(657d) Low-Order Modeling of Biomass Particle Mixing and Reaction in a Bubbling-Bed Fast Pyrolysis Reactor

Bubbling fluidized bed reactors are widely used for fast pyrolysis of biomass. Whether one is concerned primarily with interpreting laboratory pyrolysis reactor data or evaluating the potential performance of pilot or commercial scale reactors for liquid fuels production, it is important to be able to accurately relate the spatial mixing characteristics of the biomass particulates in the reactor to the resulting carbon yields and composition of the raw pyrolysis products. This task is greatly complicated by the non-uniform properties of typical biomass feed, the turbulent multi-phase mixing processes in the reactor, and the coupling of the particulate mixing with the intra-particle transport processes and reaction kinetics.

In this presentation we report preliminary results from desktop computational simulations of a small-scale bubbling bed fast pyrolysis reactor that combine a highly efficient correlated random walk model for biomass particle mixing with a low-order particle model for intra-particle heat and mass transfer and pyrolysis reaction kinetics. Used together, these models make it possible to rapidly estimate trends in particle mixing profiles and variations in reactor carbon yield and product composition as functions of feed properties and reactor operation. If this basic modeling approach can be confirmed at relevant benchmark conditions with more detailed computational fluid dynamics simulations and experimental measurements, we expect that it will provide a very fast and economical approach for evaluating general trends in pyrolysis reactor performance with variations in operating conditions and feedstock properties.