RU225353U1 - Counterflow Fluidized Bed Jet Mill - Google Patents

Abstract

The utility model relates to devices for fine grinding of various solid materials and can be used primarily in the chemical industry, as well as in the mining industry and the construction materials and ceramics industry. The technical result of the utility model is to increase the efficiency of fine grinding, reduce wear on the internal elements of the mill and simplify the design by creating a circulating two-phase (gas + particles of solid material) flow inside the grinding chamber and uniformly filling countercurrent two-phase jet streams with particles of solid material. This result is achieved by the fact that in a countercurrent jet mill with a fluidized bed, containing a grinding chamber made in the form of a vertically located body, at the top of which there is a pipe for removing the dust and gas mixture, a horizontal gas distribution grid located in the lower part of the grinding chamber, an under-grid box and a fitting for supplying compressed air to create a fluidized bed, located under a horizontal gas distribution grid, counter-directionally located, at least two nozzles for continuous and/or pulsed supply of compressed air to create countercurrent two-phase jets, located at a distance of 50 mm upward from the horizontal gas distribution grid on its vertical planes of symmetry in the radial direction from the axis of the grinding chamber, according to the utility model, the grinding chamber is made with a variable cross-section, which, expanding in the lower part at the installation site of the horizontal gas distribution grid, forms storage pockets; a centrifugal classifier for separation is installed in the upper part of the grinding chamber crushed particles of a given size and return of the coarse fraction to final grinding, at a distance of at least 300 mm upward from the horizontal gas distribution grid in the radial direction from the axis of the grinding chamber, a screw feeder is located, with the help of which the source material is supplied from the hopper. 2 ill.

Description

The utility model relates to devices for fine grinding of various solid materials and can be used primarily in the chemical industry, as well as in the mining industry and the construction materials and ceramics industry.

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

A disadvantage of the device design is the low concentration of particles of solid material in colliding two-phase (gas + particles of solid material) jet streams due to the absence of storage pockets in the area of their discharge, as a consequence, reduced productivity of the device for finely dispersed product

A jet mill is known (USSR author's certificate for invention No. 1721890, IPC V02S 19/06. Countercurrent jet mill / Koloberdin V.I. et al.; applicant and patent holder: Ivanovo Institute of Chemical Technology - No. 4795478/33; application 26.02. 1990), designed for grinding bulk materials, including a grinding chamber with accelerating tubes for counter supply of energy, a pipe for discharging the crushed mass and a cyclone for separating the latter, as well as a working container for the formation of a fluidized layer, connected to the grinding chamber through a window in the side wall.

A disadvantage of the jet mill design is the low concentration of particles of solid material in colliding two-phase (gas + particles of solid material) jet streams due to the absence of storage pockets in the area of their discharge, as a result, reduced productivity of the device for finely dispersed product

The closest to the proposed design is a counterflow jet mill [USSR author's certificate for invention No. 1162487, MPK - 2006.01 B02S 19/06 Counterflow jet mill; application 12/27/1983; publ. 06.23.1985]. The counterflow jet mill contains a grinding chamber, at least two high-pressure air supply nozzles located opposite each other, a feed pipe for supplying the source material, a fitting for the output of an air suspension with crushed material for classification, and a fitting for returning the coarse fraction from the classifier to finishing grinding. The grinding chamber is made in the form of a vertically located body, in the lower part of which, under the nozzles, a horizontal grate and an under-grid box with air intake windows are mounted.

The following set of prototype features coincides with the essential features of the claimed utility model: a grinding chamber with at least two high-pressure air supply nozzles located towards each other, the grinding chamber is made in the form of a vertically located body, in the lower part of which, under the nozzles, a horizontal grid is mounted and sub-grid box.

The disadvantages of the prototype are: wear of the nozzles and a decrease in grinding efficiency due to the displacement of the collision nucleus of particles of solid material due to the uneven filling of countercurrent two-phase jets in the process of replenishing the mass of crushed material removed from the layer with the source material and returning particles with sizes larger than the particles of the commercial product through the coarse return fittings fractions, the possibility of clogging of the coarse fraction return fittings.

The technical result of the utility model is to increase the efficiency of fine grinding, reduce wear on the internal elements of the mill and simplify the design by creating a circulating two-phase (gas + particles of solid material) flow inside the grinding chamber and uniformly filling countercurrent two-phase jets with particles of solid material.

This result is achieved by the fact that in a countercurrent jet mill with a fluidized bed, containing a grinding chamber made in the form of a vertically located body, at the top of which there is a pipe for removing the dust and gas mixture, a horizontal gas distribution grid located in the lower part of the grinding chamber, an under-grid box and a fitting for supplying compressed air to create a fluidized bed, located under a horizontal gas distribution grid, counter-directionally located, at least two nozzles for continuous and/or pulsed supply of compressed air to create countercurrent two-phase (gas + particles of solid material) jet streams, located on at a distance of 50 mm upward from the horizontal gas distribution grid on its vertical planes of symmetry in the radial direction from the axis of the grinding chamber, according to the utility model, the grinding chamber is made with a variable cross-section, which, expanding in the lower part at the installation site of the horizontal gas distribution grid, forms storage pockets in the upper Part of the grinding chamber, a centrifugal classifier is installed to separate crushed particles of a given size and return the coarse fraction to final grinding; at a distance of at least 300 mm upward from the horizontal gas distribution grid in the radial direction from the axis of the grinding chamber, a screw feeder is located, with the help of which the source material is supplied from the hopper.

The essence of the utility model is illustrated by graphic materials, where

in fig. 1 shows a counterflow fluidized bed jet mill in a longitudinal section;

in fig. Figure 2 shows a counterflow fluidized bed jet mill in a horizontal section.

A counterflow jet mill with a fluidized bed contains a grinding chamber 1, made in the form of a vertically located body with a variable cross-section, which, expanding in the lower part, forms storage pockets 2, a horizontal gas distribution grid 3 located in the lower part of the grinding chamber 1 under storage pockets 2, subgrid box 4 and fitting 5 for supplying compressed air to create a fluidized bed, located under the horizontal gas distribution grid 3, screw feeder 6 for continuous supply of source material from hopper 7 to the grinding chamber 1, located at a distance of at least 300 mm up from the horizontal gas distribution grid 3 in the radial direction from the axis of the grinding chamber 1, at least two counter-directional nozzles 8 for continuous and/or pulsed supply of compressed air to create countercurrent two-phase (gas + particles of solid material) jet streams, located at a distance of no more than 50 mm up from gas distribution grid 3 on its vertical planes of symmetry in the radial direction from the axis of the grinding chamber 1, a centrifugal classifier 9 for separating crushed particles of a given size and returning the coarse fraction to final grinding, located in the upper part of the grinding chamber 1, a pipe 10 for removing the dust-gas mixture, located after centrifugal classifier 9.

The counterflow fluidized bed jet mill works as follows:

The source material is continuously fed by a screw feeder 6 from the hopper 7 into the grinding chamber 1, in which it is fluidized on the horizontal gas distribution grid 3 due to the supply of compressed air under the horizontal gas distribution grid 3 into the subgrid box 4 through fitting 5. Particles of solid material ejected from the fluidized bed collide in the collision core of two-phase (gas + particles of solid material) jet streams formed due to continuous and/or pulsed supply of compressed air into at least two counter-directional nozzles 8.

Due to the kinetic energy of two-phase (gas + particles of solid material) jet streams of one pair of nozzles 8 colliding with each other and the resulting particle fragments flying to the sides, the storage pockets 2 are instantly filled and the conditions for the entry of particles into the discharge zones of the flowing jets from the nozzles 8 are created from the initial speed different from zero, which significantly increases the maximum speed of movement of particles in the jets and the productivity of a fluidized bed jet mill for a finely dispersed product.

Analysis of the hydrodynamic regime of particle movement in storage pockets showed that particles of solid material move directionally in them, at the bottom of the nozzle - from bottom to top into the jet rarefaction zone, from the side - radially to the nozzle, from above - from top to bottom. At the same time, the concentration of solid particles in storage pockets 2 is 1.52 times higher than in the fluidized bed, therefore the concentration of particles of solid material in each two-phase (gas + particles of solid material) jet flow is also significantly higher, and the efficiency of each pair of nozzles increases, so how specific energy costs per ton of finely dispersed material produced are reduced.

A higher concentration of particles of solid material in storage pockets 2 eliminates the possibility of wear of the mill walls when grinding abrasive materials and contamination of the crushed materials with grinding products.

In addition, storage pockets 2 are continuously filled due to the fluidization of the remaining part of the layer of particles of solid material, which receive the energy of flying fragments formed as a result of the collision of two-phase jet flows (gas + particles of solid material) and carry out secondary grinding (abrasion) due to numerous collisions of a large number particles with lower mutual collision velocities.

The abrasion rate is extremely dependent on the strength of the particles of the solid material, increasing nonlinearly as it decreases. Therefore, the fluidized bed is not only a supplier of solid particles to the storage pockets 2 of the jet grinding, but also a second volumetric zone of fine grinding.

Studies have shown that the productivity of a countercurrent jet mill with a fluidized bed for abrading particles of solid materials in a fluidized bed and obtaining a finely dispersed product is 5÷7% of the total productivity.

Analysis of the granular composition of abrasion products of materials of different strengths in a fluidized bed without the operation of a centrifugal classifier 9, carried out on an Analysette - 22 device, shows that the average particle size of abrasion products fluctuates in the range of 922 microns.

The finely dispersed particles formed in the collision zones of two-phase (gas + particles of solid material) jet flows and in the volume of the fluidized bed are carried by an air flow to the centrifugal classifier 9, where large particles are separated and returned to the layer for final grinding, and a finely dispersed product of a given size is sent from the centrifugal classifier 9 , the rotor speed of which is adjusted depending on the particle size of the resulting finely dispersed mixture, into a cyclone and a filter (not shown in the drawing) for separation from air.

The use of the proposed utility model will allow, firstly, to increase the concentration of particles of solid material in colliding two-phase (gas + particles of solid material) jet streams, increase their maximum speeds and, as a result, increase the productivity of a countercurrent jet mill with a fluidized bed by up to 30% finely dispersed product at the same compressed air parameters as without storage pockets, and, secondly, to completely protect the mill walls from wear and prevent contamination of finely dispersed products with grinding products.

Claims (1)

A counterflow jet mill with a fluidized bed, containing a grinding chamber made in the form of a vertically located body, at the top of which there is a pipe, a horizontal gas distribution grid located in the lower part of the grinding chamber, an under-grid box and a fitting located under the horizontal gas distribution grid, oppositely located, at least two nozzles located at a distance of 50 mm upward from the horizontal gas distribution grid on its vertical planes of symmetry in the radial direction from the axis of the grinding chamber, characterized in that the grinding chamber is made with a variable cross-section, which, expanding in the lower part at the installation site horizontal gas distribution grid, forms storage pockets, a centrifugal classifier is installed in the upper part of the grinding chamber, a screw feeder is located at a distance of at least 300 mm upward from the horizontal gas distribution grid in the radial direction from the axis of the grinding chamber.