Computational Fluid Dynamics Simulations of Glass Vitrification Refractory Coupon Tests - 23252

The Waste Treatment and Immobilization Plant (WTP) at the Hanford site is nearing the start of the Direct-Feed Low-Activity Waste (DFLAW) operations. DFLAW is destined to convert a pretreated low activity waste portion of the 56 million gallons of tank waste into a stable solid glass. In the subsequent decade completion of the High-Level Waste (HLW) Facility is anticipated. Sustained operational missions of both LAW and HLW melter facilities are expected over multiple decades. In high temperature glass melters, the refractory lining corrodes over time, which could potentially be an issue for longer term operations, this refractory corrosion is higher at the level of the glass-air interface due to surface tension driven flow. The glass viscosity, melt pool temperature, and glass chemical composition all impact the rate at which the refractory corrodes. This rate is important to quantify for the various waste glasses to be produced at the WTP since the integrity of the refractory should not be a limiting factor affecting the lifetime of the melter. To this end, a series of glasses representative of the first batches of waste glass produced by the WTP will be melted in small-scale crucibles with sample coupons of the refractory liner inserted. The refractory that is utilized for the molten glass pool portion of the WTP is Monofrax^R K-3, a high chromium oxide fusion-cast refractory that was also used in the Defense Waste Processing Facility (DWPF) and the Durametler pilot-scale melters. The corrosion of the K-3 is measured in the melt and at the melt-line (or neckline), the glass-air interface where surface tension driven flow can greatly increase the corrosion rates. To assist with experimental design and validate the implementation of a corrosion model in the full-scale melter, computational fluid dynamics (CFD) simulations of the small scale crucible tests were performed. The bubbling that occurs in the small-scale crucible is initially validated here with a model that uses silicone oil at room temperature. The viscosity of the oil ranges from 1 to 100 Pa.s, which corresponds to operating glass pool temperatures near 1150 deg. C down to idling temperatures near 950 deg. C. The simulation results show good agreement with the bubble sizes that form during experiments. CFD modeling of the crucible setup was used to determine bubbling characteristics to match the range of near-wall velocities expected in the full-scale WTP. This study presents the initial CFD modeling results, corrosion testing plan, and a preliminary example of the corrosion testing. When fully completed, the results from the corrosion tests will be used to create a corrosion model that can be implemented into the CFD code and validated at the small crucible-level scale. When that is complete, the corrosion model can be implemented into the full-scale CFD model for prediction of corrosion in the actual WTP. (authors)