Influence of elevated temperature and gas atmosphere on coke abrasion resistance. Part two: Blast furnace cokes.

• Abrasion resistance of near-matched blast furnace bosh and feed cokes was examined. • High temperature abrasion resistance of cokes was lower than that at room temperature. • Differences in abrasive wear between RMDC and IMDC were observed for the bosh coke. • Difference in RMDC and IMDC wear decreased with increasing severity of conditions. • Tribochemical wear of IMDC was observed during in-situ testing in a CO 2 atmosphere. In this second in a series of two papers, the results of tribological testing of surfaces of coke samples retrieved from an operating blast furnace were compared with those of the corresponding feed coke, to assess the impact of the conditions in the blast furnace on the abrasion resistance of coke. Tribological tests were carried out at temperatures of up to 950 °C under a controlled inert (argon) or reactive (CO 2) atmosphere. Coke wear characteristics were quantified via (i) analysis of the coefficient of friction (COF) during tribological testing, and (ii) the application of microscopy and imaging techniques to the abraded specimens. The blast furnace coke sample was from the underside of the cohesive zone and is referred to as bosh coke in this paper. A near-matched feed coke was also examined. Under ambient testing conditions, the bosh coke had a lower abrasion resistance than the unreacted feed coke samples, indicating that the conditions coke is subjected to during its descent in the blast furnace effectively reduces its resistance to abrasion. Increasing the measurement temperature to 950 °C lowered the abrasion resistance of both the reactive maceral derived components (RMDC) and the inertinite maceral derived components (IMDC) in both samples. The bosh coke RMDC showed more severe damage than the IMDC, using a subjective damage severity scale. The difference in damage severity between these two phases in the bosh coke was reduced as the severity of the tribological testing conditions increased from ambient to elevated temperature (950 °C) to a reactive CO 2 environment. Feed coke samples that had been pre-reacted with CO 2 displayed a mean COF over time trend that was similar to that obtained from the bosh coke samples. During in-situ testing in a CO 2 environment, tribo-chemical wear of the IMDC was detected, due to the surface of the IMDC reacting with the CO 2 in the atmosphere. The observed tribo-chemical wear was due to the indenter and the coke surface rubbing against each other in this CO 2 environment, resulting in the continuous formation and removal of reaction products. Similar trends in COF over time were observed for the bosh and feed cokes during in-situ reaction with CO 2. The substantial decrease in abrasion resistance in coke at high temperature suggests that abrasion may be a more significant degradation pathway for coke in the blast furnace than hitherto expected. [ABSTRACT FROM AUTHOR]