Method to prevent recession loss of silica and silicon-containing materials in combustion gas environments

• US 6,517,341 B1
• Filed: 02/26/1999
• Issued: 02/11/2003
• Est. Priority Date: 02/26/1999
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Luthra, Krishan Lal, Brun, Milivoj Konstantin
• Primary Examiner(s): Bennett, Henry
• Assistant Examiner(s): Cocks, Josiah C.
• Application Number:
  US09/259,364
• Time in Patent Office: 1,446 Days
• Field of Search: 431/2, 431/4, 427/140, 427/142, 427/239, 427/331, 427/238, 427/237, 427/249.15, 427/255.11, 427/255.18, 427/255.17, 427/255.19, 427/255.21, 427/255.37, 427/255.393, 443/20, 443/21, 443/57, 443/62, 443/64, 443/70, 443/85, 264/30, 110/343, 110/342
• US Class Current: 431/2
• CPC Class Codes: C04B 35/565 based on silicon carbide
• CPC Class Codes: C04B 35/58 based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides containing free binder metal C22C29/00
• CPC Class Codes: C04B 35/584 based on silicon nitride
• CPC Class Codes: C04B 35/806 The matrix of the ceramic products consisting of non-oxides only
• CPC Class Codes: C04B 41/0072 Heat treatment
• CPC Class Codes: C04B 41/009 characterised by the material treated
• CPC Class Codes: C04B 41/4519 application under an other specific atmosphere
• CPC Class Codes: C04B 41/4529 applied from the gas phase
• CPC Class Codes: C04B 41/4556 coating or impregnating with a product reacting with the substrate, e.g. generating a metal coating by surface reduction of a ceramic substrate
• CPC Class Codes: C04B 41/5035 Silica
• CPC Class Codes: C04B 41/87 Ceramics
• CPC Class Codes: C10L 1/1291 Silicon and boron containing compounds
• CPC Class Codes: C10L 1/28 containing silicon

Abstract

While silicon-containing ceramics or ceramic composites are prone to material loss in combustion gas environments, this invention introduces a method to prevent or greatly reduce the thickness loss by injecting directly an effective amount, generally in the part per million level, of silicon or silicon-containing compounds into the combustion gases.

Claims

1. A method to reduce material loss of silicon-containing ceramics and silicon-containing ceramic composites in a combustion gas environment comprising the step of injecting an effective amount of silicon into said combustion gas environment, where the silicon is at least one of elemental silicon, a silicon-containing compound or mixtures thereof where an effective amount of silicon is an amount of silicon injected in the combustion gas environment that prevents or reduces volatilization of a silica film located on the silicon-containing ceramic and silicon-containing ceramic composites.

2. A method according to claim 1 where the silicon-containing ceramic is selected from the group consisting of silicon carbide, silicon nitride, silicon-silicon carbide, molybdenum silicide and mixtures thereof.

3. A method according to claim 2 where the silicon-containing ceramic is silicon carbide.

4. A method according to claim 2 where the silicon-containing ceramic is silicon nitride.

5. A method according to claim 1 where the silicon-containing ceramic comprises silicon as the predominant component.

6. A method according to claim 2 where the silicon-containing ceramic composite is a continuous fiber reinforced ceramic composite.

7. A method according to claim 6 where the fiber is selected from the group consisting of carbon, silicon carbide, silicon carbide-containing material, and mixtures thereof.

8. A method according to claim 6 where the fiber has at least one coating on the fiber surface.

9. A method according to claim 8 where the coating is selected from the group consisting of boron nitride, silicon doped boron nitride, silicon nitride, silicon carbide, carbon and mixtures thereof.

10. A method according to claim 1 where the combustion gas environment contains products from combustion of liquid fuels, natural gas, hydrogen or coal.

11. A method according to claim 10 where the products from combustion of fuel contain up to about nineteen percent water vapor by volume.

12. A method according to claim 1 where the silicon is injected into combustion gases, fuel, combustion air or mixtures thereof.

13. A method according to claim 1 where the silicon or silicon-containing compound is injected as solid matter, a slurry, a liquid, a liquid solution, an atomizing spray, a gaseous substance or a mixture thereof.

14. A method according to claim 1 where an effective amount is about 0.01 to about 10.0 parts per million by weight of the combustion gases.

15. A method according to claim 1 where the silicon-containing ceramic or silicon-containing composite has a silica film on its surface.

16. A method according to claim 1 where the combustion gas environment is at a temperature of at least 500°

C.

17. A method according to claim 16 where the temperature is above 1000°

C.

18. The method of claim 1, comprising injecting silicon to a silicon level of about 0.01 to about 10.0 parts per million by weight of combustion gases.

19. The method of claim 1, comprising injecting silicon to a silicon level of about 0.009 to about 0.6 parts per million by weight of combustion gases.

20. A method according to claim 1 where the silicon-containing compound is selected from the group consisting of siloxanes, silanes, silica, silicones, silicon carbides, silicon nitrides, silicon oxides, silicates, sand and, mixtures thereof.

21. A method according to claim 20 where the siloxane is octamethylcyclotetrasiloxane, hexamethyldisiloxane or mixtures thereof.

22. A method to maintain long-term chemical durability of silicon-containing ceramics or silicon-containing composites in combustion gas environments comprising mixing parts per million of silicon or silicon-containing compounds in combustion gases during operation where the silicon or silicon-containing compounds are mixed in the combustion gas environment to prevent or reduce volatilization of a silica film located on the silicon-containing ceramic and silicon-containing ceramic composites.

23. A method according to claim 22 where the silicon-containing ceramic is selected from the group consisting of silicon carbide, silicon nitride, silicon-silicon carbide, molybdenum silicide, and mixtures thereof.

24. A method according to claim 23 where the silicon-containing ceramic is silicon carbide.

25. A method according to claim 22 where the silicon-containing ceramic composite is selected from the group consisting of silicon carbide, silicon nitride, silicon-silicon carbide, molybdenum silicide and mixtures thereof.

26. A method according to claim 25 where the silicon-containing ceramic composite is a continuous fiber ceramic composite.

27. A method according to claim 26 where the fiber is selected from the group consisting of carbon, silicon carbide, silicon carbide-containing material, and mixtures thereof.

28. A method according to claim 26 where the fiber has at least one coating on the fiber surface.

29. A method according to claim 28 where the coating is selected from the group consisting of boron nitride, silicon doped boron nitride, silicon nitride, silicon carbide, carbon and mixtures thereof.

30. A method according to claim 22 where the combustion gas environment contains products from combustion of liquid fuels or natural gas.

31. A method according to claim 30 where the products from combustion fuel contain up to about nineteen percent water vapor by volume.

32. A method according to claim 22 where the silicon is injected into combustion gases, fuel, combustion air or mixtures thereof.

33. A method according to claim 22 where the silicon or silicon-containing compound is mixed as solid matter, a slurry, a liquid solution, an atomizing spray, a gaseous substance or a mixture thereof.

34. A method according to claim 22 where about 0.01 to about 10.0 parts per million by weight of silicon or silicon-containing compounds are mixed with the combustion gases.

35. A method according to claim 22 where the silicon-containing ceramic or silicon-containing ceramic composite is a combustion liner, a shroud, or a mixture thereof.

36. A method according to claim 22 where the silicon-containing ceramic or silicon-containing composite has a silica film on its surface.

37. A method according to claim 22 where the combustion gas environment is at a temperature of at least 500°

C.

38. A method according to claim 37 where the temperature is above 1000°

C.

39. A silicon-containing ceramic or ceramic composite component in a combustion gas environment, according to claim 22, of at least 500°

C. having a chemically stable silicon oxide film on a surface of said ceramic or ceramic composite component.

40. A method according to claim 22 where the silicone-containing compound is a low viscosity liquid.

41. A method according to claim 22 where the silicone-containing compound is a low viscosity liquid.

42. The method of claim 22, comprising injecting silicon to a silicon level of about 0.01 to about 10.0 parts per million by weight of combustion gases.

43. The method of claim 22, comprising injecting silicon to a silicon level of about 0.009 to about 0.6 parts per million by weight of combustion gases.

44. A method according to claim 22 where the silicon-containing compound is selected from the group consisting of siloxanes, silanes, silica, silicones, silicon carbides, silicon nitrides, silicon oxides, silicates, sand and, mixtures thereof.

45. A method according to claim 44 where the siloxane is octamethylcyclotetrasiloxane, hexamethyldisiloxane or mixtures thereof.