This is a thesis includes both experimental and modeling studies for high temperature slag/metal reaction system. / Bloating of metal droplets in emulsion is an important phenomenon in BOF steelmaking in controlling the kinetics of refining. This bloating controls the kinetics by mainly increasing the residence time (from ~¼th of a second to ~10-15 seconds) of the droplets in emulsion and the slag/metal surface (~5-6 times) area. The bloating behavior is determined by the decarburization kinetics. This work aims to develop fundamental understanding of the bloating phenomena through series of experiments and mathematical modeling to explore various factors affecting the kinetics of decarburization. An experimental study on varying the droplet carbon concentration, slag FeO concentration and basicity evidenced mixed controlled kinetics including transport of oxygen in the slag, interfacial (slag/metal) chemical reaction, nucleation and growth of CO bubbles. A mathematical model including these kinetic steps was developed. The model was able to demonstrate the partitioning of oxygen at the slag/metal interface into external (at the slag/metal interface) and internal (within droplet) decarburization in presence of the surface-active element sulfur. The model was developed using a single data set and validated for a wide range of experimental conditions. The model showed excellent agreement with experimental data for most of the reaction period but failed to predict a premature shutdown for droplets reacting with low conductivity slag. In order to understand this discrepancy, the slag ionic and electronic conductivity were varied which showed a premature shutdown of decarburization reaction with low conductivity slag and continuation of the reaction to the thermodynamic limit with high conductivity slag. A mechanism of generation of local electric field by accumulation of charge at the slag/metal interface was proposed to explain the premature shutdown of the reaction for low basicity slags. In all experiments with low conductivity slag sulfur was observed to delay the onset of internal decarburization. However, this effect was diminished or disappeared completely with high conductivity slag. This observation motivated additional experiments to study the competitive adsorption of oxygen and sulfur at the slag/metal interface both through experiments and modelling. It was shown that for low conductivity slag, sulfur poisoning inhibited reaction at the surface whereas for the high conductivity slags the faster transport of oxygen allowed oxygen to compete with sulfur for adsorption sites creating pathways for oxygen into the droplet. By including the possibility of competitive adsorption in the model it was possible to predict the behavior of high sulfur droplets in conductivity slags where the only modification to the model was to change the mass transfer coefficient as appropriate to the higher conductivity. Extension of this study to include silicon in the droplet showed significant effect on decarburization both in delaying bloating as well as increasing peak rate of decarburization. / Thesis / Candidate in Philosophy

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Dry abrasive blasting is one of the most widely used methods of surface preparation. Air emissions from this process include particulate matter (PM) and metals. Spent abrasive generated from this process may be hazardous in nature. With increasing concern on health effects due to silica emissions from sand, use of alternative materials is suggested by health and regulatory agencies. The objective of this research was to evaluate performance of expendable abrasives and determine PM emission factors. Dry abrasive blasting was performed in an enclosed chamber and total PM samples were collected. Three commonly used expendable abrasives, coal slag, copper slag and specialty sand, were used to evaluate cleaner alternatives. Blast pressure and abrasive feed rate, two important process conditions were varied to study their effect on performance of an abrasive. Productivity, consumption and emission factors (performance parameters) were calculated and their variation with pressure and feed rate was evaluated. Two dimensional and three dimensional predicted models were developed to estimate the performance at intermediate blast pressure and feed rate conditions. Performance of the three abrasives was compared with respect to emission potential, productivity and consumption. Emission factors developed in this research will help in accurate estimation of total PM emissions and to select cleaner abrasives and optimum process conditions that will results in minimum emissions and reduced health risk. The productivity and consumption models will help is estimating life cycle costs including material cost, equipment cost, energy cost, labor costs, waste disposal cost, and compliance costs. Consumption models will also help in determining the quantity of spent abrasive generated, identify abrasives with lower material consumption, and identify process conditions that generate minimum spent abrasives. In addition, these models will help industries in making environmentally preferable purchasing (EPP), which results in pollution prevention and cost reduction.

O uso de escória de alto forno como aglomerante alternativo ao cimento portland tem sido objeto de vários estudos no Brasil e no exterior. Além de representar vantagens ao meio ambiente por ser um resíduo, a escória apresenta boas possibilidades de emprego, principalmente pelo baixo custo e por suas vantagens técnicas das quais se destacam a elevada resistência mecânica, a boa durabilidade em meios agressivos, o baixo calor de hidratação. No entanto, o emprego deste material carece de estudos detalhados da retração, muito superior à do cimento portland. Este trabalho teve como objetivo estudar a cinética das retrações autógena e por secagem não restringidas do cimento de escória ativada em função, principalmente, do tipo e teor de ativadores empregados. Para a retração autógena, o corpo-de-prova foi selado com papel alumínio protegido internamente com plástico. As medidas estenderam-se de 6 horas até 112 dias. O fenômeno da retração também foi analisado com base nos resultados dos ensaios de porosimetria, calorimetria, termogravimetria e difração de raios X. Foram empregados como ativadores: silicato de sódio, cal hidratada + gipsita, cal hidratada e hidróxido de sódio. Como referência foi adotado o cimento portland da alta resistência inicial CPV-ARI. De acordo com os resultados obtidos, a ativação da escória com silicato de sódio apresentou retração por secagem e autógena superior à apresentada pelos demais ativadores e pelo cimento portland. A maior parte dessa retração medida ocorre até os 7 dias. A retração por secagem ocorre em dois estágios: o primeiro logo após a desmoldagem e o segundo a partir do início da formação dos produtos hidratados. O início da retração autógena coincide com o segundo estágio da retração por secagem. Com base nos ensaios de microestrutura, são determinantes para a elevada retração do cimento de escória ativada com silicato de sódio: a baixa porosidade, caracterizada pela predominância quase total de mesoporos; o elevado grau de hidratação e natureza dos produtos hidratados, com predominância quase total de silicato cálcio hidratado (C-S-H). Na ativação com cal e com cal mais gipsita, a composição diferente dos produtos hidratados (baixa formação de C-S-H e presença significativa de fases aluminato e sulfoluminato, respectivamente) altera a porosidade e a retração, principalmente a autógena que apresenta valores inferiores à do cimento portland. A ativação com hidróxido sódio é caracterizada pela elevada retração autógena e baixa formação de C-S-H, com presença significativa de fases aluminato. / The use of ground granulated blast furnace slag (BFS) as an alternative binder to portland cement has been the subject of numerous studies in Brazil and other countries. Because BFS is a residue, its use benefits the environment. Furthermore, BFS cement is less costly and shows technical advantages if compared with normal portland cement, namely the higher strength, good durability in aggressive environments, and low heat of hydration. On the other hand, the high shrinkage of BSF cement is often indicated as one of the major limiting aspects for its use. The objective of this research was to study the development of unrestrained autogenous and drying shrinkage of BSF cement as function, mainly, of the chemical activator types and dosages. Autogenous shrinkage was measured in fully aluminum foil and plastic sheet wrapped specimens. Measurements were taken from 6 hours up to 112 days. Shrinkage was also analyzed in conjunction with mercury posorimetry, conduction calorimetry, thermogravimetric analysis and X-ray diffraction tests. Activators used were sodium silicate, hydrated lime + gypsite, hydrated lime and sodium hydroxide. High early strength portland cement was used as reference. The results showed that autogenous and drying shrinkage were larger when BFS was activated with sodium silicate. Most of the shrinkage occurs before 7 days of hydration. Drying shrinkage occurs in two phases: the first phase immediately after demolding, and the second phase concurrently with the formation of the hydrated products. Autogenous shrinkage coincides with the second phase of the drying shrinkage. Based on microstructure analysis, determining factors could be identified that respond for the high shrinkage of sodium silicate activated BFS cement: low porosity, mostly mesopores; high degree of hydration and chemical nature of the hydrated products, essentially calcium silicate hydrate - C-S-H. Activation with hydrated lime and hydrated lime plus dehydrated calcium results low amounts of C-S-H and significant quantities of aluminate and sulphoaluminate phases, respectively. Porosity and shrinkage, mainly autogenous, are lower than that verified for portland cement mixtures. Activation with sodium hydroxide causes high autogenous shrinkage, small amounts of C-S-H and significant quantities of aluminate phases.

Les industries sidérurgiques et du manganèse génèrent des quantités de laitiers très importantes qui ne sont aujourd'hui peu ou pas valorisées pour la formulation de liants hydrauliques dans le domaine des matériaux de construction. Si le laitier de haut fourneau moulu est bien intégré dans la filière des matériaux de construction, le laitier de convertisseur est majoritairement utilisé sous forme de granulats et le laitier de silicomanganèse granulé n'est aujourd'hui pas valorisé dans cette filière. Les sociétés ArcelorMittal, Ecocem et Eramet produisent ou exploitent ces laitiers, très différents de par leurs origines et leurs compositions, et cherchent à développer des filières de valorisation pour ce type de coproduit. Des études ont déjà montré que le laitier de convertisseur et le laitier de silicomanganèse peuvent être intégrés au sein de matrices cimentaires en remplacement partiel du ciment, mais peu de données sont disponibles sur la connaissance des mécanismes d'hydratation de ces systèmes cimentaires à base de laitier, sur la durabilité de tels systèmes et sur l'impact environnemental que peut impliquer l'utilisation de ces laitiers. Nos travaux de recherche ont porté, sur la caractérisation des laitiers étudiés, en particulier sur la granulométrie, la chimie et la microstructure, puis sur leur réactivité. Les résultats ont montré que le laitier de silicomanganèse peut être comparable au laitier de haut fourneau du point de vue de son hydraulicité latente mais qu'il présente une chimie différente avec notamment une teneur en chaux moindre et une faible part de résidu inerte (10%). Le laitier de convertisseur, qui présente une partie inerte (23%) constituée de composés riches en fer, est fortement basique compte tenu de la présence de chaux et de portlandite et présente un comportement hydraulique. La formulation de systèmes cimentaires binaires (ciment/laitier) a permis de montrer que le laitier de silicomanganèse ajouté à du ciment Portland forme, comme le laitier de haut fourneau, des hydrates (silicates de calcium hydratés) qui participent au développement des résistances mécaniques, similaires. Le laitier de silicomanganèse peut donc être un bon matériau de remplacement du ciment pour la formulation de liants hydrauliques dans le domaine des matériaux de construction. Le laitier de convertisseur présente une plus faible activité hydraulique que les autres laitiers et participe peu au développement de la résistance mécanique des systèmes cimentaires. Cependant, sa forte basicité en fait un bon activateur des laitiers hydrauliques latents. Des systèmes ternaires (laitier de convertisseur/ciment/laitier hydraulique latent) ont donc été réalisés et ont permis de montrer la capacité du laitier de convertisseur à activer le laitier de haut fourneau ou le laitier de silicomanganèse. Ces systèmes cimentaires, composés au minimum de 80 % de laitiers, présentent des performances mécaniques intéressantes pour le domaine des liants hydrauliques routiers. En complément de l'aspect formulation, une étude environnementale a été menée et a permis de montrer que les laitiers ne présentent pas de risque vis-à-vis du relargage de polluants lors de leur utilisation comme composants de matériaux hydrauliques routiers / The steelmaking and manganese industries produce large amount of slag which are little upgraded today for the formulation of hydraulic binder in the field of civil engineering. The ground blast furnace slag (GGBFS) is integrated in the building materials industry but the converter steel slag (BOF slag) is mainly used as aggregates and the silicomanganese slag (LSiMn) is co granulated slag is now not upgraded in this sector. The companies ArcelorMittal, Eramet and Ecocem produces or exploit these slags, which are very different (origins and compositions), and want to develop the valorisation of these byproduct in the field of materials for building construction. Some studies have already shown that the steel slag and the silicomanganese slag can be integrated into cement matrix as component for cement industry. But few data exist about mechanism of hydration of these slags in cement systems, the sustainability of such systems and the environmental impact which involve the use of these slags. Our research concerns first the characterization of our slags, particularly the particle size distribution, the chemical composition and microstructure, and their reactivity. The results showed that the silicomanganese slag can be comparable with the ground granulated blast furnace slag because of their latent hydraulic behaviour but he has a different chemistry composition with lower calcium content and a little part of inert (10%). The steel slag, which has 23% of inert portion (compounds rich in iron) is very basic due to the presence of lime and portlandite and has a hydraulic behaviour. The formulation of binary systems cement (cement / slag) shown that the silicomanganese slag added to Portland cement forms, like blast furnace slag, hydrates (hydrated calcium silicates) which participate in the development of compressive strength. Then, the utilization of silicomanganese slag can be a good alternative for the formulation of hydraulic binders in the field of building materials. The steel slag has a little activity than other hydraulic slags cited and has a little participation for the development of the compressive strength. However, its high alkalinity makes it a good activator of latent hydraulic slags. Ternary cementitious systems (cement/steel slag/slag with latent hydraulic behaviour) have been prepared and show the ability of converter slag to activate the blast furnace and silicomanganese slags. These cementitious systems, composed of at least 80% of slags, have good mechanical properties for hydraulic road binders. In addition to these works, an environmental study was conducted for the slags and the cementitious matrix. The results show that the low leaching of pollutant allows the utilization of our slag as hydraulic road materials

This work investigates the interactions of carbonaceous materials (metallurgical coke, natural graphite and HDPE/coke blends) with three EAF slags [FeO: 24% to 32%]. Experiments were conducted using the sessile drop technique (1500??C-1600??C) with off-gases (CO, CO2) measured using an IR analyzer; the wetting behaviour was determined from contact angle measurements. Estimation of slag foaming behaviour was determined from the droplet volume changes calculated using specialized software. At 1550??C, all slags were non-wetting with coke due to increased surface tension due to sulphur. At 1550??C, slag 1 was initially non-wetting on natural graphite due to gas entrapment in the slag droplet; the wetting improved after that. Other slags showed comparatively better wetting. At 1600??C, all slags were non-wetting with coke. Slags showed a shift from non-wetting to wetting behaviour with natural graphite. Slag/coke reactions produced high off-gases levels causing extensive FeO reduction; gas entrapment in the slag was poor (small volume droplets). Slag/natural graphite interactions revealed both slow gas generation rates and FeO reduction, and excellent gas entrapment (higher droplet volumes) with minor changes in slag properties due to low ash levels. The iron oxide reduction rates were determined to be 1.54x10-5 and 4.2x10-6 mol.cm-2/sec (Slag 1, 1550??C) for metallurgical coke and natural graphite respectively. Slag interactions with coke/HDPE blends showed increasing off-gas levels with increasing HDPE levels. Blend#3 produced the highest off-gas levels, extensive FeO reduction and displayed significantly higher slag foaming and better wetting compared to coke. Our line on trends compared well for slag/carbon interactions and resulted in deceased specific energy consumption and carbon usage and increased productivity. These findings have enhanced the possibility of utilizing polymeric wastes in blends with coke in EAF steelmaking for slag/carbon interactions.

Copper losses to slag are generally between 0.7-2.3% during the copper matte smelting stage. In this study, the aim was to reduce these losses in the slag phase. For this purpose, usage of some additives (especially calcined colemanite labeled as CC, boric oxide-B2O3 and calcium oxide-CaO as well) as flux material was investigated. The flash furnace matte-slag (FFM-FFS) obtained from Eti Copper Inc. and a master matte-slag (MM-MS) produced synthetically were used as starting materials. Additives were tested in various amounts under two different atmospheres (N2 and low Po2 obtained by mixture of CO2/CO gases). Temperature and duration were also used as experimental variables. Experimental results have indicated that 2 hours was sufficient to obtain a low copper content in slag about 0.3% and 0.4% for FFS and MS, respectively. It was also seen that the copper content in slag decreased with increasing CC addition at all oxygen partial pressures and at all temperatures. Furthermore, the addition of all additives up to 4% had great influence in lowering the copper content in the final slags (~0.3%Cu). From FactSage calculations, it could be concluded that the colemanite addition decreased the liquidus temperature which led to early melting of slag and allowed enough duration for settling of matte particles within the slag without substantial changing its viscosity, which resulted in less mechanical copper losses to the slag. By using colemanite in copper production, it was possible that a new application area for boron compounds which are produced in Turkey could be created.

In this study it was aimed to analyse refining processes such as decreasing reducible oxide content of ladle slag with affecting parameters in low carbon aluminum killed grades and for the research Erdemir low carbon steel grades 7112K and 7110K are selected. There was a negative correlation between reducible oxide amount in ladle slag and desulphurization capacity of ladle slag with metal-slag reaction and steel internal cleanliness. To refine these properties of slag, aluminium dross, which was aluminium production discard and has a metallic content around %30-35 was used and after ladle treatment operation, decrease in reducible oxides such as FetO, MnO, SiO2, P2O5 was analysed. After the study it was observed that 653 kg. of converter slag leaked during tapping of steel and SiO2 ve P2O5 content of ladle slag had negligible change after ladle treatment. According to the results, it is observed that initial %10-12 (FetO + MnO) content was reduced to % 4.5-5.0 (FetO + MnO) after ladle treatment with use of aluminium dross. Beside of this, in order to see the effect of this slag reduction on steel cleanliness, low carbon aluminium killed grades were compared with ultra-low carbon aluminium killed grades having (FetO + MnO) content of %16-17 in slag. It was seen that reoxidation of aluminium (loss of dissolved aluminium) during continuous casting for ULC (ultra-low carbon) gradesis 144 ppm but for LC grades it was 94 ppm and it was being expected that ULC steel group would have higher inclusion content after casting.

Use of alternative raw materials, especially industrial by-products, is necessary for a sustainable cement industry. By replacing clinker with industrial by-products, consumption of natural resources and energy is decreased. Therefore, both economical and environmentally friendly cements are produced. Several industrial by-products such as fly ash, silica fume, and slag, one of the most widely used industrial by-products, can be used to produce standard blended cements. Besides its many advantages, slag cements are reported to have lower early compressive strengths. Therefore, the objective of this study is to investigate the early-strength improvement of slag cements. In the experimental study, in order not to change the cement type, the additives were incorporated within the minor additional constituent ranges, i.e. less than 5%. First, CEM III/A type control cement was prepared by blending clinker (K) and slag (S), which were separately ground in a laboratory type ball mill. Ground limestone (L) of varying fineness, silica fume (F), and sodium hydroxide (N) were prepared to be used as minor additional constituent. The ground clinker, slag, and gypsum, and the additives at various ratios were blended to obtain 15 CEM III/A type slag cements other than the control. Finally, the fresh and the hardened properties of the cements were determined. As a result of this experimental study, it was observed that addition of limestone generally increased the early compressive strength of slag cements. However, silica fume and sodium hydroxide either decreased or did not affect the early compressive strength of the slag cements.