The Effect of Viscosity and Solids on Slag Foaming

Abstract

Slag foaming is one of the most influential factors in maximizing the efficiency of electric arc furnace. The foaming behavior depends on multiple factors, including viscosity, gas flow rate, temperature, and slag composition. Basicity, defined as the ratio of basic to acidic oxides, directly influences viscosity, and thus, plays a crucial role in foaming performance. This study investigates the slag foaming height across a binary basicity in range of 1.50–3.41 and viscosities ranging from 102.88 to 564.29 mPa s⁻¹ at gas flow rates from 100 to 500 cm³ min⁻¹ and temperatures of 1550, 1600, and 1650 °C. Results show that foaming height correlates more strongly with viscosity than with basicity, as temperature modifies viscosity independently of composition. An optimal viscosity of 175.04 mPa s⁻¹ and a basicity of 3.41 shows the maximum foaming height in fully molten slags. When solid phases (i.e., MgAl₂O₄ or 2CaO·SiO₂) form, small fractions can stabilize or enhance foaming, while excessive solids increase viscosity and lead to foam collapse. These findings highlight the importance of viscosity control and phase stability in optimizing slag foaming behavior for industrial applications.