Using Fractography, 3D Image Analysis and CGA to Investigate the links between Inertinite Fusibility and Coke Structure in Rangal Coals

Previous ACARP projects identified that coals of different ranks from different Australian coal measures (or with different dilatation characteristics) can exhibit a different sensitivity to the grind of the inert rich fraction (IRF). Some coals showed increasing coke strength with increasing fineness of the IRF and others (coals from the Rangal coal measures) showed the reverse trend. The study of these series, particularly those showing anomalous behaviour, was expected to provide insights into the fundamentals of the formation of coke and the development of coke strength which can then be used to improve coke quality prediction models.

Development of analysis techniques that characterised coals and cokes in more detail gave a potential avenue to revisit these grind series samples to further understand the anomalous behaviours observed. Coals A, B and C (a Rangal coal) were reanalysed using these techniques in this project's parent project C24057, and Coals D and E (both Rangal coals) were analysed in this study. Fractography was used to gain an understanding of the mechanisms behind coke breakage under physical load. Micro-CT imaging and 3D image analysis was used to analyse the coke structure for features important to coke strength and to estimate its plasticity and points of weakness. In parallel, Coal Grain Analysis (CGA), with component size data extraction, was used to analyse the coke oven feed coal used to make the cokes and determine if small and/or large fusible/infusible structures contribute to stronger coke.

No clear single factor was found to correlate with coke strength over the series of results. It is therefore speculated that for each coal and corresponding coke, different mechanisms were important for coke strength.