Self-Sustaining Smoldering Characteristics of Corn Straw Powder Stacks

Biomass fuels are expected to play an important role in future energy consumption. Meanwhile, the fire and explosion of biomass are the have-to-face problems in its production, storage, and application process. This work aims to reveal the influence of stacking and ventilation parameters on the smoldering propagation process and provide guidance for the safe storage of biomass pellets. The effects of stacking density and air flux on the smoldering propagation process were studied experimentally, the variations of bed temperature with these two parameters were analyzed using the numerical simulation technique, and the conditions of self-sustaining smoldering were determined by the local energy analysis method. The results showed that the peak smoldering temperature of corn straw powder was between 500 and 520 °C, and the smoldering propagation velocity was between 10 and 30 mm/h. When the stacking density was changed from 56.89 to 99.56 kg/m³, the peak smoldering temperature change rate was about 2% and the smoldering propagation velocity decrease amplitude was up to 30%. Meanwhile, when the air flux was in the range of 0.2-0.8 m³/h, the small ones had little effect on the peak smoldering temperature, while the large ones helped the peak smoldering temperature reach 560 °C. Finally, the local energy analysis showed that the net heating rate was positive with energy accumulation in the system, the smoldering was self-sustaining, and the smoldering front propagated from the bottom to top. These results provide data support to facilitate the safe storage of biomass pellets.