Abstract
An alkaline-side solvent extraction process was developed for cesium removal from Savannah River Site (SRS) tank waste. The process was invented at Oak Ridge National Laboratory and developed and tested at Argonne National Laboratory using single-stage and multistage tests in a laboratory-scale centrifugal contactor. The dispersion number, hydraulic performance, stage efficiency, and general operability of the process flowsheet were determined. Based on these tests, further solvent development work was done. The final solvent formulation appears to be an excellent candidate for removing cesium from SRS tank waste. waste. Based on the results of these tests, a new solvent was developed. Using the DCs values for the new solvent and the hydraulic performance and stage efficiencies seen with the original solvent, a new flowsheet was developed. The flowsheet calculations were guided by a new definition for process robustness that should ensure good operation in plant-scale centrifugal contactors over the normal range of process perturbations. Because of the high cost of the solvent, the conceptual design of a recovery system using process diluent was outlined. This system, which still needs to be tested experimentally, should keep solvent costs at a reasonable level. While further work needs to be performed, especially in the area of solvent degradation and polymerization, the work presented here shows that the Cs7SBT/150LT solvent is a very attractive candidate for removing and concentrating cesium from the SRS alkaline-side tank wastes. The three multistage tests reported here, as well as similar tests done previously, indicate that stage efficiencies for multistage 2-cm contactors range from 60 to 90% with the lower efficiencies occurring as O/A flow ratios move away from 1.0. This effect is attributed to the slug flow of the liquids in the interstage lines. Larger laboratory and plant-scale units, which have higher flow rates, do not exhibit slug flow in the interstage lines. Thus, for larger centrifugal contactors, stage efficiencies in multistage operation will be the same as that for a single stage, that is, 95 to 100% in a well-designed contactor.
Original language | English |
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Pages (from-to) | 743-766 |
Number of pages | 24 |
Journal | Separation Science and Technology (Philadelphia) |
Volume | 36 |
Issue number | 5-6 |
DOIs | |
State | Published - 2001 |
Funding
This work was supported by the U.S. Department of Energy through the Savannah River Technical Center and the Efficient Separations and Processing Crosscutting Program, Office of Science and Technology, Office of Environmental Management, under Contract W-31-109-Eng-38 with Argonne National Laboratory, managed by the University of Chicago, and Contract DE-AC05-96OR22464 with Oak Ridge National Laboratory, managed by Lockheed Martin Energy Research Corp.