Solid bowl screw centrifuge
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- GEA WESTFALIA SEPARATOR GROUP
- Filing Date
- 2024-07-15
- Publication Date
- 2026-05-27
AI Technical Summary
Existing solid bowl screw centrifuges face issues with partial liquid phase removal for analysis, as the centrate, still under pressure in the drum, degasses and forms air bubbles or foam when discharged freely, interfering with analysis technologies like turbidity sensors or camera systems.
A solid bowl screw centrifuge design featuring a non-rotating peeling element positioned at the overflow weir allows for the removal of a partial liquid phase flow under pressure, preventing foam and bubble formation, using a circumferentially closed drain hose or pipe that skims off the liquid before it leaves the rotating system, maintaining its composition and ensuring analysis without interference.
The solution enables the removal of a liquid phase subset under pressure, free from foam and bubbles, allowing for accurate analysis without interference, with the skimmed-off portion being representative of the main stream and potentially returned, while high pressure in the drain pipe prevents gas outgassing, ensuring reliable measurement results.
Smart Images
Figure EP2024069963_23012025_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 called a decanter, can be used to separate a solid phase from a suspension. Optionally, the liquid clarified in this way – provided it contains multiple liquid phases – can be separated into liquid phases of varying density using 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 can often still contain 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 has a bowl and a screw that rotates at a speed different from that of the bowl. Solids discharge openings are generally provided in a conical section of the bowl for discharging the solids.
[0005] If a partial stream of the liquid phase – also known as "centrate" in technical terms – is to be withdrawn for analytical purposes, for example, to determine the degree of turbidity, the problem arises that the centrate, still under pressure in the drum, can expand if it freely exits the drum. This can lead to degassing of air and / or other gases that were trapped in the product or suspension to be clarified. The gas bubbles or foam remain finely dispersed in the centrate, which can cause problems for the analytical technology.
[0006] Appropriate devices for such analysis purposes can be, for example, a turbidity sensor (transmitted or scattered light), a camera system or other optical systems.
[0007] From DE 10 2015 105 988 B3 and DE 39 04 151 A, it is known that the entire centrate stream is discharged from the drum in a non-closed system and then analyzed by an optical system. DE 10 2020 128 804 B4 describes that the centrate exits the drum as a free jet and is then analyzed by an optical system. The technological background is also cited in DE 1 026 692 A, in which flowable phases of different composition are skimmed off with a skimming tube in two axially successive annular chambers of a solid-bowl screw centrifuge.
[0008] When a partial stream of the clarified liquid phase is removed from the drum, this should be done as foam- and bubble-free as possible so that the removed liquid phase can be analyzed without problems by appropriate systems.
[0009] The aim of the invention is to implement this requirement as comprehensively as possible.
[0010] The invention solves this problem by the subject matter of claim 1.
[0011] Accordingly, a solid bowl screw centrifuge is provided for processing a suspension Su in a centrifugal field, with which the suspension Su can be separated into at least one liquid phase Fl and one solid phase Fe, with a housing and a rotor rotatably mounted in the housing, which rotor has at least the following:
[0012] - a rotatable drum with a rotation axis, the drum having a cylindrical section and a conical section,
[0013] - a screw arranged in the drum, which can rotate relative to the rotating drum at a differential speed,
[0014] - an inlet pipe through which the suspension Su to be processed can be fed into a separation chamber of the drum,
[0015] - at least one liquid outlet through which the liquid phase Fl is discharged, wherein the liquid outlet has at least one overflow weir,
[0016] - at least one solids discharge through which the solid phase Fe is discharged;
[0017] - to divert a partial flow fl of the liquid phase Fl, a non-rotating skimming device is arranged in the area of the overflow weir, which is stationary during operation, so that this partial flow fl of the liquid phase Fl can be skimmed off under pressure from the liquid phase flowing through the overflow weir before it leaves the rotating rotor. This allows a partial flow of the clarified liquid phase to be withdrawn from the rotating system under pressure, which remains essentially free of foam and bubbles during and after withdrawal, so that the withdrawn liquid phase can be easily analyzed by appropriate systems.
[0018] This is because the partial stream fl of the liquid phase Fl skimmed off by the skimming device advantageously has the same composition as the liquid phase Fl from which the partial stream fl is skimmed off. The "same composition" refers to the constituents of the liquid phase Fl and their concentrations.
[0019] The invention also provides a method for the centrifugal processing of a suspension Su in a centrifugal field of a solid bowl screw centrifuge, which is designed according to one of the claims related thereto, comprising the following steps:
[0020] A. feeding the solid bowl screw centrifuge with the suspension Su to be processed so that it is separated into at least one liquid phase Fl and one solid phase Fe, and
[0021] B. Skimming off a partial flow fl of the liquid phase Fl through the skimming device in the region of the at least one overflow weir, so that the partial flow fl of the liquid phase Fl leaves the drum through the skimming device under pressure.
[0022] It is preferred that the peeling element be designed in the manner of a circumferentially closed drainage hose or pipe. This design is simple and cost-effective.
[0023] According to a further preferred embodiment, it can advantageously be provided that an inlet opening of the peeling device is positioned upstream of an edge of the overflow weir with respect to the flow direction of the liquid phase Fl. This ensures in a simple manner that a portion of the liquid phase can be removed from the drum before leaving the drum.
[0024] Then, according to a further advantageous optional development, it can be provided that the area upstream of an edge of the overflow weir is designed as a radially inwardly open annular cup, into which the peeling element dips radially with its inlet opening. This makes it structurally particularly simple to remove part of the liquid phase from the drum before it leaves the drum. In a further particularly preferred embodiment of the invention, it is provided that the discharge pipe is bent at an angle and thus has an axial leg oriented parallel to the axis of rotation D and a radial leg oriented perpendicular to the axis of rotation D, which dips into the annular cup without touching it.This creates a skimming device that is easy to manufacture and can be used to skim off the partial flow of the liquid phase under pressure in the rotating system, which itself remains stationary during operation.
[0025] Furthermore, in a further particularly expedient embodiment of the invention, it is provided that an inlet region of the discharge pipe is designed in such a way that the liquid phase Fl rotating in the annular bowl during operation of the solid bowl screw centrifuge is skimmed off through a stationary pipe opening of the radial leg of the discharge pipe in the manner of a centripetal pump.
[0026] According to a further preferred embodiment, it can be provided that the liquid outlet, in particular the overflow weir through which the liquid phase Fl is discharged, is arranged in the cylindrical section of the drum or in a drum cover.
[0027] And according to yet another preferred embodiment, it can be provided that the solids discharge is arranged in the conical section of the drum.
[0028] The screw may preferably also have a cylindrical section and a conical section.
[0029] According to another particularly preferred embodiment of the invention, the skimming of the partial stream can be carried out in such a way that the skimmed partial amount fl of the liquid phase Fl corresponds to 1% to 5% of the liquid phase Fl. Thus, advantageously, only a small portion of the total liquid phase is diverted from the main stream as a partial stream for analysis purposes. This partial amount can be returned to the main stream or the shaft for the liquid phase after analysis.
[0030] Furthermore, in another particularly preferred embodiment of the invention, the skimming of the partial flow is carried out in such a way that the pressure in the discharge pipe is a maximum of 10 bar. This high pressure advantageously prevents gas components trapped in the liquid phase from escaping in the form of bubbles or foam, thus impairing the analysis of the partial amount of the liquid phase.
[0031] Suitable devices or sensors for such analyses can include, for example, a turbidity sensor (transmitted or scattered light), a camera system, or other optical systems suitably positioned in the discharge pipe. The measurement signal can be transmitted to a control unit via a signal line, a data line, or wireless communication. Based on these measured values, the control unit influences the operation of the solid-bowl screw centrifuge. For example, the differential speed can be changed by increasing or decreasing the screw speed. The bowl speed can also be increased or decreased.
[0032] Alternatively, the process parameters can be adjusted based on the above measured values from the control unit. For example, the flow rate (volume per unit time) of the suspension to be clarified can be increased or decreased, or the amount of additives added to the suspension, such as flocculants, coagulants, or demulsifiers, can be adjusted.
[0033] Further advantageous embodiments of the invention can be found in the subclaims.
[0034] 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:
[0035] Figure 1: a schematic sectional view of a rotor of a solid bowl screw centrifuge according to the invention with a horizontal axis of rotation;
[0036] Figure 2: an enlarged detail from Fig. 1 ;
[0037] Figure 3: a schematic view in section of a rotor of a solid-shell
[0038] State-of-the-art screw centrifuge.
[0039] The following description of the figures describes one or more embodiments of a solid-bowl screw centrifuge. The individual features of these embodiments can also be combined with embodiments not shown or with further features disclosed elsewhere in this document other than the description of the figures, and are also suitable as advantageous embodiments of the subject matter described in one or more of the main and subordinate claims.
[0040] First, the construction of Fig. 3 will be described, which is further developed according to the invention in Figs. 1 and 2.
[0041] Fig. 3 shows a solid bowl screw centrifuge with 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.
[0042] 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 space, particularly vertically. The rotor 200 also includes a screw 230 arranged in the drum 210, the axis of rotation of which coincides with the axis of rotation D of the drum 210.
[0043] The drum 210 may have a cylindrical portion 211 and preferably a conical portion 212 axially adjoining thereto. The cylindrical portion 211 may be closed by a substantially radially extending drum cover 213. In the conical portion 212, the drum 210 may preferably be conical on the inside and outside (relative to the drum shell).
[0044] The screw 230 may have a cylindrical portion 231 and preferably a conical portion 232 axially adjoining it. It is arranged within the drum 210. During operation, the screw 230 may be rotated at a speed different from that of the drum 210.
[0045] The worm 230 can then have a worm screw 233 and a worm hub 234. The worm 230 can, but does not have to, be constructed in one piece; it can also be assembled from two or more elements, such as the worm hub 234 and the worm screw 233.
[0046] The screw flight 233 can have a linear, progressive, or degressive pitch. Depending on the pitch direction of the screw flight 233, the screw 230 rotates in the same direction as or opposite to the direction of drum rotation. An inlet pipe 214, aligned concentrically to the rotation axis D here, extends into the drum 210 and opens into a distributor 215 through which a suspension Su to be processed can be guided radially into a separation chamber 216 of the drum 210. The inlet pipe 214 can either be guided from the side of the cylindrical drum section 211 into the drum 210 or it can be guided from the side of the conical drum section 212 into the drum 210. It is preferred that it rotates with the screw 230 or the drum 210 during operation.
[0047] At the cylindrical end of the drum 201, one or more liquid outlets 217 can be formed—preferably in or on the drum cover 213. These can be designed in various ways, such as openings in the drum cover 213 that have a type of overflow weir, or in other ways, such as peeling disc(s).
[0048] At least one solids discharge 218 can be formed in the drum 210, particularly in the region of the free end of the conical section 212. The solid Fe exits the drum 210 via openings arranged radially relative to the drum 210. The openings of the solids discharge 218 can alternatively also be arranged axially on the drum 210 with respect to the drum 210 (not shown).
[0049] The drum 210 is designed as a solid-shell drum. In the rotating drum 210, at least one incoming suspension Su is clarified from solids or separated into a liquid phase Fl and a solid phase Fe. The at least one liquid phase Fl exits the liquid outlet 217 at the drum cover 213. The solid phase Fe, on the other hand, is transported by the screw 230 toward the solids discharge 218 and ejected from the drum 210 there.
[0050] The drum 210 is rotatably mounted in the housing 100. The worm 230 can also be rotatably mounted relative to the drum. This allows the worm 230 to rotate at either a higher or lower speed than the drum 210, resulting in a differential speed between the drum 210 and the worm 230.
[0051] A drive device 300, which may have one or two motors (not shown here), is used to rotate the rotor 200. At least one gear unit (not shown here) may be connected downstream of the drive device 300. The drive device 300 rotates the drum 210 on the one hand and the worm 230 on the other, which is indicated here by a circular arrow. Alternatively, the rotor 200 can also be driven in another way.
[0052] In a preferred embodiment, the above features can also be incorporated into the solid-bowl screw centrifuge of Fig. 1, an enlarged detail of which is shown in Fig. 2, as well as other variants of the invention. However, in these variants, in particular, the removal of a portion of the liquid phase Fl or the centrate for analysis purposes is carried out in a different manner than in Fig. 3.
[0053] First, let us consider how this extraction is carried out according to the state of the art in Fig. 3.
[0054] The clarified liquid phase Fl – also called centrate in technical terms – is discharged according to Fig. 3 in such a way that the volume flow of the central system can freely exit the rotating system via one or more opening-like overflow weirs 219 of the liquid outlet 217 – here arranged or housed on a radius in the drum cover 213 – and then flow off, for example, into a shaft 110 with a pipe and / or tank connected downstream. Located in the shaft 110 is a sampling tap with a drainage channel (not shown here), which receives a partial flow of the centrate that accumulates in the shaft 110 outside the drum 210. The metrological analysis is then carried out using this pressure-free discharged portion of the centrate. This can lead to the disadvantages described above, such as, in particular, the tendency to bubble formation.
[0055] According to Fig. 1 and 2, the partial removal of the liquid phase Fl or the centrate for analysis purposes is therefore carried out in a different, more advantageous manner.
[0056] To divert a partial flow fl of the liquid phase Fl or the centrate, according to Figs. 1 and 2, a peeling element, in particular in the manner of a circumferentially closed hose (not shown) or in the manner of a drain pipe 220, is provided with its inlet opening in the region of the liquid outlet 217 upstream of an edge 221 of the overflow weir 219 with respect to the flow direction of the liquid phase Fl or the centrate, i.e., "before" the liquid phase Fl or the centrate flows out of the rotating system via the edge 221 of the overflow weir 219. It is therefore provided that the overflow weir, in addition to the openings in the drum cover through which the liquid phase can escape from the drum 210, has a radially inwardly open circumferential annular chamber in the manner of an annular cup 222.The liquid exiting the drum then flows first into the ring cup 222 rotating with the drum, before flowing out of the rotating system via an edge 221 of the ring cup 222.
[0057] A particularly advantageous feature is that the annular cup 222 forms a kind of gripper chamber into which the peeling element can easily be immersed to discharge a partial flow of the draining liquid under pressure—and thus without the disadvantages of the prior art. This is because the centrate is not "relaxed" when the partial flow is discharged, so that degassing of air and / or other gases that were trapped in the product or suspension to be clarified cannot generally occur.
[0058] The peeling element is preferably designed as a stationary, non-rotating element during operation. According to particularly preferred and easily implemented embodiments, the peeling element can preferably be designed as a drain pipe 220 or as a drain hose. However, it can also be designed in another way. The drain pipe 220 is bent at an angle here and can have an axial leg 224 aligned parallel and spaced from the rotation axis D, as well as a radial leg 225 aligned radially or perpendicularly to the rotation axis D, which extends into the annular cup 222 rotating during operation without touching it. This arrangement is preferred but not mandatory.
[0059] An inlet area of the radial leg 225 of the discharge pipe 220 can be aligned in such a way that the liquid phase Fl or the centrate, which passes from the drum into the annular bowl 222 and then rotates in the annular bowl 222 during operation of the solid bowl screw centrifuge, is “skimmed off” through a stationary pipe opening 223 of the radial leg 225 of the discharge pipe 220 before flowing out of the annular bowl 222 in the manner of a centripetal pump.
[0060] Fig. 2 shows that the edge 221 of the overflow weir 219 lies on a radius r with respect to the rotation axis D, and the stationary pipe opening 223 of the radial leg 225 of the discharge pipe 220 lies on a radius R. The radius R is greater than the radius r. However, preferably only a small portion fl is skimmed off, for example such that the skimmed portion fl of the liquid phase Fl corresponds to 1% to 5% of the liquid phase Fl.
[0061] Since the liquid phase or centrate partial quantity fl rotating at approximately drum speed is pressed through the pipe opening 223 into the discharge pipe 220 positioned downstream of the annular cup 222, as in a centripetal pump, the kinetic energy of the liquid phase FL or the centrate is converted into pressure.
[0062] According to a preferred variant, the maximum pressure in the outlet pipe 220 can be up to 10 bar. This pressure prevents foam and bubble formation in the partial quantity fl of the liquid phase Fl or the centrate discharged into the outlet pipe 220 or skimmed off therefrom. Discharging the partial flow under pressure prevents degassing of the centrate partial quantity fl discharged through the outlet pipe 220.
[0063] Due to the pressure generated in the pipe opening 223, the flow velocity in the drain pipe 220 can be adjusted by selecting the discharge cross-section in such a way that the settling of particles on the pipe wall or on the analysis equipment is prevented or such particles are removed or flushed away from the pipe wall or the analysis equipment.
[0064] By partially discharging the liquid phase Fl or the centrate under pressure, degassing of air or other gases from the liquid phase Fl or the centrate is significantly inhibited or completely prevented.
[0065] In the case of manual or, if necessary, automated evaluation of the liquid phase Fl by means of optical systems and a control unit, as well as a corresponding evaluation program, it is of great advantage if the liquid phase Fl or the centrate to be analyzed, which is separated from the main stream, is free of foam and bubbles, since in this way the measurement is not influenced or falsified by air or gas inclusions, such as foam or bubbles.
[0066] At least one sensor 226 can be arranged on / in the drain pipe 220 for analyzing the partial flow.
[0067] The sensor 226 is designed to detect one or more physical or chemical properties and / or the material properties of the partial flow and to convert them into a further processable electrical signal.
[0068] Suitable devices or sensors 226 for such analyses can be, for example, a turbidity sensor (transmitted or scattered light), a camera system, or other optical systems that are suitably positioned in the drain pipe. The measurement signal can be transmitted to a control unit 400 via a signal line, a data line, or wireless communication.
[0069] The sensor can be connected to the control unit 400—which can be embodied as a computer unit—via a wired or wireless connection (shown in dashed lines). The control unit 400 is preferably also designed to evaluate the sensor signals. For this purpose, an evaluation device in the form of a computer program can run on it, which is designed to perform the evaluation and influence operation based on this evaluation.
[0070] Thus, the operation of the solid-bowl screw centrifuge can optionally be influenced by the control unit 400, preferably based on the evaluation of the measured values recorded by sensor 226. For example, the differential speed can be changed by increasing or decreasing the screw speed. The bowl speed can also be increased or decreased.
[0071] The drain pipe 220 can be led back into the drain of the liquid phase, e.g. in the area of the shaft 110, in the flow direction behind the sensor 226, so that no product loss occurs, since the partial quantity is led back into the main stream or the shaft for the liquid phase after the analysis.
[0072] In a further particularly preferred embodiment of the invention, the skimming of the partial flow is carried out in such a way that the pressure in the discharge pipe is a maximum of 10 bar. The high pressure advantageously prevents gas fractions trapped in the liquid phase from outgassing in the form of bubbles or foam, thus impairing the analysis of the partial amount of the liquid phase.
[0073] 100 frames
[0074] 110 shaft
[0075] 200 rotor
[0076] 210 Drum
[0077] 211 cylindrical section
[0078] 212 conical section
[0079] 213 Drum cover
[0080] 214 Inlet pipe
[0081] 215 distributors
[0082] 216 Separation room
[0083] 217 Fluid drain
[0084] 218 Solids discharge
[0085] 219 Overflow weir
[0086] 220 drain pipe
[0087] 221 edge
[0088] 222 ring cup
[0089] 223 Pipe opening
[0090] 224 axial legs
[0091] 225 radial leg
[0092] 226 Sensor
[0093] 230 snail
[0094] 231 cylindrical section
[0095] 232 conical section
[0096] 233 snail egg
[0097] 234 Worm hub
[0098] 300 drive system
[0099] 400 Control
[0100] D axis of rotation
[0101] Su Suspension
[0102] Fe solids
[0103] Fl liquid phase fl subset of the liquid phase r radius
[0104] R Radius
Claims
Claims 1 . A solid bowl screw centrifuge for centrifugally processing a suspension Su in a centrifugal field, with which the suspension Su can be separated into at least one liquid phase Fl and one solid phase Fe, comprising a housing (100) and a rotor (200) rotatably mounted in the housing (100), which rotor 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) a screw (230) arranged in the drum (210) and rotatable at a differential speed relative to the rotatable drum (210), c) an inlet pipe (214) through which the suspension Su to be processed can be guided into a separation chamber (216) of the drum (210), d) at least one liquid outlet (217) through which the liquid phase Fl is discharged, wherein the liquid outlet (217) has at least one overflow weir (219), e) at least one solids discharge (218),through which the solid phase Fe is discharged; characterized in that f) for discharging a partial flow fl of the liquid phase Fl, a non-rotating peeling element which is stationary during operation is arranged in the region of the overflow weir (219) in such a way that this partial flow fl of the liquid phase Fl can be skimmed off under pressure from the liquid phase flowing through the overflow weir before it leaves the rotor which rotates during operation.
2. Solid bowl screw centrifuge according to claim 1, characterized in that the partial stream fl of the liquid phase Fl skimmed off by the skimming element has the same composition as the liquid phase Fl from which the partial stream fl is skimmed off.
3. Solid bowl screw centrifuge according to claim 1, characterized in that the peeling element is designed in the manner of a circumferentially closed discharge pipe (220).
4. Solid bowl screw centrifuge according to claim 1 or 2, characterized in that an inlet opening of the peeling member is arranged in relation to the Flow direction of the liquid phase Fl is positioned upstream of an edge (221) of the overflow weir (219).
5. Solid bowl screw centrifuge according to claim 3 or 4, characterized in that the area upstream of an edge (221) of the overflow weir (219) is designed as a radially inwardly open annular cup (222) into which the peeling element dips radially with its inlet opening.
6. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the discharge pipe (220) is bent at an angle and thus has an axial leg aligned parallel to the axis of rotation D (224) and a radial leg aligned perpendicular to the axis of rotation D (225) which dips into the ring cup (22).
7. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that an inlet region of the outlet pipe (220) is designed such that the liquid phase Fl rotating in the annular bowl (222) during operation of the solid bowl screw centrifuge is skimmed off through a stationary pipe opening (223) of the radial leg (225) of the outlet pipe (220) in the manner of a centripetal pump.
8. Solid bowl screw centrifuge according to one of claims 2 to 5, characterized in that the edge (221) of the overflow weir (219) lies on a radius r with respect to the axis of rotation D and the stationary pipe opening (223) of the radial leg (225) of the discharge pipe (220) lies on a radius R, wherein the radius R is greater than the radius r.
9. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the drum (210) has a cylindrical section (211) and a conical section (212).
10. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the liquid outlet (217), in particular the overflow weir through which the liquid phase Fl is discharged, is arranged in the cylindrical section (211) of the drum (210) or in a drum cover (213). 11 . Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the solids discharge (218) is arranged in the conical section (212) of the drum (210).
12. A method for centrifugally processing a suspension Su in a centrifugal field of a solid bowl screw centrifuge designed according to one of the preceding claims, comprising the following steps: A. feeding the solid bowl screw centrifuge with the suspension Su to be processed so that it is separated into at least one liquid phase Fl and one solid phase Fe, and B. Skimming off a partial flow fl of the liquid phase Fl through the skimming device in the region of the at least one overflow weir, so that the partial flow fl of the liquid phase Fl leaves the drum through the skimming device under pressure.
13. The method according to claim 12, characterized in that the partial stream fl of the liquid phase Fl skimmed off by the skimming device has the same composition as the liquid phase Fl from which the partial stream fl is skimmed off.
14. Process according to claim 12 or 13, characterized in that the skimming off of the partial stream fl is carried out in such a way that the skimmed off partial quantity fl of the liquid phase Fl corresponds to 1% to 5% of the liquid phase Fl.
15. Method according to claim 12, 13 or 14, characterized in that the skimming of the partial flow fl is carried out in such a way that the pressure in the skimming element, in particular in the outlet pipe (220) is max. 10 bar.
16. Method according to one of claims 12 to 15, characterized in that one or more measured values are recorded in the partial flow fl with a sensor (226) and that on the basis of the measured values recorded with the sensor (226) an evaluation of these measured values is carried out by means of a control device (400).
17. Method according to one of claims 12 to 16, characterized in that the functioning of the solid bowl screw centrifuge is influenced by the control unit (400) on the basis of the evaluation of the measured values recorded by the sensor (226).