Dissertations / Theses on the topic 'Coke'

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
A Indústria siderúrgica, visando contribuir com a minimização das emissões de CO2, têm promovido o estudo de vários materiais carbonosos, um deles sen-do a alternativa relacionada à utilização do carvão vegetal como fonte renovável. O objetivo principal desse trabalho foi medir, em escala de laboratório, a reativi-dade ao CO2 dos materiais carbonosos, em particular o uso do carvão vegetal em comparação com o mineral, o coque metalúrgico e o coque verde de petró-leo, utilizando para tal o método de perda de peso (ASTM D5341-99). O proces-so se realizou usando briquetes de cada material, previamente cominuido a um tamanho de partícula menor que 125 m, levados a um forno tubular a uma tem-peratura de trabalho de 1100 garus Celsius, com injeção de N2 para manter uma atmosfera inerte apenas no inicio e no final dos ensaios, sob um fluxo de 0,6 Nl/min, visan-do as etapas de aquecimento e resfriamento. Utilizando como agente oxidante o CO2 durante 2h, com um fluxo de 0,9 Nl/min, todos os tipos de briquetes foram tratados na temperatura do ensaio (1100 graus Celsius). Os resultados obtidos mostraram que o carvão vegetal foi o que apresentou maior reatividade e o coque verde de petróleo a menor, entre todos os materiais ensaiados, tanto para os briquetes não desvolatilizados como desvolatilizados. Quanto ao carvão mineral e o coque, eles situaram suas reatividades intermediariamente, ficando o carvão mineral com maiores valores de reatividade do que o coque, tanto no estado desvolatilizado como no não desvolatilizado.
The steel industry contributes to the minimization of emissions of CO2 promoting the study of carbonaceous materials, one of them being the charcoal, a renewable source. The main objective of this study was to measure, in a laboratory scale, selected carbonaceous materials reactivity for CO2. To perform it, charcoal was elected to be compared with coal, metallurgical coke and green petroleum coke (pet coke). The quantitative results were obtained by the method of weight loss (ASTM D5341-99). The procedure was carried out using briquettes of each material, previously grinded to a particle size smaller than 125 m, and fed to a tubular furnace at a temperature of 1100 degrees Celsius , using a N2 injection, with a stream of 0.6 Nl/min, to insure an inert atmosphere only during heating and cooling steps of the experiments. To perform the reactivity tests, CO2 was used as the species to react with the C element present at the samples composition. The tests took 2 hours, with a CO2 flow rate of 0.9 Nl/min, in a temperature of 1100 degrees Celsius. According to the results obtained, it was found that the charcoal has the higher reactivity and the green petroleum coke the less reactive. For the metallurgical coke and coal, their reactivities were intermediary between charcoal and green pet coke, being coal more reactive than coke for both, volatilized and non-volatilized samples.

The carbon in metallurgical coke is composed of textural units, varying in size and shape depending on the rank of coal carbonized. These induce a characteristic texture to coke surfaces. This thesis describes a study of the bearing of this texture on coke strength, particular emphasis being placed on investigating the feasibility of using textural composition data, determined by either scanning electron microscopy (SEX) of etched surfaces or polarized-light microscopy (PLX) of polished coke surfaces, as a basis of predicting the tensile strength of cokes produced from blended-coal charges from the behaviour of individual blend components. Scanning electron microscopy (SEM) of fractured coke surfaces revealed differences in the mode of fracture of textural components which implied variations in their contribution to coke strength. The tensile strengths of pilot-oven cokes, produced from blended-coal charges, could be related to their measured PLM textural compositions using equations derived from consideration of simple models of intergranular and transgranular fracture. The coke strengths could also be related, with greater precision, with textural data calculated from the coal blend composition and either the SEM or the PLM textural data for the cokes from the individual blend components. It was further found that the strength of blended-coal cokes were additively related to the blend composition and the tensile strengths of the single-coal cokes. Such relationships are useful, at the very least, for predicting the strength of cokes from other blends of the same coals carbonized under similar conditions. The various approaches to coke strength prediction have potential value in different situations.

Metallurgical coke is used primarily as a reducing agent for the reduction of iron in the blast furnace. Due to the high cost, high demand and reduced availability of high quality coking coals used in the production of metallurgical coke, alternative resources are being sought. One possible alternative is to use petroleum coke. Petroleum coke has the advantage of having a higher calorific value than traditional coke, at relatively low cost with a low ash content and ready availability. However the drawback to petroleum coke relates to its poor mechanical strength and reactivity. The main focus of this study was therefore to develop a process for producing petroleum coke with the required qualities for blast furnace application. In an initial series of experiments tests including proximate analysis, ultimate analysis, intrinsic reactivity test, DSC, direct tensile strength, calorific value, X-ray computed tomography, X-ray diffraction and scanning electron microscopy were used to characterise a wide range of petroleum coke and compare it with metallurgical coke properties. X-ray computed tomography methodology was also used to provide 3D information on coke lumps. Results show that none of the petroleum coke samples met the full requirements needed for use as a good blast furnace coke.

In recent years, the consequences of global warming have increased the discussion about the climate impact caused by humans and the fossil emissions. Sweden has decided to reduce the negative climate impact with a zero vision for the fossil carbon dioxide emissions in year 2045. In order to achieve this, great efforts and changes are needed both in the inhabitants' way of living but primarily in the base industry. The major cause is the use of fossil coal, which generates fossil carbon dioxide in the steel industry in particular. The fossil coal is added to the blast furnace in the steel process in forms of coke and coal, which reduces the iron and emits heat. The quality of the coke is important as it functions reducing agent, provides a mechanical support to the bed and enables the gas flow up through the blast furnace and enables dissolution of carbon in hot metal. Also, coke supplies energy from exothermic reactions between carbon and carbon dioxide that takes part in the blast furnace and the energy are further used for the heating and melting of the cold iron pellets. Due to these factors, the blast furnace process is dependent on coke for its function, which means that the entire process must be replaced if the steel production should work without fossil coal. However, there are many studies that have been done on how to replace some of the fossil coal with bio-coal, which is produced from biomass. If some of the fossil coal could be replaced by some bio-coal, this would mean that fossil carbon dioxide emissions would decrease and lead to a reduced climate impact. The process would still generate carbon dioxide, but on the other hand, a cycle would be formed because when biomass is grown, carbon dioxide is taken up, e.g. by the trees grown for this purpose. However, bio-coal does not have the same properties as fossil coal, which in turn affects the quality of the coke. Bio-coke is more reactive and more porous than fossil coke. In order to be able to replace fossil coke with bio-coke, it is likely necessary to pre-treat the biocoal before it replaces part of the fossil coal in the coke production. Bio-coal contains ash that acts as an internal catalyst. One theory is that if it is possible to produce a bio-coal with ash-free carbon structure, it can be used in the production of coke without having such a great effect on the coke quality. In this project, the ash's impact on the properties of bio-coal in coke was studied. Previous studies have shown that leaching is an effective method for removing ash from bio-coal. It can be leached in three different ways, either with water, weak acid or acid. However, it has been found that acid leaching has a certain impact on the carbon structure itself. For this reason, two types of bio-coal, torrefied Grot (forest residue) and torrefied sawdust were selected, which were leached both with water but also with weak acid in order to achieve an ash-reduced carbon structure. The acid selected was acetic acid, as it has been tested for similar purposes in previous studies. The leaching efficiency was evaluated by analysing the leachate with ICP-OES after leaching. According to the result, a significant part of the ash had been leached out, but the leaching with weak acid was much more effective than water leaching. To ensure that the carbon structure was not altered, light-optical microscopy was made which showed that the structure was intact. However, it was not possible to determine whether the pore sizes were changed after leaching and it is therefore relevant to investigate this further. Moreover, the leached II bio-coal replaced 5% of the fossil coal in the coal mixture for coke making. In addition to this, coke was also made with only the ash from the two bio-coals to see what effect the ash has on the coke quality. The result that was obtained from the TGA showed that the ash had a low impact on the reactivity of the coke. However, the coal structure of the coke had a great impact on the reactivity behaviour. Keywords: Bio-coke, bio-coal, leaching, ash, coke quality, carbon structures, torrefied sawdust

La production mondiale d’aluminium, produit via le procédé Hall Héroult, est actuellement autour de 60000 tonnes annuellement. Ce procédé a principalement conservé le concept original développé en 1886. Les anodes de carbone précuites utlisées dans ce procédé représentent une part importante du design des cellules d’électrolyse de l’aluminium. Les anodes font partie de la réaction chimique de la réduction de l’alumine et sont consommées lors du processus d’électrolyse. De ce fait, le niveau de consommation et la qualité des anodes ont un effet direct sur la performance des alumineries dans le marché extrêmement compétitif de la production d’aluminium. Bien que le processus et le design des anodes datent de 130 ans, l’effet des propriétés des matières premières sur la qualité finale des anodes n’est pas tout à fait maîtrisé, nécessitant ainsi des recherches approfondies. Les anodes de carbone sont composées de particules de coke, de pitch et de mégots d’anodes. Le pitch à la température de mélange et de formage est un liquide. Par conséquent, le mélange est une pâte de coke et des agrégats de mégots et pitch agissant comme liant. Le comportement de l'écoulement et du compactage de ce mélange en raison de la coexistence d'une variété de paramètres physiques, chimiques et mécaniques sont des phénomènes complexes. Compte tenu de l'importance des anodes de haute qualité et de longue durée en performance et donc l'économie des cellules de réduction, sous-estimer et prédire les propriétés finales des anodes sont très importantes pour les fonderies. La modélisation numérique dans des problèmes aussi complexes peut fournir un laboratoire virtuel où les effets de différents paramètres de processus ou des matériaux sur la qualité de l'anode peuvent être étudiés sans risquer la performance du pot. Toutefois, le choix de la méthode numérique est une décision critique qui doit être prise en fonction de la physique du problème et de l'échelle géométrique des problèmes étudiés. La méthode des éléments discrets (DEM) est utilisée dans ce travail de recherche pour modéliser les deux phases de la pâte d’anode; les agrégats de coke et le brai de pétrole. Dans cette partie du travail, les modèles DEM d’agrégats de coke sont utilisés pour simuler les tests de densité en vrac vibrée des particules de coke et pour révéler les paramètres impliqués. De par sa nature, la DEM est idéale pour étudier les contacts entre particules. Les résultats de ces travaux seront ensuite utilisés pour proposer de nouvelles recettes d’agrégats secs avec une densité en vrac supérieure. La résistivité électrique de lits de particules a été mesurée expérimentalement. Les informations sur les contacts entre particules obtenues à partir des modèles numériques ont été utilisées pour expliquer la résistivité électrique de lits de particules avec différentes distribution de tailles de particules. Les résultats ont montré que lorsque le nombre de contacts par unité de volume augmente dans un échantillon, la résistivité électrique augmente aussi. La densité compactée du lit de particules a aussi une influence sur le passage de courant dans les matériaux granulaires. D’après les résultats obtenus, conserver la densité de contacts aussi basse que possible est bénéfique pour la conductivité électrique s’il n’a pas d’impact négatif sur la densité compactée. Le brai de houille est un matériau viscoélastique à température élevée. Dans ce travail, les propriétés rhéologiques du brai et de la matrice liante (brai + particules fines de coke) ont été mesurées expérimentalement en utilisant un rhéomètre à cisaillement dynamique à 135, 140 145 et 150 °C. Le modèle de Burger à quatre éléments est alors utilisé pour modéliser le comportement mécanique du brai à 150 °C. Le modèle vérifié est alors utilisé pour étudier les propriétés rhéologiques du brai et du mélange coke /brai à 150 °C. Le modèle de Burger calibré démontre une bonne prédiction des propriétés viscoélastiques du brai et de la matrice liante à différentes températures. Les résultats obtenus montrent que, considérant la physique du problème, la méthode des éléments distincts est une technique de simulation numérique adaptée pour étudier les effets des matières premières sur les propriétés mécaniques et physiques des mélanges coke /brai.
Global aluminum production now is around 60 000 metric tonnes, annually, which is produced by the Hall-Héroult process. The process has mostly kept the original concept developed in 1886. Pre-baked carbon anodes are an important part of the design of aluminum smelting cells. Anodes are part of the chemical reaction of alumina reduction and are consumed during the process. Thus, quality and properties of anodes have direct effects on the performance and economy of the aluminum production in today’s highly competitive market. Although the design of anodes goes back to 130 years ago, effects of raw materials properties on final quality of anodes still need to be investigated. Anodes are composed of granulated calcined coke, binder pitch and recycled anode butts. Pitch at temperatures of mixing and forming steps is a liquid. Hence the mixture is a paste of coke and butts aggregates with pitch acting as binder. Flow and compaction behavior of this mixture, because of the co-existence of a variety of physical, chemical and mechanical parameters are complicated phenomena. Given the importance of high quality and long lasting anodes in performance and so the economy of the reduction cells, understating and predicting the final properties of anodes are very important for smelters. Numerical modeling in such complicated problems can provide a virtual laboratory where effects of different materials or process parameters on anode quality index can be studied without risking the pot performance. However, the choice of the numerical framework is a critical decision which needs to be taken according to the physics of the problem and the geometrical scale of the investigated problems. Discrete Element Method (DEM) is used in this research work to model the anode paste. In the first step, DEM models of coke aggregates are used to simulate the vibrated bulk density test of coke particles and to reveal the parameters involved. As a micromechanical model, DEM provides a unique opportunity to investigate the particle-particle contacts. The developed DEM models of coke aggregates were then used to propose a new dry aggregates recipe exhibiting higher packing density. Packing density of coke aggregates has direct effect on the baked density of anodes. High density is a very favorable anode quality index as it has positive effects on mechanical strength, and consumption rate of anodes in the cell. Electrical resistivity of bed of particles was experimentally measured. Particle-particle contacts information obtained from numerical models were used to explain the electrical resistivity of samples with different size distribution. Results showed that the increase in the number of contacts in volume unit of a sample increases, the electrical resistivity of the particle bed. Packing density also influences the electrical current transfer in granular systems. According to the obtained results, keeping the contacts density as low as possible is beneficial for electrical conductivity if it does not have a negative effect on packing density. Pitch is a viscoelastic material at elevated temperatures. In the present work, rheological properties of pitch and binder matrix (pitch+fine coke particles) were experimentally measured using a dynamic shear rheometer at 135, 140, 145 and 150 ºC. Four-element Burger’s model is then used to model the mechanical behavior of pitch and binder matrix. The verified model is then used to investigate the rheological properties of pitch and coke/pitch mixtures at 150 ºC. Calibrated Burger’s model showed to have a good prediction of viscoelastic properties of pitch and binder matrix at different temperatures. Obtained numerical results showed that available empirical equations in the literature fail to predict the complex modulus of mixtures of pitch and coke particles. As pitch has viscoelastic response and coke particles have irregular shapes, rheology of this mixture is more complicated and needs well-tailored mathematical models. Complex modulus of pitch decreases by increasing the temperature from 135 to 150 ºC, this makes easier the coke/pitch mixtures to flow. DEM modeling showed that the mixture gets a better compaction and so lower porosity by vibro-compacting at higher temperatures. The ability of pitch to penetrate to inter-particle voids in the porous structure of bed of coke particles was also shown to be improved by temperature. Final anode structure with less porosity and so high density is favorable for its mechanical strength as well as its chemical reaction in the cell as Based on the obtained results and considering the physics of the problem, it can be said that discrete element method is an appropriate numerical simulation technique to study the effects of raw materials and the anode paste formulation on mechanical and physical properties of coke/pitch mixtures. The platform created in the course of this research effort, provides a unique opportunity to study a variety of parameters such as size distribution, shape and content of coke particles, content and rheological properties of pitch on densification of coke/pitch mixtures in vibro-compaction process. Outputs of this thesis provide a better understanding of complicated response of anode paste in the forming process.

Notre travail sur la cuisson électrique du coke moule propose par Usinor, répond par l'expérience et le calcul aux préoccupations d'homogénéité de la cuisson, d'une part au sein du boulet, d'autre part au sein d'un lit. Nous avons mesuré la variation avec la température de la résistivité des boulets choisis pour constituer la charge. Le départ des matières volatiles entraine une chute brutale et très prononcée de la résistivité entre 500 et 800c. Le contact entre boulets introduit une résistance élevée associée à la constriction des lignes de courant. Cette résistance est proportionnelle à la résistivité et inversement proportionnelle à la force appliquée. Nous avons donc mesure à la température ambiante et en fonction de la force appliquée cette résistance de constriction entre les boulets. Cette résistance qui forme 70 à 90% de la résistance totale, est très concentrée au voisinage du contact et peut faire craindre une hétérogénéité de cuisson au sein du boulet. Un calcul par éléments finis, à mailles très fines dans la zone de contact, ne fait apparaitre qu'un faible écart de température entre le contact et le point de la paroi le plus éloigné. Nous avons enfin simule numériquement la cuisson électrique de la charge. Les résultats montrent que la géométrie verticale du four conduit à un évasement des lignes de courant en dehors de la zone des électrodes, d'où résulte une surchauffe des parois par rapport à l'axe. Devant les difficultés rencontrées avec le procédé "par conduction", la société Usinor a préféré s'orienter vers un procédé "par induction

La relation entre la structure des charbons a coke et la chaleur des reactions de pyrolyse et de carbonisation a ete etudiee par analyse thermique differentielle (ATD) couplee avec analyse infrarouge par transformee de Fourier (FTIR). Des charbons frais et oxydes a divers degres ont ete analyses avec une procedure specifique limitant un biais lies au gonflement et au retrait des charbons pendant Ie chaulfage. Ces mesures ont montre que, pour tous les charbons etudies, Ie flux de chaleur est endothermique au debut de la pyrolyse et puis il devient plus ou moins exothermique avec I'augmentation de la temperature et de I'avancement de la carbonisation. Dans les charbons oxydes, I'elfet exothermique diminue fortement avec I'augmentation du degre d'oxydation. En reliant les resultats de I'analyse thermique differentielle, de I'analyse des gaz produits ainsi que de I'evolution de la structure de charbons « frais » et oxydes, on montre que I'evolution du flux de chaleur pendant Ie chaulfage resulte du bilan instantane de la chaleur des reactions de desoxydation - plutot endothermiques et des reactions de deshydrogenation - plutot exothermiques. La formation d'eau apparalt comme une reaction endothermique dont I'impact sur la chaleur de reaction se fait sentir particuiierement pendant la pyrolyse des charbons oxydes. En elfet, I'oxygene incorpore dans la structure des charbons au cours de I'oxydation forme surtout des liaisons carboxyles et hydroxyles qui sont eliminees pendant la premiere phase de la pyrolyse sous forme de C02 et de H20. Ainsi diminue nettement la quantite d'hydrogene disponible aux temperatures plus elevees pour des reactions exothermiques de deshydrogenation
The relation between coals' structure and the reaction heat of pyrolysis and carbonization has been studied by differential thermal analysi (DTA) coupled with the Fourier transformed infrared analysis (FTIR). Fresh and oxidised to different degrees coals have been analyzed with a specific procedure limiting the inherent errors caused by swelling or shrinking of coal during its heating. Those measurements havE shown that for all the coals studied the heat flow is endothermic at the beginning of the pyrolysis and then, when the temperature increas it's becoming exothermic. The exothermic elfect decrease remarkably when the degree of coal oxidation increases. By comparison of thermal analysis results with the results of the gaseous products analysis as well as the evolution of the coal structure of fresh and oxidised coals, we are showing that the evolution of the heat flow during coal heating is the result of the instantaneous balance of the deoxidation reaction heat, which is rather endothermic and the dehydrogenation reaction heat, which is rather exothermic. The water formation is an endothermic reaction and it's influence on the reaction heat is particularly visible during the pyrolysis of the oxidised coals. Indeed, the oxygen incorporated into the coal structure during its oxidation forms carboxyl and hydroxyl linkages which are eliminated during the first phase of pyrolysis and forming C02 and H20. In the same time the quantity of the available hydrogen for the exothermic reactions of dehydrogenation diminishes

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
É bem conhecido o alto peso que o coque representa no custo final do ferro-gusa, além do que, as suas propriedades estão intimamente ligadas à performance dos altos-fornos. Portanto, buscar uma qualidade do coque compatível com as necessidades do alto-forno e com o menor custo possível, se transforma em uma tarefa difícil senão se dispuser de ferramentas que permitam uma correta seleção de carvões e testes prévios em fornos pilotos. Dentre as propriedades utilizadas pelos altofornistas para qualificar o coque, se destacam a CSR - resistência mecânica após reação com CO2, e a CRI - índice de reatividade, por serem, respectivamente, uma medida direta da reação de Boudouard - solution loss, e da associação desta com a resistência do coque. Com isso se torna possível prever o consumo desta matéria prima nos altos fornos e, devido a sua grande influência nos custos da operação, mensurar seu impacto na economicidade do processo. A unidade de coqueificação do processo heat recovery da ThyssenKrupp Companhia Siderúrgica do Atlântico - TKCSA, possuindo uma concepção diferente do tradicional by product coking process, utiliza um forno piloto próprio, especificamente projetado pela empresa, com o qual se procura simular as condições operacionais das unidades de coqueificação. Entretanto, essa unidade de coqueificação ainda carecia de um estudo experimental especifico capaz de permitir uma análise comparativa confiável entre o coque produzido e o das baterias industriais. O objetivo principal desta dissertação foi desenvolver um modelo de previsão da CSR -resistência mecânica do coque após reação com CO2, e do CRI através da coqueificação de misturas de carvões, obtidas por diferentes metodologias, em no forno escala piloto e sua comparação estatística com os dados obtidos em escala industrial na ThyssenKrupp Companhia Siderúrgica do Atlântico - TKCSA. O modelo de previsão para o CSR quando obtido através de escala piloto se mostrou bastante aderente aos dados obtidos em escala industrial. Portanto, os procedimentos utilizados e este modelo desenvolvido mostraram-se adequados, e podendo assim ser usados como ferramenta para auxiliar na seleção e compra de carvões.
It is well known that coke has a major importance on the final cost of the Hot Metal and besides this fact its properties are closely connected with the performance of blast furnaces. Therefore, seeking a type of coke compatible with the blast furnace technical requirements and at the lowest possible price may become a hard challenge if neither a prediction tool is available to accomplish a correct selection of coals nor previous test were made on coke test facility. Among the properties used by the Blast Furnace specialists to qualify the coke, it can be highlighted CRI - Coke Reaction Index and CSR - Coke Strength after Reaction with CO2, because they represent a direct measure of the Boudouard reaction – solution loss, and its association with the coke strength, respectively. Based on them it is possible to predict the consumption of this raw material in the Blast Furnaces and, due to its high influence on the operational costs, measure its impact on the overall process economy. The Coke Plant unit at thyssenkrupp Companhia Siderurgica do Atlantico - TKCSA follows the coking process known as heat recovery and its concepts differ from the traditional one, by product. This unit uses its own coke test facility, specifically designed by the company s experts to simulate the operational conditions at the coke plant industrial furnaces. However, the coke test facility still required further specific experimental study capable of making a reliable comparison analysis between the cokes produced in it with the one from the industrial coke batteries. The main goal of this dissertation is to develop model to predict the CRI - Coke Reaction Index and CSR - Coke Strength after Reaction with CO2, through the coking process of coal blends, generated by different methodologies, charged on the coke test facility statistically compared with the ones from the industrial Coke plant at thyssenkrupp Companhia Siderúrgica do Atlântico - TKCSA. The prediction of CSR represented when generated through the coke test facility showed good adherence with the values obtained with the industrial scale. Therefore, the current procedures used on the developed model has proved to be adequate and may be used as a predicting tool to help the purchase of coals.

Malgre sa specificite, c'est-a-dire, sa dependance de l'evolution siderurgique, pour etudier le marche du charbon a coke nous sommes obliges d'analyser tout de meme, d'une facon superficielle, l'evolution du marche des combustibles capables de remplacer partiellement le coke dans les hauts fourneaux. On doit par consequent de faire un survol de l'histoire de la consommation energique des le debut, c'est-a-dire, concomitente avec la premiere revolution industrielle. Tout cela afin de nous permettre a comprendre la structure et le comportement de ce marche. Il semblerait que c'est l'oligopole de sweezy qui explique meilleur le comportement du marche international du charbon. Par la suite on se restreint a l'analyse du charbon a coke, et c'est la que l'etude de l'evolution de l'avenir de la siderurgie s'impose, principalement pour comprendre les erreurs concues dans les modeles de previsions siderurgiques rapelles par la suite. Et la, pour bien comprendre l'etat du developpement, le "wocol" nous a apparu le plus efficace depuis 1980
The coking coal's international maket depends of the steel works evolution in the production. So,we need to analyse superficialy the market evolution of the capable substitutes combustible in the blast furnaces since the first industrial revolution. The sweezy's monopoly explain well the market behaviors in this case. For develop afterwards we restrain to the developement steel works industry. Mainly to understend the forecast faults commited in the mathematics models. Then, to well understend the country developement level the "wocol" was the more efficient forecast model since 1980

This study aimed to investigate the relationship between the tensile strength of metallurgical coke and both the textural composition of the carbon matrix and the porous structure of the coke, and further to assess the use of these structural features as bases of methods of coke strength prediction. The forty-four cokes examined were produced in a small pilot-oven from blended-coal charges based on six coals differing widely in rank. Their textural composition was assessed by incident polarized-light microscopy while pore structural parameters were measured by computerized image analysis allied to reflected light microscopy. The tensile strength of coke could be related to textural data with accuracy using several relationships, some of which were based on a model for the tensile failure of coke. Relationships between tensile strength and pore sturctural parameters were less successful, possibly because of difficulties associated with the measuring system used. Neverthless relationships involving combinations of pore structural and textural data were developed and investigated. It was shown that relationships between tensile strength and calculated textural data had promise as the basis of a method of coke strength prediction. Also, tensile strengths could be calculated from the blend composition and the tensile strength of the coke produced from component cokes. Both methods have value in different situations.

The enrichment of alkali in the blast furnace has been proven to be a catalyst of coke gasification and is thus a key parameter in the degradation of coke. Alkali also directly destroys the carbon structure, increases the risk of scaffold formation, increases the load and attacks the refractory. It is thus important to decrease the recirculation of alkali in the blast furnace and the gasification of coke to ensure sufficient strength of the coke. The aim of the present study was to examine possible ways of alkali control in the blast furnace. This was done by investigating if coke with a modified ash composition contributed to a higher capacity of binding alkali in stable phases, which can be drained via the slag. This would decrease the recirculation of alkali in the blast furnace and prohibit coke degradation. Two campaigns were studied to determine the distribution of alkali in the shaft when the charging differed, this to improve the understanding of alkali control in the blast furnace with respect to the charging practice. Three different test cokes were produced in pilot scale with a mineral addition of kaolin, silica or bauxite. The test cokes were together with base coke used as a reference, charged in baskets to LKAB’s Experimental Blast Furnace (EBF) at the end of a campaign. When the campaign was finished the EBF was quenched with nitrogen and the charged baskets were excavated. The influence of alkali on coke with a modified ash composition was examined with XRF, XRD, SEM-EDS and TGA. This was done in order to confirm any difference between the test cokes and the base coke in terms of chemical composition, phases in the coke ash, degree of graphitisation and reactivity. The results showed that the base coke in most cases had collected more alkali compared to the test coke with a mineral addition of kaolin and silica. For the test coke with addition of bauxite the alkali content was higher in three out of four samples compared with the corresponding base coke. Unreacted grains with bauxite were detected, which indicates that bauxite was completely or partly inactive in the capturing of alkali. All aluminosilicates detected in the coke samples contained alkali, which indicates that aluminosilicates contributes in the capturing of alkali in the EBF. The main mineral phases containing potassium in the coke were kalsilite, leucite and other aluminosilicates with varying alkali content. The carbon conversion and thus the reactivity increased with the alkali content in both the test coke and the base coke. The reactivity of the test coke was thus not decreased due to the mineral addition. No indications of an increased capacity of capturing alkali in stable phases could be seen in the test cokes, this could be due to the low amount of minerals added. The uptake of alkali in the different coke types was dependent of the horizontal and vertical position in the EBF, and thus the conditions the baskets had been exposed to and the distribution of alkali within the EBF. It was concluded that the charging had an impact on the alkali distribution in the EBF. During campaign 31 the alkali content was more evenly distributed over the horizontal section in the upper part of the furnace, in the lower shaft the alkali content increased towards the centre. During campaign 32 the alkali content was increasing towards the walls in shaft of the EBF. The content of alkali in the lower shaft was higher during campaign 32 compared with campaign 31.

Inscrite dans le cadre du projet européen Coke Oven Operating Limits, cette thèse porte sur la modélisation thermomécanique d'un piédroit de cokerie. Le piédroit est une maçonnerie alvéolaire, chauffée par des gaz à haute température (supérieure à 1200°C). Pendant la cuisson du charbon dans les fours à coke, celui-ci se pyrolyse en coke provoquant une poussée sur les panneresses du piédroit. Ce projet a pour objectif de déterminer la pression maximale supportée par ces structures. Afin de répondre à cette problématique, un nouveau modèle thermomécanique de piédroit a été développé. Ce travail prend en compte à la fois le comportement non-linéaire de la maçonnerie, mais également les interactions avec l'environnement extérieur. La modélisation de la structure maçonnée est basée sur une approche macroscopique où les briques et le mortier sont remplacés par un matériau homogène équivalent, et ce pour différents états de joints. La non-linéarité du comportement est reproduite grâce à un critère d'ouverture qui permet de passer d'un état de joint à un autre. Les propriétés homogénéisées sont identifiées selon une approche énergétique couplée à un algorithme d'identification inverse. Plusieurs simulations numériques d'essais issus de la littérature ont permis de valider cette approche. Les paramètres régissant le comportement mécanique et thermique des matériaux sont déterminés expérimentalement ainsi que la tenue de l'interface brique/mortier. Les conditions aux limites du modèle sont établies à l'aide d'une instrumentation thermomécanique sur site industriel. Les simulations thermomécaniques du piédroit permettent de localiser des phénomènes de dégradation observés dans les faits.

A Work Project, presented as part of the requirements for the Award of a Masters Degree in Management from the NOVA – School of Business and Economics
This project is about how significant the positive solutions mean to Coca Cola Co. and emphasizes that if all three factors, GloCal Vision, Positive Psychology and the Stakeholder Theory are taken into consideration simultaneously then tailored positive solutions can be the result. Based on these indicators and compared with Dove’s success, we have found that Coke’s “Open Happiness” campaign is not qualified as a positive solution for obeying neither positive psychology nor the stakeholder theory. Later, after screening four solutions, one positive solution is kept and admitted to help Coke be more successful.

The inorganic chemistries of coal and petroleum differ because of their disparate geologic environments of formation, the physical state of the fuels, and the type and quantity of minerals and organic compounds in the fuels. Commercial coals typically contain 2 to 25% ash (average ~ 10%) while petroleums contain 0.003 to 0.07% ash (average ~ 0.01 %). Globally averaged, coal ash is dominated by Si, Fe, Ca, AI, and S, whereas petroleum ash contains significant quantities of V, Ni, S, Fe, Ca, Na, K, Mg, Si and AI. This larger number of important elements causes petroleum combustion slags to have more complex phase assemblages. The high vanadium contents of petroleum-based combustion feedstocks yield numerous crystalline V -oxides with stoichiometric amounts of Ca, Fe, Mg, AI, Ni andlor Na in the resulting slags. Slightly lower nickel contents yield abundant NiFe and Ni sulfides. The dominance of metals over silicon results in the formation of crystalline silicates following metal saturation of immiscible Si-rich glasses. High gasification temperatures (1200 - 1500°C) promote the development of equilibrial assemblages. Chemical variations between individual feedstock cokes coupled with nonuniform operational conditions result in three principal categories of petroleum coke slag; 1) sulfide dominant, 2) silica dominant, and 3) oxide dominant. Sulfide dominant slags are not necessarily derived from feedstocks with high sulfur contents, instead they appear to derive from feedstocks rich in chalcophile elements, predominantly Fe and Ni, by attracting sulfur otherwise lost by volatilization. Slagging additives can change the chemical categorization of resulting slags through phase modifications and the formation of new phases; this in tum can strongly alter the physical behavior of the slags. Compositionally diverse spinel oxides are the most common crystalline slag phase because of their wide thermal and compositional stability ranges, refractory nature, and rapid growth kinetics. Spinel compositions are strongly influenced by the inorganic chemistry of the feedstock, the composition of host phases, and the composition of additives. Coke slag spinels are generally enriched in AI, Fe, V, Mg, and Ni, and often contain Cr that is derived from reaction with refractory material.
Ph. D.

Pyrolysis-biorefinery shows great promise for the production of liquid fuels and chemicals from non-food lignocellulosic biomasses. Coke formation and catalyst deactivation are among the biggest challenges facing the technology development. This study investigated the formation of coke during the hydrotreatment of bio-oil from the pyrolysis of mallee wood. Bio-oil with externally added sugars and phenolic compounds was also hydrotreated to gain better understanding about the reactions involved in coke formation.

L'hydrodésulfuration (HDS) est un procédé majeur du raffinage pétrolier pour enlever le soufre des charges, typiquement avec un catalyseur CoMoS/Al2O3. Pendant un cycle du procédé d'HDS, la désactivation du catalyseur est due à trois causes principales : dépôt de coke, dépôt de métaux et ségrégation de la phase active. L'objectif de ce travail a été l'étude de l'effet du cokage et modifications de la phase active sur la désactivation du catalyseur d'HDS (de type CoMoS/Al2O3) appliqué à l'HDS des gazoles et la recherche des paramètres clés pour l'obtention d'un catalyseur usé comparable à celui issu de raffinerie. Des tests de vieillissement accéléré ont été réalisés avec différentes charges (différentes teneurs en aromatiques), couverture en hydrogène, durée et un pré-traitement de réduction. Après chaque test, les catalyseurs ont été caractérisés en termes de texture (méthodes BET et BJH), coke (Raman, IR, TPO, RPE, ToF-SIMS) et phase active (MET/EDX, XPS, TPR). En termes de texture et coke, une teneur élevée en aromatiques dans la charge et une couverture en hydrogène faible favorisent la formation de coke. Pour augmenter l'organisation du coke par rapport au catalyseur industriel, nous avons proposé un test plus long. En termes de phase active, une longue durée, couverture en hydrogène élevée et une pré-réduction favorisent plus d'hétérogénéité des teneurs en soufre et cobalt de la phase active et la formation d'agglomérats de sulfure de cobalt. La pré-réduction semble être efficace pour simuler l'exposition à des températures élevées pendant un cycle d'HDS, ce qui conduit à la ségrégation de la phase active, une caractéristique d'un catalyseur usé industriellement
Hydrodesulfurization (HDS) is a major process of petroleum refining for sulphur removal, where CoMoS/Al2O3 is the typical catalyst. During the cycle of a HDS process, deactivation of the catalyst is attributed to three main causes: coke deposition (with loss of pore volume), metals deposition and segregation of the active phase. The aim of this work was to study the effect of coking and active phase changes on the deactivation of the HDS catalyst (of CoMoS/Al2O3 type) applied to the HDS of a diesel feed and find the key operating conditions to obtain a spent catalyst comparable to the industrial one. Accelerated aging tests have been performed with different feedstocks (different amounts of aromatics), hydrogen to oil ratio, duration and a pre-reduction treatment. After each test, catalysts have been characterized in terms of texture (BET and BJH methods), coke (Raman, IR, TPO, EPR, ToF-SIMS) and active phase (TEM/EDX, XPS, TPR). In terms of texture and coke, a high amount of aromatics on the feedstock and low hydrogen to oil ratio favor the formation of coke. In order to increase the organization of graphitic coke, we have proposed a longer test. In terms of active phase, a long duration, high hydrogen to oil ratio and a pre-reduction treatment favor loss of dispersion of sulphur and cobalt contents of the active phase and formation of cobalt sulfide agglomerates. Pre-reduction seems to be an effective treatment to simulate the exposure to high temperatures during a HDS cycle which results in segregation of the active phase, a fingerprint of an industrial spent HDS catalyst

Thesis (M.S.)--West Virginia University, 2007.
Title from document title page. Document formatted into pages; contains x, 106 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 101-102).

La réalisation d'une unité pilote de pyrolyse (respectant divers paramètres industriels) a permis la caractérisation en continu du procédé de carbonisation sous faible surpression avec présence d'un gaz contribuant à l'agitation de la masse. La microscopie optique et la microscopie électronique par transmission ont permis de déterminer les faciès composant le carbonisat. Le brai d'origine optiquement isotrope acquiert progressivement une anisotropie. Le carbonisat obtenu est composé de domaines anisotropes qui sont majoritaires et de gouttes isotropes réparties aléatoirement dans les domaines. La forme des gouttes (ovoïdes ou allongées) est liée aux contraintes provoquées par le passage du gaz dans la masse. Le carbonisat est caractérisé par son taux de matières volatiles. Ce dernier permet de juger seulement de la quantité de gouttes et non de les qualifier. Pour améliorer cette qualification, une mesure de microdurète Vickers, un test de solubilité au toluène et une analyse thermogravimétrique sont indispensables. Il est important de connaître la quantité de gouttes dans le carbonisat, leur morphologie et leur nature. Ceci permettra de prévoir la qualité des pièces réalisées ensuite en production.

Thesis (Ph. D.)--West Virginia University, 2000.
Title from document title page. Document formatted into pages; contains xviii, 235 p. : ill. (some col.) Vita. Includes abstract. Includes bibliographical references (p. 190-195).

La pyrolyse de grains de charbon en four tournant permet de produire un coke réactif principalement utilisé en électrométallurgie. Le but de cette étude est d'analyser et de modéliser les différents phénomènes impliqués dans ce procédé afin d'améliorer le fonctionnement et la conduite de l'installation industrielle. La pyrolyse du charbon a été étudiée par thermogravimétrie et analysé chromatographique des gaz émis afin de déterminer la cinétique de dégagement de chaque constituant des matières volatiles. L’enthalpie de réaction de la pyrolyse a été mesurée par calorimétrie à flux différentiel. Le mouvement de la charge en four tournant a été étudié grâce à des expérimentations en four pilote. Les mesures effectuées concernent le temps de séjour moyen, la distribution des temps de séjour, le profil de chargement et le temps moyen passe par un grain en surface du talus. Des corrélations adaptées à la modélisation du mouvement de la charge ont été déterminées. Les transferts de chaleur ont fait l'objet d'une étude approfondie: ils incluent le transfert en régime transitoire à travers la paroi et le rayonnement paroi/solide qui est partiellement absorbé par le gaz qui s'interpose. La démarche adoptée pour la modélisation de ce procédé a consisté à simuler, dans un premier temps, la pyrolyse d'une particule isolée. Le modèle de grain ainsi établi a ensuite été inséré dans une représentation globale du four en tenant compte de l'hydrodynamique du réacteur, des transferts de chaleur entre la paroi, le solide et le gaz et des réactions de combustion des matières volatiles. Ce modèle a été validé grâce à un ensemble de mesures effectuées sur le four tournant industriel et utilisé avec succès pour l'amélioration du fonctionnement de cette installation

O crescente aumento dos preços de carvões de alta qualidade para a coqueificação e sua escassez em todo o mundo tem levado produtores de coque a buscar novas alternativas para a composição de suas misturas. No entanto, mudanças na matriz das misturas de carvões devem ser acompanhadas pela manutenção da qualidade do coque. O presente estudo teve como objetivo geral avaliar a influência do uso de um carvão colombiano médio volátil com alta heterogeneidade, bem como carvões de baixo e alto volátil americanos na qualidade do coque. Para isso esses três carvões e mais dois carvões médio volátil, tipicamente utilizados na produção de coque, foram caracterizados e submetidos a carbonização. Assim foram produzidos em forno piloto (250 kg) coques a partir dos carvões individuais e de três séries de misturas. A caracterização dos coques produzidos foi realizada através de sua análise química, (análises imediata e enxofre), textura óptica, porosidade, resistência mecânica a frio (DI e tambor “I”) e reatividade (CRI e termobalança). Os resultados obtidos apontam que nas condições avaliadas o uso de carvão colombiano em detrimento de carvões de médio volátil teve pouca influência sobre a qualidade do coque até percentuais de 30%, enquanto aumentos maiores afetaram de forma negativa a qualidade do coque. Os limites máximos encontrados para a substituição dos carvões de médio volátil pelos carvões de alto e baixo volátil foram de 30 e 10%, respectivamente. Além disso, foram encontradas e discutidas as relações entre a textura óptica dos coques e sua reatividade, onde a reatividade dos coques aumentou com a diminuição do tamanho da textura óptica dos coques. Verificou-se também que o teste de reatividade em termobalança é uma boa alternativa para a caracterização da reatividade de coques, podendo ser correlacionado a testes padronizados (CRI). O modelo aditivo para a estimativa da textura óptica do coque,com base nos parâmetros dos coques individuais, mostrou uma boa correlação entre os dados experimentais e calcula dos e pode ser usado como uma ferramenta para ajudar na otimização de misturas de carvões.
The increasing price of prime coking coals and their scarcity worldwide have leaded the coke producers to look for alternative ways to compose their coal blends. However, any changes in coal blends should be done follow by the maintenance of the coke quality. The main objective of the present study was to assess the influence of a medium volatile Colombian coal of high heterogeneity, as well as low and high volatile American coals on coke quality. For this propose one Colombian coal of high heterogeneity and four coals typically used as components of coking blends were characterized and submitted to carbonization. Thus, cokes from single coals and three different series of coal blends were produced in a pilot scale coke oven (250kg). Coke characterization was performed by chemical analysis (proximate and sulfur analysis) ,determination of coke optical texture , porosity, mechanical strength tests (DI and I-Type Coke Tumbler) and reactivity tests (thermobalance and CRI)conditions evaluated using. The results showed that the substitution of medium volatile coals by Colombian coal had slight influence on coke quality for percentages equal to or below 30%, whilst further additions had a negative effect on coke quality. The maximum limits found for the replacement of medium volatile for low and high volatile coals were 10 and 30%, respectively. Moreover, the relationship between coke optical texture and reactivity was found and discussed, where coke reactivity increased with decreasing size of the optical texture components. It was also found that the reactivity test carried out in thermobalance is a good alternative for the characterization of coke reactivity and it can be correlated with standardized tests (CRI). The additive model to estimate coke texture, based in individual cokes, showed a good agreement between experimental and calculated data and can be used as a tool to help in the blend composition process.

L’objectif de la thèse est de comprendre et de modéliser les principaux phénomènes chimiques qui gouvernent les performances du premier réacteur, et en particulier le rôle du solvant donneur d’hydrogène, ainsi que les interactions entre charbon, solvant, hydrogène gazeux et catalyseur. L’impact des conditions opératoires telles que la température, la pression d’hydrogène, le temps de séjour ainsi que l’impact de la qualité de la charge (type de charbon et teneur en cendres) et du type de solvant ont également été évalués. Ce travail s’articule autour d’une partie expérimentale réalisée en autoclave et d’une partie modélisation basée sur un schéma réactionnel simplifié et sur un regroupement par familles chimiques. Dans un premier temps, la partie expérimentale a consisté à mettre au point une stratégie adaptée à l’étude. L’outil utilisé est un réacteur batch de type autoclave fonctionnant jusqu’à 25 MPa et 450°C qui sont des conditions opératoires classiques en hydroliquéfaction du charbon. La charge de référence utilisée est un charbon Illinois n°6, bien connu dans la littérature. Le solvant utilisé est le 1,2,3,4-tétrahydronaphtalène (tétraline) qui est une molécule naphténo-aromatique potentiellement donneuse d’hydrogène et qui a été couramment utilisée au laboratoire pour ce type d’étude. Enfin, un seul catalyseur sulfuré NiMo/Al2O3 a été testé, l’objectif de cette étude ne portant pas sur ce paramètre. Un protocole spécifique de post-traitement a été optimisé pour séparer les différentes fractions de liquéfiats produits, avant leur caractérisation. La démarche originale mise en place dans ce travail a consisté à fractionner les liquéfiats par microdistillation à bande tournante (50 plateaux théoriques) puis à fractionner la coupe résidu sous vide via des extractions par solvants. La microdistillation a ainsi permis de séparer les liquides en quatre coupes : Pi-230°C, 230-350°C,350-450°C et 450°C+, avec une bonne performance de séparation, isolant notamment la quasi totalité du solvant dans la fraction légère, performance difficile à atteindre sur des outils plus classiques. Chacune de ces coupes a été analysée en distillation simulée par chromatographie gazeuse et par analyses élémentaires CHONS. Le résidu sous vide (450°C+) a ensuite été fractionné en huiles lourdes, asphaltènes et préasphaltènes, par solubilité dans l’heptane et le toluène respectivement. Ce protocole a été appliqué à chacun des 66 essais de liquéfaction réalisés dans l’autoclave, ce qui a permis d’effectuer des bilans matières complets et d’évaluer l’impact des conditions opératoires, des interactions solvant-phase gaz-catalyseur et des différentes charges. Pour chaque bilan, le taux deconversion, les structures de rendements et les performances en hydrotraitement ont été déterminés ainsi que la répartition entre la phase gaz et le solvant dans l’hydrogénation du charbon
This work deals with the understanding and the modeling of coal hydroliquefaction mechanisms, more precisely the impact of operating conditions and H-donor solvent -hydrogen gas phase-catalyst interactions. Experimental tests are performed in a batch reactor by using Illinois #6 coal, tetralin and NiMo/Al2O3 catalyst. An original separation procedure is developped, combinig micor-distillation and solvent extraction. Complete mass balances allow the dtermination of conversion, product yields and product quality. Operating conditions studied are temperature (380° C-420°C), hdrogen pressure (16-22 MPa) and NiMo/Al2O3 presence. Temperatures mainly impacts the firs stage of liquefaction (also called dissolution), hydrogne pressure and catalyst the products quality. Then, tests performed with other solvents (n-undecan or diethylbenzene) and/or under N2 pressure have shown the crucial impact of solvent on the first stage of liquefaction, and and the high impact of gas phase o products quality. These experimental results allow the establishment of kinetic model. In a first step, maceral are transformed into coke, preasphaltenes and hydrotreatment products. Coke formation only depends on temperature. However, preasphaltenes and hydrotreatment products formation highly depends on solvent. Other products (asphaltenes, vacuum distillate, middle distillate, light distillate and gas) are producted from preasphaltenes

The influence of coking conditions, with respect to position in a commercial coke-oven, on the mechanical behaviour of blast furnace coke has been studied. This involved the determination of density, porosity, the characterization of microstructure and assessing the influence of all three on the compressive strength of coke. The plastic flow properties were also investigated at temperatures greater than 1000°C. Three coke batches, originating in a 5m commercial coke-oven at three different positions with respect to height (0.8m, 3.3m and 5m below the coal line), along with three coke batches produced in a 460mm test-oven, were supplied by Energy, Mines and Resources (CANMET) in Ottawa. A warf coke batch was also provided as a control sample. Several hundred core-drilled specimens (≃1.3cm diameter and 1.3cm length) were produced from the seven coke batches. The bulk density of each cylindrical coke specimen was determined. Also, a detailed microstructural analysis, using a Leitz Image Analyzer, of the flat faces of the coke cylinders was performed to quantitatively characterize the pore and cell wall size, and the pore geometry. The compressive strength of each coke cylinder was determined both at ambient temperature and at 1400°C. In addition, the plastic flow behaviour of the commercially produced coke batches was studied. Results indicate that the coke product bulk density was affected by the coke-oven pressure (static load). Studies of the test-oven coke batches revealed that coke bulk density increased with higher oven pressure. Furthermore, the pore size was found to be larger for cokes produced at lower oven pressures. The cell wall size did not appear to be affected by coke-oven pressure. The bulk density of the commercially produced samples increased with depth below the coal line. This was attributed to a higher temperature and static load that existed at the bottom of the battery. The pore size was larger in cokes extracted from higher regions. No correlation of cell wall size with depth below the coal line was found. However, an oven size effect on the pore and wall size was noticed. Both the pore and wall size was smaller in the test-oven coke batches. The compressive strength of coke was higher in batches subjected to higher coke-oven pressures. Similarly,' the compressive strength of commercial coke batches was higher for coke batches extracted from regions near the sole of the coke-oven, than that for coke batches extracted from higher regions. It was concluded that high oven pressures resulted in cokes exhibiting a lower porosity and small pores which had the combined effect of producing stronger coke. Coke strength was generally shown to be higher at 1400°C than at room temperature. The test-oven cokes were always stronger than cokes produced in the 5m commercial coke-oven. Constant load tests revealed that coke exhibited plastic flow behaviour at temperatures above 1000°C. The time dependent strain data was described using an interactive-double-Kelvin element visco-elastic model.
Applied Science, Faculty of
Materials Engineering, Department of
Graduate

The size distribution and strength of metallurgical coke are factors vital for the steady and high-efficiency operation of a blast furnace, since these factors govern stack penneability. Coke strength influences the size of lump coke not only because of size degradation by impact and abrasion during transfer to and descent in the blast furnace, but also because of its influence on the fracture which takes place in the coke layer during carbonisation and the effect this has on the initial mean size and size distribution of the feed coke. Therefore, the elucidation of the relationship between coke strength and the fissure fonnation phenomena is significant. In this study, therefore, the coke strength development during carbonisation has been examined in conjunction with various parameters, such as the degree of carbonisation of the coal, namely the extent or fraction of pyrolytic reaction, and the degree of graphitisation of the coke, as well as carbonisation temperature and heating regime. The porous structure of coke has also been examined with a view to establishing a relation between the porous structure and the coking properties of the coal carbonised. The quality of coke porous structure was evaluated by parameters introduced in this study, i.e., the pore size distribution and pore rugosity factors. A poor porous structure is shown to be associated with high proportion of small pores and pores with a rough surface. These features are considered to stem from poor coking properties and the consequent poor adhesion between coal particles. An attempt has also been made to establish a mathematical model capable of predicting the degree of fissuring of coke during carbonisation by utilising the understandings obtained in this study of the coke strength development during carbonisation and the effect of coal properties on coke strength. Coke samples large enough to facilitate the observation of the degree of fissuring in relation to various coal properties and heating conditions, were made to evaluate the mathematical model and introduce the concept. The concept that fissuring takes place when developing thennal stress exceeds the developing coke strength is demonstrated to be capable to evaluate the effects of coal properties and heating conditions on the degree of fissuring observed.

This work is divided into two main parts, investigational and theoretical. The first part deals with the investigation of deposition values around integrated iron and steel works, and coke works, in South Wales, and with the changes in such values which arise as a result of modifications to process control or to arrestment equipment. A method of evaluation of such changes, based on the cumulative sum technique, is developed, which m1n1m1ses the effect of seasonal variations in the deposition values. It is demonstrated that there are two significant sources of particulate emission, from coke oven discharges, and from coke quenching. These are shown to have different spatial distributions, emissions from quench towers being very widespread, whereas emissions from oven discharges deposit relatively closer to the source. Methods to reduce both of these sources are described: It is shown that the use of arrestors in quench towers leads to enhanced emission of dissolved solids, but that the increase can be controlled by the use of additional sprays above the arrestors. The second part considers some theoretical aspects of quench tower operation. It is shown that the installation of arrestors leads to changes in gas temperature and gas composition in a quench tower, which cause increases in terminal settling velocity. The same changes lead to reduced condensation within the quench tower, and hence greater emission of steam, which gives a more buoyant emission, with more widespread dispersion than from open quench towers, as well as enhanced emissions of dissolved solids. Calculations are included which confirm the extent of the dispersion from towers fitted with arrestment devices.

A significant body of work exists around coke dissolution into liquid iron, however there are key aspects of this important reaction that are not well described. This study was focused on gaining the answers to the questions “How does the coke mineral matter behave during coke dissolution?” and “Can the effects of sulphur and oxide layer formation on the dissolution rate be separated and quantified?”. Issues that must be addressed if the understanding of the kinetics of this reaction is to be advanced and coke's use in the blast furnace further optimised.To this end, a detailed investigation was conducted examining the influence of coke mineral matter on coke (carbon) dissolution into liquid iron. This project was focused on the mineral matter layer that forms at the coke/iron interface and how the presence of this layer affects the kinetics of carbon dissolution from the coke into the liquid iron. A range of experimental techniques were used to identify and characterise the mineral layer as it formed at the coke/iron interface and to assess the layers influence on the carbon dissolution kinetics.Carbon dissolution experiments, utilising a carburiser cover technique, were carried out where carbon and sulphur transfer to an iron-carbon melt was measured over time at temperatures of 1450°C, 1500°C and 1550°C. This technique allowed fundamental data on the dissolution rate constant to be calculated, and the effects of temperature, melt sulphur and different carbonaceous materials to be explored.Development of the mineral layer at the coke/iron interface as a function of both time and temperature was studied utilising a quenched carbon dissolution technique that was developed during the project. This technique had the additional benefit of allowing the composition of the melt to be determined for a larger range of elements than the dissolution experiments. The quenched carbon dissolution experiments complemented the carbon dissolution experiments and allowed direct comparisons between the dissolution behaviour measured in the dissolution experiments and the composition and morphology of the mineral layer observed in the quenched samples.The dissolution studies were further complemented by sessile drop measurements of the wetting behaviour of iron on the mineral phases that were identified in the mineral layer present at the coke/iron interface, thermodynamic modelling utilising the MTDATA software package and a conceptual model of the interfacial mineral layer.A mineral layer was observed to have formed at the coke/iron interface during coke dissolution into liquid iron at experimental temperatures ranging from 1450°C to 1550°C. The mineral layer was solid at these temperatures and persistent at the interface. The amount of mineral matter present in the mineral layer was observed to be increasing with increased reaction time. The composition and structure of the mineral layer changed with both experimental time and temperature. The composition of the mineral layer was principally composed of oxides of aluminium and calcium, present as various calcium aluminates and calcium sulphides. Initially the mineral layer was a loose agglomeration of particles of which a majority were alumina particles. As the dissolution reaction proceeded, the loose agglomeration of particles was replaced by an open acicular layer that was predominantly the calcium aluminate CaO.6Al2O3 (CA6). As the dissolution reaction continued further, the calcium aluminates became increasingly richer in calcium oxide, with the predominate phase present in the mineral layer progressing through the calcium aluminates phases CA6 to CaO.2Al2O3 (CA2) and onto CaO.Al2O3 (CA). The apparent calcium enrichment of the mineral layer was observed to occur more rapidly as the experimental temperature increased. Accompanying the compositional changes in the mineral layer, the morphology of the mineral layer was also observed to change. The mineral layer was formed as an initial loose agglomeration of alumina particles, changing to an open acicular structure consisting of CA6/CA2 before being converted to a dense layer as the dissolution reaction proceeded and the composition of the mineral layer changed to CA and calcium sulphide (CaS) appeared at the interface.It was found that the formation of the calcium sulphide layer was preceded by the formation of the calcium aluminate layer. Only after the calcium aluminate layer had experienced progressive calcium enrichment and the CA and CA2 phases had formed did the CaS phase appear at the iron interface. Thermodynamic analysis of the experimental results confirmed that the formation of the calcium enriched calcium aluminates, CA2 and CA, were a necessary requirement to stabilise the calcium sulphide layer for the coke composition studied.The kinetics of carbon dissolution from the coke to the liquid iron were observed to be dependent on the structure of the interfacial mineral layer. This dependence was manifest as two stage behaviour in the first order mass transfer plots. The initial stage, characterised by rapid carbon dissolution, was observed while the mineral layer was developing or had the open acicular structure of the CA6/CA2 layer. The second stage was characterised by a significant reduction in the rate of carbon dissolution. The onset of the second stage was coincident with the change in the composition of the mineral layer from CA6/CA2 to CA2/CA and the associated densification of the mineral layer. In stating that the nature of the mineral layer affects the dissolution kinetics, a change in the reaction control mechanism is implied. This represents a change in the coke dissolution kinetics from simple mass transfer control to a mixed control regime where both mass transfer and the mineral (product) layer are active.In an attempt to overcome the problems associated with the heterogeneity of coke a coke analogue was developed. In the coke analogue the composition and dispersion of the carbonaceous and mineral matter (oxides) are controlled and the porosity is fixed. When single phase calcium aluminates were introduced into the coke analogues, calcium enrichment of the resulting calcium aluminate mineral layer was observed. The observed carbon dissolution kinetics were dependant on the structure of the interfacial calcium aluminate layer. Consistent with the coke dissolution studies, the calcium aluminate layer formed at the coke analogue iron interface during carbon dissolution was at least in part rate controlling the carbon dissolution reaction for the coke analogues studied.Utilising the sessile drop experimental technique the wettability with liquid ironcarbon-sulphur alloys of the predominate phases that were observed in the mineral layer were measured. It was observed that the contact angle decreased as the proportion of lime (CaO) in the calcium aluminate increased. Further it was observed that while the presence of sulphur in the melt increased the contact angle for the alumina and CA6 substrates, on the CA2 and CA substrates the contact angle was decreased. The improvement in the wetting of the CA2 and CA substrates with sulphur was attributed to the formation of CaS at the substrate/droplet interface.This study has produced new fundamental data on the growth and development of the mineral layer and the wettability of the predominate calcium aluminates observed in the mineral layer. These detailed studies have illuminated the changing nature of the layer in terms of both composition and morphology and found that the kinetics of carbon dissolution from the coke to the liquid iron were dependant on the structure of the interfacial mineral layer.

Les brais charbonniers sont les résidus de la distillation des goudrons de cokefaction. Leur comportement thermique peut être modulé par l'utilisation d'additifs comme le soufre. Ce travail est une étude systématique des facteurs pouvant modifier le comportement thermique des mélanges brai/coke, précurseurs des matériaux graphites, comme la composition chimique des brais, le pourcentage en soufre introduit, les lois de chauffe utilisées ou encore l'origine et les propriétés des cokes. Nous avons divisé notre travail en deux parties. Dans un premier temps, nous avons étudié le comportement thermique des mélanges brai/soufre. Nous avons clairement démontré l'effet bénéfique du soufre sur la formation de mésophase et donc sur les textures optiques. Nous avons défini les critères permettant de relier la réactivité thermique des mélanges à la composition chimique des brais et notamment nous avons précisé le role joue par la fraction legere du brai durant le traitement thermique et le role des qi sur l'evolution des textures optiques. L'utilisation des techniques spectroscopiques et thermiques nous a permis de suivre l'évolution des structures soufrées organiques et leurs stabilités en fonction de la température. Dans la deuxième partie de ce travail, nous avons étudié l'effet de l'addition de coke sur la texture physique du brai ainsi que le comportement thermique des mélanges brai/coke/soufre. Les cokes ont été caractérisés par leurs énergies et leurs morphologies de surface. Nous avons ensuite tente d'appréhender les phénomènes chimiques aux interfaces brai/coke en développant une méthode indirecte basée sur l'extraction aux solvants sélectifs d'un brai préalablement adsorbe sur un coke. Les résultats obtenus montrent une modification de la structure physique du brai, mise en évidence par une augmentation du rendement d'extraction à l'hexane dans le cas des mélanges brai/coke et par une modification de la composition chimique de la fraction soluble. L'ensemble des résultats de ce travail est utile, d'un point de vue fondamental pour la compréhension du rôle du soufre dans les brais et d'un point de vue des applications industrielles, pour l'adaptation des procédés
Coal tar Pitches (CTP) are the residues of cokefaction tar distillation. Their thermal behaviour could be modified by the utilization of additives like sulfur. This work is a systematic study of the factors which can modified the thermal behaviour of the CTP/coke blends, precursors of graphite materials, like the chemical composition of the CTP, the initial sulfur percentage, the heat law or the origin and properties of cokes. We have divided our work in two parts. In a first time we have studied the thermal behaviour of the CTP/sulfur mixtures. We have clearly shows the positive effect of sulfur on mesophase formation and in consequence on optical texture. Crieria have been defined, allowing to connect the blends thermal reactivity to the chemical composition of the CTP and more precisely, we have precised the light fraction role of CTP during thermal treatment and the role of QI on optical texture evolution. Utilization of spectoscopic and thermic methods allows us to follow evolution of sulfur structures and their stabilities in function of temperature. In the second part of this work, we have studied effect of coke addition on physical texture of CTP and thermal behaviour of CTP/coke/sulfur mixtures. Cokes have been characterized by their surface energies and morphologies. We have then tried to understand the physical phenomena on the CTP/coke interfaces using a non direct method based on selective solvant extraction of a CTP previously adsorbed on coke surface. The results show a modification of the CTP physical structure, put in evidence by an increase of the hexane yield extraction in a case of CTP/coke blends and by an evolution of the chemical composition of the hexan soluble fraction. All the results of this work is usefull for the comprehension of the sulfur role in CTP and for the adaptation to the industriel processes of graphite making

Les catalyseurs ni/al#2o#3 et nik/al#2o#3 donnent, en presence de cyclopentane sous atmosphere d'hydrogene, un depot de carbone bidimentionnel a t#c < t#b ( 441c) et du carbone filamentaire a t#c > t#b. La regeneration sous hydrogene a 800c de ces catalyseurs permet de gazeifier pratiquement la totalite du carbone bidimentionnel forme a t#c < t#b d'aspect tres toxique pour la fonction metallique. Dans les memes conditions operatoires, la reactivite des depots de carbone d'aspect filamentaire forme a t#c > t#b est faible, l'elevation du debit d'hydrogene augmente de facon notable la vitesse de gazeification du carbone et l'effet promoteur du potassium est confirme. L'eau diluee dans l'hydrogene a par contre une action inhibitrice sur la reactivite du depot de carbone, plus prononcee en absence du potassium. Par contre, son pouvoir oxydant doux est confirme au cours du vaporeformage du propane, effectuee sur les catalyseurs cokes. L'oxygene permet d'eliminer ce depot, mais son action reste brutale sur la fonction metallique, la recuperation de l'activite initiale exige une activation des catalyseurs sous hydrogene

L'hydrocokefaction est realisee a l'aide d'un petit reacteur a lit fixe dont les particules peuvent contenir soit des cokes actives, soit des catalyseurs, soit le produit lourd a traiter. Des molecules modeles sont utilisees pour determiner l'influence des conditions operatoires sur les rendements de craquage, de desulfuration et de desazotation

Les fours tournants font partie des réacteurs industriels les plus couramment utilisés pour des opérations de traitement de solides. Ce travail mêlant théorie et expérimentation a été consacré à leur étude et à leur simulation. Les différents phénomènes qui interviennent dans ce type d'unité ont été successivement examinés (mouvement axial et transversal de la charge, vitesse de réaction, échanges thermiques) soit en s'appuyant sur des travaux déjà existants, soit en effectuant des mesures complémentaires. Les informations recueillies ont permis d'élaborer des modèles mathématiques pouvant les représenter. Deux procédés volontairement différents l'un de l'autre (pyrolyse de déchets ménagers en four lisse et régénération de catalyseur en four conique à louvres) ont été étudiés afin d'illustrer 1' application de la méthodologie à des cas variés tant au niveau du fonctionnement du four que de la réaction à y effectuer. L'application à la régénération de catalyseurs a conduit à l'élaboration d'un outil de simulation utilisable pour parfaire la connaissance du four et identifier les éventuels disfonctionnements. L'application au four de pyrolyse de déchets ménagers s'est concrétisée par le développement d'un outil numérique simplifié, directement exploitable pour dimensionner des unités industrielles. Dans les deux cas, les résultats de simulation sont proches des relevés expérimentaux
The rotary kiln is one of the most widely used industrial reactors to treat solids. In the present work, this kind of unit is described using both experimental and theotetical investigations. The movement of the bed (axial and transverse), the heat transfers within the kiln and the reactions kinetics have been studied to develop mathematical models. Two different processes (catalysts regeneration and solid wastes) have been chosen to illustrate the methodology application to various cases (reaction and kiln geometry). The application to the catalysts regeneration has led to the elaboration of a simulation tool, giving information on the kiln behavior and identify eventual problems. The application to the pyrolysis kiln has given a numerical tool, which is usable to design industrial deviees. In the both cases, the results obtained by simulation are in good agreement with the experimental data

Thesis (M.S.)--West Virginia University, 2000.
Title from document title page. Document formatted into pages; contains xvi, 182 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 98-100).

La production du coke, utilisé en tant que combustible aux hauts-fourneaux, est assurée par un jeu de machines supervisées par un calculateur central et assistées par des machinistes pour la conduite (validation de fin de fonctionN), pour la maintenance (intervantion à la suite de l'apparition d'un défaut) ainsi que pour la sécurité des personnes et du matériel. L'analyse de l'existant met l'accent sur les dysfonctionnements qui bloquent le passage à une conduite entiérement automatique des machines. Le manque de fiabilité, la gestion des défauts et le systèmede positionnement ressortent comme étant les principaux points critiques à prendre en considération. Pour assurer une bonne fiabilité des équipements, une application d'aide à la maintenance a été développée et mise en service sur PC à la cokerie et concerne le calcul du temps de cycle et les mesures des taux de fiabilité par fonction. Un traitement analogue a été proposé pour le traitement des défauts. Les propositions d'amélioration de la gestion des défauts visent une simplification et une plus grande autonomie des automates machines. L'interface machine/four génere le lot majeur des défauts. Le positionnement, basé sur des mesures du génerateur d'impulsions (GI), est un point critique puisqu'il reste en boucle ouverte sur les 50 derniers centimètres à parcourir et est tributaire de tout patinage ou glissement de la roue. Les contraintes en temps (7 m en 30 s), l'inertie des machines (400 tonnes) et le nombre limité de capteurs au sol (1 par four) rendent difficile une démarche classique de bouclage. Une commande prédictive par auto-compensation de l'erreur permet d'améliorer le système de positionnement sans remise en caude de l'existant. Le suivi des écarts GI par rapport aux fours intermédiaires permet de quantifier les mesures passées des patinages et des glissements à partir desquelles on prédit l'erreur finale. Le modèle de prédiction est élaboré par une méthode de régression linéaire multivariable basée sur la méthode des moindres carrés, mise en oeuvre sous Excel, et est valide suivant des critères statistiques.

L'éthanol est converti, à 350°C sous 30 bar et sur des zéolithes protoniques, en un mélange de paraffines légères et d'aromatiques ; produits incorporables dans le pool essence. Cependant, la transformation de EtOH sur zéolithes acides conduit à la formation du coke. Des techniques physiques avancées, en particulier les techniques MALDI et LDI-TOF MS, couplées à la méthode d'analyse qui consiste à récupérer dans un solvant les molécules carbonées après dissolution de la zéolithe dans HF, contribuent à caractériser finement le coke. Sa composition dépend du catalyseur : sur HBEA(11), zéolithe à larges pores, 17 familles ont été détectées contre 4 sur HZSM-5(40) de taille de pore intermédiaire. Sur cette dernière, le coke, composé de polyalkybenzènes / naphtalènes / phénalènes et pyrènes, est localisé à l'intersection des canaux et a une toxicité vis-à-vis des sites acides de Brønsted de 1. En dépit d'un empoisonnement total, cette zéolithe est toujours capable de convertir EtOH, comme MeOH, en hydrocarbures et qui plus est avec les mêmes sélectivités en produits. La transformation de ces deux alcools ne s'explique pas par un mécanisme classique de catalyse acide, mais par un mécanisme concerté radicalaire-acide. La présence d'un inhibiteur de radicaux dans la charge réactionnelle, l'hydroquinone, provoque une désactivation immédiate et une diminution de la concentration des radicaux. La transformation de EtOH et MeOH passe par un intermédiaire réactionnel commun, le carbène :CH2, dont l'oligomérisation radicalaire conduit à la formation d'oléfines. Ces oléfines légères (n-O3-n-O5) sont très réactives et se transforment par catalyse acide (oligomérisation / cyclisation / t
Ethanol is converted into light paraffins and aromatics mixture at 350°C under 30 bar over protonic zeolites. These products can be incorporated in the gasoline pool. Nevertheless, EtOH transformation over acid zeolites leads to the formation of the coke. Advanced physical techniques, in particular MALDI and LDI-TOF MS, were coupled to the coke analysis method. This method consists of the recovery of the carbonaceous molecules in a solvent after zeolite dissolution in hydrofluoric acid solution. This coupling allows characterizing the coke through an extensive way. The coke composition depends on the catalyst morphology: over HBEA(11) zeolite of large pores, 17 families were detected while 4 over HZSM-5(40) of intermediate pore size. Over this latter, the coke, composed of polyalkylbenzenes/naphtalenes/phenalenes and pyrenes, is located in the channels intersections and has toxicity of 1 towards Brønsted acid sites. In spite of a total poisoning, HZSM-5 zeolite is always able to convert EtOH, like MeOH, into hydrocarbons with the same products selectivity. The transformation of the two alcohols cannot be explained by a classical mechanism of acid catalysis, but by a cooperative radical-acid mechanism. The presence of a radical inhibitor in the feed, the hydroquinone, causes an immediate deactivation and a decrease in the concentration of radicals. The transformation of EtOH and MeOH passed by the common reaction intermediate, the :CH2 carbene, which its radical oligomerization leads to the formation of olefins. Olefins (n-O3-n-O5) are very active and can be transformed through acid catalysis (oligomerization/cyclisation/Hydrogen transfer) into aromatics or undergo isomer

Thesis (MTech (Chemical Engineering))--Cape Technikon, Cape Town, 2002
The activation of green '"'Smartie"" coke (a mixture of medium temperature pitch and waxy oil coke) was investigated in a laboratory scale fluidised bed (FB) and a rotary kiln as function of (1) heat treatment temperature (HIT) and (2) heat treatment time (HTt). Activation in the FB was more effective (in terms of surface area development) and the product obtained from this type of reactor had a larger percentage of mesopores than the products from the rotary kiln. It was possible to produce a product with an iodine number equal to 745 mg iodine per gram carbon. The study revealed that it is possible to tune the pore structure of "Smartie" coke derived activated carbons by changing the activation device and systematically changing the activation conditions. It was possible to obtain products ranging from a predominantly microporous structure to products with a predominantly mesoporous structure. Unfortunately, in comparison to commercially available activated carbons, the total surface areas were still too low and it will be necessary to perform further investigations focused on increasing the total surface areas. The gold adsorption tests performed on the activated carbon compared well to those of activated carbon currently in use in the gold industry.