RU2108865C1 - Centrifugal mill - Google Patents

Abstract

FIELD: fine grinding of mineral raw materials; opening units of diamond-containing ores. SUBSTANCE: grinding unit of centrifugal mill includes two cone-shaped rotors 3 mounted coaxially in housing on horizontal shafts 2 at spaced relation to each other; they are revolving in opposite directions. Generatrix of inner working surface of each rotor has form of logarithmic curve whose asymptote is parallel to axis of rotation of rotors and is located at distance equal to radius of outlet hole of loading device. The logarithmic curve is described by the following equation: $$$ where $$$ is present radius of inner working surface of rotor changed at distance $$$ along axis of rotation of rotor from beginning of its curvilinear inner surface; n and c are linear parameters whose magnitudes depend on grain size $$$ of starting material; b=$$$; $$$ and $$$ are preset maximum and minimum radii of working surface of rotor; $$$=65 to 75 dwg is angle between tangent line to working surface of rotor at point lying on maximum radius of this surface and axis of rotation of rotors. End sections of rotors may be provided with radial circular recesses. EFFECT: enhanced efficiency. 2 cl, 3 dwg

Description

 The invention relates to techniques for the disintegration of solid ore and non-metallic materials and can be used for fine grinding of various minerals in the construction and chemical industries, coal for environmentally friendly and cost-effective combustion in boiler units of thermal power plants, as well as for the disclosure of diamond ore aggregates.

 Known grinding installation of a centrifugal type, comprising a housing with coaxially mounted in it with a gap on the horizontal shafts of two cone-shaped disks with partitions forming an annular grinding chamber [1].

 However, this device does not allow to achieve high grinding efficiency due to the low speed of the colliding grains of the material, irrational particle paths moving towards each other flows of the crushed product. The disadvantages are due to the fact that the movement of the material on the conical working surfaces of the rotors, the generators of which are straight, does not provide a set of particles at high speed. The presence of partitions only exacerbates the disadvantages.

 Known centrifugal mill in the form of coaxially placed in the housing on the horizontal shafts of two cone-shaped rotors, rotating in different directions and installed with a gap relative to each other, loading and unloading devices and drive [2].

 The disadvantage of this mill is the low disintegration efficiency, since the particles of the material do not have time to acquire a sufficient departure speed and the corresponding trajectory of the particles due to the irrational design of the rotors. In addition, the rectilinear generatrix of the working surface of the rotor does not allow to form the required dispersal of particles depending on their particle size.

 The objective of the invention is to increase the efficiency of disintegration by increasing the speed, and hence the energy of collision of the particles, as well as optimizing the trajectories of their relative motion.

This is achieved due to the fact that in a centrifugal mill containing a housing, a grinding unit in the form of two cone-shaped rotors coaxially placed in the housing on horizontal shafts with a gap relative to each other and rotating in opposite directions, loading and unloading devices and a drive forming an internal working the surface of each rotor has the form of a logarithmic curve, the asymptote of which is parallel to the axis of rotation of the rotors and placed from it at a distance equal to the radius of the outlet of the boot when ability, while the logarithmic curve is described by the equation
r _i = r _min {0,5 exp [(l _i -c) / b] +1} -n,,
Where
r _i is the current radius of the inner working surface of the rotor, measured at a distance l _i along the axis of rotation of the rotor from the beginning of its curved inner surface; n and c are linear parameters, the value of which depends on the size K _{max of the} starting material:
n = (2/3) K $\genfrac{}{}{0ex}{}{\text{1.25}}{\text{max}}$ ; c = A / (nK $\genfrac{}{}{0ex}{}{\text{0.5}}{\text{max}}$ ); ;
Where
A = 540-580 - an empirical coefficient depending on the physicomechanical properties of the material being ground
b = (r _max -r _min + n) / tgφ _max
Where
r _max and r _nin - given (taken structurally), respectively, the maximum and minimum radii of the working surface of the rotor; φ _max = 65-75 ^o - the angle between the tangent to the working surface of the rotor at a point located on the maximum radius of this surface, and the axis of rotation of the rotors.

 In addition, at the end sections of the rotors made radial annular undercut.

 In FIG. 1 shows a section of a centrifugal mill; in FIG. 2 - profiles of the working surface with different sizes of the source material; in FIG. 3 is a view A in FIG. one.

 The centrifugal mill includes a grinding unit in the form of a pair of rotors 3 rotating in opposite directions coaxially placed in the housing 1 on the horizontal shafts 2. The rotation speed can be adjusted. Between the end surfaces of the rotors there is a gap δ, the value of which can vary depending on the type of material and the required grinding fineness.

 Material loading is carried out through the loading device in the form of cylindrical or conical nozzles 4 arranged along the axis of the rotors 4. Inside the nozzles 4 there are feeding screws 5. The unloading device 6 has the form of an outlet pipe in the lower part of the housing 1. The shafts 2 are driven by a drive, for example, gear wheels 7.

 The inner working surface 8 of each rotor 3 is formed by rotation of a logarithmic curve around an axis coinciding with the theoretical axis of rotation of the rotors. The asymptote of the logarithmic curve is parallel to this axis and placed from it at a distance equal to the radius of the outlet of the loading device 4.

The shape of the logarithmic curve is described by the equation
r _i = r _min {0,5 exp [(l _i -c) / b] +1} -n,,
Where
r _i is the current radius of the inner working surface of the rotor, measured at a distance l _i along the axis of rotation of the rotor from the beginning of its curved inner surface; n and c are linear parameters, the value of which depends on the size K _{max of the} starting material:
n = (2/3) K $\genfrac{}{}{0ex}{}{\text{1.25}}{\text{max}}$ ; c = A / (nK $\genfrac{}{}{0ex}{}{\text{0.5}}{\text{max}}$ ); ;
A = 540-580 is an empirical coefficient depending on the physicomechanical properties of the material being ground;
b = (r _max -r _min + n) / tgφ _max ; ;
r _max and r _min - set (taken structurally), respectively, the maximum and minimum radii of the working surface of the rotor; φ _max - the angle between the tangent to the working surface of the rotor at a point located on the maximum radius of this surface, and the axis of rotation of the rotors.

It was experimentally established that the angle φ _max should be equal to 65-75 ^o . With an increase in the angle φ _max , the abrasion effect somewhat increases and the impact energy of the oncoming flows of the crushed material decreases.

At the same time, the working profile of the rotor should correspond to the size of the initial product, since large particles of a rounded shape not only slide on the working surface, but also roll along it, not having time to gain the desired speed until it breaks off the rotor. Therefore, for a coarse-grained material, the acceleration section at which the angle φ _i between the tangent to the working surface and the axis of rotation of the rotor is much smaller than φ _max should be greater than for fine-grained material, although this increases the axial size and mass of the rotor.

 At the end sections of the inner surfaces of the rotors 3, radial annular recesses 9 can be made, which increases the wear resistance of these sections, since during operation the recesses 9 are clogged with compacted fine material, and further wear does not occur.

 The mill operates as follows. The source material through the feeding screws 5 is sent from two sides along the nozzles 4 into the working cavity of the rotors 3, where it is slowly and then faster accelerated by centrifugal forces to high speeds. The nature of the speed set depends on the shape of the working surfaces 8 of the rotors 3, which, in turn, depends on the size of the starting material. The difference in the shapes of the working surfaces is determined by the different nature of the movement of small and large particles: the movement of large particles is sliding with rolling, and small ones are practically pure sliding. After the disruption of the material particles from the rotors 3, the flow encounters, accompanied by an oblique impact and friction of the particles against each other, which leads to intensive self-grinding of the material.

 Thus, the proposed design of the mill allows you to organize such a movement of the material along the working surfaces of the rotors, which provides the most efficient grinding with minimal energy consumption.

Sources of information:
1. RF patent N 2012403, cl. B 02 C 7/06, 1991.

 2. Copyright certificate of the USSR N 599838, cl. B 02 C, 1976.

Claims (2)

1. A centrifugal mill containing a housing, a grinding unit in the form of two cone-shaped rotors coaxially placed in the housing on horizontal shafts with a gap relative to each other and rotating in opposite directions, loading and unloading devices and a drive, characterized in that it forms the inner working surface of each the rotor has the form of a logarithmic curve, the asymptote of which is parallel to the axis of rotation of the rotors and placed from it at a distance equal to the radius of the outlet of the loading device , The logarithmic curve described by the equation
r _i = r _min {0,5 exp [(l _i -c) / b] +1} -n,
where r _i is the current radius of the inner working surface of the rotor, measured at a distance l _i along the axis of rotation of the rotor from the beginning of its curved inner surface;
n and c are linear parameters, the value of which depends on the size K _{m a x of the} source material
n = (2/3) K $\genfrac{}{}{0ex}{}{\text{1.25}}{\text{max}}$ ;
c = A / (nK $\genfrac{}{}{0ex}{}{\text{0.5}}{\text{max}}$ );
A = 540 - 580 - empirical coefficient depending on the physicomechanical properties of the crushed material;
b = (r _max -r _min + n) / tgφ _max ;
r _{m a x} and r _{m i n} are given (taken structurally), respectively, the maximum and minimum radii of the working surface of the rotor;
φ _max = 65 - 75 ^o - the angle between the tangent to the working surface of the rotor at a point located on the maximum radius of this surface, and the axis of rotation of the rotors.  2. The mill according to claim 1, characterized in that at the end sections of the rotors are made radial ring grooves.

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