Properties and CO2 reactivity of the inert and reactive maceral-derived components in cokes

The response of coke to gasification affects its degradation in the blast furnace. Coke gasification with carbon dioxide at high temperature is selective, with the inert maceral-derived component reacting more readily than the reactive maceral-derived component. Previous reactivity studies on carbonised vitrinite- and inertinite-rich fractions indicated that the amount of catalytic mineral phases control their reactivity. However, total Fe, Ca, K and Na from the ash chemistry were used as indicators of the abundance of catalytic material rather than the concentration of the catalytic mineral phases. Additionally, there is disagreement regarding the influence of micropore surface area and average carbon crystallite size on reactivity of the inert maceral-derived component and reactive maceral-derived component. Here we examine the influence of the abundance of the catalytic mineral phases on the reactivity of the inert maceral-derived component and reactive maceral-derived component, and also the influences of micropore surface area and average carbon crystallite size. Cokes from inertinite- and vitrinite-rich fractions prepared from four Australian bituminous coals were reacted with carbon dioxide at temperatures between 855 °C and 934 °C. The major factors that make inert maceral-derived component more reactive than reactive maceral-derived component at the initial stages were found to be the concentration of catalytic mineral phases and micropore surface area. The catalytic mineral phases identified in the coked inertinite- and vitrinite-rich fractions were metallic iron, pyrrhotite, troilite, wustite, magnetite and hematite. No Ca, K and Na catalytic mineral phases were identified in any of the studied cokes. The average crystallite height was not found to be a major factor controlling coke reactivity at the initial stages.

► Cokes prepared from maceral-enriched fractions were reacted with CO2.
► Coke reactivity was determined by surface area and catalytic iron phases.
► Lc was not a major factor controlling the reactivity of maceral-derived components.