Characterization of Ferrous Burden Material for Use in Ironmaking Technologies
Research output: Thesis › Doctoral Thesis › Research
It is the rising demand for steel products with the simultaneous claim of a more cost-saving and environmentally friendly operation mode that makes the efficient use of raw materials a key factor of iron and steel making. Especially different direct and smelting reduction process routes, as an alternative to the predominant blast furnace route, have been developed and further enhanced. Within the research work for this theses a variety of industrial scale processed lump ferrous burden materials were investigated with the objective of characterizing a raw materials appearance and nature and subsequent describe the behaviour during the conversion to metallic iron. In order to do so, characterizing different ores, pellet brands and sinter samples, testing methodologies and procedures have been developed and executed in different lab scale testing facilities. The description of a materials ability of oxygen release and mechanical performance during reduction was at first executed at standardized process conditions and subsequently at varying conditions related to industrial scale processes concerning temperature and gas composition. These results could give a picture about the applicability of a material for different industrial scale process routes. It could be revealed that the investigated lumpy materials behave different as the testing conditions differ, especially pellet samples showed varying behaviour whereas sinter samples retained their good reducibility performance hardly depending on the testing conditions. However, the variation of single testing parameters revealed the influence of different gas oxidation potentials as well as the effect of hydrogen addition to the reducing gas mixture. Combined with the morphological characterization and the structural evolution during reduction the results contributed on finding a correlation between raw material properties and their performance during the reduction process. It could be revealed that though the path of reduction – the stepwise reduction of the different oxides proceeds in a layerlike manner from the outer part to the core – remains the same, hydrogen distinctly changes the formation of metallic iron. Further the initial structural appearance of the material and the gangue amount and composition influence the final outcome as well as porosity and slag phase distribution are assumed to severely affect the reduction kinetics.