Inclusion (particle) removal by interception and gravity in ceramic foam filters

Abstract

An analytical model regarding the ceramic foam filter (CFF) as a network of branches (cylinders) has been developed to describe inclusion removal in CFFs used for aluminium filtration. The model based on measurements of filters with 30 pores per inch, should also predict behaviour of commercial filters with finer pores. Filtration efficiency is a function of particle size, metal velocity, particle settling velocity, and filter properties—the branch diameter, filter thickness, porosity, and specific surface area. The model takes into account interception with cylinders and settling on branch surfaces. The velocities are calculated from the Forchheimer and Ergun’s equation. There is good agreement between the model and plant experiments. Removal by interception increases strongly with decreasing cylinder diameter. There is indication that Al₂O₃ and SiC filters differ in their capture of inclusions.