Spontaneous ignition hazards in stockpiles of cellulosic materials: criteria for safe storage

The ambient temperature at which ignition is brought about in various sizes, shapes and masses of sieved bagasse pith was investigated on a laboratory scale. DELTA T-time and DELTA T-position profiles were obtained, and critical temperatures are determined to closer than 0. 5 K; this is the highest precision for location of the sub-critical/super-critical margin so far reported for any thermal ignition system. Such quality is a pre-requisite for quantitative extrapolation in order to predict the critical sizes for field stock-piles in normal climatic conditions. Scaling rules based on stationary-state, thermal ignition theory are used and comparisons of the results are made with real piles. The predictions are shown to grossly over-estimate the safe size of stock-piles, and the reasons for this discrepancy are discussed.