WO1993020945A1 - Froth wash and froth removal system - Google Patents

Froth wash and froth removal system Download PDF

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Publication number
WO1993020945A1
WO1993020945A1 PCT/AU1993/000172 AU9300172W WO9320945A1 WO 1993020945 A1 WO1993020945 A1 WO 1993020945A1 AU 9300172 W AU9300172 W AU 9300172W WO 9320945 A1 WO9320945 A1 WO 9320945A1
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WO
WIPO (PCT)
Prior art keywords
froth
wash
troughs
zone
side walls
Prior art date
Application number
PCT/AU1993/000172
Other languages
French (fr)
Inventor
George Bodnaras
Original Assignee
Atomaer Pty Ltd
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 Atomaer Pty Ltd filed Critical Atomaer Pty Ltd
Publication of WO1993020945A1 publication Critical patent/WO1993020945A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
    • B03D1/00—Flotation
    • B03D1/08—Subsequent treatment of concentrated product
    • B03D1/082—Subsequent treatment of concentrated product of the froth product, e.g. washing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
    • B03D1/00—Flotation
    • B03D1/14—Flotation machines
    • B03D1/1418—Flotation machines using centrifugal forces
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
    • B03D1/00—Flotation
    • B03D1/14—Flotation machines
    • B03D1/1443—Feed or discharge mechanisms for flotation tanks
    • B03D1/1462—Discharge mechanisms for the froth
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
    • B03D1/00—Flotation
    • B03D1/14—Flotation machines
    • B03D1/1487—Means for cleaning or maintenance
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
    • B03D1/00—Flotation
    • B03D1/14—Flotation machines
    • B03D1/16—Flotation machines with impellers; Subaeration machines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
    • B03D1/00—Flotation
    • B03D1/02—Froth-flotation processes
    • B03D1/028—Control and monitoring of flotation processes; computer models therefor

Definitions

  • a froth wash apparatus for flotation apparatus comprising: an arm adapted to extend substantially horizontally over a zone through which froth passes in an upwards direction, said arm comprising a liquid distribution means for distributing froth wash liquid over the length of the arm, said liquid distribution means being provided with a flow control member connected thereto, said flow control member having a surface over which froth wash liquid released from the distribution means can flow into said froth zone whereby, in use, froth wash liquid can be deposited onto bubbles of said froth with reduced velocity.
  • Figure 4 is a perspective close-up view of the underside of the system of Figure 1 illustrating a preferred embodiment of the froth wash apparatus incorporated therein;
  • liquid distribution means 82 is in the form of a pipe, however it may take any suitable form for distributing liquid along the length of the arm.
  • the liquid distribution means 82 could incorporate a structure similar to the shroud 44 with liquid distribution means 42 of Figures 5 or 6.
  • An increased volume of froth wash liquid can be " distributed in the froth wash system by metering at the feed orifices 48 in the hub, rather than at the spray heads as in conventional systems.

Abstract

A froth wash and froth removal unit (10) for flotation apparatus comprises a froth removal apparatus (12) and a froth wash apparatus (14). The froth removal apparatus (12) comprises a plurality of elongate members in the form of troughs (16) adapted to extend across a froth zone of a flotation apparatus and arranged side by side, with the side walls of adjacent troughs defining gaps (18) between adjacent troughs. The troughs (16) are arranged radially from a central hub (20) to a circumferential rim (22). The troughs (16) are open at the rim (22) and closed at the hub (20), and the bottoms of the troughs (16) are inclined downwardly in a radially outwards direction so that froth passing upwards through the gaps (18) flows over the side walls of the troughs (16) and outwards towards the rim of the froth removal apparatus (12). Each trough (16) comprises a pair of side walls (24) which converge towards a lower edge (25) at the bottom of the trough whereby froth passing upwards through the gaps (18) is accelerated by the converging side walls of adjacent troughs. The converging side walls (24) of the troughs (16) cause a crowding effect so that the velocity of the froth flowing upwards through the gaps (18) is increased. The increased velocity helps to ensure free flow of froth over the side walls of the troughs (16) for collection. A significant advantage of the design of the troughs (16) is the increased froth removal lip-length that can be achieved.

Description

FROTH WASH AND FROTH REMOVAL SYSTEM
FIELD OF THE INVENTION
The present invention relates to a froth wash and froth removal system suitable for flotation apparatus and relates particularly, though not exclusively, to a froth wash apparatus, froth removal apparatus and froth collapsing apparatus for a mineral flotation apparatus . BACKGROUND TO THE INVENTION
Froth flotation is a process used for concentrating values, for example, from low-grade ores. After fine grinding the ore is mixed with water to form a slurry. Chemicals are added to the slurry to develop differences in hydrofobicity between the various mineral species present. The slurry is then copiously aerated and the preferred (aerophilic) mineral specie(s) cling(s) to the bubbles and float (s) as a mineralised froth which is collected for further processing.
In conventional flotation apparatus the froth is removed by mechanical skimming or simply by overflow at the mouth of the flotation vessel. It is known to employ a froth wash system for washing the mineral-laden air bubbles free of tailings matter. Some conventional froth wash systems comprise an array of water spray heads arranged above the froth zone to spray the water directly onto the froth while other systems employ "under froth" wash water methods with a variety of means of distributing the metered wash water within the froth layer.
A significant disadvantage of conventional froth removal and washing techniques is that a large proportion of the bubbles in the froth are disturbed and collapse prior to or during removal so that the mineral values fall back into the flotation vessel. This greatly reduces the efficiency of the flotation process and severely limits the proportion of mineral values that can be recovered from the slurry. SUMMARY OF THE INVENTION
The present invention was developed with a view to providing improved froth removal and/or washing so that the proportion of mineral values that can be recovered is increased. According to one aspect of the present invention there is provided a froth wash apparatus for flotation apparatus, the froth wash apparatus comprising: an arm adapted to extend substantially horizontally over a zone through which froth passes in an upwards direction, said arm comprising a liquid distribution means for distributing froth wash liquid over the length of the arm, said liquid distribution means being provided with a flow control member connected thereto, said flow control member having a surface over which froth wash liquid released from the distribution means can flow into said froth zone whereby, in use, froth wash liquid can be deposited onto bubbles of said froth with reduced velocity.
Typically said arm of the froth wash apparatus is one of a plurality of arms arranged to cover said zone through which the froth passes. Advantageously for circular froth zones said plurality of arms extend radially over said area from a central hub to a circumferential rim. Alternatively, for rectangular froth zones, said plurality of arms preferably extend in a parallel fashion from a suitably positioned wash liquid manifold, at one end of the arms, to a rim of the froth area.
In one embodiment said flow control member is a shroud covering said liquid distribution means and having a plurality of apertures provided therein for releasing said froth wash liquid into said froth zone.
Preferably said shroud comprises first and second side walls arranged to meet along a lower edge of the shroud to define a trough within the shroud extending substantially over the full length of the arm, said side walls being positioned relative to the distribution means so that froth wash liquid flows down an inner surface of said side walls towards the lower edge of the shroud.
Typically both said side walls have a substantially planar lower section and meet at an acute angle along said lower edge whereby a lower section of the shroud is substantially wedge-shaped. Preferably said plurality of apertures in the shroud are provided at spaced intervals along said lower edge and advantageously the spacing between apertures can be varied such that uniform distribution of wash liquid is achieved.
In its preferred form each of said plurality of apertures is provided with a lip extension whereby froth wash liquid passing through said apertures flows over the lip extension into the froth. Advantageously each said lip extension is substantially co-planar with one of said side walls, and adjacent lip extensions are co-planar with said first and second walls respectively.
Typically for circular froth zones said distribution means open into the central hub through a plurality of feed orifices whereby, in use, froth wash liquid can be metered into the distribution means from a central chamber within the hub. Preferably each distribution means is provided with a single elongate slot, or a plurality of apertures at spaced intervals, along an upper surface thereof.
In an alternative embodiment said liquid distribution means is adapted to extend substantially horizontally above said froth zone and said flow control member is suspended below the liquid distribution means and extends down into said froth zone.
Preferably said flow control member is substantially planar and is provided with a lip extension at a lower edge thereof extending obliquely from said flow control member to further decrease the velocity of the froth wash liquid flowing down said flow control member into the froth zone.
According to another aspect of the present invention there is provided a froth removal apparatus for flotation apparatus, the froth removal apparatus comprising: a plurality of elongate members adapted to extend across a froth zone of a flotation apparatus and defining a gap between adjacent members, the members being arranged to form inclined surfaces whereby, in use, froth passing through the gap can flow down the inclined surfaces to be collected for further processing.
Preferably said elongate members are in the form of troughs arranged side by side with the rims of adjacent troughs - - defining said gap and wherein the bottoms of the troughs are inclined to form said inclined surfaces.
Preferably for circular froth zones said plurality of troughs are arranged radially over said froth zone from a central hub to a circumferential rim. Typically said troughs are open at the rim and closed at the hub and said bottoms of the troughs are inclined downwardly in a radially outwards direction so that the froth flows towards the rim of the collector. In- an alternative embodiment the troughs are closed at the rim and open at the hub and said bottoms of the troughs are inclined downwardly in a radially inwards direction so that froth flows towards the hub of the collector. Alternatively, for rectangular froth zones, said plurality of troughs are preferably arranged in a parallel fashion over said froth zone to discharge towards one side of the froth zone, with the inclination of the trough bottoms being towards said one side of the froth zone.
Advantageously each trough comprises a pair of side walls arranged to meet along a lower edge at the bottom of the trough whereby froth passing upwards through the gap is accelerated by the converging side walls of adjacent troughs.
According to a still further aspect of the present invention there is provided a froth collapsing apparatus for collapsing froth in a flotation apparatus, the froth collapsing apparatus comprising: a motor driven impeller rotatably supported within a housing, the impeller being adapted to rotate about a central axis to define a froth collapsing zone wherein gas bubbles in the froth are caused to collapse and the gas is forcibly separated from the remainder of the froth whereby, in use, centrifugal forces cause the separated remainder to accumulate towards an outer periphery of the froth collapsing zone and onto an inner wall of the housing from where it can drain away for further processing. Preferably said impeller has at least two blades that rotate about a substantially vertical axis. The housing may have a centrally located aperture provided adjacent the underside of the impeller for admitting froth into said froth collapsing zone. The housing may be further provided with a bubble trap located above the impeller and adapted to inhibit any build-up of froth above the impeller.
Preferably all parts of the froth collapsing apparatus that come into contact with fast moving pulp and/or froth, are coated with or manufactured from an abrasion resistant material.
In the case where the flotation apparatus has a circular froth zone the froth collapsing apparatus is preferably located in the hub of the froth removal apparatus. In the case of a rectangular froth zone the froth collapsing apparatus is preferably located above the froth launder drain pipe.
According to another aspect of the present invention there is provided a froth wash and froth removal system for a flotation apparatus, the froth wash and removal system comprising a combination of a froth wash apparatus and a froth removal apparatus as described above.
Advantageously the froth wash and removal system also incorporates a froth collapsing apparatus as described above.
BRIEF DESCRIPTION OF THE DRAWINGS
In order to facilitate a fuller understanding of the invention preferred embodiments of the invention will now be described in detail, by way of example only, with reference to the accompanying drawings in which:
Figure 1 is a top perspective view of a preferred embodiment of a froth wash and froth removal system with lid .removed;
Figure 2 is an enlarged view of a pair of troughs of a froth removal apparatus incorporated in the froth wash and froth removal system of Figure 1;
Figure 3 is a part section side elevation of the froth wash and froth removal system of Figure 1;
Figure 4 is a perspective close-up view of the underside of the system of Figure 1 illustrating a preferred embodiment of the froth wash apparatus incorporated therein;
Figure 5 illustrates a single arm of the froth wash apparatus of Figure 4; Figure 6 illustrates a variant of a single arm of the froth wash apparatus;
Figure 7 illustrates another embodiment of the froth removal apparatus according to the invention; Figure 8 illustrates another embodiment of a froth wash apparatus; and.
Figure 9 illustrates an embodiment of a froth collapsing apparatus. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring to Figures 1, 3 and 4 in particular, a preferred embodiment of the froth wash and froth removal system 10 is illustrated which comprises a froth removal apparatus 12 and a froth wash apparatus 14. Although in this embodiment the froth removal apparatus 12 and froth wash apparatus 14 are incorporated in a single froth wash and froth removal unit 10, clearly the froth removal apparatus 12 may be provided separate from the froth wash apparatus if desired. Thus, for example, the froth removal apparatus 12 may be retrofitted to a flotation plant having a conventional froth wash apparatus already installed therein. The froth removal apparatus 12 and froth wash apparatus 14 can function substantially independently, however their incorporation in a single froth wash and froth removal unit 10 provides certain advantages which will become evident from the following description. A preferred form of froth removal apparatus 12 will now be described in detail with reference to Figures 1, 2 and 3.
As can be seen most clearly in Figure 1, the froth removal apparatus comprises a plurality of elongate members in the form of troughs 16 adapted to extend across a froth zone of a flotation apparatus (not shown) and arranged side by side, with the side walls of adjacent troughs defining a gap 18 between adjacent troughs. The bottoms of the troughs 16 are inclined to form inclined surfaces whereby froth passing through the gaps 18 can flow over the side walls of the troughs and down the inclined surfaces to be collected for further processing. In this embodiment, which is designed for a flotation apparatus with circular froth zone, the troughs 16 are arranged radially from a central hub 20 to a circumferential rim 22. The troughs 16 are open at the rim 22 and closed at the hub 20 and the bottoms of the troughs 16 are inclined downwardly in a radially outwards direction so that the froth flows towards the rim of the froth removal apparatus 12. Typically, a gutter (not shown) is provided around the periphery of the mouth of the flotation vessel within which the froth wash and froth removal unit 10 is received, so that froth flows out of the troughs 16 into the peripheral gutter to a drain where it is collected for further processing.
As can be seen more clearly in Figure 2, each trough 16 comprises a pair of side walls 24 which converge towards a lower edge 25 at the bottom of the trough whereby froth passing upwards through the gap 18 is accelerated by the converging side walls of adjacent troughs. Hence, the converging side walls 24 of the trough 16 cause a crowding effect so that the velocity of the froth flowing upwards through the gaps 18 is larger than that of the froth before it reaches the lower section of the froth removal apparatus 12. The increased velocity helps to ensure free flow of froth over the side walls of the troughs 16 for collection. As can be seen most clearly in Figure 1, the area of the gaps 18 is approximately equal to the area occupied by the troughs 16 so that the volume of froth that can be removed is maximised and froth travel distance minimised.
Referring to Figure 3 the froth removal apparatus 12 normally has a lid 26 that completely covers and encloses the troughs 16 to define a froth collection chamber 28. The provision of froth collection chamber 28 prevents exposure of the froth to atmosphere and provides a controlled environment for froth collection which helps to prevent the froth from collapsing prior to removal. The lid 26 is mounted on a plurality of brackets 30 so as to be supported a prescribed distance above the lip of the side walls of the troughs 16 and the circumferential rim 22. The lid 26 also helps to ensure that froth passing upwards through the gaps 18 moves sideways over the side walls of the troughs to be removed. In this way, the lid ensures migration of fine bubbles as well as heavier bubbles into the troughs 16 or over the circumferential rim into the peripheral gutter (not shown) .
A significant advantage of the design of the troughs 16 is the increased froth removal lip-length that can be achieved. In this embodiment, the effective froth removal lip- length is equal to the length of the side walls of the troughs 16 together with the sections of the circumferential rim 22 located in the gaps 18 between the troughs. The larger the lip-length the more efficient the froth removal apparatus. In other words, in this embodiment, not only is the froth able to flow over the side walls of the troughs 16 and hence into the peripheral gutter, but the froth can also flow over the circumferential rim 22 directly into the peripheral gutter or launder. Figure 7 illustrates another embodiment of the froth removal .apparatus 12 designed for flotation apparatus having a rectangular froth zone, in which the troughs 16 are arranged in parallel fashion over the froth zone. The bottoms of the troughs 16 are inclined towards one side of the froth zone and discharge into a launder 32. The troughs 16 of this embodiment are of similar design to that of Figure 2, and the apparatus 12 operates in a similar manner to that of Figures 1 and 2.
A preferred embodiment of the froth wash apparatus 14 will now be described with reference to Figures 3, 4 and 5 in particular. Referring to Figures 4 and 5, the froth wash apparatus 14 comprises a plurality of arms 40 adapted to extend substantially horizontally over a zone through which froth passes in an upwards direction, each arm comprising a liquid distribution means 42 for distributing froth wash liquid over the length of the arm. The liquid distribution means 42 is covered by a shroud 44 having a plurality of apertures 46 provided therein for releasing the froth wash liquid into the froth passing adjacent to the shroud. Shroud 44 acts as a flow control member in that inner surfaces of the shroud, over which froth wash liquid from the liquid distribution means 42 flows, slows the velocity of the liquid as it flows downwards under the influence of gravity. In this embodiment, the plurality of arms 40 of the froth wash apparatus are arranged radially over the froth zone from the central hub 20 to the circumferential rim 22 of the froth wash and froth removal unit.
The distribution means 42 are in the form of steel pipes 43 or pipes of other suitable material welded at one end to the central hub 20 and at the other end to the circumferential rim 22. The pipes 43 open into the central hub- through feed orifices 48, and open out into the peripheral gutter (not shown) through cleaning orifices 50 in the circumferential rim 22 (see Figure 1) . The cleaning orifices 50 are normally closed with a removable plug which can be removed to facilitate flushing and draining of the distribution lines for cleaning and maintenance purposes. Froth wash liquid is distributed along the length of the arms 40 through a plurality of apertures 52 provided at spaced intervals along an upper surface of the distribution pipes 43. Alternatively, the distribution lines 42 may be provided with one or more elongate slots along the upper surface thereof in order to distribute wash liquid evenly along the length of the arms 40. Froth wash liquid can be metered into the distribution pipes 43 from a central chamber within the hub 20, as will be described in more detail below.
Shroud 44 comprises first and second side walls 54, as can be seen most clearly in Figure 5, arranged to meet along a lower edge 56 of the shroud to define a channel within the shroud extending substantially over the full length of the arm 40. The side walls 54 are positioned relative to the distribution line 42 so that wash liquid flows down an inner surface of the side walls into the channel at the lower edge 56 of the shroud and out through the apertures 46 into the froth. The side walls 54 are formed from a single length of pressed sheet metal folded to form a diamond-shaped cross section. Both side walls 54 have a substantially planar lower section and meet at an acute angle along the lower edge 56 so that the lower section of the shroud 44 is substantially wedge- shaped. Hence, disturbance to the bubbles of froth passing upwards through the froth wash system 14 is minimised. Prior to folding of the sheet metal to form the shroud 44, the plurality of apertures 46 are drilled along a straight line that will form the lower edge 56 of the shroud
44. The apertures 46 are relatively large, typically 5mm holes, so that the possibility of blockage is minimised.
Furthermore, the apertures are provided at spaced intervals, with the spacing between apertures decreasing in a radially outwards direction along the shroud 44. In this manner the volume of wash water is distributed substantially evenly over the whole area of a circular froth zone. The froth wash water may have chemical additives, for example, a frother to enhance washing and to minimise disturbance to the bubbles. After the sheet metal has been folded into the diamond-shaped shroud 44 as illustrated in Figure 5, each of the apertures 46 is provided with a lip extension 58 in the form of small metal tabs welded adjacent to the apertures so that froth wash liquid passing through the apertures flows over the lip extensions into the froth. The lip extensions are substantially co-planar with the side walls 54, with adjacent lip extensions being arranged in alternate directions.
The net effect of having the distribution lines 42 covered by a shroud 44, arranging the side walls 54 of the shroud so that wash liquid flows down an inner surface of the side walls to the apertures 46, and having the apertures 46 provided with lip extensions 58, is to significantly reduce the velocity of the froth wash liquid to a minimum as it is deposited onto the froth bubbles. Hence, the disturbance to the bubbles caused by the release of the froth wash liquid is minimised without reducing the volume of froth wash liquid that can be released into the froth.
There are twenty four distribution lines arranged radially around the hub 20 with the feed orifices 48 staggered at the hub in order to maximise the number of arms 14 of the froth wash system thereby minimising the wash liquid velocity when discharging into the froth.
Referring to Figure 3, it can be seen how the hub 20 forms a central chamber 60 from which the froth wash water is fed into the distribution lines through the feed orifices 48. Froth wash liquid enters the chamber 60 through a feed port 62. The chamber 60 can be drained through drain hole 64 provided in the bottom of the chamber 60. The drain hole 64 is normally sealed with a plug 66 which is connected to a lid 68 of the chamber by tie rod 70. Hence, when the lid 68 is removed the plug 66 is automatically lifted and opens the drain hole 64 so that the froth wash water can drain out of the central chamber 60. Thus, any accumulation of sand or other contaminants which have settled within the central chamber 60 can be flushed out through drain hole 64, so that the possibility of the distribution lines 42 becoming clogged, or the apertures 52 therein becoming blocked, is substantially eliminated.
Figure 6 illustrates a variant of a froth wash arm
40 for the froth wash apparatus 14. The only difference between the arm 40 of Figure 6 and that of Figure 5 lies in the arrangement of the liquid distribution means 42 within the shroud 44. In this embodiment the distribution pipe 43 is replaced with a channel 45 welded to one of the side walls 54 through which the froth wash liquid can flow. The upper edge or lip of the channels 45 is spaced from the inner wall of the shroud 44 and forms an elongate weir or slot 47 extending along the length of the arm 40. Hence froth wash liquid is distributed along the length of the arms 40 through the slot
47. The wash liquid flows over the lip of the channel 45, down over the external surface of channel 45 and onto the side walls
54 of the shroud. Hence the flow control effect is substantially the same as with the distribution pipes 43 of
Figure 5, in reducing the velocity of the wash liquid. In other respects the construction and operation of the froth wash arm 40 of Figure 6 is identical to that of Figure 5.
Figure 8 illustrates one arm 81 of yet another embodiment of a froth wash apparatus, comprising a liquid distribution means 82 for distributing froth wash' liquid over the length of the arm 81. A flow control member in the form of curtain 84 is suspended below the liquid distribution means 82 and is adapted to extend down into the froth zone of a flotation apparatus (not illustrated) . In this embodiment, distribution means 82 is in the form of a pipe having a plurality of apertures 86 provided therein for releasing the froth wash liquid onto the curtain 84. The apertures 86 may be replaced with a single elongate slot or plural slots if preferred. Curtain 84 may be a flexible or rigid sheet of any suitable material having a wettable surface and is designed to allow the froth wash liquid to flow down into the froth zone in a fine sheet. For this purpose the wettable surface of curtain 84 is typically treated, for example, to produce a roughened surface, to increase the thickness of the boundary layer of liquid formed on the curtain and further slow down the velocity of the liquid flowing into the froth zone. Preferably the curtain 84 is also provided with lip extensions 86 at a lower edge thereof extending obliquely into the froth zone. The extensions 86 further decrease the velocity of the froth wash liquid so that it can be deposited onto bubbles of froth with minimum velocity.
In the illustrated embodiment liquid distribution means 82 is in the form of a pipe, however it may take any suitable form for distributing liquid along the length of the arm. For example, the liquid distribution means 82 could incorporate a structure similar to the shroud 44 with liquid distribution means 42 of Figures 5 or 6.
Typically the froth wash apparatus comprises a plurality of such arms 81 extending above the froth zone. One advantage of the froth wash apparatus of Figure 8 is that the distribution pipes 82 and curtain 84 are easily accessed for maintenance purposes. A further advantage is that the curtain 84 is self-cleaning. The curtain 84 is unaffected by scaling as any build-up of scale does not affect the operation of the curtain, indeed it may enhance it. Another advantage of having the liquid distribution means 82 located above the froth zone is that the froth does not have to travel around the pipes 82 and hence the bubbles are less likely to be disturbed.
A preferred embodiment of a froth collapsing apparatus according to the invention will now be described in greater detail with reference to Figure 9.
In Figure 9 a froth collapsing apparatus 90 is illustrated in part section view and comprises an impeller 92 rotatably supported within a housing 94 and driven by an electric motor 96. The impeller 92 has at least two blades 98 adapted to rotate about a substantially vertical central axis 100 to define a froth collapsing zone 102 wherein gas bubbles in the froth are caused to collapse and the gas is forcibly separated from the pulp or slurry, that in a mineral froth comprises the remainder of the froth. The housing 94 is provided with a first frusto-conical inner baffle 104 provided adjacent the underside of the impeller 92 and defining a first centrally located aperture 106 for admitting froth into the froth collapsing zone 102.
In use, froth entering the froth collapsing zone 102 collapses as it strikes the blades 98 of the impellor 92 and centrifugal forces cause the separated pulp to accumulate towards an outer periphery of the zone 102 and onto an inner wall of the housing 94 from where it can drain down over the first inner baffle 104, through aperture 106, into drain pipe 108 and away for further processing. The aperture 106 is sized to permit slurry/pulp drainage such that down flowing slurry does not obstruct the entering froth flow. There is of course no harm done, indeed it is desirable, if some of the froth collapses due to the down flowing slurry. Froth enters the housing 94 through a froth inlet or inlets 110 arranged around the outer periphery of the housing below the minimum level 112 of the froth layer which is to be collapsed. Preferably the plane of rotation of the impeller 92 also lies substantially below the level 112 of the' froth layer.
The gas that is forcibly separated from the pulp/ slurry is typically vented to atmosphere or for collection through a second centrally located aperture 114 provided about the impellor shaft 116 and formed by a second frusto-conical inner baffle 118 adjacent an upperside of the impellor 92. The second inner baffle 118 has a discharge outlet positioned above the froth level 112. A third frusto-conical inner baffle 120 provided between the upper side of the impellor 92 and the underside of the second inner baffle 118 defines a bubble trap 122 wherein any froth bubbles that escape upwards through the froth collapsing zone 102 are prevented from building up above the impellor or escaping from the housing 94. The third inner baffle 120 forms a third circular aperture 124 of larger diameter than the second aperture 114 formed by the second baffle 118. A gap provided between the outer periphery of impellor 92 and the inner wall of the housing 94 is sufficiently large to enable substantial gas-slurry separation andminimum slurry/pulp velocity before drainage occurs thereby also diminishing the power required to rotate the impellor 92. All parts of the apparatus 90 which are impacted by fast moving slurry/pulp and/or froth, including the blades 98 of the impellor and the inner wall of housing 94, are coated with or manufactured from abrasion resistant materials.
The froth collapsing apparatus 90 is typically provided in the central hub of the froth removal apparatus 12 in the case where the flotation vessel has a circular froth zone. On the other hand in the case where the froth zone is rectangular the froth collapsing apparatus is typically located above the froth launder drain pipe. Now that preferred embodiments of the froth removal apparatus 12, froth wash apparatus 14 and froth collapsing apparatus 90 have been described in detail, it will be evident that the described apparatus have significant advantages over conventional froth wash, froth removal and froth laundering apparatus, including the following: Froth Removal Apparatus
(1) The design of the troughs increases the effective lip-length of the froth removal lip. This has a marked effect on the quantity of material that can be recovered by flotation.
(2) The distance the froth is required to travel horizontally is minimised. In large conventional flotation units the distance the froth has to travel to the removal lip may be too great, leading to high shear stresses in the mineralised bubbles and bursting thereof. (3) Sideways movement of the froth is minimised. Froth is extremely brittle and sideways movement causes break up of the bubbles and loss of concentrate.
(4) The provision of a lid enclosing the froth collection chamber prevents exposure of the froth surface to the atmosphere. In conventional flotation apparatus the froth may be exposed for relatively prolonged periods to air movement, sunlight, rain, etc. leading to high evaporation rates and uncontrolled disturbances to the top bubble layer. Froth Wash Apparatus
(1) An increased volume of froth wash liquid can be " distributed in the froth wash system by metering at the feed orifices 48 in the hub, rather than at the spray heads as in conventional systems.
(2) The velocity of water deposition onto the froth bubbles is reduced to an absolute minimum and disturbance to the froth layer is minimised.
(3) The distribution lines can be easily flushed and drained and the relatively large apertures reduce the possibility of blockage.
Froth Collapsing Apparatus In prior art systems, after washing (if installed) and removal, the froth flows down suitably located launders where water sprays (launder water) are employed to forcibly collapse the froth to form deaerated pulp ready for further processing. The requirement for launder water stemming only from the need to collapse the removed froth leads to the following drawbacks: gradual decrease in pulp density (if several flotation stages are required by the concentration process) with the direct result that extra pulp pumping power is required; increased flotation equipment volumes to ensure suitable residence times; the prospect of using thickeners to enable further processing of the mineral pulp at reasonable densities; - use of larger quantities of water than otherwise required which could become an environmental limitation in particular plant locations.
The froth collapsing apparatus according to the invention can overcome the above disadvantages by diminishing or virtually eliminating the need for launder water.
In addition to the above, by incorporating the froth wash apparatus and the froth removal apparatus in a single froth wash and removal unit 10 the distance the washed froth bubbles have to travel is minimised. The radial arrangement of the troughs 16 of the froth removal apparatus and the arms 40 of the froth wash apparatus maintains the radial mobility of the froth and provides radial symmetrical flow.
Furthermore, the system is low maintenance with no moving parts and can be easily cleaned.
The illustrated embodiment of the froth removal unit 10 is intended to be mounted on top of a conventional flotation column 80 as illustrated in broken outline in Figure 3. However, the unit can also be modified so as to be movable vertically within the column, enabling the position of the froth removal system to be adjusted depending on the height of the froth generated within the column. In order to make the froth removal unit movable the radial troughs 16 need to be rearranged so that the froth flows towards the central hub for collection rather than towards the peripheral rim as in the above described embodiment.
In this alternative embodiment the troughs are closed at the rim and open at the hub and the bottoms of the troughs are inclined downwardly in a radially inwards direction so that the froth flows towards the hub of the collector. In order to efficiently remove the froth collected in the central hub for further processing a froth collapsing apparatus as described above may be provided within the central hub to break up the froth bubbles as they enter the hub.
The provision of a central drain for the values concentrate thus enables the froth removal apparatus to be movable within the flotation column, whereas the illustrated embodiment is necessarily fixed as the froth collected in the troughs 16 drains into a peripheral gutter or launder provided around the upper periphery of the column.
Now that embodiments of the froth removal apparatus, froth wash apparatus, a froth wash and removal unit incorporating both therein and a froth collapsing apparatus, have been described in detail it will be apparent to persons skilled in the relevant arts that numerous variations and modifications may be made, in addition to those already described, without departing from the basic inventive concepts. For example, it is not essential for the troughs 16 of the froth removal apparatus, or the arms 40 of the froth wash apparatus to be arranged radially, although this is the preferred arrangement for flotation apparatus having a circular froth zone. The troughs 16 and arms 40 may also be arranged in a linear array with suitable modifications. Furthermore, the actual shape and configuration of the troughs 16 and the arms 40 may vary considerably from that illustrated. For example, the trough 16 may be of U-shaped cross section. All such variations and modifications are to be considered within the scope of the present invention, the nature of which is to be determined from the foregoing description and the appended claims.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:
1. A froth wash apparatus for flotation apparatus, the froth wash apparatus comprising: an arm adapted to extend substantially horizontally over a zone through which froth passes in an upwards direction, said arm comprising a liquid distribution means for distributing froth wash liquid over the length of the arm, said liquid distribution means being provided with a flow control member connected thereto, said flow control member having a surface over which froth wash liquid released from the distribution means can flow into said froth zone whereby, in use, froth wash liquid can be deposited onto bubbles of said froth with reduced velocity.
2. A froth wash apparatus as claimed in claim 1, wherein said arm of the froth wash apparatus is one of a plurality of arms arranged to cover said zone through which the froth passes.
3. A froth wash apparatus as defined in claim 1, wherein said flow control member is a shroud covering said liquid distribution means and having a plurality of apertures provided therein for releasing said froth wash liquid into said froth zone.
4. A froth wash apparatus as defined in claim 3, wherein said shroud comprises first and second side walls arranged to meet along a lower edge of the shroud to define a trough within the shroud extending substantially over the full length of the arm, said side walls being positioned relative to the liquid distribution means so that froth wash liquid flows down an inner surface of said side walls towards the lower edge of the shroud.
5. A froth wash apparatus as defined in claim 4, wherein both said side walls have a substantially planar lower section and meet at an acute angle along said lower edge whereby a lower section of the shroud is substantially wedge-shaped.
6. A froth wash apparatus as claimed in claim 3 , wherein each of said plurality of apertures is provided with a lip extension whereby froth wash liquid passing through said apertures flows over the lip extension into the froth.
7. A froth wash apparatus as claimed in claim 3 , wherein said liquid distribution means is adapted to extend substantially horizontally above said froth zone and said flow control member is suspended below the liquid distribution means and extends down into said froth zone.
8. A froth wash apparatus as claimed in claim 7, wherein said flow control member is substantially planar and is provided with a lip extension at a lower edge thereof extending obliquely from said flow control member to further decrease the velocity of the froth wash liquid flowing down said flow control member into the froth zone.
9. A froth wash apparatus as claimed in claim 8, wherein said flow control member is in the form of a curtain having a wettable surface on which said froth wash liquid forms a thin film.
10. A froth removal apparatus for flotation apparatus, the froth removal apparatus comprising: a plurality of elongate members adapted to extend across a froth zone of a flotation apparatus and defining a gap between adjacent members, the members being arranged to form inclined surfaces whereby, in use, froth passing through the gap can flow down the inclined surfaces to be collected for further processing.
11. A froth removal apparatus as claimed in claim 10, wherein said elongate members are in the form of troughs arranged side by side with the rims of adjacent troughs defining said gap and wherein the bottoms of the troughs are inclined to form said inclined surfaces.
12. A froth removal apparatus as claimed in claim 11, wherein said plurality of troughs are arranged radially over said froth zone from a central hub to a circumferential rim.
13. A froth removal apparatus as claimed in claim 12, wherein said troughs are open at the rim and closed at the hub and said bottoms of the troughs are inclined downwardly in a radially outwards direction so that the froth flows towards the rim of the collector.
14. A froth removal apparatus as claimed in claim 11, wherein each trough comprises a pair of side walls arranged to meet along a lower edge at the bottom of the trough whereby froth passing upwards through the gap is accelerated by the converging side walls of adjacent troughs.
15. A froth collapsing apparatus for collapsing froth in a flotation apparatus, the froth collapsing apparatus comprising: a motor driven impeller rotatably supported within a housing, the impeller being adapted to rotate about a central axis to define a froth collapsing zone wherein gas bubbles in the froth are caused to collapse and the gas is forcibly separated from the remainder of the froth whereby, in use, centrifugal forces cause the separated remainder to accumulate towards an outer periphery of the froth collapsing zone and onto an inner wall of the housing from where it can drain away for further processing.
16. A froth collapsing apparatus as claimed in claim 15, wherein said impeller has at least two blades that rotate about a substantially vertical axis.
17. A froth collapsing apparatus as claimed in claim 16, wherein the housing has a centrally located aperture provided adjacent the underside of the impeller for admitting froth into said froth collapsing zone.
18. A froth collapsing apparatus as claimed in claim 17, wherein the housing is further provided with a bubble trap located above the impeller and adapted to inhibit any build-up of froth above the impeller.
19. A froth collapsing apparatus as claimed in claim 18, wherein all parts of the froth collapsing apparatus that come into contact with fast moving pulp and/or froth, are coated with or manufactured from an abrasion resistant material.
20. A froth wash and froth removal unit for a flotation apparatus, the unit comprising a combination of a froth wash apparatus as claimed in claim 1 and a froth removal apparatus as claimed in claim 10.
PCT/AU1993/000172 1992-04-16 1993-04-16 Froth wash and froth removal system WO1993020945A1 (en)

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US5746910A (en) * 1996-03-05 1998-05-05 Her Majesty The Queen In Right Of Canada, As Represented By The Minister Of Natural Resources Frothless flotation apparatus
US6095336A (en) * 1997-08-29 2000-08-01 Baker Hughes Incorporated Flotation cell with radial launders for enhancing froth removal
WO2007053879A1 (en) * 2005-11-08 2007-05-18 Newcastle Innovation Limited Method and apparatus for froth washing in flotation
US7328806B2 (en) * 2002-11-27 2008-02-12 University Of Illinois Apparatus for froth cleaning
CN100443192C (en) * 2006-10-26 2008-12-17 北京矿冶研究总院 Bubble pushing device of flotation machine
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EP2500102A1 (en) 2011-03-15 2012-09-19 Siemens Aktiengesellschaft Flotation apparatus with a fluid distribution element for creating a fluid flow towards the froth collecting device
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US5511669A (en) * 1993-09-06 1996-04-30 Supaflo Technologies Pty. Ltd Membrane washing apparatus for flotation device
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US6095336A (en) * 1997-08-29 2000-08-01 Baker Hughes Incorporated Flotation cell with radial launders for enhancing froth removal
US7328806B2 (en) * 2002-11-27 2008-02-12 University Of Illinois Apparatus for froth cleaning
US7770736B2 (en) 2005-11-08 2010-08-10 Newcastle Innovation Limited Method and apparatus for froth washing in flotation
WO2007053879A1 (en) * 2005-11-08 2007-05-18 Newcastle Innovation Limited Method and apparatus for froth washing in flotation
CN100443192C (en) * 2006-10-26 2008-12-17 北京矿冶研究总院 Bubble pushing device of flotation machine
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DE102008014791A1 (en) * 2008-03-18 2009-09-24 Siemens Aktiengesellschaft Flotation cell for the recovery of valuable material particles
US20120074046A1 (en) * 2009-06-09 2012-03-29 Outotec Oyj froth flotation method and an apparatus for extracting a valuable substance from a slurry
CN102802801A (en) * 2009-06-09 2012-11-28 奥图泰有限公司 A froth flotation method and an apparatus for extracting a valuable substance from a slurry
US8360246B2 (en) * 2009-06-09 2013-01-29 Outotec Oy Froth flotation method and an apparatus for extracting a valuable substance from a slurry
AU2009202281B2 (en) * 2009-06-09 2014-07-24 Metso Outotec Finland Oy A froth flotation method and an apparatus for extracting a valuable substance from a slurry
EP2500102A1 (en) 2011-03-15 2012-09-19 Siemens Aktiengesellschaft Flotation apparatus with a fluid distribution element for creating a fluid flow towards the froth collecting device
WO2012123258A1 (en) 2011-03-15 2012-09-20 Siemens Aktiengesellschaft Flotation device comprising a fluid distribution element for generating a flow that is directed at the foam collecting unit
CN106063474A (en) * 2016-07-29 2016-11-02 浙江省海洋水产养殖研究所 Fish recirculating aquaculture water treating pond
WO2019008214A1 (en) * 2017-07-04 2019-01-10 Outotec (Finland) Oy A froth flotation arrangement and a froth flotation method
WO2019008215A1 (en) * 2017-07-04 2019-01-10 Outotec (Finland) Oy A froth collection launder
CN110891689A (en) * 2017-07-04 2020-03-17 奥图泰(芬兰)公司 Foam collecting chute
CN110913991A (en) * 2017-07-04 2020-03-24 奥图泰(芬兰)公司 Froth flotation device and froth flotation method
US10828647B2 (en) 2017-07-04 2020-11-10 Outotec (Finland) Oy Froth collection launder
US11033909B2 (en) 2017-07-04 2021-06-15 Outotec (Finland) Oy Froth flotation arrangement and a froth flotation method
EA039490B1 (en) * 2017-07-04 2022-02-02 Оутотек (Финлэнд) Ой Froth flotation arrangement and froth flotation method
CN110891689B (en) * 2017-07-04 2022-05-17 奥图泰(芬兰)公司 Foam collecting chute
AU2021202923B2 (en) * 2017-07-04 2022-12-08 Outotec (Finland) Oy A froth flotation arrangement and a froth flotation method
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US20200391225A1 (en) * 2018-03-02 2020-12-17 Outotec (Finland) Oy Froth flotation cell
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