H. Liaw, Y. Liou
Sep 1, 2020
Citations
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Influential Citations
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Journal
Process Safety and Environmental Protection
Abstract
Abstract In 2016, a serious accident involving a thermal explosion of o,o-dimethyl phosphoramidothioate (DMPAT) resulted in the death of one operator and the serious injury of another at a pesticide plant in Taichung, Taiwan. This study conducts a systematic thermal and flammability hazard analysis of DMPAT in order to better understand the decomposition and reaction events that led to the explosion. The temperature and pressure behavior of DMPAT were analyzed using a PHI-TEC II adiabatic calorimeter, while the thermal stability was investigated using a thermogravimetric analyzer/differential scanning calorimeter (TGA/DSC). The liquid and solid samples formed during the test and heating process were analyzed using attenuated total reflectance (ATR), while the gas phase compounds were examined by TGA-FTIR and pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS). The results indicate that, during the explosion, the vapors of DMPAT and its impurities partially oxidized in air and the resulting heat of the reaction elevated the temperature of the liquid DMPAT at the vapor liquid interface, which resulted in temperatures higher than the onset decomposition temperature. A significant decomposition of DMPAT then occurred, which released more heat and this brought about the decomposition of the remaining DMPAT. The result was a further rapid rise in the system temperature until the point where a thermal explosion occurred. This study gave evidence that combustion of decomposition products may occur alongside a thermal explosion of the main reactive material if the final temperature of the decomposition reaction exceeds the auto-ignition temperatures of the decomposition products, and sufficient air is available.