Recently, results of a 1998 sample have been obtained and the surrogate feed revised to incorporate the new sample results. Both surrogate compositions have been tested with no observed processing differences. The batch vitrification process includes the three distinct steps of drying, calcination and vitrification prior to draining the glass into a storage canister. The drying step removes the free aqueous fraction required to transfer the precipitated feed slurry to the melter and the chemically bound waters of hydration. The amount of time required to dry a single batch varies between 1 - 4 hours depending upon the total batch size and the volume of flush water used.
Water is the main constituent in the off-gas during the drying step.
Nitrous oxides and a small quantity of carbon monoxide and carbon dioxide also are evolved. The amount of time required to calcine a single batch is a function of the heating rate and the total batch size. Vitrification occurs as the oxides resulting from the calcination step begin to react with the 25SrABS glass-forming composition. The time to complete the vitrification step may include a hold period to fine the bubbles before the vitrified glass is drained from the melter into a stainless steel canister. Bubbles in the final product would not affect the product performance criteria of recoverability.