RU2055651C1 - Pneumatic classifier - Google Patents

Abstract

FIELD: chemical engineering. SUBSTANCE: pneumatic classifier has housing made of a set of vertical separation columns, distributing lattice on the ends of which charging and discharging branch pipes are mounted, branch pipes for air feeding and outletting of dust-air mixture. Pressure chambers with nozzle members in overscreen part are fastened on housing from exterior side. Additional distributing lattice is located between charging branch pipe and distributing lattice. Adjusted louvers are mounted between separation columns and distributing lattice. Separation columns have garlands made of buckets and flow splitters connected by rods. The rods are suspended to balance beams attached to vibration drive. EFFECT: enhanced efficiency of classification of granular materials. 2 cl, 6 dwg

Description

 The invention relates to the construction materials industry, the processing of coal, ores, mineral fertilizers, etc. It can be used to classify various bulk materials according to the size limit of 0.07-3.0 mm.

 Known combined cascade classifier, made of a set of vertical separation columns with overflow shelves located above an inclined gas distribution grid. The classifier is equipped with loading and unloading nozzles, nozzles for supplying air and removing dust-air mixture (Barsky M.D. Fractionation of powders. M. Nedra, 1980, p. 327, Fig. 33). The disadvantage of this classifier is the short residence time of the material on the grate, insufficient dispersion of the material on the grate, sticking of the material in the separation columns above and below the overflow shelves. All this reduces the efficiency of the classification process and the reliability of the apparatus. In addition, when combining heat treatment processes, the intensity of the heat exchange process between the gas and solid phases is low.

 The closest set of essential features is the gravity pneumatic classifier made of a set of vertical separation columns with leveling gratings, a perforated distribution grate installed under them, loading and unloading devices and nozzles for supplying air under the distribution grate and for discharging dust-air mixture [1] design is the low reliability of the apparatus due to the sticking of the material on the leveling gratings. The design does not provide for mechanical cleaning of these gratings without stopping the apparatus. The heat exchange between the gas and solid phases is not intense, because the air velocity in the oversize part is 1-8 m / s. The residence time of the material on the distribution grid is small, which reduces the severity of separation and the efficiency of heat treatment of the material.

 The task of increasing the efficiency of heat treatment, the severity of the separation of the material and improving the reliability of the apparatus is solved by the proposed invention, the essence of which is as follows.

 In the pneumatic classifier, which includes a housing, a distribution grid, separation columns located above it, inlet pipes for air and granular material, pipes for removal of separation products, an additional distribution grid located between the loading pipe and the main distribution grid, to the side walls of the apparatus from the outside fixed pressure chambers with nozzle elements in the oversize part, between the separation columns and the distribution grill are mounted mye shutters, and the separation column provided with garlands suspended from the link bodies, which are connected with the vibratory drive.

 Salient features of the claimed device are a housing, loading and unloading nozzles, air supply and dust-air mixture nozzles, a distribution grill, an additional distribution grill, separation columns with garlands suspended inside them, consisting of baskets and flow dividers, pressure chambers mounted on the side walls of the apparatus and equipped with nozzle elements in the oversize part, shutters installed between the separation columns and the distribution grid.

 Distinctive features of the proposed invention from the known are: installation along the distribution grid from the outside of the housing of the pressure chambers with nozzle elements in the oversize part; installation of blinds between separation columns and distribution grid; installation of garlands in separation columns with the possibility of periodic shaking; installation of an additional distribution grid between the loading nozzle and the main distribution grid.

 Fixing pressure chambers with nozzle elements on the side walls of the apparatus makes it possible to intensify the heat exchange process between the gas and solid phases, since the speed of gas jets is 60-120 m / s, increases the porosity of the layer, and the dispersion of the processed material.

 The presence of blinds in a fluidized bed reduces the speed of longitudinal movement of the material along the distribution grid, increasing the residence time of the material on the grid and thus the severity of separation, the time of heat treatment.

 Finely dispersed particles carried by the air flow from the material layer into the separation columns, having hit the elements of the garlands, lose their speed. Particles of material having a particle size exceeding that of the boundary grain are poured from the separation columns into a fluidized bed. Particles of material having a particle size smaller than the boundary grain are again accelerated by the air flow in the separation column, because have a speed of soaring less than the speed of the gas stream. Thus, multiple refining of both large and small products occurs, which ensures effective classification of the material.

 An additional distribution grid provides preliminary dispersion of the material, its additional winnowing.

 Periodic shaking of the garlands ensures the reliability of the device, since it allows them to be mechanically cleaned without stopping its operation.

1

(1) где Е эффективность классификации по критерию Ханкока-Луйкена, доли ед.The dependence of the classification efficiency of such devices on operational and structural parameters can be represented by the formula:
E

1

(1) where E is the classification efficiency according to the Hankok-Luiken criterion, fractions of units.

β ₀ mass fraction of fines in the source material, fractions of units

ρ _{d the} density of the dispersed phase, kg / m ³ ;
ε porosity of the layer of material on the lattice, fractions of units

h the height of the fluidized bed, m;
τ the residence time of the material on the lattice, s;
μ consumption concentration of the material, kg / m ³ ;
W air flow rate in the oversize zone of the apparatus, m / s;
α angle of inclination of the lattice to the horizontal, deg.

R _{m is the} product of the mass fraction of particles larger than the boundary grain in a small product and the yield of a small product, fractions of units

From the formula (1) it follows that to increase the classification efficiency it is necessary:
organize the cleaning of a small product (reduce R _m );
increase the porosity of the material layer on the distribution grid ε;
increase the residence time of the material on the lattice τ.

 The invention is illustrated by drawings, where in FIG. 1 shows a general view of a pneumatic classifier; in FIG. 2 view along arrow A from the end; in FIG. 3, section AA in FIG. 1; in FIG. 4 distribution grid design; in FIG. 5 design of the installation of garland elements in a separation column; in FIG. 6 flow divider.

 The pneumatic classifier includes a housing 1, consisting of separation columns 2 with garlands suspended on them on the rods 3, a U-shaped distribution grid 4, nozzle elements 5, an additional distribution grid 6, a loading nozzle 7 with a loading device 8, a large product unloading nozzle (K ) 9 with a discharge device 10, an air supply pipe (B) 11, a dust-air mixture discharge pipe (B + M) 12, baskets 13, flow dividers 14, pressure chambers 16, shutters 15, springs 17.

 Recommended aspect ratios of the main elements of the garlands are shown in FIG. 5.

 Pneumatic classifier works as follows. The source material (IM) through the loading pipe 7 enters an additional distribution grid 6, where it is dispersed and pre-screened, while the finely dispersed fraction is carried away by air flow into the first separation column. The main stream of source material from the additional distribution grid 6 is poured onto the main distribution grid 4 of a wireless type, through which slots air passes. Air is sucked into the apparatus through the nozzle 11 during operation of the fan installed after the dry dust cleaning system (not shown). On the distribution grid 4, a fluidized bed is formed, which is treated with jets of air (coolant or refrigerant depending on the task) emerging from the nozzles 5. In the fluidized bed during blasting of the material, intense heat exchange occurs between the solid and gas phases. Air, filtered through a fluidized bed, carries fine particles into the separation columns. Particles of material with a grain size larger than the boundary grain carried by the dust and gas stream into the separation columns, when they hit the elements of the garlands 14, 13, lose their speed along the walls of the separation columns, where the velocity of the upward stream is lower than in the core of the stream, they are poured onto the distribution grid 4 into a fluidized bed . The finely dispersed fraction (B + M) is removed from the apparatus with an air flow through the nozzle 12. Upon impact on the louvre plate 15, the particles of the processed material change their motion path to an upward and downward flow, which increases the residence time of the material in a fluidized bed.

 Garlands are cleaned periodically by shaking them when vibrodrives are turned on without interrupting the processing of material in the apparatus.

 To change the separation boundary, it is enough to change the flow rate of air passing through the pipe 11.

 U-shaped distribution grid provides a more uniform distribution of air flow rates over the separation columns, the compactness of the apparatus.

 Uralkali joint-stock company conducted tests of a pilot industrial prototype of the claimed pneumatic classifier for dust removal and cooling of potassium chloride.

Technical characteristic of pneumatic classifier. Productivity, t / h 80 Separation boundary, mm 0.1-0.2 Distribution grill area, m ² 5 Air flow through the apparatus, thousand m ³ / h 20-30 Live cross-section of the distribution grill, 12 Distribution tilt angle grating, city 10 Dimensions: length, m 4,5
width, m 4.2
height, m 5.5
Apparatus Tests have shown that the source material temperature is reduced from 110-118 ^C to 50-60 ^{° C} (in the summer).

 The residence time of the material on the grate in the absence of blinds in the apparatus was 30 s, in the presence of blinds 33 s.

 Granular compositions of the source material and classification products are presented in the table.

 The dust product yield was 9.1% classification efficiency by the criterion: Hankok-Luiken 94.7% Eder-Mayer 60% separation boundary 0.1 mm.

 The presence of blinds 15 allows you to guaranteed to receive a dust-free product with a mass fraction of class -0.1 + 0 mm not more than 1%

Claims (3)

 1. Pneumatic classifier, comprising a housing made of a set of vertical separation columns, a distribution grill installed beneath them, at the ends of which there are loading and unloading pipes, air supply and dust-air mixture discharge pipes, characterized in that it is equipped with an additional distribution grid located between the loading branch pipe and distribution grill, pressure chambers located on the outside of the housing, with nozzle elements in the oversize part, shutters, laid between the separation columns and the distribution grid, garlands in the separation columns made of baskets and flow dividers connected by rods hanging on the rocker arms, which are connected to vibration drives.  2. The pneumatic classifier according to claim 1, characterized in that the distribution grid can be made U-shaped.  3. The pneumatic classifier according to claim 1, characterized in that the blinds are offset one from another, and the projections on the vertical plane of adjacent blinds are mutually overlapped.

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