Sandvik produces about 230 000 tonnes of steel annually by melting in an electric arc furnace, where more than 90% of this steel is casted via continuous casting. When the strands are cast, these strands will be cuts to specific lengths with 2 cm thick cuts by using gas and iron powder. This generates approximately 750 tonnes of steel chips (cutting residues) each year, with a composition from the entire annual production of steel that falls as a residual. The purpose of the work was to review a possible reuse of the cutting residues as a raw material in the electric arc furnace. The problem with the cutting residue is the large reactive surface area, which could cause the material to burn in the electric arc furnace during operation. Since there are a high gas flow in the electric arc furnace during operation, the cutting residue that has a small particle size can also disappear from the furnace with the gas flow to the particle filters. By briquetting the cutting residue, these problems could be minimized and a reuse of the cutting slag as raw material could thus be possible. Therefore the cutting residue was transported to a company that sieved, dried and briquetted the cutting residue.  37 tonnes of cutting residue briquettes have been reused into 18 charges under normal operations with 2 tonnes of cutting residue briquettes in each charge (one charge with only 1 tonne of cutting slag). In order to measure how efficient, the reuse of the cutting residue was, a reference was needed. The reference was based on how the yield of steel for the elements, molybdenum, nickel, copper, cobalt and chromium in the electric arc furnace behaves in daily operation. This yield was used as a basis for calculating the yield when reusing the cutting residue. The results showed that nickel and molybdenum had a consistently good yield. The results for the cobalt and copper was not as clear, but the yields were generally good. In the case of chromium the results are naturally varied, as chromium reacts with the slag during the process. However, the predominant conclusion of the work was that it is possible to reuse the cutting residue as a raw material in the electric arc furnace with an acceptable yield by briquetting it. Analysis of the slag was also done to see any deviations from daily operations. The results showed that the slag was not affected when the cutting residue was reused as raw material in the electric arc furnace. / Varje år producerar Sandvik ungefär 230 000 ton stål genom nedsmältning av stålskrot i ljusbågsugnen där mer än 90 % av stålet gjuts via stränggjutning. När strängarna gjuts kapas de till specifika längder med ett 2 cm tjockt snitt med hjälp av syrgas och järnpulver. Detta resulterar i en restprodukt (skärslagg) om ca 750 ton per år, med sammansättningen från den årliga produktionen av stål. Syftet med arbetet var att se över en möjlig återanvändning av skärslaggen som råvara i ljusbågsugnen. Problematiken med skärslaggen är den stora reaktiva ytan vilket kan medföra att materialet börjar brinna i ljusbågsugnen under drift. Skärslaggen har en liten partikelstorlek och kan således följa med till gas- och partikelfilter då det är ett högt gasflöde i ljusbågsugnen under drift. Genom att brikettera skärslaggen kan dessa problem minimeras och en återföring av skärslaggen som råvara kan således vara möjlig. Skärslaggen transporterades till ett företag som siktade, torkade och briketterade skärslaggen. 37 ton skärslaggsbriketter har återförts i 18 försökscharger under normal drift med 2 ton skärslaggsbriketter i varje charge (en charge med enbart 1 ton skärslagg). För att mäta hur effektivt återföringen av skärslaggen var behövdes en referensnivå. Referensnivån baserades på hur utbytet till stål för elementen, molybden, nickel, koppar, kobolt och krom i ljusbågsugnen förhåller sig vid daglig drift. Detta utbyte användes som bas för att beräkna utbytet vid återföringen av skärslaggen. Av resultaten framgår det att nickel och molybden visade genomgående goda utbyten. Utfallet för elementen kobolt och koppar var inte lika tydliga men utbytena var till övervägande del goda. Beträffande krom var resultaten av naturliga skäl varierande, då krom reagerar med slaggen under processens gång. Den övervägande slutsatsen av arbetet var emellertid att det går att återföra skärslagg som råvara i ljusbågsugnen med godtagbara utbyten genom att brikettera den. Analysering av ljusbågsugnsslaggen gjordes också för att se eventuella avvikelser ifrån den dagliga driften. Resultaten visade att slaggen inte påverkas när skärslaggen återförs som råvara i ljusbågsugnen.

No description available.

Primary aluminum production brings about severe environmental burden due to its energy intensive process.  Secondary aluminum production contributes to cutting off high energy demand around 90-95% and greenhouse gas emission by remelting scraps. However, previous research indicates melting furnace’s energy efficiency in secondary plant is still very low, which is around 26-29% and more than 70% heat is lost in different way. The objective of this project is to investigate energy consumption and greenhouse gas (GHG) emission in secondary aluminum cast house through process analysis. The result offers a comprehensive overview to aid decision-maker to compare energy consumption and environmental impacts caused by different product or process. This project has been done in collaboration with SAPA Heat Transfer. This project consists of two tasks. First task is aimed to give an overview of annual energy distribution and carbon footprint of per ton aluminum slab in SAPA cast house. In order to analyze energy distribution, mass and energy conservation has been applied for calculation. Meanwhile, International standard method, life cycle assessment, has been used to evaluate greenhouse gas contribution of the whole production process. The second task intends to investigate two effects (melting furnace type, raw material type) on products’ energy consumption and carbon footprint.  Melting furnace’s effect is compared by selecting electric induction furnace and oxy-fuel furnace. On the other hand, raw material’s effect is studied by comparison of four different cast house products which have different raw material recipe. Calculation and analysis results indicates that per ton Sapa cast house aluminum slab consumes energy 3826MJ and contributes to 306kgCO2eq. green house gas. Meanwhile, comparison results show that oxy-fuel melting furnace has higher energy efficiency than electric induction furnace, however, it contributes much more GHG due to consumption of propane fuel. In addition, primary ingot has been concluded as distinct carbon footprint contribution than others contributors (i.e. fuel) for Sapa cast house’s slab.

Iron and its products, especially the various forms of steel, have been and still are a vital material in many sectors of life. It is utilized in many industrial activities ranging from production of heavy duty mechanical equipment to light electrical appliances and home appliances. With the world‟s iron ore consumption estimated to stand at 1.3 billion tonnes by 2025, exploitation of any existing natural deposits is of increasing importance to meet the demands of the expanding world economy. Large deposits of iron ore exist in Uganda in the eastern (Tororo) regions and south-western (Kisoro-Kabale) regions of the country. The ore deposits of Kisoro-Kabale consist of an iron-rich hematite grade with less deleterious impurities as compared to that of Tororo. Prospective quantification puts the deposits at 30-50 million tonnes of raw-ore reserves. To date the deposits lay unexploited, with small holder black smith activities taking place in the area. This work involves understanding the occurrence, quantity and quality of the ore plus its properties and characteristics in a bid to pave way for its exploitation for economic use in Uganda and beyond. Characterisation was done on the samples collected from the deposits, to establish its physical, chemical and metallurgical properties. Literature detailing the natural occurrence of the deposits plus the genesis of the parent rocks and ore and the prospective tonnage is included. The economic situation in Uganda as far as demand and consumption of iron and steel is concerned is also briefly highlighted. The chemical, physical and metallurgical characteristics that could facilitate the initial exploitation of the ore are examined with conclusive results from the representative samples examined. The results present Muko ore as a high grade of hematite with an Fe content averaging 68%. The gangue content (SiO 2+Al2O3) of 5 of the 6 samples investigated is < 4%, which is within the tolerable limits for the dominant iron production processes, with its S and P contents being < 0.1% and 0.07% respectively. Thus, Muko iron ore can be reduced in the furnace without presenting major difficulties. With respect to mechanical properties, Muko ore was found to have a Tumble Index value > 85 wt%, an Abrasion Index value < 4 wt% and a Shatter Index value < 2.5 wt%. This implies that the ore holds its form during the processes of mining, transportation, screening and descent when loaded in the furnace for reduction. Its reducibility index was found to be 0.868%/min. This is well within the desired reduction limits for the major iron reduction processes. It implies that a high productivity (in terms of iron reduced) can be realised in the reduction processes in a given period of time. Muko iron ore was found to meet most of the feed raw material requirements (physical, chemical and metallurgical) for the blast furnace and the major direct reduction processes (Midrex, HYL III and SL/RN). Furthermore, for those desired for sinter and pellet making. It can thus serve well as a feed raw material for smelting reduction and direct reduction processes. / QC 20101007 / Sustainable Technological Development in the Lake Victoria Region

Hot isostatic pressing (HIP) is a thermal treatment method that is used to consolidate, densify or bondcomponents and materials. Argon gas is commonly used as the pressure medium and is isostaticallyapplied to the material with an excess pressure of 500-2000 bar and a temperature of 500-2200oC. WithHIP treatment being a well-established technology for the last decades, one is now striving to obtain anincreased understanding of local details in the internal gas flow and heat flux inside the HIP apparatus.The main objective of this work is to assess the potential of using computational fluid dynamics (CFD) asa reliable tool for future HIP development. Two simulations are being performed of which the first one isa steady-state analysis of a phase in the HIP-cycle called sustained state. The second simulation is atransient analysis, aiming to describe the cooling phase in the HIP-cycle. The most suitable modelingapproaches are determined through testing and evaluation of methods, models, discretization schemes andother solver parameters. To validate the sustained state simulation, the solution is compared tomeasurements of operating pressure, heat dissipation rate out through the HIP vessel and localtemperature by the vessel wall. However, no validation of the cooling simulations has been conducted. Asensitivity analysis was also performed, from which it could be established that a mesh refinement ofstrong temperature gradients resulted in an increase of wall heat dissipation rate by 1.8%. Both of thesimulation models have shown to yield satisfactory solutions that are consistent with the reality. With theachieved results, CFD has now been introduced into the HIP field and the presented modeling methodsmay serve as guidelines for future simulations.

This study focused on the dynamic behaviour of the freeze lining and slag bath, and the interactions between these components in an ilmenite-smelting furnace process. The purpose of the work was to gain a better understanding of these issues and to ultimately contribute to an improved understanding of the ilmenite-smelting process in its entirety, and to future improvements in the design, operation and control of these processes. A mathematical model of the freeze lining and furnace sidewall was developed. This model was used in isolation for focused characterisation of the dynamic behaviour and interactions of the freeze lining and slag bath. The influences of net power input and slag composition were studied and various aspects of the freeze lining and slag bath were considered. These aspects included freeze lining thickness, temperature distribution through the freeze lining and furnace sidewall, composition distribution through the freeze lining, slag bath temperature and slag bath composition. The thermal response of thermocouples installed in the furnace sidewall to changing conditions on the inside of the furnace was also investigated. A mathematical model of the crust that forms on the slag bath surface was developed. This model was not used in isolation, and was only incorporated into a complete model of the process. A mathematical model of the entire ilmenite-smelting furnace process was constructed. This model incorporated the two models mentioned above and was able to describe the metal bath, slag bath, furnace atmosphere, freeze lining, furnace sidewall and the crust that is sometimes present on top of the slag bath. The model was used to study the influence of changes in operational parameters on the slag bath and freeze lining. The operational parameters that were studied included electrical power and reductant feed rate, both relative to ilmenite feed rate. The influence of severe operational errors and furnace down time were also investigated. Operational errors included loss of all feed while maintain electrical power input, and loss of reductant feed while maintaining power input and ilmenite feed. The above-mentioned studies were conducted by executing numerous experiments with two of the mathematical models. The experimental results were processed into sets of graphs displaying variations in the aspects that were considered. Many valuable insights resulted from the interpretation of these results. One specific aspect that formed part of the scope of this work was the origin of the compositional invariance of the slag close to the stoichiometric M3O5composition. This invariance was studied and a mechanism was proposed that explains the observed behaviour. The proposed mechanism created some questions about other mechanisms in the process. These mechanisms were also considered and elaborated on. The models and results produced in this study provide valuable insights into the behaviour of the ilmenite-smelting process. It also represents a useful foundation for future modelling work, and finally, it presents numerous opportunities for organisations operating ilmenite-smelting furnaces to improve their understanding and even the performance of their processes. / Thesis (PhD (Metallurgical Engineering))--University of Pretoria, 2004. / Materials Science and Metallurgical Engineering / unrestricted

By 2050, Europe needs to have drastically decoupled its economic growth from its emissions of CO2. This is a direct response to the compelling evidence from the increasing risks of climate change brought about by the anthropogenic Greenhouse Gas (GHG) emissions and pollutant emissions (NOx). A replacement of significant percent of fossil fuels with renewable energy sources will be needed. However, energy production from most renewable energy sources, is typically intermittent and unpredictable. This requires a reliable mid-long term energy storage to synchronize production and demand. The Power-to-Fuel option or chemical storage can be the key for a sustainable energy system. Indeed, converting the excess of renewable energy into second generation fuels will unlock a long-term and high-density energy storage, ensuring also a reduction of the carbon footprint. These ”green” non-conventional fuels are blends of CH4, H2, CO and NH3. However, to achieve Power-to fuel, the development of an efficient combustion technology, coupled with virtually zero pollutant emissions, stable working conditions with different load and fuel and significant energy saving is required. In the last years, a so-called MILD or flameless combustion has drawn attention for its ability of meeting the mentioned targets. However, the studies available in literature are conducted on Jet in hot co-flow-like systems or they face conventional fuels, such as natural gas or methane. The examples using non-conventional fuels are scarce and limited to few operating conditions. In this framework, this PhD thesis focuses on a threefold aspect. Experimental campaigns investigated fuel flexibility of flameless combustion in the ULB furnace. A progressive addition of hydrogen in methane enhanced combustion features, reducing the ignition delay time and increasing the reactivity of the system, possibly losing its flameless behavior. Indeed, a threshold of 25% H2 was defined for reaching flameless/MILD conditions, characterized by still low pollutant emissions and temperature peak. This is in line with the goal of introducing “green” hydrogen into the natural gas pipeline (up to 20%) to reduce CO2 emissions. Further experimental campaigns tested the role of the injection geometry (varying the air injector ID) and fuel lance length to reduce NO emissions and retrieve flameless/MILD conditions for high hydrogen content. Finally, ammonia/hydrogen blends were tested. Results suggests that stoichiometry has a major impact on NO emissions. An optimal window, minimizing both NO and NH3-slip emissions was defined using an equivalence ratio of 0.9. To qualitatively describe the observed trends, a simplified reactors network was considered. The analysis highlighted the most important reactions correlated to NO formation and the reason of the NO reduction at stoichiometry condition. On the other side an affordable and reliable numerical model was optimized and tested in the Adelaide Jet in Hot Co-flow burner. The latter is a simplified burner capable of mimicking MILD combustion conditions. A set of RANS simulations were run using the Partially Stirred Reactor (PaSR) approach, investigating different mixing model formulations: a static, a fractal-based and a dynamic formulation, based on the resolution of transport equations for scalar variance and dissipation rate. A study about the role of combustion models and kinetic mechanisms on the prediction of NO formation was also conducted. Finally, an analysis of the choice of a Heat Release Rate (HRR) marker for MILD (HM1 flame) and not MILD (HM3 flame) conditions was carried out. Once having awareness of the capability of the proposed numerical model, simulations were conducted to define the key aspects in simulating a flameless furnace, varying the composition of the fuel, considering methane/hydrogen and ammonia/hydrogen blends. In particular, for the latter case, existing kinetic schemes showed a major over-estimation of NO emissions, reason why an optimization study was conducted in a simplified reactor (well stirred reactor) using a Latin Hypercube Sampling. Finally, the first-of-its-kind digital twin based on CFD simulations for a furnace operating in flameless combustion conditions was created. A reduced- order model (ROM) based on the combination of Proper Orthogonal Decomposition (POD) and Kriging was developed for the prediction of spatial fields (i.e. temperature) as well as pollutant in the exhausts. / D’ici 2050, l’Europe devra découpler sa croissance économique de ses émissions de CO2. Il s’agit d’une réponse nécessaire au changement climatique et à la pollution de l’air induits par les émissions atmosphérique de gaz à effet de serre (GES) et de polluants (NOx). Un remplacement d’un pourcentage significatif des combustibles fossiles par des sources d’énergie renouvelables sera nécessaire. Cependant, la production d’énergie à partir des sources renouvelables est généralement intermittente et imprévisible. Cela nécessite un stockage d’énergie fiable à moyen et long terme, pour synchroniser la production et la demande d’énergie. L’option Power-to-Fuel, ou stockage chimique, peut être la clé d’un système énergétique durable. En effet, la conversion de l’excès d’énergie renouvelable en carburants de deuxième génération permettra de débloquer un stockage d’énergie à long terme et à haute densité, en assurant également une réduction de l’empreinte carbone. Ces carburants non conventionnels « verts » sont des mélanges de CH4, H2, CO et NH3. Cependant, pour exploiter le potentiel du Power-to-Fuel, il est nécessaire de développer une technologie de combustion efficace, avec des émissions de polluants pratiquement nulles, assurant des conditions de travail stables avec une charge et des carburants différents et des économies d’énergie significatives. Au cours des dernières années, une combustion dite « MILD », ou sans flamme, a attiré l’attention pour sa capacité à atteindre les objectifs mentionnés. Cependant, les études disponibles dans la littérature sont menées sur des systèmes de laboratoire (jet in hot co-flow) et avec des carburants conventionnels comme le gaz naturel ou le méthane. Les exemples utilisant des carburants non conventionnels sont rares et limités à quelques conditions de fonctionnement.Dans ce cadre, cette thèse de doctorat se concentre sur un triple aspect.Des campagnes expérimentales ont étudié la flexibilité du combustible dans un four sans flamme installé à l'ULB. L’ajout progressif d’hydrogène dans le méthane permet d’améliorer les caractéristiques de combustion, en réduisant le délai d’allumage et augmentant la réactivité du système, ce qui, par contre, cause un éloignement du système des conditions sans flamme. En effet, un seuil supérieur de 25% H2 a été identifié pour les mélanges méthane/hydrogène, pour travailler dans des conditions sans flammes (MILD), caractérisées par une faible augmentation de température et des émissions de polluants amoindries .Cela est conforme à l’objectif d’introduire de l’hydrogène « vert » dans le gazoduc (jusqu’à 20%) afin de réduire les émissions de CO2. D’autres campagnes expérimentales se sont focalisées sur le rôle de la géométrie d’injection (variation du diamètre de l’injecteur d’air) et de la longueur de la lance du carburant pour réduire les émissions des oxydes d’azote et récupérer les conditions sans flamme/MILD pour une teneur élevée en hydrogène. Enfin, des mélanges ammoniac/hydrogène ont été testés. Les résultats suggèrent que la stœchiométrie a un impact majeur sur les émissions d’oxydes d’azote. Une fenêtre optimale minimisant les émissions de NO et d’ammoniac imbrulées a été définie en utilisant un rapport d'équivalence de 0,9. Pour tracer qualitativement les tendances observées, un réseau de réacteurs simplifié a été construit. L’analyse a mis en évidence les réactions les plus importantes pour la formation des NOx et elle a permis de justifier la réduction des oxydes d’azote à l’état stœchiométrique.De l’autre côté, un modèle numérique robuste et fiable a été optimisé et testé pour le brûleur Jet in Hot Co-flow de l’Université d’Adelaide. Ce dernier est un brûleur simplifié capable de simuler les conditions de combustion MILD/sans flamme. Un ensemble de simulations RANS ont été effectuées à l’aide de l’approche du réacteur partiellement agité (Partially Stirred Reactor – PaSR - en anglais), en examinant les différentes formulations de modèles de mélange :une formulation statique, fractale et dynamique, basée sur la résolution des équations de transfert pour la variance scalaire et le taux de dissipation. Une étude sur le rôle des modèles de combustion et des mécanismes cinétiques dans la prédiction de la formation des oxydes d’azote a également été réalisée. Enfin, une analyse sur le choix d’un marqueur de taux de dégagement de chaleur (Heat Release Rate – HRR – en anglais) pour les conditions MILD et non MILD a été réalisée. Après validation, les modèles développés ont été utilisés pour définir les aspects clés de la simulation d’un four sans flamme, en variant la composition du combustible, pour des mélanges méthane/hydrogène et ammoniac/hydrogène. En particulier, pour ce dernier cas, les schémas cinétiques existants ont montré une surestimation importante des émissions d’oxydes d’azote, raison pour laquelle une étude d’optimisation a été menée dans un réacteur simplifié.Enfin, le premier jumeau numérique en son genre, basé sur des Simulations numériques de Dynamique de Fluides (CFD – Computational Fluid Dynamics en anglais) pour un four fonctionnant dans des conditions de combustion sans flamme, a été créé. Un modèle à ordre réduit (ROM – Reduced Order Model en anglais) basé sur la combinaison de la Décomposition Orthogonale aux valeurs Propres (POD) et du Kriging a été développé pour la prédiction des variables d’intérêt (température et espèces chimiques majeures) ainsi que des polluants dans les fumées. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

This work is devoted to describe the possibilities of mechanical activations of admixtures used in concrete. Then, the verification options of grind fly ash, both from brown and black coal, from the classical as well as fluidized combustion and examination their impact on physical and mechanical properties of concrete, especially on long-term development to old age 180 days. Further attention is paid to assessing the impact of the use of mechanically activated fly ash on hydration heat evolution and the associated volume changes in the age of 1 to 90 days. In this work are presented the results of basic technological tests on concretes using admixtures, especially fly ash.

The landfilling of slag obtained from the high alloyed Electric Arc Furnace (EAF) steel making process, constitutes an environmental treat for society as well as an economical problem for the companies producing it, due to the costs related to waste management practices. Conventional methods of slag recycling are abundantly used among the steelmaking business, but due to their particular physical properties, high- alloyed EAF slags cannot be properly valorized. Moreover, the pickling process that high-alloyed EAF steels undergo to, generates acidic wastewaters, that need to be collected and neutralized, before they can be recirculated into the natural water streams. For such a task, steel mills currently utilize slaked lime (a Ca rich mineral) to raise the pH and to remove any metal particles dissolved into the wastewaters. Slag contains high amount of Ca; therefore, it has already been tested as a slaked lime replacement. In fact, previous studies conducted at the Material Science and Engineering department at KTH Royal Institute of Technology showed, on a laboratory scale, that slag has the potential to replace lime for the neutralization and purification of the acidic wastewaters. This Master’s thesis project aims at upscaling the volumes of wastewaters to be tested, about 70 to 90 folds of the one from previous research, bridging the gap between laboratory tests and the industrial scale. The thesis is divided into three tranches, a first part where a water-salt solution conductivity trials were carried out, to model the behavior or slag dispersion in the acidic wastewaters. After the results obtained from the conductivity trials, neutralization trials with slag and the lime product currently in use by the company, were carried out at the neutralization plant in Outokumpu Stainless, Avesta (Sweden). The neutralization trials were carried out with 70 and 90 liters of acidic wastewaters and in order to perform the trials on site, the slag sample was dried and later sieved to a particle size of less than 350μm. Moreover, data was analyzed and compared to previous studies in order to have a clearer understanding regarding the neutralization efficiency of the slag, especially whether or not the technology would had worked on upscaled volumes. Additionally, the project checked if it was possible to find a generalized relationship between the mass of slag and volume of wastewaters required for the neutralization process. Slag demonstrated to be able to buffer the pH to the target values of 9, while also showing an almost linear trend compared to previous studies. The reaction progress between slag, lime, and the acidic wastewaters was also analyzed. / Deponering av slagg som erhållits från den höglegerade ljusbågsugn (EAF) stålframställningsprocessen utgör en miljömässig behandling för samhället och ettekonomiskt problem för de företag som producerar den på grund av kostnaderna för avfallshantering. Konventionella metoder för återvinning av slagg används i storutsträckning bland stålindustrin, men på grund av deras speciella fysiska egenskaper kan höglegerade EAF-slaggen inte värderas ordentligt. Dessutom produceras sura avloppsvatten av betningsprocessen som höglegerade EAF-stål genomgår som sedan måste samlas in och neutraliseras innan de kan återcirkuleras i det naturliga vattnet. För en sådan uppgift använder stålfabriker för närvarande släckt kalk (ett Ca-rikt mineral) för att höja pH-värdet och för att avlägsna alla metallpartiklar som löses upp i avloppsvattnet. Slaggen innehåller hög mängd Ca och därför har den testats som en ersättning till släckt kalk. Tidigare studier utförda vid avdelningen materialvetenskap och teknik vid Kungliga Tekniska Högskola visade på laboratorieskala att slagg har potential att ersätta kalk för neutralisering och rening av sura avloppsvatten. Detta examensarbete syftar till att skala upp volymerna av avloppsvattnet som ska testas till cirka 70–90 gånger av den från tidigare forskning, och därav fylla ut bryggan mellan laboratorietester och industriell skala. Avhandlingen är uppdelad i tre delar, Första delen innehåller försök på ledningsförmåga i en vatten-saltlösning som genomfördes för att modellera beteende eller slaggspridning i sura avloppsvatten. Efter de resultat som erhållits från konduktivitetsmätningarna genomfördes neutraliseringsförsök med slagg och kalk som för närvarande används av företaget vid neutraliseringsanläggningen i Outokumpu Stainless, Avesta (Sverige). Neutraliseringsförsöken genomfördes med 70 och 90 liter sura avloppsvatten och för att utföra experimenten på plats torkades slagg provet och siktades senare till en partikelstorlek på mindre än 350 μm. Dessutom analyserades data och jämfördes med tidigare studier för att få en tydligare förståelse för slaggens neutraliseringseffektivitet, särskilt huruvida tekniken skulle ha fungerat på större volymer, och även om det också var möjligt att hitta ett generaliserat samband mellan mängden slagg och volym avloppsvatten som krävs för neutraliseringsprocessen. Slagget visade sig kunna buffra pH till målvärdena 9, samtidigt som den visade en nästan linjär trend jämfört med tidigare studier. Reaktionsförloppet mellan slaggkalk och de sura avloppsvattnen analyserades också.

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