SU1475707A1 - Impact centrifugal mill - Google Patents

Abstract

The invention relates to the construction of a centrifugal impact mill, in which, simultaneously with the grinding, drying and classification of the material is carried out. The purpose of the invention is to reduce energy consumption and wear of work items, improving the drying conditions of the comminuted material. As the material is fed through the loading nozzle 1 into the bowl of the rotor 7, it falls on its perforated lateral conical surface. At the same time, large particles rise on this surface and are picked up by the upper blades 8 and are hit by the blows 10 and the firing ring 5. Under the action of the lower blades 9, whose area is larger than the area of the upper blades 8, the ground material is blown upwards from the grinding zone falls on the perforated conical surface of the rotor thicket, where they separate. Large particles are subjected to re-treatment in the same upper grinding chamber, and small particles - through the overflow pipe get into the lower grinding chamber of the same design, but with a larger diameter. To use the heat generated during grinding, the grinding chambers are covered with jackets with air intake nozzles 2 and helical guides 13. From the last lower grinding chamber, the material is withdrawn by an open fan wheel 14 through the loading nozzle 13.

Description

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The invention relates to devices for the fine grinding of materials with their simultaneous drying and classification and can be used in the chemical, pharmaceutical, construction, microbiological and other industries.

The purpose of the invention is to reduce energy consumption and wear of work items, improving the drying conditions of the comminuted material.

The drawing shows a centrifugal impact mill.

The centrifugal impact mill contains a loading 1, air intake 2 and discharge 3 nozzles, a prefabricated vertical stepped body 4, each grinding chamber of which is provided with a cylindrical fender ring 5 connected to the conical part. Inside the case on the vertical shaft 6 there is a stepped rotor 7. Each stage of the rotor is equipped with a bowl, made in the form of a reverse truncated cone, facing a large base towards the material loading side. The larger base of the rotor cone is connected to an annular disk, on the end surfaces of which double-sided ventilation-transport blades 8 and 9 and 10 are beaten. The ratio of the areas of the lower blades 9 to the upper 8 is equal to 1.02-1.05. When reducing the ratio of areas lower than 1.02, particles of the material being crushed fall into the space located under the annular disk, and lead to an increase in power costs for grinding. Increasing this ratio to more than 1.05 results in overloading of the screening surface, which also increases the energy consumption for transporting the material.

 Each grinding chamber has an overflow pipe 11 and an air intake in the form of a shirt, equipped with a helical guide 13. On the lower part of the rotor is

open-type fan wheel 14 for unloading finished products.

Moreover, the truncated rotor cone has a perforated lateral surface, the angle of inclination of which generates to the horizontal is determined from the condition:

arccos - (P1 + 4f - 1) of arctg-,

where L is the angle of inclination of the forming bowl in the form of a reverse truncated cone to the horizontal; f is the coefficient of friction of the grinding of the material to be ground on the material of the bowl.

When the angle d is less than the left part of the inequality, the proportion of small particles in the zone of intensive grinding increases, and the grinding efficiency decreases. When the angle X is greater than the right part of the inequality, the movement of the material along the generatrix of the lateral surface of the reverse truncated rotor cone stops

there is no grinding of the material.

Centrifugal impact mill works as follows.

The source material - lignin through the loading nozzle 1 enters the lower base of the rotor bowl 7 and due to centrifugal forces, friction forces and Coriolis forces falls on its perforated conical surface filled to the horizontal at an angle determined by

1 i1

arccos -r (Vl + 4f - 1) with arctg r tg

and equal to 50 ° (friction coefficient of lignin on steel f 0.77) Moving along the conical perforated surface of the bowl, the material is mixed and separated. Large particles rise along the conical surface upwards and, reaching the annular disk, are picked up by the upper ventilation-transport blades 8 and are thrown into the zone of intensive grinding, hit by the action of the blow 10 and the fender ring 5. After destruction of the material particles with a stream against the fender ring 4 air, directed upwards due to the fact that the area of the lower blades is 1.02-1.05 times larger than the area of the upper blades, is removed from the grinding zone and fall on the perforated conical surface of the rotor bowl 7, where create one. Large particles along the surface of the truncated cone again fall into the grinding zone, and small particles are diverted along the overflow pipe 11 into the next grinding chamber, which is more energy-stressed, where the described process of grinding and separation of particles is repeated.

From the final grinding chamber, the material is diverted by an open fan wheel 14 through the discharge pipe 3.

During the grinding process, due to the shock loading and friction of particles against the surface of the walls of the grinding chambers and the rotor, a certain amount of heat is generated. For its use, the grinding chambers are equipped with jackets, inside of which are installed spiral-shaped guides, which promote improved thermal exchange between the walls of the grinding chambers and the air supplied to it.

The amount of air entering the mill at each stage is regulated by the shut-off valves of the air intake nozzles 2. Thus,

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0 5

0

0

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In each grinding chamber by supplying it with a different amount of air, it is possible to maintain a certain thermal regime and thereby regulate the process of drying the material. Due to the fact that the air, cooling the surface of the grinding chambers, is heated before entering each grinding chamber, the moisture contained in it does not condense, and consequently, the process of drying the material is accelerated.

Claims (1)

Invention Formula A centrifugal impact mill, which are installed coaxially one below the other and interconnected by means of overflow pipes of the grinding chamber in the form of an articulation of a cylinder with a reverse cone, forming steps extending downward, passing through the chambers along their axis, the shaft carrying discs located in each chamber blades located on their end surfaces, mounted in the lid of the upper grinding chamber, a loading nozzle located under the lower grinding chamber, a discharge chamber with It is equipped with an additional inlet pipe, through which the lower grinding chamber communicates with the discharge chamber, and the overflow branch pipes are installed along the axis of the grinding chambers, and the air intake is made in the form of a system covering the shredding chambers of the shirts, each of which is made with an air supply regulator and a spiral guide, with each disc is formed with beaters and the central bore and connected to the shaft by means of a bowl mounted on the latter in the form of reverse truncated cone having a perforated side surface and an inclination angle a generatrix defined by the condition of arccos - (Vt + 4f - 1) i oU arctg j, where - the angle of inclination of the forming bowl in the form of a reverse cone to the horizontal 514757076 f is the coefficient of friction of the glide and the area of the lower blades of each dielectric material on the mask is 1.02-1.05 times the weight of the bowl, “the upper blades”