EP0801229A2 - Pump - Google Patents

Abstract

An outer part (8) of the running wheel (3) extends out of the pump housing (2). With rotation of the running wheel materials picked up by the worm shape of the outer running wheel are drawn into the running wheel aperture of the pump housing as pump input and are impelled. A somewhat tangential pump outlet (10) is provided in the torus-shaped pump housing and a drivable pump shaft (4) is connected coaxially with the outer running wheel part. A striker strip edge (17,18) or the worm periphery edge (9) have cavities (25) or raised formations (26) as obstructions for the disintegration of the solid material moved past the outer running wheel part.

Description

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

A generic pump known from prior use (DRP 4000 E, manufacturer U.T.S. Umwelt-Technik-Süd GmbH) comprises a toroidal pump housing and a screw-shaped pump impeller which is approximately coaxial with the pump housing. The pump impeller projects with an inner impeller part into the pump housing and projects with an outer impeller part out of the pump housing. During an impeller rotation, materials that can be detected by the screw shape of the outer impeller part are conveyed into the impeller opening of the pump housing as the pump inlet. The pump impeller is connected to a coaxial driven pump shaft.

The inner impeller part in the pump housing has wing-like extensions which move materials to be pumped further in the pump housing and push them out of the toroidal pump housing from an approximately tangential pump outlet. Depending on the circumstances, the shape of the torus is not circular, but is extended towards the pump outlet with a somewhat larger radius.

A blow bar with a blow bar edge is also attached in the area of the peripheral edge of the screw of the outer impeller part. The screw circumferential edge runs past the blow bar edge at a short distance, the blow bar edge being in one plane the impeller axis. In the known pump, the screw shape of the impeller tapers conically away from the pump housing, at least in the region of the outer impeller part, so that the blow bar edge is also inclined in accordance with the cone inclination.

A shaft bearing of the pump shaft is located at a distance from the pump housing. The pump housing and the shaft bearing are connected to one another via two bow-shaped arms located opposite one another and offset laterally to the axial direction, the outer impeller part rotating freely between these connecting arms in the medium to be pumped. Blow bars are attached to the arms facing the impeller. The arrangement of these two connecting arms essentially determines the size and shape of two impeller openings as pump openings.

The blow bar edges and the peripheral edge of the screw running past them are provided with a hard metal weld in the manner of a hard metal bead with a rough surface. Apart from the relatively low roughness of the weld, the blow bar edges and, correspondingly, the screw peripheral edge run straight through without any further structure.

This pump is used for the conveyance of industrial and agricultural wastewater that is contaminated with solids, especially with clogging materials, such as those that occur in sewage treatment plants. By using the blow bars in the area of the outer impeller part, there is an additional crushing effect for solid contaminants, so that the pump in a device contains the functions of conveying, crushing and mixing solid contaminants.

A processing comminution of biological residues, as they occur, for example, from households in bio-bins, is with the known Pump is only possible to a limited extent even with a liquid suspension of these residues. Larger, more stable solid parts are often not correctly grasped and are not sufficiently torn and dismembered. In addition, the arrangement tends to clog and block, which can only be countered by high engine power. Furthermore, the pumping effect is reduced and unsatisfactory because of the insufficient size reduction. When using the known pump for processing materials with a higher solids load, such as for example for processing biological residues even when adding liquid, a sufficiently good result is therefore not obtained.

The shredding of biological residues is currently usually dry, i. H. performed without adding liquid using choppers and / or shredders. Such systems are large, very expensive and have a high energy requirement.

Only after this dry comminution, depending on the further processing, liquid is added for stirring and pumping processes. There are therefore several machines required as comminution machines and downstream stirring and pumping machines. Such extensive, expensive facilities are only economically viable in large systems. In particular, such facilities are too expensive for decentralized recycling of biological residues by agricultural businesses.

Such a known type of utilization consists in the operation of biogas plants in which biological residues are gasified in fermenters. The gases generated are mostly used as fuel for downstream internal combustion engines. Crushing biological residues is very advantageous before charging a biogas plant, since then larger surfaces are available for contact with microorganisms and the gas production is accelerated as a result.

Such decentralized, small biogas plants in the agricultural sector are desirable for reasons of economy and environmental protection: only short, traffic-reducing transport routes are required for the transport of biological residues from households. Large, odor-intensive landfill sites and composting plants are no longer necessary. Agricultural, biological residues can be recycled on site and used as energy. Funding programs are currently underway to introduce this decentralized biogas technology on a larger scale.

Furthermore, simple centrifugal pumps are known (DE-AS 28 55 385 and CH-PS 400 726) with an axially opposite pump inlet and pump outlet opening of a conical housing in which a screw-shaped, correspondingly conical, adapted pump impeller rotates. These pumps are purely feed pumps for solids-contaminated liquids, in which no operational comminution but only a small amount of deposited or trapped solids in the pump housing is to be undertaken to prevent pump blockage. For this purpose, a pump design has at least part of the fixed inner wall of the pump housing which is swept by the impeller and has a deflecting surface which winds in the direction of the impeller rotation around the impeller axis after the outlet and which can be designed both as a groove and as a rib. In such centrifugal pumps, the pump inlet and pump outlet openings are coaxially exposed. This creates the possibility that long-fiber solids, such as. B. ropes, nylon stockings and the like can be detected again when the pump passes through the pump inlet to form a loop. Such loops lead to a reduction in performance and possibly blockage of the pump. In order to cut open such loops, a special design of the blade end edges of the pump wheel is proposed in another pump design. With none however, these pumps have external impeller parts with associated blow bars.

Furthermore, a cutting device in front of the suction opening of a slurry pump with a bearing in the suction opening for the shaft of a stirring device is known (DE-OS 1 403 263). This cutting device consists of knives, which cut over the suction opening and cut long-fiber material by brushing the ribs arranged in the suction opening as counter knife. The knives are thus designed here as pump-centrally driven rotary knives which rotate in one plane transverse to the suction direction. The knife arrangement or cutting arrangement corresponds to a conventional scissor arrangement in which the cutting surfaces are moved one above the other in a plane and an initially larger scissor angle is reduced for a cutting effect. Such an angular reduction forces the material to be cut out of the scissors area with the formation of barks. As a result, the knife has to overcome the greatest resistance at the edge of the suction opening, ie on the outside, since most parts have to be cut there, while little is cut on the inner part, disadvantageously the length of the cutting edge is not used uniformly. In order to reduce this unfavorable effect, projections and depressions are provided along the cutting edge of the counter knife and the cutting edge of the knife, among other things. This corresponds to a serrated arrangement, as is well known for this purpose in household scissors, for example. The pushing-out movement of the material to be cut is at least partially supported on the shaft flanks of the serrated edge directed towards the pivot point, since the cutting edges move one above the other while reducing the scissor angle and thus the material to be sliced is held in place by the serrated edge arrangement. In the generic pump described at the outset, on the other hand, blow bars and a peripheral edge of the screw are used for comminution, which in a predetermined, practically constant angle, which is determined by the screw pitch, past each other, so that the reduced disadvantage of rotary knives with a serrated edge arrangement does not occur here. In the generic pump, the material to be cut is moved parallel to the axis of rotation in the conveying direction, in that the respective intersection between the fixed cutting edge and the worm cutting edge moves in the conveying direction. This further movement supports the promotional effect.

The object of the invention is to develop a generic pump so that it is suitable for crushing, stirring and conveying liquids and sludges that are highly contaminated with solids, in particular for comminuting liquid-containing biological residues as preparation and for charging for biogas plants.

This object is achieved in particular with regard to an improvement of the comminution function with the characterizing features of claim 1.

According to claim 1, the blow bar edge and / or peripheral screw edge of a generic pump has depressions and / or elevations as an obstacle to the comminution of solids moving past by the outer impeller.

The pump according to the invention is therefore generally suitable for stirring and conveying waste water with a high solids load. Such a pump according to the invention has proven to be particularly advantageous for processing biological residues. The function of a chopper or shredder and a conveyor is implemented in a single device. A preferred application is the decentralized processing and recycling of biological residues with smaller biogas plants, especially in the agricultural sector.

In previous conventional processes, the biological residues were delivered directly to the fermenter in a biogas plant or were comminuted dry in a first process step and, if necessary, stored temporarily before the fermenter was loaded. In the fermenter, however, it is necessary to add liquid to the biological residues. When using the pump according to the invention with an integrated chopper and comminution device, it is necessary to mix the biological residues with liquid as soon as they are fed to the pump. Since this is necessary for a gasification process anyway, this does not represent a disadvantage compared to the previous processes. Rather, the biological residues are mixed with liquid in a single operation, intensively torn and shredded to create large surfaces, and also in the suitable, liquid-mixed preparation in the Promoted fermenter. All of these processes require only the single pump device according to the invention as a compact, easy-to-assemble and easy-to-install machine with a single drive unit.

The formation of the depressions and / or elevations on the blow bar edges and / or the screw peripheral edge can be adapted to a certain extent to the type of materials to be processed. The depressions and / or elevations should in any case be selected in a size so that the parts can be grasped by the impeller after the size reduction and can be transported. On the other hand, the depressions and / or elevations are to be chosen so large that the materials between them are well torn and shredded.

An arrangement of the depressions and / or elevations according to claim 2 over the entire length of the blow bar edge and / or the screw peripheral edge at least in the region of the outer impeller part is particularly suitable. This results in a jagged, overall computing or comb-like edge structure through which the solid materials are pushed and thus crushed, in particular due to the shear movement of the screw. The structure can have different shapes depending on the materials.

A very intensive size reduction with high efficiency is achieved with the features of claim 3. The structure on the blow bar meshes with the structure on the passing peripheral edge of the screw with an intermediate gap. The gap width can be adapted to the main materials to be processed for optimal comminution.

The depressions and / or elevations can, if necessary, be provided with cutting edges, the cutting edges suitably following the edge course. This measure is particularly advantageous in the case of stable, hard-to-cut solids, such as wood chips or harder industrial waste. Furthermore, in order to avoid rapid wear of the edges, the depressions and / or elevations can be made of hard materials, preferably hard metal, or they can be coated with hard metal welding in a manner known per se. A structure size from 5 to 25 mm has proven to be well suited.

In a development of the invention according to claim 5 it is proposed that at least one blow bar can be rotated about a longitudinal axis. Such a rotatable blow bar can have several blow bar edges offset on the circumference. The blow bar can be designed here, for example, as a shaft with ledges projecting on the circumference. This rotatable attachment promotes a crushing process during the division. The risk of jamming solid parts between a blow bar edge and the impeller and a blockage of the pump is reduced. This is also achieved with the features of claim 6 in that a rotatable or non-rotatable blow bar is resiliently mounted.

An increase in the size reduction effect is also achieved with rotatable blow bars if they are themselves driven by rotation. With the same direction of rotation with the pump wheel, the edges are guided past each other so that the shearing and tearing effect is increased. In a drive with the opposite direction of rotation, the edges run past each other in the same direction, so that a squeezing effect is increased. The rotary drive for a blow bar can be derived from the pump drive by a corresponding gear arrangement, so that no additional motor is required.

Depending on the application, it may be expedient to mount a plurality of blow bars in a basket arrangement according to claim 7 so as to be rotatable about the outer impeller part. Here, too, the basket can be driven in rotation. In principle, similar crushing effects as described above are achieved. In addition, each blow bar can be rotatably supported on the basket.

According to claim 8, a further possibility of adaptation and dimensioning consists in conically and / or cylindrically designing the outer circumference of the screw on the outer impeller part at least in partial areas. The taper can be varied. Cylindrical and conical areas can be combined over the length of the impeller.

The object of the invention is achieved in particular with regard to an improved pump feed with improved delivery with the characterizing features of claim 9.

According to claim 9, the fixed connection between the pump housing and the shaft bearing is made via only one connecting arm offset laterally to the axial direction. As a result, the outer impeller part and thus the pump inlet are largely exposed. The outer impeller part rotates in the area of this connecting arm and at least one impact bar is attached to the connecting arm in the direction of the pump axis.

Due to the outer impeller part, which is largely exposed in the pump medium, with the screw conveyor and the wide-open, almost unhindered access to the pump, use with the pump from the prior art with good function is also possible in wastewater that is much more contaminated with solids. Larger solid parts can also be captured and crushed, the risk of blockage or blockage being significantly reduced. In particular, the pump is also suitable for shredding biological residues in a liquid suspension in connection with recycling in a biogas plant, as well as for agricultural waste water containing high levels of solids, e.g. B. manure heavily mixed with straw, with surprisingly good results.

In an advantageous, concrete embodiment according to claim 10, the pump housing has an upper detachable ring which is connected in one piece to a bearing bush of the shaft bearing via the connecting arm. An easy to manufacture, easy to assemble and maintenance-friendly construction is achieved. A stable attachment of the connecting arm can be easily achieved by welding.

In particular for increasing the rigidity in such a one-armed connection, it is advantageous to make the connecting arm concave, approximately bowl-shaped. The increase in efficiency due to the single-arm structure is still significantly achieved if the outer impeller part through the connecting arm over an angle of less than 60 ° is included. This concave shape can be achieved in terms of production technology in a simple manner according to claim 12 by flat plate parts arranged at an angle to one another, a particularly good function according to claim 13 being achieved when the blow bar is mounted longitudinally approximately in the longitudinal center of the concave shape.

The construction with a connecting arm attached on one side can also be carried out in such a way that the connecting arm consists of several parallel arm parts, with small gaps between these arm parts not influencing the effect.

To improve the shredding function, structuring of the blow bar edge and / or the screw peripheral edge is claimed in claim 15 even in an embodiment with a connecting arm. The structuring can be carried out in accordance with the features of claims 2 to 4. The blow bar arrangement can also be varied here. In particular, a blow bar can be resiliently mounted or driven in rotation, wherein a plurality of blow bars can also be attached to the connecting arm.

Exemplary embodiments of the invention are explained in more detail with further details, features and advantages with the aid of a drawing.

Fig. 1

einen Längsschnitt durch eine erste Ausführungsform einer Pumpe,

Fig. 2a und Fig. 2b

vergrößerte Darstellungen von Kantenstrukturen,

Fig. 3

eine schematisierte Draufsicht auf eine drehbare Schlagleiste,

Fig. 4

eine schematisierte Draufsicht auf eine andere Ausbildung einer drehbaren Schlagleiste,

Fig. 5

eine perspektivische Seitenansicht einer zweiten Ausführungsform einer Pumpe, und

Fig. 6

eine um die Längsachse um 90° verdrehte Ansicht entsprechend Fig. 5.

Show it:

Fig. 1

2 shows a longitudinal section through a first embodiment of a pump,

Fig. 2a and Fig. 2b

enlarged representations of edge structures,

Fig. 3

a schematic plan view of a rotatable blow bar,

Fig. 4

2 shows a schematic top view of another embodiment of a rotatable blow bar,

Fig. 5

a perspective side view of a second embodiment of a pump, and

Fig. 6

a view rotated by 90 ° about the longitudinal axis corresponding to FIG. 5.

In Fig. 1, a pump 1 is shown as a pressure-tear mix pump with a horizontally lying, toroidal pump housing 2, a screw-shaped pump impeller 3, a drivable pump shaft 4 with an upper bearing part 5 and a lower bearing part 6 of a shaft bearing.

The pump impeller 3 projects coaxially into the pump housing 2 with an inner impeller part 7. With an outer impeller part 8, it protrudes upward from the pump housing 2. The pump impeller 3 and, correspondingly, the screw peripheral edge 9 are designed conically tapering towards the top. The pump shaft 4 is firmly connected to the pump impeller 3 for a rotary drive.

A pump outlet connector 10 is formed approximately tangentially on the pump housing 2. The pump housing 2 is also connected to the lower bearing part 6 in a basket-like arrangement via a first bow-shaped connecting arm 11 and a second connecting arm 12. The entire pump 1 thus hangs on the pump tube 13 and can be immersed in a container 14 from above.

One bow-shaped arm 12 (shown in dashed lines) can in principle be omitted if the other arm 11 is dimensioned to be correspondingly strong, as a result of which the outer impeller part 8 is largely exposed.

On the arms 11 and 12, blow bars 15, 16 with blow bar edges 17, 18 are attached to the pump center. These are made of hard metal at least on the outside edge and have a structure which is explained in more detail in connection with FIG. 2a.

A section of a blow bar edge 17 is shown enlarged on the left side of FIG. 2a. There are recesses 19 and / or elevations 20 provided in a rake-like or comb-like edge structure which, depending on the circumstances, can be triangular 21, rectangular 22, semi-circular 23 or irregularly shaped 24 with suitable combinations of shapes.

In the illustrated embodiment according to FIG. 2a, depressions 25 and elevations 26 are also formed on the peripheral edge 9 of the screw in the area of the outer impeller part 8 and are assigned to corresponding structures on the blow bars 15, 16. The depressions 25 and elevations 26 are designed such that they mesh positively in a projection onto the blow bar edges 17, 18 with the structure there to form a gap 27, a shear apparent from FIG. 1 occurring during the passage. In FIG. 2a, in the obliquely hatched right-hand area, the rotating body which is formed when the screw peripheral edge is rotated is indicated in its outer area, from which the positive interlocking with the blow bar edge structure can be seen.

2b shows an alternative embodiment of a structure on the screw peripheral edge 9 which, depending on the circumstances, can mesh with a corresponding blow bar structure or run against another blow bar structure. The structure here consists of elevations 23a with a length up to ten times the depth with lateral roundings, the depth being approximately 5 to 25 mm.

In Fig. 1, the blow bars 15, 16 are immovably attached. In alternative embodiments according to FIGS. 3 and 4, the blow bars are rotatably mounted about a longitudinal axis.

In Fig. 3, a flat blow bar 28 has opposite, blade-shaped blow bar edges 29, 30, both of which contain a correspondingly identical edge structure and mesh with a passing screw peripheral edge (arc 31 shown in broken lines). For this purpose, the blow bar 28 is mounted on a bearing part 32 on both end sides and rotatable about a longitudinal axis 33. In addition, a resilient, radially evasive mounting of the blow bar 28 is shown schematically here by a spring 34.

In an alternative embodiment of a blow bar 35, it is designed as a shaft and is held rotatably about an axis 36 with four blow bar edges 37 offset on the circumference, which also mesh here with a screw peripheral edge (bow 38 shown in broken lines).

The pump 1 shown has the following function:

Materials to be processed, for example biological residues mixed with liquid, are supplied to the pump 1 in the region of the outer impeller part 8 (arrows 39, 40). The materials are captured and the solids contained are pushed past the jagged, sharp edge structure of the blow bars by the helical shape of the impeller and torn and crushed, the edge structure on the screw peripheral edge additionally shearing off and crushing solid parts during the positive passage through the blow bar edge structure. The material to be conveyed is then transported through the impeller screw into the pump housing 2 and from there pushed out through the pump outlet connection 10.

5 and 6, the structure with a toroidal pump housing 2, a pump impeller 3 with an inner impeller part 7 and an outer impeller part 8, a lower bearing part 6 of a shaft bearing, a single one Connection arm 11 and a pump outlet connector 10 can be seen. On the upper part of the pump housing 2, a horizontal ring 44 is attached via screw connections 43, which is connected via the connecting arm 11 to a lower bearing bush 45 of the bearing part 6, the connecting arm 11 being welded on both sides.

The connecting arm 11 is cup-shaped, concave in shape and comprises the outer impeller part 8 at a distance at an angle of approximately 60 °.

The connecting arm 11 is formed from two elongate plate parts 46, 47 which are set at an angle to one another.

In the longitudinal center of the connecting arm 11, where the two plate parts 46, 47 adjoin one another, the longitudinal impact bar 15 (covered by the plate part 46 and thus drawn in by dashed lines) is welded in. The blow bar edge 17 is attached to the peripheral edge 9 of the screw with a slight gap. The screw peripheral edge 9 and the blow bar edge 17 are straight in this embodiment and not structured.

This pump 1 according to FIGS. 5 and 6 basically has the same function as the pump according to FIG. 1, whereby the outer impeller part 8 is largely exposed by the single connecting arm, so that bulky, long solid parts are well grasped and divided.

Claims (15)

Pump, with a toroidal pump housing (2), with a helical pump impeller (3) lying approximately coaxially to the pump housing (2), which projects with an inner impeller part (7) into the pump housing (2) and with an outer impeller part (8) protrudes from the pump housing (2), so that during an impeller rotation, materials that can be detected by the screw shape of the outer impeller (8) are drawn into the impeller opening of the pump housing (2) as a pump inlet and pushed, with an approximately tangential pump outlet (10) on the toroidal pump housing (2), with a drivable pump shaft (4) which is connected coaxially to the outer impeller part (8), with at least one blow bar (15, 16; 28; 35) with a blow bar edge (17, 18; 29, 30) in the bypass area of the peripheral screw edge (9) of the outer impeller part (8) for comminuting solids in materials to be pumped,
characterized, that the blow bar edge (17, 18; 29, 30) and / or the screw peripheral edge (9) has depressions (19; 25) and / or elevations (20; 26) as an obstacle to the comminution of the outer impeller part (8) Solids. Pump according to claim 1, characterized in that the depressions (19; 25) and / or elevations (20; 26) are lined up over the length of the blow bar edge (17, 18; 29, 30) and / or peripheral screw edge (9), so that a serrated, rake-like or comb-like Edge structure is formed, and that the depressions (19; 25) and / or elevations (20; 26) are triangular (21) and / or rectangular (22) and / or semicircular (23) and / or irregular (24) shapes. Pump according to Claim 1 or Claim 2, characterized in that the structure (19, 20) on the blow bar edge (17, 18) corresponds to the structure (25, 26) on the screw peripheral edge (9), in such a way that both structures pass the screw peripheral edge (9) interlock with a gap (27). Pump according to one of claims 1 to 3, characterized in that that the depressions (19; 25) and / or elevations (20; 26) have cutting edges along the edge, and / or that the depressions (19; 25) and / or elevations (20; 26) are made of hard materials, preferably hard metal, or are coated with them. Pump according to one of claims 1 to 4, characterized in that the at least one blow bar (28; 35) is rotatably or possibly rotationally driven about a longitudinal axis (33; 36), and possibly a plurality of blow bar edges (29, 30; 37) offset on the circumference ) having. Pump according to one of claims 1 to 5, characterized in that the blow bar (28) is spring-loaded (34). Pump according to one of Claims 1 to 6, characterized in that a plurality of blow bars are offset on the circumference and are arranged in a blow bar basket which can be rotated coaxially around the outer impeller part and, if appropriate, is driven in rotation. Pump according to one of claims 1 to 7, characterized in that the outer circumference of the screw on the outer impeller part (8) is conical and / or cylindrical at least in some areas. Pump, with a toroidal pump housing (2), with a helical pump impeller (3) lying approximately coaxially to the pump housing (2), which projects with an inner impeller part (7) into the pump housing (2) and with an outer impeller part (8) protrudes from the pump housing (2), so that at materials which can be detected by the rotation of the screw of the outer impeller (8) are drawn and forced into the impeller opening of the pump housing (2) as a pump inlet, with an approximately tangential pump outlet (10) on the toroidal pump housing (2), with at least one blow bar (15), with a blow bar edge (17) in the area of the screw peripheral edge (9) of the outer impeller part (8) for comminuting solids in materials to be pumped, with a drivable pump shaft (4) which is connected coaxially to the outer impeller part (8), and with a shaft bearing (6) of the pump shaft (4), which is arranged at a distance and coaxially to the pump housing (2), the shaft bearing (6) and the pump housing (2) being firmly connected to one another,
characterized, that the fixed connection between the pump housing (2) and the shaft bearing (5) via only one, laterally offset to the axial direction connecting arm (11) is made so that the outer impeller part (8) and the pump inlet are largely exposed, and that in the area of this connecting arm (11) that the outer impeller part (8) rotates and the at least one blow bar (15) is attached to the connecting frame (11) in the direction of the pump axis. Pump according to claim 9, characterized in that the upper part of the pump housing (2) consists of a detachable ring (24) and the shaft bearing (6) has a bearing bush (25), and that the ring (24) and the bearing bush (25) are connected to a component via the connecting arm (11) and the connecting arm (11) is preferred is welded on both sides. Pump according to Claim 9 or Claim 10, characterized in that the connecting arm (11) has a concave shape and encompasses the outer impeller part (8) over an angular range of less than 60 ° and at a distance from the peripheral edge of the screw (9). Pump according to claim 11, characterized in that the concave shape is preferably formed by at least two flat plate parts (26, 27) set at an angle to one another. Pump according to claim 11 or claim 12, characterized in that the blow bar (15) is arranged running longitudinally approximately in the longitudinal center of the concave shape. Pump according to one of Claims 9 to 13, characterized in that the connecting arm (11) attached on one side consists of a plurality of arm parts which are parallel and at short intervals. Pump according to one of claims 9 to 14, characterized in that the blow bar edge (17) and / or the screw peripheral edge (9) has depressions (19; 21) and / or elevations (20; 22) as an obstacle to the comminution of the outer impeller part (8) of solids moving past.

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