Characterization of microstructure and strength of coke particles and their dependence on coal properties

Abstract

Microstructural features of coke particles are crucial for determining the performance of cokes in ironmaking blast furnaces. An analytical study was carried out to examine coke microstructure using image analysis. The microstructure parameters were correlated to the tensile strength of cokes. Coke properties were related to coal fluidity data based on Gieseler Plastometer measurements and other coal properties including quantitative mineralogy of coals using SIROQUANT analysis. Based on the microstructural data, a new modified microstructural parameter (S+) is proposed to characterize the heterogeneous nature of the physical structure of coke particles. The modified parameter was shown to have a good correlation with the tensile strength of coke as well as with the plastic range of the parent coals. Coal rank was shown to have a strong influence on the thermo-plasticity, with the results showing that there is an increase in both the maximum fluidity and plastic range of coals with increasing volatile matters of coal. The study highlighted the significance of coal mineral chemistry on coke particle characteristics from the observation that kaolinite-rich coals displayed a better correlation with the proposed modified parameter as well as the coke strength under the tested conditions. Stamp charging is also shown to have a positive impact on the microstructure as well as mechanical strength of cokes. This study has implications for the optimisation of the impact of coal chemistry and process conditions on coke quality.