Classifying (process engineering)

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Classification is a separation process in process engineering . The separated components are called fraction .

In mechanical process engineering , classification refers to the separation of a disperse solid mixture into fractions, preferably according to the criteria of particle size or particle density . If the geometric particle size is the separation criterion, classification is carried out by means of sieving ; if density or other equivalent diameters are relevant, views are usedas a classification process. The result is at least two parliamentary groups that differ in that the minimum limit of one group is also the maximum limit of the other group. Solid particles that lie exactly in between are called boundary grains. However, this is an idealized consideration of the separation process, in practice there are more or less large transition areas between the classes.

The aim of the classification is:

  • the production of at least two partial quantities of the original mixture of solids, each partial quantity meeting the specified size criteria as completely as possible. In industrial practice, however, such an ideal selectivity cannot be achieved. Deviating particles are called false grains.
  • the separation of the upper and lower grain in order to avoid disturbances or overloads in subsequent processes.

A distinction is made between the following classification methods:

  • Sieve classification by means of sieves
  • Current classifying with the separation medium air or other gases, e.g. B. by means of air sifting
  • Stream classification with the separation medium water or other liquids, e.g. B. by means of swimming / sinking method .

Crushing, classifying and sorting technology are collectively referred to as processing technology in mining , quarries , gravel works and in the recycling industry .

Individual evidence

  1. ^ Matthias Stieß: Mechanische Verfahrenstechnik 1 Second Edition, p. 276ff