Impact of reactive drying on physiochemical and comminution characteristics of agroforestry biomass

Prior to biomass gasification, the pretreatment process consumes substantial consumption of equivalent energy from feedstock, a careful trade-off is necessary among the costs of moisture removal, the power consumption for comminution, and the operational benefits of handling dried feedstock. This study focused on the reactive drying process of eucalyptus, corn stalks, and Phyllostachys edulis those were pretreated at a temperature range of 150 °C–200 °C under inert conditions. The physicochemical and comminution characteristics of three agroforestry biomass after reactive drying were comparatively analyzed, revealing the mechanisms behind the mechanical impacts of chemical changes. The results indicated that the reactive drying primarily involved moisture removal and slight depolymerization of hemicellulose. By analyzing FTIR, the removal of hydroxyl groups was attributed to the release of internal water (105 °C–160 °C) and the depolymerization of hemicellulose (160 °C–200 °C). Based on 13C NMR results, the reactive drying led to only minor changes in carbon structures, corresponding to the -CH3 carbon of the acetyl units of hemicellulose and the C-2,3,5 of carbohydrates. From a microscopic molecular view, the changes were attributed to the depolymerization of hemicellulose, which reduced the fibrous nature between particles.