Reymann, Steffen (2000) The analysis of complex filtration processes by means of particulate media and slurry flow theory. (PhD thesis), Kingston University, .

Abstract

The better understanding of the physics of colloidal suspensions is of enormous theoretical and industrial importance. Of particular interest is the study of the interaction between the suspended particles and the influence of this interaction on the bulk behaviour of the suspension. New and original analytical and numerical methods for the study of interparticle interactions and dead-end filtration problems have been developed. The developed methods for the interparticle interaction are as follows: a) A new analytical method for the solution of the Debye-Huckel equation in arbitrary geometries based on a novel series approach to fit the appropriate boundary conditions b) The modelling of the electrolyte within such (non-parallel) geometries by means of a canonical Monte Carlo simulation method The calculation of the corresponding electrostatic forces from methods a) and b) and their comparison is carried out; differences for small separations between the charged surfaces can be explained by the field-theoretic nature of the Debye-Huckel theory. The lattice-Boltzmann method provides a powerful numerical tool to simulate the flow of particle-fluid mixtures. The method has been implemented successfully and used to study a number of problems, notably the shear flow of suspensions and filtration problems. Dead-end filtration problems provide an easy accessible model system for the study of the behaviour of particulate suspension in the vicinity of irregular boundaries. The importance of the interparticle interaction is being recognised and two new theoretical models have been developed, appropriate to different types of interactions: a) In the case of strongly charged particles a stiffness model is found to be appropriate, here the exponent of the volume-time curve depends on the strength and range of interaction and the susceptibility of the septum to clogging. b) In the case of neutral particles, the viscous interaction is more important; here the granular temperature model is applied to the problem and particle velocity fluctuations are found to be of great importance. The theoretical and numerical results agree favourably with the outcome from experiments. The backwash of filter systems is a process of enormous industrial relevance. V sing the tools and methods developed in this thesis, extensive experimental data has been studied and analysed.

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