Screw press separator with modified press screw

Abstract

The invention relates to a press screw separator (1) for separating solid components from a turbid suspension containing solid and liquid components, comprising: a housing (2), a cylindrical screen (4) arranged in the housing (2), and a scraper element (3) arranged within the screen (4) and rotationally mounted about a longitudinal axis (5) of the screen (4) and having at least one continuous screw spiral (31) for pressing out the turbid suspension, wherein, in addition to the at least one continuous screw spiral (31), the scraper element (3) is also provided with one or more stripping elements (32), wherein the stripping elements (32) are arranged within the screen, only over a first region on the scraper element (3), which starts at the beginning of the screen (4) and ends before the end of the screen (4), when viewed in the conveying direction of the scraper element (3), the stripping elements (32) being secured on a screw shaft (33) of the scraper element (3) or the stripping elements (32) being secured on the continuous screw spiral (31) and protruding from same in the axial direction.

Description

[0001] Press screw separator with modified press screw

[0002] The present invention relates to a press screw separator for separating solid components from a slurry containing solid and liquid components.

[0003] Screw press separators are used to press slurry. The slurry can be, in particular, manure or wastewater. Wastewater can originate from agricultural, municipal, and industrial plants, and the wastewater always needs to be separated into solid and liquid components. In some cases, it is advantageous to add precipitants or flocculants to the slurry before pressing. The housing of the screw press separator typically contains a cylindrical screen, within which a rotating agitator element rotates. The agitator element conveys and presses the slurry through the screw press separator. The liquid components of the slurry pass through the screen, while a plug of solids forms within the screen.The rotating scraper element, on the one hand, removes any adhering fibers from the screen's inner surface to ensure continuous dewatering of the slurry. On the other hand, the solid plug is conveyed to one end of the press screw separator for ejection. The torque from the scraper element is transferred to the screen via the solid plug. Therefore, the screen must be mounted in the housing so that it cannot rotate.

[0004] In practice, it has been shown that the geometry of the clearing element has a decisive influence on the performance of press screw separators. Press screw separators described so far usually have a screw with one or more screw flights that extend up to a certain point in the screen or beyond; in any case, if there are several screw flights, they all end at the same point in the machine. The screw flights must be a minimum distance from each other to prevent the thickened slurry from getting stuck in the screw flights and clogging the screw. The more screw flights used, the better the performance of a press screw separator, because with each revolution the screw flights free the inner surface of the screen of adhering fibers, thus making the screen passable again for the liquid portion of the slurry.However, if too many screw flights are used, the problem arises that in the area of ​​the screen where the slurry has already thickened into a solid, the screw flights can easily clog if the screw flights are too narrow. Known screws in press screw separators therefore incorporate screw flights that represent a compromise between performance and low susceptibility to clogging. The state of the art is represented in particular by the documents AT17259B, DE4232449A1, DE 102008048091 B4, and AT 509618 A1.

[0005] In detail, AT17259B describes a screw press with several individual, non-connected spirals. This is disadvantageous for the screen's clearing by the screw flights in areas where the slurry is still liquid, as there are no spirals in some areas of the screen.

[0006] DE4232449A1 describes a press screw separator with a screw with two symmetrically opposed screw flights.

[0007] DE 102008048091 B4 describes a liquid separator with at least one clearing element, which comprises at least two rotor elements arranged parallel to one another, which are designed as worm thread elements which have the same pitch and are arranged axially offset from one another.

[0008] AT 509618 A1 describes a press screw separator with a press screw with at least one screw flight arranged thereon for common rotation with the screw shaft.

[0009] US 2009 / 0183971 A1 discloses a clearing element with a screw flight, wherein brushes are provided over a first region of the clearing element. The brushes are mounted on the outer end of the screw flight and allow the screw flight and the screen basket to be manufactured with greater tolerances. The brushes subsequently compensate for these tolerances. This is also the reason why the brushes are mounted only on the outer circumference of the screw flight.

[0010] The object of the present invention, based on the prior art described above, is therefore to create a technically simple press screw separator of the type mentioned at the outset, which, compared to similar machines, has an increased performance due to a modified geometry of the clearing element and yet does not clog during operation.

[0011] The object is achieved by a press screw separator for separating solid components from a slurry containing solid and liquid components, comprising: a housing, a cylindrical sieve which is arranged in the housing, and a clearing element arranged within the sieve and mounted such that it can rotate about a longitudinal axis of the sieve, with at least one continuous screw flight for pressing out the slurry, wherein the clearing element is equipped with one or more stripping elements in addition to the at least one continuous screw flight, wherein the stripping elements are arranged within the sieve only over a first section on the clearing element, which section begins at the beginning of the sieve and ends before the end of the continuous screw flight, seen in the conveying direction of the clearing element.The scraper elements are either attached to a screw shaft of the clearing element or are attached to the continuous screw flight and protrude axially from it. The distance between the end of the first section and the end of the continuous screw flight is referred to as the second section and has a length corresponding, for example, to 35-80% of the length of the screen. The dependent claims contain advantageous developments of the invention.

[0012] According to the invention, a screw press separator is thus created which comprises a housing in which a sieve is mounted. This housing, as is usual with other screw press separators, generally absorbs all radial and axial forces acting during operation. Furthermore, the screw press separator according to the invention can comprise a cover surrounding the housing in order to concentrate and drain the liquid phase after separation. Furthermore, the screw press separator according to the invention comprises a clearing element arranged within the sieve and mounted for rotation about a longitudinal axis of the sieve for pressing out the slurry. The sieve is usually cylindrical, with the housing also preferably being cylindrical.

[0013] The clearing element preferably comprises a screw shaft with one or more continuous rotor elements, designed as screw flights that convey the slurry to be separated from the inlet area of ​​the press screw separator through the screen. These screw flights may end shortly before the end of the screen on the discharge side of the housing.

[0014] Furthermore, according to the invention, the clearing element comprises one or more additional scraping elements in the initial area of ​​the screen. These additional scraping elements, while the speed of the clearing element remains unchanged, multiply the frequency with which the adhering fibers of the slurry are scraped off the inner surface of the screen, resulting in increased performance of the press screw separator. In other words, the scraping elements can clean the screen basket at a location other than the existing screw flights. To achieve this, according to the invention, the scraping elements are either attached to a screw shaft of the clearing element or are attached to the continuous screw flight and protrude axially from it.

[0015] If the scraper elements are attached to the screw shaft, they extend radially from the screw shaft, e.g., to the screen. In other words, the scraper elements can be the same height in the radial direction as the at least one continuous screw flight. In more general embodiments, however, the scraper elements could also be shorter in the radial direction than the at least one continuous screw flight.

[0016] If the scraper elements are attached to the at least one continuous screw flight, they preferably protrude in such a way that they do not increase the size of the clearing element in the radial direction. This can be used in particular if, with the aforementioned variant, the distances between the screw flights and the additional flights mounted on the screw shaft would prove to be too small during operation, which could pose a risk of clogging. The risk of clogging is certainly reduced with scraper elements attached to the continuous screw flights.

[0017] In the latter variant, the scraper elements can, for example, be attached to the radially outer edge of the at least one screw flight and protrude exclusively axially, i.e., they extend substantially parallel to the longitudinal axis of the clearing element, whereby the clearing element is not enlarged in the radial direction. Alternatively, the scraper elements can also be attached between the screw shaft and a radially outer edge of the at least one continuous screw flight and protrude therefrom both radially and axially, with an acute angle preferably existing between the longitudinal axis of the clearing element and the scraper elements.

[0018] If the scraper elements are attached to the at least one continuous screw flight, they can either have a free end or extend between two turns of one or more of the at least one continuous screw flight, which offers a particularly stable design.

[0019] In summary, it is preferred if the outer diameter of the at least one continuous screw flight essentially corresponds to the outer diameter of the stripping elements, although this is not mandatory. Furthermore, the stripping elements can preferably have a cutting edge, which facilitates the scraping of fibers on the screen.

[0020] The additional stripping elements preferably begin not in the inlet area, but only in the screen area, in order to more easily guide fibers in the inlet area into the screw flights of the clearing element. In other words, it is preferred if the stripping elements on the entire clearing element are arranged only over the first section and, in particular, if no stripping elements are provided in an inlet area on the clearing element upstream of the screen. In other embodiments, however, it could also be provided to provide the stripping elements on the clearing element upstream of the screen in the inlet area.

[0021] To prevent blockages in the screw, the additional scraper elements, unlike the at least one continuous screw flight, end in a region of the screen where the thickened slurry is still flowable or pasty, and certainly not shear-resistant. This ensures that in the area of ​​the screen where the slurry has already thickened into a shear-resistant solid, the friction in the screw flights of the at least one continuous screw flight is not further increased by scraper elements, which would prevent this solid from clogging the screw flights.

[0022] The additional scraper elements are preferably designed as screw flights and connected to the screw shaft, but can also be designed as pins, flat bars, blades, or other geometries connected to the screw shaft. The scraper elements can also be connected to the continuous screw flights without being connected to the screw shaft.

[0023] Furthermore, it is preferably provided that the stripping elements occupy a proportion of 20% to 65% of the screen area. As the slurry is conveyed through the press screw separator, it continues to thicken until a solid plug remains, which is ejected at the end of the machine. In this process, the friction of the fibers on the scraping element continuously increases. Therefore, according to the invention, the area in which the stripping elements are placed should be selected in the first area of ​​the screen in such a way that blockages in the scraping element due to excessive friction and insufficient distance between the continuous screw flights and the stripping elements are avoided. The invention will now be described in detail using an exemplary embodiment with reference to the attached drawing. In the drawing:

[0024] Fig. 1 is a schematic representation of a press screw separator according to an embodiment of the invention.

[0025] Figure 2 shows different variants of the stripping elements of the press screw separator according to the invention.

[0026] Fig. 1 shows a screw press separator 1 comprising a housing 2 in which a single- or multi-part screen 4 and the reaming element 3 rotating therein are installed. Only those components of the screw press separator that are relevant to the present invention are described below. All remaining components correspond to those used in known screw press separators.

[0027] The clearing element 3 and the sieve 4 are arranged within the housing 2. The clearing element 3 can compress a slurry so that liquid components can be separated from solid components. The solid portion of the slurry is ejected at the outlet 22. So that the solid portion can be conveyed to the outlet 22, the sieve 4 is provided, which extends cylindrically around the clearing element 3. The sieve 4 has a longitudinal axis 5, which is also the longitudinal axis of the clearing element 3. The sieve 4 can be designed in one part or in several parts. If the sieve 4 is designed in several parts, the different parts of the sieve 4 can differ, for example, in their structure or in their connection to the housing.

[0028] In the illustrated embodiment, the clearing element 3 comprises a screw shaft 33 and two opposite, rotating screw flights 31 extending from the inlet area 21 through substantially the entire screen 4. As is known to those skilled in the art, screw flights are understood to mean spirally rotating rotor blades. In the example shown in Figure 1, the screw flights 31 thus extend over an inlet area AO of the clearing element 3 located upstream of the screen 4 and over those two sections A1, A2 of the clearing element 3 that are arranged at the beginning of the screen 4. Viewed in the conveying direction of the clearing element 3, the continuous screw flights 31 thus end at the end of the second section A2. An end section A3 of the clearing element 3, which is arranged at the end of the screen 4 - but within the screen 4 - can optionally remain free of screw flights 31.Such an arrangement of screw flights 31 is known per se from the prior art, so that they are referred to below as continuous screw flights 31.

[0029] In other embodiments, instead of the two continuous screw flights 31, only one continuous screw flight 31 or more than two continuous screw flights 31 could be used. All continuous screw flights 31 extend over all three sections A0, A1, A2.

[0030] According to the invention, the clearing element 3 further comprises additional stripping elements 32, which extend from the beginning of the screen 4 into a region of the screen 4 in which the slurry is not yet shear-resistant during operation of the press screw separator. This section of the clearing element 3, on which the stripping elements 32 are arranged, is referred to as the first section A1. The first section A1 ends before the end of the continuous screw flight 31, i.e. before the end of the second section A2 (in each case viewed in the conveying direction of the clearing element 3). The stripping elements 32 free the screen 4 from adhering fibers on its inner surface more often than would be the case with the continuous screw flights 31 alone. This significantly increases the possible throughput of the liquid components of the slurry and thus the performance of the press screw separator. In the radial direction, the stripping elements 32 generally extend as far as the screen 4.

[0031] From Figure 1 it can be seen in particular that the stripping elements 32 are only arranged over the first section A1. The first section A1 begins at the start of the screen 4 and ends before the end of the screen 4 and also before the end of the continuous screw flight 31, seen in the conveying direction of the clearing element 3. Usually no stripping elements 32 are arranged above the inlet area AO upstream of the screen 4, i.e. before the start of the screen 4 there are generally no stripping elements 32 arranged on the clearing element 3, since they would have no effect. In other embodiments, however, stripping elements 32 could also be arranged above the inlet area AO upstream of the screen 4, e.g. if this facilitates the production of the clearing element 3. Furthermore, no stripping elements 32 are arranged above a second section A2 on the clearing element 3, which is located inside the screen 4 and downstream of the first section A1.Thus, only the continuous screw flights 31 are located on the second section A2. In other words, the scraper elements 32 are arranged within the screen 4 over the length of the first section A1, and the continuous screw flights 31 over a length A1+A2, which corresponds to the sum of the first section A1 and the second section A2. Furthermore, there are no scraper elements 32 above the optional end section A3, which is located at the end of the screen 4 and where the continuous screw flights 31 can also be omitted. The first section A1 typically extends over a length of 20-65% of the screen 4, and the second section A2 typically extends over a length of 35-80% of the screen 4. The optional end section A3 typically extends over a length of 0-20% of the screen 4.

[0032] The first section A1, over which the scraper elements 32 are arranged in the area of ​​the screen 4, makes up, for example, up to or substantially 20%, 40%, 50%, or 65% of the total length of the screen 4. This is chosen with the background that the slurry is compressed across the longitudinal axis 5, with liquid components constantly passing through the screen 4 and the solid components of the slurry remaining within the screen 4. Thus, the dry matter content of the solids within the screen 4 steadily increases as the solids approach the outlet 22. This also causes a steadily increasing friction between the solids and the screw flights 31 and the scraper elements 32. To prevent clogging due to the increasing friction, the scraper elements 32 end earlier in the screen 4 than the continuous screw flights 31. Overall, this enables safe and reliable operation with increased performance.

[0033] The stripping elements 32 are preferably also designed as one or more screw flights located in the first section A1 in the spaces between the first-mentioned continuous screw flights 31. In other words, there are more or denser screw flights across the first section A1 than across the second section A2.

[0034] Alternatively, the stripping elements 32 could also be designed as flat irons, pins, blades, or other geometries. Furthermore, the stripping elements 32 are preferably attached to the worm shaft 33, but can also be attached additionally or exclusively to one or more of the continuous worm flights 31.

[0035] Fig. 2 shows the clearing element 3, on which various variants of stripping elements 32, 34, 35, 36, 37 are arranged. As shown, various stripping elements 32, 34, 35, 36, 37 can be combined on a single clearing element 3 across the first section A1, although it is preferred that only one type of stripping elements 32, 34, 35, 36, 37 be provided on a clearing element 3 across the first section A1. It is particularly evident that the at least one continuous screw flight 31 has an outer diameter D1 that essentially corresponds to the inner diameter of the screen. The scraper elements 32, 34, 35, 36, 37 have, regardless of the specific design or the location of the attachment to the clearing element 3, an outer diameter D2 which is preferably the same size as the outer diameter D1 of the at least one continuous screw flight 31.This has the effect that both the continuous screw flight(s) 31 and the stripping element 32, 34, 35, 36, 37 can free the sieve 4 of adhering fibers. However, it would also be possible for the outer diameter D2 of the stripping elements 32, 34, 35, 36, 37 to be smaller than the outer diameter D1 of the at least one continuous screw flight 31, since this nevertheless promotes conveying of the slurry, which is not yet shear-resistant in this area, to the screw flights 31 or can be useful if the at least one continuous screw flight 31 comprises flexible elements at the radially outer ends. Usually, however, it is provided that the outer diameter D2 of the stripping elements 32, 34, 35, 36, 37 is not larger than the outer diameter Dl, although this should not be excluded, e.g. if the stripping elements 32, 34, 35, 36, 37 have flexible elements at their ends.

[0036] The stripping element, denoted by reference numeral 32, is formed by two opposing screw flights (but could also be formed by a single or more than two screw flights), which are located in the first section A1 in spaces between the first-mentioned continuous screw flights 31. It can be seen that this stripping element 32 is fastened to the worm shaft 33. This additional screw flight, which runs only over the first section A1, is designed to be continuous over the first section A1 and preferably has the same outer diameter D2 as the continuous screw flight 31.

[0037] The stripping element, indicated by reference numeral 34, is formed by one or more blades that are mounted on the worm shaft 33 and project to the outer diameter D2, which corresponds to the outer diameter D1 of the at least one continuous worm flight 31. It can be seen that the blade projects radially and is non-contact with the worm flights 31.

[0038] The stripping element, represented by the reference numeral 35, is formed by one or more blades that are fastened to the at least one continuous screw flight 31. This blade protrudes in the axial direction from the at least one continuous screw flight 31, so that the blade covers an area between the turns of the at least one continuous screw flight 31. However, these blades do not extend completely to the next turn of the at least one continuous screw flight 31, but have a free end and are fastened to the at least one continuous screw flight 31 on only one side.

[0039] The stripping element, indicated by reference numeral 36, is formed by one or more blades mounted on the at least one continuous screw flight 31. This blade projects axially from the at least one continuous screw flight 31 and extends from one turn of the at least one continuous screw flight 31 to the next. This is possible both when there is a single continuous screw flight 31 or when there are two or more continuous screw flights 31 (in which case the blade can extend from one continuous screw flight 31 to another continuous screw flight 31).

[0040] The stripping elements 35, 36 are each attached to the radially outer edge of the at least one continuous screw flight 31 and extend (apart from a thickness of the stripping elements 35, 36) exclusively in the axial direction, so that they do not exceed the outer diameter D1 of the at least one continuous screw flight 31. In other words, the stripping elements 35, 36 are arranged substantially parallel to the longitudinal axis of the clearing element 3.

[0041] The stripping element represented by the reference numeral 37 is formed by one or more blades which are fastened to the at least one continuous screw flight 31. The blades are fastened to the at least one continuous screw flight 31 between the worm shaft 33 and the radially outer edge of the at least one continuous screw flight 31 (ie are at a distance from the radially outer edge) and protrude from the latter both in the radial direction and in the axial direction, so that a free end of the blades is substantially at an outer diameter D2 which corresponds to the outer diameter D1 of the at least one continuous screw flight 31. In the example shown, the angle between the stripping element 37 and the longitudinal axis of the clearing element 3 is substantially 45°.The angle could, for example, also be between 60° and 0°, preferably between 45° and 5° or between 30° and 5°, so that the scraper element 37 can protrude as far as possible from the at least one continuous screw flight 31.

[0042] In contrast to the stripping element 32, which is designed as an additional screw flight, the stripping elements 34, 35, 36, 37 are not continuous, but are arranged essentially at specific points or in a linear fashion. The stripping elements 34, 35, 36, 37 are typically arranged parallel to the longitudinal axis of the reaming element 3, optionally with a radial inclination, and / or have a relatively small width in the circumferential direction, e.g., a width of less than 10% of the circumference.

[0043] It is possible for only a single stripping element 34, 35, 36, 37 to be present in the first section A1, or multiple stripping elements 34, 35, 36, 37 can be provided along the circumference of the clearing element 3 and / or in the axial direction of the clearing element 3. Although the stripping elements 34, 35, 36, 37 are designed as blades in Figure 2, they could also be designed as pins, flat irons, or other rigid elements.

[0044] Preferably, the scraping elements 34, 35, 36, 37 have a cutting edge which promotes scraping on the sieve.

[0045] It is understood that the above statements apply regardless of whether one or more continuous screw flights 31 are used. If the scraper elements 34, 35, 36, 37 are attached to the continuous screw flights 31, they can be attached to all or only some of the screw flights 31.

[0046] It should be noted that the terms “radial”, “axial” and “circumferential direction” used herein refer to the longitudinal axis of the clearing element 3 and the screen 4, respectively.

[0047] List of reference symbols

[0048] 1 press screw separator

[0049] 2 housings

[0050] 21 Inlet area

[0051] 22 Outlet

[0052] 3 clearing element

[0053] 31 continuous screw flights

[0054] 32, 34, 35, 36 ,37 scraper elements

[0055] 33 Worm shaft

[0056] 4 sieve

[0057] 5 Longitudinal axis

[0058] AO inlet area

[0059] The first section

[0060] A2 second section

[0061] A3 final section

Claims

Patent claims 1. Press screw separator (1) for separating solid components from a slurry containing solid and liquid components, comprising: a housing (2), a cylindrical sieve (4) arranged in the housing (2), and a clearing element (3) arranged within the sieve (4) and mounted for rotation about a longitudinal axis (5) of the sieve (4), with at least one continuous screw flight (31) for pressing out the slurry, wherein the clearing element (3) is equipped, in addition to the at least one continuous screw flight (31), with one or more stripping elements (32, 34, 35, 36, 37), wherein the stripping elements (32, 34, 35, 36, 37) are arranged within the sieve (4) only over a first section (A1) on the clearing element (3), which begins at the beginning of the sieve (4) and before the end of the continuous Screw helix (31) ends, seen in the conveying direction of the clearing element (3), characterized in that the scraper elements (32,34) are attached to a worm shaft (33) of the clearing element (3), or that the stripping elements (35, 36, 37) are attached to the at least one continuous worm flight (31) and protrude from it in the axial direction.

2. Press screw separator according to claim 1, characterized in that the stripping elements (32) are designed as one or more screw flights.

3. Press screw separator according to claim 1, characterized in that the stripping elements (34, 35, 36, 37) are designed as flat iron.

4. Press screw separator according to claim 1, characterized in that the stripping elements (34, 35, 36, 37) are designed as pins.

5. Press screw separator according to claim 1, characterized in that the stripping elements (34, 35, 36, 37) are designed as blades.

6. Press screw separator according to one of the preceding claims, characterized in that the stripping elements (32, 34, 35, 36, 37) on the clearing element (3) only are arranged over a length of up to 20%, up to 40%, up to 50% or up to 65% of the sieve (4).

7. Press screw separator according to one of the preceding claims, characterized in that the stripping elements (32, 34, 35, 36, 37) on the entire clearing element (3) are arranged only over the first section (A1) and in particular no stripping elements (32, 34, 35, 36, 37) are provided in an inlet area (AO) on the clearing element (3) upstream of the screen (4).

8. Press screw separator according to one of the preceding claims, characterized in that the outer diameter (Dl) of the at least one continuous screw flight (31) corresponds to the outer diameter (D2) of the stripping elements (32, 34, 35, 36, 37).

9. Press screw separator according to one of the preceding claims, characterized in that the stripping elements (35, 36) are fastened to a radially outer edge of the at least one continuous screw flight (31) and are substantially parallel to the longitudinal axis of the clearing element (3).

10. Press screw separator according to claim 9, characterized in that the stripping elements (35, 36) have a free end.

11. Press screw separator according to claim 9, characterized in that the stripping elements (35, 36) extend between two turns of one or more of the at least one continuous screw helix (31).

12. Press screw separator according to one of claims 1 to 8, characterized in that the stripping elements (37) are fastened between the screw shaft (33) and a radially outer edge of the at least one continuous screw flight (31) and protrude from the latter both in the radial direction and in the axial direction.

13. Press screw separator according to one of the preceding claims, characterized in that Ab stripping elements (32, 34, 35, 36, 37) have a cutting edge.

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