Approximately 4.3 kg of slurry from Hanford Tank AZ-101 were evaluated by the pretreatment processes of cross-flow filtration, washing, caustic leaching, and rinsing. The filterability was measured with a 0.1-mm sintered metal filter using a single-element, cross-flow filtration system. During testing, the permeate flux and slurry axial velocity, pressure, and temperature were monitored every 10 min. The slurry temperature was maintained at 258C + 58C, except during the elevatedtemperature leaching step. The test results show that cross-flow filtration provides excellent separation of solids and liquids, as evidenced by the permeate flux and the measured activity of nearly insoluble 241 Am. The average permeate flux measured was higher than the Waste Treatment Plant target of 0.014 gpm/ft 2 , and the average decontamination factor for 241 Am was 985,000 during testing.
This report focuses on filtration/leaching tests performed on two of the eight waste composite samples and follow-on parametric tests to support aluminum leaching results from those tests.The sample groups examined in this report were the reduction-oxidation (REDOX) sludge (Group 5) and S-saltcake (Group 6). The Group 5 waste was anticipated to be high in boehmite, requiring caustic leaching, whereas the Group 6 waste was anticipated to contain a significant fraction of water-insoluble chromium that required oxidative leaching. Project report WTP- (c) describes the homogenization, characterization, and parametric leaching activities before bench-top filtration/leaching testing of these two waste groups. Characterization and parametric data in that report were used to plan two filtration/leaching tests-one test with only Group 5 material and another test that blended Group 5 and Group 6.The initial Group 5 test focused on filtration testing of the waste and caustic leaching for aluminum in the form of boehmite, and its impact on filtration. The initial sample was diluted with a liquid simulant to simulate the receiving concentration of retrieved tank waste into the UFP2 vessel (from 4 to 6 wt% undissolved solids). Filtration testing was performed on the dilute waste sample and dewatered to a higher solids concentration. Filtration testing was then performed on the concentrated slurry. Afterwards, the slurry was leached and was then washed to remove aluminum from the waste. The leach was planned to simulate leaching conditions in the UFP2 vessel. During the leach, permeate samples were collected to measure the dissolution rate of aluminum in the waste. After the solution cooled down from the elevated leach, the leach liquor was dewatered from the solids. The remaining slurry was rinsed (a) SM Barnes, and R Voke. WTP-RPT-172, Rev 0 xviii and dewatered with caustic solutions to remove a majority of the dissolved aluminum from the leached slurry. It was planned that the concentration of the rinse solutions would maintain the solubility of the aluminum in the dewatered rinse solutions. Filtration tests were performed on the final slurry to compare to testing performed before the leach.The second test used a blend of the Group 5 and Group 6 waste. Because there was an insufficient quantity of solids present in Group 6 waste to achieve 20 wt% solids for the initial dewater process, the Group 6 waste was blended with Group 5 waste to provide a higher feed concentration for the initial dewater. The focus of this test was to examine how both wastes filtered and examine oxidative leaching of chromium in the Group 6 waste after caustic leaching aluminum in the Group 5 waste. Initially, Group 6 material was added to the testing skid and diluted with excess permeate present from homogenization. Filtration testing was performed and then dewatered to a system minimum volume. Group 5 material was then added to the concentrated slurry and dewatered further. Filtration testing was performed on the concentrated slurry and caustic l...
Because of limited availability of test data with actual Hanford tank waste samples, a method was developed to estimate expected filtration performance based on physical characterization data for the Hanford Waste Treatment and Immobilization Plant in Richland, Washington. A test with simulated waste was analyzed to demonstrate that filtration of this class of waste is consistent with a concentration polarization model. Subsequently, filtration data from actual waste samples were analyzed to demonstrate that centrifuged solids concentrations provide a reasonable estimate of the limiting concentration for filtration.
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