Global Model for High-Consistency Wood Pulp Suspensions in Corotating Twin Screw Extruders

A novel composite model was proposed for corotating, fully intermeshing twin screw extruders dedicated to the processing of high-consistency wood pulp suspensions. This model builds on plasticating extruder modeling techniques that have been applied to suspension processing applications and accounts for the unique rheology of a fibrous suspension and changes in consistency (i.e., composition) through liquid absorption and expression. The model was implemented into a simulator, and the potential of this simulator to predict the axial profiles of major processing variables (i.e., pressure, residence time, filling ratio, liquid and swollen fiber mass flow rate, and consistency) was successfully demonstrated through simulation and experimental comparisons. Although this model was developed for extrusion processing of wood pulp suspensions, it may be easily adapted to other suspension processing applications if the rheological properties of the suspension can be appropriately modeled.