Solid bowl centrifuge
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- GEA WESTFALIA SEPARATOR GROUP
- Filing Date
- 2024-06-14
- Publication Date
- 2026-04-29
AI Technical Summary
Existing solid bowl screw centrifuges are complex and costly, making them unsuitable for low-throughput applications, particularly in laboratory settings, and require frequent cleaning and maintenance.
A solid bowl screw centrifuge design featuring a rotor with a rotatable drum and screw, supported by magnetic bearing units for levitation and differential speed control, made from non-magnetic materials, allowing for single-use and hermetic operation with integrated magnetic drive systems, eliminating the need for separate drives and reducing maintenance.
The design results in a compact, cost-effective, and simple structure suitable for low-throughput applications, enabling efficient separation and processing of suspensions with reduced maintenance and energy loss, and facilitating quick rotor replacement.
Smart Images
Figure EP2024066544_26122024_PF_FP_ABST
Abstract
Description
[0001] Solid bowl screw centrifuge
[0002] The invention relates to a solid bowl screw centrifuge according to the preamble of claim 1.
[0003] A solid-bowl screw centrifuge—also known as a decanter in technical terms—can separate a solid phase from a suspension. Optionally, the suspension, once clarified of solids in this way, can be separated into different liquid phases in a design with two liquid outlets. Solid-bowl screw centrifuges are ideally suited to processing relatively high solid concentrations in the feed stream, are comparatively robust, achieve excellent separation results, and ensure effective drying of the solids. In this context, "solid" refers to a solid that has been dehydrated as much as possible, although in practice, it often still contains so much residual moisture that it behaves like sludge.
[0004] Known solid-bowl screw centrifuges with a frame that is non-rotatable or non-rotating during operation have a rotatable or rotating rotor, which in turn contains a bowl and, within it, a screw that rotates at a speed different from that of the bowl. Solids discharge openings are provided in a conical section of the bowl for discharging the solids.
[0005] For solid-bowl screw centrifuges with low throughput (i.e., suitable for use under laboratory conditions), it is desirable that they be as simple and cost-effective as possible. Furthermore, a hermetic feed of the suspension to be separated and a hermetic discharge of both the at least one or more liquid phases are desirable.
[0006] The aim of the invention is to implement these requirements in the simplest possible way.
[0007] The invention solves this problem by the subject matter of claim 1. Accordingly, a solid bowl screw centrifuge for processing a suspension Su in a centrifugal field is provided, comprising a housing and a rotor rotatably mounted in the housing, which rotor has at least the following:
[0008] - a rotatable drum with a rotational axis, the drum having a cylindrical section and a conical section, - an inlet pipe projecting into the drum and arranged concentrically to the rotational axis D, through which the suspension Su to be processed can be guided into a separation chamber of the drum,
[0009] - at least one liquid drain,
[0010] - at least one solids discharge,
[0011] - a screw arranged in the drum, which can rotate relative to the rotating drum at a differential speed, wherein
[0012] - a bearing and drive system of the rotor, which has at least a first magnetic bearing unit and a second magnetic bearing unit, wherein the first magnetic bearing unit provides a radially and axially acting levitronic bearing for the drum and the second magnetic bearing unit provides a radially and axially acting levitronic bearing for the screw,
[0013] - wherein at least the screw is mounted in the drum so that it can slide and rotate relative to the drum, and
[0014] - wherein the drum, the screw and the inlet and outlet system are each made entirely or predominantly of a non-magnetic material, for example of plastic and / or a plastic composite material and / or of titanium.
[0015] This creates a solid-bowl screw centrifuge with a simple and cost-effective design, which, thanks to the particularly advantageous interaction of the claimed features, is very well suited for processing even small amounts of suspension and is therefore surprisingly well suited for laboratory conditions. The rotor, including the inlet and outlet systems, are particularly suitable for single use. This has the advantage that, thanks to the intended single use of the rotor, including the inlet and outlet systems, the bowl and screw no longer need to be cleaned. The fact that the screw is mounted in the bowl so that it can slide and rotate relative to it sufficiently ensures that no solid deposits can form on the inside of the bowl during single use.The proposed bearing system with two magnetic levitronic bearings, which can be easily assembled and disassembled, thus supports the single use of the rotor and can be easily and advantageously developed into a drive system.
[0016] It is preferred—but not mandatory—that the one or two or more liquid outlets be arranged in the drum, in particular in the cylindrical section of the drum, and / or that the at least one solids outlet be arranged in the drum, in particular in the conical section or as an extension of the conical section of the drum. In a particularly preferred embodiment of the invention, the respective magnetic bearing unit comprises a rotor unit and a stator unit. This creates the prerequisite for a compact levitronic drive of the rotor of the solid-bowl screw centrifuge in a structurally simple manner.In a further particularly preferred embodiment of the invention, it is provided that the stator unit of the respective magnetic bearing unit is controlled by a controller such that the respective magnetic bearing unit generates a motor torque, so that a first drive and magnetic bearing device is formed from the first magnetic bearing unit, and a second drive and magnetic bearing device is formed from the second magnetic bearing unit. Due to the advantageous integration of the "rotatable bearing" and "drive" functions into the magnetic bearing units, a separate drive for the solid-bowl screw centrifuge can be omitted. This results in a structurally simple drive design that does not require a gear and is therefore particularly compact.
[0017] It can then be provided that a control device controls the stator unit of the respective magnetic bearing unit in such a way that the respective magnetic bearing unit generates a motor torque. For this purpose, the control device is equipped with a corresponding computer program that performs the necessary computational operations, and the control device is in a corresponding operative connection with the magnetic bearing units.
[0018] In a further preferred embodiment of the invention, it is provided that the first drive and magnetic bearing device formed by the first magnetic bearing unit, preferably between the frame and the drum, drives the drum, in particular on the solids discharge side, and a second drive and magnetic bearing device formed by the second magnetic bearing unit, preferably between the frame and the screw, drives the screw, in particular on the liquid discharge side. This creates a bearing and drive system for the solid bowl screw centrifuge that advantageously enables rapid replacement of the single-use rotor, since the respective rotor units remain on the drum and screw to be replaced and can just as easily be newly installed on the drum and screw to be installed.
[0019] Furthermore, in another particularly preferred embodiment of the invention, the speed and direction of rotation for both drive and magnetic bearing devices can be adjusted independently of one another, so that the differential speed between the drum and the screw can be generated. This allows the differential speed between the drum and the screw to be generated particularly simply and in a space-saving manner.
[0020] Furthermore, in another particularly preferred embodiment of the invention, the bearing and drive system of the solid-bowl screw centrifuge comprises a further, third magnetic bearing unit between the drum and the frame, wherein the third magnetic bearing unit comprises a rotor unit and a stator unit, so that a third drive and / or magnetic bearing device can be formed from the third magnetic bearing unit. This allows for stabilization of the bearing and / or an increase in the torque of the drum drive of the solid-bowl screw centrifuge in a particularly space-saving manner.
[0021] In this context, a further particularly preferred embodiment of the invention provides that the rotor unit of the third magnetic bearing unit is positioned on an outer wall of the drum in the region of the cylindrical section of the drum. This also makes the third magnetic bearing unit easy to assemble and disassemble, thus advantageously enabling and supporting the single-use of the rotor.
[0022] It is also provided in a further particularly preferred embodiment of the invention that the screw and the drum are mounted so as to be rotatable relative to one another in a sliding manner over or in the region of the screw flight.
[0023] This creates a plain bearing between the drum and the screw that is easy to construct, assemble and disassemble, eliminating the need for additional bearings or magnetic bearings.
[0024] Furthermore, in another particularly preferred embodiment of the invention, a gap between the drum and the screw flights of the screw is designed such that a lubricating film can form, with the suspension Su to be separated serving as the lubricant. This makes the generation of the lubricating film particularly simple in design and ensures long-term, reliable operation of the plain bearing between the drum and the screw. Furthermore, a suitably narrow gap ensures that no or only minimal solid residues can accumulate on the inner wall of the drum.
[0025] Furthermore, in another particularly preferred embodiment of the invention, the solids discharge is arranged axially in the center of the drum. This advantageously results in only low shear forces during solids discharge and a lower energy loss due to the solids or sludge emerging from the rotating drum.
[0026] In a further particularly preferred embodiment of the invention, it is provided that the rotor is hermetically sealed, ie all inlets and outlets of the rotor are sealed from the housing and the environment.
[0027] The invention also provides the interchangeable unit of claim 19, which optionally further comprises one or more of the features of subclaims 2 to 18.
[0028] This replaceable unit can be designed as a replaceable insert for the frame. This replaceable insert essentially comprises the rotor, but it can also include one or more non-rotating elements on or within the rotor that do not rotate during operation—particularly elements that come into contact with the product, such as stationary elements of the inlets and outlets or discharges, as well as any hose connections to these elements.
[0029] The respective interchangeable insert can therefore also have hoses and, if applicable, nozzles which can be connected to other lines (not shown here) and containers such as bags, tanks, pumps and the like.
[0030] The inlet pipe and fluid outlet are also preferably made of plastic. The inlet pipe can be stationary or rotating during operation.
[0031] Further advantageous embodiments of the invention can be found in the subclaims.
[0032] The invention is described in more detail below with reference to exemplary embodiments and the drawings. They show:
[0033] Figure 1: a schematic view in section of a rotor of a solid bowl screw centrifuge according to the invention with a horizontal axis of rotation, which is rotatably arranged on a machine frame;
[0034] Figure 2: a schematic sectional view of a rotor of another solid bowl screw centrifuge according to the invention with a vertical axis of rotation, which is rotatably arranged on a machine frame.
[0035] The following description of the figures describes two embodiments of solid-bowl screw centrifuges. The individual features of these embodiments—the dimensions, bearing arrangements, and sealing arrangements mentioned below are purely examples—can also be used in the respective other embodiments and in those not shown, and are also suitable as advantageous embodiments and further developments of the subject matter described in one or more of the main and subclaims.
[0036] Fig. 1 and Fig. 2 each show a solid-bowl screw centrifuge 1—also called a "decanter"—for processing a product in the form of a suspension Su in a centrifugal field. The decanter has a frame 100 that is non-rotatable or non-rotating during operation—which can preferably be designed as a type of housing—and a rotor 200 that is rotatable or rotating during operation.
[0037] In Fig. 1, the rotor 200 has a rotatable drum 210 with a horizontal axis of rotation D. However, the axis of rotation D can also be oriented differently, in particular vertically, in space, as shown in Fig. 2. The embodiments of Figs. 1 and 2 can - but do not have to - be identical except for the axis of rotation.
[0038] The drum 210 is preferably designed as a solid-bowl drum. In the drum 210, which rotates during operation of the solid-bowl screw centrifuge 1, an incoming suspension is separated into at least one liquid phase (F1) and one solid phase (Fe), or the suspension of solids (Fe) is clarified.
[0039] The rotor 200 also has a screw 230 arranged in the drum 210, the rotational axis of which coincides with the rotational axis D of the drum 210. The screw 230 has a screw flight 231 formed externally on a screw hub 232 and projecting radially or substantially radially therefrom. The screw 230 is preferably constructed in one piece, but it can be constructed in multiple pieces. For example, it can be assembled from the screw hub 232 and the screw flight 231.
[0040] The screw flights 231 can have a progressive or degressive pitch. The pitch can be linear or have sections with varying pitches. Depending on the pitch direction of the screw flights 231, the screw 230 rotates in the same direction as or opposite to the drum's rotation direction.
[0041] The drum 210 has a cylindrical portion 211 and preferably has a conical portion 212 axially adjoining thereto. The cylindrical portion 211 is closed here by a substantially radially extending drum cover 213. In the conical portion 212, the drum 210 is preferably conical on the inside and outside (relative to the drum shell).
[0042] One or more liquid outlets 214 may be formed in or on the drum cover 213 or at the cylindrical end of the drum toward this drum cover 213. These can be designed in various ways, such as openings in the drum cover 213 that function as a kind of overflow weir, or in another way, such as a peeling disc 215—also called a "grabber" in technical terms—as shown in Fig. 1 and Fig. 2.
[0043] At least one solids discharge 216 is formed as an extension of the conical section 212 of the drum 210. The solids discharge 216 is arranged axially in the center of the drum 210. This advantageously reduces the shear forces in the solids discharge 216.
[0044] An inlet pipe 217, which is arranged concentrically to the axis of rotation D here and is preferably stationary during operation of the solid bowl screw centrifuge 1, projects into the drum 210 and opens into a distribution chamber 218 through which the suspension Su to be processed can be guided radially into a separation chamber 219 of the drum 210.
[0045] The distribution chamber 218 can, for example, be designed with small tubes 223, so that the suspension Su is guided, for example, into the center of the separation chamber 219. Alternatively, the inlet pipe 217 can also be designed to rotate. The inlet pipe 217 can - as shown in Fig. 1 - either be guided into the drum 210 from the side of the cylindrical drum section 211 or it can be guided into the drum 210 from the side of the conical drum section 212. It is considered part of the rotor here.
[0046] The distribution chamber 218 is arranged here in the drum 210 in the cylindrical drum section 211 and is positioned axially approximately in the center of the cylindrical drum section 211, to which the conical drum section 212 adjoins. The distribution chamber 218 can also be positioned at a different location, in particular in the cylindrical drum section 211 and there preferably—but not necessarily—just before the transition to the conical drum section 212.
[0047] The inlet pipe 217 is designed concentrically with the impeller disc 218. A impeller disc chamber 220, which accommodates the impeller disc 215, is designed on the screw hub 232, with inlet openings 221 for the liquid phase Fl near the screw hub 232. The liquid phase Fl can thus flow into the rotating impeller disc chamber 220 and is discharged from there into the liquid outlet 214 by means of the impeller disc 215. In the process, part of the energy of the rotating liquid is converted into pressure. The impeller disc chamber 220 is preferably sealed from the screw hub 232 by a seal 222. The seal 222 can be designed as a mechanical seal. The screw hub 232 is sealed from the liquid outlet 214 by a further seal 225. The seal 225 can also be designed as a mechanical seal. The peeling disc can be designed to be stationary during operation.
[0048] The screw 230 here also has a cylindrical section 233 and an axially adjoining conical section 234. It is arranged within the drum 210. During operation, the screw 230 can be rotated at a speed different from that of the drum 210. The solids Fe deposited on the inner wall of the drum during operation are transported by the screw 230 toward the solids discharge 216 and ejected from the drum 210.
[0049] The transition of the Fe solids from the rotating drum to the non-rotating solids discharge 216 can be achieved using a suitable seal 224, which can be designed as a mechanical seal. A positive or negative backpressure can be generated in the non-rotating discharge system by a pump (not shown).
[0050] The seals 222, 224 and 225 seal the inlet 217 and the outlets 214, 216 and thus the rotor 200 is hermetically sealed so that pressures in the rotor of up to 6 bar can be handled.
[0051] The drum 210, the screw 230, and the inlet and outlet systems 217, 214, 216 are each made entirely or predominantly of a plastic or a plastic composite material. Alternatively, the drum 210 can also be made of a non-magnetic material, such as titanium.
[0052] As a result, the entire rotor 200 of the solid-bowl screw centrifuge 1 is designed for single use. The bowl 210 and the screw 230, as well as the inlet and outlet systems 217, 214, 216, therefore do not need to be cleaned after use, but can be disposed of thermally, for example.
[0053] The ratio L / d between a total length L and an inner diameter d of the drum 210 is preferably between 3 and 7. The inner diameter d of the drum 210 is preferably between 50 and 150 mm. The cone angle α of the screw 230 and the inner wall of the drum is preferably between 4 and 16°.
[0054] A bearing and drive system 250 of the rotor 200 has at least a first magnetic bearing unit 251 and a second magnetic bearing unit 252. The two magnetic bearing units 251, 252 are designed to absorb both axial and radial forces (relative to the rotational axis D of the drum 210) of the drum 210 and the worm 230, respectively.
[0055] The respective magnetic bearing unit 251, 252 each has a rotor unit 251a, 252a and a stator unit 251b, 252b. The respective rotor unit 251a, 252a can be rotationally fixedly coupled to the drum 210 or the worm 230, respectively, and the respective associated stator unit 251b, 252b can be arranged on the frame 100, preferably radially outside the respective rotor unit 251b, 252b.
[0056] The first magnetic bearing unit 251 provides a radially and axially acting levitronic bearing for the drum 210 and the second magnetic bearing unit 252 provides a radially and axially acting levitronic bearing for the screw 230.
[0057] Furthermore, it is provided that a control device (not shown here) controls the stator unit 251b, 252b of the respective magnetic bearing unit 251, 252 such that the respective magnetic bearing unit 251, 252 generates a motor torque. For this purpose, the control device is provided with a corresponding computer program that performs the necessary computational operations, and the control device is operatively connected to the magnetic bearing units 251 and 252. The control device can be the one that also handles the remaining control and regulation of the decanter or a separate control unit.
[0058] A first drive and magnetic bearing device formed by the first magnetic bearing unit 251 drives the drum 210 on the solids discharge side 216, and a second drive and magnetic bearing device formed by the second magnetic bearing unit 252 drives the screw 230 on the liquid discharge side 214.
[0059] Optionally, the bearing and drive system 250 of the solid-bowl screw centrifuge 1 can include a further, third magnetic bearing unit 253 between the drum 210 and the frame 100, as shown in Fig. 1 and Fig. 2. The third magnetic bearing unit 253 can be constructed analogously to the first magnetic bearing unit 251 and the second magnetic bearing unit 252 and can then also include a rotor unit 253a and a stator unit 253b. In this respect, a third drive and / or magnetic bearing device can be formed from the third magnetic bearing unit 253 if required.
[0060] The rotor unit 253a of the third magnetic bearing unit 253 can be placed around the outer circumference of the drum 210. It is then preferably positioned in the region of the cylindrical portion 211 of the drum 210. The stator unit 253b is positioned accordingly on the housing.
[0061] Such bearing and drive devices are described, for example, in DE 10 2017 128 027 A1.
[0062] They can also be used within the scope of this document. For example, a first levitronic motor can be used to drive the drum 210, which simultaneously magnetically supports the drum 210 radially and axially. Furthermore, a second levitronic motor can be provided to drive the screw 230, which simultaneously magnetically supports the screw 230 radially and axially.
[0063] This creates an advantageously simple bearing and drive system 250 for the solid bowl screw centrifuge 1, which in particular also enables a quick change of the single-use rotor 200, since the respective rotor elements 251a, 252a simply remain on the bowl 210 and the screw 230 to be replaced (single-use component) and are just as easily already mounted on the bowl 210 and the screw 230 to be installed.
[0064] The control device is preferably designed such that the speed and direction of rotation for the two or more drive and magnetic bearing devices 251, 252, 253 can be adjusted independently of one another, so that a differential speed can be generated between the drum 210 and the screw 230. The screw flight 231 on the screw hub 232 and the generated differential speed transport the solid Fe, which is centrifugally driven radially outward in the drum 210, to the solids discharge 216.
[0065] The screw 230 can be mounted in the drum 210 via the screw flights 231 for sliding movement and rotation. For this purpose, there can be such a clearance between the inner wall of the drum 210 and the screw flights 231 that the screw 230 can rotate relative to the drum 210, but can also slide into contact with the inner circumference of the drum 210, preferably in its conical section 211. Due to this type of mounting of the screw in the drum 210, no additional rolling bearing is required or need not be provided on the liquid outlet 214 side, and for the screw 230 on the solids discharge 216 side, no additional bearing is required or need not be provided there. The screw 230 is preferably only slide-mounted towards the conical side of the drum 210, which is simple and advantageous. If necessary, the drum can also be mounted on roller bearings towards the drum cover.
[0066] Further advantages arise from the optional use of the following type of bearing of the screw relative to the drum.
[0067] For example, a gap between the inner wall of the drum 210 and the screw flights 231 can be dimensioned such that a type of lubricating film can form in this gap. The suspension Su to be separated serves as the lubricant. This lubricating film allows the screw 230 to rotate within the drum 210 with low friction. This prevents solid deposits from forming on the inside of the drum during operation.
[0068] During operation of the solid-bowl screw centrifuge 1, the rotational speed of the drum 210 is preferably in a range between 1000 rpm and 9000 rpm. The screw 230 rotates slightly faster or slower than the drum 210. The resulting differential speed is preferably between 1 rpm and 200 rpm. The volume flow of the suspension Su to be processed in the solid-bowl screw centrifuge 1 can preferably be between 10 l / h and 400 l / h.
[0069] The decanters shown enable the production of a replaceable insert, in which all product-contacting components can preferably be made of plastic or other non-magnetic materials that can be disposed of after a single use or recycled. Cleaning after use is thus eliminated. The separator and its operation can thus be implemented cost-effectively.
[0070] 1 solid bowl screw centrifuge
[0071] 100 frames
[0072] 200 rotor
[0073] 210 Drum
[0074] 211 cylindrical section
[0075] 212 conical section
[0076] 213 Drum cover
[0077] 214 Fluid drain
[0078] 215 Peeling disc
[0079] 216 Solids discharge
[0080] 217 Inlet pipe
[0081] 218 Distribution chamber
[0082] 219 Separation room
[0083] 220 Peeling disc chamber
[0084] 221 Inlet opening
[0085] 222 Seal
[0086] 223 pipe
[0087] 224 Seal
[0088] 225 Seal
[0089] 230 snail
[0090] 231 snail egg
[0091] 232 Worm hub
[0092] 233 cylindrical section
[0093] 234 conical section
[0094] 250 drive and bearing system
[0095] 251 magnetic bearing unit
[0096] 251a rotor unit
[0097] 251 b Stator unit
[0098] 252 magnetic bearing unit
[0099] 252a rotor unit
[0100] 252b Stator unit
[0101] 253 magnetic bearing unit
[0102] 253a rotor unit
[0103] 253b Stator unit D Rotation axis d Diameter
[0104] L length
[0105] Su Suspension Fe Solids
[0106] Fl liquid phase
Claims
Claims 1. Solid bowl screw centrifuge (1) for processing a suspension Su in a centrifugal field with a frame (100) and a rotor (200) rotatably mounted in the frame (100), which has at least the following: a) a rotatable drum (210) with an axis of rotation (D), wherein the drum (210) has a cylindrical section (211) and a conical section (212), b) an inlet pipe (217) projecting into the drum (210) and arranged concentrically to the axis of rotation D, through which the suspension Su to be processed can be guided into a separation space (219) of the drum (210), c) at least one liquid outlet (214), d) at least one solids discharge (216), e) a screw (230) arranged in the drum (210) and rotatable at a differential speed relative to the rotatable drum (210), characterized in that f) a Bearing and drive system (250) of the rotor (200), which has at least a first magnetic bearing unit (251) and a second magnetic bearing unit (252),wherein the first magnetic bearing unit (251) provides a radially and axially acting levitronic bearing for the drum (210) and the second magnetic bearing unit (252) provides a radially and axially acting levitronic bearing for the screw (230), g) wherein at least the screw (230) is mounted in the drum (210) so as to be slidably and rotatably movable relative thereto, and h) wherein at least the drum (210), the screw (230) and the inlet and outlet system (217, 214, 216) are each made entirely or predominantly from a non-magnetic material, in particular from plastic and / or a plastic composite material and / or from titanium.
2. Solid bowl screw centrifuge (1) according to claim 1, characterized in that the respective magnetic bearing unit (251, 252) has a rotor unit (251a, 252a) and a stator unit (251b, 252b).
3. Solid bowl screw centrifuge (1) according to claim 2, characterized in that the stator unit (251 b, 252b) of the respective magnetic bearing unit (251 , 252) is controlled by a control system in such a way that the respective magnetic bearing unit (251 , 252) generates a motor torque, so that from the a first drive and magnetic bearing device is formed from the first magnetic bearing unit (251) and a second drive and magnetic bearing device is formed from the second magnetic bearing unit (252).
4. Solid bowl screw centrifuge (1) according to one of the preceding claims, characterized in that the first drive and magnetic bearing device formed by the first magnetic bearing unit (251) drives the drum (210) and a second drive and magnetic bearing device formed by the second magnetic bearing unit (252) drives the screw (230).
5. Solid bowl screw centrifuge (1) according to claim 4, characterized in that the first drive and magnetic bearing device formed by the first magnetic bearing unit (251) on the side of the solids discharge (216) drives the drum (210) and a second drive and magnetic bearing device formed by the second magnetic bearing unit (252) on the side of the liquid outlet (214) drives the screw (230).
6. Solid bowl screw centrifuge (1) according to one of the preceding claims, characterized in that a control device is provided for controlling and / or regulating the two or more drive and magnetic bearing devices (251, 252).
7. Solid bowl screw centrifuge (1) according to one of the preceding claims, characterized in that the speed and direction of rotation for both drive and magnetic bearing devices for the drum (210) and the screw (230) can be adjusted independently of one another using the control device in order to generate the differential speed between the drum (210) and the screw (230).
8. Solid bowl screw centrifuge (1) according to one of the preceding claims, characterized in that the rotational speed of the drum (210) during operation of the solid bowl screw centrifuge (1) is in a range between 1000 rpm and 9000 rpm.
9. Solid bowl screw centrifuge (1) according to claim 6, characterized in that the differential speed between the drum (210) and the screw (230) is preferably between 1 1 / min and 200 1 / min.
10. Solid bowl screw centrifuge (1) according to one of the preceding claims, characterized in that the bearing and drive system (250) of the Solid bowl screw centrifuge (1) has a further, third magnetic bearing unit (253), in particular between the drum (210) and the frame (100).
11. Solid bowl screw centrifuge (1) according to claim 9, characterized in that the rotor unit (253a) of the third magnetic bearing unit (253) is positioned in the region of the cylindrical portion (211) of the drum (210).
12. Solid bowl screw centrifuge (1) according to one of the preceding claims, characterized in that the screw (230) is mounted in the drum (210) via the screw flight (231) in a sliding and rotatable manner.
13. Solid bowl screw centrifuge (1) according to one of the preceding claims, characterized in that the drum (210) is mounted in a sliding and rotatable manner via the screw flight (231).
14. Solid bowl screw centrifuge (1) according to one of the preceding claims, characterized in that a gap between the drum (210) and the screw flights (231) of the screw (230) is designed such that a lubricating film can form from the suspension Su, so that the suspension Su to be separated serves as a lubricant.
15. Solid bowl screw centrifuge (1) according to one of the preceding claims, characterized in that the at least one liquid outlet (214) is arranged in the cylindrical section (211) of the drum (210) and / or that the at least one solids outlet (216) is arranged in the conical section or in an extension of the conical section (212) of the drum (210).
16. Solid bowl screw centrifuge (1) according to one of the preceding claims, characterized in that the solids discharge (216) is arranged axially in the center of the drum (210).
17. Solid bowl screw centrifuge (1) according to one of the preceding claims, characterized in that the rotor (200) is hermetically sealed.
18. Solid bowl screw centrifuge (1) according to one of the preceding claims, characterized in that the volume flow of the suspension Su to be processed in the solid bowl screw centrifuge (1) is adjustable between 10 l / h and 400 l / h.
19. Replaceable unit for a solid bowl screw centrifuge (1) according to one of the preceding claims, which has at least the following: a) a rotatable drum (210) of a rotor (200) with a rotational axis (D), the drum (210) having a cylindrical section (211) and a conical section (212), b) an inlet pipe (217) projecting into the drum (210) and arranged concentrically to the rotational axis D, through which inlet pipe the suspension Su to be processed can be guided into a separation chamber (219) of the drum (210), c) at least one liquid outlet (214), d) at least one solids outlet (216), e) a screw (230) of the rotor (200) which is rotatable relative to the rotatable drum (210) at a differential speed and is arranged in the drum (210), characterized in that f) a bearing and drive system (250) of the Rotor (200) has at least one rotor unit (251a) of a first magnetic bearing unit (251) and one rotor unit (252a) of a second magnetic bearing unit (252),wherein the first magnetic bearing unit (251) provides a radially and axially acting levitronic bearing for the drum (210) and the second magnetic bearing unit (252) provides a radially and axially acting levitronic bearing for the screw (230), g) wherein at least the screw (230) is mounted in the drum (210) so as to be slidably and rotatably movable relative thereto, and h) wherein at least the drum (210), the screw (230) and the inlet and outlet system (217, 214, 216) are each made entirely or predominantly of a non-magnetic material, in particular of plastic and / or a plastic composite material and / or of titanium.