WO1994002232A1 - Nouveau corps diffuseur et procede de preparation - Google Patents

Nouveau corps diffuseur et procede de preparation Download PDF

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Publication number
WO1994002232A1
WO1994002232A1 PCT/US1993/006923 US9306923W WO9402232A1 WO 1994002232 A1 WO1994002232 A1 WO 1994002232A1 US 9306923 W US9306923 W US 9306923W WO 9402232 A1 WO9402232 A1 WO 9402232A1
Authority
WO
WIPO (PCT)
Prior art keywords
gas diffusion
recited
substrate
ceramic
substrate surface
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/US1993/006923
Other languages
English (en)
Inventor
Chad A. Sheckler
Harry C. Stanton
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.)
Refractron Corp
Original Assignee
Refractron Corp
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 to US07/920,792 priority Critical patent/US5215686A/en
Priority claimed from US07/920,792 external-priority patent/US5215686A/en
Application filed by Refractron Corp filed Critical Refractron Corp
Priority to EP93918329A priority patent/EP0655944A4/fr
Priority to PCT/US1993/006923 priority patent/WO1994002232A1/fr
Publication of WO1994002232A1 publication Critical patent/WO1994002232A1/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
    • 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
    • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
    • C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
    • C04B41/4582—Porous coatings, e.g. coating containing porous fillers
    • 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
    • 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
    • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
    • C04B41/80—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only ceramics
    • C04B41/81—Coating or impregnation

Definitions

  • a ceramic diffuser body containing a ceramic substrate and a ceramic coating on the top surface of the substrate is disclosed.
  • Porous gas diffusion elements are well known to those skilled in the art. These prior art porous gas diffusers are often used to diffuse a gas (such as oxygen, ozone, air, carbon dioxide, or nitrogen) into a liquid (such as waste water or drinking water).
  • a gas such as oxygen, ozone, air, carbon dioxide, or nitrogen
  • An ASCE Standard Test (“Measurement of Oxygen Transfer in Clean Water,” July, 1984, ISBN 0-87262- 430-7) was developed by the American Society of Civil En ⁇ gineers to evaluate the efficiencies of these prior art devic ⁇ es.
  • a ceramic diffuser body which contains a ceramic substrate coated with a ceramic membrane.
  • the minimum active pore size of the substrate is from about 2 to about 5 times as great as the minimum active pore size of the ceramic membrane.
  • FIG. 1 is a flow diagram of one preferred process of the instant invention
  • Figure 2 is a sectional view of one preferred diffuser of the instant invention
  • Figure 3 is a sectional view of the diffuser of Figure 2 connected to a source of gas
  • FIG. 4 is a sectional view of another preferred diffuser of the instant invention.
  • Figure 1 illustrates one preferred process for produc ⁇ ing the diffuser body of this invention.
  • mixer 10 to mixer 10 is charged aggregate material and bonding agent.
  • the aggregate material is prefer ⁇ ably charged via line 12.
  • the bonding agent is charged via line 14.
  • the aggregate material consists essentially of ceramic material.
  • the ceramic material charged via line 12 preferably has a particle size distribution such that at least about 99 weight percent of its particles have a maximum dimension which is from about 150 to about 1,000 microns. In one embodiment, at least about 99 weight percent of the ceramic aggregate particles charged via line 12 have a maximum dimension of at least about 250 microns.
  • the ceramic aggregate material charged via line 12 preferably has a shrinkage such that, after it is formed into a green body with a substantially circular cross-section and a diameter of 7.0 inches and fired at a temperature of 1,225 degrees Centigrade for 1 hour, will exhibit a shrinkage of less than about 1.0 percent.
  • the shrinkage of the material may be determined by measuring the diameter of body prior to and after firing.
  • the ceramic material charged via line 12 is selected from the group consisting of alumina, silicon carbide, silica, mullite, zirconium silicate, and the like.
  • the ceramic material charged via line 12 is silica, which often consists of naturally occurring sand particles.
  • An amorphous glass binder may be added to the silica (via line 14); see, e.g., page 2 of EPA/625/8-85/010 Summary Report, "Fine Pore (Fine Bubble) Aeration Systems” (developed by the Water Engineering Research Laboratory, Cincinnati, Ohio) .
  • the ceramic material charged via line 12 is an alumina material such as, e.g., a 46 grit alumi ⁇ na sold by General Abrasivemaschineacher, Inc. of Niagara Falls., New York.
  • An elaborate binder, resembling porcelain, may be charged via line 14; see, e.g., page 3 of said E.P.A. report.
  • the ceramic material charged via line 12 is zircon (ZrSiO ⁇ ). In another embodiment, the cera ic material charged via line 12 is silicon carbide.
  • Mullite may be used as the ceramic material charged via line 12.
  • mullite is an aluminosilicate of the formula 3Al2 ⁇ 3.2Si ⁇ 2-
  • alumina as the ceramic aggregate material charged via line 12, and reference will be made to such alumina in the remainder of this specification.
  • a bonding agent In addition to the alumina (which is charged via line 12), from about 5 to about 20 weight percent of a bonding agent is charged via line 14.
  • This bonding agent consists essentially of inorganic material, all of whose particles have a maximum dimension smaller than about 100 microns.
  • the bonding agent preferably forms a glassy phase when subjected to a temperature of 1,225 degrees for at least 1 hour.
  • a borosilicate glass is used as the bonding agent.
  • This borosilicate glass may be formed by combining a borosilicate frit and nepheline syenite in a mixture which contains from about 20 to about 50 weight percent of borosilicate frit and from about 50 to about 80 weight percent of nepheline syenite.
  • the bonding agent charged via line 14 is a mixture of from about 20 to about 50 weight percent of a clay material and from about 80 to about 50 weight percent of a material selected from the group consist ⁇ ing of feldspar, nepheline syenite, and mixtures thereof.
  • the clay material preferably has a particle size such that sub ⁇ stantially all of its particles have a maximum dimension smaller than about 10 microns; and it may, e.g., be ball clay or bentonite.
  • the feldspar and/or the nepheline syenite material preferably has a particle size such that substantial ⁇ ly all of its particles are smaller than 40 microns.
  • the bonding agent also contains from about 20 to about 50 weight percent of glass frit.
  • the ceramic aggregate material and the bonding agent are mixed in mixer 10, preferably by dry mixing, until a substantially homogeneous mixture is obtained therein.
  • mixers known to those skilled in the art may be used.
  • Eirich R7 Mixer Eirich Machines, Ltd., Box 550, Maple, Ontario.
  • the mix ⁇ ture is then stirred until it is substantially homogeneous. Thereafter, the mixture is discharged via line 18 to former 20.
  • former 20 may be a press equipped with a die in the shape of a plate, a dome, or a disc. Any suitable press may be used such as, e.g., the 30-ton presses sold by the Fred S. Carver Inc. of Menomonee Falls, Wisconsin.
  • the green body produced by former 20 may be in the form of a plate with a thickness of from about 1.0 to about 1.5 inches thick.
  • the plate may have a shape which is square, or rectangular.
  • the green body produced by former 20 may be in the form of a disc with a diameter of from about 6 to about 12 inches and a thickness of from about 0.5 to about 2.0 inches. In one embodiment, the thickness of the disc is from about 0.5 to about 1.0 inches. In one embodiment, the diamet ⁇ er of the disc is either 7 inches, or 9 inches, or 9.5 inches, or 12 inches. See, e.g., page 6 of said E.P.A. report.
  • the green body produced in former 20 be in the shape of a dome, resembling a circular disk with a downwardly turned edge.
  • these domes are also from about 6 to about 12 inches in diameter and from about 0.5 to about 2.0 inches thick.
  • the dome is about 7.0 inches in diameter and 1.5 inches high; in this embodiment, the media is 0.6 inches thick on the edges and 0.75 inches thick on the top or flat surface. See, e.g., page 5 of said E.P.A. report and a publication by D.H. Houck et al. entitled "Survey and Evaluation of Fine Bubble Dome Diffuser Aeration Equipment," EPA-600/2-81-222, NTIS no. PB82- 105578 (United States Environmental Protection Agency, Cincin ⁇ nati, Ohio, September, 1981).
  • the dome has a diameter of about 9 inches.
  • the dome has a diameter of about 12 inches.
  • the green body formed in former 20 is then passed via line 22 to furnace 24, where it is heated to a temperature of 1,225 degrees Centigrade and maintained at at least this temperature for at least 1 hour. It is preferred to heat the green body in air at a temperature of from about 1,225 to about 1,275 degrees Centigrade for at least about 8 hours. Thereafter, the heated body is then allowed to cool, prefer ⁇ ably while in furnace 24.
  • Any conventional furnace may be used to heat the green body.
  • a tunnel kiln sold by the Lindberg Company, 304 Hart Street, Watertown, Wisconsin.
  • the materials required to produce an inorganic coating for the green body from furnace 24 may be charged to mixer 26. It is preferred that the mixture formed in mixer 26 have a coefficient of expansion which is from about 0.9 to about 1.1 times as great as the coefficient of expansion of the mixture formed in mixer 24.
  • Ceramic aggregate material is charged via line 28 to mixer 26. It is preferred that the ceramic aggregate material charged via line 28 be chemically identical to the ceramic ag ⁇ gregate material charged via line 12. However, the aggregate material charged via line 28 has a particle size distribution such that substantially all of its particles have a maximum dimension less than about 150 microns and, more preferably, less than about 50 percent of the size of the mean particle size of the ceramic aggregate material charged via line 12.
  • the alumina charged via line 12 has a mean particle size of greater than 250 microns
  • the alumina charged via line 28 has a mean particle size of about 95 microns.
  • Bonding agent is charged to mixer 26 via line 30. It is preferred that a sufficient amount of such bonding agent be charged so that the mixer 26 contains from about 80 to about 95 weight percent of ceramic aggregate material and from about 20 to about 5 weight percent of bonding agent.
  • a similar, or identical bonding agent may be charged via line 30 as is charged via line 14; it is preferred that the binding charged in the former line be identical to the binding agent charged via the latter line.
  • a sufficient amount of water is charged to mixer 26 via line 32 so that the slurry formed in such mixer has a solids content of from about 40 to about 60 weight percent.
  • surfactant may be added to mixer 26 via line 34.
  • surfactant it prefer ⁇ ably is an anionic surfactant.
  • an anionic surfactant e.g., one may use "DARVAN” 821A polyacrylate surfactant, which is sold by the R.T. Vanderbilt and Company of Norwalk, Connecticut.
  • a sus ⁇ pending agent is added to mixer 26 via line 36.
  • the function of this suspending agent is to suspend and maintain a mixture of the particulate components homogeneously.
  • suspending agents such as, e.g., Xanthan gum.
  • the ingredients are mixed in mixer 26 until a substan ⁇ tially homogeneous slurry is produced. Thereafter, the slurry is discharged via line 38 to coater 40. It is preferred that substantially all of the particles in the slurry are smaller than about 125 microns and, more preferably, less than about 100 microns.
  • the green body from furnace 24 is passed via line 52 to coater 40. Its interior surface (see Figure 2) is masked, and the top surface of the green body is dipped into the slurry; thus, the green body is only partially coated with the slurry.
  • the partially coated green body is then removed from coater 40, the top surface is then allowed to dry, and then the green body is again dipped into the slurry in order to coat the bottom surface of the green body. Thereafter, the partially coated green body is again removed from the coater 40 and allowed to dry.
  • the partially coated green body is then removed from coater 40 and charged via line 44 to furnace 46, where it is fired in accordance with the procedure used in furnace 24. It is preferred to heat the coated green body at a temperature of from about 1,225 to about 1,275 degrees Centigrade for at least about 1 hour and, more preferably, for at least about 8 hours.
  • FIG. 2 A sectional view of one preferred porous gas diffuser body is illustrated in Figure 2.
  • diffuser 48 is prefer ⁇ ably a dome-shaped body 50 comprised of gas inlet orifice 52.
  • the diameter 54 of body 50 is at least about 3.0 times as large as the maximum diameter 56 of gas inlet orifice 52; and the cross-sectional area of the solid portion of body 50 (the sum of the areas of sections 58 and 60) is at least about 3.5 times as great as the cross-sectional area of the hatched orifice area 52.
  • the coating is prepared form alumina and a bonding agent containing about 30 weight percent of ball clay and 70 weight percent of nephe ⁇ line syenite.
  • the coating 62 has a thick ⁇ ness which has a thickness which is from about 0.1 to about 1.0 millimeters and, generally, is less than about 5 percent of the thickness 64 of the substrate 66. In one preferred embodiment, the maximum thickness of substrate 66 is 1.5 inches, and the coating 62 has a thickness of from about 0.4 to about 0.6 millimeters.
  • the substrate 66 preferably has an apparent porosity of from about 35 to about 50 percent; as is known to those skilled in the art, apparent porosity is the relationship of the open pore space to the bulk volume, expressed in percent (see A.S.T.M. C242-87).
  • the coating 62 also has an apparent porosity of from about 35 to about 55 percent. Although the porosity of the coating 62 may be identical to or smaller than the porosity of substrate 66, it often is at least about 2.0 percent higher than the porosity of substrate 66.
  • the substrate 66 must have sufficient strength for its intended use.
  • the substrate 66 has a strength of at least about 1,000 pounds per square inch.
  • measurement of strength usually involves sup ⁇ porting the diffuser in a fashion similar to that used for the final assembly and then applying a 1,000 pound load to a 25 millimeter (1.0 inch) diameter area in the center of the diffuser.
  • the minimum active pore size of substrate 66 is greater than the minimum active pore size of coating 62.
  • the term minimum active pore size refers to the smallest pore in the diffuser which is actively diffus ⁇ ing gas into the liquid medium.
  • the pore size distribution of a porous body may be determined in accordance with A.S.T.M. Standard Test Method F316-86, "Test Method for Pore Size Characteristics of Mem brane Filters for Use with Aerospace Fluids.” In this test, porous bodies are mounted on a gas plenum and immersed in a liquid of known surface tension. The plenum is slowly pres ⁇ surized, and observations are made of the pressure at which the first bubble is released from the body at various gas flow rates.
  • the minimum active pore size of substrate 66 is gener ⁇ ally from about 40 to about 120 microns.
  • the minimum active pore size of coating 62 is generally from about 10 to about 40 microns.
  • the minimum active pore size of sub ⁇ strate 66 is from about 2.0 to about 5.0 times as great as the minimum active pore size of coating 62. It is preferred that the minimum active pore size of substrate 66 be from about 2.0 to about 4.0 times as great as the minimum active pore size of coating 62. In one preferred embodiment, the minimum active pore size of substrate 66 is about 3.0 times as great as the minimum active pore size of coating 62.
  • the minimum active pore size of the coating 62 on the top surface 68 of substrate 66 is at least about 2.0 times as great as the minimum active pore size of the coating 62 on the bottom surface 70 of substrate 66.
  • This difference in minimum active pore size may be obtained, e.g., by using different particle size materials to coat the top and bottom surfaces of the substrate.
  • a coarser membrane may be used on the top. This may be achieved, e.g., by using a coarser grade of ceramic aggregate for the top surface membrane, and using a finer grade of ceramic aggregate for the bottom surface membrane.
  • FIG 3 illustrates the diffuser body 48 of Figure 2 connected to a source of gas 72; this embodiment is especial ⁇ ly suitable for diffusing ozone gas.
  • diffuser body 48 is attached to inlet casting 74 by means of bolt 76, gasket 78, and gasket 80.
  • bolt 76 is preferably a stainless steel bolt.
  • Gaskets 78 and 80 are preferably an ozone-resistant elastomer- ic material such as "HYPALON" 70 (a chlorosulfonated polyethy ⁇ lene sold by the Du Pont de Nemours and Company of Wilmington, Delaware) .
  • HYPALON a chlorosulfonated polyethy ⁇ lene sold by the Du Pont de Nemours and Company of Wilmington, Delaware
  • the uniformity of the diffuser body may be tested with a visual test. Alternatively, or additionally, the uniformity of the diffuser may be tested with the uniformity tests de ⁇ scribed the Environmental Protection Agency's "Design Manual — Fine Pore Aeration Systems" (EPA/625/1-89/023, published in 1989 by the Center for Environmental Research Information, Risk Reduction Engineering Laboratory, Cincinnati, Ohio) .
  • One such uniformity test measures the water displaced from an inverted graduated cylinder in a given period of time and compares the flow rate so determined for a specific location above the diffuser to other areas.
  • a diffuser's uniformity can be measured by comparing the values for different areas of its active surface.
  • Figure 4 is a sectional view of another preferred embodiment of applicant's invention, illustrating a conically- shaped diffuser body. This sectional view, like the sectional views depicted in Figures 2 and 3, was taken through a section taken through the centerpoint of the top surface of the dif ⁇ fuser body.
  • diffuser body 82 is comprised of substrate 84 and coating 86, which are similar to the sub ⁇ strate 66 and coating 62 depicted in Figures 2 and 3. As with the diffuser body of Figures 2 and 3, the coating 86 is not applied to the interior surfaces 88 and 90 of the diffuser body 82.
  • Figure 5 is a sectional view of another preferred embodiment of applicant's invention, illustrating another conically-shaped diffuser body 91. Referring to Figure 5, it will be seen that substrate 92 is coated with coating 94 over substantially every exterior surface except for exterior surfaces 96 and 98. Thus, unlike the embodiment of Figure 3, the tip 100 contains operative diffusing material (coating 94) .
  • An adaptor such as adaptor 102, is connected to sub ⁇ strate 92 by conventional means such as, e.g., adhesive 104, adhesive 106, and adhesive 108.
  • adaptor 102 preferably contains pipe threads 104 and a flat section 106 which a wrench may grasp.
  • the adaptor 102 may be made from conventional materials such as, e.g., plastic material (such as polyvinyl chloride), metal material (such as stainless steel), and the like.
  • the self-supporting diffuser head embodiments of applicant's invention are substantially less expensive than the prior art devices which required fabricated holders (which often con ⁇ sisted of plastic or stainless steel) and which usually communicated with precise orifices and often presented leakage problems at the junctures of the holders and the diffuser bodies. Applicant's devices are substantially less likely to present such leakage problems and are greatly simplified structures.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Catalysts (AREA)

Abstract

Elément diffuseur de gaz rigide, monolithique et poreux, composé d'un corps (50) de particules solides et comprenant un substrat céramique perméable partiellement revêtu (66). Le substrat se compose essentiellement d'un premier matériau céramique poreux, qui présente une porosité apparente comprise entre environ 35 et environ 50 %, et une taille minimale de pores actifs comprise entre environ 40 et environ 120 microns; il est partiellement enduit d'un revêtement (62) composé essentiellement d'un deuxième matériau céramique, qui présente une porosité apparente comprise entre environ 35 et environ 55 %, et une taille minimale de pores actifs comprise entre environ 10 et environ 40 microns. La taille minimale de pores actifs du substrat est d'environ 2 à environ 5 fois plus grande que la taille minimale de pores actifs du revêtement.
PCT/US1993/006923 1992-07-28 1993-07-23 Nouveau corps diffuseur et procede de preparation Ceased WO1994002232A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US07/920,792 US5215686A (en) 1992-07-28 1992-07-28 Diffuser body and method of manufacture
EP93918329A EP0655944A4 (fr) 1992-07-28 1993-07-23 Nouveau corps diffuseur et procede de preparation.
PCT/US1993/006923 WO1994002232A1 (fr) 1992-07-28 1993-07-23 Nouveau corps diffuseur et procede de preparation

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US07/920,792 US5215686A (en) 1992-07-28 1992-07-28 Diffuser body and method of manufacture
US07/920,792 1992-07-28
PCT/US1993/006923 WO1994002232A1 (fr) 1992-07-28 1993-07-23 Nouveau corps diffuseur et procede de preparation

Publications (1)

Publication Number Publication Date
WO1994002232A1 true WO1994002232A1 (fr) 1994-02-03

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Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3507253A (en) * 1968-10-07 1970-04-21 Aquariums Inc Aquarium air stone ornament
US3689611A (en) * 1970-08-06 1972-09-05 American Can Co Method of making glazed ceramic bonded expanded vermiculite articles
US3753746A (en) * 1966-10-19 1973-08-21 O Koerner Permeable refractory products
US4046845A (en) * 1976-06-23 1977-09-06 Ferro Corporation Air diffuser element
US4118450A (en) * 1973-05-18 1978-10-03 Shikoky Kaken Kogyo Kabushiki Kaisha Method for producing inorganic porous shaped material
US4184885A (en) * 1979-01-25 1980-01-22 General Electric Company Alumina core having a high degree of porosity and crushability characteristics
US4261932A (en) * 1978-10-19 1981-04-14 Water Pollution Control Corporation Diffusion element with boundary zone treatment
US4746341A (en) * 1985-04-17 1988-05-24 Ngk Insulators, Ltd. Porous ceramic filter and process of producing the same
US4820412A (en) * 1986-02-18 1989-04-11 Meyer Rudolphi Karl U Element for the transfer of gas into liquids, in particular, for the transfer of oxygen in sewage treatment plants
US4965230A (en) * 1988-03-02 1990-10-23 Inax Corporation Alumina porous body and production of the same

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3753746A (en) * 1966-10-19 1973-08-21 O Koerner Permeable refractory products
US3507253A (en) * 1968-10-07 1970-04-21 Aquariums Inc Aquarium air stone ornament
US3689611A (en) * 1970-08-06 1972-09-05 American Can Co Method of making glazed ceramic bonded expanded vermiculite articles
US4118450A (en) * 1973-05-18 1978-10-03 Shikoky Kaken Kogyo Kabushiki Kaisha Method for producing inorganic porous shaped material
US4046845A (en) * 1976-06-23 1977-09-06 Ferro Corporation Air diffuser element
US4261932A (en) * 1978-10-19 1981-04-14 Water Pollution Control Corporation Diffusion element with boundary zone treatment
US4184885A (en) * 1979-01-25 1980-01-22 General Electric Company Alumina core having a high degree of porosity and crushability characteristics
US4746341A (en) * 1985-04-17 1988-05-24 Ngk Insulators, Ltd. Porous ceramic filter and process of producing the same
US4820412A (en) * 1986-02-18 1989-04-11 Meyer Rudolphi Karl U Element for the transfer of gas into liquids, in particular, for the transfer of oxygen in sewage treatment plants
US4965230A (en) * 1988-03-02 1990-10-23 Inax Corporation Alumina porous body and production of the same

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