Effect of steam exploded treatment on the reactivity of pine wood

A commercial thermally treated biomass process known as ‘steam exploded biomass’ provided the treated biomass samples for this project together with the original yellow pine wood. The aim was to investigate the change in pulverised biomass reactivity. The steam exploded biomass is processed into pellets in the normal way and are known as black pellets (BP). The material was investigated using the Hartmann dust explosibility equipment. This enables the minimum explosion concentration (MEC) to be determined together with the initial rate of pressure rise and the flame speed and these latter parameters are measures of the mixture reactivity. BP was found to have a higher reactivity than the raw biomass with a much leaner MEC. A good correlation was found between the initial rate of pressure rise and the flame speed for the raw wood sample. Surface morphology was performed to investigate the effects of the steam exploded treatment. This showed the enhancement of the proportion of fines. The particle size distribution was determined and this confirmed the enhancement of the fineness of the treated sample. The enhanced reactivity of BP was found to be due to the greater proportion of fine particles which had a higher heating rate and a greater release of volatiles. The steam explosion treatment was found to be an effective pre-treatment in facilitating the combustion of renewable fuel and the main effect was that it was more easily milled, changes in the biomass chemistry was of secondary importance.