Influence of ash on mass transfer and interfacial reaction between natural graphite and liquid iron

Abstract

The interfacial reaction is a factor that plays an important role in governing the rate of many metallurgical processes. In the direct iron smelting process, interfacial reactions of carbonaceous materials, such as coals, with molten iron is one of the key factors that dictate the rate of carbon transfer from the carbonaceous materials into molten iron and establish a carbon concentrated melt to reduce iron oxide in the slag phase.

In the current investigation, wetting of natural graphite, which contains 8.8 pct ash, by iron was studied in a horizontal tube furnace at 1600 °C using the sessile drop approach to establish a fundamental understanding of the influence of ash on interactions between graphite and iron. The mass-transfer phenomena between the solid substrate and the iron droplet were studied by withdrawing the assembly at different time intervals. After the wetting experiment, the contacting surface of the iron droplet was observed by a field emission scanning electron microscope (FESEM). The components of the interfacial layer formed during the experiment were examined by energy dispersive spectroscopy (EDS). The change in the carbon and sulfur contents of the droplet at different time intervals during the wetting experiment was analyzed by a LECO carbon and sulfur analyzer. It was found that the formation of an ash interfacial layer between the carbonaceous materials and the liquid iron has a strong influence on the mass transfer and interfacial reaction.