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DOE OSTI · 1019028

GLYCOLIC-FORMIC ACID FLOWSHEET SLUDGE MATRIX STUDY

Lambert, D·Koopman, D
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Abstract

Testing was completed to demonstrate the viability of the newly developed glycolic acid/formic acid flowsheet on processing in the Defense Waste Processing Facility's (DWPF) Chemical Process Cell (CPC). 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 DWPF. Four sludge simulants were prepared to cover two compositional ranges in the waste. The first was high iron/low aluminum versus low iron/high aluminum (referred to as HiFe or LoFe in this report). The second was high calcium-manganese/low nickel, chromium, and magnesium versus low calcium-manganese/high nickel, chromium, and magnesium (referred to as HiMn or LoMn in this report). These two options can be combined to form four distinct sludge compositions. The sludge matrix study called for testing each of these four simulants near the minimum acid required for nitrite destruction (100% acid stoichiometry) and at a second acid level that produced significant hydrogen by noble metal catalyzed decomposition of formic acid (150% acid stoichiometry). 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 were used for high and low acid testing. Eight planned experiments (GF26 to GF33) were completed to demonstrate the viability of the glycolic-formic flowsheet. Composition and physical property measurements were made on the SRAT product. Composition measurements were made on the condensate from the Mercury Water Wash Tank (MWWT), Formic Acid Vent Condenser (FAVC), ammonia scrubber and on SRAT samples pulled throughout the SRAT cycle. Updated values for formate loss and nitrite-tonitrate conversion were found that can be used in the acid calculations for future sludge matrix process simulations with the glycolic acid/formic acid flowsheet. Preliminary results of the initial testing indicate: (1) Hydrogen generation rate was very low throughout all SRAT cycles. (2) The mercury concentration of the SRAT product was below the 0.8 wt% limit in all runs. (3) Nitrite in the SRAT product was <100 mg/kg for all runs. (4) Foaminess was not an issue using the nominal antifoam addition strategy in these tests. (5) The high aluminum sludges (LoFe, HM type sludges) were much more viscous than the Hi Fe sludges. At 100% acid stoichiometry, the SRAT products from the high aluminum sludges were very viscous but at 150% acid stoichiometry, the SRAT products from the high aluminum sludges were very thin. This makes the glycolic acid/formic acid flowsheet an improvement for processing more viscous sludges. (6) The pH of the SRAT products was from 2.7-3.1 for the 150% acid stoichiometry runs and 5.1-6.1 for the 100% acid stoichiometry runs, significantly lower than is typical of the baseline nitric acid/formic acid flowsheet.

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Lambert, D, Koopman, D. 2011-06-30. GLYCOLIC-FORMIC ACID FLOWSHEET SLUDGE MATRIX STUDY. https://doi.org/10.2172/1019028

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