Settling velocities of particulate systems: 120. Batch centrifugation of flocculated suspensions

In this contribution we show how the phenomenological theory of sedimentati on-consolidation processes can be extended to the presence of centrifugal f ield. The modelling starts from the basic mass and linear momentum balances for the solid and liquid phase, which are referred to a rotating frame of reference. These equations are specified for flocculated suspensions by con stitutive assumptions that are similar to that of the pure gravity case. Th e neglection of the influence of the gravitational relative to the centrifu gal field and of Coriolis terms leads to one scalar hyperbolic-parabolic pa rtial differential equation for the solids concentration distribution as a function of radius and time. Both cases of a rotating tube and of a rotatin g axisymmetric vessel are included. A numerical algorithm to solve this equ ation is presented and employed to calculate numerical examples of the dyna mic behaviour of a flocculated suspension in a sedimenting centrifuge. The phenomenological model is appropriately embedded into the existing theories of kinematic centrifugation processes of ideal (non-flocculated) suspensio ns. (C) 2001 Elsevier Science B.V. All rights reserved.