EP0918573B1 - Air classifier with centrifugal action - Google Patents

Abstract

A centrifugal type pneumatic separator having a rotor and a housing. The rotor has a plurality of vanes distributed around a periphery thereof. The housing contains the rotor. The housing has an air input conduit, a material input conduit and an evacuation conduit. The air input conduit passes air through channels formed between adjacent vanes such that air and material flows toward the evacuation conduit. The rotor is divided so as to define at least two separate passages whereby air from the air input conduit flows toward the evacuation conduit as two separate and parallel streams.

Description

The present invention relates to a pneumatic separator with centrifugal action intended to classify a granular material into a fine fraction and a coarse fraction and comprising a rotor with vertical axis provided with blades regularly distributed on its periphery, guide vanes arranged around the rotor, along the generatrices of a fictitious cylinder, and able to communicate with a current of air or other gas entering said fictitious cylinder a rotational movement around the axis of said cylinder, and an envelope in which are enclosed the rotor and the guide vanes and which is provided with one or more air inlets and for the material to be classified, an outlet orifice placed above or below the rotor and through which is drawn the air stream charged with the fine fraction of the material and at least one outlet for the coarse fraction, the air entering the rotor at its periphery, through the channels formed between the blades, and flowing inside the rotor towards the outlet.

In a separator of this type the material to be classified and the air flow can be introduced separately inside the annular section space delimited by the blades and the rotor, or the material to be classified, can be suspended in the air stream before it is admitted into said space, through the blades; the air flow enters then in the rotor and is discharged through the outlet.

In both cases, the air flow and the material to be classified are rotated, around the rotor axis, in the annular section space between the rotor and the blades guidelines. The particles constituting the coarse fraction of the material are projected by the centrifugal force generated by this rotation against the guide vanes and fall by gravity in a collecting hopper with an outlet, while the particles constituting the fine fraction are entrained by the air flow through the rotor and the orifice central exit.

The separated fine fraction contains practically all the particles whose size is less than a first dimension while the coarse fraction contains practically all particles larger than a second dimension, larger than the first. In addition, both fractions contain particles whose size is included between the first and second dimensions. This results in a sharing curve comprising two substantially horizontal portions connected by an inclined portion, the slope characterizes the separator.

The distribution of particles of intermediate size in one or other of the fractions characterizes the cutting precision of the separator. In general, we seek to obtain, by construction, a cut as clear as possible between the two fractions, that is to say reduce the gap between the first and second dimensions, which results in a curve of steep sharing.

In some cases, the product we are looking for must have a particle size distribution different from that of the fraction, fine or coarse, obtained by means of a separator of this type. It is in particular the case of cement obtained by crushing by compression of the clinker. So far, the only solution to solve this problem was to use two separators placed in series or in parallel and adjusted for cut-off dimensions different. This solution is expensive.

For example, document DE 90 17 176 describes a separator with centrifugal air, in which the air is separated into several streams. according to a first variant, the separator comprises a rotor assembly consisting of four coaxial units which have the same rotational speed. He is not possible to adjust the speed and / or the flow of the different air currents between them. According to another variant, the separator comprises two rotors independent, which is an expensive solution, and more difficult to implement in action.

The purpose of the present invention is to improve the separators of the type concerned so that it is possible to adjust so simple the slope of the partition curve, i.e. to modify the distribution particle size of the size between the first and second dimensions.

The separator object of the invention is characterized in that it has a single rotor divided into sectors and in that the air circulating in the rotor between the inlet and the exhaust duct is divided into at least two separate currents, and in that the rotor is equipped with means for adjusting the speed and / or flow of at least one of the currents.

If the velocities of the two air streams in the channels between the rotor blades are set to different values, the drag forces exerted by the two currents on a particle of mass and given dimensions will be different; in the channels where the air flow travels at reduced speed, the balance between the drag forces and the forces centrifugal, which corresponds to the theoretical cutoff mesh, will occur for a smaller particle size than that for which this equilibrium is produced in other channels where the air speed is higher. Everything is will therefore pass as if we had two separators in parallel with different cutting meshes; by adjusting the velocities of the air currents, we will be able to adjust the cutoff meshes and, consequently, the distribution particle size distribution in the finished product.

The means for adjusting the speed and / or the flow of drafts can be formed by means for varying the inlet section of at least some of the channels formed between the blades of the rotor and / or by means for varying the cross section of the openings through which air currents escape from the rotor.

According to a particular embodiment, the rotor is divided in sectors by vertical partitions arranged radially and each sector communicates with the air outlet orifice through an opening provided with means for adjusting the passage section which may be formed, for example for example, by pivoting shutters or diaphragms; in this form of realization the radial partitions fulfill the anti-vortex function of the second set of blades of the separator object of French patent N ° 90 01673 in the name of applicant,

To vary the section of the channels formed between the rotor blades, it is possible to using plates placed in said channels, each plate being mobile, for example by rotation about an axis parallel to the axis of the rotor, between a first position where it leaves practically the entire section of the respective channel free, and a second position where it almost completely closes the canal.

We can, for example, place at the outlet of the channel two pivotally mounted plates on a vertical axis arranged in the median plane of the channel, these plates can be brought, by an appropriate mechanism, from a first position where they are pressed against each other and arranged practically in said median plane in a second position where their free ends are in abutment against the end of the blades defining the channel.

As a variant, certain blades of the rotor may be orientable around vertical axes. so that their ends can come to rest on a neighboring blade to seal the channel which they delimit.

Another solution is to make the blades in two parts: a fixed part and a mobile part, orientable by rotation around a vertical axis. For example, one of the faces of the blade can be fixed and the other mobile and able to pivot around a vertical axis located near the periphery of the rotor to come to rest on the neighboring blade to close the channel they form. According to another embodiment, the radially outer part of the blade can be fixed and its inner part rotatable, the movable parts of two neighboring blades can be brought into abutment against each other to close the channel delimited by the two blades.

La figure 1 est une vue en coupe diamétrale d'un rotor de séparateur conforme à l'invention ;

La figure 2 est une vue de dessus du rotor de la figure 1, l'anneau fermant partiellement le rotor à sa partie supérieure ayant été enlevé sur une moitié du rotor ;

La figure 3 est une vue à plus grande échelle d'un détail du rotor ;

Les figures 4 et 5 sont des vues analogues à la figure 3 illustrant des variantes de réalisation ;

La figure 6 est une vue en coupe diamétrale d'un autre rotor de séparateur conforme à l'invention ; et

La figure 7 montre les courbes de partage d'un séparateur classique et du séparateur objet de l'invention.

Other characteristics of the subject of the invention will appear on reading the description which follows and refers to the accompanying drawings which show, by way of nonlimiting example, several embodiments of the invention. In these drawings:

Figure 1 is a diametrical sectional view of a separator rotor according to the invention;

Figure 2 is a top view of the rotor of Figure 1, the ring partially closing the rotor at its upper part having been removed on one half of the rotor;

Figure 3 is an enlarged view of a detail of the rotor;

Figures 4 and 5 are views similar to Figure 3 illustrating alternative embodiments;

Figure 6 is a diametrical sectional view of another separator rotor according to the invention; and

Figure 7 shows the partition curves of a conventional separator and the separator object of the invention.

The separator object of the invention is of the type described in the French patent n ° 90.01673 to which one can refer for more details. As described above, there comprises a rotor with vertical axis, guide vanes arranged around the rotor and a envelope in which the rotor and the guide vanes are enclosed and which is provided with a or several inlets for the product to be classified and for the air flow, one or more outlets for the coarse fraction and a central outlet for the air stream charged with the fine fraction of the product.

The rotor 10 is fixed to the lower end of a vertical shaft 11 mounted, by by means of rolling bearings, in a tubular support 12 fixed on the ceiling of the separator shell. The shaft is coupled to a variable speed control group allowing the rotor to rotate at the desired speed.

The rotor has a large number of vertical blades 14 regularly spaced on its periphery and whose lower and upper ends are fixed, respectively, on a bottom 16 and on a ring 18. A cylindrical shell 20 fixed on the inner edge of the ring 18 defines an outlet passage for the air charged with particles of small dimensions which have entered the rotor through the channels 15 formed between the blades 14. This ferrule is connects, by a rotating joint, to the lower end of a through-pipe 22 the ceiling of the separator envelope.

The interior of the rotor is divided into four equal sectors by four vertical partitions 24 arranged radially. These partitions are fixed on the bottom 16, on the ring 18 and on a ferrule 26 surrounding the lower part of the tubular support 12 and itself fixed on the background 16.

The outlet opening delimited by the ring 18 and the ferrule 26 is partially closed by pivoting flaps 28 (two per sector in the embodiment shown). Each flap is fixed on a shaft 30 mounted on bearings fixed on the ring 18 and the ferrule 26. A square provided at the outer end of each shaft 30 makes it possible to adjust the orientation of the flaps and, therefore, the section of the exit opening of the respective sectors, and a system of locking keeps the shutters in the desired position after adjustment.

In the rotor sector represented on the lower left part of FIG. 2, a blade 14 on two is formed by a fixed part 31 constituting the active face and a part mobile 32 orientable around a vertical axis 33 located near the leading edge of the blade (see figure 3). This part 32 is movable, between a first position (represented by a line continuous in FIG. 3) where it is pressed against the fixed part 31 of the blade, so as to leave free entry of channel 15, and a second position (shown in dashed lines) where it closes completely this entry. The orientation of the moving parts of the blades can be controlled individually or in groups. These two-part blades should be distributed over the periphery of the rotor so that it is balanced. We could, for example, equip two diametrically opposite sectors of the rotor.

Figure 4 shows another embodiment of the sealing means of certain rotor channels 15. According to this variant the two blades delimiting a channel are in two parts: an external part 31 ′ which is rigidly fixed to the structure of the rotor and a lower part 32 'which is able to pivot about a vertical axis 33'. A mechanism for control, not shown allows the movable part 32 ′ of each blade to be moved between two positions: a first position, shown in solid lines in FIG. 4, where the parts 31 ' and 32 'are in the extension of one another and the channel 15 is completely cleared, and a second position, shown in phantom, where the free ends of the parts 32 'of the two blades are in abutment against each other and the channel 15 is closed.

In the variant of FIG. 5, the means for closing the channels consist of pairs of vertical plates 40 placed inside the rotor, the two plates of a pair being articulated by their inner edge on the same vertical axis 42 disposed in the plane median of the canal. A cam 44 placed between the two plates and controlled by a mechanism suitable allows to separate the two plates to bring their free end into abutment against the blades 14 and close the outlet of the channel 15, as shown in solid lines in the figure. When the cam is rotated to bring it into the median plane of the channel, the plates 40 are pressed against the cam by centrifugal force, as shown in dashed lines on the figure, and the outlet of channel 15 is almost completely clear.

According to another variant, not shown, certain blades 14 could be orientable being mounted so that it can pivot on the rotor around vertical axes located near their leading edge and come up against the neighboring fixed or orientable blades to close off the corresponding channels 15.

In service, the separator is incorporated into a circuit, open or closed, where a gas stream, for example an air stream. When entering the rotor the air flow divides into as many elementary currents as there are channels 15 between the blades 14. At the outlet channels these elementary currents are grouped in each sector of the rotor into four secondary currents which escape through the outlet opening delimited by the ring 18 and the ferrule 26. If all the flaps 28 are in the vertical position and if all the channels 15 are open, the flows of the four secondary currents are equal and the velocities of the currents elementary are equal; the operation of the separator is the same as that of a classic separator.

If part of the channels 15 are closed in one of the sectors of the rotor and simultaneously the shutters 28 are partially closed in the other sectors, so that the air flow is divided in two different currents such as the flow through each of the sectors whose flaps 28 are closed or less than the flow through the sector with the flaps open, the speed air in the 15 open channels of the first sector will be, for these two reasons, more higher than in other sector channels. Since the drag forces which act on the particles and oppose the centrifugal force in the channels 15 depend the air speed, while the centrifugal forces depend only on the speed of rotation of the rotor, the particle size for which the centrifugal and drag forces are balanced (theoretical cutoff mesh) will be more important in the first sector than in the others. Everything happens as if we had two separators working in parallel with different cutting meshes and the fine fractions of which would be mixed with the separator outlet. By adjusting the air inlet section in one or more sectors of the rotor and by adjusting the air flows circulating in the different sectors, you can select two or more different cutoffs to obtain distribution desired size within a given range.

FIG. 7 shows by way of example the partition curves of a conventional separator, for two cut-off links, and a separator according to the invention. The sharing curve gives the weight proportion, expressed in%, of the particles of size given in the fraction coarse; we would get an inverted curve for the fine fraction. For dimensions of particles smaller than 20 µm and larger than 200 µm, the three curves are combined. In the 20-200 µm range, the dashed curve corresponds to a conventional separator whose theoretical cutoff mesh is 50 µm, the dotted one corresponds to a separator classic with a theoretical cutting mesh of 105 µm. The solid line curve has been obtained with the separator of the invention; we see that its slope is lower than that of conventional separators, which means that in the 20-200 µm range, the particle size is more spread.

The invention therefore makes it possible to have a partition curve with adjustable slope and, by Therefore, to obtain a finished product having the desired particle size distribution in a particle size range given by varying both the speed of the rotor and the orientation of the guide vanes, on the one hand, and the positions of the flaps 28 and the adjustment of the section of the channels 15, on the other hand.

Instead of being divided into sectors by radial partitions, the rotor could be designed as shown in FIG. 6 and divided into two parts 46, 48, by a horizontal partition 50, located for example at mid-height, an opening 52 provided in the upper wall of the rotor communicating the upper part of the rotor with the air exhaust duct 22 of the separator and a ferrule 54 whose diameter is less than that of said opening 52 being connected to a central opening 56 of the partition and delimiting a passage 55 making communicate the lower part of the rotor with the exhaust duct 22 through the first opening. The rotor is provided with means such as those illustrated in FIGS. 3, 4 and 5 for close off some of the channels formed between its blades, over at least part of their height, and means such as the flaps 28 for adjusting at least one of the outlet openings. next the same principle, the rotor could be divided into more than two superimposed parts. We could even remove the horizontal partition (s), dividing the air in two or more currents in the rotor resulting from the arrangement of one or more dip tubes placed in the rotor axis.

Means other than pivoting shutters, for example diaphragms, could be used to adjust the section of the rotor outlet openings. It is understood that these modifications and any that may be made to the embodiments described, by the use of equivalent technical means, fall within the scope of the invention.

Claims (14)

1. A centrifugal action air separator comprising a rotor (10), with vertical pin (11) fitted with blades (14) spaced regularly on its periphery, guide vanes arranged around the rotor (10) and a shroud containing the rotor (10) and the guide vanes and fitted with air inlets and for the material to be classified, with an exhaust conduit (22) for the air loaded with the fine fraction of the material and with an outlet for the rough fraction, the air penetrating the rotor (10) at its periphery, via the channels (15) formed between the blades (14), and circulating inside the rotor (10) towards the exhaust conduit (22), characterised in that the separator comprises a single rotor, in that the rotor (10) is divided into sectors, in that the air circulating between the inlet and the exhaust conduit (22) is divided into at least two distinct currents, and in that the rotor (10) is fitted with means for adjusting the speed and/or the flow rate of the different currents relative to one another.
2. A separator according to claim 1, characterised in that said rotor is fitted with means (32, 32', 40) to vary the cross section of at least some of the channels (15) through which one of the air currents penetrates inside the rotor.
3. A separator according to claim 1 or 2, characterised in that said rotor is fitted with means (28) to vary the cross section of the opening through which at least one of the air currents exits the rotor towards the exhaust conduit (22).
4. A separator according to claim 1, 2 or 3, characterised in that said rotor is divided into sectors by vertical walls (24) arranged radially and each sector communicates with the outlet passageway via an aperture fitted with means (28) for adjusting the cross section of the air passageway.
5. A separator according to claim 1, 2, or 3, characterised in that said rotor is divided into two parts (46, 48) by a horizontal wall (50), in that the portion (48) of the rotor furthermost from the exhaust conduit (22) communicates with the latter via a passageway (55) delineated by a coaxial ferrule (54) connected to a central aperture (56) of said wall, in that the other portion (46) of the rotor communicates with said exhaust conduit via an annular aperture (52) surrounding said ferrule, and in that means are provided to vary the cross section of at least some of the channels laid out between the blades (14) in at least one of the portions of the rotor and to vary the cross section of said passageway (55) and/or said annular aperture (52).
6. A separator according to claim 4 or 5, characterised in that said means for adjusting the cross section of said aperture and/or of said passageway, consist of pivoting flaps (28).
7. A separator according to claim 4 or 5, characterised in that said means for adjusting the cross section of said aperture and/or of said passageway, consist of diaphragms.
8. A separator according to claim 4 or 5, characterised in that said rotor is fitted with means (32, 32', 40) to vary the cross section of at least some of the channels (15) formed between the blades (14) of one of the sectors or portions of the rotor.
9. A separator according to claim 2 or 8, characterised in that said means to vary the cross section of the channels consist of plates arranged in said channels (15), each plate being mobile from a first position where it leaves the whole cross section of the channel practically free, and a second position where it blanks off the channel practically completely.
10. A separator according to claim 2 or 8, characterised in that said means to vary the cross section of the channels consist, for each channel, of two plates (40) placed at the outlet of the channel (15) and mounted to pivot on a vertical axis (42) laid out on the medium plane of the channel, which plates may be brought by an appropriate mechanism (44) from a first position, where they are pressed against one another and arranged practically parallel to said medium plane, into a second position where their free ends abut against the end of the blades (14) delineating the channel.
11. A separator according to claim 2 or 8, characterised in that some blades (14) of the rotor are orientable around verticals axes so that they may rest on a neighbouring blade to blank off the channels (15) formed with the neighbouring blades, these orientable blades forming the means to vary the cross section of said channels.
12. A separator according to claim 2 or 8, characterised in that some blades (14) of the rotor consist of two sections, a fixed section (31, 31') and a mobile section (32, 32') orientable by rotation around a vertical axis and these mobiles sections of the blades form the means to vary the cross section of the channels (15).
13. A separator according to claim 12, characterised in that one of the faces (31) of some blades is fixed and the other face (32) is mobile and capable of pivoting around a vertical axis (33) situated close to the periphery of the rotor to rest on the neighbouring blade and blank off the channel (15) that they form.
14. A separator according to claim 12, characterised in that the radially external portion (31') of the blade is fixed and its radially internal portion (32') is rotary, whereas the mobile portions of two neighbouring blades may be brought to rest against one another to blank off the channel delineated by both blades.

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