(421e) Using Computational Fluid Dynamics with Experimental Validation to Predict Liquid-Solid Mixing in Vessels Equipped with Pulsed-Jet Mixers

The Columbia River in Washington State is threatened by the radioactive legacy of the cold war. Two hundred thousand cubic meters (fifty-three million US gallons) of radioactive waste is stored in 177 underground tanks (60% of the nation's radioactive waste). This waste is a product of 50 years of plutonium production for national defense. Bechtel National, Inc (BNI) has been commissioned by the U.S. Department of Energy to design and build a vast complex of waste treatment facilities to convert this waste into stable glass using a proven vitrification process.

The waste in these underground storage tanks is a combination of sludge, slurry, and liquid. Part of the engineering challenge for during processing is to verify that mixing systems in the plant vessels keep all solids in suspension. For various reasons, the mixing system chosen is one based on jet mixers. Specifically, these vessels use compressed air driven pumps to power what are known as pulsed-jet mixers (PJMs).

Computational Fluid Dynamics has been applied to the study and design of Pulse Jet Mixing systems at the Hanford Site Waste Treatment Plant since 2001. Several experimental studies have been commissioned by the Waste Treatment Plant project to understand the ability of PJMs to keep solids in suspension and determine levels of slurry blending. This work will present CFD models of these experimental platforms. These models are intended to benchmark the CFD for use in design analysis.

Eulerian-granular CFD models of a 15-inch and a 70-inch diameter test vessel will be presented. The tests were performed at just-suspended velocities and concentration measurements were recorded at various levels in the vessel. Time history comparisons between the experiments and CFD results will be presented along with other parameters intended to show how CFD can be used to predict suspension and blending.