High Temperature Tribological Testing of Coke Coupled with 3D Visualistion to Enhance Understanding of Coke Breakage and Link to Parent Coals

This project applied the approach developed during ACARP project C27017 “Influence of Elevated Temperature and Gas Atmosphere on Abrasion and Interface Properties in Blast Furnace and Pilot Oven Cokes” to examine coke abrasion resistance in-situ at temperatures of up to 950°C and in a controlled gas atmosphere using rotational tribological testing. The originality of this approach lay in the ability to apply tribological testing to the porous coke surface at elevated temperatures under a controlled inert or CO₂ reactive atmosphere. Coke wear characteristics were quantified via (i) the application of advanced microscopy techniques, and (ii) analysis of the coefficient of friction (COF) during tribological testing.

The project sought to investigate the differences in abrasion resistance between pilot oven cokes from single coals with varying properties to link in-situ abrasion resistance determined using tribological testing to the properties of the parent coals.

Two pilot oven cokes were primarily examined in this study, which were generated from single coking coals of similar rank but different petrographic composition. The two parent coals were sourced from different Australian coal measures.

We found that the COF and the severity of the wear as a function of temperature and gas atmosphere were markedly different between the two cokes. A mid-to-low vol, medium vitrinite coal from the Moranbah coal measures showed no statistically significant differences. Conversely, the more reactive coke with a higher parent coal inertinite content and sourced from the Illawarra coal measures showed clear differences.

This suggests that the reduction in abrasion resistance at elevated temperatures is accentuated in the coke with the highest coke reactivity index (CRI) and the highest content of inertinite maceral derived components (IMDC). Our research has shown that at room temperature, the IMDC show greater resistance to abrasion than the reactive maceral derived components (RMDC). This has implications for understanding the relevance of room temperature testing to the abrasion resistance of coke under practical blast furnace operation conditions.

A method using micro-CT image analysis was developed in this project to examine the wear path generated at the coke surface during tribological testing, to assess the extent of the abrasive wear by comparing the rendered micro-CT images before and after tribological testing. A colour gradient scale was used to aid the quantitative assessment. Results showed there was a notable increase in abrasive wear to this coke as the temperature was raised from room to elevated temperature.

It is suggested that coupling this method of analysis with 3D visualisation techniques in further work would provide a powerful approach to examine and quantify mechanisms of coke surface breakage and the microstructural and/or microtextural features responsible for the breakage.