<p>A production Basic Oxygen Furnace installation at Dominion Foundries and Steel Ltd., Hamilton, Ontario is used to develop a method of dynamically predicting the time during steelmaking at which a specified bathcarbon content will be reached.</p><p>The carbon evolution rate is calculated from continuous stack gas analysis and flow data. This information, combined with a known bath carbon content measured shortly before the end of the blow, is used to perform carbon mass balances. Bath carbon contents, calculated from these mass balances can be expressed as a function of time by a simple updated-mathematical model which is then used to predict the end point time.</p> <p>A new technique for determining stack gas flow rates by utilizing an injected chemical tracer is evaluated.</p> / Thesis / Master of Engineering (ME)

Ultraviolet-visible chemiluminescent emission features in laboratory-scale flames have been shown by several researchers to correlate well with the flame's equivalence ratio, and it has been suggested that this relation could be used to actively control flames. This study investigated the feasibility of extending this knowledge to the industrial setting. Radiative emissions from basic oxygen furnace (BOF) and thermal generating station burner flames were mainly characterized by thermally-induced greybody spectra; emissions from electronically excited species of OH*, OH*, and CO2* were generally weak and did not offer any unique information that could be used as part of a flame diagnostic system. A sub-study which assessed the impact of biomass cofiring demonstrated that emissions of SO2, NOx, and fossil-CO2 could be reduced with direct fuel replacement. The sensor system could be used as a pyrometer, and as part of a burner balancing strategy to counter increased CO emissions and decreased efficiency.

Ultraviolet-visible chemiluminescent emission features in laboratory-scale flames have been shown by several researchers to correlate well with the flame's equivalence ratio, and it has been suggested that this relation could be used to actively control flames. This study investigated the feasibility of extending this knowledge to the industrial setting. Radiative emissions from basic oxygen furnace (BOF) and thermal generating station burner flames were mainly characterized by thermally-induced greybody spectra; emissions from electronically excited species of OH*, OH*, and CO2* were generally weak and did not offer any unique information that could be used as part of a flame diagnostic system. A sub-study which assessed the impact of biomass cofiring demonstrated that emissions of SO2, NOx, and fossil-CO2 could be reduced with direct fuel replacement. The sensor system could be used as a pyrometer, and as part of a burner balancing strategy to counter increased CO emissions and decreased efficiency.

Phosphorus (P) is one of the essential nutrients for living organisms; however, excess P in aquatic systems often causes environmental and ecological problems including eutrophication. Removal of P from domestic wastewater, industrial wastewater, and agricultural organic-waste systems is required to minimize loading of P to receiving water bodies. A variety of sorbents or filter materials have previously been evaluated for P removal, including natural materials, industrial byproducts, and synthetic products. Among these materials industrial byproducts were reported as most effective. However, only a few of these studies were based on field experiments. Pharmaceutically active compounds (PhACs) and acesulfame-K (an artificial sweetener) are emerging contaminants observed in wastewater. The removal of PhACs in conventional wastewater treatment systems has been studied; however, few studies on alternative treatment systems are available. Studies related to the removal of acesulfame-K are even more limited. This thesis was focused on evaluation of basic oxygen furnace slag (BOFS), a byproduct from the steel manufacturing industry, as a potential reactive media for P removal from surface water and wastewater. The removal of PhACs and acesulfame-K in wastewater treatment systems containing BOFS as a treatment component was also evaluated. The effectiveness of BOFS for removing P from lake water was evaluated in a three year pilot-scale hypolimnetic withdrawal P treatment system at Lake Wilcox, Richmond Hill, Ontario. Phosphate concentrations of the hypolimnion water ranged from 0.3 to 0.5 mg L-1. About 83-100% P was removed during the experiment. The reactive mixtures were changed each year to improve the performance of the treatment system. Elevated pH (9-12) at the effluent of the treatment system was adjusted by sparging CO2(g) to near neutral pH. Elevated Al was removed through this pH adjustment. Elevated concentrations of V were removed in a column containing 5 wt% zero valent iron (ZVI) mixed with sand (0.5 m3) at the end of the BOFS based column. Removal of P in the BOFS based media is attributed to adsorption and co-precipitation at the outer layer of BOFS. Geochemical modeling results showed supersaturation with respect to hydroxyapatite, ß-tricalciumphosphate, aragonite, and calcite. Solid phase analyzes of the BOFS based reactive media collected after completion of the year 2 experiment (spent media) through combination of scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and X-ray absorption near edge structure spectroscopy (XANES) support the presence of calcium phosphate minerals on the outer layer of the spent media. A multistep wastewater treatment experiment was carried out in an indoor facility at the Center for Alternative Wastewater Treatment, Fleming College, Lindsay, Ontario, Canada. This experiment evaluated the removal of P, ammonia, cBOD5, COD, E. coli, total coliform, and trace metals in a series of treatment cells including a mixing cell, a vertical subsurface flow aerobic cell, a vertical subsurface flow P treatment cell containing BOFS, and a horizontal subsurface flow anaerobic cell. About 97-99% removal of P, NH3, cBOD5, E. coli, and total coliform; and ~72% removal of COD were achieved in the treatment system. The mixing cell and the aerated cell reduced the concentrations of P, ammonia, cBOD5, E. coli, and total coliform significantly and the P treatment cell provided additional treatment. However, the primary objective of the P treatment cell was to reduce P concentrations to the acceptable range according to the water quality guidelines. The P treatment cell had successfully fulfilled this objective. Elevated concentration of Al and V were also observed in the P treatment cell effluent. The concentration of Al decreased to below the guideline value of 0.075 mg L-1 after introducing a pH adjustment unit between the P treatment cell and the anaerobic cell. The concentration of V was decreased in the anaerobic cell effluent. However, the effluent concentration of V was much higher than the guideline value. Geochemical speciation modeling results showed supersaturation with respect to hydroxyapatite, ß-tricalciumphosphate, aragonite and calcite along the flow path. Accumulation of P on the outer layer of the spent BOFS media was identified by energy dispersive X-ray spectroscopy (EDX). Although X-ray photoelectron spectroscopy (XPS) can provide information to a depth of 5-7 nm from the outer layer of the spent media, both Ca and P were positively identified in some of the samples. Accumulation of P at the edge of the grains of the spent media was clearly identified on the element map of polished cross-sections and corresponding FTIR spectra. The phosphate and carbonate functional groups were identified by the distribution of different vibrational frequencies through FTIR spectroscopy. The presence of calcite and hydroxyapatite were inferred based on the wave numbers assigned for these minerals in the literature. Finally, X-ray absorption near edge structure spectroscopy (XANES) on the outer layer samples from the spent BOFS media and corresponding linear combination fitting analysis indicated the presence of ß-tricalciumphosphate, hydroxyapatite, and calcium phosphate dibasic. Based on the observations from the indoor wastewater treatment experiment, a multistep demonstration-scale outdoor wastewater treatment experiment was conducted to investigate the applicability of the integration of the P treatment technology and engineered wetland technology at a relatively large scale prior to a full-scale field installation. The anaerobic treatment cell was not included in this outdoor system because this unit did not efficiently remove ammonia and metals (e.g. V) from the Cell 4 effluent in the indoor system. A 10 cm layer of zero valent iron was placed at the bottom part of the down flowing P treatment cell to address the elevated V in the P treatment cell effluent observed in the indoor system and also to treat PhACs in the effluent. More than 99% removal of P, E. coli, and total coliform; >82, >98, and >76% removal of ammonia, cBOD5, and COD were achieved in this treatment system. The effluent pH (10.88±1.47) was neutralized and the concentration of V remained < 0.006 mg L-1. The Al concentration was adjusted to <0.075 mg L-1 with the neutralization of pH. Geochemical speciation modeling results showed the supersaturation of hydroxyapatite, ß-tricalciumphosphate, octatricalciumphosphate, aragonite, and calcite. The FTIR and XANES spectra showed the presence of calcium phosphate minerals on the outer layer of the spent media. Removal of the PhACs, including caffeine, ibuprofen, carbamazepine, naproxen, and sulfamethoxazole, and acesulfame-K was monitored in the demonstration-scale outdoor wastewater treatment system, which consisted of five different treatment cells including a horizontal subsurface flow constructed wetland, a vertical subsurface flow aerated cell, a vertical subsurface flow BOFS cell, and a pH neutralization unit. Significant removal of caffeine (>75%) and ibuprofen (50-75%), and moderate removal of sulfamethoxazole and naproxen (25-50%) were observed. The removal of carbamazepine was less effective with <25% removal observed. Acesulfame-K was also persistent along the flow path with <25% removal. This study demonstrated that removal of P from lake water and wastewater in excess of 95% could be achieved using BOFS as a reactive media. Integration of this media into an engineered wetland system enhances its performance in removing nutrients and other wastewater contaminants.

Phosphorus (P) is one of the essential nutrients for living organisms; however, excess P in aquatic systems often causes environmental and ecological problems including eutrophication. Removal of P from domestic wastewater, industrial wastewater, and agricultural organic-waste systems is required to minimize loading of P to receiving water bodies. A variety of sorbents or filter materials have previously been evaluated for P removal, including natural materials, industrial byproducts, and synthetic products. Among these materials industrial byproducts were reported as most effective. However, only a few of these studies were based on field experiments. Pharmaceutically active compounds (PhACs) and acesulfame-K (an artificial sweetener) are emerging contaminants observed in wastewater. The removal of PhACs in conventional wastewater treatment systems has been studied; however, few studies on alternative treatment systems are available. Studies related to the removal of acesulfame-K are even more limited. This thesis was focused on evaluation of basic oxygen furnace slag (BOFS), a byproduct from the steel manufacturing industry, as a potential reactive media for P removal from surface water and wastewater. The removal of PhACs and acesulfame-K in wastewater treatment systems containing BOFS as a treatment component was also evaluated. The effectiveness of BOFS for removing P from lake water was evaluated in a three year pilot-scale hypolimnetic withdrawal P treatment system at Lake Wilcox, Richmond Hill, Ontario. Phosphate concentrations of the hypolimnion water ranged from 0.3 to 0.5 mg L-1. About 83-100% P was removed during the experiment. The reactive mixtures were changed each year to improve the performance of the treatment system. Elevated pH (9-12) at the effluent of the treatment system was adjusted by sparging CO2(g) to near neutral pH. Elevated Al was removed through this pH adjustment. Elevated concentrations of V were removed in a column containing 5 wt% zero valent iron (ZVI) mixed with sand (0.5 m3) at the end of the BOFS based column. Removal of P in the BOFS based media is attributed to adsorption and co-precipitation at the outer layer of BOFS. Geochemical modeling results showed supersaturation with respect to hydroxyapatite, ß-tricalciumphosphate, aragonite, and calcite. Solid phase analyzes of the BOFS based reactive media collected after completion of the year 2 experiment (spent media) through combination of scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and X-ray absorption near edge structure spectroscopy (XANES) support the presence of calcium phosphate minerals on the outer layer of the spent media. A multistep wastewater treatment experiment was carried out in an indoor facility at the Center for Alternative Wastewater Treatment, Fleming College, Lindsay, Ontario, Canada. This experiment evaluated the removal of P, ammonia, cBOD5, COD, E. coli, total coliform, and trace metals in a series of treatment cells including a mixing cell, a vertical subsurface flow aerobic cell, a vertical subsurface flow P treatment cell containing BOFS, and a horizontal subsurface flow anaerobic cell. About 97-99% removal of P, NH3, cBOD5, E. coli, and total coliform; and ~72% removal of COD were achieved in the treatment system. The mixing cell and the aerated cell reduced the concentrations of P, ammonia, cBOD5, E. coli, and total coliform significantly and the P treatment cell provided additional treatment. However, the primary objective of the P treatment cell was to reduce P concentrations to the acceptable range according to the water quality guidelines. The P treatment cell had successfully fulfilled this objective. Elevated concentration of Al and V were also observed in the P treatment cell effluent. The concentration of Al decreased to below the guideline value of 0.075 mg L-1 after introducing a pH adjustment unit between the P treatment cell and the anaerobic cell. The concentration of V was decreased in the anaerobic cell effluent. However, the effluent concentration of V was much higher than the guideline value. Geochemical speciation modeling results showed supersaturation with respect to hydroxyapatite, ß-tricalciumphosphate, aragonite and calcite along the flow path. Accumulation of P on the outer layer of the spent BOFS media was identified by energy dispersive X-ray spectroscopy (EDX). Although X-ray photoelectron spectroscopy (XPS) can provide information to a depth of 5-7 nm from the outer layer of the spent media, both Ca and P were positively identified in some of the samples. Accumulation of P at the edge of the grains of the spent media was clearly identified on the element map of polished cross-sections and corresponding FTIR spectra. The phosphate and carbonate functional groups were identified by the distribution of different vibrational frequencies through FTIR spectroscopy. The presence of calcite and hydroxyapatite were inferred based on the wave numbers assigned for these minerals in the literature. Finally, X-ray absorption near edge structure spectroscopy (XANES) on the outer layer samples from the spent BOFS media and corresponding linear combination fitting analysis indicated the presence of ß-tricalciumphosphate, hydroxyapatite, and calcium phosphate dibasic. Based on the observations from the indoor wastewater treatment experiment, a multistep demonstration-scale outdoor wastewater treatment experiment was conducted to investigate the applicability of the integration of the P treatment technology and engineered wetland technology at a relatively large scale prior to a full-scale field installation. The anaerobic treatment cell was not included in this outdoor system because this unit did not efficiently remove ammonia and metals (e.g. V) from the Cell 4 effluent in the indoor system. A 10 cm layer of zero valent iron was placed at the bottom part of the down flowing P treatment cell to address the elevated V in the P treatment cell effluent observed in the indoor system and also to treat PhACs in the effluent. More than 99% removal of P, E. coli, and total coliform; >82, >98, and >76% removal of ammonia, cBOD5, and COD were achieved in this treatment system. The effluent pH (10.88±1.47) was neutralized and the concentration of V remained < 0.006 mg L-1. The Al concentration was adjusted to <0.075 mg L-1 with the neutralization of pH. Geochemical speciation modeling results showed the supersaturation of hydroxyapatite, ß-tricalciumphosphate, octatricalciumphosphate, aragonite, and calcite. The FTIR and XANES spectra showed the presence of calcium phosphate minerals on the outer layer of the spent media. Removal of the PhACs, including caffeine, ibuprofen, carbamazepine, naproxen, and sulfamethoxazole, and acesulfame-K was monitored in the demonstration-scale outdoor wastewater treatment system, which consisted of five different treatment cells including a horizontal subsurface flow constructed wetland, a vertical subsurface flow aerated cell, a vertical subsurface flow BOFS cell, and a pH neutralization unit. Significant removal of caffeine (>75%) and ibuprofen (50-75%), and moderate removal of sulfamethoxazole and naproxen (25-50%) were observed. The removal of carbamazepine was less effective with <25% removal observed. Acesulfame-K was also persistent along the flow path with <25% removal. This study demonstrated that removal of P from lake water and wastewater in excess of 95% could be achieved using BOFS as a reactive media. Integration of this media into an engineered wetland system enhances its performance in removing nutrients and other wastewater contaminants.

Dans le domaine sidérurgique, l'ajustement des commandes de préréglage est un problème courant. L'objectif des systèmes de commande est d'obtenir des produits de qualité imposée. On observe cependant fréquemment des variations de comportement d'un lot à l'autre, ce qui nécessite de modifier les paramètres des modèles employés pour les préréglages suivants. Cela est particulièrement vrai pour le convertisseur à oxygène où les informations rassemblées pendant une coulée spécifique servent à ajuster les points de consigne de la coulée suivante.Dans cette thèse, nous présentons une méthode de validation de données s'appuyant sur un modèle incertain. Les incertitudes portant sur les mesures des variables et sur la connaissance des paramètres du modèle sont simultanément prises en compte pour fournir des estimées cohérentes qui pourront être mises à profit par le système de contrôle-commande du convertisseur à oxygène. L'estimation paramétrique étant sensible à la présence de mesures aberrantes , la méthode proposée a été rendue robuste à la présence de ces informations erronées par la prise en compte, dans la méthode d'estimation, de la notion de distribution statistique contaminée.Le modèle du convertisseur a été établi sur la base des principes de conservation de masse et d'énergie, mais aussi sur des relations d'équilibre chimique pour lesquelles certains paramètres sont assez mal connus ce qui justifie pleinement l'approche utilisée. Les estimations des variables et des paramètres fournissent une image plus juste de l'état réel du système ce qui en facilite la conduite. Appliquée au convertisseur à oxygène, cette méthode permet l'actualisation du modèle de calcul de charge utile au préréglage. De plus, le suivi de l'évolution de certains paramètres du modèle permet d'évaluer un niveau de dégradation du système (par exemple, l'endommagement du réfractaire de la poche / In the steel industry, tuning the control system set-points in order to reach given product specification is a common problem. The control system objective is to obtain products satisfying the given specifications. There are however frequent changes in the behavior from one batch to another, thus requiring the modification of model parameters used for the following presets. This is particularly true for the Basic Oxygen Furnace (BOF) where the information collected during a specific batch serves to adjust the set-points of the next batch.In this thesis, we proposed a method allowing simultaneously robust data reconciliation and model parameter estimation. This approach is original because the current data validation methods make the assumption that the system model is known perfectly. Here, the uncertainties on the measurements of variables and on the knowledge of the model parameters are simultaneously taken into account to provide consistent estimates that can be utilized by the control system of the BOF, especially for the determination of the set-points. Parameter estimation being sensitive to the presence of outliers, which is common in this type of process operating in highly disturbed environment, the proposed method has been made robust to the presence of these errors by including in the estimation method, the notion of contaminated statistical distribution.The model of the converter was based on the principles of mass and energy conservation, but also on chemical equilibrium relationships for which some parameters are not well known that fully justifies the proposed approach. The variable and parameter estimates provide a more accurate picture of the actual state of the system which facilitates its control. Applied to the BOF, this method allows the updating of the model used for the preset. In addition, monitoring the evolution of some model parameters can be used to evaluate the degradation level of the system (eg, damage to the refractory of the converter)

Abstract The target in this thesis was to study selected special measurements in a basic oxygen furnace (BOF) and develop a model to predict the steel temperature at the end of the oxygen blow. Furthermore, the work aimed at increasing knowledge on measurements and phenomena in the converter and in this way improve the possibility of more efficient monitoring and control of the process. Special measurements were investigated to obtain more knowledge about their usability in running the converter process. Analysing the measurement results also led to new process knowledge. The usage of a Radio Wave Interferometer (RWI) was seen as beneficial as it makes it possible to see the rising trend of the liquid surface level in advance and to perform some corrective actions to avoid excessive foaming and possible splashing out from the converter. Acoustic measurement could also detect trends in advance, but it was found to be sensitive to disturbing noise from the surroundings. Splashing measurement gives information about the current state of the slag but not advance information. Nevertheless, the measurements revealed several factors that usually increase splashing. It would be best to use the knowledge from two different measurements, for example RWI and splashing measurement, to predict increasing splashing, which causes significant iron losses. The development of the models for end temperature prediction and additional materials provided a lot of knowledge about the factors affecting the temperature. Factors that were used in grouping were the BOF number, heat size and end carbon content. However, there were many heats that did not satisfy the target. Furthermore, there is a need for additional research into temperature progress and its control in BOF. It would also be useful to study the effect of additional materials more systematically. There are other factors, such as the oxygen flow rate and lance height, which affect the temperature that are not included in the models. Some of the factors are measurable and some are not. There is still a need for more research in this area. This work strengthens the impression that the converter process is a complex one. It was noticed; as always in process development, that continuous monitoring and efforts are required to observe the changes in process conditions, raw materials or running practices. Otherwise, the benefit of the improvements and models will be lessened. However, it would be possible to set acknowledged routines and warnings into the improved monitoring system to help the operators notice the need for system tuning. A monitoring system would provide financial benefits in terms of having fewer reblowings, better yield and better quality of final product. Savings in raw materials can also be attained as the controllability of the process becomes better. As the monitoring system contains a database of guidelines, it would form a good basis for new employees to become familiar with the process and thus facilitate their training. / Tiivistelmä Tämän opinnäytteen tarkoitus oli tutkia teräskonvertterin valittuja erikoismittauksia ja kehittää malli ennustamaan teräksen lämpötilaa happipuhalluksen lopussa. Työn tarkoituksena oli lisätä tietämystä mittauksista ja ilmiöistä konvertterissa ja tällä tapaa lisätä mahdollisuuksia prosessin tehokkaampaan monitorointiin ja ohjaukseen. Erikoismittauksia tutkittiin lisätietämyksen saamiseksi niiden käytettävyydestä konvertteriprosessin ajossa. Mittausten analysointi tuotti myös uutta prosessitietämystä. Radioaaltointerferometrin (RWI) käyttö koettiin hyödylliseksi, koska on mahdollista havaita kuonan pinnankorkeuden nousu ennakkoon ja suorittaa joitakin korjaavia toimenpiteitä liiallisen kuohumisen ja lopulta roiskumisen estämiseksi ulos konvertterista. Äänimittaus voi myös havaita trendin ennakkoon, mutta huomattiin sen olevan herkkä ympäristön häiriöäänille. Roiskemittaus antaa tietoa kuonan sen hetkisestä tilasta, mutta ei ennakkoon. Mittaukset toivat kuitenkin esiin useita tekijöitä, jotka yleensä lisäävät roiskumista. Olisi parasta käyttää kahden eri mittauksen tietoa, RWI ja roiskemittaus, ennustettaessa lisääntyvää roiskumista, joka aiheuttaa huomattavia rautahäviöitä. Loppulämpötilan ennustamiseen kehitetyn mallin ja lisäainemallin kehittäminen antoi paljon tietoa tekijöistä, jotka vaikuttavat lämpötilaan. Tekijät, joita käytettiin ryhmittelyssä, olivat konvertterinumero, panoskoko ja loppuhiilipitoisuus. Mallin soveltamisesta huolimatta jäi edelleen useita sulatuksia, jotka eivät osuneet tavoitteeseen. On edelleen tarve teräskonvertterin lämpötilakäyttäytymisen ja sen hallinnan lisätutkimukselle konvertterissa. Myös lisäaineiden vaikutusta lämpötilaan olisi hyödyllistä tutkia systemaattisemmin. On edelleen muita tekijöitä, esimerkiksi hapen virtausnopeus ja lanssin korkeus, jotka vaikuttavat lämpötilaan, mutta jotka eivät ole mukana malleissa. Osa näistä tekijöistä on mitattavia suureita ja osa ei. Lisätutkimukselle on edelleen tilaa tällä alueella. Tämä työ vahvistaa edelleen käsitystä, että konvertteriprosessi on monimutkainen. Huomattiin, kuten aina prosessikehityksessä, että jatkuvaa kehitystyötä pitää tehdä prosessiolosuhteiden, raaka-aineiden ja ajopraktiikoiden muutosten huomaamiseksi. Muuten parannusten ja mallien antama hyöty heikkenee. Monitorointijärjestelmään olisi mahdollista kehittää rutiineja ja varoituksia operaattorien avuksi, jotta he huomaisivat järjestelmävirityksen tarpeen. Monitorointijärjestelmä toisi taloudellista hyötyä, mm. lisäpuhallusten vähentymisen, lopputuotteen paremman saannon ja laadun muodossa. Raaka-ainesäästöjä voidaan saavuttaa prosessin ohjattavuuden parantuessa. Monitorointijärjestelmän sisältäessä sääntötietokannan, se luo hyvän pohjan uusille työntekijöille tutustua prosessiin ja näin heidän koulutuksensa onnistuisi helpommin.

Le présent manuscrit de thèse présente l'étude de différents phénomènes dans un convertisseur d?acier, grâce au développement de deux modèles distincts. Le premier modèle décrit la cavité produite à la surface libre du bain de métal par l'impact du jet d'oxygène supersonique. Il est basé sur le découpage du domaine de calcul en deux régions. Les effets de compressibilité du gaz sont pris en compte uniquement dans la région du jet où la vitesse est élevée, alors que partout ailleurs, le gaz est considéré comme incompressible. La méthode Volume Of Fluid (VOF) est utilisée pour suivre la déformation de la surface libre du bain. Les résultats de simulations sont présentés pour des systèmes bi- et triphasés et comparés à des données expérimentales obtenues dans diverses maquettes froides. L'influence sur la taille et la forme de la cavité de différents paramètres (parmi lesquels les conditions aux limites en sortie de la lance d'injection, le schéma d'advection de la méthode VOF et le modèle de turbulence) est étudiée. Le modèle est ensuite utilisé pour simuler l'interaction entre un jet supersonique d'oxygène et la surface libre d'un bain d'acier liquide dans un convertisseur de taille pilote. Le second modèle se focalise sur l'écoulement du gaz, le transfert de chaleur et la réaction de postcombustion dans la phase gazeuse au-dessus du bain de métal. Il utilise l'algorithme Simple Chemical Reaction Scheme pour décrire le transport des espèces chimiques, et prend en compte l'absorption d'oxygène dans le bain et les transferts thermiques par rayonnement. Les prédictions numériques sont en assez bon accord avec les mesures recueillies dans une expérience de laboratoire et dans un four à l'échelle pilote / The present thesis treats different phenomena taking place in a steelmaking converter through the development of two separate models. The first model describes the cavity produced at the free surface of the metal bath by the high speed impinging oxygen jet. It is based on a zonal approach, where gas compressibility effects are taken into account only in the high velocity jet region while elsewhere the gas is treated as incompressible. The Volume Of Fluid (VOF) method is employed to follow the deformation of the bath free surface. Calculations are presented for two- and three-phase systems and compared against experimental data obtained in various cold model experiments. The influence on the size and shape of the cavity of various parameters (including the jet inlet boundary conditions, the VOF advection scheme and the turbulence modelling) is studied. Next, the model is used to simulate the interaction of a supersonic oxygen jet with the surface of a liquid steel bath in a pilot-scale converter. The second model concentrates on fluid flow, heat transfer and the post-combustion reaction in the gas phase above the metal bath. It uses the Simple Chemical Reaction Scheme approach to describe the transport of the chemical species and takes into account the consumption of oxygen by the bath and thermal radiative transfer. The numerical predictions are in reasonable agreement with measurements collected in a laboratory experiment and in a pilot-scale furnace

A novel technique for measuring gas temperature and spectral particle emissivity in high-temperature gas-particle streams is presented. The main application of this optical sensor is to improve the process control of batch unit operations, such as steelmaking furnaces. The spectral emission profile of CO and CO2 and the continuous particle emission in the 3.5 to 5 μm wavelength region was recorded and analyzed in real time with a low-resolution passive sensor. The sensor consisted of light collecting optics, a dispersion element (grating spectrometer) and a 64-pixel pyroelectric array. Wavelength and radiance calibrations were performed. The temperature of the gas-particle medium (Tg+p) followed from the least-squares minimization of the difference between the measured radiance in the 4.56-4.7 μm region –which saturates due to the large CO2 concentrations and path lengths in industrial furnaces– and the corresponding blackbody radiance. Particle emissivity (εp) was calculated at 3.95 μm from an asymptotic approximation of the Radiative Transfer Equation that yields the emerging radiance from a semi-infinite particle cloud. The major source of error in the magnitude of Tg+p and εp could come from particle scattering. Through the method of embedded invariance an expression was developed to estimate the lowering effect of particle size and volume fraction on the saturation of the 4.56-4.7 μm CO2 emission region. An iterative procedure for correcting the values of the gas-particle temperature and particle emissivity was applied to the datasets from the two industrial tests. Results from the measurement campaigns with the infrared sensor prototype at two full-scale furnaces are presented. A proof-of-concept test at a coal-fired boiler for electricity production was followed by more extensive measurements at a Basic Oxygen Furnace (BOF) for steelmaking. The second test provided temperature and particle emissivity profiles for eight heats, which highlighted the simplicity of the technique in obtaining in-situ measurements for modeling studies. Through the analysis of the particle emissivity profile in the BOF and the definition of a new variable –the minimum carbon time– a novel end-point strategy to stop the injection of high-purity oxygen during low-carbon heats in BOF converters was proposed.

A novel technique for measuring gas temperature and spectral particle emissivity in high-temperature gas-particle streams is presented. The main application of this optical sensor is to improve the process control of batch unit operations, such as steelmaking furnaces. The spectral emission profile of CO and CO2 and the continuous particle emission in the 3.5 to 5 μm wavelength region was recorded and analyzed in real time with a low-resolution passive sensor. The sensor consisted of light collecting optics, a dispersion element (grating spectrometer) and a 64-pixel pyroelectric array. Wavelength and radiance calibrations were performed. The temperature of the gas-particle medium (Tg+p) followed from the least-squares minimization of the difference between the measured radiance in the 4.56-4.7 μm region –which saturates due to the large CO2 concentrations and path lengths in industrial furnaces– and the corresponding blackbody radiance. Particle emissivity (εp) was calculated at 3.95 μm from an asymptotic approximation of the Radiative Transfer Equation that yields the emerging radiance from a semi-infinite particle cloud. The major source of error in the magnitude of Tg+p and εp could come from particle scattering. Through the method of embedded invariance an expression was developed to estimate the lowering effect of particle size and volume fraction on the saturation of the 4.56-4.7 μm CO2 emission region. An iterative procedure for correcting the values of the gas-particle temperature and particle emissivity was applied to the datasets from the two industrial tests. Results from the measurement campaigns with the infrared sensor prototype at two full-scale furnaces are presented. A proof-of-concept test at a coal-fired boiler for electricity production was followed by more extensive measurements at a Basic Oxygen Furnace (BOF) for steelmaking. The second test provided temperature and particle emissivity profiles for eight heats, which highlighted the simplicity of the technique in obtaining in-situ measurements for modeling studies. Through the analysis of the particle emissivity profile in the BOF and the definition of a new variable –the minimum carbon time– a novel end-point strategy to stop the injection of high-purity oxygen during low-carbon heats in BOF converters was proposed.