, circulation rates, and the mass transfer coefficient were evaluated as well as the droplet residence time. Mixing times and overall circulation are not very much affected by the modifications. However, the modification brings about a large and sustainable dispersion of slag (oil) in metal (water). The influence of this dispersion on de-S was assessed. A lumped kinetic parameter KA=vw was evaluated in order to quantify the process kinetics. Kinetics can be improved by one order of magnitude. It is suggested that proper slag (amount and basicity) allied to this geometric modification could be fruitful to sulfur removal from deoxidized steel. Simulations show that sulfur removal with this RHDeS arrangement is expected to be higher than with schemes where de-S reagents are added in the vacuum chamber.
Efeito da temperatura de austenitização intercrítica sobre a cinética de transformação martensítica e evolução microestrutural de um aço API-OCTG grau K55.
(2023) Schuttenberg, Arthur Cançado; Lima, Verônica Stela da Silva; Rocha, José Márcio da; Faria, Geraldo Lúcio de
Aços API-5CT grau K55 são especificados para tubos de revestimento de poços de exploração de óleo e gás. Eles podem ser fabricados por laminação sem costura, seguida de têmpera e revenimento (processo clássico). No entanto, diversos segmentos industriais têm apontado a utilização de microestruturas bifásicas (ferrita-martensita) como uma alternativa para melhorar a relação resistência mecânica-tenacidade de diversos produtos. Considerando a possibilidade de obtenção de um tubo bifásico por meio da aplicação de têmpera após austenitização intercrítica, este estudo pioneiro investigou o efeito da temperatura de austenitização intercrítica sobre as frações de fases e a cinética de transformação martensítica de um aço API-5CT grau K55. Concluiu-se que, para este aço, a faixa de temperatura de austenitização intercrítica está compreendida entre 750 °C e 820 °C. Verificou-se um aumento significativo nas temperaturas Ms e Mf , assim como da fração de martensita com a elevação da temperatura de austenitização. Em relação à cinética de transformação martensítica, concluiu-se que o efeito autocatalítico no início da transformação é mais atuante quanto maior a temperatura de austenitização. Modelos de previsibilidade que descrevem a evolução das temperaturas Ms e Mf , assim como da cinética de transformação martensítica, em função da condição de austenitização, foram aplicados com sucesso.
Characterization of flotation tailings from Samarco and other varieties of sand for use in sand molding in the foundry industry.
(2019) Figueiredo, Ricardo Augusto Martins; Oliveira, Sávio José de; Silva, Guilherme Francisco de Sales; Vieira, Cláudio Batista; Pinto, Maria Aparecida; Carneiro, Leandro Moreira; Seshadri, Varadarajan; Araújo, Denilson Rodrigues de; Vilela Neto, Gil Ribeiro
Foundry sand used for molding should have specific properties so that molds with adequate strength, porosity, etc to produce defect free castings. Thus, characterization of two types of flotation tailings from the mineral processing of itabirites and three types of base sand for molding have been carried out. The resulting properties have been compared to evaluate the suitability of use of typical flotation tailing for the molding process. The main properties determined are the grain shape and structure, chemical composition, grain size distribution, fineness modulus, fines content, moisture content and loss on ignition. Furthermore other properties of these sands prepared with binders have been compared like compactability, permeability and green compressive strength for green sand. For cold set and sodium silicate/CO2 processes properties like tensile strength and bending strength have been evaluated. The results show that the flotation tailing SA2 presented a good potential of use in the foundry.
Mineralogical characterization of iron ore tailings from the Quadrilatero Ferrifero, Brazil, by Eletronic Quantitative Mineralogy.
(2019) Ávila, Kelly de Souza Pires; Mendes, Jefferson Januário; Figueiredo, Vinícius Costa; Silva, Fabiane Leocádia da; Krüger, Fernando Leopoldo von; Vieira, Cláudio Batista; Araújo, Fernando Gabriel da Silva
The mineralogical characterization studies search for the best processing route, with the lowest environmental impact, aiming to improve the use of mineral resources. The electronic quantitative mineralogy (EQM) provides quickly and accurately great information about the characteristics of these materials. This work aims to characterize iron ore tailings by EQM as the main tool. It has selected seven samples of itabirite ores flotation tailings from the main mining regions of the Quadrilatero Ferrifero, Brazil. All samples were mostly composed by quartz and iron minerals, with a low presence of mixture particles of these minerals - less than 20% of the sample mass. Due to the difference between the size of particles of quartz and iron minerals, it has observed an opportunity to reprocess the fractions -37μm + 5μm of the studied tailings, with a potential recovery of 12% of the total sample mass generated for AM4, AM6 and AM7 and more than 5% for samples AM1, AM2, AM3 and AM5.
Capture of CO2 by vermiculite impregnated with CaO.
(2022) Pereira, Matheus Henrique Simplício; Santos, Cláudio Gouvêa dos; Lima, Geraldo Magela de; Bruziquesi, Carlos Giovani Oliveira; Oliveira, Victor de Alvarenga
Vermiculite samples were impregnated with different amounts of calcium oxide by the con- ventional thermal heating technique and subject to CO2 capture experiments in thermal analysis equipment. The amount of CO2 captured by calcium oxide increased from 13 g of CO2 per mol of CaO to 16.8 g of CO2 per mol of CaO when the experiments were carried out with pure calcium oxide and vermiculite impregnated with CaO (1:1), respectively. Integral isoconversional methods of Kissinger-Akahira-Sunose (KAS) and Osawa-Flynn-Wall (OFW) were used for the kinetic study of the process and good correlation coefficients were achieved. The apparent activation energy values showed that for low conversions (a < 0.3) the controlling step of the process is a mixed step where the chemical reaction and the dif- fusion of the reagents into the vermiculite have rates of the same order of magnitude (20 kJ < Ea < 40 kJ). For higher conversions values (a > 0.3) the apparent activation energy values suggest that the slow step is a chemical step (Ea> 40 kJ).
Recovery of metallic lead of cupel wastes from gold analysis by alkaline fusion in the presence of sulfur.
(2022) Cerceau, Cristiane Isaac; Carvalho, Cornélio de Freitas; Varejão, Eduardo Vinícius Vieira; Santos, Claudio Gouvea dos; Oliveira, Víctor de Andrade Alvarenga
High precision and accuracy make Pb-Fire assay the method of choice for gold analysis in mineralogical samples. The second stage of this method, called cupellation, leaves the used container (cupel) highly contaminated with PbO. Since tons of cupel waste are generated annually from gold analysis worldwide, the disposal of such material constitutes a serious risk to the environment. In the present paper the recovery of the lead from cupel waste by means of an alkaline fusion in the presence of sulfur was evaluated considering the efects of the following variables: amount of NaOH and sulfur, time, and temperature. Gravimetric analyses indicated 81.3% (w/w) recovery of lead in the form of metallic lead from 5.00 g of cupel waste using 3.00 g of NaOH, 0.5 g of S8, after 15 min at 650 °C. During the process, sulfur promoted the reduction of lead oxide. After the process, both the cupel wastes and the resulting secondary wastes presented lead concentrations below the maximum limits determined by both Brazilian legislation and that followed by US Environmental Protection Agency, and can be considered safe for disposal. Furthermore, the proposed method allows cupel wastes to be converted from an environmental liability to a raw material for the production of metallic Pb.
Magnetic separation studies of a lateritic nickel ore.
(2021) Ramírez, Rafael Leonardo Silva; Santos, Claudio Gouvea dos; Lima, Geraldo Magela de; Pereira, Matheus Henrique Simplício; Oliveira, Victor de Alvarenga
Hydrogen reduction and thermal treatment experiments were carried out in the laboratory using a transition zone lateritic nickel ore. The products of the pyrometallurgical operations were subjected to magnetic separation. The ore and samples produced after the thermal processing (reduction and thermal treatment) were characterized by X-ray diffractometry (XRD), thermogravimetric analysis (TG), scanning electronic microscopy (SEM), and energy dispersive spectrometry (EDS). The qualitative identification of the main mineral transformations was performed and the influence of these thermal transformations in the magnetic properties of the sample was studied. When the reduction experiments were performed at 800 ° C, with a magnetic flux of 97.5 ± 10.6 mT, the nickel content increased by up to 33 % (recovery of ≈ 75 %) in the magnetic fraction. During the formation of magnetite in the reduction experiments, carried out at 400°C, the sample became very magnetic and, consequently, the unit operation of magnetic separation was not selective. It was possible to remove magnesium from all samples, regardless of the thermal treatment or reduction temperature used. The contents of this element were adjusted to the characteristic values of a limonitic ore.
Ultrastructure of the gill ciliary epithelium of Limnoperna fortunei (Dunker 1857), the invasive golden mussel.
(2022) Freitas, Erico Tadeu Fraga; Moreira, Amanda Maria Siqueira; Paula, Rayan Silva de; Andrade, Gabriela Rabelo; Carvalho, Marcela David de; Assis, Paulo Santos; Jorge, Erika Cristina; Cardoso, Antônio Valadão
Background: Limnoperna fortunei is a freshwater bivalve mollusc originally from southern Asia that invaded South America in the 1990’s. Due to its highly efcient water pumping and fltering, and its capacity to form strong adhe- sions to a variety of substrates by byssus thread, this invasive species has been able to adapt to several environments across South America, causing signifcant ecological and economic damages. By gaining a deeper understanding of the biological and ecological aspects of L. fortunei we will be able to establish more efective strategies to manage its invasion. The gills of the mollusc are key structures responsible for several biological functions, including respiration and feeding. In this work, we characterized the ultrastructure of L. fortunei gills and its ciliary epithelium using light microscopy, transmission and scanning electron microscopies. This is the frst report of the morphology of the epithe- lial cells and cilia of the gill of L. fortunei visualized in high resolution. Results: The analysis showed highly organized and abundant ciliary structures (lateral cilia, laterofrontal cirri and fron- tal cilia) on the entire length of the branchial epithelium. Mitochondria, smooth endoplasmic reticulum and glycogen granules were abundantly found in the epithelial cells of the gills, demonstrating the energy-demanding function of these structures. Neutral mucopolysaccharides (low viscosity mucus) were observed on the frontal surface of the gill flaments and acid mucopolysaccharides (high viscosity mucus) were observed to be spread out, mainly on the lateral tract. Spherical vesicles, possibly containing mucus, could also be observed in these cells. These fndings demonstrate the importance of the mucociliary processes in particle capture and selection. Conclusions: Our data suggest that the mechanism used by this mollusc for particle capture and selection could contribute to a better understanding of key aspects of invasion and also in the establishment of more efcient and economically viable strategies of population control.
Blast furnace’s replacement rate calculation for biomasses based on chemical and thermal properties.
(2021) Campos, Alex Milton Albergaria; Barbosa, João Paulo E.; Assis, Paulo Santos
The injection of pulverized materials in blast furnaces is a technique that has been used in iron making for reducing costs with reducing fuels and allows greater operational control. To be injected, the material needs some chemical, physical and thermal characteristics for the process. However, biomass presents as an economical and environmentally viable alternative to replace part of the coal used in this process. One variable analyzed in the reduction process is the replacement rate (RR), which is the amount of coke saved loading on the top of the reactor per quantity of material injected. There are some mathematical models for calculating the replacement rate based on properties, which are results of studies in determined blast furnaces. This work will show some calculations for replacement rate of biomasses using formulas from the literature. Some results show the technical feasibility for the use of biomass in blast furnaces.
Economic and environmental analyses of biomass torrefaction for injection as pulverized material in blast furnaces.
(2021) Campos, Alex Milton Albergaria; Khozhanov, Nietbai; Assis, Paulo Santos; Tursunbaev, Khambar; Masatbayev, Muratbek
Biomass was the first material used as a fuel by humanity, being replaced by fossil fuels after the industrial revolution. With the growing of environment discursions and the effects of CO2 emissions, biomass has been gaining strength as a potential alterna- tive to fossil fuels, especially for steelmaking, which is responsible for about 5 to 10% of all CO2 emitted. It is known that biomass, compared to fossil fossils, has a higher volatile content, high moisture and lower calorific value. On the other hand, it has a higher hydrogen content and lower sulfur content (important for the steel industry), in addition it is considered neutral in CO2 emissions. Torrefaction, heating biomass at a temperature between 200-280°C in an oxygen free atmosphere, is an interesting treat- ment to adapt biomasses for use in the steelmaking processes, mainly in the pulverized material injection into the blast furnace. PCI is an extremely important process for the production of iron in the blast furnace, due to its ability to reduce coke consumption and optimize the operation of the reactor. This article comes with the purpose of pre- senting a bibliographic review about PCI technique, torrefaction process, biomasses and its applicability in the steel industry. In addition, an economic and environmental analysis of the possible use of biomass in steelmaking processes will be presented. Results shows that the use of torrefied biomass in the injection process is interesting, generating savings of 10 dollars and reduction of 264kg in CO2 emissions per ton of hot metal, with a replacement of 50% of the coal used by biomass.
Steel desulfurization on RH degasser : physical and mathematical modeling.
(2022) Silva, Antonio Marlon Barros; Peixoto, Johne Jesus Mol; Silva, Carlos Antônio da; Silva, Itavahn Alves da
Due to the high-quality steel demand, especially for ultra-low Sulfur steel, RH desulfurization has been practiced. Based on this, mathematical and physical modeling have been applied to study steel desulfurization by reagent addition in the RH degasser vacuum chamber. The main result of cold modeling, using water and oil emulating steel and slag, respectively, was to assess the influence of density difference between the continuous and disperse phases on oil droplet behavior. It is shown that its flow tends to be more restricted near the down snorkel when the density difference increases. Moreover, these results provide the basis for CFD modeling validation, which enabled the determination of slag drop residence time inside steel on RH and the average value of the rate of dissipation of turbulent kinetic energy inside the RH ladle. These two pa- rameters were used to develop a kinetic model, which reaches a good agreement with industrial trial results available in literature. The optimum desulfurization degree of 31.44% was achieved for a gas flow rate of 90 Nm3 /h, according to the kinetic model. This value can be useful in some steel grade production, where the required S content is less than 10 ppm. Even in common steel grade production, if some punctual chemical adjustment is necessary, this technique is also useful. The main kinetic parameter for steel desulfurization is the steel circulation rate. For best results, it should be reduced in the desulfurization stage, and after that, the normal operation can be resumed, so that the production cycle is not affected.

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