Conversion of batch to molten glass, II: Dissolution of quartz particles

Quartz dissolution during the batch-to-glass conversion influences the melt viscosity and ultimately the temperature at which the glass forms. Batches to make a high-alumina borosilicate glass (formulated for the vitrification of nuclear waste) were heated at 5K min−1 and quenched from temperatures of 400 to 1200°C at 100K intervals. The batches contained quartz as a silica source, with particles ranging from 5 to 195μm in diameter. The content of unreacted quartz in the samples was determined with X-ray diffraction. Most of the fine quartz dissolved during the early batch reactions (at temperatures <800°C), whereas coarser quartz dissolved mostly in a continuous glass phase via diffusion. The mass-transfer coefficients were assessed from the data as functions of the initial particle sizes and the temperature. A series of batches were also tested that contained nitrated components and additions of sucrose, known to accelerate melting. While sucrose addition had no discernible impact on quartz dissolution, nitrate batches melted somewhat more slowly than batches containing carbonates and hydroxides in addition to nitrates.