Ignition, self-heating and convection effects during the spontaneous decomposition of methyl nitrate

✍ Scribed by J.F. Griffiths; K. Hasegawa

• Publisher: Elsevier Science
• Year: 1982
• Tongue: English
• Weight: 756 KB
• Volume: 45
• Category: Article
• ISSN: 0010-2180
• DOI: 10.1016/0010-2180(82)90033-5

✦ Synopsis

The thermal decomposition of methyl nitrate at low pressures in a closed vessel is exothermic, and the resultant self-heating may lead to ign~on. The P-T a ignition boundary has been located, and the quasi-steady temperature excesses that are achieved throughout the slow decomposition region have been mapped using very fine thermocouples. These data have been used to assess the regime in which convection begins to augment heat transfer by thermal conduction: explosion at the highest pressures studied (4 kN m -2) is made more difficult because of convection. In all circumstances ignition does not occur instantly on gas entry. An induction time is observed and a substantial extent of reaction may occur during it; this always exceeds 10%, increasing markedly as vessel temperatures are raised.

When data for the location of the ignition boundary are combined with those from all previous studies, they span a wide temperature range (510-650K). The overall activation energy for reaction varies, and this is revealed in curvature of the graph for In (PIT 3) vs. 1/T obtained from all ignition data after normalization. The half-life for methyl nitrate decomposition decreases 1000-fold over the whole temperature range. In consequence, the mechanistic interpretation for a variation in overall kinetic parameters is that, whereas at low temperatures ignition instability is controlled by the rate of O-N bond fission, at high temperatures secondary reactions of molecular products of decomposition become important.