Reactivity of petroleum coke to carbon dioxide between 1030 and 1180 K

Abstract

Measurements were made of the reaction rate of three sizes (2.9, 0.9 and 0.22 mm) of petroleum-coke particles with carbon dioxide over the temperature range 1018–1178 K, and at carbon dioxide partial pressures between 26 and 118 kPa. A limited number of similar measurements were made on samples of a commercial aluminium-smelting anode, an experimental anode, and AGKSP graphite. The materials were all reacted under conditions of chemical rate control alone: there were no rate limitations due to transport processes without or within the carbon particles. The order of the rate with respect to carbon dioxide concentration was found to be close to 0.6 for the petroleum coke and anode carbons, and between 0.6 and 0.8 for the graphite. Activation energies in the range 203–237 kJ/mol were found for petroleum coke; 187–237 kJ/mol for electrode carbon; and 293 kJ/mol for the graphite. For the petroleum coke, the order was found to be constant up to 45% burn-off and the activation energy essentially constant between 21 and 45% burn-off. The reactivity ϱ s , based on unit pore surface area of the petroleum coke at a carbon dioxide pressure of 101 kPa, can be represented by: ϱ s = α exp [− E (RT) ] . For the 2.9 and 0.9 mm particles, α = 6.1 / sx 10 6 g/m 2 min and E = 215 kJ/mol; for the 0.22 mm particles the respective values are 1.8 / sx 10 7 and 222. The reactivity ϱ of the commercial electrode on a weight basis was within the range of those of the coke and experimental electrode. For AGKSP graphite, values of ϱ s were close to those found by Walker and Raats 14.