Characterisation of Complex Coal Blends, and Methodology to Investigate Thermal Coals Based on Compositional Analysis

This project built on the outcomes from project C25049 (Fusibility of Coal Blends and Minerals in Coking coal) which successfully used Coal Grain Analysis (CGA) to characterise simple binary and tertiary coking coal blends and provide information on the maceral and grain type abundances for the individual coals in these blends and to also provide detail on the breakdown of inertinite into fusible and infusible inertinite for each coal. This project extended this capability to assess more complex blends.

The objectives of this project were to:

• Enhance the CGA system and to use the system to characterise complex coking coal blends and obtain quantitative information on each of the constituent coals;
• Investigate if mineralogical information provides a better understanding of the slagging and fouling attributes for single coals and blends used in the combustion process than does ash constituent information;
• From the data obtained from the selected thermal coal samples analysed for the second objective of this project, seek to obtain additional information to validate the optical mineral markers in the CGA system.

The results for this project were mostly based on the vitrinite reflectance of each individual particle. Therefore, for complex blends, in which the individual coals did not display significant overlap in vitrinite reflectance values, the system was able to provide accurate information on the proportions of individuals coals and their maceral and grain type compositions in the blend. However, for blends for which some of the coals had significant overlap in vitrinite reflectance values, the particles with close reflectance ranges would tend to cluster in same group. In addition, the particles which did not contain any vitrinite clustered into the unclassified group. The system was less successful in analysing this type of complex blend.

The information obtained for thermal coals, both individually and incorporated into blends, using combined technologies (CGA and SEM) provides an insight into whether observed differences in single thermal coals with different ash fusion temperatures are due to fundamental differences in mineralogy or other factors.