Study on the Risk Assessment of Spontaneous Ignition and of Perilla Oil Cakes Associated Activation Energy

Abstract

Perilla oil cakes are the residues of oil pressing processes, and used as fertilizers, feedstuff, food, etc. However, according to recent reports, perilla oil cakes often ignite spontaneously due to scorching heat, particularly in rice mills, general mills, and oil mills where large amounts of perilla oil cakes are stored. Thus, in this study, we attempted to elucidate the risk of spontaneous ignition of perilla oil cakes. For this purpose, thermogravimetry/differential thermal analysis (TG-DTA) was performed to identify thermal properties like weight reduction and heat generation, and spontaneous ignition was conducted for sample vessels of different thicknesses. The results showed that the ignition temperature of perilla oil cakes was 115 ℃ for the small (20 cm × 20 cm × 3 cm) vessel. The apparent activation energy associated with the critical ignition temperature was 60.74 kJ/mol. The ignition delay time and the time to reach maximum temperature were both found to increase with increasing vessel thickness. It was concluded that proper protection against heat must be in place because fire risk increases and spontaneous ignition can occur when large amounts of perilla oil cakes are accumulated.