encyclopedia

Cleaning and Sorting

How the Cleaning and Sorting Lines work

Cleaning is a process in which unwanted admixtures and impurities are removed from a main material. Grains of other cereals and grains damaged or otherwise degraded are considered to be admixtures. For example, fragments, dried grains, grains infested with pests, etc. Other seeds, ground material and foreign substances such as sand, stones, chaff, etc. are considered impurities. Examples of cleaning are the removal of stem residues, awn, abrasion, straw, etc. on the post-harvest line.

Sorting, grading or calibration, is a process in which the main material is divided into categories according to specified criteria, eg by size, by color, by weight, etc. An example of sorting may be, dimensional sorting of maize sowing seed or calibration of buckwheat before peeling.

Cleaning, as well as sorting, can be done by a variety of principles on a wide range of machines. The combination of these principles achieves the desired cleaning effect. Different physical properties of the particles are used in cleaning and sorting. The basic separation principles include:

1) dimensional sorting
2) aerodynamic sorting
3) magnetic separation
4) sorting by specific weight
5) sorting by color

1) Dimensional Sorting
Sorting by thickness and width is performed on sieves, sorting by length is performed on trieurs. Sieve sorting is the most used in practice. The sieve divides the sorted mixture into a sieve fraction which is larger than the holes in the sieve and a sub-sieve fraction which has fallen through the holes in the sieve. This basic principle is used by the combined cleaning machines of the JCC and JCM series. Both of these model lines of machines are complemented by aerodynamic sorting and the JCM series of machines also by magnetic sorting.

Sorting by length is used to remove long and short (round) admixtures and impurities. Examples of long admixtures are oat kernels in oats or oat kernels in wheat. Examples of round impurities are seeds of weeds of corncockle or bedstraw in wheat. JCT Intended Cylinders are designed for this type of sorting.

2) Aerodynamic Sorting
This is air cleaning. Particles with a lower buoyancy speed than the main crop are sucked out by the air flow. This principle is used in aspiration channels of both the JCC and JCM cleaner series, as well as in other machines equipped with aspiration channels. This principle is also successfully used in JAM aspiration pre-cleaners before sieve cleaning. Expansion chambers, called JVE are used to remove impurities from the air in front of the fan.

3) Magnetic Separation
Ferromagnetic impurities such as metal chips from transport conveyor (redlers), nails, electrode residues and other metal impurities are removed by magnetic separators. Aspiration boxes of the JAB type are equipped with a strong neodymium magnet as standard. Other machines can be supplemented with magnetic plate separators JMS, or more efficient grate magnets JMS.R.

4) Sorting by specific Weight
Specific density is one of the basic parameters used to classify particles of the same size, but with a different weight. The lighter particles float in a fluidized bed of air, while the heavier ones fall on a sieve, which moves in the opposite direction to the flow of grain and is thus separated. This is used, for example, in destoning, or in cleaning the mixture after peeling from the skins on JGD Destoner and JGC Gravity Concentrator. These machines divide the material into two fractions and are easier to set up compared to pneumatic tables.

Another machine using the fluid principle is the JGT Gravity Table. It works on a similar principle as a destoner, but can divide the mixture into several fractions. These machines are used for cleaning small seeds such as poppy seeds, flax seeds, etc., or for cleaning sowing seeds and separating grains infested with pests.

5) Sorting by Color
This is historically the latest way of sorting. Modern optical sorters are able to analyse each individual particle separately and eliminate different particles in color or shape according to the set program. Optical sorters are most often used for final cleaning before consumer packaging, for example in packaging business, peeling lines or food technology. Optical sorters are also able to remove stones, fusaria, sclerotia and possible glass.