RU2679718C1 - Conical mill - Google Patents

Abstract

FIELD: crushing or grinding of various materials.SUBSTANCE: invention relates to devices for grinding fibrous materials and solid polymer granules. Conical mill contains coaxially mounted in housing (1) divided by height into sections by transverse partitions rotor (2) and stator (3). Rotor (2) and stator (3) are made in the form of truncated cones, the working surfaces of which have knives and grooves between them, in adjacent sections (4) displaced relative to each other, overlaid with knives and changing in sections (4) in the direction of mass movement — from greater to smaller, from smaller to larger, and from rectangular to evenly trapezoidal, with an angle between the edges of blades of stator (3) and rotor (2) in the sweep plane 5–85°. Annular partitions (5) between blade sections (4) of rotor (2) and stator (3) contain grooves and teeth. Teeth are made equal to the height of the blades of rotor (2) or stator (3) with the possibility of overlapping all the grooves on the previous or next blade section (4). Number of teeth is equal to the number of knives of the previous or subsequent section (4) of rotor (2) or stator (3). Depth of the grooves is 5–100 % of the depth of the grooves, and the width of the grooves is 5–95 % of the width of the grooves on rotor (2) or stator (3) of previous or next blade section (4).EFFECT: high reliability, safety and longer service life of the blade headset, improved quality of grinding of fibrous and solid materials.5 cl, 7 dwg

Description

The invention relates to a device for grinding fibrous materials and solid granules and can be used for grinding polymer materials, including natural origin, and products based on them, for example, in the pulp and paper industry, as well as in the manufacture of smokeless powders of various kinds and their disposal.

The following technical solutions for grinding fibrous materials and hard granules are known. For example, in the pulp and paper and powder industries, pulp fibers are milled in disc mills of the MD type or conical mills.

In the powder industry, the manufacturability of the powder masses and, accordingly, the quality of the resulting powder depends on the quality of grinding of nitro derivatives of cellulose. Cellulose nitro derivatives are crushed in hollanders (rolls), disk mills of the DMK type, or in VVK vibro-cavitation mills [1]. Obsolete pyroxylin gunpowder and solid waste during their production are crushed on rollers, DMK coarse and fine grinding mills [2], conical mills.

The main disadvantages of Dutch holders and MD disk mills are: low productivity (100-150 kg / h), high bulkiness and high energy intensity (500-1000 kW / h). There is a significant heterogeneity of the crushed product, requiring its further sorting (classification). VVK mills are inconvenient to operate due to the imperfection of the mechanism for regulating the working gap between the stator and rotor. When grinding powders, a low degree of reliability of the DMK mills should be noted, because due to the high density of the powder grains (1.65-1.67 g / cm ³ ), disk knives often fail, the manufacture and installation of which is a complex and time-consuming operation.

A conical mill for grinding fibrous materials is known from the prior art (copyright certificate SU No. 1418372 dated 06/03/1986, D21D 1/22, publ. 3.08.1988, Bull. No. 31), consisting of a housing coaxially mounted in it a stator and rotor with grinding surfaces made in the form of knives and grooves between them. The stator and rotor consist of a set of plates with semicircular recesses on the working surfaces having a constant live section on all plates. Adjacent stator and rotor plates are displaced relative to each other with the formation of serrated profile grooves, moreover, the stator rings are displaced in the direction of rotation of the rotor, and the displacement of the rotor rings is in the direction of its rotation. For loading and unloading of processed material, the mill is equipped with inlet and outlet nozzles.

The main disadvantages in the operation of such a mill is the lack of uniformity of particles after grinding and the great complexity when replacing knives, since the rotor and stator have a knife headset in the form of a set of separate plates.

A conical mill is also known for grinding fibrous materials and solid granules (copyright certificate SU No. 1289935 dated 05/20/1985, D21D 1/22, publ. 02.15.1987, Bull. No. 6), containing a stator and rotor coaxially mounted in the housing, made in in the form of truncated cones. The stator is divided in height into sections by transverse partitions perpendicular to its axis, the ratio of the width of which to the section height is from 1/3 to 1/15. The working surfaces of the stator and rotor are equipped with knives and grooves of rectangular cross section. The grooves are located along the surface of the stator and rotor along the entire length and have the same length for the stator and rotor, respectively. The angle between the edges of the stator and rotor knives in the scan plane is from 5 to 85 ° in the direction of the mass exit. The mill is equipped with an inlet and outlet pipe.

The operation of such a mill during grinding operations of nitro derivatives of cellulose and solid waste from the production of pyroxylin powders revealed the following disadvantages:

- driving grooves in the area of mass entry into the grinding zone and loss of mill productivity up to 50-60%;

- slip of unmilled mass along the grooves of the rotor;

- hardening of the mass on the knives from the partitions, worsening the quality of grinding the mass and increasing the danger of further operation of the mill;

- limitation of the initial granule sizes to 1-2 mm when grinding pyroxylin powders.

Also known is a conical mill (RF patent No. 2109869 from 08.22.1995, D21D 1/22 (1995/01), publ. 04/27/1998), containing a stator and a rotor coaxially mounted in the casing, divided in height into sections by transverse partitions, made in the form truncated cones, the working surfaces of which have knives and grooves between them, displaced relative to each other in adjacent sections, overlapped by knives and changing the width of the sections from the larger to the smaller, the number from the smaller to the larger, and the shape from rectangular to isosceles-trapezoid noy, with the angle between the edges of rotor and stator knives in the sweep plane 10-60 °. In this case, the baffles of the rotor and stator are made with the possibility of providing additional flow turbulization. This invention is taken as a prototype.

The main disadvantages of the present invention are the low reliability of the design and the fragility of the grinding mill head, which contains cross sections separating the rotor and stator into sections, which provide additional flow turbulence, since they create cavitation areas that negatively affect the grinding head of the rotor and stator, reducing their service life. In addition, in the case of rotation of the rotor in the direction of movement of the suspension flow, a large amount of milled material accumulates in the grooves immediately in front of the transverse baffle, which is subjected to a greater degree of crushing and grinding, rather than grinding, which negatively affects the obtaining of a uniform high-quality product with desired characteristics. At the same time, in the contact area of the knife headset and transverse partitions due to their constant friction, local overheating occurs, which often causes the formation of mass hardening on the knives, worsening the quality of grinding and reducing the safety of further operation of the mill, especially when grinding nitro derivatives of cellulose in the powder industry.

Therefore, when developing the design of the walls of the conical mill, they must withstand the pressure that the material that accumulates in front of them will exert before its further “breakthrough movement” and the transition into the grooves of the new section of the rotor or stator, i.e. the design of the transverse partitions of the mill should be reliable, not reducing the service life of the knife set of the rotor and stator as a whole, while contributing to improving the grinding quality of the crushed material, preferably in a wide range of its initial characteristics.

The problem to which this invention is directed is to eliminate the above disadvantages and create a universal conical mill with high reliability, safety and a longer service life of the knife headset, qualitatively grinding both fibrous and solid granular materials in a fairly wide range of their initial sizes and properties.

The technical results of the invention are:

- providing high quality crushed product;

- elimination of the breakthrough of unmilled particles of fibrous or granular material from one section to another due to the guaranteed overlapping of the grooves of the rotor or stator with annular partitions between the knife sections;

- ensuring guaranteed mill performance due to the lack of clogging of grooves in the area of entry of fibrous or granular materials into the grinding zone;

- lack of hardening of the mass on the knives due to the exclusion of their constant continuous friction on the transverse partitions;

- improving the design of the conical mill, providing its high mechanical strength and eliminating damage to the knife headset during operation;

- reducing the duration and energy consumption of the processing of coarse-grained (for example, gunpowder) and polydisperse materials that do not require preliminary preparatory technological phases;

- regulation of the degree of grinding with obtaining a more homogeneous product of the required fractional composition;

- ensuring long-term trouble-free operation of the mill in a wide range of crushed materials.

The object of the invention and its technical results are achieved in that the conical mill comprises a rotor and a stator, arranged in the form of truncated cones, the working surfaces of which have knives and grooves between them, in adjacent sections offset relative to each other, overlapped by knives and changing in sections in the direction of the mass movement, the width is from larger to smaller, the quantity is from smaller to larger, and the shape is from rectangular to unequal nano-trapezoidal, with an angle between the edges of the stator and rotor knives in the scan plane of 5-85 °, and the annular partitions between the knife sections of the rotor and stator contain grooves and teeth. The teeth are made equal in height to the knives of the rotor or stator with the possibility of overlapping all the grooves on the previous or subsequent knife section, the number of teeth is equal to the number of knives of the previous or subsequent section of the rotor or stator, the depth of the grooves is 5-100% of the depth of the grooves, and the width of the grooves is 5 -95% of the width of the grooves on the rotor or stator of the previous or subsequent knife section.

The annular partition between the knife sections of the rotor or stator is made in the form of a truncated cone, and its generatrix passing along the upper surface of the teeth coincides with the generatrix of the rotor or stator passing along the upper surface of the knives. The thickness of the annular partition between the knife sections of the rotor or stator is not more than the thickness of the subsequent knife section on the rotor or stator.

The intake section of the cone mill rotor is made in the form of a truncated cone, moreover, its taper varies by 0-65 ° compared with the conicity of subsequent sections.

To control the degree of grinding, the conical mill contains a frequency converter.

The main distinguishing features of the presented invention from any other are:

1. the versatility of the device that allows you to work on any type of raw material - both fibrous and solid granular to obtain a high-quality product with predetermined properties;

2. constructive execution of the transverse septum between the knife sections in the form of a cylindrical ring or annular truncated cone with teeth and grooves of certain geometric parameters with their optimal ratio, providing:

- its high mechanical strength, eliminating the failure, damage or jamming of the knife headset during long-term operation of the conical mill and guaranteeing safe operation;

- effective overlapping of the grooves on the rotor and stator of the knife set, preventing the breakthrough of unmilled material along the grooves from one section to another;

- guaranteed absence of continuous friction of the rotor and stator knives, which can cause severe heating and the formation of hardening knives of crushed material on the knives;

3. complex design of the intake section of the rotor and the annular partitions between the knife sections of the rotor and the stator, providing:

- high reliability and guaranteed performance of the conical mill due to the absence of clogging of grooves with crushed material;

- the use of fibrous and solid granular materials entering the conical mill for grinding, in a fairly wide range of their initial sizes and properties, including for grinding coarse materials, the linear dimensions of which exceed 10 mm;

- simplification of the grinding process of coarse-grained and polydisperse materials, which does not require the introduction of additional stages of sorting, crushing, preliminary grinding into the technological process;

- reducing the time of the technological process of processing coarse and polydisperse materials and reducing energy costs for its implementation;

4. the possibility of changing the degree of grinding depending on the purpose of the product;

5. uninterrupted operation in any type of feedstock (both fibrous and solid granular) with a long service life of the knife headset.

The above distinguishing features of this invention together provide a positive technical result.

A device for grinding fibrous materials and solid granules, according to the invention, is described in detail below using the following schemes and drawings, which show:

- FIG. 1 - conical mill, longitudinal section;

- FIG. 2 - rotor;

- FIG. 3 - stator;

- FIG. 4 - plane of the sweep of the rotor and stator knives;

- FIG. 5 - annular partition: a - rotor; b - stator;

- FIG. 6 - profile of the annular partition: a - on the rotor; b - on the stator;

- FIG. 7 - change in the taper of the intake part of the rotor.

The conical mill (Fig. 1) contains a rotor 2 and a stator 3 coaxially mounted in the housing 1, made in the form of truncated cones, the working surfaces of which have knives 7 (Fig. 2), 9 (Fig. 3) and grooves between them 6 (Fig. . 2), 8 (Fig. 3). The rotor 2 and the stator 3 are divided in height into sections 4 by annular partitions 5 (Fig. 1, Fig. 6). The grooves 6, 8 of the rotor 2 and the stator 3 in adjacent sections 4 are offset from each other, overlapped by knives 7, 9 and have a width varying from greater to lesser in quantity 4, smaller to larger in number, and shape - from rectangular to isosceles-trapezoidal. The angle a between the edges of the knives 7 and 9 of the rotor 2 and the stator 3 in the scan plane is 5-85 ° (Fig. 4). The cone mill is equipped with inlet 10 and outlet 11 nozzles (Fig. 1).

The annular partitions 5 between the knife sections 4 of the rotor 2 (Fig. 5, a) and the stator 3 (Fig. 5, b) contain grooves 12 and teeth 13, and the teeth 13 are made equal to the height of the knives 7 of the rotor 2 (Fig. 2) or knives 9 of the stator 3 (Fig. 3) with the possibility of overlapping all the grooves 6 (Fig. 2), 8 (Fig. 3) on the previous or subsequent knife section 4. The number of teeth 13 is equal to the number of knives of the rotor 7 (Fig. 2) or knives stator 9 (Fig. 3) of the previous or subsequent section 4 of the rotor 2 or stator 3. The depth of the grooves 12 is 5-100% of the depth of the grooves 6, 8, and the width of the grooves 12 is 5-95% of the width of the ABOK 6.8 on the rotor 2 and the stator 3 of the previous or subsequent blade section 4 (FIG. 5).

The annular partition 5 between the knife sections 4 of the rotor 2 or stator 3 can also be made in the form of a truncated cone, then its generatrix passing along the upper surface of the teeth 13 coincides with the generatrix of the rotor 2 (Fig. 6, a) or stator 3 (Fig. 6, b) passing along the upper surface of the knives 7, 9.

The thickness of the annular partition 5 between the knife sections 4 of the rotor 2 or stator 3 is not more than the thickness of the subsequent knife section on the rotor 2 or stator 3.

The intake section 14 of the rotor 2 is made in the form of a truncated cone (Fig. 7) with a taper changing by 0-65 ° compared with the taper of the subsequent sections 4.

To control the degree of grinding, the conical mill contains a frequency converter.

Conical mill operates as follows. Fibrous or solid granular material in the form of an aqueous suspension with a concentration of 3-9% enters through the inlet pipe 10 into the loading cavity of the conical mill, is captured by the intake part 14 of the rotor 2 and passes a zigzag path, moving along the contact surface of the knives 7 and 9 of the rotor 2 and the stator 3 and falling under their influence. The movement of the ground mass occurs along the grooves 6, 8 of the rotor 2 and the stator 3. Under the action of centrifugal forces arising from the rotation of the rotor, the mass moves and passes from the grooves 6 of the rotor 2 into the grooves 8 of the stator 3, while the mass is repeatedly blocked by knives 7 and 9, which is accompanied by its grinding due to the cutting effect of knives and razvolnenie (dissolution) of fibrous materials due to the occurrence of cavitation effects due to the generation of compression and vacuum pulses in the suspension. Discharge pulses arising due to the presence between the knife sections 4 of the annular partitions 5, facilitate the reverse transfer of mass from the grooves 8 of the stator 3 to the grooves 6 of the rotor 2 of the next section and so on. The crushed material through the outlet pipe 11 is removed from the apparatus.

Thus, the grinding (grinding and grinding) of the material in a conical mill occurs as a result of mechanical action of the rotor and stator knives on the particles due to the scissor effect in combination with the action of compression and vacuum pulses on them.

Ring partitions 5 (Fig. 5) are performed with certain geometric parameters:

- the number d of teeth 13 on the annular partition 5 is equal to the number n of knives 7 (respectively, the number of n grooves 6) on the rotor 2 (Fig. 2) or the number m of knives 9 (respectively, the number of m grooves 8) on the stator 3 (Fig. 3 ) of the previous or NEXT section 4:

d = n or d = m;

- the depth Np of the grooves 12 on the annular partition 5 (Fig. 5) is 5-100% of the depth Hc of the grooves 6, 8 on the rotor 2 (Fig. 2) or on the stator 3 (Fig. 3) of the previous or subsequent knife section 4:

Hп = (0,05 ÷ 1,0) ⋅Hк;

- the width Bp of the grooves 12 on the annular partition 5 (Fig. 5) is 5-95% of the width Bk of the grooves 6, 8 on the rotor 2 (Fig. 2) or on the stator 3 (Fig. 3) of the previous or subsequent knife section 4:

Vn = (0.05 ÷ 0.95) ⋅Vk.

In this case, the teeth 13 of the annular partitions 5 are made equal in height to the knives of the rotor 2 or stator 3 to overlap all the grooves 6, 8 on the previous or subsequent knife section (Fig. 6).

Compliance with the annular partitions of the presented range of geometric parameters provides effective and guaranteed overlapping of the grooves on the rotor and stator of the knife set, which prevents the breakthrough of unmilled mass from one section to another, increases the uniformity of the milled material and the quality of the finished product.

The thickness of the annular partition between the knife sections of the rotor or stator is limited in its maximum value, amounting to no more than the thickness L _{c of the} subsequent knife section on the rotor (Fig. 2) or stator (Fig. 3). Otherwise, the annular partition becomes an independent knife section. The minimum thickness of the annular partition is determined by its strength characteristics, i.e. withstand the pressure that the material accumulating in front of it will exert before its further “breakthrough movement” and the transition into the grooves of the new section of the rotor or stator.

In the case of the execution of the annular partition 5 between the knife sections 4 in the form of a truncated cone, the generatrix passing along the upper surface of the teeth 13 coincides with the generatrix of the rotor 2 (Fig. 6, a) or stator 3 (Fig. 6, b) passing along the upper the surface of the knives 7, 9.

The implementation of the annular partitions between the sections of the rotor and the stator with the optimal ratio of geometric parameters increases the life of the conical mill and ensures the safety of its operation by eliminating damage or jamming of the knife headset as a result of the absence of continuous friction of the rotor and stator knives against the partitions, causing severe heating and formation on the knives hardening of the crushed material.

The implementation of the intake section 14 of the rotor 2 of the conical mill in the form of a truncated cone with a taper that varies by 0-65 ° compared with the taper of the subsequent sections (Fig. 7):

(γ-β) = (0 ÷ 65) °,

allows you to process fibrous and solid granular materials supplied to the grinding mill, in a fairly wide range of their original sizes and properties. At the same time, a guaranteed capture by the intake section and preliminary grinding of coarse-grained and polydisperse materials is observed, which prevents clogging of the intake section and allows to simplify and reduce the technological process, reduce energy consumption when grinding coarse-grained materials with sizes exceeding 10 mm, abandoning additional stages of their crushing or preliminary grinding .

The degree of grinding of the material crushed in a conical mill can be controlled using a frequency converter. The grinding ability of the mill will depend on the number of overlapping grooves with knives per unit time, i.e. from the frequency of scissor impacts on the particle of the crushed material - the number of metro cuts per second when the rotor rotates.

The mathematically grinding ability of the mill, expressed in terms of the number of metro cutters per second (Ls), can be described as a first approximation by the Yagenberg formula:

Ls = m _w ⋅m _g ⋅L⋅n / 60,

where m _w and m _g respectively, the number of knives on the rotor and stator;

L is the length of the knife;

n is the rotor speed.

Then, ceteris paribus, the higher the rotor speed of the mill, the more metro cuts per second, respectively, the higher the degree of grinding of the material.

Thus, the proposed conical mill compared with any others have the following advantages:

- high reliability and technological safety, including when grinding fibrous nitro derivatives of cellulose, due to the implementation of the annular partitions between the knife sections of the rotor and stator with certain geometric parameters, ensuring the guaranteed absence of continuous friction against the rotor and stator knives on these sections;

- longer service life of the knife headset due to the design features of the transverse partitions between the rotor and stator sections, as well as the implementation of the intake part of the rotor with a taper different from the general taper of the rotor;

- obtaining a quality product with desired characteristics regardless of the range of initial sizes and properties of the material being ground due to:

• lack of hardening on the mill knives resulting from their local overheating due to continuous friction against transverse partitions;

• changes in the taper of the intake part of the rotor;

• regulation of the degree of grinding using a frequency converter;

- reduction of technological costs, process time and energy saving in the processing of coarse-grained and polydisperse materials by changing the taper of the intake part of the rotor.

Based on the present invention, it is possible to create a universal conical mill for grinding materials with a wide range of initial characteristics both in the national economy and in special technology.

Claims (5)

1. A conical mill, comprising a rotor and a stator, arranged coaxially mounted in the housing and divided in height into sections by transverse partitions in height into sections, made in the form of truncated cones, the working surfaces of which have knives and grooves between them, displaced relative to each other in adjacent sections, overlapped by knives and changing into sections in the direction of movement of the mass, the width is from the larger to the smaller, the number is from the smaller to the larger, and the shape is from rectangular to isosceles-trapezoidal, with the angle between the edges of the stator and rotor knives in the plane reamers of 5-85 °, characterized in that the annular partitions between the knife sections of the rotor and stator contain grooves and teeth, the teeth being made equal in height to the knives of the rotor or stator with the possibility of overlapping all grooves on the previous or subsequent knife section, the number of teeth is equal to the number of knives of the previous or subsequent section of the rotor or stator, the depth of the grooves is 5-100% of the depth of the grooves, and the width of the grooves is 5-95% of the width of the grooves on the rotor or stator of the previous or subsequent knife section. 2. A conical mill according to claim 1, characterized in that the annular partition between the knife sections of the rotor or stator is made in the form of a truncated cone, and its generatrix passing along the upper surface of the teeth coincides with the generatrix of the rotor or stator passing along the upper surface of the knives. 3. A conical mill according to claim 1 or 2, characterized in that the thickness of the annular partition between the knife sections of the rotor or stator is not more than the thickness of the subsequent knife section on the rotor or stator. 4. Conical mill according to any one of paragraphs. 1-3, characterized in that the intake section of the rotor is made in the form of a truncated cone with a taper that varies by 0-65 ° compared with the taper of the subsequent sections. 5. Conical mill according to any one of paragraphs. 1-4, characterized in that for regulating the degree of grinding contains a frequency converter.

Images