Influence of Elevated Temperature and Gas Atmosphere on Coke Abrasion Resistance. Part Two: Blast Furnace Cokes

Abstract

In this second in a series of two papers, we compare the results of tribological testing of surfaces of coke samples retrieved from an operating blast furnace 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 (CO2) 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 RMDC and the 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 CO2 environment.Feed coke samples that had been pre-reacted with CO2 displayed a mean COF over time trend that was similar to that obtained from the bosh coke samples. During in-situ testing in a CO2 environment, tribo-chemical wear of the IMDC was detected, due to the surface of the IMDC reacting with the CO2 in the atmosphere. The observed tribo-chemical wear was due to the indenter and the coke surface rubbing against each other in this CO2 environment. Similar trends in COF over time were observed for the bosh and feed cokes during in-situ reaction with CO2.

Keywords: Blast furnace, coke, coke abrasion, coke gasification, coke strength, in-situ high-temperature test