The feasibility of producing Direct Reduced Iron from cold-bonded self-reducing composite pellets made from Anglo American Kumba Iron Ore Sishen upgraded slimes was considered on laboratory scale. Composite pellets were made by mixing Sishen upgraded slimes, coke and different binders using a pelletizing disc by addition of moisture. Binders investigated were dextrin, carboxymethylcellulose, calcium-lignosulphonate and combination of dextrin and bentonite. Dry strengths in excess of 300 N /pellet were attained by curing the pellets under ambient conditions. Dry strength of composite pellets increased with increase in binder quantity and decreased with increase in coke quantity. The composite pellets reduced within 20 minutes to degrees of metallisation in excess of 90 % at 1100 oC, with decrepitation indices significantly below 5 %. The degree of metallisation of composite pellets increased with an increase in reduction temperature (from 1000 to 1100 oC), reduction time (20 vs. 40 minutes) and coke quantity (15 vs. 20 wt. %). Carboxymethylcellulose was identified as the most economical and suitable binder for the Sishen upgraded slimes. / Dissertation (MSc)--University of Pretoria, 2015. / Anglo American Kumba Iron Ore and the National Research Foundation of South Africa (Grant number TP2009072800103) / Materials Science and Metallurgical Engineering / MSc / Unrestricted

Water models using perspex have been built to study the fluid flow and recirculation patterns developed in the sump of a steel continuous casting machine and the influences these have on the behaviour of inclusions. An experimental method has been devised to simulate the behaviour of inclusions in the sump and to study the apportionment of the input flux of inclusions between the molten mould powder layer and the strand. The method entails the uses of finely dispersed coloured paraffin oil in the inlet stream together with a floating colourless paraffin layer on the top of the water in the model mould to simulate the molten powder layer on top of the molten steel. A theoretical model has been formulated which relates the inclusion separation in the sump to the fluid flow there. The inclusion removal ratio in the sump for a given continuous casting machine can be predicted using this theoretical model. The model, using the properties of liquid steel and practicable casting speeds, demonstrates that the removal of inclusions of small size (< 40 um) from the mould sump is less than 5% efficient. Inclusion agglomeration plays an important role in inclusion removal. It has been shown that deep submersion of the SEN enhances the agglomeration of inclusion particle. Under certain conditions, for example, the average particle diameter in the meniscus region has been found to be as much as three times its value at the SEN nozzle. The use of fine alumina flakes or small air bubbles, together with a plane light source, has been found to be very successful in studying the fluid flow patterns developed in three-dimensional models. Employing this method, the fluid flow patterns developed on different planes within the model mould have been viewed and recorded photographically. The photographs so obtained have helped to explain the results obtained for the removal of inclusions. The fluid flow patterns developed when small outside diameter nozzles with deep SEN submerged depths are used have been found to be of benefit to the removal of inclusions. Increasing the SEN submerged depth promotes inclusion agglomeration and hence increases the inclusion removal ratio. Reducing the nozzle outside diameter and the casting speed increases the inclusion removal ratio in the sump. But the infleunces of these latter changes are not very strong, so that inclusion removal consideration need not influence the design strategies used for the casting speed and nozzle outside diameter. The SEN port angle has a little effect on the inclusion removal when using deep SEN submerged depth. Although argon stream introduced into the tundish nozzle stream can protect the nozzle blockage, it is not beneficial to the inclusion removal in the sump.

The goal of this thesis is to advance knowledge about the balance of forces acting on granular materials in the interior of the blast furnace and on the walls. Using the principles of fluid and granular flows, a mathematical model is developed and used to generate new knowledge about the influence of process parameters, under control of the blast furnace operator, on the granular stress at the level of the gas inlet and the walls. The mathematical model developed is validated under ambient conditions by comparing predictions with experimental data obtained from physical scale models of the blast furnace. Comparison of the wall gas pressure profile from a commercial blast furnace with results from the mathematical model developed, indicate that gas temperature is an important factor in estimating the magnitude of the external force exerted by gas flow on granular materials. Results also show that the vertical stress acting on the upper boundary of the coke bed in the hearth can be altered by changing variables which are under the operator’s control. These variables include the gas properties (mass flow rate and pressure) and the properties of the granular column (bulk density of granular materials and cohesive zone location). Information generated in this thesis can be used by blast furnace operators for guidance in controlling the vertical stress at the upper boundary of the coke bed in the hearth and for defining the force at this boundary for subsequent studies of hearth region. / Thesis / Doctor of Philosophy (PhD)

Para atender os altos níveis de produção exigidos dos Altos Fornos, a disponibilidade dos Canais de Corrida e dos Carros Torpedo torna-se um fator estratégico. Dentre as propostas de manutenção e reparo disponíveis pela indústria de refratários, a utilização de concretos refratários bombeáveis desponta como um recurso que possibilita, sinergicamente, realizar o reparo de forma localizada e em curtos tempos de parada. Utilizando esse tipo de material, existem, basicamente, dois tipos de aplicação: a realizada por \"Gunning\" e por \"Shotcrete\", cuja principal distinção para o usuário ocorre em função do teor de rebote, sendo os valores médios típicos de 15 % para o primeiro caso e de 5 % no segundo. Este estudo visou comparar o desempenho de concretos refratários para aplicação por bombeamento, destinados como revestimento refratários de Canais de Corrida e/ou de Carros Torpedo. As principais conclusões revelaram que dentre os concretos aplicados nos Canais de Corrida, o mais resistente à corrosão pelo ferro gusa liquido/escória é o concreto A-CLE por apresentar a fases espinélio (MgAl2O4) e não possuir SiO2 livre em sua matriz. Dentre os concretos indicados para aplicação em Carros Torpedo, o que teve melhor desempenho é o concreto C-CT seguido, em segundo lugar, pelo concreto B-T15 e, por fim, B-T85. Nesse caso a presença simultânea da fase SiC, de agentes redutores de molhabilidade (Cgraf), aditivos metálicos (Al0) , da ausência de aluminatos de cálcio, entre outros fatores, resultou em melhor desempenho. / The high productivity of blast furnaces and the availability of Torpedos Ladles and Blast Furnace Runners has a strategic factor for hot metal producers. Considering this, maximizing the refractories performance in a integrated siderurgic Plant must be achieved at a minimal cost. Among the available technologies for repairs and maintenance in the refractories Industry, the pumpable castables appear as a solution that allows, sinergically, do the repair and save valuable time. Basically there are two kinds of application : Gunning and Shotcrete technlogy. The main difference is the rebound index, around 15% for the first and 5% for the last one. This work compared the wear resistance performance of five pumpable refractory castables suggested by the suppliers for application in Blast Furnace Runners and/or Torpedo Ladle. The conclusions of this study revealed that amongst the available castables for the lining application, the A-CLE product is the most resistant against the molten hot metal/ slag bath at laboratorial Finger Test because , between other variables , it has the MgAl2O4 phase and is not free of SiO2 phase in the matrix. And regarding the castables indicated for Torpedo ladles application, C-CT product showed, comparatively a lower wear than the other ones (B-T15 and B-T85) since it has phases as SiC, C, and Alº in its composition.

Para atender os altos níveis de produção exigidos dos Altos Fornos, a disponibilidade dos Canais de Corrida e dos Carros Torpedo torna-se um fator estratégico. Dentre as propostas de manutenção e reparo disponíveis pela indústria de refratários, a utilização de concretos refratários bombeáveis desponta como um recurso que possibilita, sinergicamente, realizar o reparo de forma localizada e em curtos tempos de parada. Utilizando esse tipo de material, existem, basicamente, dois tipos de aplicação: a realizada por \"Gunning\" e por \"Shotcrete\", cuja principal distinção para o usuário ocorre em função do teor de rebote, sendo os valores médios típicos de 15 % para o primeiro caso e de 5 % no segundo. Este estudo visou comparar o desempenho de concretos refratários para aplicação por bombeamento, destinados como revestimento refratários de Canais de Corrida e/ou de Carros Torpedo. As principais conclusões revelaram que dentre os concretos aplicados nos Canais de Corrida, o mais resistente à corrosão pelo ferro gusa liquido/escória é o concreto A-CLE por apresentar a fases espinélio (MgAl2O4) e não possuir SiO2 livre em sua matriz. Dentre os concretos indicados para aplicação em Carros Torpedo, o que teve melhor desempenho é o concreto C-CT seguido, em segundo lugar, pelo concreto B-T15 e, por fim, B-T85. Nesse caso a presença simultânea da fase SiC, de agentes redutores de molhabilidade (Cgraf), aditivos metálicos (Al0) , da ausência de aluminatos de cálcio, entre outros fatores, resultou em melhor desempenho. / The high productivity of blast furnaces and the availability of Torpedos Ladles and Blast Furnace Runners has a strategic factor for hot metal producers. Considering this, maximizing the refractories performance in a integrated siderurgic Plant must be achieved at a minimal cost. Among the available technologies for repairs and maintenance in the refractories Industry, the pumpable castables appear as a solution that allows, sinergically, do the repair and save valuable time. Basically there are two kinds of application : Gunning and Shotcrete technlogy. The main difference is the rebound index, around 15% for the first and 5% for the last one. This work compared the wear resistance performance of five pumpable refractory castables suggested by the suppliers for application in Blast Furnace Runners and/or Torpedo Ladle. The conclusions of this study revealed that amongst the available castables for the lining application, the A-CLE product is the most resistant against the molten hot metal/ slag bath at laboratorial Finger Test because , between other variables , it has the MgAl2O4 phase and is not free of SiO2 phase in the matrix. And regarding the castables indicated for Torpedo ladles application, C-CT product showed, comparatively a lower wear than the other ones (B-T15 and B-T85) since it has phases as SiC, C, and Alº in its composition.

Coke is an indispensable material in Ironmaking process by blast furnace. To provide good and constant quality coke for stable and efficient blast furance operation is very important. Furthermore, a challenging issue in the cokemaking process is the prediction of coke quality. An accurate prediction can support production planning decision and reduce business operation costs. The objective of this thesis is to apply the backpropagation neural network and the model tree techniques for predicting the strength and meansize of coke. Specifically, we developed the coke- physical&chemical-property model, coal-usage model, coal-group-usage model, and extended model for the target prediction task. Experimentally, we found that the coal-usage model achieves the highest Correlation Coefficient and the lowest Mean Absolute Error. Moreover, the model trees technique reaches higher accuracy and better efficiency than does the backpropagation neural network technique.

<p>The thermodynamic conditions for the behaviour of silicon in the lower part of the blast furnace have been the focus of the thesis. More specifically, the influences of temperature, carbon activity, total gas pressure and Fe reoxidation on silicon have been studied.</p><p>Calculations show that an increased temperature gives higher equilibrium ratio between silicon in hot metal and slag. Furthermore, laboratory reduction studies shows that the carbon activity in the cohesive zone increase with an increased reduction time. Increased carbon activity will increase the equilibrium silicon content in liquid metal.</p><p>Equilibrium calculations based on tapped hot metal and slag shows that the equilibrium silicon content of the liquid metal phase is higher than measured at tapping. Around the raceway area the equilibrium silicon content is very high. The high equilibrium silicon content makes it important to differ between the conditions under operation and the conditions of samples taken out of the blast furnace before studied. The equilibrium silicon content is strongly correlated to the CO gas partial pressure. Often this partial pressure is changed during sampling and cooling of samples. At tapping the equilibrium partial pressure of CO has been calculated to higher values than the total gas pressure inside the blast furnace.</p><p>Metal droplets found in tapped slags are probably formed by reduction of FeO. In the periphery part of the lower part of the blast furnace, it is believed that mainly FeO oxidises silicon in hot metal. It is not expected that the metal droplets in the slag is formed if FeO oxidises dissolved silicon. Instead, the iron droplets may form at reactions with gas, coke carbon or coal powder carbon. Around some droplets increased magnesium content has been found. This may be due to reactions with gaseous magnesium that, according to thermodynamic conditions, is easy to form. It has been reported that much FeO may be formed in the raceway area. The metal droplets may indicate how much FeO that reacts with other components than liquid iron. The iron found in metal droplets in the slag corresponds to between 0.02 and 0.2 wt-% FeO in the slag.</p>

L’espace lorrain a connu, au cours des XIXe et XXe s., une intense activité sidérurgique reposant sur la réduction d’un minerai sédimentaire, la Minette lorraine. Paradoxalement, on a longtemps considéré qu’aucune activité de production liée à l’exploitation de ce minerai n’avait pris place dans cette région avant l’époque contemporaine. Un programme de recherche initié il y a 25 ans a par ailleurs totalement renouvelé la perception de l’histoire sidérurgique de cet espace. Les activités de production s’y sont déroulées de manière sporadique dès les âges du Fer, avant de prendre de l’ampleur au cours de la période médiévale. Les recherches menées permettent une première appréhension de l’évolution des modes de production du fer en Lorraine à différentes époques, mises en perspective dans leur contexte européen. Toutefois, les modalités de distribution du métal produit restent largement méconnues, du fait de l’indigence relative des sources historiques à cet égard. Une première perception des circuits de distribution du fer se développant au sein de l’espace lorrain est exposée dans ce mémoire, contribuant à l’appréhension des usages du fer à différentes époques.Une méthodologie développée récemment par le Laboratoire Métallurgies et Cultures et le Laboratoire Archéomatériaux et Prévision de l’Altération, reposant sur la caractérisation chimique des déchets associés à la réduction du minerai et des inclusions présentes dans les produits sidérurgiques, a été employée dans ce but. Ce travail interdisciplinaire propose par ailleurs de nouveaux développements en termes de traitement statistique multivarié de l’information chimique, contribuant ainsi à répondre aux problématiques développées.Un référentiel géochimique, constitué d’une base de données préexistante et d’informations nouvelles acquises à l’occasion de prospections archéologiques, offre une perception nouvelle de la diversité chimique caractérisant les activités sidérurgiques anciennes au sein de l’espace lorrain et de ses marges. Des ensembles géochimiques de production ont ainsi été mis en évidence. Plusieurs contextes de consommation ont ensuite été considérés, offrant un éclairage sur les circuits de distribution du fer aux époques anciennes en Lorraine. Une démarche statistique, reposant sur l’emploi d’analyses descriptives et de modèles prédictifs, a été appliquée en ce sens, après avoir été éprouvée par l’étude d’ateliers sidérurgiques pour lesquels l’utilisation d’un minerai en particulier est assurée par le contexte archéologique.Les résultats obtenus permettent de préciser, parfois à l’encontre des hypothèses formulées au préalable, les pratiques d’échange du fer à différentes époques, en regard de nos connaissances quant aux modes de production sidérurgiques. Des discussions portant sur le rôle joué par le travail du fer au sein des sociétés anciennes sont initiées à la lumière des informations nouvellement acquises. / Lorraine was, during the 19th and 20th c., one of the most important ironmaking areas worldwide, relying on the use of a sedimentary ore, the Minette lorraine. Paradoxically, it has long been thought that no iron was produced using this ore before the modern era. A research program initiated 25 years ago totally renewed our perception of its metallurgical history. Production activities were indeed sporadically performed since the Iron Age, before drastically increasing during medieval times. Research performed allows a first apprehension of the ironmaking activities’ forms in Lorraine and their evolution through successive periods, put into perspective in the European context. Iron trade and circulation remain however largely unknown, due to the lack of historical sources. A first insight of the trade networks relative to iron products extending throughout Lorraine and its fringes is exposed in this thesis, contributing to the perception of the use of iron in different periods.A methodology recently developed by the Laboratoire Métallurgies et Cultures and Laboratoire Archéomatériaux et Prévision de l’Altération, relying on the chemical characterization of smelting slags and slag inclusions entrapped in iron products, was employed to that purpose. This interdisciplinary work also offers new developments in the multivariate statistical treatment of chemical information, and contributes to answering the issues raised at the beginning of this work.A geochemical reference set, comprised of a pre-existing database and new information gathered on archaeological surveys performed during this work, was set up. It provides a new perception of the chemical diversity characterizing iron smelting activities within Lorraine and its fringes. Geochemical production sets were emphasized in doing so. Several iron consumption contexts were then considered, offering the possibility of shedding light on iron spreading networks during ancient times in Lorraine. A statistical approach, relying on the use of both descriptive statistical analyses and predictive modelling, was applied to that purpose. It was beforehand tested by studies performed on workshops for which the use of a given ore is attested by archaeological records.Results allow enlightening, sometimes against formerly formulated hypotheses, the practices in terms of the iron’s trade through different periods, facing our current knowledge about iron production modes. Benefiting from newly gathered information, discussions about the role played by ironworking activities among ancient societies are initiated.

This study was motivated by the excess oxygen that likely results from the current transition to hydrogen-based Swedish steel production. The potential usability of large amounts of oxygen in a process gas for iron ore pellet induration could improve the process efficiency in terms of fuel consumption and productivity. Iron ore pellets constitute the main raw material used in Scandinavian steel production. Knowledge of the effects of the process-gas oxygen level on induration is a prerequisite for establishing if, how, and to what extent oxygen enrichment can be exploited in an optimum manner to control temperature development and oxidation, while maintaining pellet quality. The objectives of this study are as follows: 1) to investigate the effects of the oxygen level in the inflow gas on pellet bed oxidation during induration, as well as the effects on the bed-scale temperature, oxidation degree, and cold compression strength (CCS) development; and 2) to identify the oxidation mechanisms corresponding to various oxygen levels and thermal histories. The current knowledge regarding the effects of high oxygen levels in the gas on oxidation is based on small-scale experiments; this study was conducted on a larger bed-scale and will thus contribute significantly to the knowledge pool of bed-scale effects resulting from different oxygen levels in the inflow process gas. An interrupted pot furnace experimental method was used, with the highest investigated oxygen level in the gas at 40% and an approximate bed-scale of 100 kg of pellets. The following conclusions were drawn from this study. First, efficient heating and a high degree of oxidation of an entire bed were rapidly achieved with the highest investigated oxygen level (40% O₂) compared to the results of the lower oxygen levels (6%, 13% and 30% O₂). The gas with 40% O₂ yielded improved pellet properties and a more uniform oxidation degree along the bed, compared to beds exposed to gas with lower O₂. Second, the temperature at the bottom of the bed increased more rapidly when exposed to a higher oxygen content in the gas compared to when only the gas temperature was increased. Third, the mechanical pellet properties (CCS and macrostructure) were improved in a bed exposed to gas with 40% O₂ compared to beds exposed to gas with lower oxygen levels. Finally, pellets from local conditions with comparable thermal histories oxidised according to similar mechanisms regardless of the oxygen level. Hence, it was demonstrated that the oxygen level influences the oxidation rate, whilst the temperature affects the oxidation mechanism. The overall trends in terms of the positive effect from the high oxygen content in the gas are promising, as they serve as a starting point for enabling faster production rates in the future. / <p>E632 and a digital meeting in Zoom or Teams. Maximum 8 people will be allowed in E632 due to the covid-19 pandemic situation.</p> / HYBRIT research program 1

The dust particles generated due to mechanical wear of iron ore pellets and clusters formed in molten stainless steel alloyed with rare earth metals (REM) are considered in this study. Firstly, the influence of the characteristics of iron ore pellets, applied load on a pellet bed and partial reduction of the pellets on the size distribution of the generated dust was investigated. Secondly, REM clusters are investigated to evaluate the size distribution of the clusters. Also, an extreme value distribution (EVD) analysis has been applied for the observed REM clusters. The large sized pellets showed 10-20% higher wear rate than small sized pellets during wear in a planetary mill. Moreover, an increase of ~67% was observed in the friction and dust generation in the pellet bed as the applied load increased from 1 to 3 kg. Also, it was observed that a higher friction in the pellet bed can lead to an increased amount of airborne particles. The mechanical wear experiments of pellets reduced at 500 °C (P500) and 850 °C (P850) showed that P500 pellets exhibit ~16-35% higher wear rate than unreduced pellets. For the P850 pellets, the wear is inhibited by formation of a metallic layer at the outer surface of the pellets. The mechanism of dust generation has been explained using the obtained results. A reliable cluster size distribution of REM clusters was obtained by improving the observation method and it was used to explicate the formation and growth mechanism of REM clusters. The results show that the growth of clusters is governed by different types of collisions depending on the size of the clusters. For EVD analysis three different size parameters were considered. Moreover, using the maximum length of clusters results in a better correlation of EVD regression lines compared to other size parameters. Moreover, a comparison of predicted and observed maximum lengths of clusters showed that further work is required for the application of EVD analyses for REM clusters. / Studien fokuserar på två olika typer av mikropartiklar som är valda från olika delar av järn- och ståltillverkningsprocessen. Dessa partiklar är dels stoft som genereras på grund av mekanisk nötning av partiklar och dels klusters som bildas i flytande rostfria stål legerade med sällsynta jordartsmetaller (REM). Inledningsvis så undersöktes inverkan av tre faktorer på storleksfördelningen hos stoft som bildas vid hantering av järnoxidpellets. De undersökta faktorerna inkluderade karakteristiken hos järnoxidpellets, det applicerade trycket på pelletsbädden och den partiella reduktionen av järnoxidpellets. Därefter så utfördes tredimensionella undersökningar av REM kluster som extraherats med hjälp av elektrolytisk extraction för att bestämma storleksfördelningen hos klustren. Dessutom så utfördes en extremvärdesdistribution (EVD) studie för de studerade klustren. En planetkvarn användes för att undersöka inverkan of karakeristiken hos pellets på stoftbildningen. Resultaten visade att storleken på pellets kan påverka nötningshastigheten under dessa försöksförhållanden. Pellets som hade en större storlek (13.5&lt; Deq &lt;15.0 mm) uppvisade en 10 till 20% högre nötningshastighet i jämförelse med mindre pellets (9.5&lt; Deq &lt;12.5 mm). Baserat på analyserna av stoftet som genererades under nötningsexperimenten så konstaterades att nötningsmekanismerna för dessa pellets var abrasions- och kollisionsnötning. En pelletsbädd skapades för att möjliggöra studier av inverkan av ett applicerat tryck på stoftbildningen och friktionskrafterna i en pelletsbädd. Ett varierat tryck på mellan 1 till 3 kg applicerades på pelletsbädden. Resultaten visade att en ökning på ~67% av friktionskraften och stoftbildningen ägde rum när det applicerade trycket ökades från 1 till 3kg. Dessutom så visade resultaten att en högre friktionskraft i pelletsbädden kan resultera in en ökad mängd luftburna partiklar. Den mekaniska nötningen av pellets som reducerats vid 500 °C (P500) och 850 °C (P850) studerades också genom användande av en planetkvarn. Resultaten visade att P500 pellets uppvisade en ~ 16 till 35% högre nötningshastighet i jämförelse med oreducerade referenspellets.  Resultaten för P850 pellets visade att den mekaniska nötningen motverkades genom bildningen av ett metalliskt skikt på den yttre delen av pelletsen. Resultaten visade också att stoftet som bildats pga mekanisk nötning av reducerade pellets innehöll 3 till 6 gånger mer grova partiklar  (&gt;20µm) i jämförelse med stoft som bildats från oreducerade pellets. Slutligen så diskuterades hur dessa resultat kan relateras till industriella förhållanden med avseende på mekanismerna som är involverade i den mekaniska nötningen av pellets samt med avseende på relationen mellan hastigheten av de utgående gaserna och storlken och morfologin hos stoftpartiklarna. Klusters innehållande REM-oxider som extraherats från en 253MA rostfri stålsort undersöktes med användande av en tredimensionell teknik. En trovärdig storleksfördelning av klusters (CSD) erhölls genom att förbättra undersökningsmetoden och denna användes för att studera bildningen och tillväxten av REM oxider. Dessutom så användes cirkularitetsfaktorn hos klusters för att dela in klustren i två olika grupper, vilka bildas och tillväxer enligt olika mekanismer. Resultaten visade också att tillväxten av klusters gynnas av olika typer av kollisioner som beror av av storleken på klusters. För REM-klusters så drogs slutsatsen att turbulenta kollisioner är den huvudsakliga mekanismen som påverkar tillväxten. Avhandlingen behandlar även problemet om hur det är möjligt att hantera synfält där det inte förekommer kluster vid en extremvärdesdistribution (EVD) analys. Tre olika parametrar undersöktes i EVD analysen. Resultaten visar att om den maximala längden på kluster (LC) används i analysen så erhålls den bästa korrelationen gällande regressionslinjen för en EVD analys. Specifikt så var R2 värdet upp till 0.9876 i jämförelse med de andra storleksparametrarna som har värden i intervallet 0.9656 – 0.9774. Slutligen så visar resultaten från en jämförelse mellan beräknade och observerade maximala klusterlängder att EVD analyser för studier av REM kluster behöver undersökas ytterligare i framtiden. / <p>QC 20161128</p>