The purpose of the current study is to increase the understanding of different steelmaking processes at the decarburization stages by use of mathematical modeling. More specifically, two De-Laval nozzles from a VOD (Vaccum Oxygen Decarburization) process, which is used for producing stainless steels with ultra-low carbon grades, was investigated for different vessel pressures. Moreover, the post combustion phenomena in a BOF or LD (Linz-Donawitz) process as well as an AOD (Argon Oxygen Decarburization) process were studied focusing on the decarburization stage. Two industrial VOD nozzles were numerically studied and compared at different temperatures and ambient pressures. Flow patterns of the oxygen jet under different ambient pressures were predicted and the flow information at different positions from the nozzle was analyzed. In addition, the effects of different ambient temperatures on the jet velocity and the dynamic pressure were compared. The predictions revealed that a little under-expansion is somewhat helpful to improve the dynamic pressure. The jet dynamic pressure and its width for the specific nozzle geometry were also studied. It was observed that a variation in the ambient pressure can influence the jet momentum and its width. In addition, a high ambient temperature was found to have a positive effect on the improvement of the jet dynamic pressure. Furthermore, it was found that a change in ambient pressure has a stronger effect on the jet force than a change in the ambient temperature. In addition, it was proved that the profiles of the dynamic pressure at a certain blowing distance fit well to Multi-Gaussian distribution. Post combustion in a BOF/LD and an AOD process during decarburization was also studied. Two mathematical models were created to show the post combustion phenomenon inside the converters, respectively. For the CFD modeling of the two processes, the realizable k-ɛ model, the species transport model and the discrete ordinate were adopted to calculate the turbulence, gas reaction and radiation present in the gas phase in the converter. For the BOF/LD modeling, a series of plant tests were conducted to collect data, which were used in the current model. These include the off-gas information, emissivity data, oxygen blowing parameters and the chemical composition of steel. After the simulation, the predicted flow pattern and detailed information of the gases taking part in the post combustion were compared to plant data. Specifically, the off-gas data from the plant was used for the model verification. The measured CO2 concentration was 15-20 wt% and the predicted value from the modeling was 16.7 wt%. For the AOD converter of interest in the current work, a fan is installed in the end of the AOD flue to help extract the off-gas from the converter. The influence of different fan gauge pressures as well as temperatures of the gas mixture, containing the generated CO and argon, on the post combustion in the whole AOD system was studied. It was indicated from the modeling results that the post combustion was only present in the flue for the present modeling conditions. Moreover, a critical fan gauge pressure (approx.. -550 Pa) was found which could yield a maximum post combustion in the flue gas. For both two models (BOF/LD and AOD), simulations indicated that a change of the converter temperature from 1500 to 1700 °C did not influence the post combustion reaction to a large degree. In addition, these two models can be regarded as the first step for a future more in-depth modeling work of the post combustion. / <p>QC 20130913</p>

During production of steel, slag is formed as a by-product. The process of steelmaking involves usage of additives such as chromium or vanadium as reactants to optimize and produce high quality steel. Vast amounts of slag are formed and there is a continuous search for applications that can make good use of the slag. Currently the use of slag in cleaning of metal polluted waters is researched and promising results has been found for many different types of slags. In this work two different AOD-slags has been used as sorbents for some selected elements (Zn, V, Cr, Mo, Pb, Li, Cd, Ba, Cu, Ni). The main difference between the two slags is the reducing agent that has been used, aluminium and silicon. This results in slags with different adsorption properties. The aluminium reduced slag show tendency for better adsorption capacities in general for the tested elements (Zn, V, Cr, Mo, Pb, Li, Cd, Ba, Cu, Ni), with a few exceptions. The buffering capacity of the materials were high, shown by the fact that final pH reached nearly 11.5 independent of the start pH (varied between 2 and 8). The adsorption process was rather quick and 24 minutes contact time was in most cases sufficient to reach equilibrium. For several of the elements e.g. Lithium, the maximum capacity of the slags was not reached even though a load of 3,07 mg Lithium was added per gram of slag.

Dissertação (mestrado)—Universidade de Brasília, Centro de Estudos Avançados Multidisciplinares, Programa de Pós-Graduação em Desenvolvimento, Sociedade e Cooperação Internacional, 2013. / Submitted by Raquel Viana (raquelviana@bce.unb.br) on 2014-10-16T20:07:07Z No. of bitstreams: 1 2013_AntonioAugustoGomesdosSantosSilva.pdf: 14411364 bytes, checksum: 71f6bc67bca3111a0dc6b908d2a67adf (MD5) / Approved for entry into archive by Tania Milca Carvalho Malheiros(tania@bce.unb.br) on 2014-10-16T20:23:54Z (GMT) No. of bitstreams: 1 2013_AntonioAugustoGomesdosSantosSilva.pdf: 14411364 bytes, checksum: 71f6bc67bca3111a0dc6b908d2a67adf (MD5) / Made available in DSpace on 2014-10-16T20:23:54Z (GMT). No. of bitstreams: 1 2013_AntonioAugustoGomesdosSantosSilva.pdf: 14411364 bytes, checksum: 71f6bc67bca3111a0dc6b908d2a67adf (MD5) / A inserção de atores não estatais, como as organizações não governamentais – ONGs, no processo de execução das ações de Ajuda Oficial ao Desenvolvimento (AOD) revela-se significante. As mudanças no contexto internacional, a maior participação da sociedade civil organizada e o advento da globalização, alteraram o conceito do moderno Estado-nação e o próprio Sistema Internacional (SI). Como novo paradigma, examinamos o papel exercido pelas ONGs como executoras da AOD, que permite a inserção no SI. E como os estados utilizam-se dessas estruturas para avançar sua própria política externa, apoiando e financiando suas atividades, muitas delas antes prerrogativas do Estado. O trabalho está dividido em seis segmentos onde, primeiro, foram revistas as teorias que dão sustentação aos constructos de Relações Internacionais pertinentes. Em seguida foram pesquisadas a origem e a evolução das organizações voluntárias, hoje conhecidas como ONGs. Num terceiro segmento foi perscrutada a relação entre a cooperação internacional e a Ajuda Oficial ao Desenvolvimento, tanto por parte dos países doadores, quanto dos beneficiários. Da estrutura em transformação que permite a inserção das ONGs no Sistema Internacional como parceiras de Estados-soberanos ocupou-se a etapa seguinte desse exercício. Tratase de um fenômeno global, que dá sinais de vitalidade nos campos das relações internacionais e da cooperação. Foram comparados, em seguida, os casos de Ajuda Oficial ao Desenvolvimento, seus modelos de recrutamento de parceiros e aplicação de recursos, de dois países, grandes doadores de AOD: os Estados Unidos, maior doador global, e a Suécia, maior doadora em relação à renda nacional bruta (RNB). Consideramos, por fim, os elementos motivadores das doações e parcerias, que podem se situar entre o princípio da solidariedade e um conjunto de objetivos estratégicos dos estados doadores, uma vez que as ONGs encontram-se num campo de conflito de interesses de estados diversos. _______________________________________________________________________________ ABSTRACT / The inclusion of non-state actors, such as non-governmental organizations – NGOs, in the process of executing actions of Official Development Assistance (ODA) has shown to be significant. Transformations in the international context, with greater participation of the Organized Civil Society (OSC) and the advent of globalization, have altered the concept of the modern Nation-State, as well as the structure of the International System (IS) itself and encourage an analysis of the role of NGOs in the delivery of ODA, which allows for their inclusion in the IS. States often make use of these structures as tools of their own foreign policy, supporting and financing their activities, many of which, in the past, restricted to States’ own prerogatives. This study is divided into six segments where, firstly, applicable International Relations theories concepts which support this research were scrutinized. The following segment presents an investigation of the origins and the evolution of volunteer organizations which have evolved into our contemporary NGOs. The relationship between international cooperation and ODA methods of aid delivery, both on the donors’ and the beneficiaries’ ends was the subject of the third section of this exercise, followed by an examination of the changing structure of the International System, which allows for NGOs participation, indeed a global phenomenon showing signs of vitality both in the fields of international relations and cooperation. The last two segments attempt at a review of ODA partnership practices and recruiting methods, as well as resources delivery by two large donor countries: the United States as the biggest global donor in absolute numbers and Sweden, the largest donor per Gross National Income (GNI). The final section considers the motivating factors fueling donations to ODA partners, as they may lie between the principles of solidarity and donor States’ own strategic objectives, since NGOs often find themselves operating in areas of conflict of interests of diverse states.

Abstract : This is a study concerning comparisons between the Dubovik Aerosol optical depth (AOD) retrievals from AEROCAN (ARONET) stations and AOD estimates from simulations provided by a chemical transport model (GEOS-Chem : Goddard Earth Observing System Chemistry). The AOD products associated with the Dubovik product are divided into total, fine and coarse mode components. The retrieval period is from January 2009 to January 2013 for 5 Arctic stations (Barrow, Alaska; Resolute Bay, Nunavut; 0PAL and PEARL (Eureka), Nunavut; and Thule, Greenland). We also employed AOD retrievals from 10 other mid-latitude Canadian stations for comparisons with the Arctic stations. The results of our investigation were submitted to Atmosphere-Ocean. To briefly summarize those results, the model generally but not always tended to underestimate the (monthly) averaged AOD and its components. We found that the subdivision into fine and coarse mode components could provide unique signatures of particular events (Asian dust) and that the means of characterizing the statistics (log-normal frequency distributions versus normal distributions) was an attribute that was common to both the retrievals and the model. / Résumé : Cette étude compare des épaisseurs optiques d’aérosols (AOD) à 5 stations arctiques d’AEROCAN (AERONET), obtenues d’une part à l’aide de l’algorithme d'inversion de Dubovik appliqué à des mesures in situ, et d’autre part du modèle de transport chimique (GEOS-Chem : Goddard Earth Observing Système Chemistry). Les produits d’AOD associés à l’algorithme d’inversion sont divisés en composantes totales, fines et grossières. Pour chacune des 5 stations (Barrow, Alaska, Resolute Bay, au Nunavut, 0PAL et PEARL (Eureka), Nunavut, et Thulé, au Groenland), la période de récupération est de janvier 2009 à janvier 2013. Nous avons également utilisé les mesureurs d’AOD de dix autres stations canadiennes de latitudes moyennes, à des fins de comparaison. Les résultats de l’étude ont été soumis à la revue Atmosphere-Ocean. Pour résumer brièvement ces résultats, le modèle a généralement, mais pas toujours, eu tendance à sous-estimer l'AOD moyenne et de ses composantes. Nous avons constaté que la subdivision en composantes fine et grossière pourrait fournir des signatures uniques d'événements particuliers (poussière asiatique) et que les moyens de caractériser des statistiques (les distributions de fréquence log-normale versus les distributions normales) était un attribut qui était commun aux deux les mesureurs et le modèle.

Argon oxygen decarburization slag (AOD) was tested in batch and column experiments to investigate its phosphorus (P) removal performance. The effects of factors such as AOD dose, initial P concentration of the feeding solution, and aging on the P removal ability of the slags were analyzed. In a column experiment, electric arc furnace slag (EAF), blast furnace slag (BFS) and AOD were combined in five different ways to determine optimal conditions for P removal. In another column experiment, the three types of slag were modified with polyethylene glycol (PEG) and NaOH to adjust their dissolution properties and the effect on P removal performance was examined. In the batch experiments, AOD exhibited very promising P removal ability. It removed 94.8% of P from 6.5 mg P L-1 synthetic solution in 4 hours with a dose of 5 g L-1. Maximum P removal capacity of 27.5 mg P g-1 was achieved. In the dual-filter column experiment, the column packed with only EAF had the best P removal performance (consistently above 93%). Amorphous calcium phosphate (ACP) was identified as the main P species in the five slag samples collected from the outlet chambers. The contributions from crystalline calcium phosphate (Ca-P) and P adsorbed on iron/aluminum (hydr)oxides were greater in samples from the inlet chambers. The P speciation results revealed that P was predominantly removed by the slags through formation of ACP. The second column experiment showed that modification with PEG and NaOH solution only enhanced short-term P removal by the slags. However, exhaustion of the modified slags occurred much earlier, indicating that the modification process had shortened the lifespan of the slags. Untreated AOD showed better P removal than untreated EAF until pore volume 244, probably due to faster dissolution rate of gamma dicalcium silicate (dominating in AOD according to the XRD results) than of beta dicalcium silicate (dominating in EAF). / <p>QC 20170830</p>

The literature has well-documented the deleterious effect of alcohol and other drug (AOD) use on adolescent development and future outcomes. Despite these devastating results, some adolescents are able to attain high achievement as adults, despite their earlier AOD use. Secondary quantitative analyses were conducted on nationally-representative data from the National Longitudinal Study of Adolescent to Adult Health. Longitudinal data, collected at Wave I (1994-1995), and Wave IV (2007-2008), were analyzed from a sample of 4,266 American high school students between the ages of 13-19 years. The majority of high school students in the sample self-reported AOD use (n=2,833, 66.4%), compared to those students who self-reported non-AOD-use (n=1,433, 33.6%). Statistically significant findings indicated that with the exception of household income, non-AOD-using adolescents experienced more favorable outcomes with regard to educational attainment, occupational status, and involvement with the criminal justice system when compared to their AOD-using counterparts. In addition, through ordinal and binomial logistic regressions, the present study identified risk and protective factors affecting the adult outcomes of adolescents who used AODs. Gender, age, grade level, importance of religion, frequency of prayer, fighting, suspensions, expulsions, and happiness in neighborhood were statistically significant in predicting educational attainment. Grade level and feeling safe in school were found to be statistically significant in predicting occupational status. Gender, fighting, suspensions, and alcohol use by best friends were statistically significant in predicting involvement with the criminal justice system.

Manganese is an essential alloying element in the 2nd and 3rd generation of Advanced High Strength steels (AHSS) containing 5 to 25% manganese. A combination of excellent strength and ductility makes these grades of steel attractive for the automotive industry. To produce these steels to meet metallurgical requirements the main concern for the steelmakers is to decrease the carbon concentration as low as 0.1% while suppressing the excessive manganese losses at high temperatures. Argon Oxygen Decarburization (AOD) is a promising candidate for the refining of high manganese steels. This work has studied the kinetics of decarburization and manganese losses during the argon oxygen bubbling into a wide range of iron-manganese-carbon alloys. It was shown that decreasing the initial carbon content increased the manganese loss. In the competition between manganese and carbon for oxygen, alloys with lower initial manganese concentrations consumed a higher portion of oxygen for decarburization. This behavior was not expected by thermodynamics and the results did not support the concept of the critical carbon content either. It was demonstrated that for lower range carbon (≤0.42%) alloys, the total manganese loss can be explained by considering multiple mechanisms in parallel; oxide formation (MnO) and vapor formation (Mn (g)), and formation of Manganese mist by evaporation-condensation (Mn (l)). The evaporation-condensation mechanism was proposed with the assumption that the heat generated from MnO and CO formation increases the temperature at the surface of the bubble which facilitates the evaporation of manganese at a high vapor pressure. Consequently, manganese vapor condenses as fine droplets at the lower temperature inside the bubble. Although dilution of oxygen with argon increased the efficiency of oxygen for decarburization as expected from the mechanism of the AOD process, manganese loss did not stop completely at higher argon concentrations in the gas mixture. Therefore, the bubble and melt do not fully equilibrate with respect to Mn and C. For high carbon alloys (1%), there was excess oxygen after accounting for CO and MnO formation. According to mass balance and thermodynamic calculations, and assuming manganese loss by evaporation was negligible it was shown that oxygen was distributed amongst MnO, FeO, CO, and CO2. It was demonstrated that increasing temperature resulted in the higher manganese loss as a mist and by simple evaporation due to the increased vapor pressure and less manganese loss by oxidation. Furthermore, it was found that the rate of decarburization increased with increasing temperature due to more partitioning of oxygen to carbon than manganese. In addition, it was found that the variations of depth of lance submergence did not affect the rate of decarburization or manganese loss. This means that the reactions occur within such a short time that prolonged time after the reaction is completed does not lead to a repartitioning of the species. / Thesis / Doctor of Philosophy (PhD)

<p>This dissertation consists of three interrelated articles about supporting instructors to develop their facilitation skills both on the instructional and emotional sides during online case-based discussions. In the first study, we examined the influence of instructors with varying levels of experience on student participation and interaction in online case discussions. Findings showed that while both expert and novice instructors utilized facilitation strategies in clusters to facilitate discussions, the novice instructor displayed less flexibility as a facilitator, and these differences impacted student activeness. Our second study explored experts’ teaching practices, such as structuring, facilitating, and assessing online case discussions, and the reasons behind their decisions. We found that the experts clustered strategies during online case discussions while maintaining differences in how they implemented them. There was practical guidance provided for novice instructors that could be adapted to meet their own needs. Using a learning experience design lens, the last paper conceptually discussed opportunities for facilitating students’ emotions during online case discussions and offered suggestions that instructors can incorporate into the planning, implementation, and evaluation phases.</p>

Eutrofieringen av Östersjön är omfattande och ses i dag som ett av områdets allvarligaste föroreningsproblem. Orsaken till detta är en förhöjd näringsbelastning av kväve och fosfor. Den ökade näringsbelastningen beror på att de naturliga flödena av dessa näringsämnen har rubbats, vilket är en direkt följd av urbaniseringen. Sveriges enskilda avlopp står för 16% av den totala fosforbelastningen till Östersjön. År 2006 skärptes de svenska riktvärdena för fosforbelastning från enskilda avloppsanläggningar. Nästan en tredjedel av dagens 625 000 enskilda avloppsanläggningar klarar inte dessa skärpta krav. Som ett led i detta har forskning och utveckling inom ämnesområdet bedrivits under de senaste 20 åren. Forskningen har resulterat i nya effektivare avloppsreningstekniker där så kallade reaktiva filtermaterial används som fosforfälla. Gemensamt för de reaktiva filtermaterial som har utvecklats är dess höga kalciumhalt och stora specifika fastläggningsytor, vilket vid höga pH-värden skapar förutsättning för en hög fosforfastläggningen. Den reaktiva filtermaterialstekniken möjliggör ett resurseffektivt användande av fosfor då recirkulation av grundämnet möjliggörs. Syftet med detta kandidatexamensarbete har varit att undersöka om livslängden för två olika reaktiva filtermaterial kan förlängas genom en dualfilterteknik. En teknik där fosforfällan består av två olika reaktiva filtermaterial med olika egenskaper. Hypotesen har varit att en dualfilterteknik kan minska kalciumutlakningen från filtret. De två dualfilter som har undersökts är Polonite®–Sorbulite® och Argon oxygen decarburisation–Hyttsand. Arbetet har utförts som en kolonnstudie. De viktigaste analyserna som har genomförts är alkalinitet och kalciumutlakning. Arbetes slutsatser listas nedan: o Det dualfilter som har visat bäst förutsättningar som långvarig fosforfälla i enskilda avloppsanläggningar är Polonite®–Sorbulite®. o Materialet Sorbulite® har visat sig kunna minska kalciumutlakningen, vilket bekräftar studiens hypotes. Arbetets resultat pekar på att Sorbulite® kan användas för att förlänga filterlivslängden för det reaktiva filtermaterialet Polonite® . o Materialet Hyttsand uppvisar ingen förmåga till att kunna samla upp utlakade kalciumfraktioner. Detta medför att Hyttsand ej är ett lämpligt material i ett dualfilter där syftet är att förlänga filtrets livslängd.

In a scrap based stainless steel plant the dominant process for carbon reduction is the Argon oxygen decarburisation process (AOD). The process goes through three steps: decarburisation, reduction and desulphurisation where the main challenge is to oxidise carbon to CO without oxidising the expensive chromium. The general practical approach is to inject a mixture of oxygen and an inert gas, like argon or nitrogen, through tuyeres at the converter side starting with a high amount of oxygen gas which followingly is reduced as the inert gas is increased during the decarburisation steps. This allows for a decrease in partial pressure for the CO bubbles which is thermodynamically favourable for carbon oxidation. Recent studies have shown that an aged AOD converter with a worn lining can decarburise the melt faster than a fresh vessel due to favourable thermodynamic conditions occurring since the bath height is lower in the aged converter. The studies show 8-10% savings of oxygen gas which have led to an interest to study the matter. One of two approaches are taken in the present work with the focus to develop a numerical model that simulates a downscaled AOD converter with applied inclinations that is to be validated through physical modelling. A 75-ton industrial converter was downscaled for water-air experiments where three inclination angles namely 0, 5.5 and 14° were studied with focus on mixing time and penetration length. The physical model was replicated for computational fluid dynamics (CFD) modelling using the Euler-Euler approach in ANSYS Fluent. The models show rather good similarities when comparing gas penetration length, flow structure and mixing time however needs some complementary work and final adjustments before upscaling as well as coupling with thermodynamic modelling can be done. / Den dominerande processen för kolfärskning vid skrot baserad rostfri ståltillverkning är AOD- processen (Argon Oxygen Decarburisation). Processen går igenom tre steg, kolfärskning, reducering av krom och svavelrening där de största utmaningarna ligger i att oxidera kol utan att oxidera krom. I praktiken gör detta genom att injicera en blandning av argon och syrgas från sidan av AOD-konvertern för att sänka partial trycket av den kolmonoxid som bildas när kol oxideras. Syftet är att göra det mer termodynamiskt fördelaktigt att oxidera kol i systemet. Den injicerade blandgasen har olika förhållanden under kolfärskning med en hög andel syrgas i början som sedan sänks genom processen tills bara argon injiceras. Tidigare studier har visat att kolfärskningen är en funktion av konverterns ålder där ju äldre en konverter är desto snabbare går kolfärskning. Enligt studierna har det visats att 8-10% mindre syrgas eller användning av reducerings medel kan uppnås i en gammal konverter vilket har väckt ett intresse för vidare studier. I detta arbete har en av två metoder prövats för att undersöka om man kan applicera det som sker i en gammal konverter till en ny. En numerisk modell av en nerskalad AOD-konverter har utvecklats och validerats mot en vattenmodell då konvertern vinklas. En 75-tons konverter nerskalades till en vattenmodell där vinklarna 0, 5.5 och 14° studerades med fokus på blandningstid och penetrations djup. Vattenmodellen gjordes om till en numerisk modell som använde Euler-Euler metoden i ANSYS Fluent. Modellerna visade likheter gällande penetrationsdjup, flödes struktur och blandnings tid men kräver en del justeringar innan en uppskalning samt koppling till termodynamisk modellering kan ske.