초록

A down-fired flame burner includes a flame holder positioned below the burner. The flame holder includes a plurality of perforations that collectively confine a combustion reaction of the burner to the flame holder.

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1. A down-fired burner comprising: a down-fired fuel nozzle configured to output fuel in a downward direction;an oxidant source configured to output an oxidant; anda flame holder positioned below the down-fired fuel nozzle, the flame holder including: an input surface facing the down-fired fuel nozz

1. A down-fired burner comprising: a down-fired fuel nozzle configured to output fuel in a downward direction;an oxidant source configured to output an oxidant; anda flame holder positioned below the down-fired fuel nozzle, the flame holder including: an input surface facing the down-fired fuel nozzle;an output surface opposite the fuel nozzle; anda plurality of perforations extending from the input surface to the output surface and collectively configured to promote a combustion reaction of the fuel and oxidant within the perforations, wherein the flame holder is a refractory material. 2. The down-fired burner of claim 1, wherein the flame holder is configured to contain a majority of the combustion reaction within the perforations. 3. The down-fired burner of claim 1, wherein the flame holder is configured to contain 80% or more of the combustion reaction within the perforations. 4. The down-fired burner of claim 1, wherein the flame holder is an integral structure. 5. The down-fired burner of claim 1, wherein the flame holder is configured to initiate the combustion reaction. 6. A down-fired burner, comprising: a down-fired fuel nozzle configured to output fuel in a downward direction;an oxidant source configured to output an oxidant;a flame holder positioned below the down-fired fuel nozzle, the flame holder including: an input surface facing the down-fired fuel nozzle;an output surface opposite the fuel nozzle; and a plurality of perforations extending from the input surface to the output surface and collectively configured to promote a combustion reaction of the fuel and oxidant within the perforations; anda preheating mechanism configured to heat the flame holder prior to starting the combustion reaction. 7. The down-fired burner of claim 6, wherein the preheating mechanism comprises a second fuel nozzle configured to generate a flame adjacent to the flame holder. 8. The down-fired burner of claim 6, wherein the preheating mechanism comprises a laser configured to irradiate the flame holder. 9. The down-fired burner of claim 6, wherein the down-fired fuel nozzle is an adjustable nozzle and the preheating mechanism is configured to move the fuel nozzle closer to the flame holder during a preheating period and to retract the fuel nozzle after the preheating period. 10. The down-fired burner of claim 6, comprising: a temperature sensor configured to measure a temperature of the flame holder; anda control circuit coupled to the temperature sensor, the fuel nozzle, and the preheating mechanism and configured to cause the fuel nozzle to output the fuel when the temperature of the flame holder is above a threshold temperature. 11. The down-fired burner of claim 10, wherein the threshold temperature corresponds to a combustion temperature at which the flame holder can initiate combustion of the fuel within the perforations. 12. The down-fired burner of claim 6, comprising a control circuit coupled to the preheating mechanism and the fuel nozzle and configured to initiate the fuel nozzle after the preheating mechanism has operated for longer than a threshold time. 13. The down-fired burner of claim 6, wherein the preheating mechanism includes an electrical resistor coupled to the flame holder, the preheating mechanism being configured to heat the flame holder by passing a current through the electrical resistor. 14. A down-fired burner, comprising: a down-fired fuel nozzle configured to output fuel in a downward direction;an oxidant source configured to output an oxidant;a flame holder positioned below the down-fired fuel nozzle, the flame holder including: an input surface facing the down-fired fuel nozzle;an output surface opposite the fuel nozzle; anda plurality of perforations extending from the input surface to the output surface and collectively configured to promote a combustion reaction of the fuel and oxidant within the perforations; anda tube extending vertically adjacent to the flame holder and containing a catalyst. 15. The down-fired burner of claim 14, wherein the flame holder is configured to heat the tube and cause a reaction between the catalyst and a reactant in the tube. 16. The down-fired burner of claim 14, wherein the tube comprises: a first vertical portion;a second vertical portion; anda connecting portion connecting the first vertical portion to the second vertical portion such that the tube is substantially in a U shape. 17. The down-fired burner of claim 16, wherein the tube comprises: an input configured to pass reactant into the first vertical portion; andan output configured to pass from the second vertical portion a reaction product of the reactant and the catalyst. 18. The down-fired burner of claim 16, wherein the flame holder is positioned between the first and second vertical portions of the tube. 19. The down-fired burner of claim 1, wherein the perforations are isolated from each other by a body of the flame holder. 20. The down-fired burner of claim 1, wherein the input and output surfaces of the flame holder are substantially rectangular. 21. The down-fired burner of claim 1, wherein the input and output surfaces of the flame holder are circular, elliptical, or ovular. 22. The down-fired burner of claim 1, wherein a width of the flame holder in a horizontal direction is more than twice as large as a thickness of the flame holder in a vertical direction. 23. A method comprising: heating a flame holder positioned within a combustion volume and having a plurality of perforations each extending from a top surface of the flame holder to a bottom surface of the flame holder, wherein the flame holder is of a refractory material;outputting fuel from a first nozzle in a downward direction onto a top surface of the flame holder;introducing an oxidant into the combustion volume;igniting a combustion reaction of the fuel and oxidant in the plurality of perforations; andcontaining the combustion reaction of the fuel and oxidant substantially in the perforations in the flame holder. 24. The method of claim 23, comprising: measuring a temperature of the flame holder; andoutputting the fuel onto the flame holder after the temperature of the flame holder has reached a threshold temperature. 25. The method of claim 24, wherein the threshold temperature is a temperature at which the flame holder will ignite the combustion reaction within the perforations. 26. The method of claim 23, wherein heating the flame holder comprises applying heat to the flame holder by a preheating mechanism positioned adjacent to the flame holder. 27. The method of claim 23, comprising heating the flame holder by irradiating the flame holder with a laser. 28. The method of claim 23, comprising heating the flame holder with a second fuel nozzle positioned adjacent to the flame holder. 29. The method of claim 23, comprising heating the flame holder by passing a current through an electrical resistor coupled to the flame holder. 30. A method, comprising: heating a flame holder positioned within a combustion volume and having a plurality of perforations each extending from a top surface of the flame holder to a bottom surface of the flame holder;outputting fuel from a first nozzle in a downward direction onto a top surface of the flame holder;introducing an oxidant into the combustion volume;igniting a combustion reaction of the fuel and oxidant in the plurality of perforations;containing the combustion reaction of the fuel and oxidant substantially in the perforations in the flame holder;passing a reactant through a reactor tube positioned adjacent to the flame holder; andcausing a reaction between the reactant and a catalyst in the tube by radiating heat onto the tube from the flame holder. 31. The method of claim 30, wherein the flame holder is positioned between the first and second vertical portions of the tube. 32. The method of claim 31, wherein a connecting portion of the tube connects the first and second vertical portions and is positioned below the flame holder. 33. The method of claim 23, comprising outputting oxygen in a downward direction from a second nozzle onto the top surface of the flame holder. 34. The method of claim 23, wherein introducing the oxidant includes outputting oxygen in an airstream. 35. A method, comprising: heating a flame holder positioned within a combustion volume and having a plurality of perforations each extending from a top surface of the flame holder to a bottom surface of the flame holder;outputting fuel from a first nozzle in a downward direction onto a top surface of the flame holder;introducing an oxidant into the combustion volume;igniting a combustion reaction of the fuel and oxidant in the plurality of perforations; andcontaining the combustion reaction of the fuel and oxidant substantially in the perforations in the flame holder, wherein the combustion reaction is a reaction of the fuel with oxygen. 36. The method of claim 23, wherein the perforations are isolated from each other by a body of the flame holder. 37. A system comprising: a plurality of downward facing fuel nozzles each of which is configured to output a fuel in a downward direction;one or more oxidant sources configured to output oxidant;a plurality of flame holders each of which is positioned below a respective downward facing fuel nozzle, each flame holder including: a top surface;a bottom surface; anda plurality of perforations between the top and bottom surfaces, the flame holders being configured to confine a majority of a combustion reaction of the fuel and oxidant within the perforations, wherein the flame holder is of a refractory material; anda plurality of tubes, each of which is positioned adjacent to a respective flame holder and to output a reaction product of a reaction between a reactant and a catalyst within the tube. 38. The system of claim 37, wherein at least a majority of the tubes are positioned adjacent to four respective flame holders. 39. The system of claim 37, wherein each tube is packed with the catalyst and is configured to receive the reactant in a first vertical portion of the tube to output the reaction products from a second vertical portion of the tube. 40. The system of claim 37, wherein the perforations of each flame holder are isolated from each other. 41. The system of claim 40, wherein each flame holder is configured to convey heat between the plurality of perforations. 42. A system, comprising: a plurality of downward facing fuel nozzles each of which is configured to output a fuel in a downward direction;one or more oxidant sources configured to output oxidant;a plurality of flame holders each of which is positioned below a respective downward facing fuel nozzle, each flame holder including: a top surface;a bottom surface; anda plurality of perforations between the top and bottom surfaces, the flame holders being configured to confine a majority of a combustion reaction of the fuel and oxidant within the perforations;a plurality of tubes, each of which is positioned adjacent to a respective flame holder and to output a reaction product of a reaction between a reactant and a catalyst within the tube; anda plurality of preheating mechanisms each positioned adjacent to a respective flame holder and configured to preheat the respective flame holder to a threshold temperature prior to outputting the fuel from the respective fuel nozzle. 43. The system of claim 42, wherein the threshold temperature is an auto-ignition temperature of the fuel plus an additional temperature elevation selected to prevent initial cooling by fuel and combustion air from lowering the temperature of the flame holder to a temperature below the auto-ignition temperature.