Solid-bowl centrifuge

Abstract

The invention relates to a solid-bowl centrifuge for processing a suspension (Su) in a centrifugal field, wherein the suspension (Su) is divided into at least one liquid phase (Fl) and a slurry or solid phase (Fe), comprising a machine frame (100) and a rotor which is rotatably mounted in the machine frame (100). The invention is characterized in that the machine frame (100) consists entirely or substantially of UHPC.

Description

[0001] Solid bowl centrifuge

[0002] The invention relates to a solid bowl centrifuge according to the preamble of claim 1.

[0003] Industrial centrifuges, such as solid-bowl screw centrifuges, have rapidly rotating components. The rotor, in particular, with its rotating elements—in the case of a solid-bowl screw centrifuge, especially the bowl and the screw—rotates at high speeds during operation. Unavoidable imbalances, caused, for example, by product buildup in the bowl or on the screw, an unfavorable, inhomogeneous product distribution in the bowl, and / or mechanical wear, generate vibrations. Due to the rotor's high rotational frequency, these vibrations also manifest themselves in undesirable noise during operation of the solid-bowl screw centrifuge.

[0004] To date, steel constructions have been used almost exclusively for the machine frames or housings of solid-bowl screw centrifuges, as steel has a high modulus of elasticity and thus high static rigidity. However, the damping factor D of steel—a parameter for dynamic rigidity—is relatively low at 0.02%.

[0005] For these reasons, such designs require complex vibration isolation from the surrounding environment. Another means of vibration dampening is limiting the maximum speed of the rotors used. However, this prevents the theoretically possible separation performance of the solid bowl screw centrifuge from being fully achieved.

[0006] Various approaches to solving these problems are known from the prior art. DE 43 15 694 A1 shows the design of a machine frame with a base frame composed of hollow profiles, particularly box-shaped hollow profiles. The cavities of the hollow profiles are preferably filled with mineral casting. The hollow profiles thus serve as formwork for the mineral casting and for securely holding fastening elements.

[0007] DE 10 312 966 A1 describes a machine frame for a centrifuge for dewatering sludge. The machine frame is made of reactive resin concrete, with the surface of the machine frame fully or partially covered with a metal facing. The metal facing serves to increase the mechanical strength of the structure and to facilitate machining of the machine frame, such as drilling. Therefore, the manufacture of this frame requires a relatively high level of effort. To date, no market entry of such frames has been recorded for solid-bowl screw centrifuges.

[0008] The object of the invention is therefore to provide a solid bowl centrifuge having a machine frame which has significantly improved damping properties compared to the machine frames of the prior art.

[0009] The invention solves this problem by the subject matter of claim 1. Accordingly, a solid bowl centrifuge is created for processing a suspension in a centrifugal field, wherein the suspension in the solid bowl centrifuge is separated into at least two phases, with

[0010] - a machine frame with a rotor rotatably mounted in the machine frame,

[0011] - which has at least one drum rotatable about a rotation axis d, and

[0012] - with a drive device with which the drum can be rotated.

[0013] It is further provided that the machine frame consists entirely or essentially of the particularly suitable material UHPC.

[0014] This creates the prerequisite for a low-vibration and quieter-running solid-bowl centrifuge, especially a solid-bowl screw centrifuge. Compared to machine frames made of polymer concrete or mineral cast, the machine frame made of UHPC (ultra-high performance concrete, explained in more detail below) is also characterized by its significantly higher modulus of elasticity (UHPC is particularly well-suited for this application, with 60,000 - 100,000 N / mm²). 2 ) and a density between 2,500 and 3,000 kg / m 3, which results in increased static stiffness compared to machine frames made of polymer concrete or mineral cast. Furthermore, UHPC exhibits significantly higher compressive strength than polymer concrete or mineral cast. Due to its good damping properties against mechanical vibrations, it enables a simpler vibration decoupling of the machine frame from the rotor and / or the substructure. Ideally, additional decoupling elements are no longer required. The construction is further enhanced by the higher dynamic stiffness of the UHPC machine frame (preferably "UHPC e80", i.e., a modulus of elasticity of 80,000 N / mm 2) is simplified. Furthermore, the UHPC machine frame offers the potential to increase the rotor speed by increasing the natural frequency of the machine frame, which would increase the performance of the solid bowl centrifuge, especially the solid bowl screw centrifuge. Compared to a steel machine frame, the machine frame is also more resource-efficient and therefore more sustainable to manufacture. The abbreviation UHPC stands for “Ultra High Performance Concrete”. This is a type of concrete that is characterized by its high density and strength. For the purposes of this document, this special UHPC has a specific stiffness of > 28 kNm / g, specifically 28.6 kNm / g. The specific stiffness is the ratio of the Young’s modulus of the UHPC to the density of the UHPC.

[0015] It is preferred and expedient that the drum further comprises an inlet line through which the suspension Su to be processed can be conducted into a separation space of the drum, at least one liquid outlet through which the liquid phase is discharged, and at least one solids discharge through which the centrifugally separated sludge or solids phase is led out of the drum.

[0016] In a particularly preferred embodiment of the invention, the machine frame is designed as a solid, solid concrete frame, which consists entirely or substantially of UHPC—i.e., except for connecting elements, in particular metal parts for attaching corresponding connecting parts. This significantly reduces the use of metal, as metal parts as formwork or reinforcement are omitted, thereby advantageously simplifying the manufacture of the machine frame. Preferably, the machine frame consists of more than 90% UHPC concrete material. The remaining portion can, for example, be made up of connecting elements cast into the concrete material.

[0017] According to a further particularly preferred embodiment of the invention, the weight ratio between the machine frame and the rotor is greater than 2 and in particular 2.4, which means that the machine frame is 2.4 times heavier than the rotor. Due to the higher frame weight of the machine frame relative to the rotor, the rotor can run significantly more smoothly. The high specific stiffness, which enables an increase in the natural frequencies, reduces vibration excitation of the entire machine. This further reduces the amplitude of the forced excitation of the machine frame by the rotor. The amplitude of a forced vibration is inversely proportional to the excited mass (frame) and the excitation force is proportional to the excitation mass (rotor). When using a machine frame made of steel, in which the mass ratio between the frame weight and the rotor is typically less than 1 (and e.g.is 0.9, which means that the machine frame is of the same weight or lighter than the rotor), vibration excitation is not significantly reduced. According to a particularly preferred - but not mandatory - embodiment, the solid bowl centrifuge can further comprise a screw arranged in the bowl, which is driven by the drive device at a differential speed relative to the rotatable bowl, so that it is designed as a solid bowl screw centrifuge. Especially with such designs, the machine frame is subjected to particularly high loads during operation, so that the use of the machine frame, which consists essentially of UHPC, is particularly advantageous.

[0018] According to a further, particularly preferred embodiment of the invention, the machine frame can have a substantially frame-like basic geometry. This creates a simple, load-adapted, and rigid basic geometry for the machine frame.

[0019] In a further preferred embodiment of the invention, the machine frame comprises two parallel longitudinal beams, which are integrally connected to one another by a first transverse beam and a second transverse beam. This easily creates a frame-shaped and therefore particularly rigid machine frame for the solid-bowl centrifuge.

[0020] Furthermore, according to another particularly preferred embodiment of the invention, it can be provided that precisely or approximately semicircular recesses are formed in each of the two cross members, which are intended to accommodate a first portion of the drum's bearings. These recesses allow the bearings, and thus the rotor, to be arranged in the machine frame in such a way that the center of gravity of the rotor is located close to the center of gravity of the machine frame, which can have a beneficial effect on the rotor's operating rotational behavior.

[0021] According to a further preferred embodiment of the invention, a metal plate can be embedded in the respective solid cross member on both sides of the respective recess, with fastening means such as threaded holes being incorporated into the respective metal plate, through which the respective bearing can be firmly connected to the machine frame in the area of ​​a bearing housing. This provides a simple way of attaching the bearings to the UHPC machine frame.

[0022] According to a further, particularly preferred embodiment of the invention, it is provided that a semi-truncated cone-shaped recess is introduced between the two cross members, which is intended to receive the rotor, so that the rotor, in the assembled state, lies to a considerable extent, in particular approximately half, in the machine frame, which can also have an advantageous effect on the running behavior.

[0023] According to yet another preferred embodiment of the invention, a base plate is formed in the region of the recess, which is integrally connected to the two longitudinal beams and the two transverse beams. The base plate provides additional stiffening to the machine frame through a simple structural measure.

[0024] In a further preferred embodiment of the invention, several connecting elements—which can be designed in particular as metal plates—are embedded in the upper side of each longitudinal beam. Fastening elements, such as threaded holes, are provided in each of these elements, through which a hood can be firmly connected to the machine frame. This provides a simple way to attach the hood to the UHPC machine frame.

[0025] Furthermore, in a further preferred embodiment of the invention, the respective longitudinal beam is extended behind the second cross beam and is provided with a step, so that the respective longitudinal beam continues at a lower height level as a support beam for the drive device. The two support beams are integrally connected to one another by a third cross beam, and the third cross beam is arranged parallel to the other two cross beams. Thus, the design principle of a frame-shaped, particularly rigid machine frame made of UHPC is also implemented for the arrangement of the drive device on the machine frame.

[0026] According to a further preferred embodiment of the invention, the respective support beam extends cantilever-like with a free end behind the third cross beam. This creates a material-saving support beam for the drive device on the machine frame.

[0027] In a further preferred embodiment of the invention, one or more connecting elements—which may in particular be designed as metal plates—may be placed on or cast into the upper side of the respective support beam. Holes or threaded holes may be provided in the connecting elements—which may in particular be designed as metal plates—for fastening the drive device to the machine frame. This provides a simple way of fastening the drive device to the UHPC machine frame.

[0028] Further advantageous embodiments of the invention can be found in the remaining subclaims.

[0029] The invention is described in more detail below with reference to exemplary embodiments and the drawings. Features described in connection with these exemplary embodiments can also be used in other—not shown—embodiments of the invention and are therefore also usable as features in claims. They show:

[0030] Figure 1: a spatial view of a solid bowl screw centrifuge with a horizontal axis of rotation with a machine frame according to the invention;

[0031] Figure 2: a spatial view of the machine frame from Fig. 1 without, for example, the

[0032] Rotor, the hood and the drive device.

[0033] The following description of the figures describes an embodiment of a solid-bowl centrifuge. The individual features of this embodiment can also be combined with embodiments not shown and are also suitable as advantageous embodiments of the subject matter described in one or more of the main and subclaims.

[0034] Fig. 1 shows a solid-bowl screw centrifuge 1. The solid-bowl centrifuge 1 is used to process a suspension Su in a centrifugal field, wherein the suspension Su is separated into at least one liquid phase Fl and a sludge or solid phase Fe.

[0035] The solid bowl screw centrifuge 1 has a machine frame 100 in which the rotor is rotatably mounted. The rotor is covered by a hood 2. The rotor has a rotatable drum with a horizontal axis of rotation. The drum has an inlet line 3 projecting into the drum and arranged concentrically to the axis of rotation, through which line the suspension Su to be processed can be guided into a separation chamber of the drum. The drum also has a screw arranged in the drum that can rotate at a differential speed relative to the rotatable drum. Furthermore, the drum has at least one liquid outlet through which the liquid phase Fl is discharged, and at least one solids discharge through which the sludge or solid phase Fe is discharged. A drive device 4 drives the rotor. The drive device 4 rotates the drum on the one hand and the screw on the other.For this purpose, the drive device can be equipped with two drive motors or one drive motor 5 and a gearbox with two outputs.

[0036] The machine frame 100 is shown in Fig. 2 without the rotor, the hood 2, and the drive device 4. Machine feet 6 are arranged below the machine frame 100. Further details on the exemplary components of a solid-bowl screw centrifuge 1 can be found, for example, in DE 10 2019 126 325 A1.

[0037] According to Figs. 1 and 2, the machine frame 100 consists entirely or substantially of the concrete material referred to as UHPC. UHPC (abbreviated for ultra high performance concrete) refers to a concrete characterized by a particularly high structural density and compressive strength. The special UHPC material of this application preferably has a higher specific stiffness (28.6 kNm / g) than steel (typically 26.8 kNm / g) and polymer concrete (typically 16.7 kNm / g). This results from a density of 2,800 kg / m 3 and an elastic modulus of 80,000 N / mm 2 . Suitable for the machine frame described here are UHPC materials with an elastic modulus between 60,000 and 100,000 N / mm 2 , especially 80,000 N / mm 2 and a density between 2,500 and 3,000 kg / m 3 , in particular 2,800 kg / m 3 In addition, it preferably has a compressive strength of over 150 N / mm 2and a w / c (water / cement) ratio of < 0.25. Fibers (steel fibers, glass fibers, carbon fibers, etc.) can also be added to the UHPC, which can further enhance its positive properties.

[0038] The following table shows further material properties of common UHPC of interest here in contrast to UHPC (e80) for this application as well as in comparison to polymer concrete / mineral casting, normal concrete and cast iron with lamellar graphite:

[0039] UHPC grade e80 also exhibits a higher specific stiffness (28.6 kNm / g) than steel (26.8 kNm / g) and polymer concrete (16.7 kNm / g). Specific stiffness refers to the ratio of Young's modulus to density.

[0040] It is particularly advantageous if the weight ratio between the machine frame and the rotor, i.e. the ratio of the mass of the machine frame to the mass of the rotor, is significantly greater for a machine frame made of UHPC (weight ratio between machine frame and rotor greater than 2, in particular = 2.4) than for a machine frame made of steel (weight ratio between machine frame and rotor = 0.9), whereby both machine frames have the same enclosed volume.

[0041] The machine frame 100 can have a substantially symmetrical, frame-like basic geometry. It comprises two longitudinal beams 101, 102 running parallel to one another, which can be integrally connected to one another by a first cross beam 103 and a second cross beam 104, forming a frame-like basic structure of the machine frame 100. Semicircular or more semicircular recesses 105, 106 are formed in the two cross beams 103, 104, respectively.

[0042] The two recesses 105, 106 are each intended to accommodate a lower section—here, approximately the lower half—of the drum's bearings. For this purpose, metal plates 107a, b, 108a, b, for example, can be embedded into the respective solid cross members 103, 104 on both sides of the respective recesses 105, 106 as connecting elements. Fasteners such as threaded holes can be incorporated into the respective metal plates 107a, b, 108a, b, through which the respective bearing can be firmly screwed to the machine frame 100.

[0043] A semi-truncated cone-shaped recess 109 can be introduced between the two transverse beams 103, 104, which is intended to accommodate the rotor, so that the rotor, in the assembled state, lies to a significant extent—here approximately half—in the machine frame 100. Below the recess 109 is a base plate (not shown here), which is integrally connected to the two longitudinal beams 101, 102 and the two transverse beams 103, 104.

[0044] In the area of ​​the recess 109, a plurality of transverse ribs 110a, b, c, d can be formed. The transverse ribs 110a, b, c, d can also be integrally connected to the two longitudinal beams 101, 102. A semicircular recess 111a, b, c, d is also formed in each of the transverse ribs 110a, b, c, d.

[0045] In the respective longitudinal beam 101, 102, several connecting elements such as metal plates 112, 113 are embedded on the upper side, in each of which fastening means such as threaded holes are introduced, through which the hood 2 can be firmly connected to the machine frame 100.

[0046] The respective longitudinal beam 101, 102 can be extended behind the second transverse beam 104 and each provided with a step, so that the respective longitudinal beam 101, 102 continues at a lower height than the support beam 114, 115 for the drive device 4. The two support beams 114, 115 can be integrally connected to one another by a third transverse beam 116. The third transverse beam 116 can be arranged parallel to the other two transverse beams 103, 104.

[0047] The respective support beam 114, 115 can extend behind the third cross beam 116 in a cantilever-like manner with a free end 117, 118. One or more, in this case two, connecting elements, such as metal plates 119a, b, 120a, b, can be mounted or cast onto the upper side of the respective support beam 114, 115. Holes can be provided in the connecting elements, such as metal plates 119a, b, 120a, b, as fastening means for attaching the drive device 4 to the machine frame 100 using corresponding fastening elements.

[0048] It should be noted at this point that the machine frame 100 can be realized as a solid, solid concrete frame. Accordingly, the machine frame 100 has cast-in or attached metal parts 107a, b, 108a, b, 112, 113, 119a, b, 120a, b, which are intended solely for accommodating connecting parts of the rotor and the like. The metal parts 107a, b, 108a, b, 112, 113, 119a, b, 120a, b do not serve as formwork for the concrete.

[0049] The solid-bowl screw centrifuge 1 with the machine frame 100 made of the preferred UHPC with the described high specific stiffness can run more smoothly due to its higher weight compared to a steel machine frame. At the same time, due to the higher specific stiffness, it has a significantly higher natural frequency compared to a steel machine frame. This further contributes to the smooth running of the solid-bowl screw centrifuge 1 with the UHPC machine frame 100. An exemplary test resulted in an increase in the natural frequency of the machine frame from 110 Hz to 175 Hz compared to a conventional metal machine frame. Furthermore, this test resulted in a 30% reduction in vibration velocity and a reduction in the sound pressure level by more than 3 dB(A).

[0050] Particular advantages of the machine frame 100 made of UHPC are therefore: a low-vibration and quiet-running solid-bowl screw centrifuge 1, a simple structural vibration decoupling of the machine frame 100 from the rotor and / or the substrate, ideally complete elimination of additional decoupling elements, a simplification of the construction due to the higher dynamic rigidity of the machine frame 100 made of UHPC, a potential for increasing the rotor speed by increasing the natural frequency, which would result in an increase in the performance of the solid-bowl screw centrifuge 1, and a resource-saving and thus sustainable production of the machine frame 100 made of UHPC.

[0051] List of reference symbols

[0052] 1 solid bowl screw centrifuge

[0053] 2 hood

[0054] 3 Inlet line

[0055] 4 Drive device

[0056] 5 Drive motor

[0057] Machine base

[0058] 100 machine frame

[0059] 101 , 102 Longitudinal beam

[0060] 103, 104 cross member

[0061] 105, 106 recess

[0062] 107a, b metal plate

[0063] 108a, b metal plate

[0064] 109 Deepening

[0065] 110a, b, c, d transverse rib

[0066] 111a, b, c, d recess

[0067] 112, 113 metal plate

[0068] 114, 115 supporting beam

[0069] 116 Crossbeam

[0070] 117, 118 free end

[0071] 119a, b metal plate

[0072] 120a, b metal plate

[0073] Su Suspension

[0074] Fe solid phase

[0075] Fl liquid phase

Claims

Claims 1. Solid bowl centrifuge for processing a suspension Su in a centrifugal field, wherein the suspension Su is separated into at least two phases in the solid bowl centrifuge, with a) a machine frame (100), b) a rotor rotatably mounted in the machine frame (100), which rotor has at least one drum rotatable about a rotation axis d, and c) a drive device (4) with which the drum can be rotated, characterized in that d) the machine frame (100) consists entirely or substantially of UHPC.

2. Solid bowl centrifuge according to claim 1, characterized in that the machine frame (100) is designed as a solid solid concrete frame which consists entirely or substantially of UHPC except for connecting elements, in particular metal parts for receiving corresponding connecting parts.

3. Solid bowl centrifuge according to claim 1 or 2, characterized in that the UHPC has a specific stiffness > 28 kNm / g, in particular = 28.6 kNm / g.

4. Solid bowl centrifuge according to one of the preceding claims, characterized in that the UHPC has an elastic modulus between 60,000 and 100,000 N / mm 2 , especially 80,000 N / mm 2 and a density between 2,500 and 3,000 kg / m 3 , in particular 2,800 kg / m 3 has.

5. Solid bowl centrifuge according to one of the preceding claims, characterized in that the weight ratio between machine frame and rotor is greater than 2 and in particular is 2.

4.

6. Solid bowl centrifuge according to one of the preceding claims, characterized in that it further comprises a screw arranged in the drum which is rotatable relative to the rotatable drum, preferably at a differential speed, so that it is designed as a solid bowl screw centrifuge (1).

7. Solid bowl centrifuge according to one of the preceding claims, characterized in that the machine frame (100) has a substantially frame-like basic geometry.

8. Solid bowl centrifuge according to one of the preceding claims, characterized in that the machine frame (100) has two longitudinal beams (101, 102) running parallel to one another, which are integrally connected to one another by a first transverse beam (103) and a second transverse beam (104).

9. Solid bowl centrifuge according to claim 8, characterized in that in the two transverse beams (103, 104) there are formed exactly or approximately semicircular recesses (105, 106) which are intended to receive a first part of the bearings of the drum.

10. Solid bowl centrifuge according to claim 9, characterized in that on both sides of the respective recess (105, 106) a metal plate (107a, b, 108a, b) is embedded in the respective solid cross member (103, 104), wherein fastening means such as threaded holes are introduced into the respective metal plate (107a, b, 108a, b) through which the respective bearing can be screwed to the machine frame (100).

11. Solid bowl centrifuge according to one of claims 6 to 10, characterized in that a semi-truncated cone-shaped recess (109) is provided between the two transverse beams (103, 104), which recess is intended to receive a part of the rotor, so that the rotor, in the assembled state, is immersed in the machine frame (100).

12. Solid bowl centrifuge according to claim 11, characterized in that in the region of the recess (109) a base plate is formed which is connected in one piece to the two longitudinal beams (101, 102) and the two transverse beams (103, 104) and / or that in the region of the recess (109) transverse ribs (110a, b, c, d) are formed, wherein the transverse ribs (110a, b, c, d) are also connected in one piece to the two longitudinal beams (101, 102) and that in each of the transverse ribs (110a, b, c, d) a semicircular recess (111 a, b, c, d) is formed.

13. Solid bowl centrifuge according to one of claims 5 to 12, characterized in that a plurality of connecting elements - in particular metal plates (112, 113) - are embedded in the upper side of the respective longitudinal beam (101, 102), into which fastening means such as threaded bores can be introduced.

14. Solid bowl centrifuge according to one of claims 6 to 13, characterized in that the respective longitudinal beam (101, 102) is extended behind the second transverse beam (104) and is preferably provided with a step, so that the respective longitudinal beam (101, 102) is continued as a supporting beam (114, 115) for the drive device (4).

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