| Popis: |
High-level radioactive waste stored at the Hanford Site near Richland Washington will be retrieved, transported, treated, and concentrated prior to final vitrification. This waste, stored in million-gallon underground tanks, is to be retrieved and transported via pipeline to the treatment facilities at low solids loading. Concentration is a necessary step to remove transport fluid and supernatant liquid. Several techniques are available to concentrate slurries including settle/decant, filtration, and evaporation that all present unique challenges. Using evaporators to dewater sludge is time consuming and energy intensive; settle-decant is time consuming and requires use of large settling vessels; filtration is prone to clogging and caking. Improvements in slurry concentration capabilities are desirable to help minimize waste treatment costs. Here we investigate mesofluidic separation to concentrate slurries. This mesofluidic system uses a high void space, low pressure drop grid installed within an existing pipe spoolpiece. The grid spacing is configured to force solids to migrate to one side of the grid and fluid to migrate to the other side of the grid as the slurry flows within the pipe. The fluid component exits the process stream through a branch and can be reused for additional slurry retrieval and transport. The higher concentration slurry component remaining in the “express lane” then flows through a second “grid” to be further concentrated. Several grid inserts in series may be used to obtain the degree of solids separation required to support downstream processes. The concentrated slurry then becomes the process feed for vitrification. A series of experiments were conducted to evaluate the ability of the mesofluidic grid installed within the spoolpiece to concentrate particles within a size range of interest for radioactive fluid processing. Experiments evaluated the potential to operate units in series in two configurations: further concentrating slurry routed from the express lane and further solids removal of fluid routed from the permeate line. Both configurations yielded enhanced results: additional concentration or additional dilution. Test results are presented and applicability to process enhancements is described. |
