Explosion reactivity characterisation of pulverised torrefied spruce wood

Pulverised biomass is increasingly being used for power generation in 100% biomass plants or mixed with coal as a way of reducing greenhouse gas emissions. The fire and explosion hazards of pulverised wood and other agricultural waste materials have been recognised for some time. However, safety data for biomass are very scarce in the public literature, and non-existent for upgraded biomass products such as torrefied biomass. This is largely due to the challenges that biomass poses for explosion characterisation in the standard methods (1 m3 ISO vessel or 20 L sphere). The authors have developed and calibrated a new system for the 1 m3 ISO vessel that overcomes these challenges. In this work we present the first data in the open literature for the explosion characteristics of torrefied biomass. Results for untreated Norway spruce wood and Kellingley coal are also included for comparison. Flame speeds and post-explosion residue analysis results are also presented. Torrefied spruce wood was found to be more reactive than Kellingley coal and slightly more reactive than its parent material in terms of KSt, Pmax and flame speed. The differences between coal and biomass samples highlight that it should not be assumed that safety systems for coal can be applied to torrefied or raw wood materials without suitable modifications.