Modelling dewatering behaviour through an understanding of solids formation processes. Part II--solids separation considerations.
An understanding of the mechanisms which control solids formation can provide information on the characteristics of the solids which are formed. The nature of the solids formed in turn impacts on dewatering behaviour. The 'upstream' solids formation determines a set of suspension characteristics: solids concentration, particle size distribution, solution ionic strength and electrostatic surface potential. These characteristics together define the suspension's rheological properties. However, the complicated interdependence of these has precluded the prediction of suspension rheology from such a fundamental description of suspension characteristics. Recent shear yield stress models, applied in this study to compressive yield, significantly reduce the empiricism required for the description of compressive rheology. Suspension compressibility and permeability uniquely define the dewatering behaviour, described in terms of settling, filtration and mechanical expression. These modes of dewatering may be described in terms of the same fundamental suspension mechanics model. In this way, it is possible to link dynamically the processes of solids formation and dewatering of the resultant suspension. This, ultimately, opens the door to improved operability of these processes. In part I of this paper we introduced an integrated system model for solids formation and dewatering. This model was demonstrated for the upstream processes using experimental data. In this current paper models of colloidal interactions and dewatering are presented and compared to experimental results from batch filtration tests. A novel approach to predicting suspension compressibility and permeability using a single test configuration is presented and tested.
Dustan
A C
AC
Department of Chemical Engineering, University of Cape Town, Rondebosch 7700, South Africa.
Cohen
B
B
Petrie
J G
JG
D001703:Biophysics / Q000379:methods*; D003102:Colloids / Q000737:chemistry*; D004573:Electrolytes / Q000737:chemistry; D005374:Filtration; D006863:Hydrogen-Ion Concentration; D006878:Hydroxides / Q000737:chemistry; D007477:Ions; D015233:Models, Statistical; D012212:Rheology; D055672:Static Electricity; D013997:Time Factors; D014867:Water / Q000737:chemistry*
D003102:Colloids; D004573:Electrolytes; D006878:Hydroxides; D007477:Ions; D014867:Water