Experimental and theoretical investigation of wood pellet shrinkage during pyrolysis

Abstract

Gasification of wood pellets is confronted with the problem of adhesion of fuel in the pyrolysis zone. In order to investigate the cause and regularities of fuel adhesion, experimental and theoretical studies of wood pellets thermal deformations were carried out. Experimental studies were performed by measuring thermal deformation of a wood pellet in an electrical reactor from 300 to 1 000 °C temperature in an inert atmosphere. The studies showed that the pellet radius decreased by 10% from 300 to 500 °C temperature, and by 20% from 500 to 1 000 °C temperature. It was also established that the wood pellet expands to 15% from 300 to 830 °C temperature at the beginning of fuel thermal deformation. The paper also presents the theoretical studies of wood pellets thermal deformations. The theoretical calculations were performed by Matlab using a one-dimen­sional pyrolysis model of wood pellets that includes the experimental data and the observed expansion of wood pellets. Simulation results were compared with the experimental ones. Modelling and experimental results showed that the thermal deformation of wood pellets values was different by 2–5%.