Hydrocyclone for cleaning a fibre suspension

Abstract

The invention relates to a separation cone for a hydrocyclone and to a hydrocyclone. The separation cone has an upper open end for receiving suspension and a lower open end for removing a heavy-part reject. The lower open end has a smaller diameter than the upper open end. The lower open end can be connected to a lower outlet (11) of a hydrocyclone. The separation cone is provided with a wear indicator (31) which extends axially at least over a partial section of the separation cone for detecting the wall thickness of the separation cone by reflecting radiation.

Description

[0001] Hydrocyclone for cleaning a fiber suspension

[0002] The invention relates to a hydrocyclone for cleaning a fiber suspension. The hydrocyclone has an inlet at an upper end and a contaminant discharge at a lower end.

[0003] Hydrocyclones, known as heavy particle cleaners, are used to separate heavy particles in the range of 0.1–3 mm from the fiber suspension. Heavy particles have a greater density than water and therefore do not float. Heavy particles with a density of 2 grams / cm3 or higher 3 and a size of 0.1 mm in diameter are easily separated by a hydrocyclone. The smaller the heavy particles and the smaller the density difference to water, the more difficult they are to separate in a hydrocyclone.

[0004] Heavy particles are also referred to as impurities. However, in addition to heavy particles, there are also light particles, which are also referred to as impurities. Such heavy particles have a detrimental effect on the papermaking process. In the following, the term "impurities" refers only to heavy particles.

[0005] Especially in waste paper processing, a wide variety of heavy particles can be present in the fiber suspension. Hydrocyclones are designed to separate heavy particles, which are considered impurities in the range of 0.1-3 mm, from the fiber suspension, preventing their harmful effects on the papermaking process.

[0006] Especially in waste paper processing, a wide variety of heavy particles can be present in the fiber suspension. Examples include sand, glass splinters, tiny metal particles, metal dust, heavy plastics, rubber particles, silicone particles, soot, bone splinters, rust particles, and paint splinters.

[0007] The separation of heavy particles from the fiber suspension works via centrifugal forces. The centrifugal forces act on the introduced fiber suspension in the hydrocyclone. To generate the centrifugal forces, the fiber suspension is introduced into the hydrocyclone under pressure tangentially at the inlet nozzle of the headpiece. The inlet diameter narrows to a nozzle. The lower the inlet consistency, the better the separation efficiency. In the nozzle, the inlet pressure is converted into flow velocity. This tears open the fiber network downstream of the nozzle, and heavy particles can be released from the fiber network. The heavy particles react to centrifugal forces and are pressed against the walls of the hydrocyclone.

[0008] Due to the spiral in the headpiece, a spiral flow forms along the wall of the hydrocyclone. The flow is directed downwards in a spiral fashion into the separation cone. In the separation cone, the heavy particles are concentrated and discharged as reject along with a portion of fibers.

[0009] Due to the concentration and abrasive action of the heavy particles in the separator cone, wear occurs on the inner surface. This abrasion can lead to complete wear through the separator cone. In the worst case, this can cause a leak.

[0010] The use of particularly abrasion-resistant materials, such as ceramic, is particularly costly. In addition, such materials are often very fragile and carry the risk of cracking during assembly and processing.

[0011] A hydrocyclone for cleaning a fiber suspension is known from US 2009 / 0025899. Measures are proposed which make it possible to easily determine whether a breakthrough has occurred in the housing. Furthermore, the housing wall can be easily checked to see whether it is still sufficiently thick so that there is no risk of breakthrough. If the thickness of the housing wall is so small due to abrasion that there is a risk of breakthrough, the housing or a housing part must be replaced. This is achieved by manufacturing at least the lower housing part or a casing surrounding it from a transparent or translucent material, in particular from a transparent or translucent plastic material. Due to the transparency or translucency of the casing, it is always clear whether a breakthrough has occurred.Due to the transparency of the housing wall or housing components, their thickness can be determined by occasional inspection. Using a transparent sheath makes it clear when a break has already occurred. The worn part must then be replaced. However, the sheathed version is more costly due to the additional sheathing.

[0012] Hydrocyclones are known in the art that have compartments outside the separation chamber, with any leakage flowing into these outer compartments rather than exiting the hydrocyclone. The outer compartments can fill with suspension, and operation can even continue, as described in DE 29 46 157.

[0013] DE 31 19 663 describes a hydrocyclone with an outer chamber that covers a weakened portion of the hydrocyclone. This weakened portion provides a predetermined breaking point to facilitate locating and repairing a break.

[0014] EP 429 919 discloses a hydrocyclone for separating abrasive contaminants from a liquid. The hydrocyclone comprises a substantially conical separation chamber with an outer wall, which is subject to wear on its inner surface due to the abrasive contaminants, and wherein the hydrocyclone is provided with a section of reduced wall thickness. This section of reduced wall thickness is intended for the formation of wear openings to facilitate localization of wear. The wear openings are arranged vertically on one side of the hydrocyclone. To seal a leak located in this way, the wear openings in the outer surface of the outer wall are formed such that a sealing member for closing the wear opening can be held by the wear opening. The leak can be stopped by using a sealing device.

[0015] WO 2019 / 180549 discloses a hydrocyclone with a replaceable inner coating. The thickness of the coating is measured by an ultrasonic sensor. If no section of the inner coating has a thickness that exceeds a predetermined limit, a service signal is issued via the control unit.

[0016] The invention is based on the object of improving the operational reliability of hydrocyclones used as heavy particle cleaners.

[0017] The object is achieved by a separation cone for a hydrocyclone having the features according to claim 1 and by a hydrocyclone according to claim 10 and a method for operating the hydrocyclone according to claim 13.

[0018] Further advantageous features are mentioned in the dependent claims.

[0019] The invention is characterized in that the separator cone is provided with a wear indicator extending axially over at least a portion of the separator cone for detecting the wall thickness of the separator cone by reflecting radiation. In particular, the inner contour of the separator cone can be detected by reflecting radiation. This allows wear of the separator cone to be detected. Maintenance can be scheduled early, thus preventing leakage.

[0020] By measuring wear, it becomes possible to use even more easily worn materials, such as plastics. This can have a positive impact on manufacturing costs. The separator cone can also be used and replaced as a spare part, making it easy to retrofit hydrocyclones with a wear indicator. The separator cone tapers in the direction of its axial extension. Hydrocyclones with separator cones can be arranged both vertically and horizontally.

[0021] In a preferred embodiment, the wear indicator comprises a marking. The marking makes it easier to determine the wall thickness. In particular, it has proven advantageous to determine the wall thickness as a function of the marking itself or an image of the marking. The marking is arranged on the outer surface of the separation cone. Thus, the marking of the wear indicator itself is not subject to wear. It has proven advantageous to capture an image of the marking in reflection. This allows a contour of the inner surface of the separation cone to be captured. Such a wear indicator reliably and easily provides an indication of wear by detecting the wall thickness.

[0022] In one embodiment, the separation cone is at least partially transparent. This makes it particularly easy to determine the wall thickness by capturing an image of the marking, e.g. a mirror image or shadow image. This simple method of determination is a particularly cost-effective solution. Detection by the human eye is even possible, which is a particularly advantageous variant. Furthermore, it is also possible to view the flow in the separation cone, which has a beneficial effect on detecting and preventing malfunctions. In advantageous embodiments, a radiation source can be provided, the radiation being reflected on the inner surface of the separation cone. A sensor can be provided to record the reflected radiation. This enables a particularly precise image to be obtained.Pulsed or timed irradiation is also possible, making it possible to specifically minimize interference signals. Colored markings have proven particularly advantageous for this purpose. Contrasting colors compared to the color of the suspension have proven particularly suitable. Signal colors, such as red, are particularly effective. A partially transparent red marking forms a mirror image that is easily recognizable to the human eye.

[0023] It has proven advantageous to provide the wear indicator marking on the outer surface of the separator cone. This allows for subsequent marking. Furthermore, the marking is protected from abrasion and wear. This makes retrofitting or installing a wear indicator as needed particularly simple and cost-effective.

[0024] It has proven advantageous to provide multiple marking elements to enable spatially distributed wear detection. In particular, it has been shown that wear can occur very locally. Even if only one vertically arranged marking is provided, leakage can still occur if wear occurs more frequently in one area, particularly in a limited circumferential area, due to inflow and contaminants.

[0025] In one embodiment, a plurality of markings are provided at different vertical heights of the separation cone in order to detect wear at different heights.

[0026] It may be provided that a separation cone made of at least partially transparent plastic has proven particularly cost-effective. This has a beneficial effect on both manufacturing and maintenance costs. Furthermore, inspection with the human eye may be possible, depending on the lighting conditions. By replacing conventional separation cones with one of the inventive separation cones, retrofitting can be carried out during maintenance.

[0027] For remote maintenance, it has proven advantageous to provide image capture. This allows the marking and / or an image of the marking to be recorded, and wear can be detected early by a control system or by personnel based on the image. This allows maintenance to be scheduled well in advance. A radiation source for irradiating the marking of the wear indicator is particularly preferred. This makes it possible to determine wear under constant conditions. Radiation that is invisible to the naked eye can also be used, which, in contrast to illumination or incident light, allows a reliable determination of the wall thickness and therefore wear. The material used for the separation cone and the radiation source can also be matched to one another, so that good contour detection of the inner contour of the separation cone is possible based on the radiation reflected from the inner surface.

[0028] In one embodiment, it may be provided to move a marker with a light source and a detector around the cone in order to record a complete image of the inner contour and thus of the wear.

[0029] Further advantageous features of the invention are explained using exemplary embodiments with reference to the drawings.

[0030] Fig. 1 schematic representation of a hydrocyclone with a transparent separation cone

[0031] Fig. 2 : Separation cone with line marking before use

[0032] Fig. 3 : Separator cone with line marking with wear

[0033] Fig. 4 : Separator cone with colored marking as wear indicator

[0034] Figure 1 shows a hydrocyclone 1. Suspension to be cleaned is fed into the hydrocyclone 1 via an inlet 3. The suspension is fed into a main body 7 via the head 5 of the hydrocyclone 1. The suspension flows through the head 5 in a ring-shaped manner into a main body 7. The ring flow 17 is represented by arrows. A central flow is represented by arrows 19.

[0035] The main body 7 is connected to a separation cone 9. The separation cone 9 is made of a transparent material and has a wear indicator 31. The separation cone 9 could also be formed integrally with the main body. The wear indicator comprises a marking 33. The separation cone 9 is connected at its lower end to a lower outlet 11. An overflow, also referred to as a heavy particle reject 21, is discharged via the lower outlet 11. The lower outlet 11 is provided with a feed 25 for backwash water 27. The flow visible in the separation cone can also be used to adjust the backwash water flow. An impending blockage can also be detected early. The separation cone is imaged, enabling remote diagnosis.

[0036] Especially in waste paper processing, a wide variety of heavy particles can be present in the fiber suspension. Examples include sand, glass splinters, tiny metal particles, metal dust, heavy plastics, rubber particles, silicone particles, soot, bone splinters, rust particles, and paint splinters.

[0037] Heavy particles have a greater density than water and therefore do not float.

[0038] Heavy parts with a density of 2 grams / cm 3 and a size of 0.1 mm in diameter are very easy to separate. The smaller the heavy particles, and the smaller the density difference to water, the more difficult they are to separate in a hydrocyclone.

[0039] The separation of heavy particles from the fiber suspension is achieved through centrifugal forces, with the centrifugal forces acting on the introduced suspension in the hydrocyclone. To generate the centrifugal forces, the fiber suspension is introduced into the hydrocyclone under pressure tangentially at the inlet nozzle of the headpiece. The inlet diameter narrows to a nozzle. To ensure the proper function of the hydrocyclone and good separation efficiency for heavy particles, the inlet consistency should not exceed 2.5%. The lower the inlet consistency, the better the separation efficiency.

[0040] In the nozzle, the inlet pressure is converted into flow velocity. This tears open the fiber network downstream of the nozzle, allowing the heavy particles to be released from the fiber network. The heavy particles react to centrifugal forces and are pressed against the inner surface 39, also known as the wall, of hydrocyclone 1.

[0041] Due to the spiral in the headpiece, a spiral flow, also referred to as annular flow 17, forms on the inner wall of the hydrocyclone 9. The flow is directed downward in a spiral shape into the separation cone 7. During this process, the fibers free of heavy particles reach the central region and form the core flow 19. The core flow 19 reaches the upper outlet 15 (see the flow arrows 19 in Fig. 1). The upper outlet 15 represents the accepts discharge 23.

[0042] By means of a wear indicator 31 of the separation cone 9, it is possible, on the one hand, to use materials subject to wear for the separation cone 9 and, on the other hand, to ensure timely maintenance and / or replacement by detecting the wear.

[0043] The basic principle of the wear indicator 31 is described below.

[0044] Here, only an example of a marking 33 applied to the outer surface 38 of the transparent separation cone 9 is shown. The marking of the wear device is mirrored on the inner surface 39, 39' see Figure 2 and Figure 4, of the separation cone 9, depending on the viewing position. As the separation cone 9 wears, the wall thickness 37 of the separation cone 9 decreases. The marking 33, in particular the colored marking in strip form, is now mirrored on the inner surface 39 of the reduced wall thickness 37. With increasing wear, the wall thickness 37 becomes increasingly smaller in individual sections. As a result, the inner colored marking of the mirror image 34 increasingly approaches the outer colored marking 33. The space between the colored marking 31 and its mirror image indicates the remaining wall thickness 37. When the distance reaches 1-2 mm, the separation cone 9 should be replaced.

[0045] The reflection is also visible on the inner surface 39 when wear occurs, such as when the material of the separation cone 9 becomes cloudy, or when the inner surface 39 becomes roughened. Even in this case, a partial transparency of the cone material is maintained until the separation cone 9 is completely worn through. A reflection of 50% of the radiation radiated onto the cone at the inner surface is sufficient, as long as the image is viewed with the human eye. When using a sensor, the reflected portion and reflected intensity may be significantly lower.

[0046] Depending on the recorded wall thickness 37 of the separation cone 9, a replacement can be planned and carried out. Since wear is to be expected particularly in the lower, conically tapered area of ​​the separation cone 9, a marking 33 of the wear indicator 31 is positioned in the lower area, at least in the lower third of the separation cone 9. Here, the marking 33 extends over at least 20 cm of the axial height of the separation cone 9. In order to also record wear situations with different radial distribution, several markings 33 arranged at a distance from one another in the circumferential direction can be provided (not shown). Several markings spaced apart in the vertical direction can also be provided. Since wear will occur more frequently in the lower area in particular and can also occur very selectively, several markings of the wear indicator are provided particularly in the lower third of the separation cone.An inner surface showing noticeable wear is marked 39'.

[0047] Figure 2 shows an embodiment of a separation cone 9. The separation cone is made of a transmissive material. The marking 33 of the wear indicator 31 is applied, e.g., glued, to the outer surface 38. A mirror image 34 of the marking 33 can be seen on the inner surface. This mirror image 34 can also be recorded by the image capture 43. If the marking itself is not partially transparent, a shadow image of the marking 33 is formed on the inner surface 39 for determining the wall thickness. A partially transparent red marking is particularly easy to recognize, since red provides a good contrast to the fiber suspension in the separation cone.

[0048] As a marking of the wear indicator, several markings 33 with an at least partially axial course can be provided.

[0049] The markings can have the following forms:

[0050] - A straight line

[0051] - A slanted line

[0052] - A wavy line

[0053] - a series of points

[0054] - Applied shapes such as triangles, rectangles, special shapes

[0055] - Lettering and characters

[0056] The above-mentioned marking 33 or markings of the wear indicator 31 can have the following attachment options:

[0057] - Marking can be recessed

[0058] - Markings can be applied or placed

[0059] - Marking can be applied directly to the surface.

[0060] - Marking can be created by gluing films and thicker molded parts. - Markings can be created in the form of one or more partial inks on the separation cone.

[0061] The marking can have the following color scheme:

[0062] - Depressions or elevations can be created without additional color design.

[0063] - The marking can be coloured, all known colours can be used for this purpose, colour contrasts to the colour of the

[0064] Suspension.

[0065] - Color materials can be used to improve visibility.

[0066] - The marking can be transparent in color.

[0067] For example, in one embodiment (not shown), three grooves with a depth of 0.3 mm can be incorporated into the transparent separation cones. These grooves can be color-coded. The transparent color markings in the grooves serve as the basis for the wear indicator 31.

[0068] A method for detecting wear in a separation cone 9 of a hydrocyclone 1 can provide the step of applying a marking to the hydrocyclone, provided that no marking is already present. The wall thickness can be detected by the marking itself and its change or the change in the mirror image of the marking. If a predetermined wall thickness is undershot, a signal is output. It may be sufficient that an undershoot of the predetermined wall thickness is detected only in one area of ​​the detected area. In order to minimize the number of erroneous signals, it can be provided that a minimum extent of a minimum detected wall thickness 37 must be detected before a signal indicating a wear state of the separation cone 9 is generated.

[0069] If significant wear is suspected in an unexpected location, a colored mark can be drawn on the outer surface 38 of the separator cone 9, e.g., using a waterproof pen. This allows wear to be detected at this location as well. This can be done, in particular, during an inspection by personnel.

[0070] Furthermore, an image sensor can be provided, by means of which an image of the marking 33 is captured on demand and / or automatically at predetermined time intervals. The signals are evaluated in a controller 41. If a predetermined limit is continuously exceeded at a position and / or over a predetermined distance and / or over a predetermined period of time, a signal is output by the controller 41 to initiate a replacement.

[0071] Alternatively, a radiation source 45 can be provided, the radiation of which is reflected by the inner surface 39 of the separation cone 9. The reflected radiation is then recorded by a detector / image capture device 43. This allows the contour of the inner surface 39 of the separation cone and the thickness of the wall of the separation cone to be recorded. In such a design, the radiation and the material of the separation cone should be well matched to ensure that the inner surface is imaged by the reflected radiation. Interference radiation can be eliminated by pulsed irradiation.

[0072] A plastic can be used as the material for the transparent part of the separation cone 9. Glass can also be used.

[0073] An image capture system 43 and a controller 41 are assigned to the separation cone 9. Furthermore, a radiation source 45 is assigned to the separation cone 9. The image capture system 43 records the marking 33 of the wear indicator 31 and determines the wall thickness over at least a portion of the axial extent of the separation cone 9. The radiation source 45 can also be used to generate radiation that is invisible to the human eye and is reflected off the inner surface. Depending on the determined wall thickness, the controller outputs a signal to indicate wear. Predetermined limit values ​​are stored in the controller for this purpose. These limit values ​​can depend on the material of the separation cone and the lead times that must be planned for maintenance. When using radiation that is invisible to the eye, transparent refers to a material that is transparent to this radiation.

[0074] List of reference symbols

Claims

Patent claims 1. Separation cone (9) for a hydrocyclone (1), wherein the separation cone (9) has an upper open end for receiving suspension and a lower open end for discharging a heavy particle reject, and wherein the lower open end has a smaller diameter than the upper open end and the lower open end is connectable to a lower outlet (11) of a hydrocyclone, characterized in that the separation cone (9) is provided with a wear indicator (31) extending axially over at least a partial section of the separation cone (9) for detecting the wall thickness (37) of the separation cone (9) by reflection of radiation.

2. Separation cone according to claim 1 characterized in that the wear indicator (31) comprises at least one marking (33) on the outer surface (38) of the separation cone (9).

3. Separation cone according to claim 1 or 2, characterized in that the separation cone (9) is at least partially transparent.

4. Separation cone according to one of the preceding claims, characterized in that the marking (33) is a colored marking, preferably colored transparent, in particular in red.

5. Separation cone according to one of the preceding claims, characterized in that the wall thickness (37) is detected by reflection of radiation at the inner surface (39) of the separation cone (9).

6. Separation cone according to one of the preceding claims, characterized in that the marking (33) is attached or applied on or in the area of ​​the outer surface (38) of the separation cone (9) so that the marking is not subject to wear.

7. Separation cone according to one of the preceding claims, characterized in that the marking (33) is provided for generating a mirror image on the inner surface (39) of the separation cone (9).

8. Separation cone according to one of the preceding claims, characterized in that the marking (33) comprises several marking elements which are arranged distributed in the circumferential direction of the separation cone (9).

9. Separation cone according to one of the preceding claims, characterized in that the separation cone (9) is made of a plastic.

10. Hydrocyclone (1 ) with an inlet (3) for the supply of fiber suspension and a lower outlet (11 ) and a separation cone arranged above the lower outlet (11 ), characterized in that the separation cone (9) is a separation cone (9) according to one of the preceding claims.

11. Hydrocyclone (1) according to claim 10, characterized in that, that the separating cone (9) is provided with an image capture (43) for the image capture of a reflection of an image of the marking (33) for the detection of the wear indicator (31).

12. Hydrocyclone (1 ) according to one of claims 10 or 11 , characterized in that a radiation source (45) is provided for irradiating the marking (33) of the wear indicator (31 ) of the separation cone (9).

13. Method for operating a hydrocyclone (1) with a separation cone (9) for purifying a fiber suspension, characterized in that the separation cone (9) is provided with a wear indicator (31) and the wall thickness (37) of the separation cone (9) is detected during operation, wherein the detected values ​​of the wall thickness (37) indicate wear at at least one point if a predetermined value is undershot, and wherein the detected values ​​of the wall thickness are preferably supplied to a control unit (41) and the control unit automatically generates a signal indicating wear if the wall thickness falls below a predetermined value.

14. Method according to claim 13, characterized in that images of the separation cone (9) are captured by an image capture device (43) and supplied to a control unit (41) and a minimum wall thickness of the separation cone (9) is determined in the control unit (41).

15. Method according to one of claims 13 or 14, characterized in that the wall thickness (37) of the separation cone (9) is measured at predetermined time intervals.

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