Measurement of Offgas Species from Thermal Decomposition of Simulated DWPF Melter Feed.

摘要

A better understanding of the decomposition process in the DWPF melter is desired to improve the melter offgas flammability model. Antifoam in DWPF is of interest because its presence contributes to the flammability of the melter offgas via formation of flammable gas species. Simulant formic/nitric and glycolic/nitric flowsheet SRAT/SME (melter feed) products were studied at several antifoam concentrations. In addition, redox measurements were compared to the offgas generation data to aid in the overall understanding of the feed decomposition process in the DWPF. A new method for quantitatively measuring the offgas species from simulated DWPF melter feed during heating was used to measure the offgas as a function of temperature. Results indicated that the form of the antifoam (degraded, pristine, or a surrogate) had a negligible effect on the offgas composition (including H2 generation) or glass redox for the SB8 formic/nitric flowsheet. Antifoam concentration in the glycolic/nitric flowsheet feed had a negligible effect on the offgas composition (including H2 generation) and glass redox. The glycolic/nitric flowsheet feed had significantly less (approximately 14) total H2 generation in the offgas during melting compared to the formic/nitric flowsheet and is thought to be related to different reaction paths among the flowsheets The overall composition of the offgas was composed primarily of CO2, NO, H2, CO, N2O, N2, NO2, and CH4. CO2 and NO comprised approximately 80% of the total emitted offgas from the formic/nitric flowsheet feeds and approximately 90% of the total emitted offgas from the glycolic/nitric flowsheet feed. The SB8 formic/nitric flowsheet feed exhibited approximately equal concentrations of NO, N2O, and N2. In contrast, the glycolic/nitric flowsheet feed exhibited approximately 80% NO, and approximately 10% N2O and N2. Similarly, the SB6 formic/nitric flowsheet feed exhibited approximately 70% NO, and approximately 15% N2O and N2 with the exception that for the SB6 formic/nitric flowsheet feed processed in 1% O(sub 2) no N2 was measured but, approximately 10 % NO2 was measured. In all other feeds, 1-3% NO2 was measured. The overall feed composition appeared to have a significant effect on the offgas composition and resulting glass redox.