General

Designed particularly for polishing applications, the filter medium consists of a coating or „precoat“ of material applied to the filter cloth. This medium can be diatomaceous earth, sawdust, etc.

The precoat is applied prior to filtration in thicknesses up to a maximum of 100 mm. A scraper knife is used to discharge a thin layer of cake containing the feed slurry particles, which collect on the surface of the precoat. The knife advances in steps of one hundredth of a millimetre per revolution as the drum rotates (in special designs, continuous advance also possible), thereby presenting a clean surface to the feed material on each cycle. The scraper advance is stopped automatically when the minimum layer thickness is reached. This type of filter is used in applications to clarify suspensions with low solids content or with tendencies to blind conventional filter media. The main advantages are clear filtrate and continuous and trouble-free operation.