Device and method for feeding dilution water into a rotatable drum

Abstract

The invention relates to a rotating drum (2) comprising a feed device (40) for feeding dilution water into the rotating drum (2), to a repulping device comprising a feed device into the rotating drum of the repulping device, and to a method for conveying dilution water into a rotating drum, wherein the feed device (40) has at least one fixed supply line (42) for feeding multiple lines (50) rotating with the rotating drum (2) and the rotating lines (50) are located on an outer face of the rotating drum (2).

Description

[0001] Device and method for feeding dilution water into a rotatable drum

[0002] The invention relates to a device for adding dilution water to a rotatably driven drum, in particular for adding water to dilute a fibrous suspension.

[0003] For processing fibrous materials, especially waste paper, devices for dissolving and sorting, as well as combined devices for dissolving and sorting, are used. During the dissolution of waste paper, in addition to the fiberization of the cardboard and paper raw material, the coarse, non-recyclable components contained within, such as plastics or glass, or other foreign matter, are removed from the process. These foreign matter components are referred to as rejects.

[0004] These devices are used to process fibrous raw materials so that they can be used, for example, in a machine for producing a fibrous web, particularly a paper web, in the form of a fibrous suspension. Typically, the density of the fiber dissolved in the fibrous suspension is 18–24%. After dissolving, the fibrous suspension is sorted by wet sieving to retain foreign impurities due to their size and then separate them. The usable fibers can then pass through the sieve openings as feedstock along with some of the water.

[0005] For improved efficiency, a single-piece drum consisting of a dissolving and a sorting section is preferred. The optimal bulk density for dissolving and sorting differs significantly. Dissolving requires a bulk density of approximately 18-24% by weight, while sorting has proven advantageous with a considerably lower bulk density of less than 12%. Various devices are currently used for supplying dilution water. For example, spray nozzles for diluting the suspension are known, which are mounted outside the sorting drum body. These spray nozzles simultaneously clean the screen surface of contaminants. With external spray nozzles, water can only be supplied gradually along the length of the drum: some of the water does not enter the drum body but flows down the outside, diluting the material without improving sortability.Further dilution of the raw material is often disadvantageous, as high material densities offer advantages in the subsequent process.

[0006] Alternatively, it is also known to inject dilution water axially into the sorting drum from the outlet opening, against the direction of suspension conveyance. However, there is a risk that the dilution water will be carried away by the circulating fiber and thus not reach the front of the sorting drum.

[0007] Due to changes in waste paper composition resulting from a significant increase in the reject rate and recycling rates, a dissolving drum is increasingly used for dissolving and initial coarse sorting of fibrous materials. Sorting drums with a perforated drum body are used for this coarse sorting of the dissolving fibrous material. Dissolving drums are characterized by low maintenance costs, minimal wear, ease of operation, and the ability to separate even difficult-to-dissolve raw materials. Compared to a pulper, contaminants can be more effectively separated from the fibers without grinding them into smaller pieces.

[0008] During the rotation of the drum body, the suspension containing the dissolved fibers is either reflected off the inner surface of the drum body or passes through the perforations and is collected in a receiving container.

[0009] EP 3 892 773 A1 discloses a device for adding dilution water at the end of the dissolving section of a dissolving drum. The device comprises an annular groove arranged around the dissolving section of the dissolving drum, the base of which forms the outer wall of the drum, and two opposing walls of the annular groove projecting outwards along the radial direction of the drum. Several curved tubes extend from the annular groove into the interior of the drum, the radial opening on the inner side of each curved tube oriented against the direction of rotation of the drum. The annular groove is covered by a fixed annular groove cover. A feed line located above and a drain line located below the drum for excess dilution water open into the annular groove cover. Fibers that have entered the annular groove can also be discharged through the drain line.

[0010] The object underlying the invention is to provide a device for adding water to dilute dissolved fibrous materials, particularly for waste paper, with which the dilution of the fibrous suspension after the dissolution process can be carried out efficiently, quickly, reliably, without interference, and in a targeted manner for effective sorting. In particular, it should be possible to reduce the density of the dissolved fibrous suspension to 8-12% over a short transport distance, in order to lengthen the processing path for sorting in the sorting drum or to use a shorter sorting drum.

[0011] The object of the invention is to efficiently and precisely feed dilution water into a rotating sieve drum. In particular, a high proportion of the supplied dilution water should be fed into the sieve drum.

[0012] The problem is solved according to the invention by an embodiment according to the independent claim. Further advantageous embodiments of the present invention are found in the dependent claims.

[0013] The inventive feed device for feeding dilution water into the rotating drum allows a significant quantity of dilution water to be introduced over a short axial length of the rotating drum. This reduces the overall length required for subsequent dilution, which has a positive impact on manufacturing costs, space requirements, and operating costs, particularly for fiber processing equipment with dissolution and sorting capabilities. The feed device has at least one stationary supply line for feeding several lines that rotate with the rotating drum. The rotating lines are located on the outer surface of the rotating drum. Preferably, the rotating lines are located within the area of ​​a closed drum shell. The rotating lines contribute to the stability of the device.This allows the supply of dilution water to be staggered axially from its point of entry into the drum. The dilution water fed into the rotating pipes can be transferred to the rotating drum at a desired position. This allows for greater design flexibility.

[0014] In a preferred embodiment, the rotating lines of the feed device have both an axial and a circumferential extension. Starting from the side facing the feed line, the rotating lines extend circumferentially in the opposite direction to the rotation. This causes the drum movement to cause the dilution water to flow along the lines. This prevents backflow and thus minimizes leakage from the feed device.

[0015] In a preferred embodiment, the rotating pipes are equipped with a funnel. The enlarged opening area of ​​the funnel faces the at least one stationary supply pipe. This allows the dilution water exiting the supply pipe to be collected via the funnel's opening. Preferably, the funnels are arranged in a circumferential line, so that the dilution water supplied through the at least one supply pipe is continuously collected by a rotating funnel during operation, except for the wall separating the funnels.

[0016] In a further embodiment, the at least one supply line is arranged axially in continuation of the rotating lines on the side facing the supply line. This ensures that the dilution water is flushed directly into the rotating lines with kinetic energy, counteracting backflow. This minimizes leakage. Turbulence in the dilution water is also reduced, which further contributes to reducing leakage losses.

[0017] In one embodiment, multiple supply lines are provided and arranged circumferentially. This allows dilution water to be supplied to the rotating lines over a larger circumference. The amount of dilution water supplied per revolution of the rotating drum can thus be increased while maintaining a compact design. Fanning out a single supply line would have the particular disadvantage that the flow direction could not be optimally adjusted.

[0018] In one embodiment, the at least one supply line is arranged laterally to the side of the rotating drum, and the drum rotates upwards on the side of the at least one supply line. This makes it possible to utilize the acting gravitational force. In particular, if the rotating lines are arranged downwards, the dilution water is drawn into the rotating lines due to the rotational force.

[0019] The rotating drum is positioned horizontally or with a downward tilt towards the rear. This tilt facilitates the flow of the suspension within the rotating drum. The tilt is typically in the range of 0° to a maximum of 3°.

[0020] In one embodiment, at least one of the supply lines has an outlet opening pointing towards the rear of the rotating drum. This allows dilution water to be supplied with kinetic energy in the direction of flow of the suspension in the rotating drum, contributing to an improved energy balance. In another embodiment, the rotating lines are arranged in a spiral shape. This spiral shape supports the flow of the supplied dilution water until it enters the rotating drum and minimizes energy losses.

[0021] In one embodiment, rotating lines are arranged radially on the outside of the rotating drum. This arrangement on the radial outside of the rotating drum offers the advantage that the dilution water supply and the area where dilution water is introduced into the rotating drum can be positioned offset from each other. It is also possible to introduce dilution water at different axial heights on the rotating drum.

[0022] The introduction and passage of the dilution water through the drum body is achieved through a small number of drum openings. Preferably, each rotating line is assigned one drum opening. This allows the dilution water to be introduced into the rotating drum with minimized resistance. The drum openings can be arranged axially offset to distribute any weakening of the drum body over a larger area and thus have less of an impact on stability.

[0023] In one embodiment, the dilution water is introduced into the rotating drum through openings in the drum. These openings can be positioned at a distance from highly stressed areas. Such areas can arise, for example, from the drum's bearings. Nevertheless, it is possible to add the dilution water to the suspension even in these highly stressed areas. The dilution water introduced into the drum through the openings can be conveyed to the desired point of addition, for example, by means of axially connected lines. In particular, the openings can be positioned to ensure sufficient distance from a highly stressed area of ​​the rotating drum. Bearing points of the rotating drum, in particular, are often subject to high stress.Especially in the case of a bearing-type bearing ring, the bearing ring area is subject to high stress. The drum through-holes can be arranged in such a way as to minimize weakening of the drum body.

[0024] In one embodiment, the rotating lines transition into axially extending lines within the rotating drum. This makes it possible to decouple the introduction of dilution water from the entry of the dilution water for dilution of the suspension in the drum.

[0025] In one embodiment, the lines run inside the rotating drum within lever bars. This minimizes the design complexity and prevents the lines from interfering with the flow of the suspension in the drum.

[0026] In one embodiment, the feed device ensures that dilution water is always guided axially in the direction of suspension flow through the rotating and axially oriented lines within the drum. This minimizes the energy required for supplying the dilution water.

[0027] In one embodiment, the funnels comprise at least one common ring coaxially surrounding the rotating drum, with lamellae arranged between them. Due to minimal leakage during the dilution water supply, a complex enclosure for the dilution water addition area can be omitted. If necessary, a splash guard with drainage for the small amount of leaked water can be provided. On the side of the stationary supply line, for example, the splash guard can be designed to be open. Alternatively, a coaxially extending, rotating ring can be used to enclose the funnels. Furthermore, an L-shaped ring could be used to form the funnels and the enclosure, further simplifying the design. Such simple designs contribute to reducing manufacturing costs.

[0028] In one embodiment, the supply lines are arranged at an angle of 20° to 60°, preferably an angle (a) of 25° to 45°, with the axis of rotation of the rotating drum towards the rear end of the rotating drum. This downward oblique inflow promotes low leakage and has a positive effect on the flow characteristics during the supply of dilution water.

[0029] The invention relates to a dissolving device with a rotating drum according to one of the preceding embodiments, wherein dilution water for post-dilution is supplied by the feed device upstream of the perforated section of the sorting drum. This allows sorting to be optimized right from the beginning of the perforated zone of the rotating drum. With the feed device according to the invention, effective post-dilution can be achieved over a short axial length, which has a positive effect on the overall length of the dissolving device.

[0030] A method for supplying dilution water to a rotating drum by means of a feed device with a stationary supply line. The stationary supply line temporarily supplies dilution water to lines rotating with the drum at an inlet. The introduced dilution water is drawn away from the inlet into the rotating lines by the rotation and the force of gravity acting within the rotating lines. The dilution water is directed into the rotating drum through designated openings, each axially offset from the at least one supply line, into associated lines. The dilution water flowing in the lines within the drum is fed to the suspension located in the rotating drum at a predetermined axial position. The invention is explained below with reference to the figures. The figures show in detail:

[0031] Fig. 1: Schematic sectional view through a fiber processing device with a feed device. Fig. 2: Schematic view of a fiber processing device with a rotating drum.

[0032] Fig. 3: Feed-in device

[0033] Fig. 4: Illustration of the feed device in the direction of the sorting area from a frontal view in the flow direction of the suspension.

[0034] Fig. 5: Sectional view of the feed device, transition of the dilution water from the supply line into the rotating lines. Fig. 6: Detailed view of the dilution water supply line.

[0035] Figure 2 schematically depicts a fiber preparation device 1 for dissolving and sorting fibers according to the prior art. The fiber preparation device 1 is suitable for dissolving fibers with high densities in the high consistency (HC) range, particularly waste paper with a high reject rate. The fiber preparation device 1 comprises a dissolving drum 10 and a sorting drum 20, which can be designed as a one-piece or two-piece construction.

[0036] The dissolving drum 10 comprises a drum body 12 into which the fiber material, typically in bale form, is fed in an inlet area 14 along with water. The rotation of the dissolving drum 10, in conjunction with internally arranged lifting elements, conveys the fiber suspension upwards, where it then falls back to the bottom of the drum body 12. The resulting mechanical forces on the fiber material dissolve it. The rotating drum body 12 ensures a continuous dissolving process, leading to efficient material utilization and uniform, stable processing of the fiber material. In particular, fleck-free dissolution is possible for high-carbon fibers and difficult-to-dissolve raw materials, which can be further enhanced by carrying out the dissolution process at higher temperatures and / or by adding chemicals.The rotation of the drum body 12 ensures gentle mixing and kneading of the fibrous material, as sufficiently high shear forces are exerted on the components of the fibrous material that still need to be separated in order to dissolve the fibrous material in an energy-efficient manner.

[0037] The sorting drum 20 follows the dissolving drum 10. The sorting drum 20 comprises a perforated drum body 24. Through the perforations, a portion of the fiber suspension fed to the sorting drum 20 from the dissolving drum 10 can exit as good material 102, while another portion of the fiber suspension is retained by the perforations as reject 101. The good material 102 is collected in a collection container.

[0038] The separation of fibers from contaminants continues to occur through the rotation of the perforated drum body 24 in conjunction with internally arranged lifting elements. Early removal of the good material intensifies the treatment of the remaining suspension. This early removal is further facilitated by a significantly reduced suspension concentration compared to the dissolving drum 10. The fiber suspension remaining in the rotating drum 2 is conveyed upwards by the rotation and then falls back to the bottom of the perforated drum body 24. The rotating drum body 24 ensures continuous sorting of the fiber suspension. The fiber suspension is diluted by the feed device 40 before entering the perforated area. The feed device 40 is described in detail below with reference to further figures.

[0039] For efficient sorting of the fiber material in the sorting drum 20, a fiber density of less than 12% to less than 8% in the fiber suspension is required. Only after achieving an acceptable dilution can the fibers pass through the perforations in the drum body 24 as good material 102. Therefore, a high degree of post-dilution after dissolution in a short axial distance is of great importance for the efficiency of the sorting process.

[0040] As can be seen in Fig. 1, the dissolving drum 10, the dilution section 41, and the sorting drum 20 all have the same diameter, which can range from 2.5 to 4.5 m. In a preferred embodiment, the length 11 of the dissolving drum 10 is, for example, 31 m, and the length 21 of the sorting drum 20 is, for example, 12 m. The dilution section 41 is arranged between the dissolving drum 10 and the sorting drum 20. The dilution section 41 has a closed drum body. The dilution water supplied here at the inlet of the post-dilution section by the feed device is mixed with the suspension transferred from the dissolving drum into the dilution section. The flow direction 101 of the suspension is in the axial direction 80. The axis of rotation 82 is horizontal in the illustrated embodiment.The rotating components, such as the funnel 55, the rotating pipes, the drum openings 59, and the axially extending pipes 60 of the feed device 40, are arranged in the area of ​​the dissolving drum 10. The funnels 55 and the rotating pipes 50 are arranged radially outside the rotating dissolving drum 10, as can be seen particularly in Figure 3. The rotating pipes 50 run in a spiral shape and can be held on the dissolving drum 10. In the embodiment shown, the funnels 55 are also mounted on the dissolving drum 10. The dilution water is conveyed through the drum openings 59 into the axially extending pipes 60, which are arranged radially inside the dissolving drum, in the flow direction 100 of the suspension. The axially extending pipes 60 can be formed by lever bars 61 in the drum, or the axially extending pipes 60 can be arranged within the lever bars 61.The lever bars 61 penetrate a baffle 63. The lever bars 61, and if present, the axially extending lines 60, have an opening 62 facing in the direction of flow. The suspension passing through the baffle 63 is immediately mixed with the dilution water. Lever bars 61 may also be provided in the dilution zone 41 to promote mixing. The further diluted suspension passes through an inlet-side baffle 22 upon entering the sorting drum 20 with the perforated drum body 24. The perforated drum body 24 extends over an axial length 21. At the end of the sorting drum 20, the reject 101 exits. The acceptable material passes through the perforation and is collected in a hopper 5 located below the sorting drum. From there, the acceptable material 102 is discharged.

[0041] Figure 1 shows a schematic representation of the rotating drum 2. The rotating drum 2 rotates about the axis of rotation 82, and the flow direction 100 of the suspension is axial 80. In the front section of the dissolution 11 and dilution stages, the drum shell 3 is closed. In this simplified representation, the baffle 13 is shown as an example in the dissolution drum 10. Often, several baffles are provided in the dissolution section 11, so that the flow of the suspension through the baffles is influenced, particularly by the radial height of the baffles. Lever bars are also provided in this section (not shown), which convey the suspension upwards and then downwards. A dilution section 41 adjoins the dissolution section of the rotating drum 2.

[0042] The dilution water is fed from the stationary supply lines 42 into the rotating pipes 50, which are designed as pipe bends. Due to the rotation of the drum and thus the rotating pipes, the dilution water flows further into the pipes. The dilution water passes through the drum opening 59. The drum opening has a significantly larger diameter than the diameter of the perforations. This diameter corresponds approximately to the diameter of the rotating pipes 50 ±10%. Therefore, the flow resistance upon entering the drum is very low.

[0043] The dilution water that has passed through the drum shell 3 flows onward within designated lever bars 60. For this purpose, axially extending lines 60 can be provided in the lever bars 60, or the lever bars 61 themselves can serve as lines. The lever bars 61 transport the water through a baffle 63 located at the end of each lever bar, with this baffle separating the dissolution and dilution zones. The dilution water is then added to the suspension. In the dilution zone, the dilution water mixes with the suspension, and a predetermined dilution can be set by regulating the dilution water supply. This is achieved by supplying the lines 42 with more or less dilution water up to a predetermined maximum quantity.

[0044] The distance between the drum openings 59 in the drum shell 3 and highly stressed zones can be selected based on the length of the water lines in the axial lines 60. For example, a mechanically stressed zone, and thus a highly stressed zone, is located under the running ring 4. This area can be used as a dilution zone. The openings 59 can be spaced apart from this running ring 4. It is also possible to arrange the openings axially offset to reduce weakening of the drum shell 3 in the area of ​​the openings 59. Consequently, the length of the rotating lines 50 outside the drum shell and the axial lines inside the drum wall can vary without affecting the axial position of the dilution water injection point.In the embodiment shown, the distribution of the drum passage openings 59 would be limited to the axial extent of the water-carrying lever bars 61.

[0045] Figures 3 to 6 illustrate a possible embodiment of a feed device. The dilution water is supplied through the stationary supply lines 42 and guided via numerous funnels 55 into hoses as rotating lines 50. The hoses wind around the drum shell. Here, the hoses rest on the drum shell 3 and are arranged there in a spiral pattern. The hoses do not have to withstand any forces and do not need to possess high strength. The previously mentioned funnels 55 are implemented here by an inlet box 58, see especially Figures 3 and 6. The inlet box 58 comprises an axially extending ring 56b that radially surrounds the drum shell 3. On the side facing the supply lines 42, the inlet box has a closing ring 56c, which extends radially and the supply lines 42 are arranged radially between the drum shell 3 and the closing ring 56c.This closing ring 56c prevents dilution water from escaping the inlet area. On the other side of the axially extending ring 56b, another radially extending ring 56a is provided to close off the inlet box 58. This ring extends from the radial outer surface of the drum shell 3 to the axially extending ring 56b. Within the inlet box formed by the rings 56a to 56c, lamellae 57 are arranged to form funnels. These lamellae form the circumferential segments. These circumferential segments constitute the funnels 55. The dilution water flowing into each circumferential segment through the supply lines 42 is fed to the rotating lines, each of which opens into the ring 56a. The inlet box 58 prevents direct feeding of dilution water to the extracted material.Due to the high feed rate of the dilution water, a more precise dilution can be achieved.

[0046] Figure 5 shows an inlet box 58 in an alternative design. Instead of the ring 56a, tapered edges are formed that point towards the rotating pipes. This improves the funnel effect. However, this design is also more complex and therefore more expensive.

[0047] The funnels 55 are extended on one side as guide vanes to direct free water in the inlet box 58 towards the inlet 51 of the rotating pipes 50. The design of the inlet box 58, the cross-section / number / length of the rotating pipes 50, and the inclination α and the wrap angle β have a significant influence on the maximum flow rate of water that can be supplied without overflow in the area of ​​the inlet box 58. The wrap angle β is approximately 100° in the illustrated embodiment, Fig. 4.

[0048] Separating the dilution water supply allows for more targeted cleaning of the perforated drum shell, and the nozzles can be optimized solely for this function. This also enables further optimization of water consumption. Furthermore, it would now be possible to use a different cleaning method for the perforated screen shell, for example, with compressed air or mechanically, thus completely preventing dilution of the recovered material. Reference list

[0049] 1 Dissolving device I Fiber processing device 2 Rotating drum

[0050] 3 Drum shell

[0051] 4 running ring

[0052] 5 tubs of good stuff

[0053] 10 Dissolving drum

[0054] 11 Resolution range

[0055] 12 drum bodies

[0056] 13 bulkhead

[0057] 14 Entrance area

[0058] 16

[0059] 20 sorting drums

[0060] 21 Length of the perforated drum body

[0061] 22 Partition wall in front of the sorting drum entry

[0062] 24 perforated drum bodies

[0063] 40 Feed device (post-dilution)

[0064] 41 Dilution range

[0065] 42 Fixed supply line

[0066] 44 Outlet opening

[0067] 50 Rotating Lines

[0068] 51 admissions out of 50

[0069] 52 Axial extent of 50

[0070] 53 Axial continuation

[0071] 54 Extension in the circumferential direction of 50

[0072] 55 Funnel Ring

[0073] slats

[0074] Inlet box

[0075] Drum passage opening

[0076] Axially running cables inside the drum, lever bars

[0077] Lever bar opening pointing in the direction of flow

[0078] Axial direction

[0079] axis of rotation

[0080] Circumferential direction

[0081] Direction of rotation

[0082] Flow direction of suspension

[0083] Reject

[0084] Good substance

Claims

Patent claims 1. Rotating drum (2) with a feed device (40) for feeding dilution water into the rotating drum (2), preferably at the end of a dissolution area of ​​the drum, wherein the feed device (40) comprises at least one stationary supply line (42) for supplying several lines (50) rotating with the rotating drum (2), characterized in that the rotating lines (50) are arranged on an outside of the rotating drum (2).

2. Rotating drum (2) according to claim 1, characterized in that the rotating lines (50) of the feed device (40) have an axial extension (52) and an extension in the circumferential direction (54) and rotate with the drum (2) and wherein the rotating lines (50) have a circumferential course in the opposite direction to the direction of rotation (86) starting from the side facing the feed line (42) in the circumferential direction (84).

3. Rotating drum (2) according to claim 1, characterized in that the rotating lines (50) are provided with a funnel (55) on the side facing the supply line (42).

4. Rotating drum (2) according to claim 1, characterized in that the at least one supply line (42) is arranged in axial extension (53) to the rotating lines (50).

5. Rotating drum (2) according to claim 1 or 2, characterized in that several supply lines (42) are provided and the supply lines (42) are arranged distributed in the circumferential direction (84).

6. Rotating drum (2) according to any one of the preceding claims, characterized in that the at least one supply line (42) is arranged laterally to the is arranged in a rotating drum (2) and the drum (2) rotates upwards on the side of the at least one supply line (42).

7. Rotating drum (2) according to one of the preceding claims, characterized in that the at least one supply line (42) has an outlet opening (44) pointing towards the rear end of the rotating drum (2).

8. Rotating drum according to one of the preceding claims, characterized in that the rotating lines (50) are arranged in a spiral shape.

9. Rotating drum according to one of the preceding claims, characterized in that the rotating lines (50) transition into axially extending lines (60) within the rotating drum (2).

10. Rotating drum according to one of the preceding claims, characterized in that the lines (60) run inside the rotating drum (2) within lever bars (61).

11. Rotating drum according to one of the preceding claims, characterized in that dilution water is always guided axially in the flow direction (100) of the suspension by the feed device (40) in the rotating lines (42) and the axially extending lines (60) within the drum (2).

12. Rotating drum according to one of the preceding claims, characterized in that the funnels (55) comprise at least one common ring (56) coaxially surrounding the rotating drum with lamellae (54) arranged between them.

13. Rotating drum according to one of the preceding claims, characterized in that the supply lines (42) are connected at an angle of 20° to 60°, preferably an angle (a) of 25° to 45°, to the enclose the axis of rotation (82) of the rotating drum (2) towards the rear end of the rotating drum (2).

14. Rotating drum according to one of the preceding claims, characterized in that the dilution water is introduced into the rotating drum through drum passage openings (59), wherein the drum passage openings (59) are arranged spaced apart from the point of entry into the suspension.

15. Dissolving device (1) with a rotating drum (2) according to one of the preceding claims, characterized in that dilution water for post-dilution is supplied by the feed device (40) in front of the perforated section of the sorting drum (5).

16. Method for supplying dilution water to a rotating drum (2) by means of a feed device (40) with a stationary supply line (42) through the lines (50) rotating with the drum (2) temporarily supplied with dilution water at an inlet (51) and that the dilution water introduced into the rotating lines (50) is carried away from the inlet by the rotation and the acting gravitational force in the rotating lines (50) and that the dilution water flows through each provided drum passage opening axially offset to the at least one supply line (42) into associated lines (60) in the rotating drum (2) in order to then be supplied at a predetermined axial position to the suspension located in the rotating drum (2).

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