Crushing
The crushing is one of four major classes of process mechanical process technology and describes the shift of the particle size distribution ( particles , droplets , bubbles ) in a finer size range. The others are agglomerating , mixing and separating .
Chopping is known to everyone from everyday life, if he has already worked in the kitchen . You cut, grate, mash or grind food and spices in order to prepare them for their palatability, to develop their taste or smell or simply to bring them into a more appealing shape.
Industrial applications include, for example, mineral processing (raw material extraction), waste recycling, food production and the ceramic industry .
Shredding process
The process of crushing can be differentiated based on the state of aggregation :
Solids
The term chopping is mostly aimed at solids . Depending on the grain size and hardness of the grain type, a distinction is made between coarse crushing, fine crushing and grinding with grain sizes of the starting material from 50 mm to 0.5 mm and fine grinding, fine grinding and colloid grinding with grain sizes from 500 micrometers to less than 5 micrometers. The naming of the results of the crushing ranges from chunks over gravel , Split , semolina , flour , powder up to colloidal fineness.
A distinction is made between the following types of shredding (or types of stress):
- Pressure crushing: material is crushed between two tool surfaces
- Impact comminution : Material lying on a tool surface and is crushed by impact with a second movable mold
- Frictional comminution : Material is stressed by two oppositely moving tool surfaces
- Cutting size reduction : material is cut into two parts using two cutting edges . (See also shear cutting )
- Impact shredding : Material is thrown against a wall, hits a moving tool or two particles collide with one another
Shredding machines such as jaw crushers , impact crushers , hammer mills , ball mills , colloid mills , good-bed roller mills , single-shaft shredders and many others are used.
liquids
If liquids are “broken up”, one speaks of liquid division and, in particular, of sprinkling, atomization (e.g. hairspray ) and spraying. When sprinkling the liquid is distributed in jets or large droplets, when atomizing - often through nozzles - in fine to very fine droplets. When spraying, the liquid is broken up by rotating machine parts or impact surfaces. Application examples of liquid division are cooling , absorption , gas cleaning, drying by atomization, fuel atomization in furnaces and targeted reactions between gases and liquids. The atomization of liquids, emulsions or suspensions plays a special role in the coating of surfaces ( painting ).
Gases
If gases are crushed, i.e. gas bubbles in a liquid environment, one speaks of gassing ( whirlpool , bioreactor ).
machinery
See also
literature
- Klaus Schönert : Breaking processes and micro-processes of shredding. In: Handbook of Mechanical Process Engineering. Volume 1, ed. v. Heinrich Schubert , pp. 183-209. WILEY-VCH Verlag, Weinheim 2003.
- Klaus Schönert: Chopping. In: Handbook of Mechanical Process Engineering. Volume 1, ed. v. Heinrich Schubert, pp. 299–382. WILEY-VCH Verlag, Weinheim 2003.
- M. Stieß: Mechanical Process Engineering 2 . Springer, Berlin 2001, ISBN 978-3-540-55852-1 .
Individual evidence
- ^ Walter Müller: Basic mechanical operations and their laws , Oldenbourg Verlag , 2008, ISBN 9783486598681 , p. 177 [1]