<p> Steam Exploded Pine Wood: Flame Speed and KST as a Function of Particle Size </p><p>Muhammad Azam Saeed, Nieves Fernández Áñez, Gordon E. Andrews*, Herodotos N. Phylaktou & Bernard M. Gibbs Energy Research Institute, School of Chemical and Process Engineering, University of Leeds, Leeds, LS2 9JT, UK</p><p>Abstract for oral presentation Biofuels are the best replacement of coal in the existing power generation plants for low carbon electricity. However, the low bulk density of biofuels with low heating values and the milling difficulties makes the use of biomass not a simple replacement for coal. The transport costs from the dominant source of the biomass in forests in the USA and Canada is a significant cost factor and increasing the bulk density of the biomass and reducing its water content is desirable. Thermal pretreatment of biomass using processes such as torrefaction or the present steam exploded biomass treatment, gives increased GCV, reduced water content and a more friable biomass that is easier to mill. A commercial thermally treated biomass, steam exploded biomass or ‘black pellets’, was investigated in terms of its flame propagation rate in a pulverised turbulent cloud of biomass, using the ISO 1 m 3 dust explosion equipment, modified to enable coarse fibrous biomass to be investigated. The ISO vessel was modified to enable the spherical turbulent flame speed to be determined. The ISO vessel was calibrated to determine the mean turbulent flame speed enhancement factor with the present new dust injector as 4.7. This enabled the laminar flame speed to be determined from which the burning velocity could be determined. In addition the explosoin reactivity parameter, the deflagration parameter, Kst was determined together with the peak pressure. In this work, steam exploded pine wood was split into different sized fractions to study the effect of particle size. Post explosion residues were analysed in comparison to original treated wood to understand the mechanism of flame development and the origins of much of the initial biomass not burning in the explosions. It was found that the fine fractions were more reactive with more mass burnt and higher Kst in comparison to coarser fractions. The results showed that the fine fraction had a peak reactivity near to the dust stoichiometric concentration, whereas for coarser fractions the peak reactivity was for very rich burnt dust mixtures. SEM imaging showed enhancement of fines in the pine wood sample after steam explosion treatment and active participation of fine with some partial burnt coarse particles in the post explosion residue. The Kst and flame speed were a strong function of the particle size but particles as large as 150 - 300µm with no fines present would still explode with an overpressure of Pm/Pi of 7. </p><p>Keywords: Steam Exploded Biomass, Flame propagation, Deflagration Index, Dust Explosoins, Biomass Combustion. </p><p>Acknowledgement: The authors thank the University of Engineering and Technology, Lahore, Pakistan for a Scholarship to MAS. The authors are grateful to the EPSRC Energy Programme (Grant EP/H048839/1) for financial support of part of this work. We would like to thank Zilkha biomass energy for supplying the processed biomass used in this research.</p><p>* Corresponding author: e-mail: [email protected] Tel: +441133432493. </p>