Classifications

• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F3/00—Biological treatment of water, waste water, or sewage
  • C02F3/02—Aerobic processes
  • C02F3/12—Activated sludge processes
  • C02F3/1278—Provisions for mixing or aeration of the mixed liquor
  • C02F3/1284—Mixing devices
• • 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
  • B01F25/3122—Injector mixers in conduits or tubes through which the main component flows with Venturi elements; Details thereof the material flowing at a supersonic velocity thereby creating shock waves
• • 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
  • B01F25/314—Injector mixers in conduits or tubes through which the main component flows wherein additional components are introduced at the circumference of the conduit
  • B01F25/3141—Injector mixers in conduits or tubes through which the main component flows wherein additional components are introduced at the circumference of the conduit with additional mixing means other than injector mixers
• • 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
  • B01F25/40—Static mixers
  • B01F25/45—Mixers in which the materials to be mixed are pressed together through orifices or interstitial spaces, e.g. between beads
• • 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
  • B01F25/40—Static mixers
  • B01F25/45—Mixers in which the materials to be mixed are pressed together through orifices or interstitial spaces, e.g. between beads
  • B01F25/452—Mixers in which the materials to be mixed are pressed together through orifices or interstitial spaces, e.g. between beads characterised by elements provided with orifices or interstitial spaces
  • B01F25/4521—Mixers in which the materials to be mixed are pressed together through orifices or interstitial spaces, e.g. between beads characterised by elements provided with orifices or interstitial spaces the components being pressed through orifices in elements, e.g. flat plates or cylinders, which obstruct the whole diameter of the tube
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
  • B05B7/0018—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas with devices for making foam
  • B05B7/0025—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas with devices for making foam with a compressed gas supply
  • B05B7/0031—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas with devices for making foam with a compressed gas supply with disturbing means promoting mixing, e.g. balls, crowns
• • 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
  • C02F1/20—Treatment of water, waste water, or sewage by degassing, i.e. liberation of dissolved gases
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F3/00—Biological treatment of water, waste water, or sewage
  • C02F3/02—Aerobic processes
  • C02F3/12—Activated sludge processes
  • C02F3/1278—Provisions for mixing or aeration of the mixed liquor
  • C02F3/1294—"Venturi" aeration means
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W10/00—Technologies for wastewater treatment
  • Y02W10/10—Biological treatment of water, waste water, or sewage

Definitions

• This invention relates to a device for mixing a liquid with a gas to produce a fine foam.
• Venturi tubes where for instance air is sucked into a pipe in the form of bubbles containing liquid, or liquid is sprayed into a Venturi-shaped tube containing gas. Velocities are kept above laminar flow levels to ensure turbulent flow and hence good mixing. Other mixing devices use blades and other mechanical devices with moving parts to mix the two phases.
• aerator used to aerate slurry on farms to accelerate the digestion of noxious bacteria and reduce the smell.
• the liquid to be aerated is pumped through a nozzle to increase its velocity and hence lower its pressure. After passing through the nozzle it enters a 'T' piece with a connection to an air supply at right angles to the flow of liquid. Air is dragged into the liquid flow in the manner of an ejector. The mixed flow is then passed through a long barrel the size of which ensures that the flow is turbulent r and hence rigorous mixing takes place.
• a Venturi tube is used to drag oxygen into a flow of water. hen this mixture expands in the expansion section of .the Venturi tube vigorous mixing takes place because of the positive pressure gradient.
• Yet another aerating device works by pumping liquid to a mixing head which contains a large number of stainless steel pins on both a stator and rotor.
• the rotor mixes the ingredients ⁇ and at the same time compressed air is introduced into the head to aerate the mix to a foam.
• mixing is achieved by mechanical means.
• a device for mixing a liquid with a gas to produce a fine foam comprising: means for feeding a liquid under pressure along a passage, gas inlet means for admitting gas into the passage to mix with the liquid, and a sized restrictor through which the mixture is forced to pass, causing the mixture to reach substantially a supersonic velocity downstream of the restrictor, whereby the shock waves resulting from the subsequent decelaration of the mixture cause the mixture to be further broken up to produce a fine foam.
• the passage may be a tube containing the liquid with one or more openings, in which gas is allowed to pass and mix with the liquid to form bubbles.
• the resultant mixture is then passed through a carefully sized convergent-divergent nozzle which ensures that the mixed flow is first forced to go supersonic and then forced to pass through shock waves as it decelerates back to subsonic.
• Pre ixing of the liquid gas mixture can be enhanced by passing the mixture through an orifice or other mixing device upstream of the supersonic nozzle.
• only one orifice is used. At the entrance to the orifice vigorous mixing ensures that a relatively fine mix is exhausted at the orifice exit. Choking of the mixture takes place at the exit (sonic velocity) and as the mixture expands downstream of the exit it goes supersonic for a short distance and finally passes through shock waves as it decelerates to a subsonic condition .
• a Venturi tube is used to suck gas into the liquid stream. This mixture is then passed through a supersonic nozzle.
• the supersonic nozzle is a convergent-divergent or de-Laval nozzle.
• large Mach numbers ratio of velocity to sonic velocity
• the gas will have to be separated from the liquid mixture at a later stage.
• the device in accordance with the invention uses the little known phenomena of choking in gas-liquid mixtures. This phenomena is described below.
• This phenomena of supersonic flow and its associated shock waves is used in the present invention to break gas-liquid mixtures into fine foams.
• Figure 1 is a sectional view of a device in accordance with one embodiment of the invention.
• Figure 2 is a device similar to Figure 1 but incorporating a Venturi gas inlet
• Figure 3 is a further device but incorporating a de-Laval nozzle. Detailed description
• liquid 1 is forced along a tube 2 in which openings 4 are located from which gas 3 is injected into the liquid stream.
• the resultant bubbly mixture is passed through a pre-mixing orifice 6, which breaks up the bubbles and mixes the two constituents further and increases the volumetric ratio of gas to liquid because of the associated pressure reduction and expansion of the gas.
• the resultant mixture which should preferably be near to 50% gas in volumetric terms, is then passed through a sized restrictor in the form of a second orifice 7 where the mixture reaches sonic conditions. As the mixture leaves orifice 7 and expands into the increased space, it goes supersonic and then decelerates to subsonic through shock waves, resulting in a foamy mixture 9.
• the number of orifices used can vary depending on factors such as the gas to liquid ratios, the type of gas and liquid, and the flow rates.
• liquid 1 is forced along a tube 2 and into a Venturi 11 in which openings 4 are located from which gas 3 is injected into the liquid stream.
• the resultant bubbly mixture is further broken up in the expansion section of the Venturi, resulting in an even finer mixture which should preferably be near to 50% gas in volumetric terms.
• This is then passed through an orifice 7 where the mixture reaches sonic conditions. As the mixture leaves orifice 7 and expands into the increased space it again decelerates and passes through shock waves, resulting in a foamy mixture 9.
• liquid 1 is forced along a tube 2 to which openings 4 are located from which gas 3 is injected into ' the liquid stream.
• the resultant bubbly mixture is passed through a pre-mixing orifice 6 which again breaks up the bubbles, and mixes the two constituents further, and increases the volumetric ratio of gas to liquid.
• the resultant mixture again near to 50% gas in volumetric terms, is then passed through a de Laval convergent divergent nozzle 12 where the mixture reaches sonic conditions at the throat. As the mixture leaves nozzle 12 and expands into the increased space it again goes supersonic and then declerates to subsonic through shock waves, resulting in a foamy mixture 9.

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• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Hydrology & Water Resources (AREA)
• Engineering & Computer Science (AREA)
• Environmental & Geological Engineering (AREA)
• Water Supply & Treatment (AREA)
• Organic Chemistry (AREA)
• Dispersion Chemistry (AREA)
• Biodiversity & Conservation Biology (AREA)
• Microbiology (AREA)

Applications Claiming Priority (10)

Publications (1)

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• 1989
  • 1989-11-22 EP EP89913017A patent/EP0445169A1/de not_active Withdrawn
  • 1989-11-22 WO PCT/GB1989/001395 patent/WO1990005583A1/en not_active Application Discontinuation
  • 1989-11-22 AU AU46250/89A patent/AU4625089A/en not_active Abandoned

Non-Patent Citations (1)

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