HYDRODYNAMICS OF THE CONTINUOUSLY FILTERING SLURRY REACTOR - INFLUENCE OF LOAD OF SOLIDS AND PARTICLE-SIZE DISTRIBUTION

Internal filtration in slurry bubble columns offers a possible solutio n to the filtration problems related to this reactor type. The applica bility of the concept has already been demonstrated at full-scale for waste water treatment. Theoretical description of internal filtration is lacking, however. In previous work it was derived on basis of two d ifferent models, that in three-phase filtration solids concentration i n the vicinity of the filter should uniquely depend on a single dimens ionless number, i.e. epsilon(s,b) = f(j root nu l/d(p) root U(g)g). T he validity of the so-called cake build-up number was demonstrated by determining filter cake resistance as an indirect measure of solids co ncentration for a system in batch operation with respect to solids. In the present work the force balance model is extended to include the e ffect of particle size distribution. It is demonstrated that particle polydispersity can explain trends observed upon variation of load of s olids, which cannot be understood assuming the particles to be monodis persed. Based on a simplified version of the model including particle polydispersity, a novel diameter characteristic to filtration behaviou r of polydisperse solids is derived. Using this novel diameter in the cake build-up number, experimental results for four different size dis tributions can be reasonably well described by a single master curve. (C) 1997 Elsevier Science Ltd.