Factors Underpinning the Gasification Reactivity of Coke RMDC and IMDC with CO₂

Abstract

The reactivity of metallurgical coke is a key contributory factor to its integrity in the ironmaking blast furnace. Herein, the factors that influence the CO₂ gasification reactivity of individual coke inert maceral derived components (IMDC) and reactive maceral derived components (RMDC) were examined, including: Parent inertinite types, degree of microtextural anisotropy, accessibility of the IMDC; and ash chemistry.

Individual IMDC and RMDC components were formed by coking inertinite group concentrates (IC) and vitrinite group concentrates (VC), respectively. Cokes were also formed from head coals and by using different proportions of IC and VC in the coking blend. Coke lump and intrinsic gasification kinetics were compared for each case, where "intrinsic" refers to the gasification behaviour of powdered samples. The most influential factors on which the reaction rate was dependent were distinctly different between lump and powdered samples. The degree of isotropy of the carbon structure was the most important parameter controlling coke lump gasification kinetics with CO₂ at 1100 °C, followed by the basicity index of head coal. Conversely, intrinsic reactivity was closely correlated with microporosity.

Importantly, the isotropy of the carbon structure was not found to be a critical parameter controlling the intrinsic gasification kinetics up to the 40 % carbon conversion point. These results suggest that in the lump form where gas diffusion limits the reaction rate, carbon structure and catalytic effect of coke minerals play the dominant role in coke gasification. Such behaviour leads to a selective reaction of gas with IMDC in coke lumps due to the isotropy of carbon and greater association with minerals.