Deterioration of Coke Strength by CO<SUB>2</SUB> Gasification at High Temperature

Post-reaction Strength of Catalyst-added Highly Reactive Coke

“…5, in the case of catalyst no-addition coke, CSR(WL 20 %, CO 2 /COϭ50/50) increases with decreasing temperature in the temperature range of 1 000 and 1 200°C. Nishi et al 12) showed that the coke strength after reaction (CO 2 /COϭ100/0) that stopped at a weight loss of 20 % increased slightly with decreasing temperature in the same temperature range as in our study. Our study showed that a similar tendency was observed in the gas composition closely resembling that in the thermal reserve zone in a blast furnace.…”

“…Moreover, they attributed the high post-reaction strength of low CRI coke to the assumption that the coke reaction occurred preferentially on the surface of the coke and that of high CRI coke to the assumption that CO 2 enters the inner part of the coke, which disperses the reaction through the entire particle. This comment is different from the view by Nishi et al 11,12) and Yamaguchi et al 9) attributed this difference to a difference in the reaction condition; in Yamaguchi's study the reaction was conducted at an increasing temperature and in Nishi's study the reaction was conducted at a constant temperature.…”

“…This suggests that as the reaction temperature decreases, CO 2 enters the inner part of the coke more, which disperses the reaction through the entire particle and makes the reaction degree gradient gentler. This implies that the reaction mode of the highly reactive coke produced by the post-addition of the catalyst to coke method becomes more homogeneous with decreasing the reaction temperature 9,11,12,17,18) and that this change helps to enhance the post-reaction strength.…”

“…It is also reported that at a higher reaction temperature the coke reaction occurs preferentially on the surface of the coke with the inner part of the coke lump being kept nearly unreacted. 10,12) Furthermore, it is reported that at a lower reaction temperature the reaction gas diffuses into the coke inside, 17) which makes the coke reaction mode more homogeneous. 18) Since the reaction temperature has a great effect on the reaction degree gradient inside the coke lump, it is important to study the effect of the reaction temperature on the post-reaction strength of the catalyst added coke.…”

“…[8][9][10] Nishi et al 11,12) proposed a coke structure that is resistant to breakage after reaction: the coke of which the reaction follows the unreacted-core reaction model (the coke with highly reactive carbon structure and low porosity, e.g. formed coke) and the homogeneous reaction model (the coke with less reactive carbon structure, high porosity and thick coke structure wall).…”