Rotor for use in stock preparation

Abstract

The invention relates to rotating rotors, impellers and propellers, hereinbelow referred to as rotors (21), for use in a stock preparation plant (1). The rotors are partly or wholly provided with functional surfaces (41). The functional surfaces are elevations and depressions having dimensions of 0.15 mm to 5 mm from a peak to the trough. The functional surfaces improve the quality of the fiber suspension. • - Fiberization is improved with regard to paper particles and specks. • - The paper suspension is homogenized. • - Any slight fiber entanglements are treated. • - Linear particles are comminuted until undetectable. - The fibers are slightly fibrillated, thus contributing to an increase in strength of the paper. • - The paper fibers are cleaned and the cleaned fibers contribute to an increase in paper strengths. • - Hornified fibers are partially treated to reactivate the hornified OH groups. The activation of the OH groups contributes to an increase in strength of the paper. • - The increase in strength due to the treated paper fibers makes it possible to economize on chemicals.

Description

[0001] The invention relates to various types of rotors for use in a stock preparation system according to the preamble of patent claim 1.

[0002] For example, a rotor is used in a pulper. The pulper is filled with warm return water, and the rotor in the pulper sets the water in rotation. Paper is added in bales or loose. The paper is wetted by the water. The rotor creates a current that draws the paper into the area of the rotor. The rotor roughly shreds the paper. Once the paper particles reach a certain size, the efficiency of the rotor decreases. Further disintegration occurs through impact in the area of the screen plate openings. The efficiency also decreases as the paper particles become smaller. Subsequently, further disintegration only occurs in the moving material through material friction. This disintegration through material friction is often very ineffective, time-consuming, or associated with a relatively high energy consumption.Depending on the raw material and the condition of the pulping elements, rotor, and screen plate, paper particles ranging in size from 1x1 mm 2 to 5x5 mm 2 and specks are usually still present in the accept, also known as the accept pulp. The accept pulps and fibers are further pulped and shredded in a subsequent secondary pulper. Most of the specks and paper particles are removed. However, the remaining paper particles and specks are removed as rejects during the subsequent screening process and represent fiber losses.

[0003] In addition, remaining long fibers in the suspension often appear entangled. This means that fiber clouds are cross-linked by the long fibers. Foreign particles may also be trapped within these fiber clouds, making it difficult to separate them from the fiber suspension.

[0004] US Pat. No. 3,163,368 discloses a pulper with stationary blades. The blades are arranged radially coaxially with the rotor and have a ribbed surface on both sides.

[0005] DE 26919247 U1 discloses a pulper with stationary impact elements located near the rotor. The rotor comprises at least one helix. The helix has an adjusting section A and a section B that is not part of the adjusting section. The adjusting section A is arranged at an angle to the section B.

[0006] WO 2012 / 116928 discloses a rotor for a pulper in a fiber processing plant. The rotor is arranged to circulate a fiber suspension contained in a container. The rotor sweeps over a sieve surface of the container. The rotor is formed by a rotor head, with several rotor blades attached to the outer circumference of the rotor head.

[0007] The invention was based on the object of improving the quality of the fiber suspension produced in each process step. In particular, the invention was based on the object of producing a more uniform fiber suspension and increasing the proportion of free, isolated fibers.

[0008] The invention is solved by the features of independent claims 1 and 13. Further advantageous features are mentioned in the dependent claims.

[0009] The rotor according to the invention with functional surfaces makes it possible to achieve an improved fiber suspension in a fiber processing plant.

[0010] By providing the rotor according to the invention in a fiber processing plant, it is also possible to subsequently improve the efficiency of a fiber processing plant. Functional surfaces are understood to be surfaces with a rough surface. The functional surfaces preferably have a total height of a roughness profile R t in the range of 0.15 mm to 5 mm. The total height of a roughness profile can be measured, for example, using a Parthometer S3P surface measuring device. A measuring length of 10 times the total height of the roughness profile has proven to be suitable. With a total height of the roughness profile of more than 4 mm, the total height of the roughness profile can preferably be determined by an impression.

[0011] Locally generated vortices cause specks and / or paper particles to slide along the functional surfaces. The specks or paper particles are subjected to friction and / or shear forces and are broken down into individual fibers. The functional surfaces are located on the surfaces facing away from the preferred direction. This ensures gentle processing of the passing components. High energy input is avoided, and wear of the functional surfaces is kept to a minimum. A key feature is that the functional surface is located on the side facing away from the flow and is therefore less exposed to wear. Also to keep energy consumption low, no functional surfaces are provided on the inflow surface. The inflow surface has a lower roughness than the functional surface.

[0012] In a preferred embodiment, the functional surface is a structured surface with structures, in particular regular structures, of at least 0.15 mm, preferably 1.5 mm, height measured perpendicular to the surface normal of the area spanned by the minimal points. This surface structure can be measured using electron microscopy. This height difference has proven advantageous for interacting with passing paper particles. In particular, paper particles or specks can become caught in the structures and then be gently broken down into individual fibers by the shear forces generated by the suspension continuing to flow past the structure. The flowing suspension also rinses the functional surface and prevents clogging of the surface structure.Therefore, the functional surface structure must be selected so that, depending on the suspension used in the processing process, clogging of the surface structure does not occur. Clogging of the surface occurs when a fiber mat forms on the functional surface, thereby impairing its functionality.

[0013] In a further embodiment, the functional surface is a rough surface, i.e., a surface with an aperiodic structure, with a height extension of 0.15 mm to 5 mm. This allows for suitable processing of fiber composites (paper parts / specks).

[0014] In one embodiment, the functional surface is arranged on one of the rear surfaces relative to the preferred direction of the rotor blade. This prevents the functional surface from being exposed to the main flow of the suspension. This leads to less wear compared to positioning it on the surface of the rotor exposed to the flow.

[0015] In a preferred application, the rotor with functional surfaces is intended for use in a pulper. This can further increase the efficiency of the pulper. The functional surfaces can be used to break up specks and flakes through interaction with functional surfaces. It has proven advantageous to provide functional surfaces on the surface of the rotor blades that is not directly exposed to the flow. Particularly in areas where turbulent flow develops during operation, the provision of functional surfaces has proven effective for gentle processing of the fiber composites. Different remote surfaces of the rotor blades can be provided with different functional surfaces.For example, a functional surface located almost parallel to the screen on the side of the rotor blade facing away from the screen can have a different structure than a surface located on a side of the rotor blade facing away from the preferred direction, with a component perpendicular to the screen. Pressing in the paper particles and specks stresses the specks and paper particles beyond their strength and causes them to disintegrate into individual fibers. Repeated interaction with a functional surface may also be necessary to achieve a release and loosening of the fiber composites.

[0016] In one embodiment, a functional surface is arranged circumferentially between the rotor blades on the rotor shaft. These functional surfaces can be provided in addition to or as the only functional surfaces.

[0017] In particular, it has proven advantageous that the functional surface on the rotor shaft is arranged adjacent to the side of the rotor facing away from the preferred direction and extends only over a partial area in the circumferential direction. This makes it possible to vary the functional surface in the surface areas depending on the application. This results in an effect suitable for improving fiber suspension.

[0018] It has proven advantageous to also apply functional surfaces to propeller heads of agitators.

[0019] Functional surfaces on agitators ensure gentle fibrillation of the fibers. This improves paper strength without damaging the fibers. Cornified fiber surfaces are reactivated. The functional surfaces are so fine that no spinning occurs and no sliver fragmentation occurs. However, the flow intensity is high enough that the functional surfaces are always self-cleaning, preventing deposits from forming.

[0020] In general, and not specific to specific machines, functional surfaces contribute to the cleaning of paper fibers. Just as fibers can be dyed, even the smallest dirt particles can adhere to the free OH groups. Paper strength decreases because the OH groups of the fibers are already covered by dirt. The functional surfaces treat and clean the fibers like a washboard. This results in an increase in free OH groups, which contribute to paper strength. This reduces the need for additives.

[0021] In one embodiment, particularly in a rotor for a pressure screening device, the at least one functional surface is provided on one of the rotor blades, preferably all of the rotor blades, in an outflow area. The functional surface comprises a maximum area of 50% of the respective area. Turbulent flows preferably form in such outflow areas, which promotes interaction with the functional surface.

[0022] It has proven advantageous for the rotor blade to be designed radially outward with flow surfaces running in the circumferential direction and for functional surfaces to be formed as a surface area. This functional surface is formed with an axial extension at the end of the flow surface facing away from the preferred direction. Advantages also arise if the rotor blade is designed radially inward with flow surfaces running in the circumferential direction and for functional surfaces to be formed as a surface area. Functional surface areas can also be provided inside and outside.

[0023] The preferred use of the rotor has been found to be in a screening device for removing a fiber mat forming on the screen.

[0024] The inventive method for operating the rotor according to one of the preceding claims is characterized in that fibers of a fiber suspension are accelerated by the rotary movement of the rotor. The fibers initially interact with the surfaces of the rotor blades facing the preferred direction and are accelerated. Subsequently, in a region facing away from the preferred direction, a portion of the fiber suspension moved by the rotor flows past the at least one functional surface of the rotor and is further dissolved, de-flaked, or defibrillated by interaction with the functional surface. This additional treatment represents a particularly gentle processing.

[0025] Further advantageous features of the invention are explained using exemplary embodiments with reference to the drawings. Fig. 1schematic representation of a fiber processing plant in the form of a screening device Fig. 2: Rotor for a pulper Fig. 3: Orbiting propeller for a pumping device Fig. 4 a + b: flat screen rotor Fig. 5 to Fig. 16: various designs of functional surfaces

[0026] In Figure 11 shows a screening device 9 of a fiber processing plant 1. The embodiment shown is a pressure screen. This screening device 9 has a suspension feed 3 and an accepts discharge 5 and a rejects discharge 7. A screen 11 designed as a screen basket is arranged vertically. Alternatively, not shown, the screen could also be arranged horizontally. A rotor 21 is arranged on the side of the screen basket facing the suspension feed. Here, the rotor 21 is arranged radially inside the screen basket. The rotor 21 comprises a drivable rotor shaft 25. Rotor blades 23 are firmly connected to the rotor shaft 25. These rotor blades 23 are arranged at a distance in the radial direction from the rotor shaft 25. Fibers and impurities located on the screen 11 are removed from the screen 11 by these rotor blades 23.For this purpose, the rotor blades 23 are arranged vertically at a radial distance from the screen 11 and rotate in front of the screen during operation. The rotor blades 23 have an inflow region 31 pointing in the direction of rotation and an outflow region 39 at the end 29 of the rotor blade 23 in relation to the circumferential direction 33. This outflow region 39 is provided with a functional surface 41. During operation, fiber suspension is fed to the screening device 9. A negative pressure prevailing on the accept side accelerates the suspension towards the screen 11. Suspension containing fibers passes through the screen 11. The components of the suspension retained by the screen 11 are removed from the screen by the rotor blades rotating past the screen. The accept that has passed through the screen is discharged through the accept discharge. Impurities fall out of the bottom of the screening device 9 and are discharged through a reject discharge 7.

[0027] In the outflow region 39, the radial distance to the sieve 11 is increasingly greater and a turbulent flow can develop. As a result, the components of the suspension detached from the sieve 11 are subjected to gentle processing by the functional surface 41 provided in this region. Fiber composites can be dissolved. By dissolving the fiber composites, thickening in the sorting device 9, also referred to as a pressure sorter, can be reduced. The efficiency of the sorting device 9 is increased. Due to the position of the functional surface 41, wear on the functional surface 41 is low and the associated energy consumption is also low. For such sorting devices 9, fine functional surfaces have proven to be particularly suitable. Fine functional surfaces are surfaces with a total height of a roughness profile R t of 0.15 to 1.5 mm.Wear requiring reconditioning of the functional surface 41 is to be expected at the same intervals as the necessary reconditioning of the rotor.

[0028] In Figure 2a rotor 27 intended for a pulper is shown. Such rotors 27 are designed for mixing the components in pulpers. The pulper is filled with warm return water. The rotor 27 in the pulper sets the added water in rotation. Paper is added in bales or loose. The paper is wetted by the water. The rotor 27 draws the paper into the area of the rotor 27, where the added paper is roughly shredded. From a certain size of the paper particles, the efficiency of the rotor 27 decreases. Further disintegration of the paper now takes place through impact effects at the screen plate openings of the pulper. But here too, the efficiency decreases as the paper particles become smaller. Now further disintegration only takes place in the moving material due to material friction. However, this type of disintegration is very ineffective depending on the raw material.During the emptying process, depending on the raw material and the condition of the pulping elements, paper particles measuring between 1x1 and 5x5 mm and specks may still be present in the accepted material. With the rotor 27 shown here, the proportion of paper particles is significantly reduced.

[0029] The rotor blades 23 are connected to the rotor shaft 25. The rotor blades 23 have an inflow surface 31 facing the direction of rotation. A functional surface 41 is provided on the rear surface of each rotor blade 23. This surface is arranged away from the preferred direction 33. This means that the surface is arranged on the blade 23 of the rotor 21 opposite to the direction of rotation. This achieves better resolution of paper particles and specks on all paper types.

[0030] By pressing specks and paper particles into the surface structure of the functional surface 41, 41', the specks and paper particles are stressed and disintegrate into individual fibers. Paper particles are broken down into specks and specks into fibers. The fibers are released from the fiber composite at the many small impact surfaces of the functional surface 41. Even if the corners and edges of the functional surfaces are rounded, a shearing effect of the functional surface 41 remains. The suspension flowing past the functional surface 41, 41 experiences a shearing force due to flow paths of varying lengths. Small ink particles and paint particles can also be shredded on the functional surfaces 41, 41'. Dirt spots are no longer visually recognizable or are only partially recognizable.Due to the low flow intensity on the opposite sides of the rotor blades 23, plastic particles are not shredded by a functional surface and can be discharged as contaminants. For a rotor intended for a pulper, functional surfaces with a total roughness profile height in the range of 1 to 3 mm are particularly suitable.

[0031] In Figure 3A propeller 51 that can be used as a pump wheel is shown as the rotor 21. Such pump wheels can be used in pumps for pumping fiber suspension. The rotor 21 is also referred to as a propeller 51 and has a rotor shaft 25. Radially extending rotor blades 23 are connected to the rotor shaft 25. Functional surfaces 41, 41' are provided in the circumferential direction between the rotor blades 23 and also on the opposite surface of the rotor blade. Different functional surfaces 41 and 41' can be provided on the opposite surface of the rotor blades and on the rotor shaft 25 between the blades. Functional surfaces 41 can also be provided only on the rotor blades 23 or functional surfaces only on the shaft 41'.

[0032] On propellers 51 on agitators, functional surfaces 41 are mounted opposite the conveying propeller blade side.

[0033] Functional surfaces 41, 41' on propellers cause gentle, minimal fibrillation of the fibers. This improves paper strength without damaging the fibers. Cornified fiber surfaces are reactivated. The functional surfaces 41, 41' are so fine that no spinning occurs and no sliver shredding occurs. However, the flow intensity is sufficient that the functional surfaces 41, 41' are always self-cleaning, preventing deposits from forming.

[0034] A functional surface is any surface structure that exhibits a height / depth difference of greater than 0.15 mm. The height / depth difference can be determined using suitable measuring instruments depending on the depth difference. The functional surface 41, 41' can consist of grooves, ridges, holes, and elevations of any shape. Figures 4 to 9 different functional surfaces 41, 41 'are shown.

[0035] In Figure 4 A rotor for a flat screen is shown. The rotor is provided with a functional surface with a rib structure 61.

[0036] In the Figures 7 , 10 , 11 , 13 to 16 are functional surfaces with a periodic or almost, Fig. 5 , periodic structure. In the Figures 6 , 8 , 9 and 12 Aperiodic functional surfaces are shown. As these examples clearly show, the functional surfaces can have very different structures. The structure used depends heavily on the intended application and the expected suspension qualities.

[0037] In Figure 8 A particularly fine functional surface is shown. This surface has an aperiodic structure and a height-to-depth ratio of 0.15 mm. List of reference symbols

[0038] 1 Fiber processing plant 3 Suspension supply 5 Acceptance removal 7 Reject removal 9 screening device 11 Sieve 21 rotor 23 rotor blades 25 rotor shaft 27 Rotor for pulper 29 End of rotor blade 31 Inflow area 33 Preferred direction / direction of rotation 34 circumferential direction 35 Facing surface 36 Radial direction 37 Back surface 38 Axial direction 39 Outflow area 40 Flow area 41 Functional surface / functional surface area 41' Functional interface 43 Regular structure 45 Aperiodic structure 47 increase 51 propeller

Claims

1. Rotor (21) for use in a fibre stock preparation system (1), wherein the rotor (21) comprises a rotor shaft (25) and at least one rotor blade (23) extending radially from the rotor shaft (25) for moving a fibre stock suspension and the rotor (21) is configured for rotary drive in a preferred direction (33), wherein the rotor blade (23) has inflow surfaces (31) oriented to accelerate the fibre suspension in the preferred direction, characterized in that the rotor (21) is provided, at least in part, with a functional surface (41) on at least one surface (35) facing away from the preferred direction, wherein the functional surface is a rough surface and wherein the inflow surface has a lower roughness than the functional surface.

2. Rotor (21) according to Claim 1, characterized in that the functional surface (41) is a regularly structured surface, with structures, with a total height of the roughness profile Rt of at least 0.15 mm.

3. Rotor (21) according to Claim 1, characterized in that the functional surface (41) is an aperiodically structured surface with a total height of the roughness profile Rt ranging from 0.15 mm to 5 mm.

4. Rotor (21) according to any one of the preceding claims, characterized in that the functional surface (41) is formed on a rear surface (37) of the rotor blade (23) facing away from the preferred direction (33).

5. Rotor (21) according to Claim 4, characterized in that the rotor (23) is provided for use in a flat screen machine, such as a pulper or a disc screen sorter or a vertical sorter.

6. Rotor (21) according to any one of the preceding claims, characterized in that the functional surface (41) is arranged in the circumferential direction (34) between the rotor blades (23) on the rotor shaft (25).

7. Rotor (21) according to Claim 6, characterized in that the functional surface (41) on the rotor shaft (25) is arranged adjacent to the surface (35) of the rotor blade (23) facing away from the preferred direction (33) and extends in the circumferential direction (34) only over a partial region of the area between the rotor blades.

8. Rotor (21) according to Claim 6 or 7, characterized in that the rotor (21) is a propeller (51) with a propeller head serving as the rotor shaft (25) for circulating the fibre suspension.

9. Rotor (21) according to any one of the preceding claims, characterized in that the functional surface (41) is provided in an outflow region (39) of the rotor blade (23), wherein the functional surface (41) can vary in terms of extent.

10. Rotor (21) according to any one of the preceding claims, characterized in that the rotor blade (23) is formed with flow surfaces extending in the circumferential direction (34) on the radially outer side and at least one surface region with a functional surface (41) is formed at the end of the flow surface facing away from the preferred direction (33) and extends in the axial direction (38).

11. Rotor (21) according to any one of Claims 9 or 10, characterized in that the rotor (21) is provided for use in a screen device (9) for detaching a fibre mat that forms on the screen (11).

12. Rotor (21) according to any one of the preceding claims, characterized in that the functional surface (41) is formed in a turbulent flow region during operation of the rotor (21).

13. Method for operating the rotor (21) according to any one of the preceding claims, wherein a suspension with fibres is accelerated by the rotational movement of the rotor (21), whereby the suspension first interacts with the surfaces of the rotor blades (23) facing the preferred direction (33) and is accelerated and subsequently, in a region facing away from the preferred direction (33), part of the suspension moved by the rotor (23) flows past the functional surfaces of the rotor (23), wherein fibre bundles contained in the suspension are disintegrated or cleaned of specks through interaction with the functional surface.

14. Method according to claim 13, characterized in that the drive energy additionally required to operate the rotor compared with a rotor without functional surfaces is increased, wherein the additional drive energy is increased by a maximum of 10% compared with a rotor without functional surfaces.

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