Sulfur Partitioning During Vitrification of INEEL Sodium Bearing Waste: Status Report Page: 29 of 65
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2.4.2 TGA/DTA/Evolved Gas Analysis
Using a TA Instruments 2960 TGA/DTA, simultaneous TGA and DTA were performed on the dried
SBW-4 feed (35 mass% waste loading) to provide additional insight into the temperatures and gases
evolved at each of the reactions during the conversion of the SBW melter feed material to a glass product.
Samples were analyzed to temperatures greater than 1150 C at heating rates of 1, 5, and 25 C in an
atmosphere of He/2%Ar. The TGA and DTA results as a function of temperature show the temperatures
where major reactions occurred and the weight loss associated with each reaction.
The gas that evolved during the TGA/DTA run made at 5 C min was analyzed by gas
chromatography-mass spectrometry (GC-MS) using a Hewlett Packard model 5890 GC and a model 5971
MS. The GC's Pora PLOT Q column was maintained at 90 C. The inlet pressure was 6.1 psig, and a
corresponding backpressure regulator was set at 6.1 psig (to avoid baseline upsets). GC injections of 0.5
mL were made once a minute by a valve rotator. A sweep gas of 2% Ar in He was used at a flow rate of
50 mL/min. The gases that were monitored quantitatively included 02, CO2, CO, SO2, NO, N20, and
CH4. The GC-MS results obtained from the SBW-4 feed (35 mass% waste loading) are summarized in
Figure 2.5. No SO2 was detected during the course of this run.(') Due to the size of the sample (a few
milligrams), the final glass was not chemically analyzed. Figure 2.6 compares the mass loss (determined
by TGA) and total measured off-gas generation rates for the measurement as a function of temperature.
1400
1200
c 1000
o 800 0
Co2
600
400 NO
0
200
20
0
0 200 400 600 800 1000 1200
Temperature ( C)
Figure 2.5. SBW-4 Feed (35 mass% waste loading) Off-Gas Test Results
() The fraction of total sulfur that must be evolved for SO2 concentration to be above the GC-MS
detection limit has not been fully determined; however, initial estimates indicate it to be a significant
fraction (see Section 4.3).2.7
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Darab, John G.; Macisaac, Brett D.; Russell, Renee L.; Smith, Harry D. & Vienna, John D. Sulfur Partitioning During Vitrification of INEEL Sodium Bearing Waste: Status Report, report, July 31, 2001; Richland, Washington. (https://digital.library.unt.edu/ark:/67531/metadc723302/m1/29/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.