Gravity Nutsche filters

Typical uses Separation of free filtering solids requiring gentle handling. FDS process ratings 4 C, 7, 7, 9. 

Typical particle size and feed concentration range 100-10000 pm and 1-10% w/w. 

Gravity Nutsche filters find limited use when larger particle sizes are present and gentle handling of a feed is required. General operation is similar to both vacuum and pressure Nutsche filters (see Sections 1.4.1.1 and 1.4.2.1) except the feed is introduced and processed within the filter chamber under the influence of gravitational forces alone. The most frequent application of gravity Nutsche filters is beer mash filtration. 

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Nutsche Filters A nutsche is one of the simplest batch filters. It is a tank with a false bottom, perforated or porous, which may either support a filter medium or act as the filter medium. The shiny is fed into the filter vessel, and separation occurs by gravity flow, gas pressure, vacuum, or a combination of these forces. The term nutsche comes from the German term for sucking, and vacuum is the common operating mode. 

Gravity filters are seldom used in the process industries because they offer low filtration rates, however, simple Nutsch filters are sometimes found in the pharmaceutical industry at pilot scale. The Nutsch filter is a tank with a perforated base on which a filter cloth can be supported. The feed slurry liquid filters through the cake and cloth under its own weight. Although these units are low cost, they are labor intensive to operate, cannot be contained for protection of the product or the operator, and are slow. 

Batch vacuum filters were developed from gravity filters and, in essence, Buchner funnels as used in laboratories and Nutsche type filters as used in industry are similar to gravity filters, except that they feature a vacuum pump or some other vacuum generating equipment to reduce the pressure under the filter medium, thereby increasing the driving force across the filter medium. 

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