DEMET - Departamento de Metalurgia

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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.
Adsorção de metais pesados em serragem de madeira tratada com ácido cítrico.
(2006) Rodrigues, Rafael Falco; Trevenzoli, Rafael Lopes; Santos, Luciano Rodrigo Gomes; Leão, Versiane Albis; Botaro, Vagner Roberto
Neste estudo, avaliou-se a capacidade da madeira Paraju (Manilkara longifolia), modificada quimicamente, para a retenção de íons metálicos. A modificação refere-se a um tratamento com ácido cítrico que leva à reação de grupos carboxilato com a celulose da biomassa. A introdução desses grupos foi observada através de espectrometria de infravermelho. Foram realizados ensaios em sistemas de batelada contendo cádmio e cobre. Os ensaios foram conduzidos em condições de equilíbrio, ajustados segundo o modelo de Langmuir. Obteve-se um carregamento máximo nos sistemas contendo apenas um metal, de 0,56 mmol-Cd/g e 0,94 mmol-Cu/g. O carregamento de cádmio reduziu-se de 0,56 mmol-Cd/g para 0,21 mmol-Cd/g, à medida que a concentração de cobre cresceu no sistema mostrando que existe uma competição entre os metais pelos grupos de troca.
Adsorção de níquel e cobalto em resina de troca iônica como alternativa para o tratamento de licor de lixiviação.
(2011) Siqueira, Priscila de Freitas; Silva, Carlos Antônio da; Silva, Itavahn Alves da
Estudou-se o emprego da resina PUROLITE S-930 como substrato para a remoção de níquel e cobalto de soluções sulfúricas. Experimentos de adsorção com diferentes razões [Ni]/[Co] mostraram uma maior seleção da resina em soluções mais ricas em níquel (Ni 600 mg/L - Co 800 mg/L). Isotermas de adsorção mostraram um aumento na capacidade de adsorção da resina em temperaturas mais elevadas (qmax Ni 0,28 mol/L, a 70ºC e qmax Co 0,18 mol/L, a 60ºC). Os valores de ∆H indicaram uma fisiossorção endotérmica. Para modelar a cinética de carregamento da resina, em leito fixo, utilizou-se o modelo de difusão superficial homogênea (Homogeneous Surface Diffusion Model - HSDM). Os resultados mostram um bom ajuste ao modelo, com kf = 5,2x10-6 m/s e DS = 4,5x10-12 m2/s, indicando que o carregamento da resina baseia-se em difusão na camada-limite e difusão nos poros da resina.
Aglomeração de moinha de carvão vegetal e sua possível aplicação em alto-forno e geração de energia.
(2008) Lucena, Daniel Avelar; Medeiros, Raphael Dias de; Fonseca, Urano Troseski; Assis, Paulo Santos
Este trabalho tem por objetivo analisar as características de briquetes de carvão vegetal a partir de resíduos siderúrgicos (moinha) e verificar a influência das mesmas sobre seus desempenhos quando submetidos ao processo de redução e oxidação. Para avaliar tais desempenhos, preconizou-se um índice denominado “índice de combustão” (ICOM), integrando num só valor o tempo de combustão, a temperatura gerada durante a combustão e a massa consumida para gerá-la. Para a caracterização dos briquetes foram determinados umidade, teores de materiais voláteis, cinzas e carbono fixo, poder calorífico, densidade, porosidade e resistência à compressão. Finalmente, analisar o briquete, por meio da equivalência energética. Desta forma pretende-se obter uma nova forma de reaproveitamento deste resíduo sob a forma de briquetes e sua possível viabilidade como redutor em alto-forno.
An evaluation of gas injection effects in a mechanically stirred hot metal desulfurization system.
(2017) Torres, Filipe de Menezes; Silva, Carlos Antônio da; Silva, Itavahn Alves da; Melo, Pedro Henrique Resende Vaz de; Lourenço, Marcelo Araújo
Physical modeling techniques have been used in order to assess the effects of gas injection as a means of optimizing mechanically stirred desulfurization processes. For such a 1:7 scale model of a 315 ton of a Kanbara reactor was built. The influence of gas injection on mixing times, gas – liquid interfacial kinetics and solid phase dispersion was evaluated. Gas injection can reduce mixing times up to 20% and can increase solid dispersion up to 40%. Gas liquid interaction is shown to be highly dependent on the gas injection location. In this regard injecting through the impeller or at the bottom of the ladle has been investigated. Gas injection can be beneficial to the desulfurization process.
Analysis of parameters affecting end blow manganese content at oxygen steelmaking.
(2008) Barão, Celso Dias; Silva, Carlos Antônio da; Silva, Itavahn Alves da
The end blow manganese behavior in BOF process has been assessed through analysis of an industrial data base. The available literature suggests that the main operational factors to influence the end blow manganese behavior in BOF are: manganese input, slag volume, oxidation level and temperature. The large extension of the industrial data base has made it possible to separate the influence for each factor. Then correlations between end blow manganese and these factors have been obtained.
Analysis of the fluid flow behavior within a beam blank mold using submerged-entry nozzle with three exit ports.
(2019) Gabriel, Weslei Viana; Peixoto, Johne Jesus Mol; Alves, Gesiane Letícia; Silva, Carlos Antônio da; Silva, Itavahn Alves da; Seshadri, Varadarajan
Through the use of physical and mathematical modeling techniques, liquid flow inside a beam blank mold with a submerged valve consisting of three exit ports has been analyzed. The behavior of the slag metal interface was evaluated using water and an aqueous NaCl solution to simulate steel. Slag simulation was done using silicon oil. Increased casting speed results in increased free surface oscillation. For the fluid density of 1,000 kg/m3, oil entrainment started at a casting velocity of 0.98 m/minute. For a fluid density of 1,170 kg/m3, no entrainment was observed in any of the conditions studied.
Analysis of the influence of biomass addition in coal mixture for metallurgical coke production.
(2021) Campos, Alex Milton Albergaria; Assis, Paulo Santos
Metallurgical coke is a common material used for hot metal production in blast furnaces. In addition to the fuel function, it has a physical assignment, supporting the load inside the reactor, and chemical, supplying carbon to hot metal. However, due to growing discourse on environmental issues, the production of hot metal via coke blast furnace has been in evidence. This process is responsible for about 70% of CO2 emissions in steelmaking. On the other hand, biomasses are materials that are available in different ways in nature and considered neutral in CO2 emissions since they absorb this gas and release oxygen in the photosynthesis process. Thus, a viable alternative in the short term is the partial replacement of the coal used in coke production with biomass, which would generate environmental gains, and guarantee the sustainable production. Therefore, this work aims to show several published researches using biomass in coke production. The effects that biomass has on the properties of coke will be emphasized, and at the end, an environmental analysis will be shown with the possible use of biomass. It will be possible to see that it is possible to substitute between 2 and 10% of the coal for biomass, producing coke with the characteristics required in the blast furnace.
Aplicação do modelo do núcleo não reagido à lixiviação da calcopirita pelo íon Fe+3.
(2015) Porcaro, Rodrigo Rangel; Martins, Flávio Luiz; Leão, Versiane Albis
A lixiviação da calcopirita pelo íon férrico é um processo considerado lento e com baixa recuperação de cobre, fato atribuído à passivação do mineral. Nesse sentido, o presente trabalho investiga a cinética de lixiviação de uma amostra de calcopirita de elevada pureza, utilizando sulfato férrico como oxidante. Os efeitos da agitação, temperatura, Eh e concentração de Fe3+ na extração de cobre foram avaliados. Os dados experimentais seguiram o modelo do núcleo não-reagido com controle por difusão na camada de cinzas e alta energia de ativação (103,9±6,5kJ/mol), provavelmente devido à não consideração do efeito da distribuição de tamanhos de partículas (PSD) nas equações cinéticas. A aplicação da hipótese do estado quasi-estacionário em sistemas líquido-sólido bem como o efeito da PSD na interpretação dos dados cinéticos são discutidos.
Application of sodium - and biogenic sulfide to the precipitation of nickel in a continuous reactor.
(2013) Gonzaga, Flávia Donária Reis; Silva, Adarlêne Moreira; Cunha, Emanoelle C.; Leão, Versiane Albis
Attention has been focused in recent decades upon the precipitation of metal sulfides from acid mine drainage (AMD) and pregnant leach solutions, due to the advantages of the sulfide precipitation process over traditional methods employing hydroxides. The aim of this work was thus to explore Technologies for the precipitation of valuable metals, such as nickel using such sulfides (as either Na2S or biogenic sulfide). The recovery of nickel sulfide was improved when the initial pH of the solution containing each metal was set to 7. In such a condition the removal efficiency of nickel was 99.9%, corresponding to a residual level of 0.13 mg /L for nickel in solution. Kinetic parameters for precipitation were determined from the particle size distributions (produced in an MSMPR reactor) using the method of moments, where the growth and nucleation rates, as well the agglomeration kernel, were calculated. The precipitation of nickel at an initial pH of 7 showed a nucleation rate value of 8.16 x 1018#m^-3 s^-1, the highest volumetric growth rate (1.03 x 10^1 um^-3 s^-1) and agglomeration kernel of 9.71 x 10^-23m3 #^-1 s^-1. The biogenic sulfide was a suitable alternative to sodium sulfide for nickel removal. Both sodium sulfide and biogenic sulfide can be utilized to precipitate nickel as millerite (NiS), allowing the effluent compliant with environmental legislation.
Applying virtual reality model to green ironmaking industry and education : ‘a case study of charcoal mini-blast furnace plant’.
(2017) Vieira, Cláudio Batista; Seshadri, Varadarajan; Oliveira, Ricardo Augusto Rabelo; Reinhardt, Pablo; Calazans, Patrícia Moreira Procópio; Vieira Filho, José Batista
A virtual reality (VR) model has been developed in the case of a generic green ironmaking industrial unit, namely a typical charcoal mini-blast furnace (CMBF) plant in Brazil. The VR prototype construction of the CMBF plant has been implemented through integration of data in different softwares and hardwares, including detailed engineering design of various auxiliary units and major equipments with realistic project parameters. Through the VR technology, one can actually have the unique experience visiting all parts of the CMBF plant, promote technical discussions on engineering and process control with users and improve information handling, communication, safety, maintenance procedures and development of advanced engineering projects in the field. VR industry-professional education platform can be used in universities, museums and industries with great benefits to students, workers and users.
Artificial neural network-based committee machine for predicting fuel rate and sulfur contents of a coke blast furnace.
(2019) Assis, Paulo Santos; Carvalho, Leonard de Araújo; Irgaliyev, A.
Being developed over the centuries, it currently occupies a prominent role in the world production scenario, being the stage of the process related to the obtaining of hot metal an element of great importance to establish the competitiveness of national steel. From this perspective, the control of the process of obtaining hot metal is relevant to ensure competitive prices and a sustainable process. Considering the presented situation, this research developed a committee machine, being three networks to predict each of the study variables, namely: i) fuel rate; ii) sulfur content in hot metal. The committee machine was developed to model the hot metal during the operation of a coke blast furnace, according to the input parameters provided. The results obtained by the committee machine were lower than those of the neural networks acting alone, and the following RMSE values were verified: i) fuel rate: 4.88 (network 1), 4.74 (network 2), 6.14 (network 3) and 4.67 (committee); ii) sulfur content: 0.00915 (network 1), 0.00917 (network 2), 0.00974 (network 3) and 0.00726 (committee). Considering the results obtained, the model can be used to provide important support in monitoring and decision making during the operation.
Artificial neural networks to prediction fuel rate in the blast furnace operation.
(2018) Carvalho, Leonard de Araújo; Assis, Paulo Santos
This paper proposes the use of artificial neural networks for the prediction of fuel consumption in the blast furnace. For this purpose, a dataset of 270 records, with 19 input variables were considered, based on the historical data of operation from the years 2014 to 2017 of a blast furnace of a Brazilian steel mill, and it was verified that model presented good results with correlation coefficient of 0.837, consisting of an input layer with 19 neurons, intermediate layer with 19 neurons and output layer with 1 neuron.
Aspectos técnicos da utilização da carepa gerada em processos siderúrgicos e tratada por desagregação ultra-sônica.
(2006) Cunha, Adriano Ferreira da; Araújo Filho, Gerson de; Martins Júnior, Álvaro; Gomes, Olídio Carlos Blanc; Assis, Paulo Santos
A siderurgia brasileira tem uma geração média de resíduos de 700kg por tonelada de aço produzido. A recuperação dos teores metálicos contidos nesses resíduos passou a ser muito importante tanto quanto aos limites impostos pelas legislações ambientais, como do ponto de vista econômico, visto que substituem matérias-primas empregadas no processo. Carepa é um produto oriundo da oxidação da superfície do aço quando submetido ao gradiente térmico ou simples ação do tempo. Uma planta piloto foi instalada na ETE-III da VMB, onde foi gerada a carepa limpa para os testes na própria empresa. A técnica por DUS mostrou que este material é de fácil processamento e que eleva o seu valor agregado, substituindo com eficácia a utilização da carepa nas operações de refino.
Assessing metal recovery from low-grade copper ores containing fluoride.
(2011) Sicupira, Lazaro Chaves; Veloso, Tácia Costa; Gonzaga, Flávia Donária Reis; Leão, Versiane Albis
Low-grade ores are becoming increasingly important to metal production due to increasing metal prices and depletion of high-grade, low-impurity sources. Bioleaching can be an option to recover the metallic content present in these tailings. In this work, the bioleaching potential of a low-grade copper ore, containing chalcocite, bornite and chalcopyrite, was demonstrated with a Sulfobacillus thermosulfidooxidans strain, at 50 °C. Batch experiments were performed in shake flasks as well as a bioreactor (BioFlo 110), and the effects of pH, metal concentration and air flow rate on copper extraction were determined. The presence of fluoride in the gangue minerals resulted in up to 270 mg/L total fluoride in solution, which affected bioleaching. Fluoride toxicity was overcome with aluminium additions and resulted in high copper extraction (up to 100%) at pH 1.9. Speciation calculations were performed with on the aluminium-fluoride systems and indicated AlF2+ as the main complex in the system, whereas HF concentration was reduced to values below 10−4 mol/L, which seems to be the threshold for bacterial growth inhibition.
Aumento da eficiência de dessulfuração do gusa líquido em um reator Kanbara.
(2011) Lemos, Leandro Rocha; Silva, Carlos Antônio da; Silva, Itavahn Alves da; Mansur, Filipe; Seshadri, Varadarajan; Kirmse, Odair José
São analisados os efeitos de parâmetros operacionais sobre o desempenho de dessulfuração do gusa líquido num reator Kanbara à luz de modelagens matemática e física do processo, no qual são considerados o tamanho das partículas do reagente dessulfurante no banho, forma, profundidade de imersão, posicionamento e velocidade de rotação do agitador mecânico. As condições de dispersão do reagente são estudadas via modelagem física, e a necessidade de se incorporar a distribuição espacial no modelo é discutida. Abordam-se as implicações teóricas e práticas da descentralização do impelidor. Os resultados industriais mostram-se em concordância com os previstos por um modelo matemático que despreza as complexidades de maior ordem e permitem evidenciar a importância da velocidade de rotação e da granulometria do reagente.
Austenitizing temperature and cooling rate effects on the martensitic transformation in a microalloyed-steel.
(2020) Souza, Samuel da Silva de; Moreira, Paulo Sérgio; Faria, Geraldo Lúcio de
The effects of the austenitizing temperature and the cooling rate upon the kinetic of athermal martensitic transformation in a microalloyed steel were evaluated. Considering the studied steel, the knowledge about these effects on the martensitic transformation has a great relevance for naval manufacturers and steel researchers. In this study, computational simulation was performed aiming to evaluate the phase’s stability. Specimens were submitted to quenching simulations in a dilatometer, considering four different austenitizing temperatures and four cooling rates. The results shown that the austenite chemical composition was not significantly affected by the austenitizing temperatures. Both the austenitic grain size and the cooling rate affected the martensitic transformation kinetics. The larger the austenitic grain size, the higher the Ms. The austenitic grain growth promoted a decrease in the required chemical energy to compensate the free energy increase associated with the lattice strain and the creation of new interfaces, leading to a lower austenite undercooling. An extrinsic effect of the cooling rate on the Ms was observed. For lower cooling rates, the carbide precipitation modified que austenite chemical composition, changing its stability and increasing Ms. A predictability equation, correlating the MS with the austenite grain size and the steel cooling rate, was proposed.
Avaliação da eficácia da técnica de difração de raios-X para caracterizar fases presentes em dois ferros fundidos cinzentos perlíticos com diferentes adições de nióbio.
(2021) Reis, Bárbara Cristina Mendanha; Faria, Geraldo Lúcio de; Bortoluzzi, Mirian Batista de Oliveira; Pereira, Natália Fernanda Santos; Carmo, Denílson José do; Santos, Anderson Júnior dos; Câmara, Marcelo Araújo
This work aims to present a brief state of the art regarding the characterization techniques currently used to evaluate the effects of fabrication processes on the structure of gray cast iron, as well as to evaluate the effectiveness of the X-ray diffraction technique (XRD) to identify and quantify the phases present in two types of gray cast iron: one with low (0.02% by weight) and the other with high niobium content (0.21-0.24% by weight). For both samples, the three main phases were identified: graphite-G, ferrite-Fe(α) and cementite-Fe3C. However, not even for the sample with the highest niobium content, niobium carbide (NbC) was identified by this technique, a fact justified by the detection limit of the conventional diffractometer used and the small fraction of this carbide in the analyzed samples. The modification in the niobium concentration was not enough to promote significant differences in the diffractograms. The fluorescence of iron excited mainly by Cu Kα radiation resulted in a high level of noise in the measurements and made it impossible to quantify the phases by means of Rietveld refinement. Thus, for the analyzed niobium contents and limitations of the instrumental conditions used in this work to minimize these iron fluorescence effects in the samples (but usual operating conditions of copper tube equipment in routine operation), it is concluded that the Cu tube XRD technique is not effective for quantifying phase fractions nor for identifying NbC in gray cast iron.
Avaliação da formulação de reativos à base de ácido pícrico visando a revelação do grão austenítico prévio em diferentes tipos de aços.
(2021) Pimenta, Natália Aparecida Barbosa; Moreira, Paulo Sérgio; Faria, Geraldo Lúcio de
As técnicas de revelação dos contornos de grãos austeníticos prévios em aços são importantes ferramentas de caracterização. O método mais usual faz uso de reativos à base de ácido pícrico, que, na maioria dos casos, não produz resultados satisfatórios. Diante disso, foram investigadas, neste trabalho, formulações de reativos à base de ácido pícrico, variando-se a concentração de ácido clorídrico, com o objetivo de propor condições de ataque eficientes para sete aços fabricados no Brasil. Para cada aço, foram avaliados reativos com cinco concentrações distintas de HCl e diferentes tempos de ataque. Foi possível revelar os contornos de grãos austeníticos eficientemente para todos os tipos de aços estudados adequando-se a concentração de HCl adicionado e o tempo de ataque. Com base nos resultados alcançados, foi possível disponibilizar uma tabela e uma equação de regressão linear múltipla que apresenta o tempo de ataque em função do carbono equivalente do aço e da concentração de HCl. Concluiu-se que a concentração de HCL utilizada no reativo é o parâmetro que exerce maior influência sobre o tempo de ataque.
Avaliação da influência de tratamentos térmicos pós-soldagem sobre a microestrutura e propriedades mecânicas de juntas de um aço API 5L X70Q.
(2015) Araújo, Lívia Carla Silva de; Cândido, Luiz Cláudio; Trindade, Vicente Braz; Porcaro, Rodrigo Rangel
Aços que atendem à norma API 5L são aplicados na construção de dutos e há grande interesse naqueles de maior resistência, como o grau API 5L X70Q. Ainda são escassos os estudos relacionados a tubos sem costura. Durante a montagem, os tubos podem ser soldados por eletrodos revestidos (SMAW) e eventualmente sofrer aquecimento indutivo para adequação à topografia do terreno, processos que podem alterar a microestrutura das juntas. Neste trabalho foram obtidas juntas soldadas pelo processo SMAW, a partir de tubo sem costura grau API 5L X70Q. As juntas foram submetidas a tratamentos térmicos pós-soldagem nas temperaturas 920 °C e 600 °C. Foram realizados ensaios de tração, impacto Charpy e microdureza, além de caracterização metalográfica nas amostras de metal base e nas juntas como soldadas e após os tratamentos térmicos. O tratamento térmico a 920 °C promoveu a formação de estrutura ferrita/perlita, com consequente redução na resistência mecânica das juntas a valores inferiores aos especificados para o grau X70Q. Porém, o tratamento térmico a 600 °C mostrou-se benéfico devido à redução da fração volumétrica dos constituintes martensita/austenita e martensita-austenita-bainita, sem reduzir de forma significativa a resistência mecânica e com relativo ganho na tenacidade ao impacto na ZTA e na ZF.

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