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Comportamiento termoplástico de los macerales de carbones coquizables y su implicación en las propiedades del coque

AutorGuerrero Costa, Adrià
DirectorGómez Borrego, Ángeles ; Díez Díaz-Estébanez, María Antonia
Fecha de publicación2017
Resumen[EN] Metallurgical coke is an irreplaceable raw material used for the production of iron and steel. The shortage and high price of premium coals for the production of high quality coke, technological developments for the replacement of coke in the blast furnace by other fuels and reducing agents, and commitment of the society to reduce greenhouse gas emissions have redirected the focus of research towards alternative technologies that allow the production of high quality coke while reducing its costs and gas emissions to the environment. These new methods involve the modification of coal blends and the incorporation, as secondary raw materials, of organic industrial waste and biomass, classified as zero emissions of CO2. Biomass and charcoal are products of great interest, the latter form a significant part of this work. Accordingly this work explores the addition of charcoal to coal blends for the production of coke and the production of Fe-Coque briquettes with unexpensive materials such as iron ore fines and coals with poor coking properties. In order to follow the modifications that coal undergoes during its transformation to coke, this doctoral thesis uses optical microscopy and other additional techniques to trace the transformations of coal macerals during the carbonization process, and to define their relation to their thermoplastic behavior with special emphasis on organic components, traditionally considered as inert.
In order to achieve this goal, coals typically used in the production of metallurgical coke of different rank, maceral composition, chemical and thermoplastic properties, and geographic origin, are characterized by scan analysis at maceral level. As a result a threshold of inertinite reflectance was established. This determines inertinite fusibility and varies with coal rank, reaching the minimum value for coals with a vitrinite reflectance of around 1.3%. From this determination it is concluded that in addition to the macerals traditionally considered as semi-reactive, a significant part of the fusinite also undergoes transformations during the coking process. A sub-series of coals has been selected for a more detailed study of the transformations of the macerals in stages critical for the carbonization process i.e., the pre-plastic, plastic and post-plastic stages and of the influence of the incorporation of controlled grain-sized charcoal on the development of coal thermoplastic behavior, and on the mechanical and textural properties of the resulting cokes. It was observed that the addition of up to 15% of fine-sized charcoal causes a suppression of fluidity and a decrease in the optical texture size of the coke matrix, and that the smaller the particle size of the charcoal, the greater this effect. In addition to the coal rank and plastic properties of vitrinite, the balance between the volume of reactive and inert components is a determining factor in the amount of the charcoal accepted by a blend. Charcoal prevents the growth of graphite structures and produces discontinuities that propagate at the inert matrix interface, causing an increase in CO2 reactivity and a deterioration of mechanical strength. In this study Fe-Coke self-reducing briquettes were successfully produced using fine-grained coals with poor coking properties and charcoal as carbon source. The briquetes treated at 1000°C achieved the complete conversion of the iron oxides to metallic iron. The incorporation of this type of Fe-Coke briquettes in the blast furnace allows the use of biomass and recycled coal fines, thereby contributing to a reduction of CO2 emissions and giving added value to their use in a sustainable integrated steel-making industry.
DescripciónTesis doctoral presentada en el Departamento de Energía de la Universidad de Oviedo, 2017.
Aparece en las colecciones: (INCAR) Tesis
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