Pilot stabilized burner

Abstract

According to an embodiment, a burner system includes a pilot burner disposed in a furnace at a distal position along a main fuel and combustion air flow axis, and one or more main fuel nozzles disposed at a proximal position along the main fuel and combustion air flow axis. The pilot burner is configured to support a pilot flame and the one or more main fuel nozzles are configured to support a main flame in contact with the pilot flame. The pilot burner is disposed to cause the main fuel and combustion air to be ignited by the pilot flame. The pilot burner may support a diffusion pilot flame or may include a premixing apparatus to support a pre-mixed flame.

1 . A burner system, comprising:
 a pilot burner disposed in a furnace at a distal position along a flow axis of a main fuel and combustion air; and   one or more main fuel nozzles disposed at a proximal position along the flow axis and configured to output a main fuel;   wherein the pilot burner is configured to support a pilot flame; and   wherein the one or more main fuel nozzles are configured to support a main flame in contact with the pilot flame;   wherein the pilot burner is disposed to cause the main fuel and combustion air to be ignited by the pilot flame.   
     
     
         2 . The burner system of  claim 1 , wherein the main flame comprises a flame having a heat output of at least 10 times the heat output of the pilot flame when the burner system is operating at a rated heat output. 
     
     
         3 . The burner system of  claim 2 , wherein operating at the rated heat output corresponds to operating in a steady state standard operating mode. 
     
     
         4 . The burner system of  claim 2 , wherein the main flame comprises a flame having a heat output of at least 20 times the heat output of the pilot flame when the burner system is operating at a rated heat output. 
     
     
         5 . The burner system of  claim 1 , further comprising a stack operatively coupled to the burner system, wherein the burner system has a NOx output of about twenty parts per million or less, adjusted to 3% excess O 2  at the stack. 
     
     
         6 . (canceled) 
     
     
         7 . (canceled) 
     
     
         8 . The burner system of  claim 1 , wherein the pilot burner defines a plurality of fuel orifices having a sufficiently large collective area to collectively support a low momentum pilot flame. 
     
     
         9 . (canceled) 
     
     
         10 . (canceled) 
     
     
         11 . (canceled) 
     
     
         12 . The burner system of  claim 1 , wherein the pilot burner comprises a fuel manifold having a plurality of segments joined together, each segment having a plurality of fuel orifices configured to pass fuel from inside the fuel manifold to a furnace combustion volume. 
     
     
         13 . The burner system of  claim 12 , wherein the plurality of segments are formed as respective tubes configured to freely pass the fuel delivered from a fuel pipe into the fuel manifold. 
     
     
         14 . The burner system of  claim 13 , wherein at least a portion of the tubes is arranged as spokes radiating from a center disposed substantially at a centerline along the axis. 
     
     
         15 . (canceled) 
     
     
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         17 . (canceled) 
     
     
         18 . (canceled) 
     
     
         19 . (canceled) 
     
     
         20 . The burner system of  claim 1 , wherein the pilot burner supports a diffusion flame at the distal location at least 100 main fuel nozzle diameters from the floor of the furnace. 
     
     
         21 . (canceled) 
     
     
         22 . The burner system of  claim 1 , wherein the pilot burner includes at least one tube disposed transverse to the fuel and combustion air flow axis. 
     
     
         23 . The burner system of  claim 22 , further comprising:
 one or more sections of reticulated ceramic disposed superjacent to the at least one tube.   
     
     
         24 . (canceled) 
     
     
         25 . (canceled) 
     
     
         26 . The burner system of  claim 1 , further comprising:
 a distal flame holder disposed at a third position along the fuel and combustion air flow axis, more distal from the main fuel nozzles than the pilot burner.   
     
     
         27 . The burner system of  claim 26 , wherein the distal flame holder comprises a perforated flame holder. 
     
     
         28 . The burner system of  claim 1 , wherein the pilot burner is a pre-mix burner configured to support the pilot flame using a pre-mixture of a pilot fuel and an oxidant. 
     
     
         29 . The burner system of  claim 28 , wherein the pilot burner includes:
 a pilot pre-mix chamber;   a pilot fuel line fitting configured to output the pilot fuel into the pilot pre-mix chamber;   a pilot oxidant channel configured to output oxidant into the pilot pre-mix chamber; and   a pilot pre-mixture nozzle arranged to receive the pre-mixture of pilot fuel and oxidant from the pilot pre-mix chamber and output the pre-mixture of pilot fuel and oxidant into the furnace to support the pilot flame;   wherein the pilot pre-mix chamber, the pilot fuel line fitting, and the pilot oxidant channel are arranged to cause mixing of the pilot oxidant with the pilot fuel in the pilot pre-mix chamber to produce the pre-mixture of pilot fuel and oxidant   
     
     
         30 . (canceled) 
     
     
         31 . The burner system according to  claim 29 , wherein the pilot burner further includes a flame arrestor disposed to cause the pre-mixture of pilot fuel and oxidant to flow through the flame arrestor as the pre-mixture of pilot fuel and oxidant flows from the pilot pre-mix chamber through the pilot pre-mixture nozzle. 
     
     
         32 . (canceled) 
     
     
         33 . (canceled) 
     
     
         34 . The burner system according to  claim 29 , wherein the pilot pre-mix chamber is disposed closer to the proximal position than to the distal position;
 wherein the pilot pre-mix chamber comprises a pre-mixture pipe arranged to deliver the pre-mixture of the pilot fuel and oxidant from the pilot fuel line and pilot oxidant channel to a pilot burner distal assembly disposed adjacent to the distal position; and   wherein the pilot burner distal assembly includes a flame arrestor arranged to pass the pre-mixture of the pilot fuel and oxidant from the pre-mixture pipe to the pilot pre-mixture nozzle and to prevent a flash-back of combustion from the pilot pre-mixture nozzle into the pilot pre-mixture pipe.   
     
     
         35 . (canceled) 
     
     
         36 . (canceled) 
     
     
         37 . The burner system according to  claim 34 , wherein the pilot burner distal assembly includes the pilot pre-mixture nozzle; and
 wherein the pre-mixture pipe is configured to transmit the pilot fuel, the oxidant, and the pre-mixture thereof at a sufficiently high flow rate to cause a flow velocity to exceed a flame speed of the fuel and oxidant pre-mixture to prevent a flash-back of combustion into or through the pre-mixture pipe.   
     
     
         38 . The burner system according to  claim 28 , further comprising:
 a pilot igniter configured to ignite the pre-mixture of the pilot fuel and oxidant after the pre-mixture of the pilot fuel and oxidant is emitted from the pilot pre-mixture nozzle.   
     
     
         39 . (canceled) 
     
     
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         45 . (canceled) 
     
     
         46 . (canceled) 
     
     
         47 . (canceled) 
     
     
         48 . The burner system of  claim 27 , wherein the perforated flame holder comprises perforations formed as passages between the reticulated fibers or in a reticulated ceramic foam. 
     
     
         49 . A method for operating a burner system, comprising:
 providing heat to a distal flame holder from a pilot flame supported by a pilot burner, the pilot flame being fueled by a pilot fuel, the distal flame holder and the pilot burner being disposed in a furnace and in proximity to one another, the pilot burner disposed between the distal flame holder and one or more main fuel nozzles, a distance between the pilot burner and the distal flame holder being smaller than a distance between the pilot burner and the one or more main fuel nozzles;   introducing mixed main fuel and air to the distal flame holder; and   holding at least a portion of a combustion reaction of the mixed main fuel and air with the distal flame holder while the pilot burner continues to support the pilot flame.   
     
     
         50 . (canceled) 
     
     
         51 . The method of  claim 49 , further comprising:
 measuring a temperature of the distal flame holder; and   when the temperature of the distal flame holder is at or above a predetermined threshold, reducing a pilot fuel rate of flow to reduce a size of the pilot flame;   wherein reducing the size of the pilot flame relative to the size of the combustion reaction of the mixed main fuel and air causes a reduction of emissions of oxides of nitrogen.   
     
     
         52 . The method of  claim 49 , wherein introducing mixed main fuel and air to the distal flame holder includes introducing, at a proximal end of a mixing tube, the main fuel via the one or more main fuel nozzles and the air;
 wherein the proximal end of the mixing tube is disposed proximate to the one or more main fuel nozzles, and a distal end of the mixing tube is disposed proximate to the distal flame holder, the mixing tube being open from the proximal end to the distal end.   
     
     
         53 . The method of  claim 52 , further comprising:
 educing a flue gas into the proximal end of the mixing tube.   
     
     
         54 . The method of  claim 52 , wherein the pilot burner is disposed between the distal flame holder and the distal end of the mixing tube. 
     
     
         55 . (canceled) 
     
     
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         64 . The method of  claim 51 , further comprising:
 detecting the combusting of the main fuel at the distal flame holder using an electrocapacitive sensor, the electrocapacitive sensor configured to output sensor signals to a controller.   
     
     
         65 . The burner system according to  claim 1 , further comprising:
 a distal flame holder positioned in the furnace in a position to be preheated by the pilot flame during a preheating state and to hold a combustion reaction of the main fuel and oxidant adjacent to the distal flame holder during a standard operating state;   a pilot flame sensor configured to sense a condition of the pilot flame and to output a sensor signal indicative of the condition of the pilot flame;   a combustion sensor configured to sense a condition of the distal flame holder and to generate a sensor signal indicative of the condition of the distal flame holder;   one or more actuators configured to adjust a flow of the main fuel from the one or more main fuel nozzles, to adjust a flow of pilot fuel to the pilot burner, and to adjust a flow of oxidant from an oxidant source; and   a controller communicatively coupled to the actuators and the combustion sensor, the controller being configured to receive the sensor signal from the combustion sensor and to control the actuators to adjust the flow of the pilot fuel, the main fuel, and the oxidant responsive to the sensor signal and in accordance with software instructions stored in a non-transitory computer readable medium coupled to the controller.   
     
     
         66 . (canceled) 
     
     
         67 . (canceled) 
     
     
         68 . The burner system according to  claim 65 , wherein the pilot flame sensor includes at least one of an electrocapacitive sensor, an electro resistive sensor, and a tomographic sensor. 
     
     
         69 . (canceled) 
     
     
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         73 . The burner system according to  claim 65 , wherein the controller is configured to adjust a size of the pilot flame in response to the sensor signals from at least the combustion sensor by controlling one or more of the actuators to adjust the flow of the pilot fuel or the oxidant. 
     
     
         74 . (canceled) 
     
     
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         77 . The burner system according to  claim 68 , wherein the electrocapacitive sensor includes:
 a first set of electrodes positioned laterally around the distal flame holder and configured to sense a parameter in a vicinity of the distal flame holder.   
     
     
         78 . The combustion system of  claim 77 , wherein the electrocapacitive sensor includes:
 a second set of electrodes positioned upstream from the distal flame holder and configured to sense a parameter upstream from the distal flame holder.   
     
     
         79 . (canceled) 
     
     
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         82 . The burner system according to  claim 68 , wherein the electrocapacitive sensor includes a plurality of electrodes positioned laterally around the distal flame holder, and wherein
 the plurality of electrodes include one or more pairs of electrodes each separated from each other by the distal flame holder.   
     
     
         83 . (canceled) 
     
     
         84 . The burner system according to  claim 82 , wherein the electrocapacitive sensor generates electrocapacitive tomography images based on a capacitance between the one or more pairs of electrodes. 
     
     
         85 . The burner system according to  claim 82 , wherein at least one of the pairs of electrodes is separated by the distal flame holder and disposed opposite each other in a first orientation substantially perpendicular to a primary direction of a flow of the main fuel toward the distal flame holder. 
     
     
         86 . (canceled) 
     
     
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         89 . (canceled) 
     
     
         90 . A low emissions modular burner system, comprising:
 one or more burner modules, each burner module including:
 a main fuel source, separately valved from all other fuel sources, configured to selectively deliver a main fuel stream for dilution by a flow of combustion air, 
 a main fuel igniter configured to cause ignition of the main fuel stream emitted from the main fuel source, 
 a distal flame holder, separated from the main fuel source and the main fuel igniter by respective non-zero distances, the distal flame holder being configured to hold a combustion reaction supported by the main fuel stream when the distal flame holder is at or above a predetermined temperature, and 
 a pre-heating apparatus configured to pre-heat the distal flame holder to the predetermined temperature; 
   a common combustion air source configured to provide combustion air to each of the plurality of burner modules; and   a wall encircling all of the one or more burner modules, the wall being configured to laterally contain combustion fluids corresponding to the one or more burner modules.   
     
     
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         96 . The low emissions modular burner system of  claim 90 , further comprising:
 one or more separate main fuel valves, each including a separate main fuel valve actuator configured to operate responsive to receiving control signals; and   a control system configured to output respective control signals to each of the separate valve actuators;   wherein the control system further comprises:
 an interface between the control system and an input channel, 
   wherein the interface is configured to receive a signal corresponding to a burner capacity requirement;
 one or more burner module sensor inputs, each of the one or more burner module sensor inputs being configured to receive a signal corresponding to a burner module status wherein the burner module status is provided by sensor hardware; 
 a microcontroller, a computer readable memory, and a module sequencer configured to select a subset of the one or more burner modules for ignition; and 
 a respective one or more main fuel valve driver outputs each operatively coupled to one of the separate main fuel valve actuators. 
   
     
     
         97 . (canceled) 
     
     
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         100 . The low emissions modular burner system of  claim 96 , wherein the microcontroller is configured to read and execute computer executable instructions, supported by a non-transitory computer readable memory, to:
 receive capacity input data corresponding to the burner capacity requirement signal;   read module status sensor data from one or more sensors corresponding to at least one burner module to verify that a selected one or more of the burner modules is ready for firing;   select the subset of the one or more burner modules for firing; and   drive at least one of the separate main fuel valve actuators corresponding to the selected subset of the one or more burner modules to open so as to provide fuel to a combustion reaction supported by the subset of the one or more burner modules.   
     
     
         101 . (canceled) 
     
     
         102 . The low emissions modular burner system of  claim 90 , wherein the pre-heating apparatus comprises:
 a pilot fuel source configured to provide a pilot fuel,   a pilot fuel igniter configured to ignite a flow of the pilot fuel, and   a distal pilot configured to hold a pilot flame supported by the pilot fuel, a pilot fuel source flow rate being selected to provide a pilot flame sized to raise the distal flame holder temperature to the pre-determined temperature.   
     
     
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         115 . The low emissions modular burner system of  claim 90 , wherein at least one of the burner modules is configured to be freestanding, supported only by a coupling at a combustion air inlet. 
     
     
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