PNNL

Abstract

As glass batch is charged into an electric melter, a cold cap forms on the glass melt surface. Heat transfer to the cold cap from the molten glass below and the melter atmosphere above determines the melting rate. A mathematical model of the cold cap and the experimental kinetic data of the feed-to-glass conversion that were collected for several low-activity and high-level waste melter feeds allowed us to develop relationships between the internal structure of the cold cap, its properties, its thickness, and the internal heat transfer. This contribution shows the distribution of major crystalline phases and the cumulative evolution of gases within the cold cap. It also examines the temperature, conversion degree (in terms of silica dissolution), and the heating rate the melter feed is experiencing during the passage through the cold cap. Attention is paid to the effects of the profiles of temperature, conversion degree, density, and heating rate within the cold cap on the cold-cap bottom temperature and morphology, which are important for the computational fluid dynamics simulations of melters.