DOE OSTI2019
During processing in the Defense Waste Processing Facility (DWPF), the evaporation of sludge leads to large amounts of foaming. This foaming can cause a foam-over, which contaminates other parts of the facility, most importantly the condensate. Currently, the antifoam being used is not sufficient at more extreme pH values and relatively high concentrations are required to minimize foaming. This means that a foam-over is more likely in parts of the process where the pH moves away from the neutral point and antifoam is needed in large quantities to prevent such occurrences. Adding this antifoam can also double processing time. The current antifoam also degrades into flammable byproducts, which creates a hazard in the processing. There are two main ideas proposed in order to solve the problems with the current antifoam: A new antifoam; A mechanical solution (sprays, agitator, etc). The focus of this summer was to develop a new antifoam that works across a broader range of pH values, can be added in lower concentrations, and does not degrade into flammable byproducts. This solution was pursued by obtaining different superspreaders and antifoams from companies across the country in order to perform a series of tests on them; these tests include superspreader testing, Foamscan testing, boiling testing, and Sludge Receipt and Adjustment Tank (SRAT) and Slurry Mix Evaporator (SME) process testing. To begin testing, four different superspreaders were tested on their ability to spread. The four superspreaders include: Y-17112, Y-17309, Antifoam 747 (the old antifoam), and Silwet L77 (the main component in Antifoam 747). These superspreaders were tested across a range of pH values and concentrations from 100 ppm to 5000 ppm. After completion of the tests, the results indicated that Y-17112 spread across a wider pH range than the others, even at lower concentrations. This is ideal for developing a new antifoam, as the pH throughout processing in DWPF varies and the lower the necessary concentration, the less antifoam that must be added per cycle. In order to test whether or not the superspreaders work as an antifoam, they have to be tested on real foam. In order to test this, a foamy simulant similar to the foaminess of the sludge in DWPF needed to be developed. This required testing many different sludges and designing our own simulant with different concentrations of insoluble solids. Eventually, a simulant similar enough to what is seen in DWPF was identified. Each superspreader will be tested on the simulant at different pH values and at different concentrations. The simulant will be allowed to foam and small amounts of the superspreader will be added while the Foamscan software tracks the height of the foam column; this allows us to know if the superspreader decreased the foam or not. Next, boiling testing in the Foamscan will be completed. This is testing identical to the Foamscan testing at room temperature, only at boiling conditions similar to DWPF. After boiling testing, the superspreader that is deemed most successful will be tested in a real, scaled-down SRAT/SME cycle. This will ensure it works with all the real chemicals that are added in DWPF and that it will remain successful in all the conditions that it may face. After the SRAT/SME testing, a decision will be made on whether or not the superspreader is successful and it may or may not be chosen as the new antifoam for DWPF.
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗