Study On Consolidation Of Gravity Sedimentation And Dead-End Filtration

Because of the density difference between solid phase and liquid one,dead-end filtration is accompanied with sedimentation. In gravity sedimentation and dead-end filtration processes, variations of various interfaces for Al2O3 suspension with various initial concentrations and heights are showed in this paper. It is observed that the initial concentration and height affect various suspension interfaces similarly and ultimate concentration of sediment and filter cake oppositely.In this paper, B.B.O. equation and conservation of mass law are used to analyze the settling process of solid particle in gravity sedimentation and dead-end filtration, explain the effect of initial suspension concentration on curves of supernatant-suspension height vs. time in theory and educe the functions about particle settling velocity in zone settling. In addition, the empirical relation of the effective solid stress and permeability k to volume fraction of solid by a batch of gravity sedimentation experiments, which is used to explain liquid penetrating through sediment and filter cake.For making out the importance of unifying gravity sedimentation and dead-end filtration, the effect of solid settling on dead-end filtration process are discussed in this paper. The relative velocity between solid phase and liquid one is inducted into Ruth Filtration Equation, which can describe the change of filtrate volume with time much more accurately. The relation between permeability and rising speed of filter cake shows that solid settling has a great effect on filter cake resistance. In filtration with and without sedimentation processes, filtrate pressure difference has opposite influence on permeability of filter cake. Finally, a mathematical model about suspension concentration distribution in gravity sedimentation and dead-end filtration is founded on the continuity equation and momentum balance of the solid and liquid. With above results, variations of various interfaces and concentration distribution for Al2O3 suspension in gravity sedimentation and dead-end filtration are simulated. And the simulations are close to experimental values.