8th International Congress on Science and Technology of Ironmaking - ICSTI 2018

The rising amount of injected through the tuyeres pulverised coal makes increasingly difficult its conversion within the raceway zones despite of numerous measures to improve gasification of coal particles. Unburnt particles can nevertheless be partly consumed outside the raceway by so called secondary conversion reactions. From this point of view, properties of char that leaves the raceway were in the focus of current study. Chars from two coals with the same grain size distribution were produced artificially in a laboratory furnace at pre-defined conditions in order to find out differences in char properties depending on reaction temperature and coal type. Next to chemical composition that revealed among others volatile yield, petrographic properties has been determined using an oil-immersion microscope. All char samples showed complete disappearance of liptinite phases whereas a significant increase of inertinite was determined with increasing reaction temperature. This effect was in correlation with volatile yield. Physical properties showed an extreme increase in specific surface area by transformation of coal to char which was determined using BET analysis. Microscopic analysis showed high porous particle whereas the average particle size remained almost unchanged and bulk density decreased. However, changes of physical properties were only immense in comparison to its parent coal. Activation energy was determined for coals and chars. A correlation of volatile matter and specific surface area could be identified. The artificially produced char was compared with char generated by injection trials using the MIRI plant simulation the raceway conditions.