TY - JOUR
T1 - Behaviour of smoldering fires during periodic refilling of wood pellets into silos
AU - Fernandez-Anez, Nieves
AU - Katharina Meyer, Anita
AU - Elío, Javier
AU - Kleppe, Gisle
AU - Hagen, Bjarne Christian
AU - Frette, Vidar
PY - 2021/6/25
Y1 - 2021/6/25
N2 - The evolution of smoldering fires in biomass stored in lab-scale silos with additional fuel material supplied repeatedly, has been studied. The direct effects of the added material on the sample are: cooling, enhanced thermal insulation, and facilitation of more intense combustion at a later stage. This article focuses on the cooling, which leads to an almost instantaneous reduction in the combustion rate. Surprisingly, this reduction does not vary only with the amount of material refilled – but also depends strongly on the stage of the smoldering process. This demonstrates that the underlying smoldering processes merely to a certain degree are regularized by the periodic refillings. Quantitatively, the functional relationship between the refilled amount and the change in combustion rate caused by the refilling was determined. The results displays four regimes, that reflect different stages of the smoldering process at the time of the refilling. Using the Arrhenius equation, we find for one of these regimes an expression for the ratio of combustion rates (immediately after to immediately before the refill) as function of the amount of added material. This expression contains only one free (undetermined) parameter. We determine the value of this parameter from the data and demonstrate that this value is consistent with a simple model for how the sudden cooling occurs spatially in the sample.
AB - The evolution of smoldering fires in biomass stored in lab-scale silos with additional fuel material supplied repeatedly, has been studied. The direct effects of the added material on the sample are: cooling, enhanced thermal insulation, and facilitation of more intense combustion at a later stage. This article focuses on the cooling, which leads to an almost instantaneous reduction in the combustion rate. Surprisingly, this reduction does not vary only with the amount of material refilled – but also depends strongly on the stage of the smoldering process. This demonstrates that the underlying smoldering processes merely to a certain degree are regularized by the periodic refillings. Quantitatively, the functional relationship between the refilled amount and the change in combustion rate caused by the refilling was determined. The results displays four regimes, that reflect different stages of the smoldering process at the time of the refilling. Using the Arrhenius equation, we find for one of these regimes an expression for the ratio of combustion rates (immediately after to immediately before the refill) as function of the amount of added material. This expression contains only one free (undetermined) parameter. We determine the value of this parameter from the data and demonstrate that this value is consistent with a simple model for how the sudden cooling occurs spatially in the sample.
KW - Cooling
KW - Silo
KW - Smoldering
KW - Thermal runaway
KW - Wood pellets
UR - http://www.scopus.com/inward/record.url?scp=85109380330&partnerID=8YFLogxK
U2 - 10.1016/j.jlp.2021.104565
DO - 10.1016/j.jlp.2021.104565
M3 - Journal article
SN - 0950-4230
VL - 72
JO - Journal of Loss Prevention in the Process Industries
JF - Journal of Loss Prevention in the Process Industries
M1 - 104565
ER -