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WO2008013349A1 - Diffuseurs de silice et d'alumine créant des microbulles, leur procédé de fabrication, et procédé de traitement des eaux usées - Google Patents

Diffuseurs de silice et d'alumine créant des microbulles, leur procédé de fabrication, et procédé de traitement des eaux usées Download PDF

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Publication number
WO2008013349A1
WO2008013349A1 PCT/KR2007/000261 KR2007000261W WO2008013349A1 WO 2008013349 A1 WO2008013349 A1 WO 2008013349A1 KR 2007000261 W KR2007000261 W KR 2007000261W WO 2008013349 A1 WO2008013349 A1 WO 2008013349A1
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WO
WIPO (PCT)
Prior art keywords
ceramic
diffuser
silica
wet powder
range
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.)
Ceased
Application number
PCT/KR2007/000261
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English (en)
Inventor
Yong Su Choi
Sanghyup Lee
Seok Won Hong
Chanhyuk Park
Seung Ho Kim
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.)
KOREA CERAMIC CO Ltd
Korea Institute of Science and Technology KIST
Original Assignee
KOREA CERAMIC CO Ltd
Korea Institute of Science and Technology KIST
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 KOREA CERAMIC CO Ltd, Korea Institute of Science and Technology KIST filed Critical KOREA CERAMIC CO Ltd
Priority to CN200780025139XA priority Critical patent/CN101484393B/zh
Priority to HK09111628.8A priority patent/HK1131962B/xx
Publication of WO2008013349A1 publication Critical patent/WO2008013349A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • 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
    • B01F23/231—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids by bubbling
    • B01F23/23105—Arrangement or manipulation of the gas bubbling devices
    • B01F23/2312—Diffusers
    • B01F23/23123—Diffusers consisting of rigid porous or perforated material
    • 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
    • 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
    • B01F23/231—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids by bubbling
    • B01F23/23105—Arrangement or manipulation of the gas bubbling devices
    • B01F23/2312—Diffusers
    • B01F23/23126—Diffusers characterised by the shape of the diffuser element
    • B01F23/231262—Diffusers characterised by the shape of the diffuser element having disc shape
    • 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
    • B01F23/231—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids by bubbling
    • B01F23/23105—Arrangement or manipulation of the gas bubbling devices
    • B01F23/2312—Diffusers
    • B01F23/23126—Diffusers characterised by the shape of the diffuser element
    • B01F23/231265—Diffusers characterised by the shape of the diffuser element being tubes, tubular elements, cylindrical elements or set of tubes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B1/00—Producing shaped prefabricated articles from the material
    • B28B1/08—Producing shaped prefabricated articles from the material by vibrating or jolting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B3/00—Producing shaped articles from the material by using presses; Presses specially adapted therefor
    • B28B3/02—Producing shaped articles from the material by using presses; Presses specially adapted therefor wherein a ram exerts pressure on the material in a moulding space; Ram heads of special form
    • B28B3/022—Producing shaped articles from the material by using presses; Presses specially adapted therefor wherein a ram exerts pressure on the material in a moulding space; Ram heads of special form combined with vibrating or jolting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B3/00—Producing shaped articles from the material by using presses; Presses specially adapted therefor
    • B28B3/20—Producing shaped articles from the material by using presses; Presses specially adapted therefor wherein the material is extruded
    • B28B3/26—Extrusion dies
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B7/00—Moulds; Cores; Mandrels
    • B28B7/34—Moulds, cores, or mandrels of special material, e.g. destructible materials
    • B28B7/342—Moulds, cores, or mandrels of special material, e.g. destructible materials which are at least partially destroyed, e.g. broken, molten, before demoulding; Moulding surfaces or spaces shaped by, or in, the ground, or sand or soil, whether bound or not; Cores consisting at least mainly of sand or soil, whether bound or not
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/10—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on aluminium oxide
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/14—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on silica
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/60—Aspects relating to the preparation, properties or mechanical treatment of green bodies or pre-forms
    • C04B2235/602—Making the green bodies or pre-forms by moulding
    • C04B2235/6021—Extrusion moulding
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
    • C04B2235/94—Products characterised by their shape

Definitions

  • the present invention relates to silica or alumina based ceramic diffusers that generate microbubbles for solid-liquid separation of pollutants in wastewater as well as methods for manufacturing said diffusers.
  • the present invention also relates to methods for wastewater treatment based on air-flotation using said diffusers.
  • Membrane filters filter and separate pollutants, organic matter and microbial particles such as bacteria in wastewater through their micropores. Widely used in the field of water treatment, membrane filters are mostly involved in municipal and drinking water treatment. They, however, frequently suffer from fouling caused by highly concentrated pollutants.
  • Water treatment based on air-flotation is most frequently used in the treatment of organic wastewater or sludge from aeration tank where biological oxygen demands(BODs) and suspended solid (SS) levels are typically high.
  • BODs biological oxygen demands
  • SS suspended solid
  • DAF dissolved air- flotation
  • Dissolved air-flotation is described in such prior arts as Korean Patent Publications No. 10-0155482 and No. 10-0351111. Still, this method has its own problems. It requires high capacity air compressors since supplying dissolved air necessitates high pressures of 4-5 atmospheres. It also require wide areas for installation and suffers from high running costs.
  • microbubbles have come into more frequent use in order to overcome the shortcomings mentioned above.
  • water to be treated is provided with artificially produced microbubbles in place of air bubbles from pressurized, supersaturated dissolved air.
  • microbubbles cause solid pollutants to rise to the top, eventually leading to the removal of the separated solid by, for example, a skimmer.
  • EF electro-flotation
  • the present invention aims to provide silica or alumina-based ceramic diffusers consisting of dense and uniform ceramic particles, the ideal particle distribution of which supports a steady generation of fine air bubbles.
  • the present invention also aims to provide methods for producing said diffusers.
  • the present invention provides a ceramic diffuser based on silica or alumina capable of generating microbubbles, for separating pollutants through flotation, wherein said diffuser is a calcined silica or alumina powder compact.
  • the inventive diffuser is characterized in that it has such particle size distribution that as one proceeds from the surface to the inside, particle sizes increase.
  • the pore sizes of the inventive diffuser are in the range of 0.001 ⁇ m-0.05 ⁇ m.
  • said diffuser is characterized in that it is either disc-shaped or pipe-shaped. Said pipe- shaped diffuser characteristically has a length ranging from 16 to 100 cm.
  • the inventive diffuser is characterized in that the size of microbubbles formed by said diffuser ranges from 1 to 100 ⁇ m, preferably 40 to 60 ⁇ m.
  • the present invention also provides a method for producing pipe-shaped ceramic diffusers based on silica or alumina capable of generating microbubbles comprising: (a) preparing a wet powder of silica or alumina; (b) feeding a extruder with the wet powder; (c) placing a vibrator at the nozzle of said extruder; (d) applying vibration under pressure to the wet powder in the extruder using the vibrator to form an extrusion molded product and (e) removing the extrusion molded product out of said nozzle and calcining said extrusion molded product in an oxidative atmosphere furnace.
  • the present invention is characterized in that the pressure applied is in the range of 300 to 600 tons.
  • the present invention also provides a method for producing disc-shaped ceramic diffusers based on silica or alumina capable of generating microbubbles comprising: (a) preparing a wet powder of silica or alumina; (b) feeding concave metallic mold 1 with the wet powder; (c) inserting a polyvinyl chloride film to the fed wet powder after the feeding; (d) feeding said concave metallic mold 1 with the wet powder on top of the inserted film;
  • the film has a thickness in the range of 0.25-0.5 mm.
  • said supersonic vibrator(s) 11 is/are placed either (a) inside said convex metallic mold 2 or (b) inside the support 22 to which said concave metallic mold 1 is fixed or (c) one each at both said places of(a) and (b).
  • vibration separator(s) 12 is/are placed either (a) at the vicinity of said supersonic vibrator 11 and said support 22 wherein said supersonic vibrator 11 is fixed thereto or (b) at the vicinity of press 23 and supersonic vibrator 11 inside said convex metallic mold 2 or (c) one each at both said places of (a) and (b) so as to block the propagation of the vibration toward said support 22 and press 23.
  • the removal of the molded product comprises a movement by piston 21 connected to an actuator capable of vertically moving up and down.
  • the driving pressure of said concave metallic mold 2 is in the range of 100 to 200 tons and said pressure applied with vibration is in the range of 10 to 30 tons.
  • the temperature of said oxidative atmosphere furnace is in the range of 900 ° C-l,300 ° C .
  • said wet powder is a mixture of binder solution with either a silica or alumina powder which said ceramic diffuser is based thereon.
  • said vibration is applied at a frequency range of 20,000 to 25,000 hertzes.
  • a method for treating wastewater by air-flotation wherein microbubbles generating from said ceramic diffuser float pollutants to form concentrated sludge layer on the upper part and a layer of treated water on the lower part of the treatment cell.
  • an aeration through said ceramic diffuser is achieved under a pressure of 0.8-1.2 atmospheres.
  • the ceramic diffuser of the present invention has a particle size distribution in which the particle sizes of silica or alumina powder increase in the direction toward its center since during the manufacturing of said diffuser, pressure is applied along with shaking.
  • a small air pressure around 1 atm is capable of providing a uniform and steady stream of microbubbles for securing a rapid flotation of pollutants in wastewater.
  • the air-flotation method of the present invention does not suffer from scale formation as is the case with electro-flotation with electrode plates. This allows the inventive ceramic diffuser to be used conveniently and semi-permanent Iy without maintenance problems, adding to its economic advantage.
  • the enhanced productivity arising from the use of the inventive extrusion molding process for producing said ceramic diffusers supports additional cost reduction.
  • Figure Ia is a photograph showing a finished product of the disc-shaped ceramic diffuser of the present invention.
  • Figure Ib is a photograph showing a finished product of the pipe-shaped ceramic diffusers of the present invention.
  • Figure Ic is a cross section of the inventive disc-shaped ceramic diffuser.
  • Figure 2a is a schematic diagram showing bubbles generated from the disc-shaped ceramic diffuser of the present invention.
  • Figure 2b is a photograph showing bubbles generated from the disc-shaped ceramic diffuser of the present invention.
  • Figure 2c a schematic diagram showing bubbles generated from the pipe-shaped ceramic diffuser of the present invention.
  • Figure 2d is a photograph showing bubbles generated from the pipe-shaped ceramic diffuser of the present invention.
  • Figure 3 is a vertical cross section illustrating the operation of the apparatus for manufacturing the inventive disc-shaped ceramic diffuser.
  • Figure 4a is a photograph showing the microbubbIe-induced flotation results in example 1 of the present invention immediately after the introduction of sludge.
  • Figure 4b is a photograph showing the microbubble- induced flotation results in example 1 of the present invention 5 minutes after the introduction of sludge.
  • Figure 4c is a photograph showing the microbubble-induced flotation results in example 1 of the present invention 10 minutes after the introduction of sludge.
  • Figure 4d is a photograph showing the top surface after solid/liquid separation of sludge by air- flotation using microbubbles.
  • Figure 5 is a top view showing the configuration of electrode plates in comparative example 1 of the present invention.
  • Figure 6 is a photograph comparing electrode plates with scale deposit (left) in comparative example 1 with the same electrode plates before scale deposition (right).
  • the inventive ceramic diffuser based on silica or alumina generates microbubbles so as to float pollutants to the top and separate them.
  • the pore size of said silica or alumina-based ceramic diffuser can be chosen from a range of 0.001 ⁇ m to 0.05 ⁇ m depending on the size of the bubble to be generated.
  • the size of the microbubbles generated from said diffuser is in the range of 1 to 100 m, and preferably in the range of 40 to 60 ⁇ m. This is because larger bubbles are incapable of effectively floating pollutants, leading to a sharp drop in purification capacity.
  • the inventive ceramic diffuser based on silica or alumina is preferably a disc or pipe.
  • said pipe-shaped diffusers have lengths in the range of 16-100 centimeters, since the pressure of air moving inside the ceramic diffuser becomes less uniform when the length of the inventive diffusers is out of the stipulated range.
  • Figure Ia is a photograph showing a finished product of the disc-shaped ceramic diffuser of the present invention.
  • Figure Ib is a photograph showing a finished product of the pipe-shaped ceramic diffuser of the present invention.
  • the diameter of the inventive disc-shaped ceramic diffuser was 15.8 cm.
  • the air inlet (the central circle in Figure Ia) for pressurizing the internal channel of said diffuser had a diameter of 1 inch and a thickness of 0.8 cm.
  • the pipe-shaped ceramic diffuser had an outer diameter of 4.0 cm, and a length of 18 cm.
  • Figure Ic shows a cross section of a disc ⁇ shaped ceramic diffuser according to an embodiment of the present invention.
  • Figure 2a is a schematic diagram showing the actual generation of bubbles by a disc-shaped ceramic diffuser according to an embodiment of the present invention when applied to a reactor.
  • Figure 2b is the corresponding photograph.
  • the structure in the center connected to 4 disc-shaped diffusers serves as a passage for air.
  • the air introduced through this passage pressurizes the internal channel shown in Figure Ic, generating bubbles on the entire surface of the ceramic diffuser.
  • Figure 2c is a schematic diagram of a pipe-shaped ceramic diffuser according to an embodiment of the present invention in which bubbles generated from said diffuser are shown.
  • Figure 2d is the corresponding photograph.
  • a vibrator is placed either at the metallic molds or the nozzle so as to propagate vibration from the surface to the center of the ceramic diffuser.
  • This enables the ceramic diffuser to achieve an ideal particle size distribution in which not only the silica or alumina particles are dense but the particle size increases in the direction toward the center with particles on the surface being the smallest.
  • the semi-dry molding step and high temperature calcination step in the production of the inventive ceramic diffuser produces particles with uniform size and dense, regular configuration.
  • Figure 3 is a vertical cross section of illustrating the operation the apparatus for manufacturing the disc-shaped ceramic diffuser according to an embodiment of the present invention.
  • ceramic diffuser In the manufacture of said ceramic diffuser, highly purified silica or alumina devoid of impurities is ground into a fine powder first. This powder is mixed with an aqueous solution containing organic binders such as polyvinyl alcohol (PVA) to form a wet powder suitable for molding.
  • organic binders such as polyvinyl alcohol (PVA)
  • Ceramic diffusers made from alumina powders require application of relatively higher air pressure for operation than those made from silica, albeit being capable of generating finer bubbles and having a superior strength.
  • ceramic diffusers made from silica powders is able to operate under low air pressure, and thus are economical.
  • silica-based diffusers have adequate strength for air-flotation of wastewater sludge, even if they may not be as strong as alumina-based ones. Therefore, both types of ceramic diffusers are suitable and complement each other for generating microbubbles in the solid/liquid separation by air-flotation.
  • the next step following the production of the wet powder is the initial filling of the concave metallic mold 1 with this wet powder.
  • a film made from an organic material such as polyvinyl chloride (PVC) with a thickness of 0.25-0.5 mm is inserted to this wet powder.
  • PVC polyvinyl chloride
  • the thickness of this film is one of the factors decisive in determining the overall thickness of the ceramic diffuser. As the thickness of the ceramic diffuser increases, more ceramic powder is required and this lowers the economic efficiency. Thus, a film with a thickness of 0.25-0.5 mm is preferable for the optimization of the amount of ceramic powder used and the size distribution of bubbles to be generated.
  • a second filling of said wet powder is performed and the top surface is leveled evenly.
  • the convex metallic mold 2 is then driven into said wet powder by a press under a pressure of 100-200 tons for the initial compression, yielding a pre-molded ceramic diffuser out of the uncalcined wet powder.
  • the driving pressure of the press falls below 100 tons, larger bubbles are generated due to the insufficient compression of silica or alumina powder.
  • this pressure exceeds 200 tons, breakage of the ceramic diffuser occurs during high temperature molding. Therefore, the driving pressure of the press is preferably in the range of 100-200 tons.
  • the pre-molded ceramic diffuser is subject to a supersonic vibration generated by the supersonic vibrator 11 placed on the press metallic mold. Concurrent with this vibration is the compression by the press with a pressure of 10-30 tons, forming the final ceramic diffuser.
  • the pressure range of 10-30 tons allows the vibrator 11 to hold the ceramic diffuser. In addition, this pressure range allows particles to be distributed evenly instead of most being spread out towards the edges.
  • convex metallic mold 2 Through concave metallic mold 1 and convex metallic mold 2, the supersonic vibration propagates from the surface of said ceramic diffuser to its center. Small particles in the constituent ceramic powder move toward the vibrating source due to their small diameter and weight. This movement creates a particle size distribution in which particle size increases in the direction towards the center with particles on the surface being the smallest, hence to yield an ideal ceramic diffuser.
  • convex metallic mold 2 is removed first, followed by a lifting movement of piston 21, taking the ceramic diffuser formed out of concave metallic mold 1.
  • Extrusion molding is used for the manufacture since this method is quite economical in that it can produce up to 4 meters of product per minute.
  • the extruder is filled with the wet powder prepared.
  • a supersonic vibrator which produces vibration as the wet powder is extruded with a pressure in the range of 300-600 tons. Outside this pressure range, powder cannot be uniformly distributed so that it becomes difficult to generate evenly-sized bubbles. Therefore this pressure range is preferred for the extrusion molding step.
  • the disc- or pipe-shaped ceramic diffusers are introduced in an oxidative atmosphere furnace and calcined at 900 ° C-l,300 ° C to yield the ceramic diffuser of the present invention.
  • the maximum limiting temperature under which these ceramic powders can be melted is approximately l,200°C for silica powders and l,400°Cfor alumina powders. Calcination under such high temperatures supports very fine pores, which in turn leads fine air bubbles.
  • these ceramic diffusers will placed at the lower parts of wastewater precipitation tanks, these inventive ceramic diffusers should be capable of withstanding water pressure in the precipitation tank, generating air bubbles, and withstanding the pressure of the air introduced.
  • calcination is preferably performed at the given temperature range.
  • the actual method of calcination need not be limited to specific methods.
  • the use of supersonic vibration enables the ceramic diffusers to achieve ideal particle size distribution even when cheaper, relatively coarse materials are used instead materials of fine particle sizes in the manufacture of the inventive ceramic diffusers.
  • the frequency and duration of such supersonic vibration can be properly adjusted according to the shape and size of the particles. In the case of fine alumina or silica powders, 20,000-25,000 vibrations per second are preferred.
  • Example 1 Separation by air-flotation using ceramic diffuser for generating microbubbles >
  • the air-flotation was performed at about 1 meter below the water 1eve1.
  • Experimental Example 1 Measuring the size of microbubbles generated> The sizes of the microbubbles generated in example 1 and comparative example 1 were measured. The relation between the size of the generated bubbles and the size of the particles to be subject to solid/liquid separation may determine the collision efficiency, and in turn affect flotation capacity. The sizes of the bubbles generated were measured with a particle counter (LaserTrac Model PC 2400D, Hemtrac, USA)
  • microbubbles from the ceramic diffuser in example 1 had an average diameter of 51.67+0.51 urn under the pressure of 0.8 bar.
  • the microbubbles from electrode plates in comparative example 1 had an average diameter of 34.43+0.51 ⁇ m at the voltage of 220 V, current of 450 mA and current 2 density of 89.52 A/m .
  • Microbubbles with sizes suitable for an effective air- flotation were formed in both examples.
  • scale accumulates on the electrode plates, as shown in Figure 6, when the reactor is run over a long time. This scale formation diminishes the efficiency of the electrode plates, which in turn leads to fewer microbubbles formed and lessened air-flotation capacity.
  • the concentrations of the sludge accumulated on top of the reactor by the microbubbles as well as those in the reactor effluent were measured for example 1 and comparative example 1.
  • the surface loading rates (the ratio of the surface of the precipitation tank to which the sludge is introduced to the amount of sludge introduced per hour) were similar for both examples with
  • the concentration of the accumulated sludge was 14,660- 23,400 mg/L and that in the reactor effluent was 3-10 mg/L.
  • the air/solid (A/S) ratios (related to sludge flotation efficiency) were similar in both examples with 0.004-0.009 for example 1, and 0.005-0.01 for comparative example 1. In other words, large amounts of pollutants were separated by air-flotation in both examples.
  • the inventive ceramic diffuser due to its manufacturing process with applied vibration under pressure, is capable of achieving a particle size distribution in which the sizes of silica or alumina particles increase in the direction towards the center with particles on the surface being the smallest.
  • a small air pressure around 1 atm is capable of providing a uniform and steady stream of microbubbles for securing a rapid flotation of pollutants in wastewater.
  • the air-flotation method of the present invention does not suffer from scale formation as is the case with electro-flotation with electrode plates. This allows the inventive ceramic diffuser to be used conveniently and semi-permanent Iy without maintenance problems, adding to its economic advantage.
  • the enhanced productivity arising from the use of the inventive extrusion molding process for producing said ceramic diffusers supports additional cost reduction.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Hydrology & Water Resources (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Aeration Devices For Treatment Of Activated Polluted Sludge (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
  • Physical Water Treatments (AREA)
  • Compositions Of Oxide Ceramics (AREA)

Abstract

L'invention porte: sur des diffuseurs céramiques de silice et d'alumine produisant des microbulles servant à la séparation liquide/solide des polluants des eaux usées; sur leur procédé de fabrication; et sur des méthodes de traitement des eaux usées par flottation à l'air utilisant lesdits diffuseurs. Ces diffuseurs assurent une distribution en taille des particules de silice et d'alumine dont la taille croît vers le centre et décroît vers la surface. On obtient ainsi une pression de l'ordre d'une atmosphère créant un courant uniforme et constant de microbulles provoquant une flottation rapide des polluants. Les diffuseurs peuvent en outre être utilisés aisément et de manière semi- permanente sans problème d'entretien, ce qui est un plus pour leurs avantages économiques; il en est de même du procédé de fabrication des diffuseurs par moulage par extrusion qui permet une réduction supplémentaire des coûts.
PCT/KR2007/000261 2006-07-26 2007-01-16 Diffuseurs de silice et d'alumine créant des microbulles, leur procédé de fabrication, et procédé de traitement des eaux usées Ceased WO2008013349A1 (fr)

Priority Applications (2)

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CN200780025139XA CN101484393B (zh) 2006-07-26 2007-01-16 用于产生微气泡的二氧化硅或氧化铝陶瓷扩散器、其制造方法、及其采用该陶瓷扩散器使用空气浮选方法的废水处理方法
HK09111628.8A HK1131962B (en) 2006-07-26 2007-01-16 Silica or alumina ceramic diffuser for generating microbubbles, method for manufacturing the same and method for wastewater treatment using air- floatation process using the same

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KR1020060070148A KR100759834B1 (ko) 2006-07-26 2006-07-26 미세기포 발생용 실리카 또는 알루미나 세라믹 멤브레인산기관, 그의 제조방법 및 제조장치
KR10-2006-0070148 2006-07-26

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WO2013167358A1 (fr) * 2012-05-09 2013-11-14 Jens-Uwe Repke Dispositif et procédé d'épuration de l'eau par flottation
WO2016180853A1 (fr) 2015-05-11 2016-11-17 Akvolution Gmbh Dispositif et procédé de production de bulles de gaz dans un liquide
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EP3424588A4 (fr) * 2016-03-01 2019-10-30 Hirose Holdings&Co., Ltd. Dispositif d'introduction/retenue de gaz, procédé d'introduction/retenue de gaz, et tête de libération de gaz

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