Influence of composition of slag and carbonaceous materials on the wettability at the slag/carbon interface during pulverised coal injection in a blast furnace

Abstract

Study of slag/char interactions is essential to understand the behaviour of unburnt char within a blast furnace during pulverised coal injection. While slag/carbon reaction kinetics have been reported in the literature, limited work is reported on study of the wetting behaviour in these systems. In the present study, wettability of slag/carbon systems has been investigated by measuring the variation in dynamic contact angle at the slag/carbon interface with time, for different slag compositions and carbonaceous materials, at 1500°C. The influence of liquid and solid composition on wetting has been discussed. The concept of a modified slag composition present at the slag/carbon interface during the interaction is introduced due to the presence of ash in the carbonaceous material. The wetting behaviour is found to be a function of the composition of this modified slag. Increased silica content at the interface, that is lower basicity slags and higher silica bearing carbonaceous materials, result in an improved wetting in the slag/carbon systems, when the iron oxide content is low. This is attributed to the increased reduction of silica at the slag/carbon interface, and when the reaction slows down, to a decreased interfacial tension at the slag/carbon interface; these contribute to lowering the interfacial energy. For the high iron oxide bearing slag (31.52% Fe2O3), the wetting behaviour at the interface is dependent on the slag/iron interaction due to the deposition of the reduced iron at the interface.