Open-cell glass crystalline porous material

• US 6,444,162 B1
• Filed: 11/27/2000
• Issued: 09/03/2002
• Est. Priority Date: 11/27/2000
• Status: Expired due to Fees

• Current Assignee: United States Department of Energy
• Original Assignee: United States Department of Energy
• Inventors: Revenko, Yurii A., Tranter, Troy J., Aloy, Albert S., Anshits, Alexander G., Knecht, Dieter A., Tretyakov, Alexander A., Macheret, Yevgeny, Sharonova, Olga M., Zykova, Irina D., Vereshchagina, Tatiana A., Lubtsev, Rem I.
• Primary Examiner(s): DERRINGTON, JAMES H
• Application Number:
  US09/721,962
• Time in Patent Office: 645 Days
• Field of Search: 264/43, 264/44, 264/628, 264/669, 264/125
• US Class Current: 264/628
• CPC Class Codes: C03C 11/00 Multi-cellular glass ; Porous or hollow glass or glass particles
• CPC Class Codes: C04B 18/082 Cenospheres
• CPC Class Codes: C04B 2111/00767 for waste stabilisation purposes
• CPC Class Codes: C04B 2111/00793 as filters or diaphragms
• CPC Class Codes: C04B 2111/0081 as catalysts or catalyst carriers
• CPC Class Codes: C04B 28/26 Silicates of the alkali metals
• CPC Class Codes: C04B 32/005 Artificial stone obtained by melting at least part of the composition, e.g. metal C04B28/36 and C03C take precedence; cast stone from molten slag C04B5/00; artificial stone obtained by melting the polymeric ingredient of the composition C04B26/00
• CPC Class Codes: C04B 38/0058 open porosity
• CPC Class Codes: C04B 38/08 by adding porous substances
• CPC Class Codes: C04B 40/0268 Heating up to sintering temperatures C04B41/0072 takes precedence
• CPC Class Codes: Y02W 30/91 Use of waste materials as fillers for mortars or concrete

Abstract

An open-cell glass crystalline porous material made from hollow microspheres which are cenospheres obtained from fly ash, having an open-cell porosity of up to 90 vol. % is produced. The cenospheres are separated into fractions based on one or more of grain size, density, magnetic or non-magnetic, and perforated or non-perforated. Selected fractions are molded and agglomerated by sintering with a binder at a temperature below the softening temperature, or without a binder at a temperature about, or above, the softening temperature but below the temperature of liquidity. The porous material produced has an apparent density of 0.3-0.6 g/cm³, a compressive strength in the range of 1.2-3.5 MPa, and two types of openings: through-flow wall pores in the cenospheres of 0.1-30 micrometers, and interglobular voids between the cenospheres of 20-100 micrometers. The porous material of the invention has properties useful as porous matrices for immobilization of liquid radioactive waste, heat-resistant traps and filters, supports for catalysts, adsorbents and ion-exchangers.

Claims

1. A method of making an open-cell glass crystalline porous material containing cenospheres obtained from fly ash, said porous material having an open-cell porosity of about 40 vol. % up to about 90 vol. %, said method comprising separating said cenospheres, molding a selected fraction of said separated cenospheres, and agglomerating said cenospheres under sintering conditions, said sintering conditions including isothermal holding of said cenospheres in an air atmosphere at a temperature above 800°

C. but below the temperature of liquidity of said cenospheres.

2. The method of claim 1 including the step of removing broken cenospheres and accessory particles before said molding.

3. The method of claim 2 wherein said separating comprises one or more of the following steps, in any order:

separating by size, by density, by magnetic or non-magnetic property, and separating perforated from non-perforated cenospheres.

4. The method of claim 3 wherein said separating comprises separating by size and by density.

5. The method of claim 3 wherein said separating comprises separating by density and separating of magnetic cenospheres from non-magnetic cenospheres.

6. The method of claim 3 wherein said separating comprises separating by size, separating of perforated from non-perforated cenospheres and separating by density.

7. The method of claim 3 wherein said separating steps comprise:

separating of magnetic cenospheres from non-magnetic cenospheres, separating by size, separating by density, and separating of perforated from non-perforated cenospheres.

8. The method of claim 3 further comprising forming a mixture before said molding, by mixing said non-magnetic cenospheres with a wetting agent and a binder in a weight ratio of cenospheres:

wetting agent;

binder of about 1;

(0.012-0.29);

(0.15-0.30), said molding comprising compacting said mixture by one-side pressing in a press form up to reduction of the mixture volume by 10-20%.

9. The method of claim 8 further comprising drying said compacted mixture containing cenospheres at about 160°

C. for about 2 hours and sintering for about 0.5-1 hour at a temperature of about 850°

C.

10. The method of claim 8 wherein said binder is a liquid silicate glass and said wetting agent is water.

11. The method of claim 3 further comprising selecting a separated fraction of said non-magnetic non-perforated cenospheres, molding and agglomerating said cenospheres under a sintering temperature of about 1100°

C., and treating said agglomerated cenospheres with acid reagents selected from the group comprising 3-6 M hydrochloric acid;

NH₄F—

HF—

H₂O with content of F⁻

about 15-30 gram-ions per liter at a molar ratio NH₄F/HF of about 0.1-1.0;

NH₄F—

HCl—

H₂O with a content of F⁻

about 1-10 gram-ions per liter at a molar ratio F⁻

/Cl⁻

of about 0.1-1.0.

12. The method of claim 3 wherein said cenospheres are naturally perforated.

13. The method of claim 3 wherein said cenospheres are chemically perforated with acid.

14. The method of claim 13 wherein said acid is hydrochloric acid.

15. The method of claim 13 wherein said acid is a reagent containing hydrofluoric acid.

16. The method of claim 3 wherein said selected fraction comprises non-perforated cenospheres.

17. The method of claim 3 wherein said selected cenospheres comprise a mixture of non-perforated cenospheres and naturally perforated cenospheres in a weight ratio of non-perforated cenospheres-to-perforated cenospheres of about 9:

1.

18. The method of claim 3 wherein said molding comprises placing said selected cenospheres in a refractory mold of a predetermined shape, placing said mold in a muffle and holding said mold at a temperature above 1000°

C. but below the temperature of liquidity for about 20-60 minutes.

19. The method of claim 18 wherein said cenospheres are non-perforated cenospheres.

20. The method of claim 18 wherein said cenospheres comprise a mixture of non-perforated cenospheres and naturally perforated cenospheres in a weight ratio of non-perforated cenospheres-to-perforated cenospheres of about 9:

1.