Filtering properties of twin-layer sintered filters

Summary

• 1. At equal filter thickness, twin-layer sintered filters from nonspherical powder have a much superior combination of filtration qualities (permeability and purification fineness) compared with filters made entirely from the same powder.

• 2. The dependence of permeability on resistance for twin-layer filters obeys Darcy's law within the limits investigated; for short filtration periods, permeability and purification fineness are the same irrespective of which of the two layers faces the oncoming fluid stream.

• 3. It is shown that the service life (period of operation before clogging) of twin-layer filters is longer when the filters are placed so that their coarse-fraction powder layer faces the fluid stream; filters arranged during operation with their fine-fraction powder layer against the fluid stream were found to exhibit better regeneration characteristics.

• 4. It is shown that filters from nonspherical powders can very effectively be regenerated by ultrasonic treatment, but not by the method of counter-blowing (at pressure drops of up to 1.5 MN/m²).

• 5. For a given filtration fineness, a twin-layer filter has a much longer service life (to clogging) than a filter made from powder of one fraction.