Interfacial phenomena occurring during iron/char interactions in a blast furnace

Using the sessile drop approach, interfacial reactions taking place in the iron/carbon interfacial region were investigated at 1 550 degrees C in a horizontal tube resistance furnace with an argon atmosphere. Two coalchars, labelled as 1 and 2 with respective ash concentrations of 10.88wt% and 9.04wt%, and electrolytically pure iron were used in this study. Liquid iron droplets were exposed to chars at high temperatures for times ranging between 1 to 180 min and the assembly was then withdrawn into the colder section quenching the droplet. To examine the time dependant growth of new phases formed in the interfacial region, FESEM and EDS investigations were carried out on the underside of the droplet, which effectively represents the iron/char interface. The transfer of carbon and sulphur into the iron droplet was also determined using a LECO Analyser. Interfacial regions for both chars showed a high occurrence of ash deposits, which were found to increase with time. Al, Ca, S, O, Fe were also detected in EDS analysis of the interface. However very low levels of Si were found in the interfacial region despite high concentrations of silica in the chars initially suggesting chemical reactions involving silica. After three hours of contact, carbon pick-up by liquid iron reached only 0.12wt% and 0.28wt% for Char 1 and Char 2 respectively, both of which were much below the saturation level of 5.6wt%. These results are discussed in terms of the formation of interfacial products, the consumption of solute carbon by reducible oxides and low intrinsic rates of carbon dissolution from non-graphitic Chars.