Determination of Spontaneous Ignition Behaviour of Biochar Accumulations

This study was conducted in order to determine the thermal susceptibility or spontaneous ignition behaviour of biochar accumulations so as to establish its critical values in terms of volume and temperature through Frank Kamenetskii theory of criticality and its respective methodology. Though biochar is considered a stable carbonaceous material, the fact that is often a very fine and light material, and contains a proportion of biochar dust mixed with larger particles, makes it susceptible to spontaneous ignition and risk of explosion during storage, transport and handling and hence, this study. Conclusions are made that biochar is prone to spontaneous ignition and its behaviour is enhanced by increase in stockpile size and ambient temperature. The study establishes that at temperatures of 11C and below, no self heating can occur to biochar samples even at maximum stockpile volumes and as temperature increases up to 40C, each temperature range is associated with a specific critical volume and these critical volumes reduces with increase in temperature. The study further indicates that at any temperature above 40C, spontaneous ignition is inevitable even at an accumulation of a smaller sample and therefore, a recommendation is made that temperatures for storage of biochar accumulations should be below 40C, while observing that accumulations stored at temperature greater than 11C, have specific critical volumes for a specific temperature range.