Influence of Temperature on Carbon Dissolution of Cokes in Molten Iron

Abstract

Coke within the blast furnace not only supports the furnace bed and allows gas flow, it also carburises liquid iron. Although carburisation rates of iron by coke vary considerably between cokes, the factors controlling it have not been clearly identified. In this study the rate of carbon dissolution from two cokes prepared from Australian coals, and synthetic graphite, into liquid iron has been measured in the temperature range 1723–1823 K. The apparent activation energy, Ea, obtained for synthetic graphite (Ea=54 kJ mol−1) is in agreement with literature values. The observed Ea values for Cokes 1 and 3 (479 kJ mol−1 and 313 kJ mol−1 respectively) are an order of magnitude larger than those of synthetic graphite. This difference in activation energies is attributed to mineral matter in the coke limiting the interfacial contact area between the carbon source and liquid iron. The interfacial contact area is a function of mineral matter yield and composition, which in turn is a function of temperature. Therefore, as temperature decreases the slag/ash layer produced at the carbon/iron interface can increase in area and viscosity and thus hinder carbon dissolution and increase the apparent activation energy of dissolution.