Numerical Simulation of Vortex Pyrolysis Reactors for Condensable Tar Production from Biomass

A numerical study is performed in order to evaluate the performance and optimal operating conditions of vofiex pyrolysis reactors used for condensable tar production from biomass. A detailed mathematical model of porous biomass particle pyrolysis is coupled with a compressible Reynolds stress transport model for the twbulent reactor swirling flow. An initial evaluation of particle dirnensionality effects is made through comparisons of single- (lD) and mukbdhnensional particle simulations and reveals that the lD particle model results in conwvative estimates for total pyrolysis conversion times and tar collection. The observed deviations are due predominantly to geometry effects while directional effects from thermal conductivity and permeability variations am relatively small. Rapid ablative particle heating rates are attributed to a mechanical fragmentation of the biomass particles that is modeled using a critical porosity for matrix breakup. Optimal thermal conditions for tar production are obsemxl for reactor wall temperatures of approximately 900K. Effects of biomass identity, particle size distriiutioL and reactor geome~ and scale are discussed