EP1474241A1

EP1474241A1 - Full-jacket helix centrifuge with a weir

Info

Publication number: EP1474241A1
Application number: EP03704471A
Authority: EP
Inventors: Paul BRÜNING; Jürgen HERMELER; Helmut Figgener
Original assignee: Westfalia Separator GmbH
Current assignee: GEA Mechanical Equipment GmbH
Priority date: 2002-01-30
Filing date: 2003-01-27
Publication date: 2004-11-10
Also published as: CA2473640C; KR20040098635A; WO2003064054A1; CA2473640A1; US20050164861A1; CN1691985A; DE10203652A1; DE10203652B4; US7326169B2; CN100337754C; KR100857950B1

Abstract

Disclosed is a full-jacket helix centrifuge comprising at least one weir (15) diverting a clarified fluid from a drum (3). Said drum (3) is provided with a port (17) to which a throttling device, particularly a throttle disk (31), is assigned. Said throttling device is arranged at a variable distance from the port (17) and is configured as a static part in relation to the drum (3) when the centrifuge is in an operating position. A nozzle (21) which rotates together with the drum (3) and discharges the clarified fluid is associated with the port.

Description

Full shell screw centrifuge with a weir

The invention relates to a solid bowl screw centrifuge according to the preamble of claim 1.

Such a centrifuge is known from DE 43 20 265 AI. The one in this

Scripture-disclosed solid bowl screw centrifuge is provided on the liquid outlet side with a weir which has a passage which can be formed by a plurality of grooves extending from the inside diameter of the weir or by openings provided in the walls of the weir. Associated with the passage is a throttle disc which is stationary relative to this while the drum is rotating and which is axially displaceable via a threaded bushing.

The distance between the weir and the throttle plate can be changed by turning the threaded bushing. This changes the discharge cross-section for the liquid running out of the centrifugal drum, which is composed of the total length of the transition edge of the passage and the distance between the weir and the throttle disc.

The change in the discharge cross-section causes a change in the liquid level in the centrifugal drum, so that this can be adjusted continuously

Liquid level is possible by moving the throttle plate.

The throttle plate can also be displaced in the axial direction in that the throttle plate is articulated and pivoted on its outer circumference, which in the area of the weir leads to an axial displacement between the throttle plate and the weir.

The publication "Patent Abstracts of Japan", number 11179236 A, shows that a baffle can be assigned to a passage, which one from the drum give a fluid swirl, the recoil effect should be used to save energy.

The construction of DE 43 20 265 AI has proven itself since it offers a solution to the problem with the construction of DE 41 32 029 AI that the devices for adjusting the transfer diameter on the weir rotate with the drum during operation , which makes a relatively complex and laborious transfer of actuating forces to the rotating centrifugal drum necessary.

Nevertheless, it is desirable to be able to use simple means to provide additional adjustment options for the weir of the solid-bowl screw trifuge for different feed rates. The object of the invention is to solve this problem.

The invention solves this problem by the subject matter of claim 1.

Thereafter, the passage is also assigned at least one nozzle or several nozzles rotating with the drum for discharging / discharging the clarified liquid.

In this way, the invention offers the possibility of deriving a fixed basic quantity from the drum through the nozzles and additionally using the variable throttle device, in particular the throttling disk, to finely regulate or fine-tune the liquid level in the solid bowl screw centrifuge ,

Although nozzles on solid-bowl screw centrifuges and their effect of saving energy with an appropriate orientation inclined to the drum axis are known per se, for example from DE 39 004 151 A1. However, the advantageous effect, which results from the fact that they are combined with a throttle device at the liquid discharge. The throttle device is used to regulate the liquid level in the centrifuge. With increasing flow resistance at the gap through which the liquid exits the throttle device, a greater liquid pressure at the passage is required, which leads to an increase in the

Liquid level in the centrifuge. Since this change in pressure also changes the amount of liquid flowing out through the nozzles, these two effects add up, i.e. the control range that can be achieved becomes larger and the control characteristic is advantageously influenced. This effect does not occur according to the prior art, since there is no throttle device with upstream nozzles but only nozzles with a downstream overflow opening. According to the state of the art, the nozzle is hoped for the effect of saving energy and improving the conditions at the solids discharge.

The nozzles are particularly advantageously designed to be exchangeable in order to be able to easily preset the amount of liquid that runs off, e.g. with strongly varying throughput quantities. Another advantage of this measure can be seen in the fact that changing the nozzles against others with a different diameter provides a simple further possibility for changing the control and setting characteristics. "Nozzles" with blind bores (closed bores) can also be set, as a result of which the number of nozzles and the characteristics can also be changed.

The nozzles are preferably connected downstream of the passage and the throttle device is in turn connected downstream of the nozzles.

The nozzle chamber preferably also has a diameter which corresponds to the diameter at the outer edge of the passage. This ensures very favorable flow conditions in the nozzle chamber, which largely or completely prevent the accumulation of dirt. In this variant in particular, clearing elements are no longer required in the nozzle chamber.

In order to avoid blockages, it is advantageous if the nozzles have a diameter of more than 2 mm. It is in particular possible to provide the nozzles with such a large diameter if they are arranged offset radially inwards relative to the outer drum shell, and particularly preferably such that the nozzles are at a distance from the outer drum radius in a plane perpendicular to the drum axis Have 25 to 75% of the drum radius.

The further inward the nozzles are arranged, the larger their diameter can be selected in order to achieve a constant discharge rate. By arranging further inwards, the nozzles can basically only be designed so that blockages are reliably avoided. This was not recognized in the prior art. For this reason, too, the nozzles have not become particularly popular in practice.

Another advantage of the measure of arranging the nozzles further inward toward the axis of rotation is that it is possible to change the annular chamber provided according to DE 43 20 265 AI - called an annular channel there - in such a way that the annular chamber there

Ring channel arranged and provided broaching tools that are necessary to avoid the accumulation of dirt can be saved.

In addition to the good adjustability and adaptability of the amount of the expiring

Liquid from the solid bowl screw centrifuge should be mentioned as a further advantage that, with appropriate alignment of the openings of the nozzles inclined to the axis of symmetry, the liquid emerging from the nozzles reduces the drive power and energy to be applied of the solid bowl screw centrifuge. This Energy saving is not insignificant and can lead to a noticeable reduction in the energy consumption of the solid bowl screw centrifuge.

The openings of the nozzles are preferably oriented backwards in relation to the direction of rotation of the drum in order to save energy.

The openings of the nozzles are preferably oriented in relation to a tangent in a plane perpendicular to the drum axis of rotation on the drum surface such that they have an inclination between 0 ° and 30 °. An inclination of 0 ° brings maximum energy gain. Values greater than 0 ° and less than 30 ° can be implemented constructively.

If a variant with radial alignment of the nozzle openings is realized, the advantage of energy saving when driving the drum is eliminated. However, the easy adaptability to different throughput quantities is retained, so that such a variant also offers a considerable advantage over the prior art.

The energy gain is particularly great in solid-bowl screw centrifuges with such a design that the peripheral speed of the drum on the outer diameter of the drum during operation is more than 70 m / s, since the energy gain has a particularly significant effect in such centrifuges.

Further advantageous configurations can be found in the remaining subclaims.

The invention is described in more detail below with reference to the drawing. It shows:

1 shows the area of the weir of a solid bowl screw centrifuge according to the invention; Fig. 2 is a schematic view of a known solid bowl screw centrifuge with a weir designed as an overflow; and FIGS. 3, 4 are diagrams for illustrating effects of the prior art and the invention.

Fig. 2 is intended to illustrate the basic structure of a solid bowl screw centrifuge.

2 shows a solid-bowl screw centrifuge 1 with a drum 3, in which a screw 5 is arranged. The drum 3 and the screw 5 each have an essentially cylindrical section and a section which tapers conically here.

An axially extending central inlet pipe 7 is used to feed the centrifuged material via a distributor 9 into the centrifugal chamber 11 between the

Snail 5 and the drum 3.

If, for example, a muddy slurry is passed into the centrifuge, coarser solid particles settle on the drum wall. A liquid phase forms further towards the inside.

The screw 5 rotates at a somewhat lower or greater speed than the drum 3 and conveys the ejected solid to the conical section from the drum 3 to the solids discharge 13. The liquid, on the other hand, flows to the larger drum diameter at the rear end of the cylindrical section of the drum 3 and is derived there by or over a weir 15.

1 shows how such a weir 15 can be designed in the frame according to the invention. According to FIG. 1, the weir 15 has a passage 17 in an axial cover 19 of the drum 3, to which a combination of at least one or more nozzles 21 and an adjustable throttle device is assigned - here connected downstream.

The nozzles 21 are designed as screw bodies inserted into openings 23 of a stepped ring extension 25 that are configured in radial or inclined directions with respect to the drum axis, the bores or openings 27 of which are oriented perpendicular or at an angle to the drum axis S of the drum.

In the region or section adjoining the passage 17, the ring extension 25 has an inner diameter which corresponds to the outer diameter of the passage 17. The nozzle chamber 33 thus also has a diameter which corresponds to the diameter at the outer edge of the passage 17. In addition, the inlet openings 27 of the nozzles are preferably flush with the diameter of the overflow-like passage 17. This prevents dirt from accumulating in the nozzle chamber 33.

The ring extension 25 forms at its end facing away from the passage 21 an axial outlet 29, which is followed by the throttle disc 31, the distance to the outlet 29, for example in the manner described in DE 43 20 265 AI, with a wide variety of drive devices (here not shown) is changeable.

The distance of the throttle disc 31 to the outlet 29 is preferably changed by axial movement, in particular by axial displacement (which can also be achieved by pivoting) of the throttle disc 31 which is stationary relative to the rotating drum 3. Alternatively, it is also conceivable that the throttle disc 31 rotates with the drum 3 during operation (not shown). However, this solution is structurally more complex than the non-rotating variant. The term nozzle 21 is to be understood here in such a way that the bore 27 can have a diameter which is constant or variable over the axial extent of the opening. The nozzle 21 can also be designed as a bore in the ring extension 25, but the screw bodies offer the advantage of being interchangeable and thus of presetting the discharge quantity.

In the inner nozzle chamber 33, ribs (not shown here) can improve the delivery.

A preset basic quantity of liquid is derived from the drum 3 through the nozzles 21, depending on the design and diameter of the openings of the exchangeable screw body. The optimal alignment of the nozzles 21 for maximum energy savings can be determined with simple experiments.

With a solid bowl screw centrifuge for thickening a sludge in a ratio of 1:10 with a feed rate of 300 m ³ / h and a solids removal of 30 m ³ / h, for example, a nozzle design for 200 m ³ / h and a discharge of 70 m ³ / h h Recommended for regulating the level via the throttle disk 31.

If smaller capacities of, for example, 200 m ³ / h of feed are used, the amount of solids is, for example, 20 m ³ / h. With this quantity, a nozzle design for 110 m / h and, in turn, a discharge of 70 m / h for regulating the mirror via the throttle disk 31 would be recommended.

In order to adapt to different outputs, the nozzles 21 are simply exchanged for those with a different diameter. A complex exchange of expensive and complicated components is not necessary. The nozzles 21 are preferably arranged in a plane perpendicular to the drum axis at a distance from the outer drum radius or circumference of 25 to 75% of the drum radius, since the energy gain is greater the closer the nozzles 21 come to the drum circumference, but one Arranging further inwards offers the advantage that the diameter of the nozzles or their opening cross section can be larger than in the case of an arrangement further out, so that they clog less quickly. The area mentioned represents a good compromise between the effects mentioned.

As in DE 43 20 265 AI, a change in the discharge cross-section brings about a change in the liquid level in the drum 3 by adjusting the distance between the throttle disk 31 and the outlet 29. With the help of the throttle disk 31, the liquid level FS in the solid-bowl screw centrifuge is used in particular fine-tuned.

In the solid bowl screw centrifuge of FIG. 2, the following applies to the flowing particle stream Q _w over the weir 15 with a diameter d _w , the peripheral speed U _w at the weir diameter d _w being:

P (Q _w ) = px Q _w x U

In contrast to this, it applies to the invention that the major part of the volume flow at the diameter d _w is discharged through the nozzles 21 (volume flow Q _D ), and that another partial flow is discharged through the outlet 29 of a throttle disk 31.

If the liquid level in the chamber is kept at the weir diameter d _w by the throttle disk 31, the output is through the flow rate component Q _D flowing out of the nozzles 21 P (Q _D ) = px Q _D x U ² _w x A.

This formula is used to calculate a significant reduction in power consumption at a nozzle inclination angle between 0 and 30 °. A depends on the diameter and the cross-sectional shape of the nozzle 21, the level of the mirror in the drum and the beam angle of the nozzle jet. The cross-sectional geometry of the nozzles 21 can be designed as desired, e.g. round or square or in some other way.

Fig. 3 shows the conditions in a construction of the type of DE 43 20 265 AI without nozzles. The gap width s between the throttle plate 31 and drum weir outlet 17 is plotted on the X axis, and the volume flow VX is plotted on the Y axis. A volume flow V1X thus results for a gap width X. The larger the gap width S, the larger the volume flow , which is derived between the throttle plate 31 and the drum weir 17 from the drum 3. Conversely, the volume flow becomes smaller, the narrower the gap between throttle plate 31 and drum weir is set. At the same time, the pond depth increases within the decanter drum, i.e. the surface level moves further inwards as the gap decreases.

FIG. 4, on the other hand, shows the behavior of the volume flow V at the nozzles 21. Here, the volume flow increases with increasing pond depth due to the pressure in the liquid at the nozzle inlet. Both effects overlap. In practice, this extends the control range on the decanter according to the type of FIG. 1 up to double compared to a decanter without nozzles 21 according to the type of FIG. 3. LIST OF REFERENCE NUMBERS

Screw centrifuge 1

Drum 3

Snail 5

Inlet pipe 7

Distributor 9

Spin chamber 11

Solids discharge 13

Weir 15

Passage 17

Lid 19

Nozzles 21

Openings 23

Ring extension 25

Openings 27

Outlet 29

Throttle disc 31

Nozzle chamber 33

Symmetry and rotation axis S liquid level FS

Claims

claims

1. Solid bowl screw centrifuge with at least one weir (15) for discharging clarified liquid from a drum (3), which has a passage (17) to which a throttle device, in particular a throttle disc (31), is assigned, the distance to which Passage (17) is variable, characterized in that the passage (17) is further assigned at least one nozzle (21) rotating with the drum (3) or a plurality of nozzles for the outlet of the clarified liquid.

2. Solid bowl screw centrifuge according to claim 1, characterized by a design such that the nozzles (21) in a plane perpendicular to the drum axis are at a distance from the outer drum radius of 25 to 75% of the drum radius.

3. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the nozzles (21) have a diameter of more than two mm.

4. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the nozzles (21) are connected downstream of the passage (17) and that the throttle device (31) is in turn connected downstream of the nozzles (21).

5. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the nozzles (21) are designed to be exchangeable.

6. Solid bowl screw centrifuge according to claim 5, characterized in that the nozzles (21) are designed as screw bodies.

7. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that a plurality of the nozzles (21) are distributed on the drum cover (19) or a component (19) attached to the drum cover.

8. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the screw bodies are screwed into openings (23) of a ring extension (25) on the cover (19) of the drum (3).

9. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the nozzles (21) are arranged in a nozzle chamber (33), preferably formed by the ring extension (25), and in that the inner diameter of the nozzle chamber (33) corresponds to the outer diameter corresponds to the overflow-like passage (17).

10. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that inlet openings (27) of the nozzles are arranged flush with the diameter of the nozzle chamber (33).

11. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that bores (27) of the nozzles (21) are aligned at an angle to the axis of rotation (S) of the drum (3).

12. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the openings (27) of the nozzles (21) based on the

Direction of rotation of the drum are aligned backwards.

13. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the openings (27) of the nozzles (21) - based on a tangent to the drum surface in a plane perpendicular to the drum axis of rotation - have an inclination between zero and 30 °.

14. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the openings (27) of the nozzles (21) - with respect to the outer wall of the drum (3) - are directed radially outwards.

15. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the ring extension (25) at its end facing away from the passage (21) has or forms an axial outlet (29), which is followed by the throttle disc (31).

16. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the distance of the throttle disc (31) to the outlet (29) by axial movement, in particular by an axial displacement, the

Throttle disc (31) is variable.

17. Solid bowl screw centrifuge according to one of the preceding claims, characterized by a design such that the peripheral speed of the drum (3) on the outer diameter of the drum (3) in operation is more than 70m / s.

18. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the throttle disc (31) is designed as a stationary part relative to the drum (3) during operation of the centrifuge.

19. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the throttle disc (31) is formed as a part rotating with the drum during operation of the centrifuge.