EP0525423A1 - Method and device for grinding materials of different sizes - Google Patents

Abstract

In order to grind materials of different granular sizes, a grinding device, a feeder device for fresh material for grinding, in which device portions of fine material are sifted out of the fresh material for grinding, and a sifter for the ground material are provided. In order to further increase the grinding capacity of the grinding device, coarse material which is to be fed back from the sifter to the grinding device can be fed to a resifting device for sifting out portions of fine material. <IMAGE>

Description

The invention relates to a device (according to the preamble of claim 1) and a method (corresponding to the preamble of claim 8) for comminuting regrind of different grain sizes.

From EP-A-370 267 it is known to provide a device in a roller mill with an air classifier arranged directly above it, via which fresh regrind is fed to the rotating grinding table (with grinding rollers rolling thereon). This feed device designed in the manner of a material feed chute is preferably provided on its obliquely downwardly extending bottom with two air inlet channels, through which an air stream can be fed in such a way that fine material portions can be sifted out of the freshly fed regrind and fed to the air classifier, thereby making them Crushing device is relieved of the selected fines content and thus its crushing performance is to be improved.

The invention is based on the object of improving a device of the type required in the preamble of claim 1 and a method according to the preamble of claim 8 in such a way that by relatively simple measures at least an additional increase in performance when comminuting the ground material can be reached.

This object is achieved on the one hand by the characterizing features of claim 1 and on the other hand by the characterizing features of claim 8. Advantageous refinements and developments of this invention are the subject of the dependent claims.

In this embodiment according to the invention - in contrast to the known embodiment according to EP-A-370 267 explained above - not only the fresh regrind to be fed to the comminution device is relieved by a kind of precaution of fines content, but at least a part of the amount The outlet of the classifier to be returned to the comminution device of coarse material (semolina) is subjected to an indulgence in order to sift out at least a substantial proportion of the sufficiently fine fine material components still contained in this coarse material. For this purpose, in the area between the size outlet of the classifier and the re-introduction point of this coarse material into the comminution device, a suitable after-viewing device for viewing fine parts from this coarse material is arranged.

In the studies on which the invention is based, it has been shown that the coarse material coming from the classifier in the form of semolina is often still contaminated with a relatively high proportion of fine material (finished product) that has already been comminuted sufficiently. Since a further over-grinding of the finished goods contained in the returned coarse goods costs additional energy, it has an extremely advantageous effect if at least a sufficiently large proportion of these fine goods still contained in the returned coarse goods is sifted out by means of the viewing device before these coarse goods are drawn into the grinding tools of the comminution device becomes. These grinding tools and thus the entire comminution device can therefore be relieved of the selected fine material portions, which creates particularly good conditions not only to improve the comminution work, but also to further increase the comminution performance of the comminution device.

According to a particularly simple embodiment, the after-viewing device can be designed, for example, in the form of a material feed chute with an obliquely downwardly extending floor, to which at least one viewing air inlet duct which is adjustable in terms of its flow cross section is connected. An after-vision device designed in this way can be parallel, if necessary. H. be provided regardless of the feed device for the fresh regrind.

If the feed device for fresh regrind to the shredding device is also designed in the form of a fresh material feed chute with a sloping bottom, to which at least one sight air inlet duct is connected, then it can also be particularly advantageous if the size outlet of the classifier is connected to this fresh material feed chute via a conveying device and this fresh material feed chute simultaneously forms the after-inspection device for at least the largest proportion of the coarse material returned from the classifier to the comminution device or for all coarse material returned. This means that coarse material coming from the classifier can then be fed to the fresh material feed chute and thus to the fresh regrind in such a way that on the one hand a joint screening of fresh regrind and recycled coarse material is carried out, with all of the fine material portions that are aligned being able to be fed together to the classifier. On the other hand, with this joint sifting, an extremely intensive mixing of the freshly supplied ground material (feed material) with the returned coarse material is also brought about, so that a very uniform total ground material mixture can be fed into the shredding tools of the shredding device, whereby the shredding work in this shredding device still further is favored.

It should be emphasized at this point that it is for the overall training of the Einrich invention tion is generally possible to arrange at least the shredding device and the sifter as separate devices, that further as a sifter both a dynamic wind sifter (with rotating viewing elements) and a static wind sifter (without rotating viewing elements) and that also as a shredding device each for the shredding of regrind different grain sizes, in particular suitable for more or less brittle mineral material, can be provided.

According to a particularly preferred embodiment of this device according to the invention, however, the comminution device is designed in the form of a known vertical-axis roller mill with grinding tools (grinding rollers or grinding balls) that roll on a rotatable grinding plate, and the separator is in a manner known per se directly above the roller mill arranged in a common device housing with this roller mill. In this case, a mechanical conveyor, preferably a screw conveyor, a simple material chute or the like, connects the Greisses outlet of this air classifier with the indulgence device, which can be formed in a particularly compact design of the overall device according to the above-described embodiment by the fresh material feed chute .

• Fig.1 Eine schematische Vertikalschnitt-Ansicht durch eine Wälzmühle mit darüber angeordnetem Sichter in erfindungsgemäßer Bauweise;
• Fig.2 eine Schemaansicht eines zweiten Ausführungsbeispieles der erfindungsgemäßen Zerkleinerungseinrichtung, ebenfalls in Form einer Wälzmühle mit darüber angeordnetem Sichter sowie mit äußerem Überhebeförderer.

The invention will be described in more detail below with reference to some exemplary embodiments illustrated in the drawing. In this drawing:

• 1 shows a schematic vertical sectional view through a roller mill with a sifter arranged above in the construction according to the invention;
• 2 shows a schematic view of a second exemplary embodiment of the comminution device according to the invention, likewise in the form of a roller mill with a sifter arranged above it and with an external lifting conveyor.

In the first exemplary embodiment illustrated in FIG. 1, the comminution device according to the invention is provided as a particularly preferred, extremely compact structural unit comprising a comminution device in the form of a vertical axis roller mill (roller mill) 1 known per se and an air classifier 2 arranged directly above it (in a form known per se) . The roller mill 1 and the air classifier 2 arranged above it are - as is also known per se - housed in a common device housing 3.

The roller mill 1, which is only illustrated schematically, has, in the usual manner, a grinding table 5 which is rotatably driven about the vertical device axis 4 and has an upper, annular grinding path 5a on which stationary grinding rollers 6 roll, so that supplied grinding material 7 is crushed between grinding path 5a and grinding rollers 6 .

In this exemplary embodiment (FIG. 1), the air classifier 2 is formed by a static air classifier, which in the usual way has ring-shaped guide vanes 8, a coarse material funnel 9, an upper fine material outlet 10 and - at the lower end of the coarse material funnel 9 - Is provided with a lower Gresse outlet 11, which, if necessary, can also have a pendulum flap - not illustrated here.

The fresh ground material to be comminuted (arrow 12) is fed to the roller mill 1 via a fresh material feed chute 13 which is assigned to the roller mill 1 in such a way that the ground material arrives at the grinding path 5a. This fresh material feed chute 13 has a sloping bottom 13a, to which two sifting air inlet channels 14 and 15 are connected in this example. This sifting air inlet channels 14, 15 can be regulated or adjusted in their flow cross section, for example with the aid of sliders, so that the amount of sifting air and the effectiveness of the sifting air on the regrind 1 to be fed to the roller mill 1 can be regulated accordingly.

It is of particular importance that an after-inspection device is arranged in the area between the grit outlet 11 of the air classifier 2 and the point of re-introduction of coarse material to be returned (roller) into the roller mill 1 for the purpose of viewing fine parts from this coarse material. In the exemplary embodiment according to FIG. 1, for this purpose, the grit outlet 11 is first connected to the fresh material feed chute 13 via a screw conveyor 16 (or else via another suitable mechanical conveyor device), this screw conveyor 16 - in the millbase conveying direction (arrow 12) considered - in the area in front of the sight air inlet (inlet channels 14 and 15) into the fresh material feed chute 13 is connected to the latter. As will be explained in more detail, the fresh material feed chute 13 provided with the visible air inlet channels 14 and 15 thus simultaneously forms a kind of caution device for the fresh regrind (arrow 12) and rechecking device for the coarse material to be returned from the air classifier 2 to the roller mill 1 (arrow 17). .

In the operation of this first exemplary embodiment illustrated in FIG. 1, a gas stream (arrows 18), preferably furnace gas, is surrounded by a grinding plate 5 by means of a fan (not illustrated in more detail) connected to the fine material outlet 10 of the device housing 3 the nozzle ring 19 is sucked in and passed to the wind sifter 2 together with the sufficiently comminuted ground material discharged over the edge of the grinding plate 5 (arrows 20). In the air classifier 2 coarse material (arrows 17) precipitates and is returned to the grinding path 3 of the roller mill 1 via the coarse material funnel 9, the grit outlet 11, the screw conveyor 16 and the material feed chute 13 (together with the fresh regrind), while the fine material (Arrows 21) leaves the air classifier 2 through the nozzle-like fine material outlet 10.

According to the invention, with the help of the additional visual air (arrows 22) introduced into the fresh material material feed chute 13 via the visual air inlet channels 14 and 15, both a caution of the freshly fed ground material (arrow 12) and an indulgence of the coarse material returned via the screw conveyor 16 ( Arrow 17) is carried out in such a way that all of the fine material portions (arrows 23) aligned by the resulting cross flow can be fed directly to the wind sifter 2 together with the ground material sufficiently comminuted in the roller mill 1. In this way, a sufficiently high proportion of fine and very fine material is selected not only from the freshly introduced regrind, but also from the coarse material (semolina) returned by the wind sifter 2, before the entire regrind to be fed to the grinding path 5a, before this grinds 5a and reached the grinding tools (grinding rollers 6). A significant increase in performance of the roller mill 1 and a significant improvement in the grinding work in this roller mill can thus be achieved.

In the exemplary embodiment illustrated in FIG. 2, for the sake of simplicity, identical or similarly designed device parts are designated with the same reference numerals with the addition of a dash, so that a further detailed explanation of these device parts is unnecessary.

In this second example, too, it is assumed that a roller mill 1 'with a vertical device axis 4' is provided as the crushing device and a wind sifter 2 'is provided directly above the roller mill 1' in a common device housing 3 'as a sifter, with fresh regrind (arrow 12') the roller mill 1 'is fed via a fresh material feed chute 13' of the same type, the bottom 13a 'of which is in turn provided with controllable viewing air inlet channels 14' and 15 '.

In this example according to FIG. 2, it is assumed - as a variant of the example according to FIG. 1 - that the wind sifter 2 'is a dynamic wind sifter which has viewing elements which can be driven to rotate about the vertical device axis 4' and have a rotating spreading disc 2'a . Otherwise, this air classifier 2 'in turn has a fine material outlet 10', a coarse material funnel 9 'and a grit outlet 11'.

In contrast to the first exemplary embodiment described above, the screw conveyor 16 'does not connect the spout 11' of the air classifier 2 'to the fresh material feed chute 13' which also acts as a viewing device, but rather the screw conveyor 16 'preferably only conveys an adjustable proportion of that from the semolina - Outlet 11 'coarse material flowing out - according to arrow 25 - to a separately installed lifting device (as a mechanical lifting conveyor) 26, which this coarse material portion - possibly together with a portion of the comminuted material falling down from the grinding table 5 - to a material inlet nozzle 27 for the air classifier 2 'promotes, which in this embodiment also forms the viewing device for the portion of coarse material to be checked (portion of portion).

The coarse material parts conveyed out of the device housing 3 'by the screw conveyor 16' thus pass from the lifting elevator good outlet 26a via the material inlet nozzle 27 to the spreading plate 2'a of the air classifier 2 ', so that the mechanically guided and overlapped coarse material part in this dynamic air classifier 2' Forbearance is experienced, which in turn enables the desired relief of the roller mill from already comminuted fine material (finished product). As indicated in FIG. 2 by the dashed arrows 29, a corresponding proportion of coarse material can be thrown outwards from the feed material thrown outwards from the spreading plate 2'a and can be returned directly to the grinding table 5'a along the inner wall of the device housing 3 ' , while other coarse material portions are routed centrally downwards via the coarse material funnel 9 'to the semolina outlet 11'.

The portion of coarse material which is not conveyed out of the device housing 3 'by the screw conveyor 16' can be fed directly to the grinding track 5'a, but possibly also to an indulgence in the fresh material feed chute 13 '.

While in the embodiment of the example according to FIG. 2 described so far, the inlet spout 27 of the air classifier 2 'opens out over the annular spreader plate 2'a, it is optionally or additionally also possible for the inlet spout or a further inlet spout of the air classifier 2' in the at 27a indicated type to open directly into the ring-shaped upper air classifier outer area 30 through which the ground material-air mixture (arrows 20 ') conveyed from the grinding plate 5'a reaches this air classifier 2'. How to knit this 2, this second crop inlet connection 27a can be connected to the lifting elevator crop outlet 26a via a connecting line or partial line 31. In addition, there is the possibility - as also indicated by dash-dotted lines - to provide the line 32 connecting the lifting elevator good outlet 26a with the (first) good inlet connector 27 with a switch or flap 33, so that the oversized coarse material portions can optionally be distributed over the first inlet connector 27 to the spreading plate 2 'a fed or directly introduced into the annular air classifier outer area 30 via the second crop inlet pipe 27a, and there is also the possibility of arranging a sorting device at 33, so that the oversized coarse material portions are partly fed to the spreading plate 2'a and partly directly can be introduced into the wind classifier outer area 30. The first material inlet nozzle 27 and the second material inlet nozzle 27a can expediently be offset from one another in the circumferential direction (for example by approximately 1800). ).

If the raised, recirculated coarse material portions are passed directly into the annular air classifier outer area 30 bypassing the spreading plate 2'a, then this takes place against the rising gas flow or regrind-air mixture (arrows 20 '), so that at least the particularly coarse ones Good portions - according to arrows 29 - fall directly in front of the grinding tools (grinding rollers) of the roller mill 1 'onto the grinding plate 5'a. As a result, the fines are selected in a particularly advantageous manner by the upward gas flow from the recycled semolina, and a particularly good distribution of the grinding material on the grinding plate and thereby a smoother running of the roller mill 1 'can be achieved, and there is also the possibility in an advantageous manner to retrofit existing classifiers without spreading disc, i.e. static wind classifiers, easily and inexpensively.

In order to be able to carry out the described quantitative distribution of the coarse material flowing out through the freeze outlet 11 'of the air classifier 2' in a suitable manner, the freeze outlet 11 'can be followed by an adjustable quantitative distribution device which, on the one hand, can be connected to the grinding plate 5' (if necessary via the Fresh material feed chute 13 ') and on the other hand - via the screw conveyor 16' and the lifting device 26 - is connected to the dynamic wind sifter 2 ', which also acts as an indulgence device. Such an adjustable quantity distribution device can be designed in any suitable manner. In the example according to FIG. 2, it is assumed that the screw conveyor 16 'has a drive 28 which can be regulated in such a way that a more or less large overflow of material occurs at the inlet end 16'a of the screw conveyor 16' and this overflowing portion of coarse material then passes to the grinding table 5 'or if necessary, the fresh material feed chute 13 'is fed.

The crushing work and effect as well as the visual work of this exemplary embodiment (FIG. 2) within the device housing 3 or the material feed chute 13 'are otherwise the same as has been described in detail with reference to FIG.

Claims (16)

1. Device for crushing regrind of different grain size, containing a) a comminution device (1, 1 '), b) a feed device (13, 13 ') for fresh regrind (12, 12') assigned to the comminution device, which has a device (14, 15) for introducing at least one air stream which looks at the fines content from the fresh regrind, c) a classifier (2, 2 ') for the comminuted regrind, which contains a fine material outlet (10, 10') and a grit outlet (11, 11 ') for returning coarse material to the comminution device,
characterized in that d) in the area between the grit outlet (11, 11 ') of the classifier (2, 2') and the point of re-introduction of the returned coarse material (17) into the shredding device (1, 1 ') an after-inspection device (13, 2') for Prospects of fines from this coarse material is arranged. 2. Device according to claim 1, characterized in that the viewing device is approximately in the form of a material feed chute (13) with an obliquely downward bottom (13a) is formed, to which at least one in its flow cross section adjustable viewing air inlet channel (14, 15th ) connected. 3. Device according to claim 2, wherein the feed device for fresh regrind in the form of a fresh material feed chute (13) with an inclined bottom (13a) is formed, to which at least one classifying air inlet channel (14, 15) is connected, thereby characterized in that the grit outlet (11) of the classifier (2) is connected to the fresh material feed chute (13) via a conveying device (16), and this fresh material feed chute is simultaneously the after-viewing device for the classifier Crushing device (1) forms returned coarse material, the fine material portions (23) that are aligned being able to be fed together to the classifier. 4. Device according to claim 3, characterized in that the conveying device (16) for returned coarse material - viewed in the grinding material conveying direction (arrow 12) - in the region before the inlet of fresh air into the fresh material feed chute (13) is connected to the latter. 5. Device according to claim 1, characterized in that the after-viewing device is designed in the form of a separate wind-screening device, the coarse material outlet of which is connected to the comminution device and the fine material outlet of which is connected to the classifier inlet. 6. Device according to claim 2, characterized in that the comminution device in the form of a vertical-axis roller mill (1, 1 ') with grinding tools (6, 5') which roll on a rotatable grinding table (5, 5 ') and that the classifier is an air classifier ( 2, 2 ') is arranged directly above the roller mill in a common device housing (3, 3') with this roller mill, a mechanical conveying device (16, 16 ') between the grit outlet (11, 11') of this air classifier and the Viewing device (13, 2 ') is provided. 7. Device according to claim 6, with a separate mechanical lifting conveyor (26) from the grinding table (5 ') falling down comminuted material, characterized in that a) the wind sifter (2 ') simultaneously forms the inspection device for the portion of coarse material to be inspected, b) the mechanical conveyor (16 ') downstream of the grit outlet (11') is connected to the lifting conveyor (26) and c) the product outlet (26a) of the lifting conveyor (26) is connected to a product inlet connection (27, 27a) of the air classifier (2 '). 8. Device according to claim 7, characterized in that the material inlet nozzle (27) of the air classifier (2 ') opens out over the spreading plate (2'a) of the air classifier. 9. Device according to claim 7, characterized in that the Guteinlaufstutzen (27 a) of the air classifier (2 ') opens directly into the annular, upper wind classifier outer area (30) through which the grist air conveyed from the grinding plate (5'a) Mixture (20 ') is introduced into the air classifier. 10. A device according to claim 6, characterized in that the adjustable outlet (11 ') of the air classifier (2') is followed by an adjustable quantity distribution device (16 ') which on the one hand with the grinding plate (5,) of the roller mill (1') and, on the other hand, is connected to the viewing device (2 '). 11. The device according to claim 10, characterized in that the mechanical outlet device (16 ') downstream of the grit outlet (11') simultaneously forms the adjustable quantity distribution device. 12. The device according to claim 11, characterized in that the mechanical conveyor device is formed by a screw conveyor (16 ') with a controllable drive (28). 13. A method for comminuting regrind of different grain sizes, in which fresh regrind in the feed area in front of a comminution device is subjected to a precaution by introducing a stream of classifying air, after which fines content together with the regrind comminuted in the comminution device are fed to a wind sifter, removed from the fines obtained and removed Any coarse material obtained as a meal is returned to the comminution device, characterized in that at least a portion of the coarse material to be returned is subjected to an indulgence for the prospect of fines content before being put into the comminution device. 14. The method according to claim 13, characterized in that the coarse material to be re-fed to the fresh regrind and this coarse material is subjected together with the fresh regrind to the classifying air stream before being fed into the comminution device. 15. The method according to claim 13, characterized in that the coarse material to be inspected is again fed to the air classifier via a conveying device. 16. The method according to claim 13, characterized in that a vertical-axis roller mill with a built-on wind sifter is used for the comminution and the wind sifting of the comminuted ground material.

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