EP0460490A2 - Air classifier - Google Patents

Abstract

To classify granular material in at least three fractions, rod basket classifiers with at least two classifier wheels have been used so far, which are arranged in a housing at a distance above one another. The sifter wheels arranged one above the other were provided with their own lines for the sifting air supply and the sifting air discharge, in order to prevent fine material from getting into the medium or medium size material into the coarse material, so that a high separation of the desired grain fractions from each other is achieved . In contrast, with high output and sharp separation of the desired grain fractions from one another, a simplification of the classifier in terms of construction and operation according to the invention is achieved in that the classifying wheels (2, 3, 4) are nested concentrically in the housing (1) and at a distance are arranged from each other, so that they are successively flowed through by the classifying air, and that each classifier wheel is assigned its own good discharge.

Description

The invention relates to a classifier, in particular rod basket classifier with at least two classifier wheels for classifying granular material in at least three fractions, consisting of a substantially vertically arranged housing with classifier air supply and classifier material supply as well as classifier air discharge and discharge for the fine and coarse material.

In the German patent application P 39 24 826.7, a classifier of the above type is described and shown in drawing figures, in which the classifier wheels are arranged one above the other at a distance. Furthermore, a separate line for the supply of sight air and a separate line for the removal of sight air are provided for each classifier wheel. This design of the classifier is intended to avoid that when sifting granular material, no fine material gets into the medium product and no medium product gets into the coarse material, so that a high separation of the desired grain fractions from each other is achieved.

The object of the invention is a further improvement of the above-mentioned classifier, particularly with regard to the structural design and the mode of operation.

This object is achieved according to the invention with the measures of the characterizing part of claim 1. Characterized in that the classifier wheels according to the invention are nested concentrically in the housing and spaced from each other so that they are successively flowed through by the classifying air, with the same output and sharp separation of the desired grain fractions, as in the classifier mentioned above, a considerable Reduction of the classifier in its height achieved. Furthermore, this design of the classifier according to the invention simplifies the operation of the classifier considerably and saves energy.

According to a further advantageous embodiment of the invention, the classifying wheels are mounted separately in the housing and can be driven independently of one another. This enables the classifier wheels to be driven at different speeds and / or with mutually opposite directions of rotation and thus an optimal setting of the classifier on the item to be viewed.

In a further advantageous embodiment of the invention, a crop distributor plate is arranged on the outer classifier wheel and is loaded with the feed material from above. With the aid of the material distributor plate, not only is a distribution and loading of the viewing air stream particularly uniform over the scope achieved, but also a loosening and deagglomeration of the feeding material takes place, which has a particularly favorable effect on the visual effect.

According to a further advantageous embodiment of the invention, at least one further line of sight air is connected below the classifying wheels on the housing and opens from below into the free space between the classifying wheels. In this way, the grain fraction emerging from the main sight air flow downwards can be subjected to an after-inspection by supplying secondary sight air from below through the sight air line arranged below the classifying wheels on the housing, and the selectivity can thereby be improved.

Further details, features and advantages of the invention result from the following explanation of exemplary embodiments shown schematically in the drawings.

Fig. 1:

einen Stabkorbsichter ohne Gutverteilerteller gemäß der Erfindung im Längsschnitt.

Fig. 2:

einen Stabkorbsichter mit Gutverteilerteller gemäß der Erfindung im Längsschnitt und teils in Perspektive.

It shows:

Fig. 1:

a rod basket sifter without Gutverteilerteller according to the invention in longitudinal section.

Fig. 2:

a rod basket classifier with Gutverteilerteller according to the invention in longitudinal section and partly in perspective.

As shown in FIG. 1, the sifter for sifting granular material consists of a substantially vertically standing housing (1) with nested wheels concentrically nested therein and rotatable at a distance from one another (2, 3, and 4). The inner classifier wheel (2) is firmly connected to a central drive shaft (5) and the outer classifier wheels (3 and 4) are rotatably supported thereon, as well as with each other, by means of support bearings (6 and 7). Furthermore, the classifying wheels (3 and 4) are connected to hollow shafts (8 and 9) which in turn are held so as to be rotatable relative to the central shaft (5) and with one another in bearings (10 and 11). This arrangement and mounting of the classifying wheels (2, 3 and 4) according to the invention very advantageously enables the classifying wheels (2, 3 and 4) to be driven independently of one another.

The classifying wheels (2, 3, and 4) are very advantageously equipped with rod baskets (12, 13 and 14), the openings of which decrease between the rods (not shown in the drawing) for the passage of the visible air from the outer rod basket to the inner neighboring rod basket are trained. Compensation for the passage area for the classifying air, which decreases from the outside inwards with the same length of the classifying wheels, can be created by the length of the classifying wheels increasing from the outside in, so that the rate of passage of the classifying air for all classifying wheels either remains approximately the same or even decreases. For the same purpose, the thickness of the basket bars can be varied from inside to outside. On the side of the housing (1), at the level of the outer classifier wheel (4), a line (15) opening into the classifier housing (1) is arranged for the supply of classifying air, with air-guiding elements that can be adjusted and are known per se, not shown, while a line (16) is provided below the innermost classifier wheel (2) for the removal of classifying air from the classifier. Furthermore, there are openings (17) at the top of the classifier housing for supplying the material to be sifted and in the lower area immediately below the classifier wheels (2, 3 and 4), channels (18, 19 and 20) which run obliquely downwards for the discharge of those in the classifier separated grain fractions arranged. The inner clear width of the channels (18 and 19) is here exactly on the distance between the rod baskets (12, 13 and 14) located or free annular space, so that any Mixing between the grain fractions already separated from the classifying air stream and separated from one another is avoided with certainty.

In operation of this classifier shown in FIG. 1 according to the invention, the classifying wheels (2, 3 and 4) are rotated by means of a drive device, not shown in the drawing, which is connected to the shafts (5, 8 and 9) . Sighting air is then fed to the sifter through line (15) and the material to be sifted is fed to the sifter in the direction of arrow (21) from above through openings (17). In the sifter, the sighted material is captured by the sifting air flow and taken along by it in the direction of the arrow (22), due to the increasing inward circulation speed of the rod baskets (14, 13) and the rod basket (12) for separating the feed material into three fractions, namely in Coarse goods (arrow 23), medium goods (arrow 24) and fines (arrow 25) that fall down into the channels (20, 19 and 18) and are discharged separately from the classifier. The from the sifting air transported into the interior of the rod basket (12) and discharged from there via the line (16) to the outside represents the fourth fraction, the finest fraction, which in a suitable separate device, e.g. B. filter or cyclone, separated from the classifying air and can be obtained in this way.

Furthermore, a further classifying air line (26) is connected to the housing (1) of the classifier, specifically below the line (15), with valves Guide branch lines (27, 28, 29) into the channels (18, 19, 20). Through these branch lines (27, 28, 29) more or less additional secondary air can be introduced into the channels (18, 19, 20) with the help of the valves, as required, which then counteracts the fractions (23, 24, 25) flows upwards into the free space between the classifying wheels (2, 3, 4), from where it reaches the interior of the rod basket (12) together with the classifying air flow (22) and from there via the line (16) is discharged to the outside. The fraction (23, 24, 25) which is separated out in the classifier and falls down is very advantageously subjected to an after-inspection by the secondary sifting air flowing from the bottom up, any missing grain which is found in the down-falling fraction (23, 24, 25), recorded with certainty and separated from the group. The separator's sharpness can be significantly improved in this way.

As shown in FIG. 2, a crop distributor plate (30) is arranged on the outer classifier wheel (4) at the top and is loaded with the feed material to be sifted (arrow 31) from above. The feed material is grasped by the distributor plate (30) and thrown approximately radially outwards. The feed material thrown outwards from the distributor plate (30) hits a baffle ring (32) arranged in the classifier housing (1) at a distance from the distributor plate (30), from which it falls downward into the classifying air stream (22) in the direction of the arrow (33) . By the impact of the Good things on the impact ring (32), which is very advantageously made of highly wear-resistant material or can be provided with a highly wear-resistant protective layer on the inside, the agglomerates or coarser goods that are still present in the feed material are comminuted or disagglomerated before they reach the classifying air stream (22) . To support the comminution or deagglomeration of good items and / or agglomerates present in the feed material, the distributor plate (30) in the outer area can additionally be equipped with conventional centrifugal blades or percussion elements. The feed material pretreated in this way passes into the space between the sight air guide elements (34) and the guide elements or rods of the rod basket (14) of the outer classifier wheel (4), where it is caught by the sight air flow (arrows 22) and by it in the direction of the arrow (22 ) carried inwards and is separated from one another in three fractions in the operating mode already described above in connection with the classifier according to FIG. 1. Since the classifier shown in FIG. 2 differs in its other components, in particular with regard to the design and arrangement of the classifying wheels (2, 3, 4), the drive, the supply and removal of classifying air as well as the supply of primary and secondary air from that in FIG 1 does not distinguish between the classifiers shown, for the sake of simplicity these components and drives, which are therefore identical in FIG. 2, have also been given the same reference numbers.

The classifier wheels (2, 3, 4) are driven from above in the classifiers shown in FIGS. 1 and 2. However, there is also the possibility of driving the classifier wheels from below, or in particular in the case of a classifier with only two classifier wheels, one classifier wheel from above and the second classifier wheel from below. In this connection, at least the classifying air discharge (16) can then be moved upwards or upwards from the classifier. In addition, it may also be expedient to carry out the discharge of the middle fraction (arrow 24) and / or the discharge of the fine fraction (arrow 25) by subtracting a partial air stream.

Otherwise, the classifier according to the invention can also advantageously be used and operated as a so-called two-section classifier in the partial final grinding of cement clinker. For this purpose, for example, the cement clinker, which is pressed into flakes in a high-pressure roller press and then deagglomerated, is fed to the classifier shown in FIG. 2 from above in the direction of the arrow (31). The first fraction obtained in the classifier, namely the coarse material (arrow 23) is returned to the high-pressure roller press, while the medium material (arrow 24) is used in a post-grinding unit, e.g. B. abandoned ball mill and is accordingly comminuted in this. The remilled material is then either fed to the classifier from above (arrow 35) through corresponding openings (36, 37) in the classifier housing and material distributor plate (30) and between the free space through which the classifying air flows the classifying wheels (3) and (4) introduced and sifted therein or directly mixed into the finished product. The grain fraction (arrow 25) falling down from the sight air stream, which is discharged to the outside from the channel (18), then represents the second fraction, namely the finished product. A third, from the sight air through the basket rods of the classifying wheel (2) The finest fraction carried inside is then discharged as a third finished product via the classifying air outlet (16). In the case of a classifier with only two classifier wheels, the second fraction is discharged from the classifier as a finished product with the classifying air flow and separated from the classifying air in a separator (filter) connected to the classifier. In order to avoid that parts of a classifier feed material are thrown outwards from the material distributor plate (30), an annular web (38) is attached to the material distributor plate (30) behind the openings (37).

There is also the possibility, as an alternative to the embodiment of FIG. 2, of feeding the feed material (35) via the shaft (5), provided that it is designed as a hollow shaft, and via corresponding openings in the wall of the hollow shaft onto the deck of the classifying wheel (2) .

Otherwise, the classifying wheels (2, 3 and 4) can be driven in the classifiers shown in the drawing figures as required, with the same direction of rotation and the same or different circulation speed or also with the opposite direction of rotation and the same or different circulation speed in order to optimally adapt the classifier to the material to be viewed or z. B. crushing and / or special deagglomeration effects. In addition, there is also the possibility of using the classifier according to the invention for classifying particularly fine-grained material into several fractions, with gases, such as, for. B. argon and the like are used. To homogenize the flow of visible air through the openings between the rods of the rod baskets (12, 13 and 14) and thus to improve the selectivity, the rods can be profiled accordingly, as is known, for example, from turbine construction. Furthermore, the free openings between the bars for the passage of the viewing air from the respective outer bar basket to the respective inner adjacent bar basket can be designed by adapting the shape of the bar, the number of bars and the height of the individual bar baskets instead of increasingly decreasing or essentially constant. Finally, if required, any number of classifier wheels according to the invention can be nested concentrically in the classifier housing and arranged at a corresponding distance from one another and operated with different directions of rotation. The crushing effect can also be intensified by the arrangement of scattering elements and / or impact elements on the crop distributor plate (30). Thus the
shown in the drawing figures, very simple and compact designed classifier according to the invention, many variations and uses.

Claims (8)

Sifter, in particular rod basket sifter with at least two classifying wheels, for classifying granular material in at least three fractions, consisting of a substantially vertically arranged housing with classifying air supply and classifying material supply as well as classifying air discharge and discharge for the fine and coarse material, characterized in that the classifying wheels (2 , 3, 4) in the housing (1) are nested concentrically and spaced from each other so that the sifting air flows through them one after the other and that each classifier wheel is assigned its own discharge. Classifier according to claim 1, characterized in that the classifying wheels (2, 3, 4) are mounted separately in the housing and can be driven independently of one another. A classifier according to claim 1 or 2, characterized in that the line (15) for supplying the classifying air is arranged laterally at the top of the housing (1), while the line (16) for classifying the classifying air in the housing (1) below the innermost classifier wheel (2) is arranged. Classifier according to claim 1, 2 or 3, characterized in that the classifier wheels (2, 3, 4) are equipped with rod baskets (12, 13, 14), whereby the free passage cross-section between the rods for the passage of the visible air through changed rod thickness and / or rod basket height from the respective outer rod basket to the inner neighboring rod basket according to the respective requirements for the separation task, either increasing , decreasing or essentially constant. A classifier according to claim 1, 2, 3 or 4, characterized in that a crop distributor plate (30) is arranged on the outer classifier wheel (4) at the top and is loaded with the feed material (31) from above. Classifier according to claim 5, characterized in that the crop distributor plate (30) is provided with openings (37) which open into the free space between two classifier wheels (3, 4). Sifter according to one of the preceding claims, in particular according to claim 3, characterized in that at least one further sifting air line (26) is connected below the sifter wheels (2, 3, 4) on the housing (1), which from below in each of the sifter wheels (2, 3, 4) located free space opens. Classifier according to claim 7, characterized in that the classifying air line (26) is connected to at least one of the classifying material discharges (18, 19, 20).

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