Division of the ground grain fractions in the aerodynamic stream
Nowadays intensive technical reequipment takes place in the industrial mills. At the same time small mills are being built (to 50 tons) in the agriculture. Some of the farmers put limited quantity of small departments and units making flour in the granary and subsidiary rooms. Moreover they need additional equipment to get increasing common output of mill and mill of the first-class.
We will not here go into problems on grain preparation but analyze mill production technology. Here we should note the importance of the division in the grinding process especially in the small plants, because they can divide fractions only according to their geometrical parameters.
In view of the aforesaid we should talk about ground grain isolation before separation.
After grain grinding we’ve got mixture of different parts. The smallest ones are flour, which should be separated and directed to a definite sort. The left parts of the ground grain differ from each other in size and quality. That’s why they have to be divided into fractions and processed in compliance with the technology.
The existing method of ground grain separation according to the size is based on the self sorting and sifting processes. The last ones are carried out on the plain sieves, moving round and sifting in a horizontal level. The product got in this process is characterized by the passageway of a definite sieve.
The effectiveness of the sieve separation depends on the great number of factors: grain-size, its physico-mechanical characteristics, temperature and moisture of the product, unit load on the sieve, material and quality of the sieve, the size of its holes, sifting construction, transport conditions, kinematic parameters, the ways of the sieve cleaning and so on.
In order to get high productivity of the sorting for the most part of the ground grain there is an optimal thickness of layer: 12-18 mm, in action 15-24 mm. If the thickness is higher we get the product of the worse quality.
In a complicated flour making process in a modern mill we can see a wide application of a pneumatic transport. In the grinding part of the mill air lightens pneumatic sorting of the dunsts and groats. Air and product moving round together make a firm aspiration and we’ve got temperature decrease in the intermediate product of the grinding. As a result friability of the product and sifter of the sieves get better and condensate is also excluded.
Everything said about pneumatic transport doesn’t reveal all the advantages of single units. Combination of some technological operation in one unit will increase its effectiveness.
Characteristic feature of the aerodynamic stream is its universality, which is realized in ability to transport the material and to fulfil technological operations as well. As an example: aerodynamic stream in the pneumatic transport divides special fractions in flour making process.
Centrifugal cyclone separator is one of the pneumatic transport units. It detaches products of the ground grain from air, after that they go to sifting.
Centrifugal cyclone separator can solve the problem of the parts disconnection before separation on the sifting sieves. We can unit some technological operations in it, in addition to material detachment from the air, and achieve some goals: 1) to decrease the load on the sifting and thereby to prevent loss of the valuable parts, 2) to choose cutting parameters for the rolling in order to process the parts of a definite size, and as a result we lighten rolling operation.
The effectiveness of the disconnection in a pneumatic separator will be achieved by constant and equal supply of the heterogeneous mixture as well as by simultaneous action of the separated material and air membranous filled.
Advantages of the pneumatic separator are compactness, simplicity, handiness. All of these are achieved by transformation of the cyclone separator, which cuts down expenses in its turn.
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