No abstract

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.

AbstractAlthough fibrous suspensions are finding increasing use in many applications, holistic studies investigating their material properties are essentially non-existent due to a lack of simple and reliable measurement techniques. To address this, geotechnical techniques have been considered for the characterisation of an extruded suspension of poplar fibres. Use of such characterization techniques was thought suitable since the extruded fibres share many physical similarities with fibrous peats, and since both materials are primarily derived from plants. In the present study, oedometer and direct shear tests were employed to evaluate the compressibility, permeability and friction properties of poplar fibres. Triplicates of each test were carried out for two differently prepared poplar fibres at several different initial water contents. All measurements were found to be in good agreement with the values typical of fibrous peats, justifying direct cross-over of geotechnical techniques as an alternative method for characterising and modelling fibrous suspensions in manufacturing applications.