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Title: Experimental Evaluation of Dual-Opposed Jet Mixer Pump Performance for Slurry Mixing

Abstract

Million-gallon double-shell tanks at Hanford are used to store transuranic, high-level, and low-level radioactive wastes. These wastes consist of a large volume of salt-laden solution covering a smaller volume of settled sludge primarily containing metal hydroxides. These wastes will be retrieved and processed into immobile waste forms suitable for permanent disposal. Retrieval is an important step in implementing these disposal scenarios. The retrieval concept evaluated is to use submerged dual-nozzle jet mixer pumps with horizontally oriented nozzles located near the tank floor that produce horizontal jets of fluid to mobilize the settled solids. The mixer pumps are oscillated through 180 about a vertical axis so the high velocity fluid jets sweep across the floor of the tank. After the solids are mobilized, the pumps will continue to operate at a reduced flow rate producing lower velocity jets sufficient to maintain the particles in a uniform suspension (concentration uniformity). Several types of waste and tank configurations exist at Hanford. The jet mixer pump systems and operating conditions required to mobilize sludge and maintain slurry uniformity will be a function of the waste type and tank configuration. The focus of this work was to conduct a 1/12-scale experiment to develop an analyticalmore » model to relate slurry uniformity to tank and mixer pump configurations, operating conditions, and sludge properties. This experimental study evaluated concentration uniformity in a 1/12-scale experiment varying the Reynolds number (Re), Froude number (Fr), and gravitational settling parameter (Gs) space. Simulant physical properties were chosen to obtain the required Re and Gs where Re and Gs were varied by adjusting the kinematic viscosity and mean particle diameter, respectively. Test conditions were achieved by scaling the jet nozzle exit velocity in a 75-in. diameter tank using a mock-up of a centrally located dual-opposed jet mixer pump located just above the tank floor. Concentration measurements at sampling locations throughout the tank were used to assess the degree of uniformity achieved during each test. Concentration data was obtained using a real time in-situ ultrasonic attenuation probe and post-test analysis of discrete batch samples. The undissolved solids concentration at these locations was analyzed to determine whether the tank contents were uniform (≤ ±10% variation about mean) or nonuniform (> ±10% variation about mean) in concentration. Concentration inhomogeneity was modeled as a function of dimensionless parameters. The parameters that best describe the maximum solids volume fraction that can be suspended were found to be 1) the Fr based on nozzle average discharge velocity and tank contents level and 2) the dimensionless particle size based on nozzle diameter. The dependence on the jet Re does not appear to be statistically significant.« less

Authors:
;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1344659
Report Number(s):
PNNL-SA-116470
DOE Contract Number:
AC05-76RL01830
Resource Type:
Conference
Resource Relation:
Conference: ASME 2016 Fluids Engineering Division Summer Meeting (FEDSM2016), July 10-14, 2016, Washington, DC, II2:V002T10A002; FEDSM2016-7749
Country of Publication:
United States
Language:
English
Subject:
mixing; jet mixer pump; slurry; Newtonian; scaled testing; correlation

Citation Formats

Bamberger, Judith A., and Enderlin, Carl W. Experimental Evaluation of Dual-Opposed Jet Mixer Pump Performance for Slurry Mixing. United States: N. p., 2016. Web. doi:10.1115/FEDSM2016-7749.
Bamberger, Judith A., & Enderlin, Carl W. Experimental Evaluation of Dual-Opposed Jet Mixer Pump Performance for Slurry Mixing. United States. doi:10.1115/FEDSM2016-7749.
Bamberger, Judith A., and Enderlin, Carl W. 2016. "Experimental Evaluation of Dual-Opposed Jet Mixer Pump Performance for Slurry Mixing". United States. doi:10.1115/FEDSM2016-7749.
@article{osti_1344659,
title = {Experimental Evaluation of Dual-Opposed Jet Mixer Pump Performance for Slurry Mixing},
author = {Bamberger, Judith A. and Enderlin, Carl W.},
abstractNote = {Million-gallon double-shell tanks at Hanford are used to store transuranic, high-level, and low-level radioactive wastes. These wastes consist of a large volume of salt-laden solution covering a smaller volume of settled sludge primarily containing metal hydroxides. These wastes will be retrieved and processed into immobile waste forms suitable for permanent disposal. Retrieval is an important step in implementing these disposal scenarios. The retrieval concept evaluated is to use submerged dual-nozzle jet mixer pumps with horizontally oriented nozzles located near the tank floor that produce horizontal jets of fluid to mobilize the settled solids. The mixer pumps are oscillated through 180 about a vertical axis so the high velocity fluid jets sweep across the floor of the tank. After the solids are mobilized, the pumps will continue to operate at a reduced flow rate producing lower velocity jets sufficient to maintain the particles in a uniform suspension (concentration uniformity). Several types of waste and tank configurations exist at Hanford. The jet mixer pump systems and operating conditions required to mobilize sludge and maintain slurry uniformity will be a function of the waste type and tank configuration. The focus of this work was to conduct a 1/12-scale experiment to develop an analytical model to relate slurry uniformity to tank and mixer pump configurations, operating conditions, and sludge properties. This experimental study evaluated concentration uniformity in a 1/12-scale experiment varying the Reynolds number (Re), Froude number (Fr), and gravitational settling parameter (Gs) space. Simulant physical properties were chosen to obtain the required Re and Gs where Re and Gs were varied by adjusting the kinematic viscosity and mean particle diameter, respectively. Test conditions were achieved by scaling the jet nozzle exit velocity in a 75-in. diameter tank using a mock-up of a centrally located dual-opposed jet mixer pump located just above the tank floor. Concentration measurements at sampling locations throughout the tank were used to assess the degree of uniformity achieved during each test. Concentration data was obtained using a real time in-situ ultrasonic attenuation probe and post-test analysis of discrete batch samples. The undissolved solids concentration at these locations was analyzed to determine whether the tank contents were uniform (≤ ±10% variation about mean) or nonuniform (> ±10% variation about mean) in concentration. Concentration inhomogeneity was modeled as a function of dimensionless parameters. The parameters that best describe the maximum solids volume fraction that can be suspended were found to be 1) the Fr based on nozzle average discharge velocity and tank contents level and 2) the dimensionless particle size based on nozzle diameter. The dependence on the jet Re does not appear to be statistically significant.},
doi = {10.1115/FEDSM2016-7749},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2016,
month = 7
}

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  • Understanding how uncertainty manifests itself in complex experiments is important for developing the testing protocol and interpreting the experimental results. This paper describes experimental and measurement uncertainties, and how they can depend on the order of performing experimental tests. Experiments with pulse-jet mixers in tanks at three scales were conducted to characterize the performance of transient-developing periodic flows in Newtonian slurries. Other test parameters included the simulant, solids concentration, and nozzle exit velocity. Critical suspension velocity and cloud height were the metrics used to characterize Newtonian slurry flow associated with mobilization and mixing. During testing, near-replicate and near-repeat tests weremore » conducted. The experimental results were used to quantify the combined experimental and measurement uncertainties using standard deviations and percent relative standard deviations (%RSD) The uncertainties in critical suspension velocity and cloud height tend to increase with the values of these responses. Hence, the %RSD values are the more appropriate summary measure of near-replicate testing and measurement uncertainty.« less
  • Experiments were performed to support understanding mixing of radioactive waste stored in 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 clearingmore » 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 simulant and 59 to 67% in the low viscosity simulant. Percent solids suspended with a 15.2 m/s (50-ft/s) jet was 74 to 81% in the low viscosity simulant. 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 simulant.« less
  • Jet mixer pumps will be used to suspend and mix the solids that have settled on the bottom of many radioactive waste storage tanks at the Department of Energy`s Hanford Site in southeastern Washington. A series of twenty-six tests were conducted in a 1/25-scale mock-up using simulated waste. The capability of the single, centrally located mixer pump to suspend a layer of cohesive tank sludge simulant was quantified and correlated to both the mixer pump jet properties and the physical properties of the simulated sludge. The data suggest that sludge that owes the majority of its shear strength to cohesivemore » forces (rather than frictional forces) will exhibit a specific relationship between mobilization resistance and vane shear strength. Sludge that owes a greater fraction of its shear strength to frictional forces will mobilize more readily than predicted by the cohesive sludge correlation.« less
  • This paper discusses the use of computational fluid dynamics (CFD) methods to understand and characterize erosion of the floor and internal structures in the slurry mixing vessels in the Defense Waste Processing Facility. An initial literature survey helped identify the principal drivers of erosion for a solids laden fluid: the solids content of the working fluid, the regions of recirculation and particle impact with the walls, and the regions of high wall shear. A series of CFD analyses was performed to characterize slurry-flow profiles, wall shear, and particle impingement distributions in key components such as coil restraints and the vesselmore » floor. The calculations showed that the primary locations of high erosion resulting from abrasion were at the leading edge of the coil guide, the tank floor below the insert plate of the coil guide support, and the upstream lead-in plate. These modeling results based on the calculated high shear regions were in excellent agreement with the observed erosion sites in both location and the degree of erosion. Loss of the leading edge of the coil guide due to the erosion damage during the slurry mixing operation did not affect the erosion patterns on the tank floor. Calculations for a lower impeller speed showed similar erosion patterns but significantly reduced wall shear stresses.« less
  • A series of tests were conducted to evaluate the mixing performance of pulse jet mixers. A pulse-jet mixing system involves an array of pulse tubes with nozzles directed toward the vessel floor inside the mixing vessel. Fluid is expelled from the pulse tubes during the drive portion of the PJM cycle. Fluid refills into the pulse tubes during the refill portion of the PJM cycle. This cyclical process can be used to mix slurries. Concentration profiles as a function of location and elevation in the tank were taken during the pulse jet mixer cycle at several radial locations within themore » mixing vessel: at the center, near the wall, and half-way between the center and the wall. The data are being examined to determine how the time during the cycle affects the solids suspension and settling. Examples will be presented for several particle types, concentrations, and pulse-jet operating conditions.« less