(44e) Simulation of Granular Mixing in an Auger Reactor Based on the Discrete Element Method

Auger reactors are a promising alternative for conversion of biomass to transportation fuels via fast pyrolysis. They can achieve high mixing effectiveness and heat transfer rates. Previous studies have demonstrated that mixing effectiveness of biomass with pyrolysis heat carrier is important for increasing fast pyrolysis bio-oil yields. However, there is limited understanding of reaction and mixing characteristics of fast pyrolysis auger reactors. The purpose of this research is to develop a discrete element method (DEM) for simulating granular flows confined by complex geometry structures and identify parameters that influence the mixing of biomass and heat carrier particles in a dual-screw auger reactor. Reactor design parameters that are investigated include screw rotation speed, rotation orientation, and diameter ratios of the heat carrier and biomass particles. Different biomass shapes are also considered in the model. Initial results demonstrate that DEM can capture the mixing behavior of the dual-screw auger reactor. Modeling results also indicate that adopting similar particle diameters of biomass and heat carrier can prevent mixture segregation. These results can be compared to experimental studies, which indicate that the optimal rotation speed is around 58 RPM and counter-rotating screws enhance mixing effectiveness. Further development of this numerical method will allow for the design of novel reactor configurations for the efficient conversion of biomass to transportation fuels.