O pó de aciaria elétrica é um importante subproduto da indústria siderúrgica devido ao seu alto teor de zinco. Assim, tecnologias vêm sendo desenvolvidas visando seu aproveitamento, sendo o forno Waelz a mais difundida delas atualmente. No entanto, sua operação, por contar com um forno rotativo de grandes dimensões que abriga uma infinidade de fenômenos físico-químicos, apresenta difícil previsibilidade ab initio. Por essa razão, este trabalho faz uso de uma ferramenta avançada da termodinâmica computacional, destinada à modelagem de processos, chamada SimuSage, a fim de modelar o seu comportamento. Para a criação do modelo utilizou-se também uma base de dados termodinâmicos advinda do software FactSage e a plataforma de desenvolvimento Lazarus. Com base em dados e resultados operacionais da literatura, foi possível realizar simulações nos modos adiabático e isotérmico, comparando os resultados com os da prática industrial. Constatou-se uma grande capacidade do modelo de reproduzir os resultados da literatura, mesmo quando não há muita informação para aferição dos parâmetros, gerando boa concordância com a composição química relatada dos produtos Óxido Waelz e Escória Waelz. / The electric arc furnace dust is an important by-product of the steel industry due to its high content of zinc. Thus, technologies have been developed aiming for its use, and the Waelz Kiln is the most widespread of them today. However, counting on a very large rotary kiln that houses an infinity of physico-chemical phenomena, its operation is difficult to predict ab initio. For this reason, in order to model its behaviour this work uses an advanced tool of computational thermodynamics designed to process modelling, called SimuSage. To create the model, a thermodynamic database, provided by the FactSage software, as well as a development platform, Lazarus IDE, were also used. Based on operational data and results from de literature, it was possible to perform simulations on both adiabatic and isothermal modes comparing its results with the industrial practice. A great capability of the model to reproduce results from the literature was found, even when there is not much information for the parameters calibration, generating good agreement regarding the reported chemical composition for the products, Waelz Oxide and Waelz Slag.

A presente tese teve como objetivo fornecer subsídios teóricos e experimentais com vistas à reciclagem da carepa gerada em usinas mini-mills através de briquetes autorredutores para uso em FEA. Para atingir os objetivos vislumbrados, o trabalho foi estruturado em quatro principais tópicos: estudo de caracterização e de redutibilidade da carepa, escolha e caracterização do redutor para uso nos briquetes, elaboração e caracterização da mistura e ensaios de laboratório para avaliação do desempenho dos briquetes autorredutores. Os estudos de caracterização da carepa indicaram que este resíduo é constituído principalmente de wustita e se apresenta estratificada em três camadas: camada externa fina e porosa composta de hematita e magnetita, camada intermediária de wustita densa e camada interna de wustita porosa. A cinética de redução da carepa foi investigada em termobalança no intervalo de temperatura entre 830 e 1200°C com CO puro e mistura 90%CO-10%CO2. A energia de ativação aparente encontrada nesses ensaios variou de 71 a 80 kJ/mol e as observações microscópicas demonstraram que a redução da carepa segue um modelo topoquímico. A escolha do agente redutor para compor o briquete se deu através de ensaios de gaseificação ao CO2 e de autorredução em termobalança com três tipos de material carbonoso. A partir desses ensaios observou-se a seguinte ordem decrescente de reatividade e respectivas energias aparentes de ativação: Carvão Vegetal (Ea = 237 kJ/mol), Carvão Mineral (Ea = 214 kJ/mol) e Coque de Petróleo (Ea = 335 kJ/mol). Em virtude da maior reatividade do Carvão Vegetal frente aos demais, este redutor foi escolhido para uso nos briquetes. A mistura utilizada na confecção dos briquetes autorredutores teve como constituintes principais a carepa, os finos de carvão vegetal e aglomerantes (melaço e cal). Ensaios de caracterização em termobalança com atmosfera oxidante e aquecimento rápido indicaram uma perda de massa de cerca de 40%, referente às etapas de secagem, desvolatilização e autorredução da mistura. Nesses ensaios, observou-se elevadas taxas de perda de massa da mistura e uma notável complexidade dos fenômenos envolvidos, com reações simultâneas de combustão, autorredução e de oxidação do ferro, prevalecendo uma ou outra, dependendo da temperatura e da fração reagida de amostra. Através de procedimentos que buscaram reduzir a complexidade dos fenômenos envolvidos nas condições oxidantes, foi possível estimar que a energia de ativação aparente de autorredução está entre 62 e 69 kJ/mol. Os briquetes produzidos em escala industrial foram submetidos a ensaios isotérmicos e não-isotérmicos de alta temperatura. Tais ensaios buscaram determinar os gradientes térmicos no interior do briquete, a energia de ativação aparente e o desempenho cinético do aglomerado em condições de temperatura que se aproximam da prática industrial. A partir das constatações concernentes às taxas das reações químicas individuais (redução e gaseificação), às medidas do perfil de temperatura no interior dos aglomerados, à energia de ativação estimada para o briquete (93 kJ/mol) e ao modelo de redução encontrado nos ensaios de alta temperatura, acredita-se que tanto a cinética de redução da carepa como a transferência de calor sejam obstáculos limitantes da cinética global dos briquetes em estudo. Finalmente, os resultados de metalização obtidos nos testes de alta temperatura dão indícios da possibilidade de uso destes briquetes em FEA. / This dissertation aimed to provide theoretical and experimental basis for recycling of mill scale generated in mini-mill plants through the use of self-reducing briquettes in EAF. To reach these goals, the work was structured around four main topics: characterization and reducibility study of scale, choice and characterization of the reductant to use in briquettes, elaboration and characterization of the mixture and laboratory tests to performance evaluation of self-reducing briquettes. The characterization studies of mill scale have indicated that this waste is composed mainly of wustite and is stratified into three layers with different morphologies: fine porous external layer composed of hematite and magnetite, intermediate layer of dense wustite and inner layer of porous wustite. The kinetics of scale reduction was investigated in thermobalance in a temperature range from 830 to 1200°C with pure CO and a mixture of 90% CO and 10% CO2. The apparent activation energy obtained in these tests ranged from 71 to 80 kJ/mol and the microscopic observations showed that the mill scale reduction corresponds to a topochemical model. The choice of the reductant for composing the briquette was made through tests of gasification with CO2 and of self-reduction in thermobalance with three different carbonaceous materials. From the results, it was observed the following decreasing reactivity order and the related apparent activation energy: Charcoal (Ea = 237 kJ/mol), Mineral Coal (Ea = 214 kJ/mol) and Petroleum Coke (Ea = 335 kJ/mol). Due to the higher reactivity of Charcoal in relation to the others, this reducer was chosen to be used in the briquettes. The main constituents of the mixture used in the manufacture of self-reducing briquettes were scale, charcoal and binders (melasse and lime). The characterization tests in thermobalance with oxidizing athmosfere and rapid heating indicated a mass loss of about 40%, referring to the stages of drying, devolatilization and self-reduction of the mixture. During these tests, it were observed high rates of mixture loss mass and a remarkable complexity of the phenomena, with simultaneous combustion, self-reduction and iron oxidation reactions, where their importance changes according to temperature and fractional reaction of the sample. Through the procedures that aimed to reduce the complexity of the related phenomena in oxidant conditions, it was possible to estimate that the self-reduction apparent activation energy ranges between 62 to 69 kJ/mol. The briquettes produced in the industrial plant were submitted to isothermal and nonisothermal tests of high temperatures. Such tests aimed to determine the thermal gradients into the briquette, the apparent activation energy and kinetic performance of the agglomerate in temperature conditions similar to the ones used in industrial practice. Based on the findings concerning the individual rates of chemical reactions (reduction and gasification), the measures of the temperature profile inside the briquettes, the activation energy estimated (93 kJ/mol) and the reduction model found in high-temperature tests, it is assumed that both the kinetics of mill scale reduction and heat transfer limit the overall kinetic rates of these briquettes. Finally, the results of metallization obtained in the tests conducted at high temperatures indicate the possibility of using these briquettes into the EAF.

Este trabalho tem por objetivo estudar o aproveitamento do pó de aciaria elétrica (PAE) na sinterização de minério de ferro visando a eliminação de zinco. Primeiramente, foi feita uma caracterização física e química do resíduo através de análises químicas, granulométricas, morfológicas e de difração de raios-X. O minério de ferro, principal componente do processo de sinterização, foi caracterizado através de análise química, granulométrica e de umidade. Em seguida, foram fabricadas micropelotas de 3,0 a 5,0mm de diâmetro compostas por 70% de PAE e 30% de moinha de coque, que foram classificadas por peneiramento e secas em esfufa. Depois de aglomerado, o resíduo foi incorporado na sinterização de minério de ferro em diferentes proporções, condições de processo e formas de adição (micropelotas, undersize da micropelotização com granulometria entre 1,0 e 2,0mm, ou mistura de PAE e coque em pó). A cada processo de sinterização foram retiradas amostras de sínter, os materiais foram analisados através de Microscópio Eletrônico de Varredura (MEV), macroscopia e análises químicas por espectrofotometria de absorção atômica para verificar o teor de zinco. Amostras de misturas não sinterizadas também foram submetidas a análises químicas para determinar a quantidade inicial de zinco, ou seja, verificar a quantidade de zinco contido na mistura antes do processo de sinterização. Mediante a comparação do teor de zinco das amostras não sinterizadas com os sínteres, foi possível determinar a eliminação de zinco nos ensaios realizados. Aproximadamente 92% de zinco foi eliminado (junto com os gases de saída) com a incorporação de 10% de micropelotas na mistura a sinterizar. Os resultados mostraram que a eliminação do metal no processo é proporcional à relação redutor/resíduo. / The aim of this work was to study the use of electric arc furnace dust (EAFD) in iron ore sintering process aiming zinc elimination. Firstly, physical and chemical characterizations of the waste were made using X-ray diffraction, microscopy, chemical and size analyses. Iron ore is the main component of the sintering process, this material was characterized by chemical, size and humidity analyses. After, micropellets composed of EAFD 70% and coke breeze 30% with diameters of 3.0-5.0 mm were produced, then they were dried in kiln and classified by sieving. The pellets were incorporated into the iron ore sintering charge using differents proportions, process conditions and addition forms (micropellets, undersize with diameters of 1.0-2.0 mm, or a mixture of EAFD and coke breeze). Sintered samples were collected in each sintering process. These materials were analyzed by scanning electron microscopy (SEM), macroscopy and chemical analysis using atomic absorption spectrophotometry in order to determine the zinc content. Samples of not sintered mixtures were also characterized by chemical analysis aiming the determination the initial amounts of zinc, i.e. in order to check the zinc amounts present in the mixture before the sintering process. The comparation between the zinc contents of sintered samples and not sintered allowed to determine the elimination of zinc during the experiments. About 92% of zinc was eliminated (along with the output gas) with the incorporation of 10% of micropellet in the sintering mixture. Results showed that the zinc elimination in the process is proportional to the ratio reducer/waste.

A redução no volume de resíduos produzidos, industriais e agrícolas, vem se tornando uma exigência constante em todos os processos de produção. A falta de espaço físico para a disposição destes resíduos, a contaminação ambiental causada por eles, além da necessidade de preservação dos recursos naturais não-renováveis e da diminuição do consumo de energia e emissão de poluentes, tornam a reciclagem e a reutilização dos resíduos uma alternativa bastante atraente. A construção civil apresenta-se como um setor bastante apto à utilização de técnicas de reaproveitamento de resíduos, provenientes das mais diversas indústrias. Além de todos os benefícios ambientais, este reaproveitamento, pela construção civil, pode gerar recursos financeiros, bem como, possibilita a melhora das características de alguns materiais de construção, e pode diminuir o custo de construção, fator importante, quando se avalia o déficit de habitacional existente no Brasil. Neste trabalho, desenvolveu-se um estudo baseado no aproveitamento de escória de aciaria elétrica, resíduo gerado a partir da reciclagem do aço, empregada como agregado para concreto de cimento Portland, em substituição total ou parcial dos materiais convencionais. Os resultados obtidos apontaram para a viabilidade de utilização deste resíduo como agregado. / The reduction on the volume of produced wastes, from industries or agriculture, is becoming a current demand in all production processes. The lack of space to dispose these wastes, the environment contamination caused by them, besides the necessity to preserve the non-renewable natural resources, to reduce energy consumption and greenhouse gas emission , are making wastes recycling and reutilization an interesting alternative. The civil construction presents itself as a field quite able to utilize techniques to reuse wastes from different industries. Besides all the environmental benefits, this reuse by the civil construction can create new profits, as well as, the improvement of the characteristics of some construction materials and it can also decrease the costs of the construction, which is a major factor, considering the Brazilian habitation deficit. In the present work a study was developed based on the reutilization of the electric arc furnace slag, a metallurgic waste from the steel recycling process, employed as an aggregate to the concrete of Portland cement, totally or partially replacing the conventional materials. The obtained results indicate this waste reutilization viability.

As atividades industriais geram uma série de resíduos, muitos dos quais passíveis de reciclagem. Na indústria siderúrgica, em operações de lingotamento e conformação mecânica, forma-se uma casca sólida quebradiça, conhecida como carepa, a qual é originada a partir da oxidação da superfície do aço quando submetido ao gradiente térmico. Constituída por óxidos de ferro, portanto, carrega o elemento essencial para fabricação do aço. Esse trabalho se utilizou de análises, ensaios laboratoriais e testes industriais para direcionar a reciclagem da carepa de uma usina siderúrgica no próprio forno elétrico a arco. Foram analisadas as propriedades físicas e químicas do material, e nos ensaios de redutibilidade em laboratório o comportamento da carepa foi observado frente à mistura com um agente redutor. Em escala industrial a carepa foi introduzida no forno elétrico a arco juntamente com a sucata de carregamento, e o comportamento das principais variáveis do processo foram avaliadas. Pelo entendimento da sua influência sobre o processo foi possível determinar a viabilidade de promover a reciclagem do resíduo no próprio processo siderúrgico. As carepas geradas na planta siderúrgica se distinguiram, essencialmente, quanto ao tamanho de partícula e teor de umidade. Quimicamente, as amostras são semelhantes, com teor de ferro mínimo de 70%. Na sua composição, predominaram óxidos de hematita, magnetita e wustita, sendo este último o de maior importância. Nos ensaios de autorredução em laboratório, foram constatados melhores resultados para fração reagida e grau de metalização quanto mais alta a temperatura de ensaio. Nos testes em escala industrial, a adição de 1% de carepa na carga comprovou que não houve influência sobre o consumo de energia elétrica e o teor de FeO da escória. A desfosforação do aço líquido foi positivamente afetada com percentual médio de fósforo reduzido em 15% com utilização de carepa. Por outro lado, o indicador de rendimento metálico sofreu impacto negativo, evidenciando a necessidade de avaliações complementares para determinar a reciclagem deste resíduo no forno elétrico a arco. / Industrial processes generate several residues and many of them are suitable for recycling. In the steel industry, casting operations and mechanical forming originate a solid brittle layer of oxide known as scale, which is produced by oxidation of the steel surface when exposed to a thermal gradient. Consisting of iron oxides, it therefore holds the essential element for steel manufacturing. This study performed analysis, laboratory trials and industrial tests to investigate scale recycling in an electric arc furnace. Chemical and physical properties of the material were analyzed and, at reducibility laboratory trials, the behavior of the scale was observed when mixed with a reducing agent. In industrial tests, the scale was introduced in an electric arc furnace mixed with the loaded scrap and the behavior of the main process variables was evaluated. By understanding its influence on the process, it was possible to determine the feasibility of scale recycling in steelmaking. The scales generated in the steel plant were distinguished mainly by the particle size and moisture content. Samples were chemically similar, with minimum 70% iron content. In its composition predominate hematite, magnetite and wustita oxides, the latter being the most important. In self-reduction laboratory tests, the best results for fraction reacted and metallization grade were reached with the highest temperatures. In industrial tests, with 1% scale added to the scrap, there was no influence in the electric energy consumption or FeO content of the slag. The liquid steel dephosphorization was positively affected since the average phosphorus percentage was reduced by 15% with the scale utilization. However, the yield indicator suffered negative impact, suggesting the need for further assessments to determine the scale recycling feasibility in electric arc furnace process.

Abstract In this thesis, different spectroscopic methods are used for studying metals. Electron spectroscopy is applied for the study of binding energy shifts between atomic vapor and solid metals. Photoionization and Auger decay of high temperature aluminum vapors are investigated. Ionization of atomic chromium metal vapor by light absorption is studied with synchrotron radiation and time-of-flight ion mass spectroscopy. Optical spectroscopy is used for studying light emission from electric arc furnace plasma in experimental apparatuses developed during this work. Experimental techniques and sample preparation methods are presented.

<p>Electric arc furnace (EAF) is a furnace that utilizes electric energy and chemical energy to melt scraps and produce liquid steel. During the industrial process of EAF, an electric arc will be generated around the electrode located at the center of the furnace, and this phenomenon will generate a lot of heat. If any part of the electric arc is exposed to the freeboard region, a region above the slag layer inside the furnace, the heat emitted by this exposed arc can significantly heat on side wall temperatures, resulting in an overheating issue of side wall. Water-cooling panels (WCP) have been used to cool down the side wall, but the concentrated overheating area, may damage the water-cooling panel. In this study, a combination of slag foaming phenomenon and electric arc has been considered. A calculator is developed based on several arc models to calculate the parameters about slag foaming and arc power. The parameters can be used as input in a computational fluid dynamics (CFD) model. The commercial software, ANSYS FLUENT^®, was utilized to give a prediction of the side wall temperature distribution of an EAF. Data from the plant has been used to validate the calculation results. Furthermore, a series of parametric studies has been investigated to study the influence of operating conditions. The developed model can help to predict the risk of overheating from given electrode conditions and slag compositions.</p>

Abstract In this thesis, different spectroscopic methods are used for studying metals. Electron spectroscopy is applied for the study of binding energy shifts between atomic vapor and solid metals. Photoionization and Auger decay of high temperature aluminum vapors are investigated. Ionization of atomic chromium metal vapor by light absorption is studied with synchrotron radiation and time-of-flight ion mass spectroscopy. Optical spectroscopy is used for studying light emission from electric arc furnace plasma in experimental apparatuses developed during this work. Experimental techniques and sample preparation methods are presented. / Original papers The original publications are not included in the electronic version of the dissertation. Huttula, M., Jänkälä, K., Mäkinen, A., Aksela, H., &amp; Aksela, S. (2008). Core shell electron spectroscopy on high temperature vapors: 2s photoionization and Auger decay of atomic aluminium. New Journal of Physics, 10(1), 13009. https://doi.org/10.1088/1367-2630/10/1/013009 Huttula, M., Partanen, L., Mäkinen, A., Kantia, T., Aksela, H., &amp; Aksela, S. (2009). KLL Auger decay in free aluminum atoms. Physical Review A, 79(2). https://doi.org/10.1103/physreva.79.023412 Aksela, S., Kantia, T., Patanen, M., Mäkinen, A., Urpelainen, S., &amp; Aksela, H. (2012). Accurate free atom–solid binding energy shifts for Au and Ag. Journal of Electron Spectroscopy and Related Phenomena, 185(8–9), 273–277. https://doi.org/10.1016/j.elspec.2012.05.007 Mäkinen, A., Patanen, M., Aksela, S., &amp; Aksela, H. (2012). Atom-solid 3p level binding energy shift of transition metals Cr, Mn, Fe, Co, and Ni. Journal of Electron Spectroscopy and Related Phenomena, 185(12), 573–577. https://doi.org/10.1016/j.elspec.2012.12.006 Mäkinen, A., Niskanen, J., &amp; Aksela, H. (2012). Relative photoionization cross section of Cr atoms in the valence region. Physical Review A, 85(5). https://doi.org/10.1103/physreva.85.053411 Mäkinen, A., Niskanen, J., Tikkala, H., &amp; Aksela, H. (2013). Optical emission from a small scale model electric arc furnace in 250–600 nm region. Review of Scientific Instruments, 84(4), 43111. https://doi.org/10.1063/1.4802833

A computerized Fast Fourier Transform system has been used to analyse vibration measurements sampled from a 100-ton electric arc furnace. It has been the hypothesis that patterns in the vibration data would correlate to specific events in the electric arc furnace during the melting process. The theory was that the vibration patterns would be most powerful in multiples of 50 Hz, as the electric arcs operate with a frequency of 50 Hz. It was concluded that the multiples of 50 Hz were dominant. Investigation was made regarding how the amount of scrap affects the amplitude in the vibrations after a defined amount of energy input. It was confirmed that the intensity of the vibrations decreased with increasing mass and basket volume. Another discovery was the M-shaped pattern at the beginning of the melting process. This pattern was statistically analysed. It was found that 71 % of the 41 charges showed an M-shaped correlation. The appearance of this M-shape was analysed regarding power usage, and steel-type. It was concluded that the steel type affected the appearance of the M-shape. The occurrence of flat-bath was also investigated. The theory was that the vibration data would be fairly constant with the occurrence of flat-bath. It was discovered that the vibration data experienced a somewhat constant behaviour towards the end of the melting process in approximately 57 % of the 41 charges. Difficulties were encountered regarding detection of patterns, and correlating them to specific conditions, due to the many parameters that affect the vibration measurements from charge to charge. It was concluded that vibration analysis are unlikely to be used as an absolute way to foresee every event in the electric arc furnace during each charge. But can rather serve as a statistical tool, upon which decisions of how the melting process should be conducted could be based on.

Abstract Carbon emissions pose a serious threat to the continued survival of this planet. All sectors of society must, therefore, lower their emissions, this includes the steel industry. The production of steel is based on iron ore reduction by carbon. In an attempt to relieve the steel industry from its inherent fossil dependence an initiative called HYBRIT has been started. It aims to supplant carbon reduction with hydrogen reduction. Currently, there is no economically viable industrial production of steel that uses fossil-free hydrogen as reduction agent. In order to create economic viability for such a process work has to be conducted to innovate and optimize. This study aims to be a part of that optimization process by creating a tool for optimizing the slag system with regards to phosphorus removal. 26843 slag compositions were evaluated using modules written in “Matlab” combined with “Thermo-Calc”. 1583 possible slag compositions were found to be suitable for phosphorus removal. These compositions were then optimized after slag weight in order to minimize slag associated cost. The compositions were tested against two theoretical raw materials with varying initial phosphorus content 250 ppm and 125 ppm. It was found that the initial phosphorus concentration of the raw material has a substantial impact not only on the slag costs but also the slag praxis that should be used.