EP0199003A2 - Rotary air classifier with a centrifugal cage - Google Patents

Abstract

The invention relates to a rotary air centrifuge classifier. Up to now, the problem with such classifiers, particularly in the case of a visible exhaust air duct leading upwards, was the advantageous predispersion of the material to be classed. The invention in this case goes the way of distributing the material to be sifted over several stages supported by dispersing vanes and to enable a higher extraction capacity of the visual exhaust air by branching the extraction line.

Description

The invention relates to a rotary air centrifuge classifier according to the preamble of claim 1.

Such a classifier is known from EP 67 894 A1. Such separators generally require dust separators, e.g. in the form of cyclones. For this purpose, it may be expedient to draw the classifying air out of the classifier as far as possible so that there is sufficient space for installing the downstream cyclones and the circulating air blower generating the classifying air. This is particularly important where the classifier is connected downstream of a mill and the classifier should be placed as close as possible above the mill in view of low investments.

However, this extraction of the visual exhaust air coaxially to the axis of rotation of the classifier and as centrally as possible on the centrifugal basket brings with it considerable problems with regard to optimal predispersion of the material to be viewed. However, particularly good predispersion is the prerequisite for excellent selectivity during the viewing process. In other words, with an optimally operating classifier, it is expected that as little oversize as possible will get into the fine material and at the same time as little undersize as possible into the coarse material if a separation grain limit is sought. The view qut must therefore enter the view space as evenly as possible, with of course also an in falling of the visible material into the visible space, in certain cases also falling into the visible air swirl, must be prevented.

However, this required predispersion is not guaranteed in the classifier known from EP 67 894 A 1, since there is an annular channel provided directly above the classifying space for supplying the classifying material or raw material around the suction line which leads upwards, so that it can be assumed that in principle, the material to be viewed simply falls into the viewing area and an entry of material to be viewed against the air swirl cannot be ruled out.

In another classifier known from EP 23 320 B1, an attempt is being made to achieve a scattering effect for the classifiable material introduced, even with a coaxial upward suction line for the classifying air laden with fine material. Since only the outer, flange-shaped edge of the upper end of the centrifugal basket can be used as a mechanical scattering device in this known classifier, however, a good dispersing effect is not achieved. In addition, in this known classifier, the material to be sighted falls almost point-wise through two or more inlets arranged around the central suction line onto the flange-shaped edge rotating at a relatively high peripheral speed. The individual particles of the material to be sighted are immediately radially accelerated from each of the corresponding points of contact, with only a triangular diffusion curtain, which is from neighboring ones, being formed in the event of a slight drag beard scatter veils can be interrupted, can form. In this known classifier there is also the disadvantage that the shape and spacing of the scatter curtains change with changing speeds of the centrifugal basket with regard to changed separating grain boundaries, so that a uniform distribution of the material to be viewed cannot be achieved. The lack of a central visible material feed, combined with the uneven distribution effect of the flange-shaped edge, therefore has a particularly unfavorable effect on the dispersion process which is to be aimed for optimally.

Since a good predispersion plays a major role in determining the throughput for the material to be sifted, this being particularly important in the case of previous grinding in a closed grinding material cycle, since fluctuations in quantity can have an abrupt impact on the classifying process To get predispersion.

For example, a PSZ spiral wind sifter is known (cement-lime gypsum, year 38, no. 1/85, "New findings on sifter design", by F. Sgaslik, Fig. 7), in which a predispersion of the visible material is sought. The material to be sighted is fed in centrally in this PSZ classifier and is scattered from an inclined, rotating spreader plate into a non-rotating, conical distributor gap that widens downwards. The uniformity of the _S ichtgutverteilung diameter increases. The ER- _f on formulas has shown, however, that the inclination angle of this distribution gap, which surrounds the sifting chamber, depending on the friction coefficients of the trickling view good. In the case of an optimal distribution of the visible material by trickling, the granular visible material must not fall, but must just slide, ie it must still be free-flowing. The trickle section must also be long enough to achieve the desired predispersion. In order to obtain a wide range for different free-flowing visible material with this known PSZ classifier, one goes there the elaborate way to blow purge air into the conical distributor gap. In addition, this PSZ classifier has the problem that a large horizontal component has to be accepted for a sufficiently long trickling distance, the flow-correct distance from the centrifugal basket to the swirl-producing guide vanes being exceeded, and thus the annular visual space being enlarged. The resulting slight curvature of the required air spiral in the viewing space necessarily forces the user to work with higher air speeds while maintaining the same visual effect. However, this means that for larger amounts of air, correspondingly larger separating devices, such as cyclone separators or filters, are required, which considerably increase the investment in equipment.

Starting from the above prior art, the invention has for its object to improve a rotary air centrifuge classifier with a view to a more optimal classifying, the essential disadvantages mentioned above should be avoided and good predispersion even with increased throughput of the classifiable material to be viewed is achieved, and this should also be possible, if appropriate, with a suction line that is led off centrally for the fine exhaust air that is loaded with fine material.

This object is achieved in a generic classifier by the features of the characterizing part of claim 1.

An essential idea of the invention to improve the classification and the throughput assets at favorable overall height of the classifier is to make a substantially _'central task of the separated material to a first spreading plate, wherein this plate is a further scattering at least downstream. In addition to this spreading disc, dispersing vanes are provided especially in the area before the visible material enters the visible space, which further improve the uniformity of the spreading of the material to be sifted into the subsequent visible space. Here, the areas of the individual funnel jackets are enlarged in the direction of the visible space in comparison to the previous step in order to achieve a thinning and equalization of the Slreuse veil. Because especially with an upward suction line for the visual exhaust air and the fine material flow and distribution discontinuities in the Dispersion process of the introduced material to be sighted can occur, the suction line is preferably branched below the first spreading plate into several, and especially two, flow-symmetrically arranged sight air outlets. The multiple levels of spreading plates and funnel jackets compensate for any discontinuities that may occur. However, a higher suction capacity and also the connection of several cyclones is made possible by the multiple visual exhaust outlets. The concept according to the invention therefore permits an overall space-saving design of the classifier with regard to its overall height and its diameter, even with a high feed performance and high suction performance, this being achieved with largely optimal dispersion of the grain mixture to be viewed. In order to be able to control the parameters of the classifier, which influence the dispersion and classification, the spreading plates, the dispersing vanes and the centrifugal basket are preferably designed to be separately drivable. As a result, both the same and a different rotation of these devices can be achieved. The direction of rotation of these devices is such that the visible material flows into the visible air spirals circulating in the visible space in the same direction.

Even an upward discharge line is not an obstacle in the invention to provide a further, especially circular, spreading disc in this area. At this stage, the second spreading plate is combined with a tubular upwardly projecting peripheral wall coaxially surrounding the fixed suction line, this peripheral wall projecting axially upward into the mouth funnel of the first funnel jacket. With a sufficiently small distance between this peripheral wall and the suction line, an existing thin annular gap remains without impairing the suction power of the connected cyclones. However, this small annular gap can also be kept fluid-tight by a seal that enables the rotation of the spreader plate with its peripheral wall.

In order to create a classifier that is even more compact in terms of height, one can advantageously arrange the suction line from the centrifugal basket downwards where the external units allow it. As a result, the first stage of the funnel jacket can be designed to be significantly reduced axially without the dispersion of the visible material to be distributed being impaired. In the case of a suction line provided on one side, the various suction effects in the centrifugal basket which are present in some cases in the prior art can largely be eliminated by providing guide vanes which are subdivided in the axial direction and are also angle-adjustable relative to one another. This makes it possible to give the spiral-shaped visual air on the suction side a different inflow path and swirl configuration than in the area of an opposite, generally largely closed plate of the centrifugal basket.

If the single-stage sifting is to be improved despite predispersion, a further visual air inlet with appropriate guide vanes can expediently be provided in the area of the outlet for the coarse material adjacent to the lower area of the centrifugal basket. In order that the outdoor units can be kept as simple as possible, this second visual air inlet can be designed in the manner of a bypass or a branch from the main visual air inlet.

With a funnel-shaped design of the spreading plate with the opening surface facing upwards, an improvement in the spreading of the visible material falling thereon is achieved, since the inclination of the spreading plate and the weight of the individual particles achieve a uniform movement of the grain sizes to the edge of the spreading plate.

Since the invention allows both an upward and a downward suction line to be designed, a coaxial suction line can advantageously be provided on both sides of the centrifuge basket to improve the flow conditions within the centrifugal basket. This has the advantage that the additional, fixed or non-rotatable sieve shells normally required inside the rotating centrifugal basket can be dispensed with. As a result, the flow vanes of the centrifugal basket, which are designed as strips or blades, can be stiffened radially to save weight and material. This he possible a reduced momentum due to the reduced mass, whereby the replaceable wear protection is also easier to handle.

• Figur 1 ein erstes Ausführungsbeispiel eines Drehluft-Schleuderkorb-Sichters im wesentlichen im Axialschnitt, bei dem die Sichtabluft zentral aus dem Schleuderkorb nach oben abgesaugt wird;
• Figur 2 einen schematischen Radialschnitt durch den Sichter nach Fig.1,in dem einerseits die Konfiguration der Sichtabluftstutzen und andererseits das Spiralgehäuse des Sichters auf der Ebene der Sichtlufteintritte dargestellt ist;
• Figur 3 ein zweites Ausführungsbeispiel eines Drehluft-Schleuderkorb-Sichters im wesentlichen im Axialschnitt, bei dem die Sichtabluft zentral aus dem Schleuderkorb nach unten abgesaugt wird, und
• Figur 4 zwei Radialschnitte durch den Sichter nach Fig.3 in verschiedenen Ebenen, wobei links ein Schnitt im Bereich der Leitschaufeln in Draufsicht nach unten und im rechten Teil eine Draufsicht auf die den Schleuderkorb nach oben abschließende geschlossene Platte dargestellt ist.

The invention will be explained in more detail below with the aid of schematic drawings of two exemplary embodiments; show it:

• Figure 1 shows a first embodiment of a rotary air centrifuge classifier essentially in axial section, in which the exhaust air is extracted centrally from the centrifugal basket upwards;
• FIG. 2 shows a schematic radial section through the classifier according to FIG. 1, in which, on the one hand, the configuration of the classifying exhaust air sockets and, on the other hand, the spiral housing of the classifier is shown on the level of the classifying air inlets;
• Figure 3 shows a second embodiment of a rotary air centrifuge classifier essentially in axial section, in which the visible exhaust air is sucked down centrally from the centrifugal basket, and
• 4 shows two radial sections through the classifier according to FIG. 3 in different planes, one on the left Section in the area of the guide vanes in a plan view downward and in the right part a plan view of the closed plate closing the centrifugal basket upward is shown.

Since generic rotary air centrifuge classifiers and their mode of operation are well known, the main differences of the invention with respect to these known classifiers will be referred to below.

1 and 2 relate to a classifier 20, in which the classifying air is extracted upwards. In the example, the vertically operated classifier 20 has a central shaft 8 for driving an upper, first spreading plate 2 and a second spreading plate 5 arranged below it, with dispersing vanes IO associated therewith and a centrifugal basket 6.

The visible material reaches the sifter 20 almost centrally through the inlet connection 1. In the example, a single inlet connection 1 is provided which, in an inclined position, feeds the visible material into the inner cone against the funnel opening of the spreading plate 2. From the first rotating spreading plate 2, the introduced visible material is thrown against a funnel casing 3 surrounding the spreading plate 2 at a radial distance. In special training This funnel jacket 3 consists of two conically tapered jacket regions which are connected to a substantially vertical circumferential wall, through which on each side of the classifier 20 a view exhaust pipe 4 is guided to the outside.

This vertical casing area of the first funnel casing 3 helps to achieve a largely uniform distribution of the introduced material to be seen despite the implementation of the sight air outlet 4. If higher extraction capacities are considered to be desirable for the viewing process, instead of the two shown in the example, approximately diametrically opposite, outgoing air connecting pieces leading to the outside, several, e.g. three or four such nozzles with the same angular distance from one another can also be provided.

From the upper stage of the funnel jacket 3, the granular visible material slides downward in a spiral drag into a tapering opening which forms a mouth surface 35. Strands of the sliding veil of the material to be sifted, which can form in the case of very small quantities of the imported material to be sifted as a result of the penetration of the air outlet nozzle, are largely compensated for and the material to be sifted is largely uniform, somewhat collected.

From the tapering opening 36 of the funnel casing 3, the grain mixture to be sifted slides into the second rotating spreader plate 5, which is essentially circular in shape, with a collar-like, tubular circumferential wall 34 at its radially inner end upwards over the mouth surface 35 of the first funnel casing 3 protrudes. This circumferential wall 34 surrounds a central open-air exhaust pipe 7 which is open at the bottom and which is branched upward in the region of the vertical peripheral wall of the funnel jacket 3 into the two view-air connecting pieces 4.

The spreading plate 5, which forms a partial funnel opening upwards, is adjoined at the bottom by approximately radially standing dispersing vanes 10 which e.g. are rotationally rigidly connected to the second spreading plate 5 and the centrifugal basket 6 arranged underneath.

The second spreading plate 5 is surrounded radially on the outside by a second funnel casing 9, which has a larger diameter than the first funnel casing 3. The second spreading plate 5 throws the material to be sifted against the second funnel casing 9, on the circumference of which there is a complete circular distribution of the visible material . The dispersing vanes 10 are provided for generating air vortices in order to allow the already largely uniformly distributed visible material to flow optimally predispersed into the viewing space 11 provided below.

Instead of the torsionally rigid link between the spreading discs 2 and 5 and the dispersing vanes 10 and the centrifugal basket 6, separate rotary drives, e.g. over hollow shafts, can be provided for these individual assemblies.

The largely cylindrical centrifugal basket 6 has a relatively thin, closed plate 6 "at the bottom. Radially outside, the centrifugal basket 6 has a ring of flow vanes 6 'which are arranged essentially axially parallel and which can be designed, for example, as strips, blades or the like. At its upper end, the centrifugal basket 6 is kept open over most of its diameter, for example 2/3 of its diameter and more, in order to form a large suction opening in the direction of the central suction line 7. For reasons of stability, this open part of the centrifugal basket is therefore 6 are equipped with a small number of radial spokes 6 '' 'which are firmly welded to the shaft 8 and below the dispersing vanes, for example. These spokes 6' '' can have a streamlined shape in cross-section, taking into account their direction of rotation, so that they enter the centrifugal basket 6 acting suction flow remains largely unaffected.

Radially outward closes at least over the entire axial height of the centrifugal basket 6 and if necessary. even downward, the viewing space 11, the radially outward is limited by guide vane rings 12 and 13.

In the example, the guide vanes are axially divided and divided into two individual, separately adjustable guide vane rings 12 and 13. For the sake of simplicity, only two subdivisions are shown in the example. These independently adjustable guide vane rings 12 and 13 can be used to set the type of air movement circulating in the viewing space 11, with the suction acting on the fine material depending on the axial height in the viewing space and at least partially reaching into the centrifugal basket, particularly in the case of a suction line provided on one side can be.

As can be seen more clearly from FIG. 2, the sight air blown in through the sight air inlets 14 flows through the spiral housing 15 approximately on a narrowing spiral path. The blown-in air is introduced into the viewing space 11 via the inclined vane guide rings 12 and 13 with a corresponding flow and swirl direction. The visible material introduced through the entry gap 33 at the lower opening of the second funnel jacket 9 and dispersed into the viewing space 11 is viewed here in accordance with the grain size limit set. This grain size limit depends on a large number of parameters, such as the rotational speed of the centrifugal basket 6, throughput, degree of predispersion, setting of the guide vane limit, blowing speed and extraction speed of the sifting air, etc. With Fines laden sifting air flows through on its way forward radially inward flow wing 6 'of the _S chleuderkorbes 6 and is sucked to the two views air vent 4 subsequently distributed by the suction rohrförmiqe. 7 The following separators and cyclones for separating the fine material from the visual exhaust air are not shown.

At the bottom of the classifier 20 according to FIG. 1, there is essentially the coarse material hopper 16, via which the material lying above the grain size limit is discharged. In order to be able to carry out an after-treatment, a further spiral housing 17 with a likewise adjustable guide vane ring 18 adjoins after a short funnel-shaped transition region. In this area, there is therefore an inspection of the material falling down. The secondary sight air inlet 14 'in the spiral housing 17 is therefore expediently connected to the primary sight air inlet 14, so that a controllable proportion of sight air can be blown in there for indulgence.

The flow vanes 6 'of the centrifugal basket 6 can have different profiles depending on the intended use and also differ in their radial extent. It is important to coordinate these assemblies, according to which the suction effect is largely evenly adjusted over the axial height of the centrifugal basket, even with a suction line on one side.

In the sectional view of FIG. 2 can be seen as _ß a narrowing is produced in a range of 180 ⁰ to the entry of the separating air through the spiral housing 15 of a radially enlarged view of the air guide in the area of classifying air occurrence. In accordance with the flow direction generated in the classifier, the transition areas from the exhaust air line 7 to the visual exhaust air connection 4 are also designed. In the example, the fluidic extraction of the visual air loaded with fine material takes place in a displacement of the visual air nozzle of 90 to 180 ° with respect to the confluence of the visual air inlets 14.

3 and 4 schematize a sifter 30, the central exhaust air pipe 27 of which is provided below the centrifugal basket 56. In the case of functionally matching assemblies, the same reference numerals have been chosen as in the first exemplary embodiment according to FIGS. 1 and 2, the mode of operation of the classifier 30 also being essentially the same, apart from the direction of withdrawal.

The centrifuge basket 56 of the classifier 30 is constructed axially reversed, so that the closed plate 6 ″ lies at the top, while the spokes 6 ″ ″ are arranged at the bottom to stiffen the centrifugal basket 56.

The serious advantage of the sifter 30 is that a central task of the material to be sifted is provided, the axial extent of the entire sifter being omitted

upper exhaust air duct and corresponding nozzle could be significantly reduced. In particular, in the sifter 30, the first distribution of the material to be sifted can be carried out via a conical funnel jacket 3 with a single step. For this reason, the spreading discs 2 and 5 can be attached to the shaft almost at certain points.

A downward, tubular exhaust air line 27 connects centrally to the centrifugal basket 6, which is open at the bottom. This is slightly tapered in the after-inspection area, in order to subsequently open it in the area of the coarse material hopper 16 in two outgoing air outlet pipes which are guided outwards at an angle to the axis of the sifter 30. The extraction of view exhaust down also brings the advantage that any stringy training of Sichtgut- _G leitschleiers be excluded from the outset.

An exemplary profile of the flow vanes 6 'can be seen in the left half of FIG. 4. In this example, the flow vanes 6 'are designed approximately as isosceles rectangular angles, the tips of which point radially outwards. A symmetrical arrangement to the radius is sought. A change in the angle in the axial height is also expedient in order to ensure as uniform a suction as possible over the axial height of the centrifugal basket 56 in the case of one-sided visual exhaust air suction.

In the right half of FIG. 6, the closed plate 6 ″ can be seen radially on the inside, to which the entry gap 33 or the annular-cylindrical visible space 11 adjoins it.

Claims (12)

1. Rotary air centrifuge classifier with a centrifugal basket which can be driven about a vertical axis of rotation, which has flow vanes provided radially on the outside and through which the visible air essentially flows from the outside inwards,
with a circular visual space surrounding the centrifugal basket, to which a coaxial ring of guide vanes adjoins the outside radially, the visual air past the guide vanes being able to be introduced spirally into the visual space with a swirl, with an inlet above the visual space for the visual material and an outlet below the viewing area for the coarse grain and with at least one essentially coaxial suction line provided on the axial side of the centrifugal basket for the visual exhaust air loaded with fine material,
characterized,
that the inlet (1) of the material to be classified is assigned a first spreader plate (2) which can be rotated about the vertical axis of rotation and which supplies the material to be sighted to an at least one-stage, first funnel jacket (3) surrounding this spreader plate (2) with a radial spacing, that subsequently at least the mouth of the first funnel jacket (3) a further, second, to the vertical axis of rotation spreading plate (5) Feeding the material to be classified is assigned to a second funnel casing (9) which is larger in diameter than the first funnel casing (3), and that in the area of the entry ring gap (33) into the annular viewing space (11) adjoining the mouth of the second funnel casing (9) Dispersion vanes (10) which can be rotated about the vertical axis of rotation are provided for the visible material. 2. classifier according to claim 1,
characterized,
that the suction line (7, 27) in the classifier housing (40) merges into a plurality of flow exhaust outlets (4, 24) arranged symmetrically in terms of flow. 3. classifier according to claim 1 or 2,
characterized,
that the suction line (7) starting from the centrifugal basket (6) is arranged upwards so that the several visible exhaust outlets (4) below the first spreading plate (2), in particular with the same circumferential distance and / or essentially perpendicular to the axis of rotation, from the classifier housing ( 40) are performed. 4. Sifter according to one of claims 1 to 3,
characterized,
that the second spreading plate (5) is approximately circular in shape and has a circumferential wall (34) which coaxially surrounds the suction line (7) and which projects in particular axially into the bottom mouth surface (35) of the first funnel jacket (3). 5. classifier according to one of claims 1 to 4,
characterized ,
that the suction line (27) starting from the centrifugal basket (56) is arranged downwards. 6. Sifter according to one of claims 1 to 5,
characterized,
that the centrifugal basket (6; 56) opposite the individual suction line (7; 27) has a substantially closed plate (6 ''). 7. classifier according to one of claims 1 to 6,
characterized ,
that at least the second spreader plate (5) and / or the dispersing vanes (10) are rotatably connected to the centrifugal basket (6). 8. classifier according to one of claims 1 to 6,
characterized ,
that the spreading discs (2,5), the dispersing vanes (10) and the centrifugal basket (6; 56) can be driven relative to one another at the same or different speed. 9. Sifter according to one of claims 1 to 8,
characterized,
that the guide vanes (12, 13) are divided in the axial direction and / or, in particular relative to one another, are adjustable in angle. 10. Sifter according to one of claims 1 to 9,
characterized,
that in the area of the outlet (16) for the coarse material a second, in particular branched from the first sight air inlet (14), sight air inlet (14 ') is provided for inspection. 11. Sifter according to one of claims 1 to 10,
characterized ,
that the spreading plates (2,5) are essentially conical, with an upwardly open conical surface. 12. Sifter according to one of claims 1 to 11,
characterized,
that a coaxial suction line is provided axially on both sides of the centrifugal basket for the exhaust air loaded with fine material.

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