Systematic differences in the microstructure of cokes made from medium/high-reflectance Northern hemisphere and Australian coals

Cokes prepared from Northern Hemisphere (NH) and Australian coals (AU) were characterised by structural/textural parameters obtained using automated optical image analysis. Comparison of matched cokes from NH and AU with similar parent coal rank and amount of vitrinite revealed significant differences between their structural parameters.

The study showed that, NH cokes had coarser structure, including larger porosity pockets, coagulated nodes and connecting walls. However, AU cokes had more connections/walls per unit area which in total were thicker. Inert Maceral Derived Components (IMDC) in NH cokes were smaller, more rounded and less elongated. The IMDC boundary smoothness was higher in NH cokes. There are fewer voids within Reacted Maceral Derived Components on the IMDC boundary in NH cokes, and the average size of these voids is significantly larger. Porosity in AU cokes was more tortuous and there was less fine optically recordable porosity in NH cokes.

For all 26 structural parameters where the difference between NH and AU cokes was significant and where the correlation of each parameter with RMax obtained from a large set of Australian cokes was also significant, the difference was such that the structure of Australian cokes was corresponding to higher RMax than matched NH cokes.