Organic tank safety project: Preliminary results of energetics and thermal behavior studies of model organic nitrate and/or nitrite mixtures and a simulated organic waste

Abstract

Appendix A -Thermal Behavior of and Evolved.Gases from 2 and 10 Mass% TOC Mixtures of Acetate, Citrate, EDTA, and HEDTA and Equimolar Sodium Nitrate and Nitrite as Measured by DSC, TGA, ARC, and IR . . . .

Use of organic functional group concentrations as a means of screening for energetics

“…It is shown that the amount of heat produced or o6served by the two instruments is a fraction of the maximum theoretical enthalpy. One possible explanation is that the reaction between the organics and the nitrate proceed, at least partially, by a less energetic reaction pathway than predicted by theory, which is consistent with previously obtained results (Scheele et al 1995).…”

“…For example, it has been shown that ammonia is among the gases released during decomposition .of organics such as sodium acetate and sodium HEDTA. (Scheele et al 1995). This is direct evidence of different dissociation reaction pathways being followed by many of these organics of interest than predicted by calculated reaction enthalpies, where primarily nitrogen and nitrous oxide gases are expected (Burger 1995).…”

Thermal reactivity of mixtures of VDDT lubricant and simulated Hanford Tank 241-SY-101 waste

“…The reaction observed with a maximum cooling rate near 150°C may correspond to the endothermic reaction observed by Scheele et al (1995) for a mixture of sodium nitrate and nitrite. The change in slope for the pressure results observed beginning between 140 and 150'C suggests that gas is released during this endothermic reaction.…”

“…This is based on the DSC-, TGA-, and ARC-observed behavior of the NqHEDTA and equimolar sodium nitrate and nitrite mixture presented in Figure 5.2 (Scheele et al 1995) During the ARC analysis, the absence of significant pressure increases that would be predicted based on Bryan's TGA (Figure 5.3) is likely due to differences in the drying method between our lOlSY/HEDTA and Bryan's preparation. SA Bryan dried his lOISY/HEDTA at 50'C under a vacuum for 2 to 3 days compared to our 2 to 3 weeks; Bryan did not dry the simulant to a stable (a) Provided by the courtesy of SA Bryan of PNNL and the PNNL Flammable Gas Project.…”

“…In a well-behaved system, anything less than 0 would be exothermic. Typically nitrate and nitrite oxidations of organics are complex reactions (Scheele et al 1995) and are therefore not well-behaved, so in the figures, exothermicity is indicated by a downward change relative to the immediately preceding data. Often TGA is used to provide additional information on the nature of the DSC-or DTA-observed reactions; our DTA is part of a simultaneous DTA and TGA instrument that observes enthalpy changes and mass changes on the same sample.…”