FOAM BEHAVIOR IN LIQUID FEO-CAO-SIO2 SLAGS

In many metallurgical processes foamed slags are used to create large surface areas for multiphase reactions to take place, leading to improved process kinetics, heat transfer and energy efficiency. However, there is still a lack of understanding of what controls the foamability of slags, and the maximum utilization of foams has not yet been reached. Slag foaming experiments were carried out using synthetic FeO-CaO-SiO2 slags at temperatures from 1200 to 1350-degrees-C. The experimental results show that the gas injection rate and the temperature have strong effects on the behaviour of slag foams. At low gas injection rates the physio-chemical properties of the slag control the foaming behaviour while at higher injection rates, the dynamics of the gas/slag/foam movements become increasingly important. Slag foaming data from several investigators have been reviewed and analyzed. The data and the observations are fairly consistent and in general agreement. For a constant CaO/SiO2 ratio, the slag foamability increases with decreasing FeO contents. Similarly, for slags with a constant FeO content, the foaminess increases with increasing silica contents or decreasing temperatures. However, for a fixed viscosity the foamability increases with increasing CaO/SiO2 ratio. Slag foams may be greatly stabilized by the addition of surface active species and/or by solid precipitates.