Flame propagation and burning characteristics of pulverized biomass for sustainable biofuel

One of the critical energy challenges, which our planet is confronting today, is how to curtail the reliance on fossil fuels for a sustainable environment. Biomass is a promising source of renewable energy for sustainable power generation compared to the conventional coal. However, they are hard to mill to finer size due to their fibrous nature. In this study, the size dependency on the flame propagation and burning characteristics of pulverized biomass is examined compared to coals. Modified Hartmann and 1-m3 explosion vessels were used to perform flame speed and explosion tests. Fine-sized particles propagated the flame with a flame velocity of 2.5 m/s for non-spherical-shaped particles compared to round-shaped lycopodium and corn flour. For coarse size particles, the flame speeds were measured to be around 1 m/s. The minimum explosion concentration was measured to be 0.2–0.4 equivalence ratio for a size range of 40–200 μm and higher for larger particle sizes. Reactivity data showed functional correlations for selected biomass and coal samples. SEM images of post-explosion residues showed incomplete combustion of bigger particles and formation of the cenosphere because of siliceous contents. The study findings concluded that the fine-sized particles of biomass had higher fire/explosion risk due to greater burning characteristics and it could only be replaced with conventional coal after assessing their combustion data by reliable methods.