<p>The Hanford site in eastern Washington state contains more than 210,000 m<sup>3</sup> of legacy tank waste awaiting vitrification to prepare it for long-term storage or disposal. To understand the vitrification process in a way that may help improve operations by optimizing the batch melting process within the Joule heated glass melters, computational fluid dynamics models of a laboratory-scale melter have been developed. In this work, the Reynolds-Averaged Navier Stokes equations are used to solve for the average flow using a rigid body motion dynamic fluid body interaction (DFBI) model. This model was used to study the effects of bubbling rates and cold cap dynamics on the heat transfer delivered to the cold cap, a quantity used for predicting batch melt rates. Previous modeling efforts used a pseudo-steady state approximation of the melter’s glass level, that is the cold cap height and glass pool depth were assumed to be fixed. However, the glass melters are actually operated under a semi-batch operation method wherein the batch is continuously fed but is not continuously withdrawn. The withdrawal of the glass into canisters or containers will occur via periodic air lifts. In addition, the large amount of forced convective bubbling may also affect the height and location of the cold cap as it is pushed around on the surface of the glass melt pool. The use of a DFBI six-degree-of-freedom representation for the cold cap is explored to account for the dynamic forces on the floating cold cap and its resulting motion.&nbsp; Rather than prescribing a fixed position of the solid cold cap, the DFBI model allows the cold cap to rise and fall as glass is added to or withdrawn from the melt pool. It also allows for the cold cap to respond to the forced convective bubbling occurring in the melt pool and move around on the glass melt pool surface. The DFBI methodology uses a fine overset mesh that interpolates between a coarser background and foreground mesh. This allows for movement of the floating body in response to the forces calculated at each time step. The heat flux delivered to the cold cap by the convective bubbling is studied as a function of the bubbling rate. These results are compared with the previously computed heat flux trends for a stationary cold cap.</p>

Effect of Floating Body Motion on Heat Flux to the Cold Cap in a Waste Glass Melter

Paper Proceedings: https://asmedigitalcollection.asme.org/POWER/POWER2021/volume/85109

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