Filtering properties of porous materials from nonspherical powders

Conclusions

• 1. The results are presented of a study of sintered filters from nonspherical powders. It is shown that the optimum combination of permeability and stopping power is attained with high-porosity filters produced from powders with fine particles, the actual choice of a powder fraction being governed by the necessary stopping power.

• 2. It was established that the permeability coefficient of sintered filters pressed from nonspherical powder substantially increases with increasing filter thickness, which is due to the presence of a densified surface layer. The dependence of the permeability coefficient on filter thickness is more pronounced in the case of filters pressed from powders of lower apparent density.

• 3. It is shown that the stopping power of filters is independent of specimen thickness (over the 2–8-mm range investigated). An exception are filters of 55% porosity produced from a 0.28–0.36-mm powder fraction, whose stopping power becomes greater with increasing thickness.

• 4. Studies of the sludge-holding capacity of filters from nonspherical powders demonstrated that, depending on whether filtration is controlled by a volume of surface mechanism, different laws govern the increase in the resistance of filters operating in a contaminated fluid. The rate of rise in the resistance of operating filters increases with decreasing specimen thickness and porosity.

• 5. Assessment of regeneration power on the basis of the extent to which the starting sludge-holding capacity of filters is restored is clearly more appropriate than other techniques. Ultrasonic cleaning restores 90% or more of the starting sludge-holding capacity of filters from nonspherical powders.