Tom Eaves

Two-phase flow in a screw press

I will present a mathematical model of the dewatering of a saturated two-phase medium in a screw press. The model accounts for the two-phase rheological behaviour of the pressed material and splits the press into two zones, an initial well-mixed constant-pressure region followed by an axial transport region in which the total pressure steadily increases. In this latter region, a slowly-varying helical coordinate transformation is introduced to reduce the dynamics to an annular bi-axial compression of the two-phase medium. The model is compared to experimental observations of the dewatering of a paper-making fibre suspension, and is shown to reproduce operational data.