ISSN:
1089-7666
Quelle:
AIP Digital Archive
Thema:
Physik
Notizen:
Sedimentation and ultrafiltration are important processes for removing solids from suspensions. The Kynch theory describes the transient settling of noncolloidal particles forming an incompressible sediment by providing a solution to the convective conservation equation. This solution predicts the existence of several different regions as settling progresses. Subsequent treatments have accounted for compressibility within the sediment. These modifications focus largely on stretching the Kynch theory to fit the problem at hand rather than on formulating a new model to include the relevant physics. In this paper a model of sedimentation for colloidal systems is presented by including a diffusion term in the governing equation. In the regions above the sediment, this term acts as a small perturbation to the Kynch theory. Within the sediment, owing to the high solid volume fraction, diffusion is comparable to convection. Slow compression to the maximum sediment volume fraction contrasts the incompressibility of the Kynch theory. Application of the method of matched asymptotic expansions to the conservation equation enables the formulation of a complete description of the settling process, and, in particular, the volume fraction evolution in the sediment. This method is also applied to the related ultrafiltration process. Where the properties of the sediment, or filtercake, are important, such as in ceramics manufacturing, a quantitative understanding of its formation is of obvious value.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1063/1.857526
