13-20: Fluid dynamics study of cellulosic biomass flowthrough pretreatment

Compressed-hot water flowthrough pretreatment has been shown to be effective to increase the digestibility of lignocellulose while minimizing sugar degradation and reducing the use of chemicals compared with other pretreatment methods.   However, flowthrough pretreatment at scale is challenging to implement because it involves solids and liquid moving at controlled flow rates in opposite directions at elevated pressure (250 PSI) and solids concentration (~25% solids). A device was built for measuring pressure drop and other key physical properties obtained for a variety of biomass feedstocks at reaction conditions. The pressure drop across the biomass reactor was measured for switchgrass, sugarcane bagasse and poplar at 170^oC and 350 PSI. Viscous compaction caused bagasse to compress to form a dense plug containing about 450 g/L, switchgrass also compressed to a lesser extent to about 300 g/L and poplar did not compress significantly. Pressure drop across a bagasse reactor was the largest amongst feedstock studied, followed by switchgrass and poplar. As pressure drop is likely to be a key limitation in implementing flowthrough pretreatment in a practical context, understanding the fluid dynamics fundamental and mechanical properties of various feedstocks is an important step to define the feasible region of flowthrough pretreatment.