RU2784084C1 - Method for selective grinding of lost strength components from multicomponent mixture of solid loose materials and device for its implementation - Google Patents

Abstract

FIELD: selective fine grinding.

SUBSTANCE: invention relates to selective fine grinding of a multicomponent mixture and can be used in chemical, construction and other industries. In the method, which consists in the outflow of the energy carrier from the nozzles for grinding a multicomponent mixture in the apparatus and sorting the crushed powder using a centrifugal classifier installed in the apparatus, a mixture of components of various strengths is crushed in countercurrent jets of a cascade of apparatuses, while the optimal speed of particle movement in the zones of collision of countercurrent jets are set equal to the values of the critical destruction rates of the components that are subjected to selective destruction by colliding particles in countercurrent jets, forming irregularly shaped fragments and intensively abrading them in the volume of the fluidized bed, using particles of stronger components as grinding bodies, while the energy carrier supply rate for the next after the first component, second in strength, is increased by a factor equal to the ratio of the second to the first ultimate strength of the crushed components. A device having apparatuses that include a grinding section, a classification section located above the grinding section, including centrifugal classifiers, is made in the form of a cascade of three apparatuses, one below the other in series and connected by overflow pipes of the most durable particles in the mixture from the first apparatus to the second, from the second, respectively, to the third, while the overflow pipes are made at the lowest point of the flat bottoms, and the bottoms are inclined at an angle of 3°-5° to the vertical axis of the apparatus, relative to which upwards and in the radial direction from the axis of the energy carrier supply nozzles at a distance of not more than 50 mm are accumulative pockets for the accumulation of solid particles of a higher concentration compared to the concentration of the solid phase in the fluidized bed and to exclude stagnant zones, which are made in the form of recesses in the form of a truncated cone.

EFFECT: method and device provide the possibility of carrying out the process of selective grinding of target components from a mixture of components with different strengths, and also make it possible to increase the degree of extraction of the least durable target components during selective grinding of a mixture of components with different strengths.

2 cl, 2 dwg, 4 tbl

Description

The invention relates to selective fine grinding of a multicomponent mixture and can be used in chemical, construction and other industries.

The studies were carried out using the resources of the Center for the Collective Use of Scientific Equipment of the ISUCT (with the support of the Ministry of Science and Higher Education of the Russian Federation, agreement No. 075-15-2021-671 dated July 28, 2021).

A jet mill is known (USSR author's certificate for the invention No. 1721890, IPC B02C 19/06. Countercurrent jet mill / Koloberdin V.I. and others; applicant Ivanovo Institute of Chemical Technology - No. 4795478/33; applicant 26.02.1990), designed for grinding bulk materials, including a grinding chamber with accelerating tubes for counter supply of energy, a branch pipe for removing the crushed mass and a cyclone for separating the latter, as well as a working container for forming a fluidized bed connected to the grinding chamber through a window in the side wall.

The disadvantage of the mill is the impossibility of carrying out the process of selective grinding of the target components from a mixture of components with different strengths.

The closest to the proposed technical solution, taken as a prototype, is a method of grinding and classifying solid materials and an apparatus for grinding and classifying in a fluidized bed (US Patent US 2004/251330A1, B02C 1/00, FLUIDIZED BED PULVERIZING AND CLASSIFYING APPARATUS, AND METHOD OF PULVERIZING AND CLASSIFYING SOLIDS, Mutsumi Takahashi, Nobuyasu Makino, Fumitoshi Murakami, Makoto Hirai, Dec. 16, 2004), which includes: the outflow of compressed air from the nozzles for grinding material in the apparatus when secondary air is supplied to it; and sorting the crushed powder using a centrifugal classifier installed in the apparatus.

The disadvantage of this method is the low efficiency of selective grinding of a multicomponent mixture.

The closest to the proposed technical solution adopted as a prototype is an apparatus for grinding and classifying in a fluidized bed (US Patent US 2004/251330A1, B02C 1/00, FLUIDIZED BED PULVERIZING AND CLASSIFYING APPARATUS, AND METHOD OF PULVERIZING AND CLASSIFYING SOLIDS, Mutsumi Takahashi , Nobuyasu Makino, Fumitoshi Murakami, Makoto Hirai, Dec. 16, 2004), having an apparatus that includes a grinding section, a grinding section with nozzles, a classification section located above the grinding section, including a centrifugal classifier, a fluidized bed.

The disadvantage of the prototype is the impossibility of carrying out the process of selective grinding of the target components from a mixture of different strength components and a low degree of their extraction.

The technical result is the possibility of carrying out the process of selective grinding of target components from a mixture of components with different strengths and increasing the degree of extraction of the least durable target components during selective grinding of a mixture of components with different strengths.

This result is achieved by the fact that in the method of selective grinding of the least durable components from a multicomponent mixture of solid bulk materials, which consists in the flow of energy from the nozzles for grinding the multicomponent mixture in the apparatus and sorting the crushed powder using a centrifugal classifier installed in the apparatus, according to the invention, the mixture of components of various strengths are crushed in countercurrent jets of a cascade of apparatuses, while the optimal particle velocities in the zones of collision of countercurrent jets are set equal to the values of the critical rates of destruction of the components, which are subjected to selective destruction by colliding particles in countercurrent jets, forming fragments of irregular shape and intensively attriting them in the fluidized volume. layer, using particles of stronger components as grinding media, while the energy carrier supply rate for the next after the first component, the second in strength, increases ut by a factor equal to the ratio of the second to the first ultimate strength of the crushed components.

This result is achieved by the fact that the device for selective grinding of the least durable components from a multicomponent mixture of solid bulk materials, having apparatuses that include a grinding section, a classification section located above the grinding section, including centrifugal classifiers, according to the invention , is made in the form of a cascade of three apparatuses , successively located one below the other and connected by overflow pipes of the most durable particles in the mixture from the first apparatus to the second, from the second, respectively, to the third, while the overflow pipes are made at the lowest point of the flat bottoms, and the bottoms are inclined at an angle of 3 ° -5 ° to the vertical axis of the apparatus, relative to which storage pockets are located upwards and in the radial direction from the axis of the energy carrier supply nozzles at a distance of not more than 50 mm for the accumulation of solid particles of a higher concentration compared to the concentration of the solid phase in the fluidized bed and to eliminate stagnation x zones, which are made in the form of recesses in the form of a truncated cone.

The invention is illustrated by drawings, where figure 1 shows a General view of the device, figure 2 - section of the device along A-A.

The device contains a bin 1 of the original multi-component material with a screw feeder 2 for continuous supply of a mixture of crushed components, which is installed above the level of the apparatuses 3, 4, 5. Each apparatus has a flat bottom 6 inclined at an angle of 3°-5° to the vertical axis of the apparatus, relative to which up and in the radial direction from the axis of the nozzles 7 for supplying the energy carrier at a distance of not more than 50 mm, storage pockets 8 are located for the accumulation of solid particles of a higher concentration compared to the concentration of the solid phase in the fluidized bed and to exclude stagnant zones, which are made in the form of recesses in the form of a truncated cone. To classify the crushed material, centrifugal classifiers 9, 10, 11 are installed in the upper part of the devices 3, 4, 5, which are connected to the nozzles 12 for the output of the crushed product. Apparatuses 3, 4, 5 are connected by overflow pipes 13 of unground materials, into which pipes 14 are mounted for additional supply of energy carrier. In the lower part of the apparatus 5 there is an outlet pipe 15 for unground materials, into which a pipe 14 is mounted for additional supply of energy carrier.

The device works as follows.

в первом аппарате 3 каскада. Измельченные частицы поступают в центробежный классификатор 9. Тонкодисперсный материал удаляют через патрубок выхода 12. Неизмельченные частицы возвращаются в накопительные карманы 8 секции измельчения, где снова подхватываются потоком энергоносителя для повторного столкновения во встречных потоках. Использование накопительных карманов 8 позволяет увеличить концентрацию измельчаемых частиц во встречных струях энергоносителя и повысить вероятность измельчения при столкновении. Более прочные компоненты смеси не измельчаются в первом аппарате 3 каскада, и направляются по наклонному под углом 3°-5° к вертикальной оси аппарата плоскому днищу 6 через патрубок перетока 13 в аппарат 4. Для предотвращения зависания материала в патрубке перетока 13 установлен патрубок 14 для дополнительной подачи энергоносителя. Процессы измельчения и классификации происходят аналогично процессам в первом аппарате 3. Во втором аппарате 4 будет избирательно измельчаться следующий по прочности компонент смеси.The initial material, consisting of a multicomponent mixture of solid particles, is continuously fed from the hopper 1 by a screw feeder 2 into the apparatus 3, where it is picked up and accelerated in the oncoming flows of the energy carrier flowing out of four nozzles 7. Upon impact in the zones of jet impact grinding, the material is crushed and ejected by the energy carrier fountain into the fluidized bed. The least durable component of the mixture is destroyed, for which the energy carrier supply rate is calculated

in the first apparatus there are 3 cascades. The crushed particles enter the centrifugal classifier 9. The fine material is removed through the outlet pipe 12. The unground particles return to the storage pockets 8 of the grinding section, where they are again picked up by the energy carrier flow for re-collision in oncoming flows. The use of storage pockets 8 makes it possible to increase the concentration of crushed particles in the oncoming jets of the energy carrier and to increase the probability of crushing in a collision. The stronger components of the mixture are not crushed in the first apparatus 3 of the cascade, and are directed along a flat bottom 6 inclined at an angle of 3°-5° to the vertical axis of the apparatus through the overflow pipe 13 into the apparatus 4. To prevent the material from hanging in the overflow pipe 13, a pipe 14 is installed for additional energy supply. The grinding and classification processes are similar to the processes in the first apparatus 3. In the second apparatus 4, the next strongest component of the mixture will be selectively ground.

, то во втором аппарате 4 при избирательном измельчении следующего по прочности компонента смеси скорость необходимо увеличить на множитель, равный отношению второго к первому пределов прочности измельчаемых компонентов:If for the first component we choose an outflow velocity equal to

, then in the second apparatus 4, during selective grinding of the next component of the mixture in terms of strength, the speed must be increased by a factor equal to the ratio of the second to the first ultimate strength of the crushed components:

.

.

The feed rate of the energy carrier or the speed of the outflow of the jets from the nozzles 7 is controlled by the flow rate of the energy carrier by adjusting the upward or downward movement of the valve locking device. The speed of rotation of the rotors of the centrifugal classifiers 9, 10, 11 is controlled depending on the particle size of the resulting fine mixture. The stronger components of the mixture are not crushed in the second apparatus of the cascade and are directed along an inclined at an angle of 3°-5° to the vertical axis of the apparatus to the flat bottom 6 through the overflow pipe 13 into the apparatus 5. The processes of grinding and classification occur similarly to the processes in the first and second apparatuses 3, 4. Unground particles are removed through the discharge pipe 15.

The method of selective grinding of a multicomponent mixture in the present invention is carried out as follows.

.A multicomponent mixture of solid components of various strengths is continuously fed into the first apparatus 3 of the proposed device - a multi-stage jet grinder with a fluidized bed, which, unlike existing jet grinders, has storage pockets 8 in the energy carrier supply zones, in which the concentration of solid particles is 1.5-1, 7 times higher than the concentration of solid particles in the volume of the fluidized bed, which leads to an increase in the concentration of solid particles in the oncoming jets and to an increase in the performance of jet grinders for a fine product at the same energy costs. In each apparatus 3, 4, 5 of the multistage grinder, the optimum particle impact rate for one of the crushed components of the multicomponent mixture is set equal to the critical rate of destruction of its particles. (Critical failure rate refers to the 50% probability of failure of the particles of a given component, which is proportional to the static compressive strength of the crushed material). The critical rate of impact destruction of particles is usually determined experimentally by single impact loading of tens of thousands of particles at different impact velocities and by measuring the probability of their destruction. It is possible to use empirical equations in which the critical impact fracture rate is related to the strength of the crushed material and the size of the crushed particles. In the article (Blinichev V.N., Postnikova I.V., Frolov S.G. Calculation of the process of grinding particles during their collision in countercurrent jets // Bulletin of universities. Chemistry and chemical technology. - 2011. - V. 54, 4. - pp. 101 - 103) we have shown that the critical impact fracture rate is proportional to the static compressive strength of the particle material. Therefore, during selective grinding in the second apparatus 4 of a stronger component of the mixture compared to the strength of the crushed component in the first apparatus 3, the energy carrier outflow rate is increased by an amount equal to the ratio of the strength of the second selectively crushed component to the first

.

During impact destruction of the least durable material, fragments of irregular shape are formed, which are easily abraded in the volume of the fluidized bed, while particles of stronger components serve as grinding media. The resulting fine particles in the jet collision zones and in the volume of the fluidized bed are carried by the energy carrier flow to the centrifugal classifier 9, 10, 11, where the largest particles are separated and returned to the bed, and the fine product is sent from the centrifugal classifier, the rotor speed of which is controlled depending on particle sizes of the resulting finely dispersed mixture, into a cyclone and a filter for separating from the energy carrier.

. Наиболее прочные компоненты непрерывно выводятся через патрубок перетока 13 во второй аппарат многоступенчатого измельчителя при подаче в патрубок 14 регулируемого расхода энергоносителя для отдувки тонкодисперсных частиц наименее прочного первого компонента, подвергаемого избирательному измельчению.In the first apparatus, the residence time of the crushed particles is maintained, sufficient to remove from it in the form of a finely dispersed product at least 90% of the least durable target component, which is equal to the ratio of the layer volume to the productivity of the apparatus

. The most durable components are continuously discharged through the overflow pipe 13 into the second apparatus of the multi-stage grinder when the energy carrier is supplied to the pipe 14 with an adjustable flow rate for blowing off fine particles of the least durable first component subjected to selective grinding.

The method of selective grinding of the next strongest component in the second apparatus of the multistage grinder is carried out similarly as in the first apparatus, but the optimal particle impact rates are increased by an amount proportional to the ratio of the compressive strengths of the second component subjected to selective grinding to the strength of the first component.

. Неизмельченные частицы удаляют через выгрузочный патрубок 15.In the third apparatus of the multi-stage grinder, the first two target components of the mixture are regrinded with the continuous withdrawal of the most durable components in the form of rock in order to enrich the first two components already at the grinding stage. The grinding process is carried out in the same way as in the first and second apparatuses with a particle impact velocity equal to the average impact velocity in the first two apparatuses.

. Unground particles are removed through the discharge pipe 15.

Example. Selective grinding of a multicomponent mixture of particles with an average size of 5 mm was performed on the example of the components of the apatite-nepheline ore of the Khibiny deposit. The initial composition of the multicomponent mixture is presented in Table 1.

Table 1 The initial composition of the crushed multicomponent mixture Component Mass percent, % Compressive strength, MPa Density, kg/m ³ Fluorapatite 36.8 55 3120 Nepheline 36.4 110 2610 Albite 6.9 150 2600 Aegirine 12.1 190 3550 Muscovite 7.4 410 2830 Titanite 0.4 120 3540

Selective grinding was carried out at optimally selected particle collision velocities in jets in order to isolate one or another component from a multicomponent mixture. For the first component, fluorapatite, the critical particle collision velocity in countercurrent jets in the first apparatus was calculated from the equation:

A sufficient critical particle collision velocity was achieved by accelerating them in the energy carrier flow flowing out of the nozzles at a speed of 180 m/s. The velocity of particles in a jet stream was calculated using a discrete mathematical model (S.V. Vorobyov, I.V. Postnikova, V.N. Blinichev. Determination of the velocity and concentration of particles of a solid phase in a turbulent gas jet immersed in a fluidized bed // Russian Chemical Journal. - 2019. - No. 3-4, vol. LXIII. - P. 31-41).

Table 2 shows the composition of the finely dispersed product carried by the energy carrier from the first apparatus of the proposed device to the second.

table 2 Mass percentage of components in the product of selective grinding of a multicomponent mixture and the extraction ratio of the target components in the first apparatus Component Mass percent, % Recovery factor, % Fluorapatite 47.2 80 Nepheline 33.1 56.5 Aegirine 5.6 - Muscovite 9.9 - Albite 3.8 - Titanite 0.4 -

In the second apparatus, during selective grinding of nepheline, the energy carrier outflow rate was increased by a factor equal to the ratio of tensile strengths:

Table 3 shows the composition of the finely dispersed product carried by the energy carrier from the second apparatus of the proposed device to the third.

Table 3 Mass percentage of components in the product of selective grinding of a multicomponent mixture and the extraction ratio of the target components in the second apparatus Component Mass percent, % Recovery factor, % Fluorapatite 25.6 99.5 Nepheline 43.4 91.2 Aegirine 8.4 - Muscovite 14.6 - Albite 7.6 - Titanite 0.4 -

In the third apparatus, fluorapatite and nepheline are regrinded, with a continuous withdrawal of the most durable components (aegirine, muscovite, albite, titanite), so the energy carrier outflow rate is equal to the average impact velocity in the first two apparatuses:

Table 4 shows the composition of the finely dispersed product carried out by the energy carrier from the third apparatus of the proposed device.

Table 4 Mass percentage of components in the product of selective grinding of a multicomponent mixture and the extraction ratio of the target components in the third apparatus Component Mass percent, % Recovery factor, % Fluorapatite 0.2 99.9 Nepheline 43.9 97.3 Aegirine 13.6 - Muscovite 20.7 - Albite 21.5 - Titanite 0.1 -

Thus, the use of the proposed method of selective grinding and a device for its implementation makes it possible to carry out the process of selective grinding of target components from a mixture of different strength components and to increase the degree of extraction of target components during selective grinding of the least durable components from an initial multicomponent mixture of solid bulk materials.

Claims (2)

1. The method of selective grinding of the least durable components from a multicomponent mixture of solid bulk materials, which consists in the outflow of an energy carrier from nozzles for grinding a multicomponent mixture in an apparatus and sorting the crushed powder using a centrifugal classifier installed in the apparatus, characterized in that a mixture of components of different strengths is crushed into countercurrent jets of a cascade of apparatuses, while the optimal particle velocities in the zones of collision of countercurrent jets are set equal to the values of the critical rates of destruction of the components, which are subjected to selective destruction by colliding particles in countercurrent jets, forming fragments of irregular shape and intensively attriting them in the volume of the fluidized bed, using in as grinding media, particles of stronger components, while the energy supply rate for the next after the first component, the second in strength, is increased by a factor equal to the ratio of the second to the first tensile strength of the crushed components. 2. A device for selective grinding of the least durable components from a multicomponent mixture of solid bulk materials, having apparatuses containing a grinding section, a classification section located above the grinding section, including centrifugal classifiers, characterized in that it is made in the form of a cascade of three apparatuses, one in series. under the other and connected by overflow pipes of the most durable particles in the mixture from the first apparatus to the second, from the second, respectively, to the third, while the overflow pipes are located at the lowest point of the flat bottoms, and the bottoms are inclined at an angle of 3°-5° to the vertical axis of the apparatus , relative to which storage pockets are located upwards and in the radial direction from the axis of the energy carrier supply nozzles at a distance of not more than 50 mm for the accumulation of solid particles of a higher concentration compared to the concentration of the solid phase in the fluidized bed and to exclude stagnant zones, which are made in the form of recesses in the shape of a truncated cone.

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