Assessing the effect of size and shape factors on the devolatilization of biomass particles by coupling a rapid-solving thermal-thick model

Abstract

In CFD modeling, while the isothermal assumption has conventionally been coupled for updating particle temperature, its applicability diminishes when dealing with thermally thick particles. A thermal-thick discrete phase model (DPM) is developed to simulate pyrolysis of biomass particle group at high heating rates and temperatures, with particles tracked in a Lagrangian scheme. The effects of particle size and shape on the volatile release and heating history are investigated. For spherical particles with a diameter of 9.6 mm, the temperature difference between the surface and center (∆T) does not disappear even up to 50 s. In the particle size range spanning from 200 μm to 9.6 mm, the duration required for a complete volatile release extends from 1.5 to 40 s. For cylindrical particles, in contrast to the particles with an aspect ratio (AR, ratio of particle length to diameter) of 1, the devolatilization time of particles with an AR of 15 can be shortened by more than 50 %. In addition, both the particle shape and size can significantly influence the volatile distribution within the reactor. This work contributes to understanding both the particle size and shape impact on heat and mass transfer during biomass pyrolysis at high heating rates.