Onset of smoldering fires in storage silos: Susceptibility to design, scenario, and material parameters

Biomass fuels in large storage units are prone to self-heating and ignition causing smoldering fires. Here, the susceptibility of such ignition processes to parameters is explored through small-scale experiments. In a silo geometry, wood pellets samples of size 0.75 to 1.5 kg were heated from below to initiate smoldering, while the top was open, allowing convective exchange of gases between the porous sample and the surroundings. The thermally insulated sidewalls reduce the heat flow in lateral direction in a similar way that additional pellets material would do in a larger set-up. Thus, the present experimental set-up mimics a much larger system in lateral direction. After heating was terminated, the procedure led to self-sustaining smoldering or spontaneous cooling, depending on parameters.