Dissolution of carbon from coke and char in liquid Fe-C alloys

Abstract

Purpose: The aim of this paper was to study dissolution of carbon from carbonaceous materials of different origin with different morphology, microtexture and microstructure in the liquid Fe-C alloys. Design/methodology/approach: The dissolution of carbon from coke, char and glassy carbon in the molten Fe-C alloy (initial carbon concentration 2.46 wt.%) at 1350°C was measured and compared with that from graphite. The dissolution of carbon from demineralised coke and char in the Fe-C solution was also examined to study the effect of mineral matter on the carbon dissolution. Findings: The concentration of carbon in the Fe-C solution dissolved from graphite was higher than that from coke and char. Demineralisation of coke and char had a significant effect on the carbon dissolution. The concentration of carbon dissolved from demineralised coke and char in the Fe-C alloy approached the solubility of graphite in this alloy under the same conditions. Results obtained in this work confirmed that ash has a strong effect on the carbon dissolution. Research limitations/implications: Investigations in this paper were conducted at 1350°C. At higher temperatures; (1) the degree of coke and char graphitisation increases changing the microstructure of carbonaceous materials; (2) the ash can melt, and (3) some of the metal oxides in the ash can be reduced by carbon to the metal phase, thereby weakening the effect of ash on the carbon dissolution. Demineralisation of coke was incomplete; it reached 70-80% with some effect on the carbon dissolution. The effect of ash composition and further coke demineralisation on the carbon dissolution at higher temperature will be investigated in the future study. Originality/value: This study demonstrated that dissolution of carbon from coke and char was strongly affected by ash. Reactions of dissolution of carbon from coke and char in liquid Fe-C alloy reached a steady state within 1-2 hours. In this state, the coke/char – metal system was far from equilibrium. The “apparent” activity which can be assigned to carbon in the steady state is below one for graphite with significant implications for metallurgical processes.