Methods and systems for reducing silica recession in silicon-containing materials
The present disclosure relates to methods and systems for reducing silica recession of silicon-containing ceramics or silicon-containing ceramic composites, particularly those exposed to a combustion gas or to combustion gas environments, including those exposed to high temperature combustion gas environments. The methods and systems involve silicon-doping of compressed air and/or removal of moisture from compressed air prior to co-mingling the treated compressed air with the combustion gas to which the silicon-containing ceramics or silicon-containing ceramic composites are exposed.
1. A method of reducing silica recession, comprising:
compressing air with an air compressor;
exposing a silicon-containing ceramic or silicon-containing ceramic composite to a high temperature combustion gas environment provided by a combustor, wherein the combustor receives a first portion of compressed air from the compressor through a first pathway; and
contacting a target surface of the silicon-containing ceramic or silicon-containing ceramic composite with a dehumidified gas mixture, thereby reducing silica recession of the target surface,
wherein the dehumidified gas mixture comprises a second portion of compressed air from the compressor through a second pathway treated with a moisture removal agent effective to remove moisture from the second portion of compressed air, the method further comprising
injecting silicon into the second portion of compressed air at a location proximate the target surface,
wherein the silicon is injected into the second portion of compressed air before, after, or both before and after dehumidifying the second portion of compressed air.
2. The method according to claim 1 , wherein the dehumidified gas mixture comprises combustion gas co-mingled with the second portion of compressed air treated with the moisture removal agent.
3. The method according to claim 1 , wherein said moisture removal agent comprises any inorganic material, organic material, or mechanical device effective to remove moisture from the second portion of compressed air.
4. The method according to claim 3 , wherein the inorganic material is selected from the group consisting of a silica gel, and anhydrous calcium sulfate.
5. The method according to claim 1 , wherein the silicon-containing ceramic is selected from the group consisting of silicon carbide, silicon carbide-silicon carbide composite, silicon nitride, silicon-silicon carbide, molybdenum silicide, and mixtures thereof.
6. The method according to claim 5 , wherein the silicon-containing ceramic is silicon carbide-silicon carbide composite.
7. The method according to claim 1 , wherein the silicon-containing ceramic comprises silicon as a predominant component.
8. The method according to claim 1 , wherein the silicon-containing ceramic composite is a continuous fiber reinforced ceramic composite.
9. The method according to claim 8 , wherein the fiber is selected from the group consisting of carbon, silicon carbide, silicon carbide-containing material, and mixtures thereof.
10. The method according to claim 1 , wherein the silicon-containing ceramic or silicon-containing ceramic composite is a high temperature turbine component.
11. The method according, to claim 1 , wherein silica recession of the silicon-containing ceramic or silicon-containing ceramic composite is reduced by a recession rate factor of at least 2 and up to 100 compared to a silicon-containing ceramic or silicon-containing ceramic composite exposed to combustion gas without the dehumidified gas mixture.
12. The method according to claim 1 further comprising:
creating a laminar flow of the dehumidified gas mixture over the target surface of the silicon-containing ceramic or silicon-containing ceramic composite.
13. A system for reducing silica recession, said system comprising:
a combustor providing a high temperature combustion gas to a at least one silicon-containing ceramic or silicon-containing ceramic composite;
an air compressor providing a first portion of compressed air to the combustor through a first pathway to produce the combustion gas and a second portion of compressed air through a second pathway for co-mingling with the combustion gas;
at least one dehumidifying component providing a moisture removal agent to the second portion of compressed air prior to co-mingling dehumidified compressed air with the combustion gas; and
at least one silicon injector for injecting silicon into the second portion of compressed air proximate to the at least one silicon-containing ceramic or silicon-containing ceramic composite.
14. The system according to claim 13 , wherein said moisture removal agent comprises any inorganic material, organic material, or mechanical device effective to remove moisture from the second portion of compressed air.
15. The system according to claim 14 , wherein the inorganic material is selected from the group consisting of a silica gel, and anhydrous calcium sulfate.
16. The system according to claim 13 , wherein the silicon-containing ceramic or silicon-containing ceramic composite are turbine components selected from the group consisting of combustion liners, vanes and blades, nozzles, buckets, transition pieces, and shrouds.
17. The system according to claim 13 , wherein the system is integrated as part of a land based gas turbine apparatus, aircraft engine, or heat exchanger.
18. The system according to claim 13 , wherein the at least one silicon injector is positioned so that injection of the silicon is performed immediately prior to co-mingling the combustion gas with the second portion of compressed air.