EP0791407A2 - Sifter - Google Patents

Abstract

The material is fed into a separator (3) between an outer ring of air ducts (5,6,7,8) and an inner impeller rotating (13) about a vertical axis. The impeller has a tapering profile, narrower towards the bottom, and the space between the impeller and the vanes has a similar shape. The vanes direct the air flow tangentially into the separating space. The fine material is blown out of an upper duct (12) while the coarse material is dropped into a hopper (11) for recycling to the mill. The range of grain size of the milled material taken out of the mill is selected by altering the relative air flows into the air ducts. The upper air ducts have a larger air flow than the lower ducts. The upper air ducts have a larger duct cross section than the lower ducts.

Description

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

A classifier of the required type is known from DE-C-36 22 413 and is used as a high-performance classifier or high-performance wind classifier in grinding plants in order to remove the comminution product coming from a mill, for example cement materials or the like, into fines and coarse material to be removed as finished goods ( Grain) to separate, which is generally further crushed. This known sifter is primarily designed so that it has a high selectivity. A design is selected in which the vertical-axis classifier rotor is arranged centrally in the classifier housing and has an essentially cylindrical shape (around the rotor axis), this classifier rotor being concentrically surrounded by a likewise essentially cylindrical, stationary guide vane ring with a radial spacing such that Between the rotor blades of the classifying rotor and the guide vane ring, a visual space in the form of a ring cylinder is formed. Furthermore, the inlet spiral for supplying the viewing air is divided by partition walls into at least two, preferably three, superimposed supply channels, in each of which adjusting elements are provided. In this way it should be possible to adapt the quantity and / or speed of the visible air flowing into the individual feed channels of the entry spiral to the material load in the various height areas of the viewing area in the sense of the desired high selectivity.

If this known classifier in a grinding plant in a closed circuit with a corresponding mill, in particular a roller or roller mill such as e.g. a Gutbett roll mill works, then it can happen that the finished product, for example cement, has a relatively steep grain size distribution and thus a relatively narrow grain belt. In practice, however, it is often necessary to manufacture some fine goods to be removed as finished goods with a broader or flatter grain size distribution, as is required for some cements for various reasons.

Furthermore, a classifier is known from DE-A-29 47 310, the upper housing section of which is cylindrical and without a visible air inlet spiral. A classifying fan wheel with a vertical axis of rotation, which operates in the sense of a classifying rotor, is arranged centrally in this upper housing section and can have the shape of an inverted cone or another shape. A sort of guide vane ring is arranged around this fan wheel with a radial spacing, so that a visual space is again formed between the guide vane ring and the fan wheel. Classification with a high degree of efficiency is also sought here, and above all a complete separation of coarse and fine particles in the case of agglomerate formation or the like is sought. For this purpose, sifting air is fed into the interior of the classifier via several gas chambers, these gas chambers being arranged distributed over the height of the classifier housing, of which only the uppermost gas chamber surrounds the actual classroom between classifier rotor and guide vane ring, while the other gas chambers in the area below of this actual visual space lead into the interior of the classifier housing. In this way, above all the coarse material falling downward is subjected to multiple rechecking or pneumatic screening from the visible material that can be fed centrally from below or from the side or from above. Since in the ring-shaped sighting space surrounding the sifting rotor only through the uppermost gas chamber (or the uppermost gas inlet duct) sight air is supplied, but the amount and composition of the material to be sighted is generally very different over the height, the sight air becomes a burden Distribute the desired sharp separation effect over the height of the visible space unevenly and in an uncontrolled manner.

The invention is based on the object of developing a classifier of the type required in the preamble of claim 1 in such a way that, while maintaining a high separation efficiency between coarse and fine material, it allows the production of a finished product which has broad limits in its grain size distribution is adjustable and in particular also enables a sufficiently wide or flat grain size distribution.

This object is achieved by the characterizing part of claim 1.

Advantageous refinements and developments of the invention are the subject of the dependent claims.

In the classifier design according to the invention, the classifier rotor has a conical shape which tapers downwards with rotor blades running diagonally downwards and inwards.

Since, in this classifier construction according to the invention, the classifying air inlet spiral is divided into at least two superimposed supply channels in order to be able to supply the classifying air in a targeted and adapted manner at least in adjustable quantities to the different heights or height ranges of the classifying area, the possibility of supplying the classifying material is also retained here to classify very effectively. However, the classifying rotor which tapers conically downwards now generates a correspondingly greater circumferential speed in its upper region due to the larger diameter present there, which in turn leads to a correspondingly large turbulence in this height region of the visible space and to a small separating grain size. In contrast, correspondingly lower circumferential speeds with correspondingly lower turbulence are also generated in the lower height area of the classifying space due to the smaller diameter of the classifying rotor, which leads to a coarser size of the separation grain. Due to these different eddies across the height of the viewing area, different separating grain sizes can thus be achieved in the different height positions in this viewing area, so that - in comparison to the known classifier according to DE-C-36 22 413 explained at the outset - a high level in the individual height areas Separation efficiency between coarse and fine material is achieved, but at the same time the possibility is created to achieve or set a broad or flat grain size distribution corresponding to the respective requirements.

In this classifier design according to the invention, it is also advantageous to provide such a structural design of the individual feed channels of the entry spiral or corresponding means that the upper height regions of the classifying area, which are limited inward by upper rotor sections with a larger outside diameter, are supplied with larger quantities of classifying air than those lower viewing area areas (height areas of the viewing area) which are limited on the inside by lower rotor sections with a smaller outside diameter. In the upper height areas of the classifying chamber, the classifying rotor therefore has higher peripheral speeds, with - preferably adjustable - relatively high quantities of classifying air in order to achieve a relatively small separating grain size. On the other hand, in the lower height ranges with the lower peripheral speeds of the classifying rotor, smaller - preferably adjustable - quantities of sifting air can be supplied, a relatively clean sifting also being made possible in this coarser separation grain area. All in all, the quantity and speed of the sifting air via the supply channels and thus the formation of eddies over the entire height of the sifting space can be adjusted so that several separating grain sizes can be achieved over a relatively wide range without the classifier losing its separating efficiency.

The use of this classifier according to the invention is particularly noticeable when it is connected in the closed grinding circuit with a well-known good-bed roller mill in order to crush cement clinker and aggregates, the fine material to be removed from the classifier then containing a cement accordingly wider or flatter Grain size distribution forms. However, other materials can also be comminuted and sifted in a similar manner, it also being possible to use a different mill, for example a conventional roller or roller mill, for comminuting the material to be fed to the classifier.

Fig.1

einen vertikalen Querschnitt durch eine erste Ausführungsform des erfindungsgemäßen Sichters,

Fig.2

einen horizontalen Querschnitt durch den erfindungsgemäßen Sichter, etwa entsprechend der Schnittlinie II-II in Fig.1;

Fig.3

eine Detail-Schnittansicht entsprechend der Linie III-III in Fig.2, zur Erläuterung von Einstelleinrichtungen in Sichtluft-Zuführkanälen;

Fig.4

eine weitgehend schematische vertikale Schnittansicht durch ein zweites Ausführungsbeispiel des Sichters, wobei in der linken Hälfte und in der rechten Hälfte noch zwei verschiedene Ausführungsvarianten für die Gestaltung des stationären Leitschaufelkranzes veranschaulicht sind;

Fig.5

ein Diagramm mit zwei Korngrößenverteilungskurven als Vergleich zwischen einem bekannten Sichter und dem erfindungsgemäßen Sichter.

The invention is explained in more detail below with the aid of a few exemplary embodiments illustrated in the drawing. Show in this drawing

Fig. 1

3 shows a vertical cross section through a first embodiment of the classifier according to the invention,

Fig. 2

a horizontal cross section through the classifier according to the invention, approximately according to the section line II-II in Figure 1;

Fig. 3

a detailed sectional view along the line III-III in Figure 2, for explaining adjustment devices in sifting air supply channels;

Fig. 4

a largely schematic vertical sectional view through a second embodiment of the classifier, two different design variants for the design of the stationary guide vane ring being illustrated in the left half and in the right half;

Fig. 5

a diagram with two grain size distribution curves as a comparison between a known classifier and the classifier according to the invention.

The classifier according to the invention will first be explained with reference to a first embodiment, which can be seen primarily from FIG. 1, but also largely from FIG.

This classifier contains a vertical-axis classifier housing 1, which has an inlet spiral 2 in its upper region for the supply of classifying air. This entry spiral 2 opens tangentially into an annular visual space 3 formed within the classifier housing 1. Furthermore, this entry spiral 2 is divided by horizontal dividing walls 4 in this example (FIG. 1) into four superimposed viewing air supply channels 5, 6, 7, 8, which in the present case have essentially the same height dimensions.

As can be seen in FIGS. 2 and 3, two adjusting devices designed as adjustable flaps 9 for adjusting the amount of air supplied to the individual supply channels 5, 6, 7, 8 are installed in the entry area of the entry spiral. The actuation of the flaps 9 arranged in pairs can take place via corresponding outer adjusting levers 10, specifically the flaps 9 assigned to the individual feed channels 5, 6, 7, 8 can be adjusted independently of one another. A desired, adjustable amount of visible air can thus be supplied to the different height ranges of the visual space 3.

The classifier housing 1 also has at its lower end a coarse material discharge funnel 11 with a coarse material outlet opening 11a and at least one pipe connection 12 which is used to discharge the fine material Visual air is used and in this case (see Fig. 1) is connected to the upper cover wall 1a of the housing 1.

An approximately basket-shaped sifter rotor 13 is arranged centrally in the sifter housing 1 and can be rotated about a vertical axis 14 and is driven via a shaft 15 by a drive device (not illustrated in more detail) arranged on the sifter housing 1. This rotor 13 is equipped on its circumference with rotor blades 16, which are held on the rotor in a conventional manner and are preferably fixed, but if necessary, can also be attached to the classifying rotor 13 about their longitudinal axes 16a (FIG. 1) running from top to bottom.

In this case, however, it is important that the classifying rotor 13 has a conical shape that tapers from top to bottom (see FIG. 1) with rotor blades 16 that run obliquely downwards.

Otherwise, this rotor 13 can be constructed essentially in a conventional manner, its shaft 15 being expediently mounted at the lower end in a bearing 17 which is supported in an adjustable manner by radial struts 18.

In this embodiment according to FIG. 1, the classifying rotor 13 is closed at its lower end by a bottom wall 13a, while at its upper end it is only partially covered by an annular plate 13b, so that it has a sufficiently large central through opening 19 on this upper side for discharging the fine air laden with fine material into the pipe connection 12.

The classifying rotor 13 is also surrounded concentrically by a guide vane ring 20 installed in the classifier housing 1 at a radial distance in such a way that the annular classifying space 3 is formed between this vane ring 20 and the rotor blades 16. This guide vane ring 20 contains a plurality of guide vanes 21 which are arranged at equal distances from one another in the circumferential direction and which can preferably be adjusted together about their longitudinal axes 21a running from top to bottom relative to the viewing space 3 (by means known per se). This guide vane ring 20 or its guide vanes 21 are thus provided at the outlet end of the classifying air inlet spiral 2. As shown in FIG. 2, the guide vanes 21 are inclined in the sense of the direction of flow of the viewing air flowing approximately tangentially into the viewing space 3. This viewing space 3 also extends essentially over the same (vertical) height as the entry spiral 2, the guide vane ring 20 and the classifying rotor 13 or its rotor blades 16.

According to the embodiment illustrated in FIG. 1, the guide vane ring 20 also has a conical shape which tapers downwards, the guide vanes 21 accordingly running or converging obliquely from top to bottom inwards. The guide vane ring 20 tapers essentially at the same cone angle (with respect to the axis of rotation 14) as the classifying rotor 13. In this way, the viewing area 3 is also conical, with an essentially constant ring cross-section from top to bottom.

Finally, this classifier also contains suitable devices for feeding visual goods into the classroom 3. These feed devices can be designed in any suitable and known manner. Thus, in the present example (FIGS. 1 and 2), at least one of the sifting air supply channels 5, 6, 7, 8, but preferably at least one of the uppermost supply channels (for example 5, 6) can at the same time also be used for supplying the sifting material via the entry spiral 2 into the Visual space 3 can be formed. As an alternative or in addition, in the upper housing top wall 1a - as indicated by dash-dotted lines in FIG. 1 - at least one product feed connection 22 can also be arranged, which opens out via the upper ring plate 13b of the classifying rotor 13, which acts at the same time as a material distributor plate, in such a way that the visible material or a Corresponding portion of visible material can be entered from above into the annular view space 3 evenly distributed over the circumference via this upper ring plate 13b, this evenly distributed entry being supported or improved by a deflection ring indicated by dash-dotted lines at 1b (FIG. 1) above the view space 3 can be.

The function of this sifter explained so far should be largely clear on the basis of the details described above to explain the invention. The visible material, which is preferably distributed predominantly or entirely into the upper end of the viewing space 3, is exposed to different eddies during its movement through this viewing space 3 in the different height ranges, which result from the different peripheral speeds of the classifying rotor 13 at its different height sections and can still be controlled by adjustable visible air quantities of the superimposed feed channels 5, 6, 7, 8, larger quantities of visible air being expediently supplied to the upper height regions of the visible space 3 than the lower height regions of the visible space 3. In this way, there are several in the height regions of the visible space 3 Separation grain sizes with an overall relatively wide or flat grain size distribution and with a relatively high separation efficiency of the classifier.

A further exemplary embodiment of the classifier according to the invention is illustrated in FIG. 4, the guide vane ring in the left half of this FIG. 4 an embodiment variant with a conical guide vane ring (similar to that in FIG. 1) and a second embodiment variant in the right half of FIG shows with a substantially cylindrical vane ring with an otherwise identical overall design.

Since many parts of the sifter example illustrated in FIG. 4 are similar in basic function and also partially in basic structure, as have been explained with reference to FIGS. 1 to 3, in this example FIG. 4 largely uses the same reference numbers with the addition of a dash for used approximately the same components, so that the following explanation of this embodiment can be limited essentially only to the real differences.

Also in FIG. 4, the classifier contains a classifier housing 1 'with a classifying air inlet spiral 2' which opens tangentially into the annular classifying chamber 3 'and is divided by two partition walls 4' into three superposed feed channels. The formation of the entry spiral 2 'can otherwise be designed in the same way, as illustrated and explained with reference to FIG. 2; The same also applies to the provision of adjustable flaps 9 for setting the amount of visible air supplied to the individual feed channels 5 ', 6', 7 '.

The classifying rotor 13 'also has a conical shape which tapers from top to bottom with rotor blades 16' which run obliquely downwards and inwards. In the example of FIG. 4, the rotor 13 ', which can be rotated about a vertical axis 14' and driven by its shaft 15 ', is closed at its upper end by an upper cover plate 13'b, which at the same time acts as a good distributor plate and via which one of the visible goods Feeding-serving distributor bell 23 opens out concentrically, so that the fresh visible material is placed centrally on the cover plate 13'b of the rotor 13 'via this distributor bell 23 and is evenly distributed by the rotary movement of the rotor 13' and flung outward into the viewing space 3 'from above. can be entered.

On its lower end face 13'a, the sifting rotor 13 'has a sufficiently large, central through opening 19' through which the sifting air laden with fine material is guided centrally downward into a pipe connection 12 'arranged there, which in turn is connected via a plurality of pipes 24 to the outside the sifter housing 1 arranged fine material separator 25 is connected.

To discharge the coarse material, the classifier housing 1 'also has a coarse material discharge funnel 11' at its lower end in this case.

Furthermore, according to FIG. 4, the sifting rotor 13 'is again concentrically surrounded at a radial distance by a guide vane ring arranged in a stationary manner in the sifter housing 1'. According to the variant on the left in FIG. 4, the guide vane ring 20 '- in the same way as in the embodiment according to FIG. 1 - is also conical (tapering downwards), while the guide vane ring 20' 'in the right half of FIG. 4 essentially is cylindrical. Accordingly, the visible space 3 'formed in the left embodiment of FIG. 4 - as described with reference to FIG. 1 - has a ring cross section that remains the same from top to bottom. On the other hand, in the embodiment variant according to the right half of the drawing in FIG. 4, the visible space 3 ″ formed between the rotor blades 16 ′ and the guide vane ring 20 ″ has an annular cross-section which increases uniformly from top to bottom. Although both design variants can solve the problem on which this invention is based in an advantageous manner, the left design variant in FIG. 4 offers the further advantage that the separating grain sizes can be set and varied even more precisely in the different height ranges of the viewing space 3 '; in the right variant in FIG. 4, on the other hand, the cylindrical guide vane ring 20 ″ can be manufactured somewhat more simply.

A further difference of the exemplary embodiment illustrated in FIG. 4 can be seen in the fact that at least the upper feed channel 5 'of the classifying air inlet spiral 2' can have a larger clear cross section than the lower feed channels 6 ', 7'. Through this configuration of the individual classifying air supply channels 5 ', 6 ', 7' there is a further possibility of supplying larger amounts of visible air to the upper height areas of the viewing space 3 'than to the lower height areas. Nevertheless, it is considered expedient that all feed channels 5 ', 6', 7 'are again each equipped with individually adjustable adjustment flaps 9 for adjustable air quantities in the same manner as described above with reference to FIGS. 2 and 3.

To support the idea of the invention for the newly proposed classifier, a number of test series were carried out, in which the same comminution products in a cement grinding plant, which contained a material bed roller mill as a comminution unit, on the one hand in a conventional high-performance classifier according to DE-C-36 22 413 (with cylindrical classifier rotor and Visible space) and on the other hand in a classifier design according to the present invention. Samples were taken from the extracted fine goods products, i.e. the finished cements of the two classifiers to be compared, and examined in conventional sieve analyzes. The results of two typical sieve analyzes are shown in the diagram illustrated in FIG. 5 (a known, so-called RRS diagram) using two curves. Here curve I (solid line) represents the grain size distribution of the fine material from the conventional classifier (according to DE-C-36 22 413) and curve II (dash-dotted line) represents a typical grain size distribution in the fine material of the classifier constructed according to the invention.

The diagram according to FIG. 5 shows the individual sieve residues R determined in the sieve analyzes of the samples in% in the Oridnate, while the abscissa gives the grain size K in µm. The two curves I and II plotted in the diagram of the two selected samples make it clear that the fines or finished goods sample taken from the conventional classifier had a steeper grain size distribution and thus a narrower grain size band than the finished goods sample taken from the classifier constructed according to the invention, which - according to curve II - A wider or flatter grain size distribution and thus a wider grain band in the finished product (cement) can be demonstrated.

Claims (12)

Sifter containing a) a classifier housing (1, 1 ') with a tangential opening into an annular classroom (3, 3'), through partitions (4, 4 ') in at least two superimposed feed channels (5 to 8, 5', 6 ', 7 ') divided inlet spiral (2, 2') for the adjustable supply of classifying air into the classroom at different heights as well as with a coarse material discharge funnel (11, 11 ') and at least one connection (12, 12') for removing the classifying air loaded with fine material , b) a centrally in the classifier housing (1, 1 '), rotatable about a vertical axis (14, 14'), approximately basket-shaped classifier rotor (13, 13 '), which has rotor blades (16, 16') on its circumference and is concentrically surrounded by a stationary vane ring (20, 20 ') installed in the classifier housing at a radial distance, c) devices for feeding visual material into the visible space (3, 3 ') formed between the guide vane ring and rotor blades, this visible space extending essentially over the same height as the entry spiral, the guide vane ring and the rotor blades,
characterized, d) that the classifying rotor (13, 13 ') has a downwardly tapering conical shape with rotor blades (16, 16') running obliquely downwards and inwards. Sifter according to claim 1, characterized by such a configuration of the individual feed channels (5 to 8, 5 'to 7') of the entry spiral (2, 2 ') that the upper height areas of the viewing space (3, 3'), which inwards from upper rotor sections with a larger outer diameter are limited, larger amounts of visible air are supplied than the lower height ranges, which are limited inward by lower rotor sections with a smaller outer diameter. Sifter according to Claim 2, characterized in that all the feed channels (5 to 8, 5 'to 7') of the entry spiral (2, 2 ') with devices (9) for adjusting the amount of sifting air for the supply into the different height areas of the sifting space (3 , 3 ') are equipped. Sifter according to claim 2, characterized in that at least the upper feed channel (5 ') of the entry spiral (2') has a larger clear cross-section than the lower feed channels (6 ', 7'), preferably all feed channels with devices (9) for Setting the quantities of visible air for the supply to the different height areas of the visible space (3 '). Sifter according to claim 2, characterized in that the entry spiral (2, 2 ') is arranged in three or more one above the other Classification air supply channels (5 to 8, 5 'to 7') is divided. A classifier according to claim 1, characterized in that the classifying material feed devices have at least one product supply nozzle (22, 23) attached to the top wall of the housing (22, 23), which via an upper cover plate (13b, 13'b) of the classifying rotor (13 , 13 ') opens out in such a way that the visible material can be introduced from above into the ring-shaped viewing space (3, 3') evenly distributed over the circumference. A classifier according to claim 1, characterized in that at least one of the classifying air supply channels (5 to 8), preferably at least the uppermost supply channel, is simultaneously designed for supplying classifying material via the entry spiral (2) into the classifying room (3). Classifier according to claim 1, characterized in that the guide vane ring (20 '') surrounding the classifier rotor (13 ') is essentially cylindrical. Classifier according to claim 1, characterized in that the guide vane ring (20, 20 ') surrounding the classifier rotor (13, 13') also has a conical shape which tapers downwards. Classifier according to claim 9, characterized in that the guide vane ring (20, 20 ') with the formation of a conical viewing space (3, 3') with an essentially constant ring cross-section from top to bottom tapers down substantially at the same cone angle as the classifying rotor (13, 13 '). Sifter according to claim 1, characterized in that the guide vanes (21) of the guide vane ring (20, 20 ', 20' ') are adjustable about their longitudinal axes (21a) running from top to bottom. A classifier according to claim 1, characterized in that the rotor blades (16, 16 ') are optionally attached to the classifying rotor (13, 13') in a fixed manner or adjustable about their longitudinal axes (16a) running from top to bottom.

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