Effect of viscosity on dynamic evolution of metallurgy slag foaming

Abstract

The viscosity is of high significance for the dynamic evolution of slag foaming in the metallurgical processes. Through physical modelling, the dynamic evolutions of slag foaming with different viscosities were analyzed by characterizing the foam structure. Furthermore, the effects of viscosity on the characteristic parameters of dynamic evolution were investigated. The experimental results indicated that the slag foaming types evolved along Partial Foaming I → Entire Foaming → Partial Foaming II with increasing superficial gas velocity, while the bubble shape of the top layers gradually transformed from the spherical to nonspherical shape. Moreover, the rise in the slag viscosity decreased the critical superficial gas velocity between the various slag foaming types by hindering the bubble shape transformation. Despite constant injection of gas, the "foam pseudo-decaying"phenomenon was observed after the liquid level of the foamed slag reached its maximum, and this phenomenon exacerbated under the higher viscosity conditions. Under the various superficial gas velocity conditions, the effects of viscosity on the characteristic parameters of the dynamic evolution presented a considerable difference. Under a lower superficial gas velocity, the viscosity had no obvious effect on the foaming and the decaying rates, whereas, under a higher superficial gas velocity, the foaming and the decaying rates decreased significantly with increasing viscosity. The foaming height reached the peak value when the slag foaming developed into the Entire Foaming, and this foaming height is basically consistent with the theoretical peak value. The superficial gas velocity required to reach this peak value decreased with increasing viscosity.