Solids Mobilization and Suspension by Dual Opposed Mixing Pumps

Experiments were performed to support understanding mixing of Tank 241-SY-101 at the Hanford Site in Washington State. These experiments were conducted at 1/12 scale and modeled the tank and proposed mixing pump. The tests investigated solids mobilization and suspension for jets rotated in fixed increments about the tank centerline. Flow visualization tests showed that the supernatant layer was generally too cloudy for effective visualization. Observations of the settled solids interface during a start-up transient showed that the mixing action was always confined within the slurry layer. A 4.57-m/s (15-ft/s) jet velocity was not capable of clearing settled sludge off the tank floor all the way to the tank wall and produced a stratified flow field at steady state; 7.62-m/s (25-ft/s) and higher jet velocities always circulated solids to the tank surface. During the operating parameter tests with jets rotated at fixed increments, the slurry interface rose more slowly than for the fixed location jets. Solids suspension was more effective for the rotated jets than for the fixed location jets. Percent solids suspended with a 7.62-m/s (25-ft/s) jet was 66 to 72% in the high viscosity simuant and 59 to 67% in the low viscosity stimulant. Percent solids suspended with a 15.2 m/s (50-ft/s) jet was 74 to 81% in the low viscosity stimulant. A 7.62 m/s (25-ft/s) jet velocity was adequate to clear settled solids from the tank floor to the tank wall for both the low and high viscosity stimulant.