Color sorter

from Wikipedia, the free encyclopedia
Color sorter in a flour mill

A color sorter (also color separator or photo separator ) is a sorting machine that separates individual elements of granular matter based on color differences. A color sorter uses a simple form of optical image recognition for recognition and a mechanical separation process , usually blowing out, for separation. Color sorters are mainly used to select different colored grain from a good product, but also in recycling to separate incorrectly colored plastic flakes.

Color sorters originally came from sorting beans and coffee . Highly fatty black coffee beans (stink beans) are sorted out from the ripe green coffee beans by color recognition. For a long time, detection was carried out monochromatically, i.e. by detecting differences in brightness in a black-and-white spectrum. Since around 2012, more and more real color sorters with a selected spectrum have been used in the seed and food sector, and the process is also common in recycling.

application areas

Food

In the meantime, the most sorted product in the world is rice , in which dark or spotty grains are sorted out from the good product “white rice”. Color separators are also becoming more and more popular in grain mills , which is the most common place of use in Central Europe. Mainly the poisonous dark ergot is extracted from rye, in addition vetches and other black deposits from wheat or spelled can be sorted out, in the case of edible grain also foreign grain.

In the food sector, the color sorters are used, among other things, to sort out

Further areas of application

Color sorters are used in many other industries. This includes

A color sorter can also be called an "electronic Cinderella ".

technology

In the case of dry products, the product is placed on a chute for separation. At the end of the chute, the grain is then analyzed in free fall by cameras or sensors and only a few milliseconds later and a few centimeters below it is blown out with short blasts of compressed air . In the case of moist products (vegetables, legumes), on the other hand, detection takes place on a moving belt or a moving grate, and here too, bad product is blown out after detection. While color sorters used to be worthwhile for luxury products such as coffee or nuts, from around 2000 onwards, through technical progress such as the use of digital cameras instead of photocells, throughputs increased while system prices fell at the same time. As a result, color sorters have a much wider range of uses today, including agriculture for the cultivation of special crops.

Complex sensors are used for detection, especially when sorting in the recycling sector, including household waste sorting, and when sorting minerals. These work in the near infrared spectrum (NIR), with UV or X-ray - fluorescence and transmission or with lasers . These machines are grouped together with color separators under the collective term sensor-based sorters .

Near-infrared cameras in color readers in the food sector mostly still work with a sum value and not with NIR spectra. A distinction is made between cameras in the low NIR range of approx. 700–1000 nm wavelength, which are used to detect stones or foreign matter, and NIR InGaAs cameras, which are used in the wavelength range of approx. 1100–1500 nm e.g. B. recognize pelted grains or fusarium grains . With detection using NIR spectra, cereal grains can be better read out or sorted by protein content .

Depending on the size and product, color sorters have a throughput of a few hundred kilograms to approx. 40 tons per hour for food, and up to 100 t / h for stones.

Individual evidence

  1. ^ Karl Ulmer: Machine science milling: flour milling - peeling milling - feed production - special milling . Swiss Vocational Training Commission for Müller, Zollikofen 2009.
  2. ↑ Peter Erling (Ed.): Handbook of flour and peeling mill . 4th edition. Erling Verlag, Clenze 2018, ISBN 978-3-86263-127-8 .