Burner system including a distal flame holder and a non-reactive fluid source

Abstract

A burner includes a distal flame holder, first and second fuel nozzles, a fuel and oxidant source, and a mixing tube disposed upstream from the distal flame holder. Fuel emitted from the first fuel nozzle mixes with oxidant from the oxidant source to form a fuel and oxidant mixture to support combustion in the distal flame holder. A non-reactive fluid source such as recirculated flue gas provides a non-reactive fluid for dilution of the fuel and oxidant mixture to prevent flashback.

What is claimed is: 
     
         1 . A burner system, comprising:
 at least one distal flame holder for disposition in a combustion volume and configured to receive and ignite a fuel and oxidant mixture;   a fuel source configured to contribute a fuel to the fuel and oxidant mixture;   an oxidant source configured to contribute an oxidant to the fuel and oxidant mixture;   a mixing tube disposed in a dilution region between the distal flame holder and an outlet of the fuel source, the mixing tube configured to receive and facilitate mixing of the fuel and the oxidant;   a pilot fuel nozzle disposed proximate the distal flame holder and downstream from a distal end of the mixing tube; and   a non-reactive fluid source configured to deliver a non-reactive fluid in the dilution region while the fuel and the oxidant are contributed into the dilution region by the fuel source and the oxidant source and while the distal flame holder supports a combustion reaction of the fuel and oxidant mixture.   
     
     
         2 . The burner system of  claim 1 , wherein the non-reactive fluid includes flue gas from downstream of the distal flame holder, and
 a flow of at least one of the fuel and oxidant from the fuel source and the oxidant source toward the distal flame holder draws the flue gas into a proximal end of the mixing tube from at least downstream of the distal flame holder along an outer surface of the mixing tube.   
     
     
         3 . The burner system of  claim 1 , wherein the proximal end of the mixing tube includes a flared portion. 
     
     
         4 . The burner system of  claim 3 , wherein the outlet of the fuel source includes one or more main fuel nozzles arranged to deliver the fuel to the proximal end of the mixing tube,
 wherein the pilot fuel nozzle includes a pilot flame holding feature disposed to hold a pilot flame;   wherein the non-reactive fluid source is configured to deliver the non-reactive fluid in a region disposed between the one or more main fuel nozzles and an ignitable portion of the fuel and oxidant mixture.   
     
     
         5 . The burner system of  claim 4 , wherein the non-reactive fluid includes a reactive component; and
 wherein the pilot flame held by the pilot flame holding feature generates at least a portion of the non-reactive fluid in the form of a fuel depleting combustion product.   
     
     
         6 . The burner system of  claim 5 , wherein the non-reactive fluid includes one or more components selected from the group consisting of:
 nitrogen, carbon dioxide, nitrogen oxide, nitrogen dioxide, sulfur oxide, sulfur dioxide, oxygen, and argon.   
     
     
         7 . The burner system of  claim 2 , wherein the non-reactive fluid further comprises combustion reaction products generated by a pilot flame. 
     
     
         8 . The burner system of  claim 1 , wherein
 the fuel source includes:
 a fuel supply configured to store the fuel, and 
 a first fuel nozzle in fluid connection with the fuel supply and positioned to deliver the fuel to the fuel and oxidant mixture; and 
   the non-reactive fluid source includes:
 the pilot fuel nozzle, 
 an intermediate flame holder disposed between the pilot fuel nozzle and the distal flame holder, the intermediate flame holder configured to hold a flame supported by the oxidant and by the fuel, when the fuel is delivered from the pilot fuel nozzle, and 
 an ignition source configured to ignite the fuel and the oxidant at the intermediate flame holder to produce the flame. 
   
     
     
         9 . The burner system of  claim 1 , further comprising:
 a pilot fuel flow control mechanism in fluid connection with the pilot fuel nozzle;   wherein the pilot fuel flow control mechanism is configured to permit a first fuel flow rate to the pilot fuel nozzle during a startup period and is configured to permit a second fuel flow rate to the pilot fuel nozzle after the startup period.   
     
     
         10 . The burner system of  claim 1 , wherein the distal flame holder is a reticulated ceramic distal flame holder. 
     
     
         11 . The burner system of  claim 10 , wherein the distal flame holder includes a plurality of reticulated fibers. 
     
     
         12 . The burner system of  claim 11 , wherein the distal flame holder is configured to support a combustion reaction of the fuel and the oxidant upstream, downstream, and within the distal flame holder. 
     
     
         13 . The burner system of  claim 11 , wherein the distal flame holder includes about 10 pores per inch. 
     
     
         14 . The burner system of  claim 11 , wherein the reticulated fibers are formed as a reticulated ceramic foam. 
     
     
         15 . The burner system of  claim 11 , wherein the reticulated fibers are formed using a reticulated polymer foam as a template. 
     
     
         16 . The burner system of  claim 11 , wherein the distal flame holder includes:
 an input face;   an output face; and   a plurality of perforations extending between the input face and the output face.   
     
     
         17 . The burner system of  claim 16 , wherein the perforations are formed as passages between the reticulated fibers. 
     
     
         18 . The burner system of  claim 17 , wherein the perforations extend between the input face and the output face. 
     
     
         19 . The burner system of  claim 16 , wherein the distal flame holder is configured to support at least a portion of the combustion reaction within the distal flame holder between the input face and the output face. 
     
     
         20 . A burner system, comprising:
 a distal flame holder configured to hold a combustion reaction of a fuel and an oxidant;   an oxidant conduit configured to direct the oxidant toward the distal flame holder;   a first fuel nozzle oriented to direct a first flow of the fuel into a combustion volume for mixture with the oxidant in a dilution region between the first fuel nozzle and the distal flame holder when a temperature of the distal flame holder is above a predetermined temperature;   a mixing tube disposed in the dilution region, and being open between the distal flame holder and the first fuel nozzle; and   a non-reactive fluid source oriented to provide a non-reactive fluid into the mixing tube when the distal flame holder is at an operating temperature.   
     
     
         21 . The burner system of  claim 20 , wherein the non-reactive fluid source comprises:
 a flue gas recirculation path;   wherein flue gas provided by via flue gas recirculation path constitutes at least part of the non-reactive fluid, and the flue gas is educed into a fuel and oxidant stream by the flow of at least the oxidant.   
     
     
         22 . The burner system of  claim 21 , further comprising;
 a pilot fuel nozzle configured to provide pilot fuel for a pilot flame, wherein the flue gas recirculation path includes at least a toroidal volume between the mixing tube and a wall of the combustion volume, and   the flue gas is educed into the fuel and oxidant stream at a proximal opening of the mixing tube for dilution of the fuel and oxidant stream.   
     
     
         23 . The burner system of  claim 22 , wherein the flue gas recirculation path is external to combustion chamber. 
     
     
         24 . The burner system of  claim 23 , further comprising a flue gas flow control mechanism configured to control at least one of a rate of flow and a direction of flow of the recirculated flue gas. 
     
     
         25 . The burner system of  claim 20 , wherein the mixing tube includes a flared portion at the proximal opening. 
     
     
         26 . The burner system of  claim 20 , further comprising;
 a pilot fuel nozzle disposed lateral to the first fuel nozzle; and   an ignition source disposed proximate the pilot fuel nozzle and configured to ignite a mixture of the oxidant and the fuel emitted from the pilot fuel nozzle.   
     
     
         27 . The burner system of  claim 21 , wherein the flue gas is recirculated from downstream of the distal flame holder, the flue gas including combustion products from the distal flame holder. 
     
     
         28 . A method for inhibiting flashback in a burner system, the method comprising:
 supplying an oxidant to a combustion volume;   directing a fuel via a first fuel nozzle to a dilution region of the combustion volume between the first fuel nozzle and a distal flame holder;   mixing the oxidant with the fuel from the first fuel nozzle in a mixing tube disposed in the dilution region and open between the first fuel nozzle and the distal flame holder to provide a mixture of the fuel and the oxidant, the mixing tube configured to receive and facilitate mixing of the fuel and the oxidant; and   providing a non-reactive fluid to the mixture of the fuel and the oxidant in the dilution region.   
     
     
         29 . The method of  claim 28 , wherein said providing the non-reactive fluid to the mixture of the fuel and the oxidant includes emitting a non-reactive gas from a second fuel nozzle into the dilution region. 
     
     
         30 . The method of  claim 29 , wherein the second fuel nozzle is a pilot fuel nozzle disposed proximate the distal flame holder and downstream from a distal end of the mixing tube; and
 said emitting a non-reactive gas from the second fuel nozzle includes the supporting a pilot flame with the pilot fuel nozzle, the non-reactive gas including combustion products of the pilot flame.   
     
     
         31 . The method of  claim 28 , wherein said providing the non-reactive fluid to the mixture of the fuel and the oxidant includes recirculating a flue gas, as the non-reactive fluid, sourced from downstream of the distal flame holder. 
     
     
         32 . The method of  claim 31 , further comprising:
 educing the flue gas into a proximal end of the mixing tube for dilution of the mixture of the fuel and the oxidant.   
     
     
         33 . A multi-stage burner system, comprising:
 a fuel and oxidant source configured to emit fuel and oxidant into a combustion volume;   a distal flame holder oriented to receive and ignite a first mixture of the fuel and the oxidant downstream of the fuel and oxidant source; and   at least one intermediate flame holder disposed between the fuel and oxidant source and the distal flame holder and oriented to receive a second mixture of the fuel and the oxidant.   
     
     
         34 . The multi-stage burner system of  claim 33 , further comprising an ignition source disposed proximate the intermediate flame holder and configured to ignite the second mixture of the fuel and the oxidant, the intermediate flame holder configured to hold a flame resulting from the ignited second mixture of the fuel and the oxidant. 
     
     
         35 . The multi-stage burner system of  claim 33 , wherein the fuel and oxidant source comprises:
 a fuel output configured to emit the fuel for inclusion in at least one of the first mixture of the fuel and the oxidant and the second mixture of the fuel and the oxidant; and   an oxidant output configured to emit the oxidant for inclusion in the first mixture of the fuel and the oxidant and the second mixture of the fuel and the oxidant.   
     
     
         36 . The multi-stage burner system of  claim 33 , wherein the fuel output comprises two or more fuel nozzles each in fluid connection with a fuel supply. 
     
     
         37 . The multi-stage burner system of  claim 36 , wherein at least one of the two or more fuel nozzles is oriented to direct a portion of the fuel toward the at least one intermediate flame holder, and a remaining one or more fuel nozzles are oriented to direct the fuel toward the distal flame holder. 
     
     
         38 . The multi-stage burner system of  claim 37 , further comprising a controller configured to control a rate of the fuel directed by the at least one of the two or more fuel nozzles toward the intermediate flame holder. 
     
     
         39 . The multi-stage burner system of  claim 37 , wherein the intermediate flame holder is oriented to direct thermal energy released by combustion of the fuel and the oxidant at the intermediate flame holder toward the distal flame holder to heat the distal flame holder to a predetermined temperature. 
     
     
         40 . The multi-stage burner system of  claim 37 , wherein the intermediate flame holder is oriented to direct combustion products released by combustion of the fuel and the oxidant at the intermediate flame holder as a non-reactive fluid for dilution of the first mixture of the fuel and the oxidant in a region between the intermediate flame holder and the distal flame holder. 
     
     
         41 . The multi-stage burner system of  claim 33 , wherein the intermediate flame holder comprises an electrode configured to provide an electrical charge to the second mixture of the fuel and the oxidant.