New Techniques for Understanding Settler/Clarifier Behaviour

摘要

An algorithm has been developed to predict steady state thickener operation from fundamental material properties, properly accounting for compression of the suspension network structure within the sediment bed with a pseudo-2D consolidation model based on the theoretical framework developed by Buscall and White in 1987. Comparison of process performance with model predictions has been performed for a large number of industrial thickening operations. Comparisons suggest that there are extra contributions to the rate and extent of dewatering that the model does not predict. Many of these discrepancies, which manifest as enhanced extents and rates of dewatering, are attributable to shear and channelling. Shear effects that cause floc densification can involve rakes, sloped walls and general buffeting in effectively fluidised sections of the equipment with long solids residence times. Channelling phenomena which involve improved rates of liquid transport through non-homogeneities in the solids concentration distribution can be mechanically created through rakes and rods and can also evolve naturally in the sedimentation of flocculated and coagulated materials. Techniques for probing these shear effects are discussed.