skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Physical Modeling of Spinel Crystals Settling at Low Reynolds Numbers

Abstract

The crystallization of large octahedral crystals of spinel during the high-level waste (HLW) vitrification process poses a potential danger to electrically heated ceramic melters. Large spinel crystals rapidly settle under gravitational attraction and accumulate in a thick sludge layer that may partially or completely block the glass discharge riser of the melter. The settling of single particles of different sizes and the motion of hindered settling front of different particle volume fraction suspensions were studied in stagnant, transparent-silicone oils at room temperature to help predict the settling behavior of spinel crystals in the riser. The dimensions and terminal settling velocities of single particles were measured using an optical particle-dynamics-analyzer. The data yielded an experimental shape factor for glass beads that differed only 0.73% compared to the theoretical shape factor for a perfect sphere. The experimental shape factor for the spinel crystals was smaller than that of the beads given the larger drag force caused by the larger surface area to volume ratio of the octahedral crystals, but matched the theoretically predicted value to within 10%. In the hindered settling experiments, both the glass bead and spinel suspensions were found to follow the predictions of the Richardson-Zaki equation with higher particlemore » volume fractions settling at a slower rate. Particle concentration profiles obtained from color threshold analysis (CTA) indicated that for a given volume fraction the rate of clarification increases with an increase in settling vessel angle with respect to the vertical as predicted by the Ponder, Nakamura and Kuroda (PNK) model. The Stokes’, Richardson-Zaki and PNK equations can adequately predict the accumulation rate of spinel crystals in the vertical or inclined glass discharge riser of HLW melters« less

Authors:
;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1004833
Report Number(s):
PNNL-SA-67696
EY7144147; TRN: US1101012
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Journal of Young Investigators, 19(18):2-26
Additional Journal Information:
Journal Volume: 19; Journal Issue: 18
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; CERAMIC MELTERS; COLOR; CRYSTALLIZATION; DIMENSIONS; GLASS; REYNOLDS NUMBER; SHAPE; SIMULATION; SLUDGES; SPINELS; SURFACE AREA; VITRIFICATION; WASTES; Settling; Spinel; High-level Waste

Citation Formats

Schaible, Micah J, and Matyas, Josef. Physical Modeling of Spinel Crystals Settling at Low Reynolds Numbers. United States: N. p., 2009. Web.
Schaible, Micah J, & Matyas, Josef. Physical Modeling of Spinel Crystals Settling at Low Reynolds Numbers. United States.
Schaible, Micah J, and Matyas, Josef. 2009. "Physical Modeling of Spinel Crystals Settling at Low Reynolds Numbers". United States.
@article{osti_1004833,
title = {Physical Modeling of Spinel Crystals Settling at Low Reynolds Numbers},
author = {Schaible, Micah J and Matyas, Josef},
abstractNote = {The crystallization of large octahedral crystals of spinel during the high-level waste (HLW) vitrification process poses a potential danger to electrically heated ceramic melters. Large spinel crystals rapidly settle under gravitational attraction and accumulate in a thick sludge layer that may partially or completely block the glass discharge riser of the melter. The settling of single particles of different sizes and the motion of hindered settling front of different particle volume fraction suspensions were studied in stagnant, transparent-silicone oils at room temperature to help predict the settling behavior of spinel crystals in the riser. The dimensions and terminal settling velocities of single particles were measured using an optical particle-dynamics-analyzer. The data yielded an experimental shape factor for glass beads that differed only 0.73% compared to the theoretical shape factor for a perfect sphere. The experimental shape factor for the spinel crystals was smaller than that of the beads given the larger drag force caused by the larger surface area to volume ratio of the octahedral crystals, but matched the theoretically predicted value to within 10%. In the hindered settling experiments, both the glass bead and spinel suspensions were found to follow the predictions of the Richardson-Zaki equation with higher particle volume fractions settling at a slower rate. Particle concentration profiles obtained from color threshold analysis (CTA) indicated that for a given volume fraction the rate of clarification increases with an increase in settling vessel angle with respect to the vertical as predicted by the Ponder, Nakamura and Kuroda (PNK) model. The Stokes’, Richardson-Zaki and PNK equations can adequately predict the accumulation rate of spinel crystals in the vertical or inclined glass discharge riser of HLW melters},
doi = {},
url = {https://www.osti.gov/biblio/1004833}, journal = {Journal of Young Investigators, 19(18):2-26},
number = 18,
volume = 19,
place = {United States},
year = {Tue Aug 04 00:00:00 EDT 2009},
month = {Tue Aug 04 00:00:00 EDT 2009}
}