Sedimentation behaviour of complex polydisperse suspensions

Experimental data were acquired using a novel sedimentation analyser equipped with pressure and capacitance transducers, with the objective of developing a process-orientated model to enable prediction of the sedimentation behavoiur of concentrated polydisperse particulate mixtures within the size range 1 – 150 μm. Parallel experiments were performed in a batch vessel in which zones of the sedimentation column could be sectioned and removed for analysis. The sensitivity of the solid concentration profiles, solid flux and sediment characteristics to changes in the suspension properties (volume fraction, size distribution and particle zeta potential) is demonstrated and quantified using an empirical model. The experimental results are compared with a simulation of the sedimentation process using established hydrodynamics-based correlations. Hence, the regimes under which the use of hydrodynamic considerations alone fail in describing the actual sedimentation behaviour are identified. The physical mechanisms, significance and inter-relationships between the effects of size polydispersity, particle charge and solids concentration are discussed.