Rheological characterization and CFD modeling of corn stover–water mixing system at high solids loading for dilute acid pretreatment

• Rheological properties of the high solids (40–100%) corn stover system were characterized.
• CFD model with the rheological properties and helical ribbon mixing was developed.
• Power consumption and mixing efficiency were calculated by CFD modeling.
• Fluid dynamics experiments for the high solids system at different scales were all in agreement with CFD calculations.

CFD modeling of pretreatment reactors at very high lignocellulose solids content requires the characterization of rheological properties of this specific system. In this study, the non-Newtonian rheological properties of the corn stover–water mixture at high solid loading up to 50% with helical ribbon agitation were characterized. The rheological model was developed by introducing the power law model and measuring the torque values of the mixing system in a small reactor (5 L), and then applied to the larger reactors (50 L and 500 L). The CFD model was developed based on the determined rheological properties. The fluid dynamics experiments in three reactors with different scales were used for validation of the rheological model. The calculated power consumption and mixing efficiency by CFD modeling were in good agreements with the experimental results. This study provided a practical method for the rheology characterization and CFD model at high solids loading. The CFD model could be applied to the design and structure analysis of pretreatment reactors in lignocellulose biorefining processes.

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