Relation between the viscosity and electrical conductivity of molten slag for coal gasification and their dependence on SiO2 content

Direct measurement of coal ash viscosity during coal gasification in slag-tapping gasifiers poses a considerable challenge. Molten slag with different viscosities (η) possesses various electrical conductivities (κ). This study explores the relation between η and κ as a potential method for evaluating slag viscosity during coal gasification. The role of SiO2, a major component in coal ash, in η and κ was clarified based on the characterization of structural units of aluminosilicates in the slag through Fourier transform infrared spectroscopy and Raman analysis. Results indicated that an increase in SiO2 addition caused a decrease of κ and an increase in the activation energies of both κ (Eκ) and η (Eη). In particular, when the addition was 2%, η exhibited a fluctuation, and when the addition was 6%, a decoupling was observed between η and κ. Such phenomena are intricately linked to the content of the SiO4 unit structure (Qn(Si)) and its polymerization degree within the melt structure, and η is less sensitive to structural alterations than κ.