Device and Method for Separating a Suspension

Abstract

A sedimentation device for separating a solid-liquid suspension has a settling tank, a feed well, a feed pipe, an overflow collector and a mixing area. A pump is disposed in the overflow collector and overflow from the overflow collector can be fed through the pump to the mixing area. The solid-liquid suspension to be clarified can be diluted without affecting the sedimentation process, the chemicals can be used to the optimum, and the amount of overflow fed to the mixing area can be exactly determined.

Claims

1-14. (canceled)

15. A sedimentation device (1) device for separating a solid-liquid suspension, comprising a settling tank (2) defining an inside; a feed well (3) disposed on the inside of the settling tank (2); a feed pipe (4) comprising an inlet end (5) and an outlet end (6) communicating with the feed well (3); an overflow collector (7) disposed around a periphery of the settling tank (2) configured to collect overflow from the settling tank (2); and a mixing area (9) to which clarified liquid is fed from an upper part of the settling tank (2), wherein the mixing area (9) is disposed around the periphery of the settling tank (2), the inlet end (5) of the feed pipe (4) communicates with the mixing area (9), and overflow from the overflow collector (7) and the solid-liquid suspension to be separated are fed to the mixing area (9), a pump (8) is disposed in the overflow collector (7) for feeding overflow from the overflow collector (7) to the mixing area (9), a stilling chamber (10) having an overflow weir (11) is disposed between the mixing area (9) and the overflow collector (7), the overflow from the overflow collector (7) is fed to the stilling chamber (10), the overflow from the stilling chamber (10) is fed over the overflow weir (11) to the mixing area (9) forming a free surface (13), and a level measuring device (14) is assigned to the stilling chamber (10).

16. The sedimentation device (1) according to claim 15, wherein the level measuring device (14) an ultrasonic level measuring instrument, and a height of the free surface (13) can be measured in the stilling chamber (10) via the ultrasonic level measuring instrument.

17. The sedimentation device (1) according to claim 15, wherein the level measuring device (14) operates via one of static pressure measurement, capacitive measurement, measurement by use of a float switch, optical or acoustic measurement of surface area, and structured weir measurement.

18. The sedimentation device (11) according to claim 17, wherein the level measuring device (14) operates via Thomson weir measurement.

19. The sedimentation device (1) according to claim 15, wherein the overflow from the overflow collector (7) is brought to a lower part of the stilling chamber (10), and the overflow weir (11) is positioned in the upper part of the stilling chamber (10).

20. The sedimentation device (1) according to claim 16, wherein the overflow from the overflow collector (7) is brought to a lower part of the stilling chamber (10), and the overflow weir (11) is positioned in the upper part of the stilling chamber (10).

21. The sedimentation device (1) according to claim 15, wherein the pump (8) is positioned substantially horizontally, and the overflow from the overflow collector (7) is fed horizontally through the pump (8) to the stilling chamber

22. The sedimentation device (1) according to claim 19, wherein the pump (8) is positioned substantially horizontally, and the overflow from the overflow collector (7) is fed horizontally through the pump (8) to the stilling chamber (10).

23. The sedimentation device (1) according to claim 15, wherein the pump (8) disposed in the overflow collector (7) is an axial flow pump.

24. The sedimentation device (1) according to claim 15, wherein the overflow collector (7) comprises a first area (15) and a second area (16) that are separated from each other by a partition (12), the overflow can be fed from the first area (15) to the stilling chamber (10), and the overflow from the second area (16) can be discharged from the sedimentation device (1).

25. The sedimentation device (1) according to claim 16, wherein the overflow collector (7) comprises a first area (15) and a second area (16) that are separated from each other by a partition (12), the overflow can be fed from the first area (15) to the stilling chamber (10), and the overflow from the second area (16) can be discharged from the sedimentation device (1).

26. The sedimentation device (1) according to claim 19, wherein the overflow collector (7) comprises a first area (15) and a second area (16) that are separated from each other by a partition (12), the overflow can be fed from the first area (15) to the stilling chamber (10), and the overflow from the second area (16) can be discharged from the sedimentation device (1).

27. The sedimentation device (1) according to claim 15, wherein several mixing areas (9) are disposed around the periphery of the settling tank (2) and a pump (8) is assigned to each mixing area (9).

28. The sedimentation device (1) according to claim 16, wherein several mixing areas (9) are disposed around the periphery of the settling tank (2) and a pump (8) is assigned to each mixing area (9).

29. A method for diluting a solid-liquid suspension, comprising feeding the solid-liquid suspension to a sedimentation device (1) according to claim 1, collecting the overflow from the settling tank (2) in the overflow collector (7) disposed around the periphery of the settling tank (2), conveying the overflow from the overflow collector (7) to a mixing area (9) disposed around the periphery of the settling tank (2) via the pump (8) disposed in the overflow collector (7), feeding the solid-liquid suspension to the mixing area (9) and diluting the solid-liquid suspension in the mixing area to form a diluted suspension, and feeding the diluted suspension through the inlet end (5) of the feed pipe (4) to the feed well (3) communicating with the outlet end (6) of the feed pipe (4).

30. The method according to claim 29, comprising: conveying the overflow out from the overflow collector (7) into a stilling chamber (10) via the pump, and feeding the overflow from the stilling chamber (10) to the mixing area (9) over the overflow weir (11) to form a free surface (13).

31. The method according to claim 30, comprising determining an amount of overflow from the stilling chamber (10) fed to the mixing area (9) via measuring the filling level in the stilling chamber (10), wherein dilution of the solid-liquid suspension and the amount of overflow from the stilling chamber (10) transferred to the mixing area (9), respectively, are adjusted by adjusting the pump (8).

32. The method according to claim 29, comprising determining the solids content in the solid-liquid suspension before, in or after the mixing area (10), and the setting the desired dilution of the solid-liquid suspension by adjusting the pump (8).

33. The method according to claim 30, comprising conveying the overflow from the overflow collector (7) into the stilling chamber (10) substantially horizontally via the pump (8), wherein the overflow flows substantially vertically upwards through the stilling chamber (10).

34. The method according to claim 29, comprising feeding overflow from the first part (15) of the overflow collector (7) through the pump (8) to the stilling chamber (10); and discharging overflow from the second part (16) of the overflow collector (7) from the sedimentation device (1), wherein the overflow flowing into the first (15) and second (16) areas is divided by a partition (12) disposed in the overflow collector (7).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The invention will now be described using the examples in the drawings.

[0024] FIG. 1 shows a sedimentation device according to the state of the art.

[0025] FIG. 2 shows a top view of a sedimentation device, especially a first and second area of the overflow collector.

[0026] FIG. 3 shows an arrangement of a pump and mixing area in accordance with the disclosed embodiments.

[0027] FIG. 4 also shows another arrangement of a pump and mixing area in accordance with the disclosed embodiments.

[0028] FIG. 5 shows the arrangement of the pump and mixing area of FIG. 4, during operation.

DETAILED DESCRIPTION

[0029] FIG. 1 shows a sedimentation device 1 according to the state of the art, where a solid-liquid suspension is fed through an inlet end 5 of the feed pipe 4 to the settling tank 2. The outlet end 6 of the feed pipe 4 communicates with the feed well 3. Here, a mixing area 9 is formed in the feed well 3, where the suspension fed in through the feed pipe 4 and the overflow flowing out of the settling tank 2 and into the feed well 3 are mixed and diluted in the mixing area 9. The feed well 3 has an opening in the lower part and is connected hydraulically to the settling tank through this opening. Sedimentation takes place in the settling tank 2, where the solids from the solid-liquid suspension are separated downwards and concentrate in the lower part of the settling tank 2. Correspondingly low-solids and clarified suspension concentrates in the upper part of the settling tank 2. The overflow collector 7 is also disposed around the circumference of the settling tank 2 in the upper part of the settling tank 2. Here, clarified suspension flows out of the settling tank 2 as overflow into the overflow collector 7.

[0030] FIG. 2 shows a top view of a sedimentation device according to the disclosure, especially a first and second area of the overflow collector, where the first 15 and second 16 areas are divided by a partition 12. The overflow collector 7 is disposed around the circumference in the upper part of the settling tank. The partition 12 separates the first 15 and second 16 areas of the overflow collector. A partitionl2 of this kind can be designed simply as a partition plate or weir. All the overflow from the settling tank 2 flowing into the second part 16 of the overflow collector 7 can be discharged from the sedimentation device. All the overflow flowing out of the settling tank 2 into the first part 15 of the overflow collector 7 can be fed through the pump 8 to the mixing area 9, where the pump 8 is disposed in the overflow collector 7 designed as a suction area 17. First of all, the overflow is fed advantageously through the pump 8 to the stilling chamber 10 and out of the stilling chamber 10 on to the mixing area 9. The overflow that can be fed to the mixing area 9 is thus determined by means of the overflow flowing into the first area 15 of the overflow collector 7.

[0031] FIG. 3 shows an arrangement comprising a pump 8 and a mixing area 9, where the line of vision runs from the inside to the outside in radial direction. Here, an overflow collector 7 is disposed around the circumference in the upper part of the settling tank 2. The pump 8 is disposed in the overflow collector 7 designed as a suction area 17. The overflow from the overflow collector 7 flowing into the pump 8 is conveyed into the stilling chamber 10 through the pump. Advantageously, the pump 8 is disposed horizontally in the suction area 17 and the overflow is fed horizontally to the stilling chamber 10. It is a particular advantage if the pump 8 is designed as an axial flow pump. The overflow from the stilling chamber 10 can be fed to the mixing area 9 to form a free surface, where the stilling chamber 10 has an overflow weir 11 and the overflow from the stilling chamber 10 can be fed over the overflow weir 11 to the mixing area 9 to form the free surface. In addition, the solid-liquid suspension can be fed to the mixing area 9. The diluted solid-liquid suspension from the mixing area 9 is fed onwards through the inlet end 5 of the feed pipe 4 to the feed well 3 (not shown). In order to ensure that the pump 8 is always covered with liquid, the pump 8 is disposed advantageously in the suction area 17 vertically in such a way that the top edge of the pump is disposed vertically below the bottom edge of the overflow collector 7. In addition, a special controller, e.g., an immersion controller, can be provided in the suction area 17 in order to shut down the pump 8 if the overflow level in the suction area 17 is too low. The overflow conveyed horizontally through the pump 8 into the stilling chamber 10 is deflected in the stilling chamber 10 and guided vertically upwards. This is followed by overflow from the stilling chamber 10 flowing over the overflow weir 11 into the mixing area 9 to form a free surface.

[0032] FIG. 4 shows another arrangement comprising pump 8 and mixing area 9, where the line of vision points from the outside to the inside in radial direction. The wall of the settling tank 2 is not shown. The overflow from the overflow collector 7 can be fed to the pump 8, where the pump 8 is disposed advantageously in the suction area 17 vertically in such a way that the top edge of the pump 8 is disposed vertically below the bottom edge of the overflow collector 7. The pump 8 has a casing here. This makes it possible to effectively prevent air from swirling into the overflow taken in by the pump 8. The overflow is conveyed from the suction area 17 into the stilling chamber 10. Here, the pump 8 is disposed horizontally in the suction area 17 and the overflow is fed horizontally to the stilling chamber 10. It is a particular advantage if the pump 8 is designed as an axial flow pump. The overflow conveyed into the stilling chamber 10 is deflected in the stilling chamber 10 and guided vertically upwards. Additional built-in components in the stilling chamber 10 can help to homogenize the flow in the stilling chamber 10. Screen plates, screen panels, wire webs, for example—i.e., built-in components in general that cause a loss of pressure in flows when they pass through them, are suitable for this purpose. The overflow from the stilling chamber 10 into the mixing area 9 flows over the overflow weir 11 to form a free surface. The solid-liquid suspension can be fed to the mixing area 9, or the mixture of overflow and solid-liquid suspension can be fed onward through the inlet end 5 of the feed pipe 4 into the feed well 3.

[0033] FIG. 5 shows the arrangement according to the disclosure, comprising a pump 8 and mixing area 9, in operation and, in particular, the formation of a free surface 13 in the stilling chamber 10. The overflow flowing into the pump 8 over the overflow collector 7 is signified with a broken line. Here, the pump 8 is disposed vertically in the suction area 17 such that the top edge of the pump 8 is arranged vertically beneath the lower edge of the overflow collector 7. The overflow is conveyed from the suction area 17 into the stilling chamber 10. The overflow conveyed into the stilling chamber 10 is deflected in the stilling chamber 10 and guided vertically upwards. The overflow from the stilling chamber 10 into the mixing area 9 flows over the overflow weir 11 to form a free surface 13. The formation of a free surface 13 allows the filling level in the stilling chamber 10 to be measured, from which the quantity of overflow flowing out of the stilling chamber 10 into the mixing area 9 can be determined.

[0034] The disclosed embodiments offer numerous advantages. For example, the solid-liquid suspension to be clarified is diluted without affecting the sedimentation process in the settling tank in any way because the clarified liquid is taken from the overflow collector and is thus isolated from the settling tank and because dilution takes place upstream of the feed well. The invention features a minimum floor space requirement because no mixing area is required outside the sedimentation device. Similarly, the solid-liquid suspension is diluted by the overflow flowing into the mixing area only, so there is no need for a water supply outside the sedimentation device and dilution is possible with internal process water alone. As the solid-liquid suspension to be separated is diluted in a mixing area around the circumference of the settling tank, where it is advantageous to add chemicals in this mixing area, the chemicals added have longer reaction times before entering the feed well, which enables better use of the chemicals. In conformity with the overflow from the stilling chamber flowing over an overflow weir into the mixing area to form a free surface, it is possible to determine the overflow quantity fed to the mixing area easily and precisely. As the overflow is guided horizontally into the stilling chamber, this also allows a compact design and is essential in formation of a uniform, free surface in the stilling chamber.

REFERENCE NUMERALS

[0035] (1) Sedimentation device

[0036] (2) Settling tank

[0037] (3) Feed well

[0038] (4) Feed pipe

[0039] (5) Inlet end of the feed pipe

[0040] (6) Outlet end of the feed pipe

[0041] (7) Overflow collector

[0042] (8) Pump

[0043] (9) Mixing area

[0044] (10) Stilling chamber

[0045] (11) Overflow weir

[0046] (12) Partition

[0047] (13) Free surface

[0048] (14) Level measuring device

[0049] (15) First area of the overflow collector

[0050] (16) Second area of the overflow collector

[0051] (17) Suction area