Patent EA-000249-B1 (EA)
Title: Flameless combustor
Inventor: KARANIKAS JOHN MICHAEL
IPC: A47G25/90
Filed: 1996-12-17
Abstract: 1. A flameless combustor comprising: an axial combustion chamber (14) in communication with an inlet for oxidant at one end and in communication with a combustion product outlet at the other end; a fuel conduit (12) within the axial combustion chamber (14), the fuel conduit (12) defining a fuel volume, the fuel volume in communication with a fuel supply, and in communication with the combustion chamber through a plurality of orifices (13) located along the fuel conduit (12), each of the orifices (13) separated by an interval distance wherein the oxidant can pass through the combustion chamber (14) and mix with fuel passing through the orifices (13) from the fuel volume as the oxidant passes from the inlet end to the combustion product outlet; a catalytic surface (19) located within the axial combustion chamber (14), the catalytic surface (19) effective to reduce the autoignition temperature of a mixture of fuel and oxidant from a noncatalyzed autoignition temperature to a catalyzed autoignition temperature; and electrical heating means for ignition of the mixture of oxidant and fuel within the axial combustion chamber, characterized in that the electrical heating means comprise an electrical power supply (15) effective to pass electrical current through the fuel conduit (12) in an amount effective to heat the fuel conduit (12) in the vicinity of at least one orifice (13) to a temperature above a temperature at which the fuel will ignite when the fuel passes through the orifices (13). 2. The combustor of Claim 1 wherein the catalytic surface (19) comprises an outer surface of the fuel conduit (12). 3. The combustor of Claim 1 wherein the catalytic surface (19) comprises an inner surface of the combustion chamber (14). 4. The combustor of Claim 1 wherein the combustion chamber (14) is defined by an inside surface of a tubular (10) within a wellbore. 5. The combustor of Claim 1 further comprising a means to remove heat from the interval of the combustion chamber (14) between at least two orifices (13), the means to remove heat capable of removing an amount of heat that results in the temperature within the combustion chamber (14) being, when in a steady state, greater than the autoignition temperature of the fuel in air, but less than about 1100  degree C. 6. The combustor of Claim 5 wherein the means to remove heat from an interval of the combustion chamber between at least two of the orifices (13) comprises the formation (1) to which heat can be transferred from the combustion chamber (14) by convection and conduction through an annular space surrounding the combustion chamber (14). 7. The combustor of Claim 1 wherein the catalytic surface (19) comprises palladium. 8. The combustor of Claim 1 wherein the combustor is within a wellbore (3). 9. The combustor of Claim 8 wherein the fuel conduit (12) is a tubular suspended from a wellhead and the combustor further comprises a means (15) to apply electrical power to the fuel conduit at the wellhead; and the fuel conduit is of a lesser thickness in the vicinity of the orifices than above the orifices and the fuel conduit is grounded from a point below at least one orifice. 10. A flameless combustor comprising: an axial combustion chamber (14) in communication with an inlet for oxidant at one end and in 1. A fiameless combustor comprising: an axial combustion chamber (14) in communication with an inlet for oxidant at one end and in communication with a combustion product outlet at the other end; a fuel conduit (12) within the axial combustion chamber (14), the fuel conduit (12) defining a fuel volume, the fuel volume in communication with a fuel supply, and in communication with the combustion chamber through a plurality of orifices (13) located along the fuel conduit (12), each of the orifices (13) separated by an interval distance wherein the oxidant can pass through the combustion chamber (14) and mix with fuel passing through the orifices (13) from the fuel volume as the oxidant passes from the inlet end to the combustion product outlet; a catalytic surface (19) located within the axial combustion chamber (14), the catalytic surface (19) effective to reduce the autoignition temperature of a mixture of fuel and oxidant from a noncatalyzed autoignition temperature to a catalyzed autoignition temperature; and electrical heating means for ignition of the mixture of oxidant and fuel within the axial combustion chamber; characterized in that the electrical heating means comprise an electrical power supply (15) effective to pass electrical current through the fuel conduit (12) in an amount effective to heat the fuel conduit (12) in the vicinity of at least one orifice (13) to a temperature above a temperature at which the fuel will ignite when the fuel passes through the orifices (13). 11. The combustor of Claim 10 wherein the combustor is within a wellbore (3). 12. The combustor of Claim 11 wherein the fuel conduit (12) is a tubular suspended from a wellhead; electrical power is applied at the wellhead; the fuel conduit is of a lesser thickness in the vicinity of the orifices (13) than above the orifices; and the fuel conduit is grounded from a point below at least one orifice (13). 13. A method to ignite a flameless combustor comprising: providing an axial combustion chamber (14) in communication with an inlet for oxidant at one end and in communication with a combustion product outlet at the other end; providing a fuel conduit (12) within the axial combustion chamber (14), the fuel conduit (12) defining a fuel volume, the fuel volume in communication with a fuel supply, and in communication with the combustion chamber (14) through a plurality of orifices (13) located along the fuel conduit (12); passing an oxidant to the combustion chamber (14); passing a stream of fuel to the fuel volume; and heating the stream of fuel, oxidant, or both the stream of fuel and oxidant to a temperature that results in reaction of the oxidant and the fuel when fuel combines with the oxidant; characterized in that the oxidant is selected from the group comprising nitrous oxide and supplemental oxygen and that the method further comprises: continuing to pass the oxidant to the combustion chamber (14) and fuel to the fuel conduit until the temperature within the combustion chamber (14) exceeds an autoignition temperature of the fuel in air; and replacing the oxidant with air after the temperature within the combustion chamber (14) exceeds the autoignition temperature of the fuel in air. 14. The method of Claim 13 further comprising the step of passing an amount of electricity through the fuel conduit (12) sufficient to cause the fuel conduit (12), for at least a portion of the conduit (12) in the vicinity of at least one orifice (13), to heat to a temperature of at least 260  degree C. 15. The method of Claim 13 further comprising the step of providing a catalytic surface (19) within the combustion chamber (14), the catalytic surface (19) effective to reduce the temperature at which the fuel and oxidant react in the vicinity of the catalytic surface (19). 16. The method of Claim 13 wherein the fuel is hydrogen. 17. The method of Claim 13 wherein the fuel comprises hydrogen and carbon monoxide.