Initial Characterizations and SRAT Simulations of Four Sludge Matrix Study Simulants

摘要

The Savannah River National Laboratory (SRNL) initiated a sludge matrix study to evaluate the impact of changing insoluble solid composition on the processing characteristics of slurries in the Defense Waste Processing Facility (DWPF). Three compositional ranges were developed for three groups of elements in the waste. The first was high iron/low aluminum versus low iron/high aluminum. The second was high calcium-manganese/low nickel, chromium, and magnesium versus low calcium-manganese/high nickel, chromium, and magnesium. The third was high noble metals (Ag, Pd, Rh, Ru) versus low noble metals. These three options can be combined to form eight distinct sludge compositions. The sludge matrix study called for testing each of these eight simulants near the minimum acid required for nitrite destruction and at a second acid level that produced significant hydrogen by noble metal catalyzed decomposition of formic acid. Four simulants were prepared based on the four possible combinations of the Al/Fe and Mn-Ca/Mg-Ni-Cr options. Preliminary simulant preparation work has already been documented. The four simulants can be used for both high and low noble metal concentration testing and high and low acid testing. This report summarizes preliminary testing of each of the four simulants at low noble metals and low acid stoichiometry. The remaining matrix study tests are on hold. Chemically processed simulant was needed for U. S. Department of Energy-Office of Environmental Management and DWPF funded melt rate studies. Therefore, a preliminary assessment of the processing characteristics of the four sludge matrix simulants was completed using the low noble metal concentration option to meet this need. Sludge Receipt and Adjustment Tank (SRAT) testing was at low total acid stoichiometry (near the minimum acid end of the stoichiometric acid window). Composition and physical property measurements were made on the SRAT products. Updated values for formate loss and nitrite-to-nitrate conversion were found that can be used in the acid calculations for future sludge matrix process simulations.