WO2006056645A1 - Method and apparatus for concentrating thickener underflow - Google Patents

Method and apparatus for concentrating thickener underflow Download PDF

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Publication number
WO2006056645A1
WO2006056645A1 PCT/FI2005/000503 FI2005000503W WO2006056645A1 WO 2006056645 A1 WO2006056645 A1 WO 2006056645A1 FI 2005000503 W FI2005000503 W FI 2005000503W WO 2006056645 A1 WO2006056645 A1 WO 2006056645A1
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WO
WIPO (PCT)
Prior art keywords
slurry
cone
dewatering device
discharge cone
auxiliary
Prior art date
Application number
PCT/FI2005/000503
Other languages
French (fr)
Inventor
Sami HINDSTRÖM
Original Assignee
Outokumpu Technology Oyj
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Outokumpu Technology Oyj filed Critical Outokumpu Technology Oyj
Publication of WO2006056645A1 publication Critical patent/WO2006056645A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D21/00—Separation of suspended solid particles from liquids by sedimentation
    • B01D21/0012—Settling tanks making use of filters, e.g. by floating layers of particulate material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D21/00—Separation of suspended solid particles from liquids by sedimentation
    • B01D21/24—Feed or discharge mechanisms for settling tanks
    • B01D21/245—Discharge mechanisms for the sediments
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D21/00—Separation of suspended solid particles from liquids by sedimentation
    • B01D21/24—Feed or discharge mechanisms for settling tanks
    • B01D21/2488—Feed or discharge mechanisms for settling tanks bringing about a partial recirculation of the liquid, e.g. for introducing chemical aids

Definitions

  • This invention relates in general to solid-liquid separation. More specifically, it relates to a thickening apparatus and a thickening method for concentrating mineral slurries.
  • the rate of settling is often increased using optimized amount and type of flocculating agents.
  • the maximum concentration of solids obtained in the underflow cone is actually delimited by the flocculation, since water gets captured between colloidal solid particles.
  • the apparatus and the method are suitable for thickening minerals containing aqueous slurries.
  • the invention is especially applicable in increasing the solid content of tailings of high-rate thickeners or clarifiers.
  • High-rate thickeners and clarifiers are used in applications where flocculants can be used in the process and where the feed rate to the thickener does not vary substantially over a short period of time.
  • a conventional apparatus for producing a higher underflow density is to provide a high compression zone in the bottom area or the discharge cone of the thickener or clarifier tank.
  • the draw back of this approach is that it requires a considerable higher and heavier tank construction that increases the cost of the equipment and results often in awkward process conditions.
  • a thickening apparatus adapted to concentrate solids, such as minerals, containing slurry
  • the thickening apparatus comprising a circular tank with a feedwell and peripheral weir overflow, a discharge cone and a discharge line arranged to the discharge cone.
  • the present invention is characterized in that a pump is adapted to receive the concentrated slurry from the discharge cone and to feed it to a concentrating device for further concentrating the slurry and means for returning at least part of the further concentrated slurry into the discharge cone.
  • the pump is preferably a centrifugal pump, wherein the slurry is subjected to mechanical action so as the colloidal solid particles or lumps collapse and the water captured in the slurry is released for the further concentrating step.
  • the concentrating device is a flow-through thickening device, such as a flow- through filtering device.
  • flow- through thickening device means an apparatus for removing water from a flowing slurry stream.
  • An example of the flow-through dewatering device applicable in our invention is a device that comprises a filter tube with an inlet for the slurry and an outlet for the concentrated slurry and having a portion that is fluid permeable, through which filter tube the slurry is conducted, and a filter housing enclosing part of the filter tube and comprising an outlet for the filtrate.
  • the pump that is adapted to pump the slurry to the flow-through thickening device is preferably capable of producing such a high output pressure for the slurry so as to make the slurry to flow through the auxiliary thickening device and back to the discharge cone of the thickener.
  • a returning line for conducting the further concentrated slurry back to the discharge cone is arranged to the auxiliary thickening device.
  • a method of increasing solid content of slurry in a thickener discharge cone when the thickener comprises a tank with a feedwell and peripheral weir overflow, a discharge cone and a discharge line arranged to the discharge cone is also provided.
  • the method of this invention is characterized in that thickened slurry is withdrawn from the discharge cone to an auxiliary dewatering device for further thickening the slurry and at least part of the further thickened slurry is returned to the discharge cone.
  • the thickener operates in a continuous mode wherein slurry is fed continuously into the tank and the amount of solids fed into the tank equals with the amount of solids continuously withdrawn from the tank via the discharge cone.
  • the amount of solids exiting along the overflow can be considered negligible in this context.
  • the amount of solids conducted through the pump and the flow- through dewatering device is preferably between two and four times, most preferably three times, the amount of the solids fed into the thickening tank.
  • the solid content of the feed of the thickener is typically between 5 and 20 percents.
  • the filtering device is capable of reducing the water content of the slurry preferably by at least 0.5 percents, most preferably by 2 - 5 percents.
  • the filtering device is preferably provided with means for producing self- cleaning action wherein the solid cake deposited on the surface of the filtering media can be removed during the operation of the filter device.
  • the auxiliary densification step is utilized intermittently, wherein the slurry form the discharge cone is withdrawn via the pump into the auxiliary dewatering device periodically depending on the development of the solid contents of the slurry in the discharge cone.
  • the recycling of the slurry through the dewatering device of the present invention is ceased.
  • the auxiliary dewatering step is employed accordingly.
  • a part of the slurry exiting the auxiliary dewatering device is withdrawn and conducted to further processing or admixed with the slurry withdrawn via the outlet line of the discharge cone.
  • Part of the dewatered slurry is conducted back to the discharge cone to increase the solid content of the slurry in the cone.
  • Fig. 1 is a schematic presentation of the thickening apparatus according to the present invention.
  • the thickening apparatus comprises a thickener 10 with a circular tank and an underflow cone 18.
  • Flocculating agent is mixed to the slurry, normally during feeding the slurry into the tank via a feedwell that is arranged above the liquid level of the tank.
  • the flocculating agent promotes the settling of the mineral slurry on the bottom of the tank and in the underflow cone.
  • the solid concentration of the slurry in the underflow cone 18 settles typically to around 50 - 60 percents. When auxiliary concentrating means of the present invention is used, solid concentration of 60 - 65 percents is achieved in the underflow cone 18.
  • the concentrated slurry is withdrawn from the underflow cone 18 via an outlet line 13.
  • an outlet line 14 adapted to the underflow cone 18 to feed the slurry to a centrifugal pump 11 for subjecting the slurry for mechanical action and to feed the slurry to a flow-through filtering device 12.
  • the filtering device12 the water that is released in the pump 11 is at least partially removed from the slurry.
  • the slurry that is further concentrated in the filter device 12 is returned via line 15 to the underflow cone 18.
  • the slurry flow that is concentrated in the filter device 12 may be at least partially withdrawn via an outlet line 19 for further processing or to be admixed to the slurry withdrawn via line 13 from the discharge cone 18. According to the present invention, at least part of the concentrated slurry is returned via line 15 to the thickener tank.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Separation Of Suspended Particles By Flocculating Agents (AREA)

Abstract

The invention relates to an apparatus and a method of increasing the solid content of slurry in a thickener underflow cone. Thickened slurry is withdrawn from the discharge cone (18) to an auxiliary dewatering device (12) for further thickening the slurry and at least part of the further thickened slurry is returned to the discharge cone.

Description

METHOD AND APPARATUS FOR CONCENTRATING THICKENER UNDERFLOW
This invention relates in general to solid-liquid separation. More specifically, it relates to a thickening apparatus and a thickening method for concentrating mineral slurries.
Since coal and ores are processed almost exclusively in aqueous liquids, solid- liquid separation is an essential process step in the beneficiation of coal and ores. In minerals processing, gravity is widely used to concentrate suspended solids. Where the solids are colloidal, flocculants will improve operation by causing the colloids to form agglomerates or flocculi of much larger size that will settle at reasonable rates. Thickeners concentrate the solids to the thickener underflow. Normally the solids concentration in the underflow is less than the maximum possible concentration obtainable by sedimentation.
Conventional thickeners used in minerals processing consist of a circular tank with a central feedwell and peripheral weir overflow. Although the overflow must be of reasonable clarity, the emphasis is on underflow concentration. A rake is arranged to move the viscous solids settled on the bottom of the thickener towards an underflow cone positioned in the center of the thickener tank. The concentrated slurry is withdrawn via an outlet line from the underflow cone.
The rate of settling is often increased using optimized amount and type of flocculating agents. However, in certain circumstances, the maximum concentration of solids obtained in the underflow cone is actually delimited by the flocculation, since water gets captured between colloidal solid particles.
Therefore, further thickening operation is necessary, when higher solid content is needed.
The object of this invention is to provide a thickening apparatus having auxiliary means for concentrating the slurry in the underflow cone. Another object of this invention is to produce a method of increasing the solid content of slurry in a thickener underflow cone.
These above mentioned objects are achieved by an apparatus and a method described later in the independent claims. Other advantageous embodiments of the invention are presented in the dependent claims.
The apparatus and the method are suitable for thickening minerals containing aqueous slurries. The invention is especially applicable in increasing the solid content of tailings of high-rate thickeners or clarifiers. High-rate thickeners and clarifiers are used in applications where flocculants can be used in the process and where the feed rate to the thickener does not vary substantially over a short period of time.
A conventional apparatus for producing a higher underflow density is to provide a high compression zone in the bottom area or the discharge cone of the thickener or clarifier tank. However, the draw back of this approach is that it requires a considerable higher and heavier tank construction that increases the cost of the equipment and results often in awkward process conditions.
In accordance with the present invention, there is provided a thickening apparatus adapted to concentrate solids, such as minerals, containing slurry, the thickening apparatus comprising a circular tank with a feedwell and peripheral weir overflow, a discharge cone and a discharge line arranged to the discharge cone. The present invention is characterized in that a pump is adapted to receive the concentrated slurry from the discharge cone and to feed it to a concentrating device for further concentrating the slurry and means for returning at least part of the further concentrated slurry into the discharge cone.
The pump is preferably a centrifugal pump, wherein the slurry is subjected to mechanical action so as the colloidal solid particles or lumps collapse and the water captured in the slurry is released for the further concentrating step. The concentrating device is a flow-through thickening device, such as a flow- through filtering device. In context of the present invention, the term flow- through thickening device means an apparatus for removing water from a flowing slurry stream. An example of the flow-through dewatering device applicable in our invention is a device that comprises a filter tube with an inlet for the slurry and an outlet for the concentrated slurry and having a portion that is fluid permeable, through which filter tube the slurry is conducted, and a filter housing enclosing part of the filter tube and comprising an outlet for the filtrate.
The pump that is adapted to pump the slurry to the flow-through thickening device is preferably capable of producing such a high output pressure for the slurry so as to make the slurry to flow through the auxiliary thickening device and back to the discharge cone of the thickener. A returning line for conducting the further concentrated slurry back to the discharge cone is arranged to the auxiliary thickening device.
In accordance with the present invention, there is also provided a method of increasing solid content of slurry in a thickener discharge cone when the thickener comprises a tank with a feedwell and peripheral weir overflow, a discharge cone and a discharge line arranged to the discharge cone. The method of this invention is characterized in that thickened slurry is withdrawn from the discharge cone to an auxiliary dewatering device for further thickening the slurry and at least part of the further thickened slurry is returned to the discharge cone.
According to one preferred embodiment of the method of the present invention, the thickener operates in a continuous mode wherein slurry is fed continuously into the tank and the amount of solids fed into the tank equals with the amount of solids continuously withdrawn from the tank via the discharge cone. The amount of solids exiting along the overflow can be considered negligible in this context. The amount of solids conducted through the pump and the flow- through dewatering device is preferably between two and four times, most preferably three times, the amount of the solids fed into the thickening tank. The solid content of the feed of the thickener is typically between 5 and 20 percents. The filtering device is capable of reducing the water content of the slurry preferably by at least 0.5 percents, most preferably by 2 - 5 percents. The filtering device is preferably provided with means for producing self- cleaning action wherein the solid cake deposited on the surface of the filtering media can be removed during the operation of the filter device.
According to another preferred embodiment of the present invention, the auxiliary densification step is utilized intermittently, wherein the slurry form the discharge cone is withdrawn via the pump into the auxiliary dewatering device periodically depending on the development of the solid contents of the slurry in the discharge cone. When the solid contents of the slurry in the discharge cone meets the required density, the recycling of the slurry through the dewatering device of the present invention is ceased. When the density of the slurry in the discharge cone descents below a target value, the auxiliary dewatering step is employed accordingly.
According to one more embodiment of the present invention a part of the slurry exiting the auxiliary dewatering device is withdrawn and conducted to further processing or admixed with the slurry withdrawn via the outlet line of the discharge cone. Part of the dewatered slurry is conducted back to the discharge cone to increase the solid content of the slurry in the cone.
The invention is described in more detail referring to Fig. 1 , which is a schematic presentation of the thickening apparatus according to the present invention.
The thickening apparatus according to one preferred embodiment of the present invention comprises a thickener 10 with a circular tank and an underflow cone 18. Flocculating agent is mixed to the slurry, normally during feeding the slurry into the tank via a feedwell that is arranged above the liquid level of the tank. The flocculating agent promotes the settling of the mineral slurry on the bottom of the tank and in the underflow cone. The solid concentration of the slurry in the underflow cone 18 settles typically to around 50 - 60 percents. When auxiliary concentrating means of the present invention is used, solid concentration of 60 - 65 percents is achieved in the underflow cone 18.
The concentrated slurry is withdrawn from the underflow cone 18 via an outlet line 13. For further concentrating, i.e. dewatering the slurry, there is an outlet line 14 adapted to the underflow cone 18 to feed the slurry to a centrifugal pump 11 for subjecting the slurry for mechanical action and to feed the slurry to a flow-through filtering device 12. In the filtering device12, the water that is released in the pump 11 is at least partially removed from the slurry. The slurry that is further concentrated in the filter device 12 is returned via line 15 to the underflow cone 18.
The slurry flow that is concentrated in the filter device 12 may be at least partially withdrawn via an outlet line 19 for further processing or to be admixed to the slurry withdrawn via line 13 from the discharge cone 18. According to the present invention, at least part of the concentrated slurry is returned via line 15 to the thickener tank.
While the invention has been described with reference to its preferred embodiments, it is to be understood that modifications and variations will occur to those skilled in the art. Such modifications and variations are intended to fall within the scope of the appended claims.

Claims

CLAIMS:
1. A thickening apparatus adapted to concentrate solids, such as minerals containing slurry, the thickening apparatus comprising a tank with a feedwell and peripheral weir overflow, a discharge cone and a discharge line arranged to the discharge cone, characterized in that a pump is adapted to receive the concentrated slurry from the underflow cone and to feed it to an auxiliary concentrating device for further concentrating the slurry and means for returning at least part of the further concentrated slurry into the discharge cone is arranged to the auxiliary concentrating device.
2. The thickening apparatus according to claim 1 , characterized in that the pump is a centrifugal pump causing an mechanical action to the slurry to collapse colloidal particles or lumps to release captured water therein.
3. The thickening apparatus according to claim 1 , characterized in that the auxiliary concentrating device is a flow-through dewatering device.
4. The thickening apparatus according to claim 3, characterized in that the flow-through dewatering device is a filtering apparatus that comprises an inlet for the slurry, an outlet for the concentrated slurry, an outlet for a permeate, a filter housing, a fluid permeable filter tube through which the slurry is conducted.
5. The thickening apparatus according to claim 4, characterized in that the flow-through filtering apparatus is provided with means for producing self-cleaning action wherein the solid cake deposited on the surface of the filtering media is removed during the operation of the filter device.
6. A method of increasing solid content of slurry in a thickener discharge cone when the thickener comprises a tank with a feedwell and peripheral weir overflow, a discharge cone and a discharge line arranged to the discharge cone, characterized in that thickened slurry is withdrawn from the discharge cone to an auxiliary dewatering device for further thickening the slurry and at least part of the further thickened slurry is returned to the discharge cone.
7. The method according to claim 6, characterized in that the auxiliary dewatering device is a flow-through dewatering device.
8. The method according to claims 6 and 7, characterized in that the thickened slurry is withdrawn continuously into the auxiliary dewatering device.
9. The method according to claims 6 and 7, characterized in that the thickened slurry is withdrawn intermittently into the auxiliary dewatering device.
10. The method according to claims 6 and 7, characterized in that the amount of solids conducted through the pump and the flow-through dewatering device is between two and four times, preferably three times, the amount of the solids fed into the thickening tank.
11. The method according to claim 6, characterized in that the auxiliary dewatering device is a flow-through filtering device.
12. The method according to claim 11 , characterized in that the flow- through filtering device is provided with means for producing self-cleaning action wherein the solid cake deposited on the surface of the filtering media is removed during the operation of the filter device.
13. The method according to claim 6, characterized in that the flow- through dewatering device is capable of reducing the water content of the slurry at least by 0.5 percents, preferably by 2 to 5 percents.
14. The method according to claim 6, characterized in that part of the slurry exiting the auxiliary dewatering device is withdrawn and conducted to further processing or admixed with the slurry withdrawn via the outlet line of the discharge cone and part of the dewatered slurry is conducted back to the discharge cone to increase the solid content of the slurry in the cone.
PCT/FI2005/000503 2004-11-26 2005-11-24 Method and apparatus for concentrating thickener underflow WO2006056645A1 (en)

Applications Claiming Priority (2)

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FI20041519 2004-11-26
FI20041519A FI20041519A (en) 2004-11-26 2004-11-26 Method and apparatus for concentrating the thickener undercurrent

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WO2006056645A1 true WO2006056645A1 (en) 2006-06-01

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11708286B2 (en) 2020-08-19 2023-07-25 Marmon Industrial Water Llc High rate thickener and eductors therefor

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1261913A (en) * 1968-03-21 1972-01-26 English Clays Lovering Pochin Improvements in or relating to the treatment of mineral effluents
GB1268806A (en) * 1968-08-16 1972-03-29 Exxon Research Engineering Co A method for discharging of solids from a liquid stream and apparatus therefor
US3849310A (en) * 1971-01-14 1974-11-19 Technical Mij Bergmann Nv Method and apparatus for separating particles from a liquid
US4621928A (en) * 1983-11-22 1986-11-11 Vlt Gesellschaft Fur Verfahrenstechnische Entwicklung Mbh Treatment system and method for fluids containing particulate matter
US20010017161A1 (en) * 1999-03-15 2001-08-30 Alcan International Limited Transfer of shear-thinning slurries

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1261913A (en) * 1968-03-21 1972-01-26 English Clays Lovering Pochin Improvements in or relating to the treatment of mineral effluents
GB1268806A (en) * 1968-08-16 1972-03-29 Exxon Research Engineering Co A method for discharging of solids from a liquid stream and apparatus therefor
US3849310A (en) * 1971-01-14 1974-11-19 Technical Mij Bergmann Nv Method and apparatus for separating particles from a liquid
US4621928A (en) * 1983-11-22 1986-11-11 Vlt Gesellschaft Fur Verfahrenstechnische Entwicklung Mbh Treatment system and method for fluids containing particulate matter
US20010017161A1 (en) * 1999-03-15 2001-08-30 Alcan International Limited Transfer of shear-thinning slurries

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11708286B2 (en) 2020-08-19 2023-07-25 Marmon Industrial Water Llc High rate thickener and eductors therefor

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FI20041519A0 (en) 2004-11-26
FI20041519A (en) 2006-05-27

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