Factors influencing coke abrasion resistance: Coal properties, test conditions and link to tumble drum indices

Abrasion is one of the key mechanisms by which coke undergoes degradation in the blast furnace. Abrasion in coke refers to its surface breakage, and it occurs when lumps of coke move against each other as they descend the furnace. In industry, abrasion is assessed using tumble drum testing. However, tumble drum indices do not provide a measure of pure abrasion; rather, different breakage mechanisms occur during the test, including volume breakage and asperity breakage. To this end, we previously developed an approach using tribological testing of coke specimens to examine their resistance to pure abrasive wear and linked the mechanisms by which abrasion took place to coke microstructural and microtextural features, and thereby the properties of the parent coal(s) used to make the cokes. The key objectives of this present study were to: (i) investigate whether correlations exist between abrasion resistance measured using tribological testing and conventional coke quality indices, namely tumble drum indices – which is one of the novel aspects of this work; (ii) link the mechanisms of wear to coke microtextural components and the rank and maceral composition of the parent coal or blend; (iii) conduct a preliminary evaluation of whether partially pre-reacting coke samples with H 2 O affects their abrasion resistance compared to pre-reacting samples with CO 2 . This last objective contributes to a broader research aim of improving understanding of the coke quality requirements for effective operation of hydrogen-enriched blast furnaces. Key findings of the present study include: Some positive correlation was observed between the coefficient of friction (COF) of a coke at the end of tribological testing under ambient conditions and its measured ASTM Hardness or I 600 . This trend is a tentative observation requiring further validation. In addition, the mechanisms of abrasive wear under ambient conditions were correlated with parent coal rank. For coke from mid-rank coal, the reactive maceral derived components (RMDC) appeared to have a high fracture toughness based on SEM image analysis. For coke from the high-rank coal, which showed a higher degree of RMDC anisotropy, the main mechanisms of abrasion were delamination and ploughing. Finally, increased abrasive wear was observed for the samples pre-reacted with H 2 O than for those pre-reacted with CO 2 . The impact of the different gasification conditions on all six cokes will be subject of a follow-up paper.