Molecular dynamics simulations of the molten CaO-K2O-SiO2 system to study viscosity of woody biomass ash slags

Abstract

Compositions in the CaO-K2O-SiO2 system have been simulated with molecular dynamics in order to elucidate aspects of structural characteristics that correlate to molten slag viscosity. Focus was placed on the structural characteristics of the Si and O atoms, which included pair distribution and coordination number functions, angular relationships, Qn values, and oxygen types. Principal component analysis was used to reveal correlations between reported viscosity values and attributes of the structural characteristics. The simulations indicated that silicate tetrahedral units were prevalent and angular and atomic mobility attributes between these units correlate with viscosity. Viscosity also tends to increase with increasing shares of Q3 or higher, and tends to decrease with increasing shares of Q2 or lower, as expected.