High Pressure Dewatering Rolls (HPDR) is a novel filtration technology that involves two counter-rotating semi-permeable rolls inside a feed chamber. The rolls are under vacuum, which induces cake formation on the roll surface followed by cake consolidation once the cake emerges from the feed suspension. The rolls are pulled together hydraulically such that cake compression occurs as the cakes meet and travel through the nip. A model is developed to understand the behaviour of compressible suspensions in the HPDR using one-dimensional compressional rheology theory.

The model assumes constant pressure cake formation and consolidation whilst under vacuum followed by controlled rate compression through the nip. The compression rate is determined by the geometry of the rolls and decreases to zero at the narrowest point, necessitating explicit modelling of irreversible compression. The model inputs are the material compressibility and permeability, feed slurry concentration, roll dimensions, roll rotational rate, vacuum pressure, and gap.

The model is solved numerically to predict the cake solids concentration, throughput, and force on the rolls. An exact similarity solution exists when the feed concentration is less than the gel point and the roll resistance is negligible, which predicts that the solids throughput increases with the square-root of angular velocity and submerged arc length. Overall, these findings contribute to a better understanding of HPDR behaviour and provide insights for optimising performance in practical applications...