[pt] Um dos maiores problemas encontrados na indústria mineral é a perda de material ultrafino em processos convencionais de separação. A operação de floculação seletiva vem sendo estudada para a recuperação destes materiais. Por outro lado, o uso de biossurfactantes no processamento mineral, extraídos de microrganismos, vem apresentando bons resultados para a recuperação deste tipo de material, além de serem biodegradáveis e possuírem baixa toxicidade. Nesta pesquisa, tem-se como objetivo o estudo da floculação seletiva de partículas ultrafinas de hematita contidas em rejeito de minério de ferro usando o biossurfactante extraído da levedura Cândida stellata. Foi realizado um estudo de caracterização envolvendo análise granulométrica, análise química e difração raio-X (DRX). Para avaliar a interação do biossurfactante na superfície dos minerais de hematita e quartzo, foram desenvolvidos estudos de espectroscopia de infravermelho com transformada de Fourier (FTIR), potencial Zeta, microscopia eletrônica de varredura (MEV) e tensão superficial. Para os testes de floculação, realizados por jar test – teste de proveta, avaliou-se a influência do pH, concentração de sólidos e concentração de biossurfactante. A energia de interação foi avaliada através das teorias DLVO e DLVO Estendida (X-DLVO). As análises de espectroscopia no infravermelho (FTIR) e potencial zeta indicaram uma forte adsorção do biossurfactante na superfície da hematita, sendo que o ponto isoelétrico da hematita foi alterado de 5,35 para 3,25. No estudo de tensão superficial do biossurfactante indicou uma concentração micelar crítica (CMC) de 150 mg/L em pH 3, alcançando um valor próximo de 30 mN/m. Durante os ensaios de floculação foi alcançada uma recuperação de 99 por cento de hematita em pH 3, usando 75 mg/L de biossurfactante e uma concentração de sólidos de 0,50 por cento (1,25 g/500 mL). Pelo estudo da energia de interação entre as partículas, devido ao sinal negativo das interações de ácido-base de Lewis, as partículas de hematita flocularam após o contato com o biossurfactante, indicando que houve uma forte interação hidrofóbica entre elas. Os resultados obtidos neste trabalho indicam que o biossurfactante extraído da levedura Cândida stellata possui uma boa seletividade para a aglomeração das partículas ultrafinas de hematita. / [en] One of the biggest problems encountered in the mineral industry is the loss of ultrafine material in conventional separation processes. The selective flocculation operation has been studied to recover these materials. On the other hand, the use of biosurfactants in mineral processing, extracted from microorganisms, has been showing good results for the recovery of this type of material, in addition to being biodegradable and having low toxicity. In this research, the objective is to study the selective flocculation of ultrafine hematite particles contained in iron ore tailings using the biosurfactant extracted from the yeast Candida stellata. A characterization study was carried out involving particle size analysis, chemical analysis and X-ray diffraction (XRD). In order to evaluate the interaction of the biosurfactant on the surface of hematite and quartz minerals, studies of Fourier transform infrared spectroscopy (FTIR), Zeta potential, scanning electron microscopy (SEM) and surface tension were developed. For the flocculation tests, performed by jar test, the influence of pH, solids concentration and biosurfactant concentration was evaluated. The interaction energy was evaluated using the DLVO and DLVO Extended (X-DLVO) theories. The infrared spectroscopy (FTIR) and zeta potential analyzes indicated a strong adsorption of the biosurfactant on the hematite surface, with the hematite isoelectric point being changed from 5,35 to 3,25. In the surface tension study of the biosurfactant, it indicated a critical micellar concentration (CMC) of 150 mg/L at pH 3, reaching a value close to 30 mN/m. During the flocculation tests, a recovery of 99 percent of hematite at pH 3 was achieved, using 75 mg/L of biosurfactant and a solids concentration of 0,50 percent (1,25 g). By studying the interaction energy between the particles, due to the negative sign of the Lewis acid-base interactions, the hematite particles flocculated after contact with the biosurfactant, indicating that there was a strong hydrophobic interaction between them. The results obtained in this work indicate that the biosurfactant extracted from the yeast Candida stellata has a good selectivity for the agglomeration of ultrafine hematite particles.

Image segmentation through neural networks and deep learning have, in the recent decade, become a successful tool for automated decision-making. For Luossavaara-Kiirunavaara Aktiebolag (LKAB), this means identifying the amount of slag inside a furnace through computer vision.  There are many prominent convolutional neural network architectures in the literature, and this thesis explores two: a modified U-Net and the PSPNet. The architectures were combined with three loss functions and three class weighting schemes resulting in 18 model configurations that were evaluated and compared. This thesis also explores transfer learning techniques for neural networks tasked with identifying slag in images from inside a furnace. The benefit of transfer learning is that the network can learn to find features from already labeled data of another context. Finally, the thesis explored how temporal information could be utilised by adding an LSTM layer to a model taking pairs of images as input, instead of one. The results show (1) that the PSPNet outperformed the U-Net for all tested configurations in all relevant metrics, (2) that the model is able to find more complex features while converging quicker by using transfer learning, and (3) that utilising temporal information reduced the variance of the predictions, and that the modified PSPNet using an LSTM layer showed promise in handling images with outlying characteristics.

We are facing an important challenge, to reduce the greenhouse gas emissions to make sure that we limit global warming to 2 °C, preferably 1.5 °C. Drastic changes and developing new methods may be our only chance to keep global warming under 1.5 °C. The steel production in Sweden today accounts for 10% of the CO2 emission. The joint venture HYBRIT (Hydrogen Breakthrough Ironmaking Technology), between SSAB, LKAB and Vattenfall, aims to reduce the CO2 emission by developing a method that reduces iron ore pellets with hydrogen gas, leaving only water as off-gas. From simple thermodynamic calculations, it is evident that the reduction of iron ore using hydrogen gas is an endothermic reaction, requiring heat. Based on the calculated energy requirement, the temperature at the center of the pellet should not be the same as the temperature at the surface of the pellet but instead, decrease as the reduction reaction takes place. This report presents the temperature profile at the surface and in the center of a hematite pellet during hydrogen reduction at temperatures of 600 °C, 700 °C, 800 °C and 900 °C. Ideally, the results can be implemented in a model to better simulate the reduction reaction taking place inside a hematite pellet. The experiment consists of three sub-experiments, the first measures the temperature profile of the unreduced iron ore pellet in an argon gas atmosphere, secondly, the temperature profile and mass loss are measured during reduction, lastly, the temperature profile is measured for the reduced pellet in a hydrogen atmosphere. The mass loss measured during hydrogen reduction is used to calculate the degree of reduction. The results show that the reaction rate increases with increasing temperature and concentration of H2. Additionally, a higher reduction temperature gives the largest temperature decrease inside the pellet during reduction. At 900 °C, the temperature decrease is equal to 39 °C and at 600 °C, it is equal to 3 °C. The results prove that after a certain initial stage, gas diffusion and heat conduction through the product layers play important roles in controlling the reaction rate. There is even a period where a plateau of the reduction is observed, the reaction is mostly controlled by heat transfer. / Idag står vi inför en viktig utmaning, att minska utsläppen av växthusgaser och se till så att vi inte överskrider 2 °C uppvärmning, helst inte 1.5 °C. För att klara detta krävs drastiska förändringar och utvecklingar av nya metoder kan vara vår enda chans att uppnå 1.5-gradersmålet. Ståltillverkningen i Sverige idag står för 10% av CO2 utsläppen och för att bidra till att minska utsläppen av CO2 har företaget HYBRIT, vilket står för Hydrogen Brakethrough Ironmaking Technology, skapats. HYBRIT är en joint venture mellan SSAB, LKAB och Vattenfall som tillsammans vill skapa stål på ett mer miljövänligt sätt. Processen går ut på att reducera järnmalmspellets med hjälp av vätgas för att producera järnsvamp och ge ifrån sig vatten som avgas. Från enkla termodynamiska beräkningar är det lätt att inse att reduktionen med hjälp av vätgas är en endoterm process, som kräver energi. Det är genom denna kunskap som en kan föreställa sig att reduktionen av järnmalmspellets med hjälp av vätgas kommer bidra till en temperaturminskning. I denna rapport har temperaturprofilen inne i och på ytan av en hematitpellet mätts under tiden som den blivit reducerad med vätgas. Idealt kan resultaten implementeras i en modell för att bättre simulera reduktionsreaktionen som äger rum i en hematitpellets. Fyra olika reduktionstemperaturer har undersökts: 600 °C, 700 °C, 800 °C och 900 °C. Experimenten består av tre del-experiment, först mäts temperaturprofilen av den oreducerad hematitpelletsen i en argonatmosfär, sedan mäts viktminskningen och temperaturprofilen av pelleten medan den reduceras i en vätgasatmosfär, slutligen mäts temperaturprofilen av den reducerade pelleten i en argonatmosfär. Viktminskningen under reduktionen används för att beräkna reduktionsgraden under reduktionsförloppet. Resultaten visade att reduktionshastigheten ökade med ökande temperatur och koncentration av H2. Ökad temperatur gav även den största temperaturminskningen inne i pelleten då den reducerats med vätgas. Vid 900 °C uppmätes en temperaturminskning på 39 °C, varav reduktion vid 600 °C gav en temperaturminskning på 3 °C. Resultaten visar att efter en viss tids reduktion, spelar gasdiffusionen och värmeledningen genom produktlagret en viktig roll och är det som begränsar reduktions-hastigheten. Fortsatt, då hematitpelleten reducerades uppstod en platå där temperaturen var konstant och reaktionen till största delen var begränsad av värmeledningen genom produktlagret.

No description available.

No abstract provided. / Thesis / Master of Engineering (MEngr) / Scope and contents: This thesis describes the behaviour of iron ore-water suspensions under turbulent flow conditions. This work is divided into two parts. Part I deals with the regimes of transport under steady state flow conditions in circular and horizontal ducts. The heterogeneous flow regime is extensively analyzed; a sequential discrimination of models with an oriented design of experiments have permitted the determination of the best model to correlate hydraulic gradients for these suspensions. A critical discussion on the limit deposit conditions is also included. Part II describes the behaviour of clear water under oscillatory flow conditions. The study demonstrates that the quasi-steady state hypothesis, i.e., fully developed flow assumption, applied to pulsatile turbulent flow under the conditions studied. Observations on the behaviour of iron ore-water suspensions under pulsatile flow are also included. The experiments were carried out using a new air-pulsing technique.

Iron production accounts for substantial shares of global coal use and GHG emissions. LKAB is Europe’s largest iron company and Sweden’s fourth-largest emitter of GHGs. To reduce its emissions, LKAB might implement biomass in iron ore pelletisation. It is therefore important with information on how the biomass demand can be met and what the environmental implications may be, but available research focuses on contexts which are irrelevant for LKAB. This study aims to fill this knowledge gap by investigating the extent to which LKAB can replace coal with biomass in iron ore pelletisation by assessing the availability of biomass as well as its environmental and economic performance relative to coal.  The study includes slash, industrial residues, pellets, and willow. The biomass potential is assessed using statistics and calculations. The environmental performance is assessed based on an LCA combined with a qualitative sustainability assessment, covering land-use change (LUC), biodiversity, toxins, chemicals, eutrophication (toxic-chem-eut), and compliance with EU sustainability criteria. The economic performance is based on price statistics. In general, all assessed biomass sources can meet LKAB’s potential demand, but requires sourcing from different locations, at different prices, with different environmental impacts, and with different market effects. In northern Sweden (“Norrland”) slash is largely unused and has a very good potential to supply LKAB with biomass. Industrial residues have a good potential on the domestic level but lower potential regionally. The potential of domestically produced pellets is limited but the demand can be met by increased production or imports. Willow currently has a low potential, but there is good potential to increase domestic production. In general, the biomass fuels have substantially lower environmental impact than coal. The LCA indicates that slash and industrial residues have the lowest environmental impact, pellets has slightly higher, and willow has higher impact in most categories (also higher than coal in some categories, although lower in general). Slash, industrial residues, and pellets cause no impacts on LUC, biodiversity, and toxic-chem-eut. Industrial residues, pellets, and willow are compliant with EU sustainability criteria, but it is uncertain if slash complies due to a pending criteria revision. Willow has slightly positive impacts on biodiversity and toxic-chem-eut but slightly negative impacts on LUC. The cost for biomass relative to coal is uncertain due to price volatility. In 2020, coal had the lowest price, but its average price the past three years is twice the price for slash and industrial residues and on par with the price for pellets. If all fossil GHGs in iron production would be subjected to the EU emission trading scheme the economic competitiveness of biomass would increase. The study shows that increased use of biomass, both in LKAB and in general, can be achieved with reduced environmental impacts compared to coal. Future studies should map the effects of dynamic factors on environmental impact and costs, and quantify net environmental impacts, including spatial-specific changes. / <p>Betygsdatum 2023-07-07</p>

[pt] O presente trabalho tem como objetivo investigar a influência da substituição de frações de areia por rejeito de minério de ferro (RMF) no concreto. Estudaram-se a reatividade do rejeito com o cimento, as variações de porosidade, a trabalhabilidade e o efeito filler do material. Para isso uma série de ensaios químicos, físicos, mecânicos e térmicos foram conduzidos. O RMF foi caracterizado quanto à composição química, granulometria e massa específica. Constatou-se que o material é formado por sílica e hematita e possui massa específica muito próxima à da areia, embora seja uma ordem de grandeza mais fino. Para avaliar a reatividade do RMF confrontou-se os resultados de diversos experimentos. Foram realizados ensaios de compressão axial em pastas de cimento com substituição de 10 por cento, 20 por cento e 30 por cento de cimento por RMF, em diferentes idades. O RMF foi ensaiado quimicamente pelo método Chapelle modificado e o índice de atividade pozolânica foi determinado. Além disso, fragmentos de concreto com RMF, aos 28 e 90 dias, foram ensaiados por termogravimetria e os produtos de hidratação comparados à amostra de referência. O grau de cristalinidade do RMF foi determinado por difração de raios-X. Todas as evidências indicam que o material é inerte. O efeito do RMF na trabalhabilidade do concreto e da pasta de cimento foi avaliado por ensaio de abatimento (slump test) e espalhamento (flow table), respectivamente, e detectou-se um aumento da trabalhabilidade com o aumento da fração de RMF. A porosidade foi avaliada por ensaio de imersão em água no concreto com diferentes frações de RMF, e por ensaio de microtomografia computadorizada, na qual foi determinada a distribuição dos poros. De modo geral, detectou-se tendência de redução da porosidade com o acréscimo do RMF. A resistência mecânica do concreto foi avaliada para substituições de 10 por cento, 20 por cento e 30 por cento de areia por RMF e os resultados foram comparados à substituição das mesmas frações de areia por material inerte, na granulometria do RMF. O efeito filler causou um aumento da resistência, tendo o melhor resultado sido obtido com a fração de 20 por cento de RMF. Também foi avaliado o comportamento à flexão em prismas de concreto com adição de fibras de aço na fração de 30 kg/m cúbicos e 20 por cento de substituição de areia por RMF. Os resultados de cargas máximas, tensões residuais e tenacidade foram, em média, muito próximos nas amostras com RMF e de referência. / [en] The present work aims to investigate the influence of the replacement of sand fractions by iron ore tailings (IOT) on concrete. The reactivity of tailings in the presence of cement, the variation of porosity and workability, and the filler effect of the material were studied. For this purpose, a series of chemical, physical, mechanical and thermal tests were conducted. The IOT was characterized by its chemical composition, particle size and specific weight. It is found that the material is formed by silica and hematite and has a specific weight similar to that of sand, although its grains are ten times smaller. To evaluate the reactivity of the IOT, the results of several experiments were compared. Axial compression tests were performed on cement pastes with replacement of 10 percent, 20 percent and 30 percent cement by IOT at different ages. The IOT was chemically tested by the modified Chapelle test and the pozzolanic activity index was determined. In addition, IOT concrete fragments at 28 and 90 days were tested by thermogravimetry and the hydration products were compared to the reference sample. The degree of crystallinity of the IOT was determined by X-ray diffraction. All evidence indicates that the material is inert. The effect of IOT on the workability of concrete and cement paste was tested by slump test and flow table, respectively, and an increase in workability was detected by increasing the IOT fraction. Porosity was evaluated by the water immersion test on concretes with different IOT fractions, and by computed tomography, which determined the pore distribution. In general, a tendency to reduce porosity was observed as IOT fraction increased. The mechanical strength of the concrete was evaluated for 10 percent, 20 percent and 30 percent sand replacements by IOT and the results were compared to the replacement of the same sand fractions by inert material, in the IOT granulometry. The filler effect caused an increase in resistance, with the best result being the 20 percent IOT fraction. It was also evaluated the flexural behavior in prismatic concrete specimens with addition of steel fibers in the fraction of 30 kg/m cubic and 20 percent of sand substitution by IOT. The results of maximum loads, residual stresses and toughness were on average very similar in the IOT and reference samples.

The cut-off grade determines what rock mass are economic to mine. At the Dannemora mine, in eastern Bergslagen, Sweden, previously processed ore generated tailings (enrichment sand) with an iron content of 21-22 % that was backfilled into large open bodies (stopes) in the mine between 2013-2015. However, the tailings are now considered as ore reserves due to an upgraded processing plant that lowered the cut-off from 30 % Fe to 15 % Fe. Further, with the current lowered cut-off, Grängesberg Exploration Holding AB intends to restart production of iron ore in the Dannemora mine in new ore bodies. However, before starting full operation of excavating the ore bodies and extracting the large ore reserve of tailings, several challenges related to the rock stability need to be well assessed. The main goal of this project is therefore to investigate what would be the safest and most economical technique to extract the tailings that currently act as a stabilising rock mass against the side walls. Investigation of borehole data, drill cores, and geometric calculations, were conducted to characterise the stope host rocks in terms of risk for rock failure and leads to several statements. The results reveal that the host rock has a high strength (70-80 % RQD) and there is a low risk of spalling deformation at the extracted depths when the tailings will be removed. However, deformation as wedge failure could potentially occur when the stabilising tailings will be removed. Further, it is shown that the amount of tailings that can be extracted represent approximately more than one year of iron ore production in the mine. Analysis of the host rock shows that dilution of the tailings can be favourable if the caved wall rocks contain marble or skarn, with ore sections &gt; 15 % Fe. The workflow demonstrates that extraction of low diluted tailings should be done at sublevel 350 meters, before extraction of high diluted tailings at sublevel 442-446 meters. Backfilling must be done simultaneously in order to preserve the stability against the side walls as the tailings are removed. This project demonstrates that tailing extraction is possible, while maintaining the stability of the host rock. The workflow presented in this thesis could be used as an approach for similar mining operations aiming to extract backfilled material and once again process it. / En cut-off halt bestämmer vid vilken halt som en bergmassa innehållandes värdefulla metaller, blir ekonomiskt brytningsbar (malm). Vid Dannemoragruvan i östra Bergslagen, Sverige, har tidigare bearbetad malm bildat en icke värdefull restprodukt (anrikningssand), innehållandes en järnhalt om 21-22 %, som återfylldes i stora brytningsrum inuti gruvan mellan 2013-2015. Anrikningssanden har nu blivit ansett som malm igen då ett uppgraderat anrikningsverk sänkt cut-off halten från 30 % Fe, till 15 % Fe. Med den sänkta cut-off halten, undersöker Grängesberg Exploration Holding AB vidare hur en återstart av Dannemoragruvan, och utbrytning av ännu inte utbrutna malmkroppar, och uttag av den stora malmreserven av anrikningssanden, ska ske. Däremot måste flera utmaningar i form av bergstabilitet undersökas, innan uttaget av malmkropparna och den återfyllda anrikningssanden kan ske. Detta arbete siktar till att undersöka vilket tillvägagångsätt som skulle vara det säkraste och lönsammaste att extrahera anrikningssanden ifrån, då de agerar stabiliserande mot sidoväggarna i de stora brytningsrummen. Undersökning av borrhålsdata, borrkärnor, och geometriska beräkningar, utfördas för att karakterisera sidoberget till brytningsrummen för att förstå risken för bergdeformation. Resultaten visar på en stabil bergmassa (70-80 % RQD) med en liten risk för spjälkning (uppsprickning) vid de undersökta djupen. Risk för bergdeformation inträffar i stället som kilutfall när den stabiliserande anrikningssanden extraheras. Vidare beräknas det att ungefär mer än en årsproduktion av järnmalm kan extraheras i form av anrikningssand från de återfyllda brytningsrummen. Analys av sidoberget visar dessutom att utspädning av anrikningssanden genom blockutfall och uppsprickning, kan bli fördelaktigt om sidoberget innehåller marmor eller skarn med malmsektioner &gt; 15 % järn. Tillvägagångssättet för extrahering av anrikningssanden bör ske från djup 350 meter, innan den högre halten av utspädd anrikningssand extraheras från djup 442-446 meter. Återfyllning måste ske samtidigt för att bevara bergsstabiliteten mot sidoväggarna. Detta arbete visar att extrahering av anrikningssanden är möjligt, samtidigt som bergstabiliteten bevaras. Arbetsflödet skulle kunna användas som ett tillvägagångssätt för framtida gruvoperationer som söker att extrahera återfyllt material och åter anrika det.

In the iron production processes, sinters and pellets are mostly used as raw materials due to their consistency with respect to physical and chemical properties. However, natural iron ores, as mined, are rarely used directly as a feed material for iron processing. This is mainly due to the fact that they have small contents of iron and high concentration of impurities. Moreover, they swell and disintegrate during the descent in the furnace as well as due to low melting and softening temperatures. This work involves an investigation of the parameters that influence the use of natural iron ores as a direct feed material for iron production. Furthermore, it points out ways in which these can be mitigated so as to increase their direct use in iron production. Natural iron ore from Muko deposits in south-western Uganda was used in this study. Initially, characterisation of the physical and chemical properties was performed, to understand the natural composition of the ore. In addition, investigations were done to study the low temperature strength of the ore and its behaviour in the direct reduction zone. Also, simulations were performed with three models using the experimental data from the direct reduction experiments in order to determine the best model for predicting the direct reduction kinetics of natural iron ores. Chemical analyses showed that the Muko ore represents a high grade of hematite with an Fe content of 68% on average. The gangue content (SiO2+Al2O3) in 5 of the 6 investigated iron ore samples was &lt; 4%, which is within the tolerable limits for the dominant iron production processes. The S and P contents were 0001-0.006% and 0.02-0.05% respectively. These can be reduced in the furnace without presenting major processing difficulties. With respect to the mechanical properties, the Muko ore was found to have a Tumble Index value of 88-93 wt%, an Abrasion Index value of 0.5-3.8 wt% and a Shatter Index value of 0.6-2.0 wt%. Therefore, the ore holds its form during the handling and charging processes. Under low temperature investigations, new parameters were discovered that influence the low temperature strength of iron oxides. It was discovered that the positioning of the samples in the reduction furnace together with the original weight (W0) of the samples, have a big influence on the low temperature strength of iron oxide. Higher mechanical degradation (MD) values were obtained in the top furnace reaction zone samples (3-25% at 500oC and 10-21% at 600oC). These were the samples that had the first contact with the reducing gas, as it was flowing through the furnace from top to bottom. Then, the MD values decreased till 5-16% at a 500oC temperature and 6-20% at a 600oC temperature in the middle and bottom reaction zones samples. It was found that the obtained difference between the MD values in the top and other zones can be more than 2 times, particularly at 500oC temperature. Furthermore, the MD values for samples with W0 &lt; 5 g varied from 7-21% well as they decreased to 5-10% on average for samples with W0 ≥ 5 g. Moreover, the MD values for samples taken from the top reaction zone were larger than those from the middle and bottom zones. During direct reduction of the ores in a H2 and CO gas mixture with a ratio of 1.5 and a constant temperature, the reduction degree (RD) increased with a decreased flow rate until an optimum value was established. The RD also increased when the flow rate was kept constant and the temperature increased. An optimum range of 3-4g was found for natural iron ores, within which the highest RD values that are realised for all reduction conditions. In addition, the mechanical stability is greatly enhanced at RD values &gt; 0.7. In the case of microstructure, it was observed that the original microstructure of the samples had no significant impact on the final RD value (only 2-4%). However, it significantly influenced the reduction rate and time of the DR process. The thermo-gravimetric data obtained from the reduction experiments was used to calculate the solid conversion rate. Three models: the Grain Model (GM), the Volumetric Model (VM) and the Random Pore Model (RPM), were used to estimate the reduction kinetics of natural iron ores. The random pore model (RPM) provided the best agreement with the obtained experimental results (r2 = 0.993-0.998). Furthermore, it gave a better prediction of the natural iron oxide conversion and thereby the reduction kinetics. The RPM model was used for the estimation of the effect of original microstructure and porosity of iron ore lumps on the parameters of the reduction process. / <p>QC 20130531</p> / Sustainable Technology Development in the Lake Victoria Region

A finalidade deste trabalho é estudar a redução carbotérmica de minério hematítico com misturas e pelotas autorredutoras em um forno rotativo experimental. Trabalhou-se com duas temperaturas, a 1673 e 1773 K (1400 a 1500 °C), em fluxo de argônio de 1Nl/min, em um forno rotativo experimental aquecido por resistências, com uma rotação fixa de 5 rpm. Foram realizadas diversas experiências, alterando variáveis como a temperatura, composição e quantidade da escória, tipo de redutor, e tipo de conformação. Foi estudado o tempo de residência das pelotas e misturas autorredutoras dentro do forno e sua interrelação com a inclinação do mesmo. Mediu-se a resistência a compressão de diferentes composições de pelotas. Foi analisada a fração de redução atingida nas experiências com ajuda de um método indireto proposto neste trabalho, atingindo-se frações de redução acima de 98%. Especial atenção foi dada para os casos limites estudados, o primeiro com uma mistura autorredutora de 81% de minério hematítico de baixo teor, 19% de coque de petróleo,+10% cimento ARI, processada a 1773 K (1500 °C) com 33% de escória final, a qual, apesar da grande quantidade de escória, atingiu uma fração de redução de 98,7%; e o segundo, para uma mistura autorredutora de 43,5% de minério hematítico de baixo teor, 56,5% de pó de serragem, processada a 1773 K (1500 °C), a qual atingiu uma fração de redução de 99,2%, provando, com as ressalvas cabíveis, a factibilidade de reduzir diretamente com pó de serragem. Com base nas observações experimentais sugeriram-se modelos do processo de redução-fusão tanto das misturas como das pelotas autorredutoras no forno rotativo. Analisaram-se a composição da escória e a composição da fase metálica obtida. Para comparar o grau de coalescimento entre as amostras, foram levantadas as análises granulométricas de cada uma delas, comparando-se as porcentagens em massa dos nódulos de ferro-carbono com diâmetro superior a 7,93 mm. Atenção especial foi dada ao método de desagregação do produto; pela ausência de normas técnicas especificas para processos autorredutores, foi empregada uma adaptação do método de desagregação por tambor (ASTM E279-95), e validada por moagem manual. Estudou-se o efeito das variáveis: temperatura de processamento, temperatura liquidus da escória, da quantidade de escória de alta temperatura liquidus, da quantidade de voláteis do redutor, da quantidade do redutor, e da ausência de conformação. Entre os resultados destas experiências tem-se que a maior temperatura de processamento leva a maior grau de coalescimento. Na medida em que a escória do sistema não se liquefaz, o processo de coalescimento é prejudicado. Na medida em que a quantidade de escória com alta temperatura liquidus aumenta, o grau de coalescimento decresce. Ao se aumentar a quantidade do redutor acima do necessário para a correta redução, carburação e colaescimento, prejudica-se o processo de formação dos nódulos de ferro-carbono. Ao se comparar o grau de coalescimento obtido entre as misturas e as pelotas autorredutoras, temse que o desempenho das misturas autorredutoras é superior. Para aclarar o efeito da temperatura liquidus da escória no processo de carburação e coalescimento, foram realizadas experiências paralelas para estudar como a temperatura liquidus da escória e a ausência do FeO afetava o coalescimento. Ao estudar o transporte de carbono pelas escórias sem e com a presença de um óxido redutível, tem-se que o transporte do óxido de ferro na escória sem agitação é um fenômeno difusivo. / The purpose of this work is to study the carbothermal reduction of hematite ore as self-reducing mixtures or pellets in an experimental rotary kiln. Two different temperatures were employed, 1673 and 1773 K (1400-1500 ° C) in an experimental rotary kiln heated by resistors, with a fixed rotation of 5 rpm and under an argon flow of 1Nl/min. Several experiments were performed by changing variables such as temperature, composition and quantity of slag, type of carbonaceous material, and type of conformation. The residence time inside the furnace and its interrelation with the slope of the kiln containing self-reducing pellets or mixtures was studied. It was measured the compressive strength of pellets of different compositions. It has been analyzed the fractional reduction achieved in the experiments with the help of an indirect method proposed in this work, reaching fractional reduction above 98%. Special attention was given to some cases, the first one with a self-reducing mixture of 81% low grade ore, 19% petroleum coke, ARI +10%, processed to 1773 K (1500 ° C) with 33% final slag, which despite the large amount of slag reached a fractional reduction of 98.7%, and the second for a self-reducing mixture of 43.5% low-grade ore, 56.5% of sawdust processed to 1773 K (1500 ° C) which reached a fractional reduction of 99.2%, proving, with reasonable exceptions, the feasibility of reducing directly with sawdust. Based on experimental observations, process models of both the reduction-melting of self-reducing mixtures and pellets in the rotary kiln were proposed. The composition of slag and composition of the metallic phase obtained were analyzed. To compare the degree of coalescence between the samples, particle size analysis of each one was performed, comparing the percentages by weight of iron-carbon nuggets with a diameter greater than 7.93 mm. Regarding the method of disintegration of the product, due to the lack of technical standards for specific self-reducing processes, the drum method (ASTM E279-95) was adapted and validated by manual grinding. It was studied the effect of the following parameters: processing temperature, slag liquidus temperature, the amount of high liquidus temperature slag, amount of volatile matter of the reducing agent, the amount of reducing agent, and the absence of conformation. These experiments have shown that the higher the processing temperature, the greater the degree of coalescence, and also that as long as the slag does not melt, the coalescence process is impaired. As the amount of slag with high liquidus temperature increases, the degree of coalescence decreases. Increasing the amount of carbonaceous material above to that necessary to reduction and carburization undermines the process of formation of iron-carbon nuggets. When comparing the degree of coalescence obtained between the self-reducing mixtures and pellets, it has been shown that the performance of self-reducing mixtures is superior. To clarify the effect of the slag liquidus temperature in the carburization and coarsening process, experiments were conducted to study how the liquidus temperature of the slag and the absence of FeO affected the coarsening. By studying the transport of carbon in slags with and without the presence of a reducible oxide, it has been shown that the transport of iron oxide in the slag without agitation is a diffusive phenomenon.