Numerical Study on the Hydrodynamics of a Self-Heating Biomass Fast Pyrolysis Reactor

Abstract

A novel, self-heating biomass fast pyrolysis reactor named internally interconnected fluidized beds (IIFB) was proposed for the efficient production of bio-oils and chemicals by catalytic fast pyrolysis of biomass. The IIFB reactor mainly consisted ofapyrolysis bed(biomasspyrolysis)andacombustionbed(charburningandcatalystregeneration)connectingthrough adrafttubeandadipleg.Eachbedwasdesignedforthecontinuousoperation.Thehydrodynamiccharacteristicsofthereactor,such as solid circulation rate, pressure distribution, and volume fraction of particles were performed using numerical simulation in this study. A non-steady-state, Eulerian multi-fluid model was used. The gas phase is modeled with a k� e turbulent model, and the particle phase is modeled with the kinetic theory ofgranular flow. The experiments were carried out in an IIFB experimental system to verify the model. The simulation results show that the solid circulation rate was kept as a constant of 110 kg/h after 12 s of computational time compared to the value of 104.5 kg/h obtained in the experiments. The time-averaged values of the pressures at different positions after 12 s of computational time were also close to the experimental data. The particles in the dipleg were monitored to drop downward at a uniform speed of 0.07 m/s. In comparison to that in the draft tube, the velocity magnitude (includingvertical orhorizontaldirections)oftheparticlesdecreasedalongtheheight ofthedrafttube,whereastheverticalvelocity oftheparticles firstunderwentadisturbed flowbecauseofthe solidsolidandsolidwall collisions,thenincreasedrapidly,and last were kept at an almost uniform magnitude. The results can provide a conceptual guide for designing, building, and operating the system of biomass (catalytic) fast pyrolysis.