Sludge Batch 5 Simulant Flowsheet Studies

Abstract

The Defense Waste Processing Facility (DWPF) will transition from Sludge Batch 4 (SB4) processing to Sludge Batch 5 (SB5) processing in early fiscal year 2009. Tests were conducted using non-radioactive simulants of the expected SB5 composition to determine the impact of varying the acid stoichiometry during the Sludge Receipt and Adjustment Tank (SRAT) and Slurry Mix Evaporator (SME) processes. The work was conducted to meet the Technical Task Request (TTR) HLW/DWPF/TTR-2007-0007, Rev. 1 1 and followed the guidelines of a Task Technical and Quality Assurance Plan (TT&QAP) 2. SRNS-STI-2008-00024 Revision 0 vi SRAT cycle, but exceeded the process limit during the SME cycle at the highest acid stoichiometry (160%). All of the blend experiments were within the process limits throughout the SRAT and SME cycles. As DWPF will be processing blend sludge, hydrogen likely won't be an issue in DWPF processing but lower acid stoichiometries will minimize hydrogen generation. The nitrous oxide generation peak was relatively insensitive to acid stoichiometry and was relatively low due to the low starting nitrite concentration. Acid quantities and processing times required for mercury removal Mercury was added to the sludge simulant at the start of the SRAT cycle as mercuric oxide at approximately 2.5 wt% (solids basis) based on the expected composition of the SB5 batch and blend. Mercury was not added to the ARP simulant. Because of the high mercury concentration, the time at boiling was increased from 12 hours to 18 hours to allow sufficient time to strip mercury from the SRAT. Boiling flux was maintained at a scaled rate of 5,000 lb/hr so a total of 90,000 lb of steam flow in DWPF will be needed to remove 120 lb of mercury. Acid quantities from 115% to 160% resulted in satisfactory mercury removal with 18 hours of boiling time (including dewater and reflux time), with the exception of the two lowest acid stoichiometry runs with the blend simulant. ARP/MCU processing did not impact mercury reduction and removal. If DWPF experiences problems stripping mercury, increasing the acid stoichiometry is likely to improve mercury removal. Simulant testing does not simulate the DWPF heel so starting mercury concentrations will be lower in DWPF and shorter steam stripping times should be achievable. Acid quantities and processing times required for nitrite destruction Acid quantities from 115% to 160% resulted in satisfactory nitrite destruction with 18 hours of boiling. In all runs, the amount of nitrite present in the SRAT product was less than 100 mg/kg, well below the 1,000 mg/kg target. The longer boiling time and low starting nitrite concentration both helped to reduce the nitrite by the end of the SRAT cycle.

DWPF Sb6 Initial CPC Flowsheet Testing Sb6-1 to Sb6-4l Tests of Sb6-a and Sb6-B Simulants

“…The pH profiles of the four SB6-A runs in general matched profiles noted during previous CPC simulations 14 . As shown in Figure 2, the pH was lower for runs with higher acid additions.…”

Sludge Batch Supplemental Srat Runs Effects of Yield Stress and Cycle Time Increase

“…IC measurements of NH 4 + in the FAVC condensate, which is downstream of the scrubber and upstream of the Nafion dryer, showed negligible ammonium ion in the condensate despite the presence of large concentrations of NH 3 and NH 4 + , 925 ppm (just upstream of the scrubber) and 934 μg/mL (in scrubber solution), respectively; thus, it can be concluded that the ammonia scrubber worked efficiently.…”

“…Savannah River National Laboratory (SRNL) performed these supplemental runs as requested by Technical Task Request (TTR) 2 following the guidelines of a Task Technical and Quality Assurance Plan (TT&QAP) 4 . The R&D Directions are given in the notebook SRNL-NB-2010-00047.…”

DWPF Coal-Carbon Waste Acceptance Criteria Limit Evaluation Based on Experimental Work (Tank 48 Impact Study)

“…17 As shown in Figure 3-3 the pH of the runs was lower for runs with coal and little change in pH occurred during boiling in runs with coal. Formic acid decomposition during high acid, no coal runs resulted in a higher final pH.…”