Investigation of Slag Compositions and Possible Relation to Furnace Operation of a FeSi75 Furnace

Slag samples from a submerged arc furnace producing FeSi75% have been collected, and the slag composition was determined using electron probe micro analyzer (EPMA). The samples were collected at the end of the tapping runner, at the top layer of the charge and from the electrode above charge level while the furnace was running or shortly after a stop (< 2 hours). The slag samples from the tapping runner mainly consisted of SiO2, Al2O3 and CaO. The viscosity of the samples was calculated and found to be between 1.9 to 6.6 poise at 1800 ˚C under normal tapping conditions. A slag sample that was reported to be from a visually high viscosity slag was found to contain double the amount of SiO2 compared to the other slag samples taken during normal tapping conditions. It was observed an indication of a correlation between the amount of CaO and increasing furnace power, while the amount of SiO2 in the slag indicated a decrease with increased furnace power. The amount of Al2O3 did not show a significant correlation with the furnace power. Samples from the electrode and the charge surface showed a slag phase consisting of mainly SiO2 and iron oxide. Some metal droplets were also observed on the electrode and the charge surface. This could either indicate a high temperature at the charge surface, or that material from further down in the furnace has been pushed upwards during operation.