Ash Fusion Properties from Molecular Dynamics Simulation: Role of the Ratio of Silicon and Aluminum

Molecular dynamics simulations are adopted to investigate the effect of the ratio of silicon and aluminum (S/A) contents on ash fusion properties and to predict the theoretical melting points and viscosities. The melting points are identified by the variation of the volume and mean square displacement, while viscosities are calculated by the Green-Kubo formula. The melting point is determined to be higher for coal ash systems with higher S/A ratios. The analyses of the radial distribution function and oxygen contents are performed to illustrate the structural evolution during the melting process. The interactions of different types are analyzed to explain the trend of melting points for various S/A ratios. The main structural features during slag melting are found to be the conversion of the oxygen atoms from the tricluster type to the bridging type. The viscosities of the slag systems near melting points are determined to be correlated to the S/A ratio as well. The computational results from this work may provide new insight into the mechanism of slag tapping.