Underflow-discharge device and hydrocyclone with such an underflow-discharge device
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-05-15
- Publication Date
- 2026-04-08
AI Technical Summary
Hydrocyclones in paper and cardboard manufacturing face inefficiencies in separating suspensions into depleted and heavy fractions, leading to unwanted contaminants being sorted out along with usable fiber material, which can cause clogging and reduce material preparation efficiency.
An underflow discharge device with a cup-shaped housing and coaxial addition pipe that supplies dilution fluid to the separation cone of the hydrocyclone, featuring a radial branch channel to divert a partial fluid flow and accelerate the heavy fraction flow, reducing blockages and improving separation efficiency.
Enhances the separation efficiency of hydrocyclones by directly diluting the reject suspension in the annular channel without straining the hydrocyclone, reducing the risk of blockages and improving the quality of the acceptance suspension stream by effectively flushing back foreign particles.
Smart Images
Figure EP2024063339_28112024_PF_FP_ABST
Abstract
Description
[0001]1 Underflow discharge device and hydrocyclone with such an underflow discharge device The invention relates to an underflow discharge device for a hydrocyclone and a hydrocyclone with such an underflow discharge device. WO 2020 / 157383 A1 describes a reject chamber of a centrifugal separator, wherein the reject chamber is designed such that it can be mounted under the cone of the centrifugal separator when the cone is pointing upwards, wherein the reject chamber has a dilution arrangement in its center, which has at least one dilution nozzle for discharging dilution fluid into the reject chamber and the reject chamber has a reject outlet at the bottom of the reject chamber, wherein the at least one dilution nozzle is directed outwards to achieve an outward flow of dilution fluid, which crosses an annular space surrounding the dilution arrangement in order to facilitate the circulating movement of theTo slow down the fluid flowing from the cone of the centrifugal separator downwards to the reject chamber. WO 2021 / 101742 A1 describes a cleaning system for removing solids and impurities from a feed slurry, the cleaning system comprising a separator operable to separate the feed slurry into an accepted slurry and a rejected slurry, the rejected slurry comprising at least a portion of the solids and impurities from the feed slurry. The cleaning system further comprises a dilution device located downstream of the separator and in fluid communication with a residue outlet of the separator, the dilution device comprising a dilution water hydrocyclone. EP 3018 252 B1 discloses a hydrocyclone for separating a fibre suspension into a heavy fraction, which essentially contains heavyContaining impurities, and into a light fiber fraction containing essentially fibers. The hydrocyclone comprises an elongated separation chamber with two opposite ends and an inlet element for feeding the fiber suspension substantially tangentially into the separation chamber at a first end thereof, such that the fiber suspension flows into the separation chamber in a vortex, and a first outlet element for discharging the accepted fraction from the separation chamber at said one end and a second outlet element for discharging the heavy fraction from the separation chamber at the second end thereof. The hydrocyclone comprises a distributor head for supplying a liquid to the separation chamber, the distributor head being arranged centrally in the separation chamber relatively close to the second end and having at least one outlet passage designed to spray a liquid jet. A liquid jet from the distributor head has aFlow component in the direction towards the second end of the separation chamber and crosses the flow into the reject chamber to cause a slowing of the flow in the reject chamber. Another liquid jet from the distributor head has a different flow component in the direction towards the first end. The object of the invention is to provide an underflow discharge device for a hydrocyclone, or to provide a hydrocyclone with such an underflow discharge device, whereby a separation of a suspension into a depleted suspension fraction and a separated heavy fraction is achieved with improved efficiency. The object is achieved by an underflow discharge device for a hydrocyclone, comprising: - a pot-shaped housing with a circumferential side wall and a bottom wall, wherein the side wall and the bottom wall delimit an annular channel with an annular opening, - a housing arranged on the annular openingsurrounding flange, which is designed for the fluid-tight connection of the underflow discharge device to an underflow opening of a hydrocyclone, and - an outlet nozzle arranged on the housing, which is designed to discharge a heavy fraction introduced from the hydrocyclone via the ring opening into the ring channel out of the ring channel to outside the underflow discharge device, and - a feed pipe arranged in the center of the pot-shaped housing coaxially to the ring channel, which comprises a connection nozzle, which is designed to supply a dilution fluid from outside the underflow discharge device into a main channel of the feed pipe for directing the supplied dilution fluid into a separation cone of the hydrocyclone in an axial direction along the symmetry axis of the separation cone opposite to the discharge direction of the heavy fraction from the separation cone into the ring channel of the underflow discharge device, when the25502 4 Underflow discharge device is connected to the hydrocyclone, wherein - the addition pipe has a branch channel branching off radially from the main channel, which is designed to divert a partial fluid flow from the total fluid flow of dilution fluid introduced into the main channel into the annular channel of the underflow discharge device. The underflow discharge device or a hydrocyclone with such an underflow discharge device can be used, for example, in the paper or cardboard manufacturing industry. The underflow discharge device or the hydrocyclone with such an underflow discharge device can be used in particular for the processing of waste paper. Waste paper generally has a particularly high proportion of impurities that must be sorted out before the accepted stock suspension is fed to a paper or cardboard machine. The hydrocyclone preferably works continuously, ie withoutBatchwise processing or intermittent processing. The reject suspension stream, or in short "the reject" or "reject material," can also be referred to as the heavy fraction or coarse fraction. It is the portion that is separated in the hydrocyclone via the underflow of the hydrocyclone. The accept suspension stream, which can form an accept, can also be referred to as the light fraction or fine fraction. It is the portion that is separated in the hydrocyclone via the overflow of the hydrocyclone. In principle, the feed fiber suspension depleted in a hydrocyclone by a reject suspension stream can form an accept. The accept is therefore the fraction that is to be used as a product or intermediate product and is also referred to as the accept suspension stream. The reject suspension stream can be subjected to a further process or process step.In paper production, the reject suspension stream can contain, for example, debris such as film scraps, glass splinters, plastic, or polystyrene particles, which must be sorted in the hydrocyclone according to their particle size and particle shape. However, due to the sole selection according to particle size and particle shape in the hydrocyclone, specks, i.e., fiber bundles or fiber knots of several individual fibers, are also separated as rejects along with the unwanted particles, even though the specks would actually represent part of the accept material. The accept suspension stream, which forms the accept material in the remaining depleted suspension fraction, can contain the desired fiber particles, which can be used for the aforementioned paper production. The hydrocyclone can be a final processing step before the accept suspension stream is fed to a paper or board machine. Rejects from continuously operated hydrocyclones contain, in addition to the actualHowever, despite the presence of impurities, there is often still usable fiber material that could and should actually be classified as an accept. The mass fraction of such rejected accept or good material can range from 30% to 70% of the total reject. This is very disadvantageous and means a lower efficiency of the stock preparation than would be possible. Such reject still containing good material could indeed be returned directly and untreated to the upstream separation stage before the hydrocyclone. However, this would mean an additional burden. In addition, this also results in an undesirable re-enrichment of the feed material with impurities, which can even lead to a complete collapse, i.e., a blockage of the hydrocyclone. To prevent blockage of the hydrocyclone due to thickening in the underflow discharge device, a so-calledDilution water can be added via an addition pipe. However, such an addition pipe arranged in the underflow discharge device structurally reduces, and the water jet emerging from the addition pipe also fluidically reduces, the outlet area in the lower region of the hydrocyclone's separation cone, so that less reject is flushed into the underflow discharge device. The escaping water jet can, for example, be at least 0.5 bar higher than the flow pressure. Depending on the amount of dilution water added, different operating conditions arise. Depending on the amount of dilution water, for example, different flow velocities arise at the dilution water pipe. In an exemplary hydrocyclone size, the volume can be, for example, 7.5 liters. With an inlet volume of 450 liters / min, the hydrocyclone fills once per second. In the outlet area for the reject suspension flow,For example, 10% of the inlet volume 25502 7 is withdrawn, i.e., 45 liters / min. This corresponds to 0.75 liters per second. The reject material is influenced by the addition of different amounts of dilution water as follows. When a small amount of dilution water is added via the addition pipe (for example, 20 liters / min), no foreign matter is flushed back into the flow-through vortex. The entire amount of added dilution water can therefore serve to dilute the reject suspension flow. Separation is most effective with this operating mode. However, the hydrocyclone remains more susceptible to blockages, since the dilution water quantity introduced centrally axially into the cone via the addition pipe must also pass through the outlet plane of the cone, i.e., the narrowest passage point of the cone, in order to reach the underflow discharge device. The consistency of the reject suspension stream is high and can, depending onInlet consistency, for example, approximately 3.0% to 4.0% of the suspension flow. When a medium amount of dilution water is fed through the addition pipe (for example, 40 liters / min), a flow is created from the outlet of the cone to the continuous vortex. Approximately two-thirds of the dilution water quantity is used to dilute the reject, and approximately one-third of the dilution water quantity enters the continuous vortex, from where it can enter the accept suspension flow. Depending on the flow velocity at the addition pipe, particles already present on the inner cone wall can be flushed back into the continuous vortex. This reduces the efficiency of the hydrocyclone. The consistency of the reject suspension flow is then, depending on the inlet consistency, for example, 1.5% to 2.0% of the suspension flow. When a large amount of dilution water is added via the addition pipe (e.g. 60 litres / min), approx.60% of the dilution water volume is used to dilute the reject, and approximately 40% of the dilution water volume enters the continuous vortex. When such a high volume of dilution water is added, the flow velocity is so high that foreign particles are flushed into the continuous vortex. Due to the high flow velocity, even heavy particles with a small volume are kept in suspension and only flushed into the underflow discharge device when a larger accumulation occurs. The stock consistency of the reject is, for example, 1.0% to 1.5% of the suspension stream, depending on the inlet stock consistency. The quality of the accept suspension stream is therefore also determined in the lower section of the hydrocyclone. This depends on how many foreign particles that have already been pressed against the cleaner wall are flushed back into the continuous vortex by currents. The underflow discharge device has a pot-shaped housing with a circumferential side wall and abottom wall. The side wall and the bottom wall define an annular channel, which is accessible via an annular opening. The pot-shaped housing is intended for attachment to an underflow of a hydrocyclone. The reject emerging downwards from the underflow of the hydrocyclone can enter the annular channel of the underflow discharge device via the annular opening. 25502 9 In order to be able to attach the underflow discharge device to the underflow of the hydrocyclone, the housing has a flange surrounding the annular opening. The flange is designed for the fluid-tight connection of the underflow discharge device to the underflow opening of the hydrocyclone. The flange can, for example, have several bores, in particular several bores that lie on a common pitch circle, so that the flange can be screwed to an underflow nozzle of the hydrocyclone using several screws. Alternatively, the pot-shaped housing of the underflowThe underflow discharge device can also, for example, have an external or internal thread running around the housing, which can interact with an internal or external counter-thread on the underflow nozzle of the hydrocyclone. In such a case, the housing can simply be screwed onto the underflow nozzle. An outlet nozzle is formed on the housing, which serves to discharge a heavy fraction introduced from the hydrocyclone via the ring opening into the ring channel, out of the ring channel to the outside of the underflow discharge device. The outlet nozzle can be formed integrally with the housing, for example as a cast part. Alternatively to a one-piece design, the outlet nozzle can, if necessary, be manufactured as a separate component and mounted on the housing. The underflow discharge device has an addition pipe arranged in the center of the pot-shaped housing coaxially to the ring channel, which pipe comprises a connection nozzle thatis designed to supply a dilution fluid from outside the underflow discharge device into a main channel of the addition pipe for guiding the supplied dilution fluid 25502 10 into a separation cone of the hydrocyclone in an axial direction along the axis of symmetry of the separation cone opposite to the direction of flow of the heavy fraction from the separation cone into the annular channel of the underflow discharge device when the underflow discharge device is connected to the hydrocyclone. In order to create an underflow discharge device for a hydrocyclone, or to create a hydrocyclone with such an underflow discharge device, whereby a separation of a suspension into a depleted suspension fraction and a separated heavy fraction can be achieved with an improved efficiency, it is proposed according to the invention that the feed pipe has a branch channel branching off radially from the main channel, which is designedis for diverting a partial fluid flow from the total fluid flow of dilution fluid introduced into the main channel into the annular channel of the underflow discharge device. Via such a branch channel branching radially from the main channel of the addition pipe, a partial fluid flow of the dilution fluid intended for the separation cone of the hydrocyclone can be branched off, even before this portion of the dilution fluid reaches above the outlet surface in the lower region of the separation cone of the hydrocyclone, i.e., into the separation cone. This ensures that the partial fluid flow of dilution fluid intended to dilute the reject suspension flow does not have to flow back from the main channel of the addition pipe via the outlet surface in the lower region of the separation cone of the hydrocyclone, against the main flow direction of the dilution fluid. This avoids unnecessary mass loading or pressure load in this area,which is the 25502 11 separation limit for separation in the hydrocyclone. By branching the partial fluid flow of dilution fluid beforehand via the branch channel directly into the annular channel of the underflow discharge device, the reject suspension flow can be diluted directly in the annular channel by the dilution fluid without this dilution fluid loading the hydrocyclone. Consequently, the selectivity of the hydrocyclone is not negatively affected or significantly negatively affected despite the dilution of the reject suspension flow with dilution fluid. The branch channel can be designed to introduce the partial fluid flow in a mass flow, which generates a suction in the heavy fraction flow in the annular channel, which accelerates the mixture of heavy fraction flow and partial fluid flow into the outlet nozzle. In this way, unwanted blockage in the area of the outlet surface in the lower area of the separation cone of the hydrocyclone can be avoided.be reduced. The partial fluid flow which is branched off from the main channel of the addition pipe via the radial branch channel is designed in such a way that the annular flow of the heavy fraction flow, i.e. the reject suspension flow in the annular channel is not slowed down by the partial fluid flow, but rather is accelerated into the outlet nozzle of the underflow discharge device. The branch channel in the addition pipe can be led out in such a radial orientation that the outlet opening of the branch channel opening into the annular channel is positioned at an angle of between 35 degrees and 50 degrees to the radial outflow direction of the mixture of heavy fraction flow and partial fluid flow from the outlet nozzle out to 25502 12 outside the underflow discharge device on the addition pipe. If the outlet opening of the branch channel leading into the annular channel is in an angle range between 35 degrees and 50 degreesIf the branch channel in the feed pipe is positioned at an angle offset to the radial outflow direction of the mixture of heavy fraction flow and partial fluid flow from the outlet nozzle, the partial fluid flow can still be introduced into the heavy fraction flow within a region of the annular channel that lies outside the outflow area at the inlet of the outlet nozzle or near the inlet of the outlet nozzle. Thus, the introduced partial fluid flow is not introduced directly into the outlet nozzle, but rather offset in a closed-walled region of the annular channel away from the outlet nozzle. The branch channel in the feed pipe can, in particular, be led out of the feed pipe perpendicular to the main flow direction in the main channel of the feed pipe. If the outlet nozzle of the underflow discharge device is attached or designed on the housing in such a way that the central axis of the outlet nozzle is oriented perpendicular to the main flow direction in the main channel of the feed pipe,then the branch channel can be arranged running in a plane perpendicular to the main flow direction in the main channel of the addition pipe. The branch channel can be arranged upstream of the flow channel of the outlet nozzle in a clockwise circumferential direction when viewed from above onto the annular channel. Alternatively, the branch channel can be arranged downstream of the flow channel of the outlet nozzle in a clockwise circumferential direction when viewed from above onto the annular channel. 25502 13 The branch channel formed in the addition pipe can open into the annular channel with its outlet opening at an axial height close to the bottom. By introducing the partial fluid flow coming from the branch channel into the annular channel close to the bottom, it is achieved that the partial fluid flow is introduced into the annular channel as far away as possible from the outlet surface in the lower region of the separation cone of the hydrocyclone. The partial fluid flow introduced into the ring channel via the branch channel influencesDilution fluid enters the separation area at the level of the outlet surface of the hydrocyclone's separation cone as little as possible. The lower third of the height of the annular channel is considered to be near the bottom. Similarly, the inlet of the outlet nozzle can also be connected to the annular channel at an axial height close to the bottom. Accordingly, the branch channel formed in the feed pipe can open into the annular channel with its outlet opening at an axial height at which the flow channel of the outlet nozzle is also located. The branch channel can have a flow cross-section designed to divert a partial mass flow of the partial fluid flow into the annular channel of the underflow discharge device. The flow cross-section is between 20% and 40% of the flow cross-section of the main channel. The feed pipe can have only a single branch channel. The subsequent dilution is thus carried out in a targeted manner. In particular, the branch channel flows upstream toIncreased dilution fluid is fed to the outlet nozzle, and fiber-laden suspension can be fed to the separation cone. 25502 14 The branch channel can be provided with an inflow recess. This can promote inflow into the branch channel. If flow is primarily expected from the main channel into the branch channel, an inflow recess should be formed on the side of the main channel. If flows in both directions through the branch channel are expected, the provision of an inflow recess on both sides of the branch channel is advantageous. Particularly good inflow behavior into the branch channel is achieved by an elongated oval, preferably eye-shaped, inflow recess. The elongated oval is aligned in the flow direction, so that the longer diameter is arranged in the axial direction. This task is also solved by a hydrocyclone for the centrifugal separation of solids.from a suspension with a separation chamber, an inlet opening into the separation chamber for feeding a suspension into the separation chamber, an overflow for discharging a depleted suspension fraction, and an underflow with an underflow opening for discharging a separated heavy fraction, comprising an underflow discharge device connected to the underflow opening according to one of the described embodiments. The underflow discharge device can accordingly be a subcomponent or a subassembly of a centrifugal separator, in particular a hydrocyclone. However, the underflow discharge device can also form a separate device, which can be retrofitted, for example, as an upgrade kit to existing centrifugal separators, in particular hydrocyclones. 25502 15 For operating a hydrocyclone for centrifugal separation, the inflow of the dilution fluid must be controlled. This allows an inflow from the annular space intothe main channel as well as a flow of dilution fluid via the branch channel into the annular space for optimizing the fiber yield. A concrete embodiment of the invention is explained in more detail in the following description with reference to the attached figures. Concrete features of this exemplary embodiment can represent general features of the invention, regardless of the specific context in which they are mentioned, if appropriate also considered individually or in further combinations. They show: Fig. 1 a perspective view of an exemplary hydrocyclone, Fig. 2 a longitudinal section through a hydrocyclone with an exemplary underflow discharge device, Fig. 3 a sectional view of the exemplary underflow discharge device according to Fig. 2, Fig. 4 a cross-sectional view of the exemplary underflow discharge device along the section line AA according toFig. 3 with a branch channel upstream of the outlet nozzle, and 25502 16 Fig. 5 is a representation of the exemplary underflow discharge device in cross section along the section line AA according to Fig. 3 with a branch channel downstream of the outlet nozzle, Fig. 6 is a longitudinal section through a hydrocyclone with an exemplary underflow discharge device with an inflow recess, Fig. 7 is a top view of the inflow recess along CC Fig. 8 is a section according to Fig. 6 with flow out of the branch channel; Fig. 9 is a section according to Fig. 6 with flow into the branch channel; Fig. 1 shows an exemplary hydrocyclone 1 for the centrifugal separation of solids from a suspension. The hydrocyclone 1 comprises a separation chamber 2 and an inlet 3 leading into the separation chamber 2 for feeding a suspension into the separation chamber 2, an upper flow 4 for discharging a depleted suspension fraction, also referred to as accept, and an underflow5 with an underflow opening 6 for discharging a separated heavy fraction. 25502 17 In Fig. 2, the hydrocyclone 1 is only partially shown, namely only with its lower section in the area of the underflow 5 with the underflow opening 6, which is located below a separation cone 2a of the hydrocyclone 1. The separation cone 2a encloses the separation chamber 2. In the area of the lower section of the separation cone 2a there is an underflow discharge device 7 connected to the underflow opening 6. The underflow discharge device 7 shown in the following Figures 2 to 9 has a pot-shaped housing 8 with a circumferential side wall 9 and a bottom wall 10. The side wall 9 and the bottom wall 10 define an annular channel 11 with an annular opening 12. The underflow discharge device 7 also has a flange 13 arranged on the housing 8, surrounding the annular opening 12, which is designed for fluid-tightConnecting the underflow discharge device 7 to the underflow opening 6 of the hydrocyclone 1. For a fluid-tight connection of the underflow discharge device 7 to the underflow opening 6 of the hydrocyclone 1, an annular groove can be introduced in the region of the flange 13 or on its upper side, into which a sealing ring (not shown in detail) can be inserted. The underflow discharge device 7 also has an outlet nozzle 14 arranged on the housing 8, which is designed to discharge a heavy fraction introduced from the hydrocyclone 1 via the annular opening 12 into the annular channel 11 out of the annular channel 11 to the outside of the underflow discharge device 7. 25502 18 The outlet nozzle 14 can, for example, as shown in Fig. 2, be designed as a cast part in one piece with the housing 8. As an alternative to a one-piece design, the outlet nozzle 14 can, if necessary, be manufactured as a separate component and attached to the housing 8be mounted. A feed pipe 15 arranged in the center of the pot-shaped housing 8 coaxial with the annular channel 11 comprises a connecting piece 16 which is designed to supply a dilution fluid from outside the underflow discharge device 7 into a main channel H of the feed pipe 15 for guiding the supplied dilution fluid into the separation cone 2a of the hydrocyclone 1 in an axial direction R1 along the axis of symmetry A of the separation cone 2a opposite to the discharge direction R2 of the heavy fraction from the separation cone 2a into the annular channel 11 of the underflow discharge device 7 when the underflow discharge device 7 is connected to the hydrocyclone 1, as can be seen in Fig. 2. The addition pipe 15 has a branch channel 17 branching off radially from the main channel H, which is designed to divert a partial fluid flow from the total fluid flow introduced into the main channel H via the connecting piece 16 toDilution fluid into the annular channel 11 of the underflow discharge device 7. The underflow discharge device 7 with the main channel H and the branch channel 17 is shown again in Fig. 3 in a standalone position. The branch channel 17 is designed to introduce the partial fluid flow in a mass flow, which creates a suction in the heavy fraction flow in the annular channel 11, which accelerates the mixture 25502 19 of heavy fraction flow and partial fluid flow into the outlet nozzle 14. In this way, undesirable blockage in the area of the outlet surface AF in the lower area of the separation cone 2a of the hydrocyclone 1 can be avoided or reduced. The partial fluid flow, which is branched off from the main channel H of the feed pipe 15 via the radial branch channel 17, is designed in such a way that the annular flow of the heavy fraction flow, ie the reject suspension flow in the annular channel 11, is not slowed down by the partial fluid flow, but ratheris accelerated into the outlet nozzle 14 of the underflow discharge device 7. In the case of the present exemplary embodiment, the branch channel 17 is led out in the addition pipe 15 in such a radial orientation that the outlet opening 18 of the branch channel 17 opening into the annular channel 11 is positioned on the addition pipe 15 at an angle of between 35 degrees and 50 degrees to the radial outflow direction AR of the mixture of heavy fraction flow and partial fluid flow from the outlet nozzle 14 to the outside of the underflow discharge device 7. This is specifically illustrated in two different variants in the cross-section through the annular channel 11 of the underflow discharge device 7 in Fig. 4 and Fig. 5. If the outlet opening 18 of the branch channel 17 opening into the annular channel 11 is offset in an angular range between 35 degrees and 50 degrees to the radial outflow direction AR of the mixture of heavy fraction flow and partial fluid flowis positioned out of the outlet nozzle 14, the partial fluid flow can still be introduced into the heavy fraction flow within a region of the annular channel 11 which lies outside 25502 20 of the outflow region B at the inlet of the outlet nozzle 14 or in the vicinity of the inlet of the outlet nozzle 14. In this way, the introduced partial fluid flow is not introduced directly into the outlet nozzle 14, but rather offset in a closed-walled region of the annular channel 11 away from the outlet nozzle 14, as shown in Fig. 4 and Fig. 5. In the embodiment according to Fig. 4, the branch channel 17 is arranged upstream of the flow channel of the outlet nozzle 14 in the clockwise circumferential direction U in the plan view of the annular channel 11 from above. In the embodiment according to Fig. 5, the branch channel 17 is arranged clockwise in the circumferential direction U downstream of the flow channel of the outlet nozzle 14 in the plan view of the annular channel 11 from above. The branch channel17 can, as is particularly shown in Fig. 2 and Fig. 3, be led out of the addition pipe 15 in particular perpendicular to the main flow direction in the main channel H of the addition pipe 15. If the outlet nozzle 14 of the underflow discharge device 7 is attached to the housing 8 as shown or is designed such that the central axis Z of the outlet nozzle 14 is oriented perpendicular to the main flow direction in the main channel H of the addition pipe 15, then the branch channel 17 can be arranged running in a plane perpendicular to the main flow direction in the main channel H of the addition pipe 15. The branch channel 17 formed in the addition pipe 15 can, as shown, open into the annular channel 11 with its outlet opening 18 at an axial height close to the bottom. 25502 21 The branch channel 17 formed in the addition pipe 15 is, in the case of the present embodiment, with its outlet opening 18 opening into the annular channel 11 at an axial heightformed, in which the flow channel of the outlet nozzle 14 is also located. The branch channel 17 can have a flow cross-section which is designed to branch off a partial mass flow of the partial fluid flow into the annular channel 11 of the underflow discharge device 7, which partial mass flow is between 20% and 40% of the total mass flow of the total fluid flow of dilution fluid introduced into the main channel H. The addition pipe 15 can, as shown in the respective embodiment variant, have only a single branch channel 17. The representation in Fig. 6 corresponds to the partial representation of the hydrocyclone 1 according to Figure 2, wherein the branch channel 17 is provided with an inflow recess 19 on the side of the main channel H. The inflow recess 19 is preferably eye-shaped, as shown in the plan view in Fig. 7. The inflow recess 19 promotes the flow into the branch channel 17. Figures 8 and 9 show variousFlow variants and thus different operating options are shown. In the design according to Figure 8, the branch channel 17 is designed at an angle in the direction of the main axis of symmetry A. The deviation from the horizontal can be in the range of 20° to 50°. 25502 22 Dilution fluid enters the separation cone 2a through the main channel H. With large volumes of dilution fluid, foreign material already separated radially outward in the separation cone 2a can be flushed back radially inward into the separation cone 2a. The backflushed material then reaches the area of the axis of symmetry A and is fed in axial direction R1 as accept to the overflow 4. The backflushed foreign particles cause a deterioration in the quality of the accept. Due to the additional supply of dilution fluid through the branch channel 17, dilution water is fed in front of the reject outlet in front of the outlet nozzle 14. This results in an additional,Targeted dilution of the escaping rejects. This also results in less dilution fluid being flushed through the main channel H into the separation cone 2a. Consequently, the risk of backwashing of foreign particles, especially heavy particles, is reduced. Separation efficiency is improved. The radially introduced dilution fluid causes additional backwashing of fibers and usable fines into the underflow opening. Only fibers and fines are backwashed, since the heavy particles flow along the outer wall of the annular channel 11 of the underflow discharge device 7. Due to the mass inertia of the foreign particles separated radially outward, outflow through the outlet nozzle 14 is promoted. The fibers and usable fines flushed back into the underflow opening are flushed back into the lower separation cone 2a by the jet effect of the dilution fluid entering in the direction R1 from the main channel H. 25502 23 TheBackflushed fibers and fines are fed to the Accept with the escaping axial dilution water and discharged through the overflow. Figure 9 shows a different operating situation under different operating conditions. Suspension from the radially inner region of the annular channel 11 of the underflow discharge device 7 is drawn through the branch channel 17 into the main channel H and then flushed with the dilution fluid into the lower separation cone 2a. The design of the branch channel 17 with the edges ensures that no heavy foreign particles can enter the branch channel 17. Due to the kinetic energy contained in the flowing heavy particles, deflection into the bore of the branch channel 17 is not possible over such short distances in such a small flow cross-section of the branch channel 17. By feeding suspension from the annular space 11 into the main channel, a portion of usable fibers and fines from the rejectare removed, thus improving the separation efficiency of the hydrocyclone. The formation of an inflow recess 19 in the axial main channel H results in better inflow into the main stream in the main channel H. A steady flow is formed, and fibers are thus fed to the lower separation cone 2a. 25502 24 List of reference symbols 1 Hydrocyclone 2 Separation chamber 2a Separation cone 3 Inlet 4 Upper flow 5 Underflow 6 Underflow opening 7 Underflow discharge device 8 Pot-shaped housing 9 Side wall 10 Bottom wall 11 Ring channel 12 Ring opening 13 Flange 14 Outlet nozzle 15 Addition pipe 16 Connection nozzle 17 Branch channel 18 Outlet opening 19 Inflow recess A Symmetry axis AF Outlet surface H Main channel R1 Axial direction R2 Discharge direction of heavy part fraction U Circumferential direction
Claims
1. Underflow discharge device for a hydrocyclone (1), comprising: - a pot-shaped housing (8) with a circumferential side wall (9) and a bottom wall (10), wherein the side wall (9) and the bottom wall (10) delimit an annular channel (11) with an annular opening (12), - a flange (13) arranged on the housing (8) and surrounding the annular opening (12), which flange is designed for fluid-tight connection of the underflow discharge device (7) to an underflow opening (6) of a hydrocyclone (1), and - an outlet nozzle (14) arranged on the housing (8), which is designed for discharging a heavy fraction introduced from the hydrocyclone (1) via the annular opening (12) into the annular channel (11) out of the annular channel (11) to outside the underflow discharge device (7), and - a flange (13) arranged in the center of the pot-shaped housing (8) addition pipe (15) arranged coaxially to the annular channel (11), which comprises a connecting piece (16),which is designed to supply a dilution fluid from outside the underflow discharge device (7) into a main channel (H) of the addition pipe (15) for guiding the supplied dilution fluid into a separation cone (2a) of the hydrocyclone (1) in an axial, 26 Direction (R1) along the axis of symmetry (A) of the separation cone (2a) opposite to the discharge direction (R2) of the heavy fraction from the separation cone (2a) into the annular channel (11) of the underflow discharge device (7), when the underflow discharge device (7) is connected to the hydrocyclone (1), wherein - the addition pipe (15) has a branch channel (17) branching off radially from the main channel (H), wherein the branch channel (17) is designed to divert a partial fluid flow into or out of the total fluid flow of dilution fluid of the underflow discharge device (7) introduced into the main channel (H).
2. Underflow discharge device according to claim 1, characterized in that the branch channel (17) is designed to introduce the partial fluid flow into a mass flow, which creates a suction in the heavy fraction flow in the annular channel (11), which accelerates the mixture of heavy fraction flow and partial fluid flow into the outlet nozzle (14). 3.Underflow discharge device according to claim 1 or 2, characterized in that the branch channel (17) in the addition pipe (15) is led out in such a radial orientation that the outlet opening (18) of the branch channel (17) opening into the annular channel (11) is positioned on the addition pipe (15) in an angular range between 35 degrees and 50 degrees angularly offset to the radial outflow direction (AR) of the mixture of heavy fraction flow and partial fluid flow from the outlet nozzle (14) out to the outside of the underflow discharge device (7). 25502 27 4. Underflow discharge device according to one of claims 1 to 3, characterized in that the branch channel (17) is arranged upstream of the flow channel of the outlet nozzle (14) in a clockwise circumferential direction (U) in a plan view of the annular channel (11) from above.
5. Underflow discharge device according to one of claims 1 to 3, characterized in that the branch channel (17) is arranged downstream of the flow channel of the outlet nozzle (14) in a clockwise circumferential direction (U) in a plan view of the annular channel (11) from above.
6. Underflow discharge device according to one of claims 1 to 5, characterized in that the branch channel (17) formed in the feed pipe (15) opens into the annular channel (11) with its outlet opening (18) at an axial height close to the bottom.Underflow discharge device according to one of claims 1 to 6, characterized in that the branch channel (17) formed in the addition pipe (15) opens with its outlet opening (18) into the annular channel (11) at an axial height at which the flow channel of the outlet nozzle (14) is also located.
8. Underflow discharge device according to one of claims 1 to 7, characterized in that the branch channel (17) has a flow cross-section which is designed to branch off a partial mass flow of the partial fluid flow into the annular channel (11) of the underflow discharge device (7), wherein the flow cross-section of the. 25502 28 branch channel (17) is between 20% and 40% of the flow cross-section of the main channel (H).
9. Underflow discharge device according to one of claims 1 to 8, characterized in that the addition pipe (15) has only a single branch channel (17).
10. Underflow discharge device according to one of claims 1 to 9, characterized in that the branch channel (17) is formed perpendicular to the main channel (H).
11. Underflow discharge device according to one of claims 1 to 10, characterized in that the branch channel (17) opens into an inflow recess (19) at least at one end.
12. Underflow discharge device according to one of claims 1 to 11, characterized in that the inflow recess (19) is formed in the main channel (H).Underflow discharge device according to one of claims 1 to 11, characterized in that the inflow recess (19) is elongated, preferably oval, in particular eye-shaped, in the flow direction of the main channel (H).
14. Hydrocyclone for the centrifugal separation of solids from a suspension with a separation chamber (2), an inlet (3) opening into the separation chamber (2) for feeding a suspension into the separation chamber (2), an overflow (4) for discharging a depleted suspension fraction and an underflow (5) with an underflow. 25502 29 Opening (6) for discharging a separated heavy fraction, comprising an underflow discharge device (7) according to one of claims 1 to 13 connected to the underflow opening (6).
15. Method for centrifugally separating solids from a suspension with a hydrocyclone according to claim 14, wherein the flow of the dilution fluid is controlled for an inflow of suspension from the annular space into the main channel or inflow of dilution fluid into the annular space.