Cluster formation of silica particles in glass batches during melting

The study describes the incorporation of solid silica into molten glass during glass-batch melting as a function of the grain size in the range from 5 to 275 µm. Whereas tiny grains formed a bubbly melt, very large grains formed slowly dissolving clusters. Silica grains are forced to clusters by rising bubbles. The impact of the silica grain size on the glass-forming melt viscosity, overall density, thermal conductivity, and compositional homogeneity, as well as the consequences of these effects on glass processing in melting furnaces, is discussed. A high-alumina borosilicate glass for nuclear waste vitrification was chosen for the study, but the authors believe that the observed behaviors also occur in the melting of commercial batches.