Modeling Feed-to-Glass Conversion in Electric Waste Vitrification Melters

This study focuses on modeling the feed-to-glass conversion process in waste vitrification melters, specifically those used for the vitrification of legacy nuclear waste at the Hanford site. It explores modeling approaches and feed characterization methods developed for understanding feed-to-glass conversion and predicting glass production rate in electric melters.<br/>The conversion process involves mixing nuclear waste with glass-forming and modifying additives, which are introduced into the melter as a feed. This feed forms a reacting material layer, known as the cold cap, that floats on the molten glass surface. The endothermic conversion processes within the cold cap, including water evaporation, conversion reactions, and sensible heating, consume thermal energy primarily supplied by the molten glass below. Thus, efficient heat transfer from the glass melt to the cold cap is crucial for optimizing the glass production rate.<br/>Using the developed models, we evaluate various strategies to enhance the melting rate such as increasing bubbling rates to boost melt convection, adjusting glass formulations to lower viscosity or increase thermal conductivity, and optimizing melter feed to prevent stable high-temperature foam formation in laboratory-scale, pilot-scale, and full-scale melters.