The Profiles of Mass and Heat Transfer during Pinewood Conversion

Pulverised biomass is an alternative to fossil fuels recognized by both academic and industrial communities as it can effectively generate heat and electricity by different conversion processes in a carbon neutral manner. Among the forest biomass options, pine already represents 20% of planted forests as it has numerous industrial applications. This study concentrates on the conversion of pulverized particles of pinewood under fast and slow heating regimes in both air and nitrogen atmospheres. The results reveal that (i) at low heating rates the morphology of the pinewood particles (250 to 75 μm) remains practically with the same aspect during all conversion (ash ∼ 2 wt.%), while at high heating rates the network structure of the pinewood changes into a more spherical shape; (ii) during conversion, the temperature profiles show a single semi-plateau around 350 °C for pyrolysis and two plateaux for direct combustion around 300 and 470 °C, close to the maximum reaction rate and half-way of the conversion degree for the main reactions; and (iii) combustion reactivity of pinewood chars at 425 °C augmented from 35 min to 9 min, as morphology becomes more uniform and size reduces.