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EP0954379A2 - Appareil et procede de flottation induite avec insufflation d'air - Google Patents

Appareil et procede de flottation induite avec insufflation d'air

Info

Publication number
EP0954379A2
EP0954379A2 EP98904132A EP98904132A EP0954379A2 EP 0954379 A2 EP0954379 A2 EP 0954379A2 EP 98904132 A EP98904132 A EP 98904132A EP 98904132 A EP98904132 A EP 98904132A EP 0954379 A2 EP0954379 A2 EP 0954379A2
Authority
EP
European Patent Office
Prior art keywords
cone
shaped
annular channel
liquid
funnel
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP98904132A
Other languages
German (de)
English (en)
Inventor
Marko Zlokarnik
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
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
Priority claimed from DE19702181A external-priority patent/DE19702181A1/de
Priority claimed from DE1997119539 external-priority patent/DE19719539A1/de
Application filed by Individual filed Critical Individual
Publication of EP0954379A2 publication Critical patent/EP0954379A2/fr
Withdrawn legal-status Critical Current

Links

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
    • B03D1/14—Flotation 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
    • B03D1/14—Flotation machines
    • B03D1/24—Pneumatic
    • B03D1/247—Mixing gas and slurry in a device separate from the flotation tank, i.e. reactor-separator type
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/24—Treatment of water, waste water, or sewage by flotation
    • 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
    • B03D1/1412—Flotation machines with baffles, e.g. at the wall for redirecting settling solids
    • 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
    • B03D1/1493—Flotation machines with means for establishing a specified flow pattern

Definitions

  • the present invention concerns induced air flotation.
  • a so-called induced air flotation process has been devised.
  • a self-aspirating and radially discharging aeration device in the form of a funnel-shaped nozzle is known, such as was described in European Patent No. 0 035 243, issued to BAYER AG, D - Leverkusen (Inventor: M. Zlokarnik) and dated 7 May 1986.
  • the nozzle consists of a deflecting cone which is arranged in a funnel-shaped housing thus forming an annular channel in the space between the cone and the funnel . This channel provides a Venturi-type confuser/diffuser.
  • a liquid propulsion nozzle line is placed above the top of the cone.
  • the liquid jet impinges against the deflecting cone, is fanned out by it, and becomes uniformly distributed over the whole cross- section of the annular channel.
  • the air which is sucked into the mixing chamber, becomes intimately mixed with the liquid and discharged over the whole circumference of the deflecting cone, forming a free jet of the gas/liquid dispersion, which is afterwards uniformly distributed over the bottom of the cell.
  • This funnel-shaped nozzle produces relatively tiny gas bubbles of approximately 200 ⁇ m and distributes them evenly over the floor of the flotation cell .
  • This technology has been successfully applied in many industrial tasks, see for example, M. Zlokarnik, "New Approaches in Flotation Processing and Waste Water Treatment in the Chemical IndustryX in Ger. Chem. Eng. 5 (1982) 2, 109-115 and Kern. Ind. (Zagreb) 34 (1985) 1, 1-6.
  • An example of a large- scale application of this technology is the recovery of silver salts from washwaters of a large film factory as described in European Patent No. 0 059 227 issued to AGFA Leverkusen, and dated 24 April 1984.
  • the subsequent sludge- sedimentation causes serious problems. This is likely a result of dissolved C0 2 which desorbs and therefore hinders the sedimentation process.
  • flotation should therefore be carried out continuously, which requires a completely new concept for the flotation cell.
  • the flotation cell is subdivided into two different spaces by inserting an inner vessel concentrically into a larger vessel .
  • the inner vessel is equipped with the funnel-shaped nozzle and serves as the actual flotation cell .
  • an annulus is formed, thus enabling vertical liquid flow from top to bottom.
  • the funnel-shaped nozzle produces gas bubbles that are too coarse to ensure satisfactory separation.
  • the liquid propulsion jet in the annular space of the funnel-shaped nozzle must therefore be tuned to provide the ut ost shear rate.
  • This task cannot be accomplished by an increase in suction alone, since it hardly makes any sense to increase the suction of the funnel-shaped nozzle while at the same time choking the gas throughput as it is done in funnel-shaped nozzles with a constant hydraulic cross- sectional area (see M. Zlokarnik and J. Susa, in "Selbstansaugende und radialstrahlende Trichtesduese” , Chem. -Ing. -Techn. 68 (1996) 12, 1572-1574).
  • the first disadvantage is the fact that the flotate (froth) is pushed by the skimmer over the whole cross- sectional area of the cell. This perturbs the liquid motion in the annulus and has the disadvantage that parts of the compacted flotate may sediment before they can be removed from the rim of the cell.
  • the present invention aims at purposeful changes of the funnel-shaped nozzle and of the flotation cell to eliminate these disadvantages.
  • the present invention is an aeration device for inducing a liquid/gas dispersion which includes a cone- shaped deflecting element arranged inside of and spaced apart from a funnel-shaped outer casing such that an annular channel is formed between the cone and the funnel .
  • a liquid propulsion nozzle is disposed adjacent the apex of the funnel and arranged to cause the liquid exiting therefrom to impinge upon the deflecting cone and to be fanned out thereby.
  • a first novel aspect of the present invention are directed to disposing one or more trip edges within the annular channel.
  • the trip edge(s) prevent formation of a laminar boundary layer along the deflecting element, thereby promoting turbulence in the fluid flow within the annular channel.
  • the trip edges also promote turbulence within the annular channel itself, improving the suction action of the funnel shaped nozzle and thereby also strongly intensifying the shear rate in the liquid flow which in turn is a prerequisite to producing gas bubbles which are as fine as possible.
  • the trip edges may be disposed on either the cone- shaped deflecting cone element surface or on the inner surface of the funnel shaped casing.
  • the annular channels between the deflecting cone and the funnel shaped housing deflecting cone element and funnel have approximately a constant hydraulic diameter.
  • the annular channel may be segmented into at least four sections, with each of the sections having trip edges disposed therein.
  • the segments channel may be shaped to provide convergent, divergent, or a Venturi shaped exit path to provide the desired fluid flow characteristics.
  • Yet another aspect of the invention concerns a flotation cell provided with an inner cylindrical chamber and an outer annular space, in which the annular space serves as the flocculator or “mixing” chamber and the inner chamber serves as the tranquilizer or "calming” chamber.
  • Yet another aspect of the invention concerns a flotation cell provided with an inner cylindrical chamber and an outer annular space, in which the annular space serves as the flocculator or “mixing” chamber and the inner chamber serves as the tranquilizer or "calming” chamber.
  • the calming zone exhibits laminar vertical motion from top to bottom thereby facilitating the separation of the residual flocks.
  • liquid throughput forming the liquid propulsion jet is provided by a recycling centrifugal pump.
  • the majority of the flocks float in immediate vicinity of the outer cell wall and, therefore, may be removed by a skimmer without perturbing the liquid surface of the tranquilizer. Indeed, the accumulated flocks along the upper part of the tranquillizing zone are now left practically undisturbed by the skimmer and the laminar motion within it is maintained.
  • a simple cross shaped grid may be inserted in the lower portion of the inner cylindrical vessel. This may, therefore, be implemented far more easily in the cylindrical vessel than in the annular space, thereby permitting the dimensions of the cross sectional area of the inner cylinder to be relatively large at the expense of the area of the outer annular space.
  • Fig. 1 is a cross sectional view of a self-aspirating and radially discharging aeration device according to the invention.
  • Fig. 2 is a plot of the suction characteristics of the aeration device.
  • Fig. 3A is a cross-sectional view of an alternative embodiment of the aeration device .
  • Fig. 3B is a top end view of the aeration device of Fig. 3A.
  • Fig. 4 is a cross sectional view of a flotation cell in which the aeration device may be disposed to provide an induced air flotation for separating activated sludge.
  • Fig. 1 depicts a cross sectional elevational view of a self-aspirating and radially discharging funnel shaped aeration device 10 according to the invention.
  • the aeration device 10 consists of a deflecting section 12 shaped preferably as a cone which is arranged within a funnel-shaped housing 14.
  • the cone 12 and funnel 14 are spaced apart to thereby form an annular channel 16 between them.
  • the channel 16 therefore provides a Venturi-type confuser or diffuser depending upon the exact relative angular orientation of the cone 12 and funnel 14.
  • the spacing between the cone 12 and funnel 14 is maintained by spacers 18 disposed between them.
  • Above the top of the cone 12 is disposed a liquid propulsion jet nozzle 20 typically within the funnel.
  • the liquid jet nozzle 20 causes liquid exiting therefrom to impinge against the apex of the cone of the deflecting cone 12. Liquid is fanned out by the cone 12 becoming uniformly distributed over the cross sectional area of the annular channel 16. Also, within the annular channel, any air being sucked into the device through the top of the funnel 14 is ultimately mixed with liquid exiting from the jet nozzle 20 being discharged over the circumference of the deflecting cone 12. The resulting free jet of gas-liquid dispersion is therefor afterwards uniformly distributed over the floor of the flotation cell.
  • the inventive improvement of the funnel-shaped nozzle consists of inserting trip-edges 22 to either wall of the annular channel 16. Their purpose is to rip off the' laminar boundary layer from the deflecting cone 12 and from the casing 14, thus promoting the utmost turbulence in the annular channel 16.
  • the use of the trip-edges 22 improves the suction action of the funnel-shaped nozzle 10.
  • the trip edges 22 also promote the utmost shear rate in liquid flow which is a prerequisite to producing gas bubbles which are as fine as possible.
  • Fig. 2 is a chart depicting the dependency of the suction characteristics of the funnel-shaped nozzle 10 upon certain characteristics.
  • the diameter of the cone base, D b was 160 millimeters (mm) ; the diameter of the propulsion jet nozzle, d, was 20 mm; and the liquid head H' above the cone base was H' 800mm.
  • the plot illustrates that spreading of the liquid jet over the whole cross-section of the channel 16 such as encouraged by the trip edges 22 significantly improves the suction action.
  • segmentation 26 of the annular channel 16 represents an additional freely adjustable geometric parameter which results in a threefold advantage: a) In connection with a minimum slot width of the annular channel, it assures a high velocity of the free jet of the gas-liquid dispersion. b) The segments 26 may have different geometrical shapes or positions resulting in a confusor-, diffusor- or Venturi-shaped channels 16. Thus it is possible to optimally satisfy each requirement with regard to gas suction and shear rate. For high suction, a diffusor- shaped channel 16 with a slight enlargement of approximately 7° will be favorable. As a general rule, four to eight segments 26 will suffice. c) The segments make it possible to connect the funnel-shaped cone 12 solidly with the casing 14 thus allowing a centric, light, yet stiff connection between both parts .
  • the present inventive improvement also consists of reversing the functions of an inner chamber and an annular space of a floatation cell within which the jet nozzle may be deployed.
  • annular space serves as the actual flotation or flocculation space and the inner chamber represents the calming or tranquilizing zone.
  • the flotation cell 30 consists of an inner preferably cylindrical chamber 32 and outer annular chamber 34.
  • the annular space 34 serves as the actual flotation space in which mixing and aeration occurs whereby the inner space 32 serves as the calming or tranquilizing zone.
  • the aeration unit 10 is disposed beneath the bottom of the cell typically within the center of the outer annular space.
  • a feed inlet 36 and air inlet 38 are coupled to the aeration unit 10.
  • a feed outlet 40 provides an exit point for clarified liquid to exit from the tranquilizing zone 32.
  • a flotate or froth outlet 44 is provided at the top of the cell 30.
  • the cell is activated by connecting a centrifugal pump 42 to drive the aeration unit 10.
  • a motor 46 provides for driving a skimmer 46 to remove floate from the liquid surface of the cell.
  • the reversing of the functions of the inner chamber and annular space provides a variety of advantages .
  • a) The free jet of the funnel-shaped nozzle 10 distributes the gas-liquid-dispersion evenly across twice cross-sectional area. This results in an essential suppression of bubble coalescence.
  • Most of the flocks float in the immediate vicinity of the outer cell wall and therefore are removed by the skimmer 46 without perturbing the liquid surface.
  • c) The filter formed of accumulated flocks in the upper part of the calming zone is now left essentially undisturbed by the skimmer 48, the laminar motion within it also being safeguarded.
  • a cross- or ring-shaped grid 48 maybe inserted in the lower part (e.g., within the lower A to 2/3 of the height) of the inner cylindrical vessel 32.
  • This can be implemented far easier in a cylindrical chamber 32 than in an annular space as in the prior art.
  • This also permits the cross-sectional area of the cylinder 32 to be extended as far as possible at the expense of the annular space 34.
  • the new inventive conception of the functional reversion of both spaces allows a problem-free control of large cell diameters and includes an additional, fifth advantage, which can be exploited when flotation cells are to be piled up above one another.
  • multiple flotation cells 30 may be easily operated in parallel and be stacked up above one another, with 2 to 3 cells above one another representing an optimum utilization of the plant ground expense.
  • Another advantage of the new flotation cell according to the invention also becomes apparent, due to the favorable circumstance that the flotate (froth) rises in the annular space around the outer cell.
  • the flotate can therefore be easily be sucked out by a vacuum froth cleaner, rotating around the circumference of the cell.

Landscapes

  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Biotechnology (AREA)
  • Hydrology & Water Resources (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Physical Water Treatments (AREA)
  • Aeration Devices For Treatment Of Activated Polluted Sludge (AREA)

Abstract

L'invention a pour objet un dispositif pour la flottation induite avec insufflation d'air. Ce dispositif utilise une buse en forme d'entonnoir, à auto-aspiration et à déchargement radial, pour produire des bulles de gaz extrêmement fines. En outre, la buse peut être utilisée avec une cellule de flottation qui se compose d'uen chambre de mélange entourée d'un canal annulaire, pour permettre ainsi le déplacement vertical du liquide, depuis le sommet en direction du fond du canal annulaire.
EP98904132A 1997-01-23 1998-01-23 Appareil et procede de flottation induite avec insufflation d'air Withdrawn EP0954379A2 (fr)

Applications Claiming Priority (7)

Application Number Priority Date Filing Date Title
DE19702181 1997-01-23
DE19702181A DE19702181A1 (de) 1997-01-23 1997-01-23 Neue Vorrichtung zur Begasungsflotation
DE19706436 1997-02-19
DE19706436 1997-02-19
DE1997119539 DE19719539A1 (de) 1997-01-23 1997-05-09 Neue Vorrichtung zur Begasungsflotation
DE19719539 1997-05-09
PCT/EP1998/000375 WO1998032538A2 (fr) 1997-01-23 1998-01-23 Appareil et procede de flottation induite avec insufflation d'air

Publications (1)

Publication Number Publication Date
EP0954379A2 true EP0954379A2 (fr) 1999-11-10

Family

ID=27217054

Family Applications (1)

Application Number Title Priority Date Filing Date
EP98904132A Withdrawn EP0954379A2 (fr) 1997-01-23 1998-01-23 Appareil et procede de flottation induite avec insufflation d'air

Country Status (2)

Country Link
EP (1) EP0954379A2 (fr)
WO (1) WO1998032538A2 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT504827A1 (de) * 2007-01-23 2008-08-15 Siemens Ag Oesterreich Vorrichtung zum trennen von flüssigkeit und in der flüssigkeit fein verteilten, nicht-löslichen partikeln
CH703440B1 (it) * 2010-07-12 2014-06-30 Supsi Scuola Universitaria Professionale Della Svizzera Italiana Icimsi Sistema per il trattamento delle acque reflue.

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2634496C2 (de) * 1976-07-31 1985-10-17 Bayer Ag, 5090 Leverkusen Injektor zur Begasung einer Flüssigkeit
DE3008476A1 (de) * 1980-03-05 1981-09-17 Bayer Ag, 5090 Leverkusen Verfahren zur flotation und verwendung von trichterduesen zur flotation
DE4116916C2 (de) * 1991-05-24 1994-09-22 Escher Wyss Gmbh Flotationseinrichtung zur Störstoff- insbesondere Druckfarbenentfernung aus Altpapiersuspensionen

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9832538A3 *

Also Published As

Publication number Publication date
WO1998032538A2 (fr) 1998-07-30
WO1998032538A3 (fr) 1998-12-10

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