Machinery & Energetics

The article is devoted to the study of the thermal decomposition of milled and granulated pine wood at various pressures. The strength of the intermolecular bonds that arise in granulated biomass can be reflected in the kinetic parameters of the thermal decomposition of biomass. Investigation of the influence of the pressing pressure on the kinetic characteristics of the thermal decomposition of biomass allows broadening the understanding of the mechanisms of biopolymers pellet formation. The purpose of this paper is to determine the kinetic parameters of desorption of physically bound moisture and to determine activation processes of non-isothermal decomposition of hemicelluloses of wood biomass, depending on the pressing pressure, using the non-isothermal kinetics Broido model. The work provides an analysis according to the Broido kinetic model of the thermal destruction of biofuel samples from pine wood milled and granulated at a pressure of 80–120 MPa selected over the territory of Ukraine. The results of calculation of kinetic parameters for the stages of desorption of physically-bound moisture and thermal decomposition of hemicelluloses are presented. The value of the activation energy of moisture desorption for pine biomass is in the range of 52.6– 57.5 kJ / mol, where the less value corresponds to milled wood, and the highest value corresponds to the pressing pressure of 120 MPa. The values of the kinetic constants of the thermal decomposition of hemicelluloses are calculated. The value of the activation energy for milled biomass is 104.0 kJ / mol and increases for pellets with an increase of the pressing pressure to 137–170 kJ / mol, which are 37–70%, where a highest value corresponds to a pressing pressure of 120 MPa. It has been established that granulated biofuel has a higher thermal stability during periods of desorption of moisture and decomposition of hemicelluloses, and it increases with increasing a pressing pressure. This fact is explained by the partial cross-linking of the macromolecules of the polysaccharide biomass complex with each other or through a water molecule, which confirms the main provisions of the molecular theory of briquetting.

biofuel, biomass, pine wood, granulation, activation energy, non-isothermal kinetics method, Broido model