EP0525423B1 - Method and device for grinding materials of different sizes - Google Patents

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 fines content can be sifted out of the freshly fed regrind and fed to the wind sifter, which means that these 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 in 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 solved 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 in addition at least a part of the grit The outlet of the classifier to be returned to the comminution device of coarse material (semolina) is subjected to an after-inspection 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 investigations on which the invention is based, it has been shown that the coarse material coming from the classifier in the form of semolina is in many cases still contaminated with a relatively high proportion of fine material (finished product) which has already been comminuted sufficiently. Since a further over-grinding of this finished material contained in the returned coarse material costs additional energy, it has an extremely advantageous effect if at least a sufficiently large proportion of this fine material still contained in the returned coarse material is sifted out by means of the viewing device before this coarse material is 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 returned coarse material. In this way, 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 common sifting of fresh regrind and recycled coarse material is carried out, all of the fine material portions which have been aligned can 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 is even further is favored.

It should be emphasized at this point that it is generally possible for the overall configuration of the device according to the invention to arrange at least the comminution device and the sifter as separate devices, that as sifter both a dynamic wind sifter (with rotating viewing elements) and a static wind sifter (without rotating viewing elements) and that, in addition, any design suitable for the comminution of regrind of different grain size, in particular for more or less brittle mineral material, can be provided as the comminution device.

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) rolling on a rotatable grinding table, 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. This then connects a mechanical conveying device, preferably a screw conveyor, a simple material chute or the like., the grit 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 simultaneously 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:

Fig. 1

A schematic vertical sectional view through a roller mill with a sifter arranged above in the construction according to the invention;

Fig. 2

a schematic view of a second embodiment of the shredding device according to the invention, also in the form of a roller mill with a sifter arranged above 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 way a grinding plate 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 wind sifter 2 is formed by a static wind sifter, which in the usual way has ring-shaped guide vanes 8, a coarse material hopper 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. These 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 now that in the area between the Gresse outlet 11 of the air classifier 2 and the Re-introduction point of coarse material to be returned (semolina) into the roller mill 1, an after-inspection device for viewing fine parts from this coarse material is arranged. 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), said screw conveyor 16 - in the direction of regrind (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 sucked in by means of a fan (not illustrated in more detail) connected to the fine material outlet 10 of the device housing 3 through a nozzle ring 19 surrounding the grinding table 5 and together with the sufficiently crushed ground material discharged over the edge of the grinding plate 5 is directed to the air classifier 2 (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 the fine material portions (arrows 23) which are aligned by the resulting cross flow can be fed directly to the air classifier 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 added 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 it grinds the grinding path 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, the same or similarly designed device parts are designated with the same reference numerals with the addition of a dash for the sake of simplicity, 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 'is used as the comminution device vertical device axis 4 'and as a sifter a wind sifter 2' are provided directly above the roller mill 1 'in a common device housing 3', with fresh regrind (arrow 12 ') being fed to the roller mill 1' via a similar fresh material feed chute 13 ', the Floor 13a '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 meal - Outlet 11 'coarse material flowing out - according to arrow 25 - to a separate lifting elevator (as a mechanical lifting conveyor) 26, which this coarse material portion - possibly together with a portion of the comminuted material dropping 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' Experienced indulgence, which in turn can relieve the roller mill of the already finely comminuted fine material (finished product). As is 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 guided downwards centrally 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 indicated at 27a to open directly into the annular, upper wind classifier outer area 30, by which the ground material-air mixture (arrows 20 ') conveyed from the grinding table 5'a reaches this wind sifter 2'. As indicated by the dot-dash line in FIG. 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 optionally the oversized coarse material portions are distributed to the spreading plate 2 via the first inlet nozzle 27 'a fed or directly introduced into the annular air classifier outer region 30 via the second crop inlet pipe 27a, and there is also the possibility of arranging a sorting device at 33, so that the overwrought 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 180 °).

If the raised, recycled 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 particularly advantageously by the upward gas flow sighted from the recycled semolina, and it is possible to achieve a particularly good distribution of regrind on the grinding table and thereby greater smoothness of the roller mill 1 ', and in addition there is advantageously the possibility of using existing classifiers without a spreading plate, i.e. static wind classifier, simply and inexpensively to retrofit accordingly.

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 a viewing 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. Apparatus for the crushing of material for grinding of differing grain size, containing

   a) a crushing device (1, 1'),

   b) a feed device (13, 13') for fresh material for grinding (12, 12') which is associated with the crushing device and has an arrangement (14, 15) for introducing at least one air stream which separates the fine particles out of the fresh material for grinding,

   c) a separator (2, 2') for the crushed material for grinding which contains a fine material outlet (10, 10') as well as a tailings outlet (11, 11') to return oversize material to the crushing device,

   characterised in that

   d) a secondary separating device (13a, 2') to separate fine particles out of this oversize material is arranged in the region between the tailings outlet (11, 11') of the separator (2, 2') and the reintroduction point for the returned oversize material (17) into the crushing device (1, 1').
2. Apparatus as claimed in claim 1, characterised in that the secondary separating device is constructed approximately in the form of a material feed chute (13) with a base (13a) running obliquely downwards, to which is connected at least one inlet channel (14, 15) for separating air which is controllable in its flow cross-section.
3. Apparatus as claimed in claim 2, in which the delivery device for fresh material for grinding is constructed in the form of a fresh material feed chute (13) with a base (13a) running obliquely downwards, to which is connected at least one inlet channel (14, 15) for separating air, characterised in that the tailings outlet (11) of the separator (2) is connected via a conveyor device (16) to the fresh material feed chute (13) and this fresh material feed chute simultaneously forms the secondary separating device for oversize material returned from the separator to the crushing device (1), the fine particles (23) separated out being capable of being delivered jointly to the separator.
4. Apparatus as claimed in claim 3, characterised in that the conveyor device (16) for returned oversize material - viewed in the direction of conveying the material for grinding (arrow 12) - is connected to the fresh material feed chute (13) in the region before the separating air entry into the fresh material feed chute.
5. Apparatus as claimed in claim 1, characterised in that the secondary separating device is constructed in the form of a separate air separator device in which the oversize material outlet is connected to the crushing device and the fine material outlet is connected to the separator inlet.
6. Apparatus as claimed in claim 2, characterised in that the crushing device is constructed in the form of a roller mill (1, 1') with a vertical axis and with grinding tools (6) rolling on a rotatable grinding table (5, 5'), and the separator is arranged as an air separator (2, 2') immediately above the roller mill in a common device housing (3, 3') with this roller mill, a mechanical conveyor device being provided between the tailings outlet (11, 11') of this air separator and the secondary separating device (13, 2').
7. Apparatus as claimed in claim 6, with a separate mechanical lift-over conveyor (26) for crushed material falling downwards from the grinding table (5'), characterised in that

   a) the air separator (2') simultaneously forms the secondary separating device for the proportion of oversize material to be subjected to secondary separation,

   b) the mechanical conveyor (16') arranged after the tailings outlet (11') is connected to the lift-over conveyor (26) and

   c) the material outlet (26a) of the lift-over conveyor (26) is connected to a material inlet connection (27, 27a) of the air separator (2').
8. Apparatus as claimed in claim 7, characterised in that the material inlet connection (27) of the air separator (2') opens above the distributor plate (2'a) of the air separator.
9. Apparatus as claimed in claim 7, characterised in that the material inlet connection (27a) of the air separator (2') opens directly into the annular upper outer region (30) of the air separator through which the mixture of material for grinding and air (20') conveyed from the grinding table (5'a) is introduced into the air separator.
10. Apparatus as claimed in claim 6, characterised in that an adjustable quantity distribution device (16') is arranged after the tailings outlet (11') of the air separator (2'), the said device being connected on the one hand to the grinding table (5') of the roller mill (1') and on the other hand to the secondary separating device (2').
11. Apparatus as claimed in claim 10, characterised in that the mechanical conveyor device (16') arranged after the tailings outlet (11') simultaneously forms the adjustable quantity distribution device.
12. Apparatus as claimed in claim 11, characterised in that the mechanical conveyor device is formed by a screw conveyor (16') with a regulable drive (28).
13. Method of crushing material for grinding of differing grain size, in which fresh material for grinding is subjected to primary separation in the delivery region before a crushing device by the introduction of a stream of separating air after the proportions of fine material have been delivered jointly with the material crushed in the crushing device to an air separator from which precipitated fine material is drawn off and oversize material precipitated as grit is returned to the crushing device, characterised in that at least a proportion of the oversize material to be returned is subjected to secondary separation to separate out fine particles before it is fed into the crushing device.
14. Method as claimed in claim 13, characterised in that the oversize material to be subjected to secondary separation is delivered to the fresh material for grinding and this oversize material together with the fresh material for grinding are subjected to the stream of separating air before being delivered into the crushing device.
15. Method as claimed in claim 13, characterised in that the oversize material to be subjected to secondary separation is fed back to the air separator via a conveyor device.
16. Method as claimed in claim 13, characterised in that a roller mill with a vertical axis and with an air separator built immediately above it is used for the crushing and air separation of the crushed material for grinding.

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