Self-heating Behavior and Management of Torrefied Biomass Pellets in Outdoor Storage

Torrefied biomass pellets (TBP) may carry the risk of spontaneous combustion during storage. Understanding the self-heating behavior and spontaneous ignition characteristics of TBP is important for the establishment of storage guidelines for TBP. This study conducted outdoor storage tests of approximately 1500 t of TBP and measured the temperature changes within TBP stockpiles. Spontaneous ignition tests of TBP, bituminous coal, and sub-bituminous coal were conducted using a quasi-adiabatic spontaneous ignition tester (SIT). The outdoor storage tests showed that the temperature of TBP stockpiles rose from 293 to 313 K in about 15 days. However, the SIT results did not match the findings of the outdoor storage test because TBP heated up more slowly than the bituminous coal. Therefore, this study revealed that the specific surface area must be considered when comparing TBP and coal in the SIT. Monitoring of temperatures over time and adequate actions are important when temperatures exceed 313 K during outdoor storage of TBP.