Spontaneous Ignition of Bagasse Stockpiles in Thailand: A Fire Safety Concern
The sugar industry is confronted with the problem of safe bagasse storage over extended periods. In term of fire safety, there have been many instances that the spontaneous ignition promotes ignition inside a large bagasse stockpile and eventually the spontaneous ignition process develops to a flaming fire. This paper presents a method to determine a safe size for bagasse stockpile from spontaneous ignition. The kinetic parameters for spontaneous ignition of bagasse were estimated based on two methods: the Frank-Kamenetskii method and the crossing point method. The bagasse activation energies experimentally determined were ranged from 89 to 109 kJ/mol. Based on the calculated kinetic parameter values, the bagasse stockpile safe sizes for a sugar factory were estimated in term of graphical solutions. For a fixed surrounding temperature, as the bagasse stockpile radius or length increases, the height of the stockpile that spontaneous ignition does not occur decreases and approaches the asymptotic value as the stockpile radius or length approaches infinity. The graphical solutions showed that a bagasse stockpile with any radius or length stored with height below the asymptotic height for a given surrounding temperature was considered to be safe from spontaneous ignition. Applying the calculated activation energy of 89 kJ/mol, the asymptotic heights for bagasse stockpiles were 10.0 m, 7.8 m, and 6.0 m for surrounding temperatures of 40oC, 45oC and 50oC, respectively.