Filter press

Filter presses are discontinuously operating pressure filter for solid-liquid separation of suspensions.

Frame filter press, chamber filter press and membrane filter press differ in the design of the filter plates, but not in the filtration principle.

Filter press apparatus for a cake formed by filtration, having a filter pack of filter plates in a frame which is arranged between a fixed lid and a movable lid. Between the individual filter plates to filter means are ( tissue or membrane). The fixed cover is connected via connection and tie rods with the bridge. A hydraulic contact pressure device, which is integrated in the bridge, and acts on the movable cover, the filter pack is pressed. The contact pressures are between 250 and 600 bar. These high pressures, the sealing of the filter package is ensured. The tubing for the supply lines of the suspension is integrated in the fixed cover. The passage opening for the suspension within the filter pack located in the center of the filter plates. In the filter chambers, the suspension with 10 by means of a pump - 20 bar pumped to the filter cloths. The liquid passes through the filter medium and leaves the press about drainage channels. The solid parts of the suspension remain on the filter means, and form the filter cake. After completion of the filtration cycle, the press is opened and the cake. As far as the press this is done non-automatic ( self-cleaning filter press ) is depressurized to slowly open the filter press, and remove the cake from the filter cloths manually.

Membrane filter presses have the peculiarity that the filter cake is also pressed mechanically. To this end, each filter chamber has at least one movable membrane. Said membrane, after the inflow of the suspension was turned off, is set by means of compressed air or pressure water towards the filter cake and presses it into motion so additionally.

Filter presses are used in many ways. The size of the solids to be separated ranges from submillimeter range (eg enzymes ) up to the mm range (eg sewage sludge). The filter areas ranging from less than 1 m in small laboratory processes to over 1000 m² with large presses. Uses it would in the food industry, the chemical. ceramic or the pharmaceutical industry. Also, you can find them in metallurgy and mining

An important application of the filter press is the waste water treatment. Main application of the filter presses there is the drainage of sewage sludge. This filter cake may not be disposed of to landfill since 2005 by a tightening of legislation ( TA municipal waste ). They are either the thermal treatment in waste incineration plants supplied or discharged as fertilizer on agricultural land. The use in agriculture represents the most cost -effective method of disposal for the waste water treatment plant operators and is currently widely used. In 2003 ( German Association for Water, Wastewater and Waste ) were used 56 % of the treated sludge from municipal wastewater treatment plants as a fertilizer in agriculture and landscaping in Germany, according to DWA.

See also: separation processes (process engineering )