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
  • B03D1/1431—Dissolved air flotation machines
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
  • B01F23/40—Mixing liquids with liquids; Emulsifying
  • B01F23/45—Mixing liquids with liquids; Emulsifying using flow mixing
  • B01F23/454—Mixing liquids with liquids; Emulsifying using flow mixing by injecting a mixture of liquid and gas
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
  • B01F25/20—Jet mixers, i.e. mixers using high-speed fluid streams
  • B01F25/21—Jet mixers, i.e. mixers using high-speed fluid streams with submerged injectors, e.g. nozzles, for injecting high-pressure jets into a large volume or into mixing chambers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
  • B01F25/30—Injector mixers
  • B01F25/31—Injector mixers in conduits or tubes through which the main component flows
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
  • B01F25/30—Injector mixers
  • B01F25/31—Injector mixers in conduits or tubes through which the main component flows
  • B01F25/312—Injector mixers in conduits or tubes through which the main component flows with Venturi elements; Details thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
  • B01F25/30—Injector mixers
  • B01F25/31—Injector mixers in conduits or tubes through which the main component flows
  • B01F25/312—Injector mixers in conduits or tubes through which the main component flows with Venturi elements; Details thereof
  • B01F25/3124—Injector mixers in conduits or tubes through which the main component flows with Venturi elements; Details thereof characterised by the place of introduction of the main flow
  • B01F25/31242—Injector mixers in conduits or tubes through which the main component flows with Venturi elements; Details thereof characterised by the place of introduction of the main flow the main flow being injected in the central area of the venturi, creating an aspiration in the circumferential part of the conduit
• • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
  • B01F23/20—Mixing gases with liquids
  • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F33/00—Other mixers; Mixing plants; Combinations of mixers
  • B01F33/80—Mixing plants; Combinations of mixers
  • B01F33/81—Combinations of similar mixers, e.g. with rotary stirring devices in two or more receptacles
• • 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

• the present invention relates to a method of generating gas bubbles in a liquid, in which method gas is taken into a dispersion space situated inside a dispersion nozzle device, and at least a portion of the dispersion operation is carried out in the dispersion space and in a discharge channel exiting thereof using liquid-gas-liquid dispersion. Furthermore, the invention concerns an apparatus for the implementation of the method.
• Such applications include, e.g., aeration or oxygenation of water or aqueous solutions/suspensions, and the froth flotation and/or flotation of minerals, solids, sludges and similar components from liquids containing these particles.
• the small bubbles of air required in the flotation purification of liquids are generally produced using a so-called dissolved-air method in which a solution saturated with air or gas in a pressure vessel with the help of elevated pressure is subsequently taken along a pipe to the space containing the liquid to be purified.
• the small bubbles (with a size of ⁇ 100 ⁇ m) thus gener ⁇ ated float up the solids, sediment and similar particles.
• the flotated material is accumulated immediately below the liquid surface forming a relatively consistent super ⁇ natant froth which is removed at timed intervals by means of a scraper or similar means over the edge of the flota ⁇ tion cell.
• Dissolved nutrients or other undesirable ele ⁇ ments contained in the liquid can be removed by first coagulating them with suitable chemicals and then remov ⁇ ing by flotation the formed sediment, to which also solids contained in the liquid generally readily attach.
• the microbubbles required for flotation are still today conventionally generated by the dissolved-air method in a pressure vessel, wherefrom the air/gas-saturated liquid mixture is taken via piping to the purification tank.
• the pressure vessels require annual inspections and mainte ⁇ nance.
• the bubble size required in mineral froth flotation is larger than in flotation, typically being ⁇ IOOO ⁇ m.
• a disadvantage herein is a high specific energy consumption and the need of repetitive maintenance and servicing of the mechanical rotors.
• the adjustment of the air bubble size in impeller aeration is problematic.
• Prior-art methods of controlling the air bubble size include change of air feed rate and/or bubble size control by means of various chemicals. Both control methods of bubble size are complicated and frequently cause operating deviations and disturbances in the process that rather deteriorate than improve the desired outcome.
• Apparatuses are used in the art in which the liquid and the gas are mixed in a separate dispersion vessel prior to taking them to the treatment tank or similar point of use.
• Conventional dispersion methods are suited for generating either microbubbles for flotation, or more typically, only larger bubbles for froth flotation, but not for making both bubble sizes controlledly by means of the same apparatus.
• prior-art arrangements are based on controlling the bubble size through air flow rate adjustment.
• the air flow rate must be reduced, whereby also the total volume of air entrapped in the bubbles may possibly fall below the critical volume required for the process.
• a contrary problem may occur if the process demands a high volume of air. Then, increasing the air flow rate may bring the bubble size excessively large for the process. In other words, the bubble size in conventional arrangements is very strongly dependent on the air flow rate.
• the size of generated gas bubbles is controlled through altering the length of the dispersion space with the help of an adjus ⁇ ter means, or alternatively, through altering simul ⁇ taneously the length of the dispersion space and the size of the gas infeed opening to the dispersion space with the help of the adjuster means.
• the dispersion space is formed into a separate space, and bubble generation and size of bubbles generated therein can be adjusted flexibly according to the invention.
• the size of the gas infeed opening is either kept constant while the length of the dispersion space is altered, or alternatively, the size of the gas infeed opening is adapted variable in a predetermined fashion.
• the bubble size can be adjusted in a manner that causes less variation in the air flow rate than conventional arrangements.
• the method according to the invention is superior to conventional dispersion arrangements in that the present method makes it possible to generate both small bubbles (microbubbles) for flota- tion and also larger bubbles for froth flotation in a controlled manner.
• the bubble size can be controlled accurately as required and also the fine-tuning of the bubble size is possible.
• Particularly in mineral froth flotation such a bubble size fine-tuning facility is an excellent benefit as it may be employed to reduce production losses caused by errors in ore grinding.
• the bubble size can be adjusted mechanically for a larger or smaller size in order to improve the flotation efficiency.
• the aeration apparatus according to the invention is simple and easy to operate and maintain.
• the kinetic energy of the liquid is effectively utilized by implementing the liquid-gas-liquid dispersion inside the apparatus and the gas-liquid dispersion outside the apparatus in the liquid to be dispersed.
• a gas-liquid mixture with abundant bubbles is achieved at a low cost of bubble generation.
• the method according to the invention is suited for the dispersion of all kinds of liquids and gases as well as their numerous applications.
• the dispersion space When the dispersion space is implemented as a separate space, changes can be controlled and the size of gas bubbles adjusted.
• the fine-tuning of the size of gas bubbles generated in the dispersion space and the discharge channel can be complemented with bubble size control based on varying the flow and/or pressure ratios of the infeed liquid and/or gas, which are conventionally known coarse adjustment methods of bubble size.
• the apparatus suited to implement the method ⁇ according to the invention which apparatus is installable in an operating space such as an aeration tank, a dispersed-air flotation cell or a dissolved-air froth flotation cell, has an extremely simple construction and comprises no wearing mechanisms.
• the manufacturing and maintenance costs of the apparatus are low.
• the replacement of the apparatus or a part thereof with a new one takes only a few minutes, whereby such a replacement operation cannot generally cause any major disturbance to the process supported by the apparatus.
• the disturbance states related to the maintenance operations of the apparatus according to the invention are short-term and rare.
• the process must generally be run down for service or maintenance operations when a conventional apparatus is used, whereby in addition to maintenance costs, economical losses will occur from process run-downs, restarts and production losses.
• the specific energy consumption of the apparatus accord- ing to the invention is extremely modest.
• the energy consumption of the apparatus according to the invention is less than 10 %.
• the operating costs of the dispersion apparatus according to the invention remain appreciably smaller than those of the prior-art.
• Microbubbles employed in the conventional flotation tech ⁇ niques of water purification can be generated by means of the method according to the invention and utilizing the apparatus implementing the method without the use of a pressure vessel for gas saturation. Additionally, the same apparatus can be used for generating larger gas bubbles suited for separation of sludge and solids through froth flotation, whereby the sludge, solids or similar particulates are carried by the bubbles up to the surface of the sludge-containing liquid and further away from the liquid being purified along with the overflow of the formed froth, over the edge of the cell.
• froth flotation operation is appreciably faster (needing shorter time for purification) than conventional flota ⁇ tion
• the purification equipment requires an essentially smaller footprint in the water treatment premises.
• froth flotation applications using the embodiment accord ⁇ ing to the present invention require smaller investment costs in building and equipment with regard to those of conventional flotation applications.
• the oper- ating costs remain herein smaller than in conventional flotation.
• Figure 1 is a longitudinally sectioned side view of an embodiment of the dispersion nozzle device according to the invention.
• Figure 2 is a longitudinally sectioned side view of another embodiment of the dispersion nozzle device according to the invention.
• Figure 3 is a longitudinally sectioned side view of a third embodiment of the dispersion nozzle device according to the invention.
• Figure 4 is a schematic diagram illustrating an aeration application of the method suited for use in the oxidiza ⁇ tion of, e.g., water taken from natural supplies;
• Figure 5 is a schematic diagram illustrating another aeration application of the method suited for aeration, and conventional flotation or froth flotation in, e.g., tanks;
• Figure 6 is a froth flotation/conventional flotation application of the apparatus according to the invention in a partially sectioned side view;
• Figure 7 is a top view of the apparatus shown in Fig. 6;
• Figure 8 is a partially diagrammatic side view of another further application of a froth flotation/conventional flotation apparatus according to the invention.
• the dispersion nozzle device 1 com ⁇ prises a body part 6 incorporating a discharge channel 3, an end part 4 incorporating a liquid infeed connection 8 and a liquid channel 9, and an intermediate part 10 adapted between the body part and the end part. Between the intermediate part, the end part and the discharge channel is arranged a dispersion space 2.
• the end part 4 is axially adjustably connected to the intermediate part 10 by means of threads, for example, thus providing stepless adjustment of the length A of the dispersion space 2 by moving the end part with respect to the inter ⁇ mediate part.
• the intermediate part 10 is adjustably connected to the body part 6 thus permitting the adjustment of the length of the dispersion space 2 also by moving the intermediate part relative to the body part.
• a gas infeed connection 7 is adapted to the body part.
• the wall of the intermediate part is provided at the gas infeed connection with an opening 12 through which the gas can enter a gas space 11 between the intermediate part and the end part, whereby the opening forms a round, slit-like gas entrance orifice into the dispersion space.
• the opposing walls of the intermediate part and the end part are arranged tapering in this space. The walls are extended tapering almost parallel, thus giving an effective control means for the gas flow rate through the adjustment of the axial distance between the intermediate part and the body part.
• the gas connec ⁇ tion line 7 is provided with a regulator for the adjust ⁇ ment of the gas flow rate and pressure.
• the liquid connection line 8 may be provided with a regulator for the adjustment of the liquid pressure and flow rate.
• the discharge channel 3 is detachably connected to the body part 6 thus facilitating easy replacement. Similar- ly, the end part is adapted detachable from the inter ⁇ mediate part and the intermediate part detachable from the body part. Hence, a certain application may readily be provided with a size- and shape-optimized liquid channel, discharge channel and other parts. An extra benefit herein is the easy replacement of worn parts.
• the disper ⁇ sion liquid is taken via the liquid connection 8 to the liquid channel 9 of the end part of the dispersion nozzle device and therefrom further to the dispersion space 2, into which the gas is taken via the gas infeed connection 7 and the gas space, that is, the gas infeed opening 12.
• the gas infeed opening 1? is adapted to surround the liquid channel in an annular fashion. In the dispersion space the pressurized liquid jet meets the gas entering from about it, whereby liquid-gas-liquid dispersion occurs.
• the dispersed liquid-gas mixture discharges further via the discharge channel, undergoing further dispersion in the channel, into the liquid to be gas- aerated or into a liquid containing particulates to be subjected to purification, flotation or other similar treatment thereby causing the dispersion of the liquid with the injected gas-liquid dispersion.
• the length and volume of the dis ⁇ persion space are adapted adjustable through an axial movement of the intermediate and end part combination relative to the body part, or alternatively, of the intermediate part relative to the end part, while the size of the gas space, that is, the gas infeed opening can be simultaneously adjusted if required by an axial movement of the end part relative to the intermediate part.
• the longitudinal adjustment of the dispersion space can be implemented either with the gas infeed openings 12 staying constant during the adjustment, or alternatively, making the openings variable in a predetermined fashion during the adjustment of the dispersion space.
• the embodiment of the dispersion nozzle device shown therein comprises a body part 6, an end part 4 detachably adapted to one end thereof, and a tip part 5 also detachably adapted to the other end of the body part.
• a gas infeed connection 7 To the body part is attached a gas infeed connection 7.
• the end part is provided with a liquid infeed connection 8, and axially extending through the end part is made a liquid channel 9.
• a separate dispersion space 2 In the inside on the device, between the body part, the end part and the tip part is arranged a separate dispersion space 2.
• the gas connection 7 is located to the side of the body part so as to exit into a gas space 11 situated between the end part and the body part.
• the body part is provided on the outer wall of the gas space with an appropriately upward slightly tapering, conical inner-diameter-reducing section.
• the outer diameter of the constant-diameter tip section of the end part that extends to the gas space is larger than the smallest inner diameter of the conical reducer section.
• the length of the dispersion space 2 and the bubble size can be adjusted by means of an axial movement of the end part and/or the tip part relative to the body part.
• the gap between the gas space and the dispersion space can be adjusted by moving the tip part 5 or the end part 4 or both simultaneously relative to the body part.
• a. simple embodiment of the disper ⁇ sion nozzle device is shown longitudinally sectioned.
• the body part 1 also forms the tip part. Then, both the volume of the gas space 11 and the length and volume of the dispersion space 2 are changed by the same adjustment when the end part is moved relative to the body part, whereby this type of bubble size adjustment facility is sufficient for some applications.
• FIG. 4 an aeration application according to the invention is shown.
• the liquid is fed to the dispersion nozzle device 1 by means of a pipe 13 forming a circle, eclipse or other desired shape.
• a required number of dispersion nozzle devices 1 are con ⁇ nected to the pipe.
• the gas is fed to the dispersion nozzle device via a hose 14.
• the disper ⁇ sion nozzle devices are mounted so that dispersion occurs outward and downward slanting from the perimeter of the shape-folded joint manifold, whereby the gas-liquid mixture is discharged to a maximally large area and simultaneously the retention time of the dispersion mixture in the liquid to be dispersed is long and the gas treatment can be extended maximally close to the bottom yet leaving a sufficient upward distance so that the bottom sludge layer will not be evoked up with the turbu- lence.
• the adjustment of the dispersion nozzle devices is carried out locally according to the intended use.
• FIG. 5 another aeration application accord ⁇ ing to the invention is shown in which the pipe 15 feed- ing the liquid and the hose 16 feeding the gas are con ⁇ figured to a shape complying with the treatment tank 17 or similar point of application, and a required number of dispersion nozzle devices 1 according to the invention are mounted on said liquid infeed pipe.
• optimal alignment of the discharge openings of the dispersion nozzle devices is capable of increasing the retention of the dispersion mixture in the liquid and thus aiding the gas treatment of the liquid.
• individual alignment of the discharge openings of the device sets or single devices permits aiming the disper ⁇ sion mixture to critical points in the liquid space as required by the treatment process.
• the adjustment of the dispersion nozzle devices is carried out locally accord ⁇ ing to the intended use.
• the apparatus is placed on the bottom of a froth flotation or conven ⁇ tional flotation cell 18 having a conical bottom section.
• the dispersion nozzle devices 1 are placed at a distance from each other along the perimeter of the conical section with one of the devices located on the bottom of the conical section.
• the dispersion nozzle devices 1 are located in rows on the bottom of a tank 19 and its flanked walls.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Biotechnology (AREA)
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Priority Applications (1)

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Cited By (5)

Families Citing this family (1)

Citations (4)

• 1994
  • 1994-04-12 FI FI941674A patent/FI941674A/sv not_active Application Discontinuation
• 1995
  • 1995-04-12 WO PCT/FI1995/000209 patent/WO1995027557A1/en active Application Filing
  • 1995-04-12 AU AU22595/95A patent/AU2259595A/en not_active Abandoned

Patent Citations (4)

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