WO2020227581A1 - Brûleur pilote stabilisé - Google Patents

Brûleur pilote stabilisé Download PDF

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Publication number
WO2020227581A1
WO2020227581A1 PCT/US2020/031966 US2020031966W WO2020227581A1 WO 2020227581 A1 WO2020227581 A1 WO 2020227581A1 US 2020031966 W US2020031966 W US 2020031966W WO 2020227581 A1 WO2020227581 A1 WO 2020227581A1
Authority
WO
WIPO (PCT)
Prior art keywords
pilot
burner
fuel
distal
flame holder
Prior art date
Application number
PCT/US2020/031966
Other languages
English (en)
Inventor
Colin James Deller
Donald Kendrick
Venkatesh Iyer
Douglas W. KARKOW
James K. DANSIE
Christopher A. Wiklof
Original Assignee
Clearsign Technologies Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US16/782,861 external-priority patent/US20210239317A1/en
Application filed by Clearsign Technologies Corporation filed Critical Clearsign Technologies Corporation
Priority to CN202080034369.8A priority Critical patent/CN113795713A/zh
Priority to EP20803052.8A priority patent/EP3966503A4/fr
Publication of WO2020227581A1 publication Critical patent/WO2020227581A1/fr
Priority to US17/521,722 priority patent/US20220205633A1/en

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
    • F23D14/20—Non-premix gas burners, i.e. in which gaseous fuel is mixed with combustion air on arrival at the combustion zone
    • F23D14/22—Non-premix gas burners, i.e. in which gaseous fuel is mixed with combustion air on arrival at the combustion zone with separate air and gas feed ducts, e.g. with ducts running parallel or crossing each other
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
    • F23N5/10—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using thermocouples
    • F23N5/105—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using thermocouples using electrical or electromechanical means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D11/00—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space
    • F23D11/36—Details, e.g. burner cooling means, noise reduction means
    • F23D11/40—Mixing tubes or chambers; Burner heads
    • F23D11/406—Flame stabilising means, e.g. flame holders
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
    • F23D14/02—Premix gas burners, i.e. in which gaseous fuel is mixed with combustion air upstream of the combustion zone
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
    • F23D14/26—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid with provision for a retention flame
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
    • F23D14/46—Details, e.g. noise reduction means
    • F23D14/48—Nozzles
    • F23D14/58—Nozzles characterised by the shape or arrangement of the outlet or outlets from the nozzle, e.g. of annular configuration
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
    • F23D14/46—Details, e.g. noise reduction means
    • F23D14/62—Mixing devices; Mixing tubes
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N1/00—Regulating fuel supply
    • F23N1/002—Regulating fuel supply using electronic means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N3/00—Regulating air supply or draught
    • F23N3/005—Regulating air supply or draught using electrical or electromechanical means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D2900/00—Special features of, or arrangements for burners using fluid fuels or solid fuels suspended in a carrier gas
    • F23D2900/00014—Pilot burners specially adapted for ignition of main burners in furnaces or gas turbines

Definitions

  • 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.
  • a burner system includes a main fuel source disposed at a proximal position along a flow axis of a furnace, a pilot burner disposed at an intermediate distance along the flow axis, and a distal flame holder disposed at a distal position along the flow axis.
  • the pilot burner is configured to support a pilot flame to heat the distal flame holder.
  • the main fuel source is configured to provide main fuel to the distal flame holder after the distal flame holder is at least partially heated.
  • the distal flame holder is configured to hold at least a portion of a combustion reaction supported by the main fuel.
  • a method for operating a burner system includes providing heat to the 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 are 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 with 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.
  • the method for operating a burner system includes introducing mixed 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.
  • a method for operating a burner system includes supporting a diffusion flame across a portion of a width of a furnace volume at a position distal from a furnace floor, providing combustion air to the furnace volume from a location near the furnace floor, outputting a high pressure main fuel jet from each of one or more main fuel nozzles at one or more locations near the furnace floor, mixing the main fuel with the combustion air while the main fuel and combustion air travel from the locations near the furnace floor to the distal position, combusting the main fuel to produce a main flame by exposing the mixed main fuel and air to the diffusion flame.
  • the main flame is held by a distal flame holder more distal from the furnace floor than the diffusion flame.
  • a combustion system includes an oxidant source configured to output an oxidant into a furnace volume, a pilot burner configured to support a pilot flame by outputting a pilot fuel to support a pilot diffusion flame at least during a preheating state, and a main fuel nozzle configured to output a main fuel into the furnace volume from a proximal position during a standard operating state at least after the preheating state is complete.
  • the combustion system includes a distal flame holder positioned in the furnace volume to be preheated by the pilot flame during the preheating state and to hold a combustion reaction of the main fuel and oxidant adjacent to the distal flame holder during the standard operating state.
  • the combustion system includes a combustion sensor configured to sense a condition of the combustion system and to generate a sensor signal indicative of the condition of the combustion system, and one or more actuators configured to adjust a flow of the main fuel from the main fuel nozzle, to adjust a flow of the pilot fuel to the pilot burner, and to adjust a flow of the oxidant from the oxidant source.
  • the combustion system includes a controller communicatively coupled to the actuators and the
  • the controller being configured to receive the sensor signals 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 signals and in accordance with software instructions stored in a non-transitory computer readable medium coupled to the controller.
  • a computing system implemented method for operating a combustion system includes receiving, during a preheating state of a combustion system, sensor signals from a pilot flame sensor indicating a condition of a pilot flame in a furnace volume supported by a flow of pilot fuel and an oxidant, and receiving, during the preheating state, sensor signals from a distal flame holder sensor indicating a temperature of a distal flame holder positioned in the furnace volume to be preheated to an operating temperature by the pilot flame during the preheating state.
  • the method includes outputting control signals to control one or more actuators to adjust the flow of the pilot fuel, to adjust the flow of the oxidant, or to generate an arc to ignite the pilot flame responsive to the sensor signals from the pilot flame sensor and in accordance with software instructions stored on a non-transitory computer readable medium, and outputting control signals to control one or more actuators to transition the combustion system from the preheating state to a standard operating state if the sensor signals from the distal flame holder sensor indicate that the distal flame holder has reached the operating temperature, the standard operating state corresponding to supporting a combustion reaction of a main fuel and the oxidant in the distal flame holder and in accordance with the software instructions stored on the non-transitory computer readable medium.
  • the method includes receiving sensor signals from the distal flame holder sensor during the standard operating state indicating a condition of the distal flame holder, and outputting control signals to control one or more actuators to adjust a flow of the main fuel or to adjust the flow of the oxidant responsive to the sensor signals from the distal flame holder sensor during the standard operating state and in accordance with the software instructions stored on the non-transitory computer readable medium.
  • a low emissions modular burner system includes on or more burner modules.
  • Each burner module includes 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.
  • the low emissions modular burner system includes 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.
  • a burner includes a housing having a combustion air inlet at a base, and a burner module positioned inside the housing.
  • the burner module includes an inlet configured to be coupled to a main fuel supply and to receive combustion air via the housing, a distal flame holder positioned inside the housing, and a main nozzle configured to receive a flow of main fuel from the inlet, and to emit a main fuel stream toward the distal flame holder.
  • a burner system includes 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 main fuel nozzle oriented to direct a flow of a main fuel into a combustion volume for mixture with the oxidant in a dilution region between the main fuel nozzle and the distal flame holder when a temperature of the distal flame holder is above a predetermined temperature, and a mixing tube disposed in the dilution region, and being open from a mixing tube inlet to a mixing tube outlet between the main fuel nozzle and the distal flame holder, the mixing tube being formed to cause flow of the oxidant and fuel to educe flue gas into the mixing tube for mixing with fuel and oxidant.
  • FIG. 1 A is a block diagram of a burner system, according to an
  • FIG. 1 B is a block diagram of a burner system including a distal flame holder, according to an embodiment.
  • FIG. 2A is an illustration of a burner system, according to an embodiment.
  • FIG. 2B is an illustration of a burner system including a distal flame holder, according to an embodiment.
  • FIG. 3 is a perspective view of a combustion system, according to an embodiment.
  • FIG. 4 is an illustration of a pilot burner in the shape of an H, according to an embodiment.
  • FIG. 5 is an illustration of a pilot burner in the shape of a spiral, according to an embodiment.
  • FIG. 6 is an illustration of a pilot burner in the shape of a hexagon, according to an embodiment.
  • FIG. 7 is a simplified diagram of a combustion system including a distal flame holder configured to hold a combustion reaction wherein the distal flame holder includes a perforated flame holder, according to an embodiment.
  • FIG. 8 is a side sectional diagram of a portion of the perforated flame holder of FIG. 7, according to an embodiment.
  • FIG. 9 is a flow chart showing a method for operating a burner system including the distal flame holder shown and described herein, according to an embodiment.
  • FIG. 10A is a simplified perspective view of a combustion system, including a reticulated ceramic perforated flame holder configured to hold a combustion reaction, according to an embodiment.
  • FIG. 10B is a simplified side sectional diagram of a portion of the reticulated ceramic perforated flame holder of FIG. 10A, according to an embodiment.
  • FIG. 11 is a flow chart showing a method for operating a burner system, according to an embodiment.
  • FIG. 12 is a flow chart showing a method for operating a burner system, according to an embodiment.
  • FIG. 13A is a diagram of a combustion system including a distal flame holder and an electrocapacitive combustion sensor, according to an embodiment.
  • FIG. 13B is a top view of the distal flame holder and an electrocapacitive combustion sensor, according to an embodiment.
  • FIG. 14 is a diagram of an arrangement for each of a plurality of burner modules, according to an embodiment.
  • FIG. 15 is a diagram of a control circuit for use in the control system of FIG. 14, according to an embodiment.
  • FIG. 16 is a block diagram of a burner system, according to an
  • FIG. 17 is an illustration of a burner system, according to an embodiment.
  • FIG. 18 is an illustration showing a horizontally-fired burner system including a distal pilot burner and a mixing tube, according to an embodiment.
  • FIG. 1A is a block diagram of a burner system 100, according to an embodiment.
  • the burner system 100 includes a pilot burner 104 and one or more main fuel nozzles 106.
  • 106 are disposed in a furnace volume 101.
  • the pilot burner 104 is disposed in a furnace 101 at a distal position along a main fuel and combustion air flow axis A.
  • the one or more main fuel nozzles 106 are disposed at a proximal position along the main fuel and combustion air flow axis A.
  • the pilot burner 104 is configured to support a pilot flame 108.
  • the pilot flame 108 helps to ignite and/or sustain a main combustion reaction 110.
  • the pilot burner 104 supports the pilot flame 108 by outputting a pilot fuel 112.
  • the pilot flame 108 is supported by the pilot fuel 112 and combustion air introduced into the furnace volume 101. Accordingly, the pilot flame 108 is a combustion reaction of the pilot fuel 112 and combustion air.
  • the one or more main fuel nozzles 106 are configured to support the main flame 110 within the furnace volume 101.
  • the main flame 110 is supported downstream from the pilot flame 108.
  • the main fuel nozzles 106 support the main flame 110 by outputting main fuel 114 into the furnace volume 101.
  • the main flame 110 is supported by the main fuel 114 and combustion air introduced into the furnace volume 101. Accordingly, the main flame 110 is a combustion reaction of the main fuel 114 and the combustion air.
  • the pilot burner 104 and the one or more main fuel nozzles 106 are configured to simultaneously support the main flame 110 in contact with the pilot flame 108.
  • the pilot burner 104 is disposed to cause the main fuel and combustion air to be ignited by the pilot flame 108.
  • the main flame 110 may not be in contact with the pilot flame 108. Instead, the main flame 110 may be separated from the pilot flame 108 away by a gap.
  • the pilot burner 104 includes a plurality of tubes or arms that extend laterally from the axis A.
  • the tubes or arms include a plurality of orifices that output the pilot fuel. Accordingly, the pilot flame 108 is held above each of the tubes, arms, or segments of the pilot burner 104.
  • the shape of the pilot burner 104 can be selected to cover a lateral area corresponding to the area above the main fuel nozzles 106, or an area through which the main fuel 114 passes.
  • the main fuel 114 passes through gaps or open spaces between the laterally extending portions of the pilot burner 104.
  • the main fuel 114 may be initially ignited by the pilot flame 108 as the main fuel 114 passes adjacent to the pilot flame 108. After the main fuel 114 has been ignited, thereby generating the main flame 110, the main flame 110 can be supported in a steady state by the main fuel 114.
  • the laterally extending arms of the pilot burner 104 form a star shape. Additionally or alternatively, the pilot burner 104 can form a spiral shape, a circle shape, an H shape, a square shape, a hexagon shape, or other shapes that cover a desired lateral distance while including gaps through which the main fuel 114 can pass. (See, e.g., FIGS. 2A-6.) In one embodiment, the pilot burner 104 includes a pilot fuel manifold.
  • the pilot fuel manifold includes laterally extending tubes, segments, arms, or portions.
  • the pilot fuel 112 is output from orifices positioned in the laterally extending tubes, segments, arms, or portions of the pilot fuel manifold.
  • the main flame 110 includes a flame having a heat output of at least 10 times the heat output of the pilot flame 108 when the burner system 100 is operating at a rated heat output. In one embodiment, operating at a rated heat output corresponds to operating in a steady state standard operating mode of the burner system 100. In another embodiment, the main flame 110 includes a flame having a heat output of at least 20 times the heat output of the pilot flame 108 when the burner system 100 is operating at a rated heat output.
  • the burner system 100 has a NOx output of about twenty parts per million or less, adjusted to 3% excess O2 at a stack operatively coupled to the burner system 100. In one embodiment, the burner system 100 has a NOx output of about twenty parts per million or less, adjusted to 3% excess O2 at an exhaust stack operatively coupled to the burner system 100.
  • FIG. 1 B is a block diagram of a burner system 111 including a distal flame holder 102, according to an embodiment.
  • the burner system 111 of FIG. 1B is substantially similar to the burner system 100 of FIG. 1 A, except that the burner system 111 includes the distal flame holder 102.
  • the burner system 111 includes a main fuel source 106 disposed at a proximal position along a flow axis A of a furnace volume 101 , a pilot burner 104 disposed at an intermediate distance along the flow axis A, and a distal flame holder 102 disposed at a distal position along the flow axis A.
  • the pilot burner 104 may be configured to support a pilot flame 108 to heat the distal flame holder 102.
  • the main fuel source 106 may be configured to provide main fuel 114 to the distal flame holder 102 after the distal flame holder 102 is at least partially heated.
  • the distal flame holder 102 may be configured to hold at least a portion of the main flame 110 supported by the main fuel 114.
  • the distal flame holder 102 is a perforated flame holder.
  • the operation and structure of the perforated flame holder are described with more particularity in relation to FIGS. 7-10B.
  • the distal flame holder 102 may include one or more solid bluff body flame holders, or may include a mixture of one or more perforated flame holders and one or more bluff body flame holders.
  • FIG. 2A is an illustration of a burner system 200, according to an embodiment.
  • the burner system 200 includes a pilot burner 104 and main fuel nozzles 106.
  • the pilot burner 104 is support the pilot flame 108 by outputting the pilot fuel 112.
  • the main fuel nozzles 106 are configured to support the main flame 110 by outputting the main fuel 114.
  • the pilot burner 104 is supported by and receives fuel via a fuel pipe 220.
  • the fuel pipe 220 extends into the furnace volume 101 via an opening 240 in a floor 238 of the furnace.
  • a stiffener 222 can be positioned around the fuel pipe 220 to prevent the fuel pipe 220 from
  • the main fuel nozzles 106 also extend through the opening 240 in the floor 238.
  • the main fuel nozzles 106 can be supported by fuel risers 224.
  • the main fuel nozzles 106 include orifices that output the main fuel 114 with a 2° spread.
  • the pilot burner 104 defines a plurality of fuel orifices 218 having a sufficiently large collective area to collectively support a low momentum pilot flame 108.
  • the main fuel 114, output by the main fuel nozzles 106 and combustion air form a combustible mixture that expands in breadth as it flows from the proximal position of the main fuel nozzles 106 to the distal position of the pilot burner 104.
  • the plurality of fuel orifices 218 may be disposed across the furnace volume 101 sufficiently broadly to cause contact of the pilot flame 108 with the main fuel 114 and combustion air mixture across the breadth of the combustible mixture.
  • the main fuel nozzles 106 are configured to output fuel in co-flow with the air.
  • the pilot burner 104 includes a fuel manifold having a plurality of segments 219 joined together, each segment 219 having a plurality of fuel orifices 218 configured to pass fuel from inside the fuel manifold to the furnace volume 101.
  • the plurality of segments 219 may be formed as respective tubes configured to freely pass the fuel delivered from the fuel pipe 220 into the fuel manifold.
  • at least a portion of the tubes is arranged as spokes radiating from a center disposed substantially at a centerline along the axis.
  • at least a portion of the tubes may be arranged as an“X”, a rectangle, an ⁇ ”, a wagon wheel, or a star.
  • the pilot burner 104 includes a manifold including a curvilinear tube.
  • the curvilinear tube is arranged as a spiral,
  • the main fuel nozzles 106 form a main fuel dump plane at the proximal location coincident with or near the floor 238 of the furnace.
  • the pilot burner 104 supports a diffusion flame at the distal location at least 100 main fuel nozzle 106 diameters from the floor 238 of the furnace.
  • the pilot burner 104 includes at least one tube disposed transverse to the fuel and combustion air flow axis A.
  • the at least one tube may include opposed vertical tabs extending upward from the at least one tube to form a“U” channel.
  • the burner system 200 includes a pilot fuel source 230.
  • the pilot fuel source 230 supplies the pilot fuel 112 into the fuel pipe 220.
  • the pilot fuel 112 is output from the pilot burner 104 via the fuel orifices 218.
  • a pilot fuel control valve 234 can be manually or electronically controlled to enable or shut off the flow of pilot fuel 112 from the pilot fuel source 230 to the pilot burner 104.
  • the burner system 200 includes a main fuel source 232.
  • the main fuel source 232 supplies the main fuel 114 to the main fuel nozzles 106.
  • the main fuel 114 can be supplied to the main fuel nozzles 106 via the fuel risers 224.
  • a main fuel control valve 236 can be manually or electronically controlled to enable or shut off the flow of the main fuel 114 from the main fuel source 232 to the main fuel nozzles 106.
  • the main fuel source 232 and the pilot fuel source 230 may be a single fuel source or reservoir, fuel of which may be respectively directed to the pilot burner 104 and the main fuel nozzle(s) 106 and separately controllable via, e.g., the pilot fuel control valve 234 and the main fuel control valve 236.
  • combustion air is provided into the furnace volume 101 as natural draft flow through the opening 240 in the floor 238 of the furnace. Additionally or alternatively, the combustion air can be provided into the furnace volume 101 in ways other than through the opening 240 in the floor 238.
  • combustion air may include recirculated flue gas(es), as discussed in more detail below.
  • the combustion air may include forced draft from a blower (not shown).
  • FIG. 2B is an illustration of a burner system 211 including a distal flame holder 102, according to an embodiment.
  • the burner system 211 is substantially similar to the burner system 200 of FIG. 2A, except that the burner system 211 includes a distal flame holder 102 positioned above the pilot burner 104, i.e. , disposed at a position further distal from the main fuel nozzles 106 than the pilot burner 104. While the pilot burner supports the pilot flame 108 (see FIG. 1A and FIG. 1 B), the distal flame holder 102 holds the main flame 110 (see FIG. 1 B).
  • the pilot flame 108 can ignite and stabilize the main flame 110.
  • the distal flame holder 102 may include a perforated flame holder configured to hold the secondary flame 110 and to control the length of the secondary flame 110. Such perforated flame holder 102 can hold at least a portion of the secondary flame 110 within the perforated flame holder 102.
  • FIG. 3 is a perspective view of a combustion system 300, according to an embodiment.
  • the burner system 300 includes a pilot burner 104 and main fuel nozzles 106. Though not shown in FIG. 3, the pilot burner 104 is configured to support the pilot diffusion flame 108 by outputting the pilot fuel 112 through low velocity orifices. Though not shown in FIG. 3, the main fuel nozzles 106 are configured to support the main flame 110 by outputting the main fuel 114 as one or more high velocity streams or“jets”.
  • the pilot burner 104 is supported by and receives the pilot fuel 112 via a fuel pipe 220.
  • the fuel pipe 220 extends into the furnace volume 101 via an opening 240 in a floor 238 of the furnace.
  • a stiffener 222 can be positioned around the fuel pipe 220 to prevent the fuel pipe 220 from wobbling.
  • the main fuel nozzles 106 also extend through the opening 240 in the floor 238.
  • the main fuel nozzles 106 can be supported by fuel risers 224.
  • the main fuel nozzles 106 include orifices that output the main fuel with about a 2° spread.
  • the pilot burner 104 includes a fuel manifold having a plurality of segments 219 joined together, each segment 219 having a plurality of fuel orifices (e.g., fuel orifices 218 in FIGS 2A, 2B) configured to pass fuel from inside the fuel manifold to the furnace volume 101.
  • the plurality of segments 219 may be formed as respective tubes configured to freely pass the fuel delivered from the fuel pipe 220 into the fuel manifold.
  • at least a portion of the tubes is arranged as spokes radiating from a center disposed substantially at a centerline along the axis. In the embodiment of FIG.
  • the plurality of segments 219 are arranged in an“X” shape.
  • each segment 219 includes one or more sections of reticulated ceramic 226 disposed in and supported by a“U” channel in the segments 219.
  • the pilot fuel 112 can flow from the fuel orifices 218 into the channels or passageways of the one or more sections of reticulated ceramic 226.
  • the pilot flame 108 can be held at least partially within the channels or
  • the one or more sections of reticulated ceramic 226 are disposed superjacent to at least one tube of the tubes forming the plurality of segments 219.
  • the at least one tube may define a plurality of fuel flow apertures disposed along a length of the at least one tube.
  • the at least one tube defines a plurality of fuel flow apertures configured to allow gaseous pilot fuel 112 to flow upward into a“U” channel formed superjacent to the at least one tube.
  • the burner system 300 includes support legs 252.
  • the support legs 252 can support a distal flame holder 102 (not shown in FIG. 3), including a solid bluff body and/or perforated flame holder, in the furnace volume 101 above the pilot burner 104.
  • the distal flame holder can hold a portion of the main flame 110.
  • FIG. 4 is an illustration of a pilot burner 104 in the shape of an H, according to an embodiment.
  • the pilot burner 104 includes a plurality of fuel orifices 218 that can output the pilot fuel 112.
  • the pilot burner 104 can be made up of a plurality of tubes segment joined together to form the“H” shape.
  • FIG. 5 is an illustration of a pilot burner 104 in the shape of a spiral, according to an embodiment.
  • the pilot burner 104 includes a plurality of fuel orifices 218 that can output the pilot fuel 112.
  • the pilot burner 104 can be made up of a plurality of tubes segment joined together to form the spiral shape.
  • FIG. 6 is an illustration of a pilot burner 104 in the shape of a hexagon with sides attached to a center hub, according to an embodiment.
  • the pilot burner 104 includes a plurality of fuel orifices 218 that can output the pilot fuel 112.
  • the pilot burner 104 can be made up of a plurality of tubes segment joined together to form the shape shown in FIG. 6.
  • FIG. 7 is a simplified diagram of a combustion system 700 including a distal flame holder 102 configured to hold a combustion reaction wherein the distal flame holder 102 includes a perforated flame holder, according to an embodiment.
  • the distal flame holder 102 can be implemented in the burner systems 111 , 200, and 300, according to various embodiments.
  • the terms distal flame holder, bluff body flame holder, perforated flame holder, perforated reaction holder, porous flame holder, porous reaction holder, duplex, and duplex tile shall be considered synonymous or interchangeable unless context dictates otherwise or further definition is provided.
  • FIGS. 7-10B shall be considered synonymous or interchangeable unless context dictates otherwise or further definition is provided.
  • distal flame holders 102 described herein can support very clean combustion. Specifically, in experimental use of burner systems 700 ranging from pilot scale to full scale, output of oxides of nitrogen (NOx) was measured to range from low single digit parts per million (ppm) down to undetectable (less than 1 ppm) concentration of NOx at the stack. These remarkable results were measured at 3% (dry) oxygen (O2) concentration with undetectable carbon monoxide (CO) at stack
  • the burner system 700 includes a fuel and oxidant source 702 disposed to output main fuel and oxidant into a combustion volume 704 to form a main fuel and oxidant mixture 706.
  • the fuel and oxidant source can include the main fuel nozzles 106.
  • fuel and oxidant mixture and fuel stream may be used interchangeably and considered synonymous depending on the context, unless further definition is provided.
  • combustion volume, combustion chamber, furnace volume, and the like shall be considered synonymous unless further definition is provided.
  • the perforated flame holder 102 is disposed in the combustion volume 704 and positioned to receive the main fuel and oxidant mixture 706.
  • FIG. 8 is a side sectional diagram 800 of a portion of a perforated flame holder as the distal flame holder 102 of FIG. 7, according to an embodiment.
  • the perforated flame holder 102 includes a perforated flame holder body 708 defining a plurality of perforations 710 aligned to receive the main fuel and oxidant mixture 706 from the fuel and oxidant source 702.
  • the terms perforation, pore, aperture, elongated aperture, and the like, in the context of the perforated flame holder 102 shall be considered synonymous unless further definition is provided.
  • the perforations 710 are configured to collectively hold a combustion reaction supported by the main fuel and oxidant mixture 706.
  • the fuel can include hydrogen, a hydrocarbon gas, a vaporized
  • the fuel can be a single species or can include a mixture of gas(es), vapor(s), atomized liquid(s), and/or pulverized solid(s).
  • the fuel in a process heater application the fuel can include fuel gas or byproducts from the process that include carbon monoxide (CO), hydrogen (hh), and methane (CFU).
  • the fuel in another application the fuel can include natural gas (mostly CFU) or propane (ObHb).
  • the fuel can include #2 fuel oil or #6 fuel oil. Dual fuel applications and flexible fuel applications are similarly contemplated by the inventors.
  • the oxidant can include oxygen carried by air, flue gas, and/or can include another oxidant, either pure or carried by a carrier gas.
  • the terms oxidant and oxidizer shall be considered synonymous herein.
  • the perforated flame holder body 708 can be bounded by an input face 712 disposed to receive the main fuel and oxidant mixture 706, an output face 714 facing away from the fuel and oxidant source 702, and a peripheral surface 716 defining a lateral extent of the perforated flame holder 102.
  • the plurality of perforations 710 which are defined by the perforated flame holder body 708 extend from the input face 712 to the output face 714.
  • the plurality of perforations 710 can receive the main fuel and oxidant mixture 706 at the input face 712.
  • the main fuel and oxidant mixture 706 can then combust in or near the plurality of perforations 710 and combustion products can exit the plurality of perforations 710 at or near the output face 714.
  • the perforated flame holder 102 is configured to hold a majority of the combustion reaction 802 within the perforations 710. For example, on a steady-state basis, more than half the molecules of fuel output into the combustion volume 704 by the fuel and oxidant source 702 may be converted to combustion products between the input face 712 and the output face 714 of the perforated flame holder 102. According to an alternative interpretation, more than half of the heat or thermal energy output by the combustion reaction 802 may be output between the input face 712 and the output face 714 of the perforated flame holder 102. As used herein, the terms heat, heat energy, and thermal energy shall be considered synonymous unless further definition is provided.
  • heat energy and thermal energy refer generally to the released chemical energy initially held by reactants during the combustion reaction 802.
  • heat, heat energy and thermal energy correspond to a detectable temperature rise undergone by real bodies characterized by heat capacities.
  • the perforations 710 can be configured to collectively hold at least 80% of the combustion reaction 802 between the input face 712 and the output face 714 of the perforated flame holder 102.
  • the inventors produced a combustion reaction 802 that was apparently wholly contained in the perforations 710 between the input face 712 and the output face 714 of the perforated flame holder 102.
  • the perforated flame holder 102 can support combustion between the input face 712 and output face 714 when combustion is“time-averaged.” For example, during transients, such as before the perforated flame holder 102 is fully heated, or if too high a (cooling) load is placed on the system, the combustion may travel somewhat downstream from the output face 714 of the perforated flame holder 102. Alternatively, if the cooling load is relatively low and/or the furnace temperature reaches a high level, the combustion may travel somewhat upstream of the input face 712 of the perforated flame holder 102.
  • transient“huffing” or flashback wherein a visible flame momentarily ignites in a region lying between the input face 712 of the perforated flame holder 102 and the main fuel nozzle 718, within the dilution region Dp.
  • transient huffing or flashback is generally short in duration such that, on a time-averaged basis, a majority of combustion occurs within the perforations 710 of the perforated flame holder 102, between the input face 712 and the output face 714.
  • the inventors have noted apparent combustion occurring downstream from the output face 714 of the perforated flame holder 102, but still a majority of combustion occurred within the perforated flame holder 102 as evidenced by continued visible glow from the perforated flame holder 102 that was observed.
  • the perforated flame holder 102 can be configured to receive heat from the combustion reaction 802 and output a portion of the received heat as thermal radiation 804 to heat-receiving structures (e.g., furnace walls and/or radiant section working fluid tubes) in or adjacent to the combustion volume 704.
  • heat-receiving structures e.g., furnace walls and/or radiant section working fluid tubes
  • terms such as radiation, thermal radiation, radiant heat, heat radiation, etc. are to be construed as being substantially synonymous, unless further definition is provided. Specifically, such terms refer to blackbody-type radiation of electromagnetic energy, primarily at infrared wavelengths, but also at visible wavelengths owing to elevated temperature of the perforated flame holder body 708.
  • the perforated flame holder 102 outputs another portion of the received heat to the main fuel and oxidant mixture 706 received at the input face 712 of the perforated flame holder 102.
  • the perforated flame holder body 708 may receive heat from the combustion reaction 802 at least in heat receiving regions 806 of perforation walls 808.
  • the position of the heat receiving regions 806, or at least the position corresponding to a maximum rate of receipt of heat can vary along the length of the perforation walls 808.
  • the location of maximum receipt of heat was apparently between 1/3 and 1/2 of the distance from the input face 712 to the output face 714 (i.e., somewhat nearer to the input face 712 than to the output face 714).
  • the heat receiving regions 806 may lie nearer to the output face 714 of the perforated flame holder 102 under other conditions. Most probably, there is no clearly defined edge of the heat receiving regions 806 (or for that matter, the heat output regions 810, described below). For ease of understanding, the heat receiving regions 806 and the heat output regions 810 will be described as particular regions 806, 810.
  • the perforated flame holder body 708 can be characterized by a heat capacity.
  • the perforated flame holder body 708 may hold thermal energy from the combustion reaction 802 in an amount corresponding to the heat capacity multiplied by temperature rise, and transfer the thermal energy from the heat receiving regions 806 to heat output regions 810 of the perforation walls 808.
  • the heat output regions 810 are nearer to the input face 712 than are the heat receiving regions 806.
  • the perforated flame holder body 708 can transfer heat from the heat receiving regions 806 to the heat output regions 810 via thermal radiation, depicted graphically as 804.
  • the perforated flame holder body 708 can transfer heat from the heat receiving regions 806 to the heat output regions 810 via heat conduction along heat conduction paths 812.
  • the perforated flame holder 102 may act as a heat source to maintain the combustion reaction 802, even under conditions where a combustion reaction 802 would not be stable when supported from a conventional flame holder.
  • the perforated flame holder 102 causes the combustion reaction 802 to begin within thermal boundary layers 814 formed adjacent to walls 808 of the perforations 710.
  • combustion is generally understood to include a large number of individual reactions, and since a large portion of combustion energy is released within the perforated flame holder 102, it is apparent that at least a majority of the individual reactions occur within the perforated flame holder 102.
  • the relatively cool main fuel and oxidant mixture 706 approaches the input face 712, the flow is split into portions that respectively travel through individual perforations 710.
  • the hot perforated flame holder body 708 transfers heat to the fluid, notably within thermal boundary layers 814 that progressively thicken as more and more heat is transferred to the incoming main fuel and oxidant mixture 706.
  • a combustion temperature e.g., the auto-ignition temperature of the fuel
  • the reactants continue to flow while a chemical ignition delay time elapses, over which time the combustion reaction 802 occurs. Accordingly, the combustion reaction 802 is shown as occurring within the thermal boundary layers 814.
  • the thermal boundary layers 814 merge at a merger point 816.
  • the merger point 816 lies between the input face 712 and output face 714 that define the ends of the perforations 710.
  • the combustion reaction 802 outputs more heat to the perforated flame holder body 708 than it receives from the perforated flame holder body 708.
  • the heat is received at the heat receiving region 806, is held by the perforated flame holder body 708, and is transported to the heat output region 810 nearer to the input face 712, where the heat is transferred into the cool reactants (and any included diluent) to bring the reactants to the ignition temperature.
  • each of the perforations 710 is characterized by a length L defined as a reaction fluid propagation path length between the input face 712 and the output face 714 of the perforated flame holder 102.
  • reaction fluid refers to matter that travels through a perforation 710.
  • the reaction fluid includes the main fuel and oxidant mixture 706 (optionally including nitrogen, flue gas, and/or other“non reactive” species).
  • the reaction fluid may include plasma associated with the combustion reaction 802, molecules of reactants and their constituent parts, any non-reactive species, reaction intermediates (including transition states), and reaction products.
  • the reaction fluid may include reaction products and byproducts, non-reactive gas, and excess oxidant.
  • the plurality of perforations 710 can be each characterized by a
  • the inventors have found that stable combustion can be maintained in the perforated flame holder 102 if the length L of each perforation 710 is at least four times the transverse dimension D of the perforation. In other embodiments, the length L can be greater than six times the transverse dimension D. For example, experiments have been run where L is at least eight, at least twelve, at least sixteen, and at least twenty-four times the transverse dimension D.
  • the length L is sufficiently long for thermal boundary layers 814 to form adjacent to the perforation walls 808 in a reaction fluid flowing through the perforations 710 to converge at merger points 816 within the perforations 710 between the input face 712 and the output face 714 of the perforated flame holder 102.
  • L/D ratios between 12 and 48 to work well (i.e., produce low NOx, produce low CO, and maintain stable combustion).
  • the perforated flame holder body 708 can be configured to convey heat between adjacent perforations 710.
  • the heat conveyed between adjacent perforations 710 can be selected to cause heat output from the combustion reaction portion 802 in a first perforation 710 to supply heat to stabilize a combustion reaction portion 802 in an adjacent perforation 710.
  • the fuel and oxidant source 702 can further include a main fuel nozzle 718 (e.g., corresponding to main fuel nozzle(s) 106 described herein), configured to output main fuel 114, and an oxidant source 720 configured to output a fluid including the oxidant.
  • the main fuel nozzle 718 can be configured to output substantially pure fuel (as opposed to, e.g., a fuel-air mixture).
  • the oxidant source 720 can be configured to output combustion air carrying oxygen, and optionally, flue gas.
  • the perforated flame holder 102 can be held by a perforated flame holder support structure 722 configured to hold the perforated flame holder 102 at a dilution distance D D away from the main fuel nozzle 718.
  • the main fuel nozzle 718 can be configured to emit a fuel jet selected to entrain the oxidant to form the main fuel and oxidant mixture 706 as the fuel jet and oxidant travel along a path to the perforated flame holder 102 through the dilution distance D D between the main fuel nozzle 718 and the perforated flame holder 102.
  • the oxidant or combustion air source 720 can be configured to entrain the fuel and the fuel and oxidant travel through the dilution distance D D .
  • a flue gas recirculation path 724 can be provided.
  • the main fuel nozzle 718 can be configured to emit a fuel jet selected to entrain the oxidant and to entrain flue gas as the fuel jet travels through the dilution distance D D between the main fuel nozzle 718 and the input face 712 of the perforated flame holder 102.
  • the main fuel nozzle 718 can be configured to emit the fuel through one or more fuel orifices 726 having an inside diameter dimension that is referred to as“nozzle diameter.”
  • the perforated flame holder support structure 722 can support the perforated flame holder 102 to receive the main fuel and oxidant mixture 706 at the distance D D away from the main fuel nozzle 718 greater than 20 times the nozzle diameter.
  • the perforated flame holder 102 is disposed to receive the main fuel and oxidant mixture 706 at the distance D D away from the main fuel nozzle 718 between 100 times and 1100 times the nozzle diameter.
  • the perforated flame holder support structure 722 is configured to hold the perforated flame holder 102 at a distance about 200 times or more of the nozzle diameter away from the main fuel nozzle 718.
  • the main fuel and oxidant mixture 706 travels about 200 times the nozzle diameter or more, the mixture is sufficiently homogenized to cause the combustion reaction 802 to produce minimal NOx.
  • the fuel and oxidant source 702 can alternatively include a premix fuel and oxidant source, according to an embodiment.
  • a premix fuel and oxidant source can include a premix chamber (not shown), a fuel nozzle configured to output fuel into the premix chamber, and an oxidant (e.g ., combustion air) channel configured to output the oxidant into the premix chamber.
  • a flame arrestor can be disposed between the premix fuel and oxidant source and the distal flame holder 102 and be configured to prevent flame flashback into the premix fuel and oxidant source.
  • a pilot burner, pilot flame holder, and/or continuous pilot flame may be disposed between the fuel and oxidant source 702 and the distal flame holder 102 to ensure
  • the oxidant source 720 can include a blower configured to force the oxidant through the fuel and oxidant source 702.
  • the perforated flame holder support structure 722 can be configured to support the perforated flame holder 102 from a floor or wall (not shown) of the combustion volume 704, for example. In another embodiment, the perforated flame holder support structure 722 supports the perforated flame holder 102 from the fuel and oxidant source 702. Alternatively, the perforated flame holder support structure 722 can suspend the perforated flame holder 102 from an overhead structure (such as a flue, in the case of an up-fired system). The perforated flame holder support structure 722 can support the perforated flame holder 102 in various orientations and directions.
  • the perforated flame holder 102 can include a single perforated flame holder body 708. In another embodiment, the perforated flame holder 102 can include a plurality of adjacent perforated flame holder sections that collectively provide a tiled perforated flame holder 102.
  • the perforated flame holder support structure 722 can be configured to support the plurality of perforated flame holder sections.
  • the perforated flame holder support structure 722 can include a metal superalloy, a cementatious, and/or ceramic refractory material.
  • the plurality of adjacent perforated flame holder sections can be joined with a fiber reinforced refractory cement.
  • the perforated flame holder 102 can have a width dimension W between opposite sides of the peripheral surface 716 at least twice a thickness dimension T between the input face 712 and the output face 714. In another embodiment, the perforated flame holder 102 can have a width dimension W between opposite sides of the peripheral surface 716 at least three times, at least six times, or at least nine times the thickness dimension T between the input face 712 and the output face 714 of the perforated flame holder 102.
  • the perforated flame holder 102 can have a width dimension W less than a width of the combustion volume 704. This can allow the flue gas recirculation path 724 from above to below the perforated flame holder 102 to lie between the peripheral surface 716 of the perforated flame holder 102 and the combustion volume wall (not shown).
  • the perforations 710 can be of various shapes.
  • the perforations 710 can include elongated squares, each having a transverse dimension D between opposing sides of the squares.
  • the perforations 710 can include elongated hexagons, each having a transverse dimension D between opposing sides of the hexagons.
  • the perforations 710 can include hollow cylinders, each having a transverse dimension D corresponding to a diameter of the cylinder.
  • the perforations 710 can include truncated cones or truncated pyramids (e.g., frustums), each having a transverse dimension D radially symmetric relative to a length axis that extends from the input face 712 to the output face 714.
  • the perforations 710 can each have a lateral dimension D equal to or greater than a quenching distance of the flame based on standard reference conditions.
  • the perforations 710 may have lateral dimension D less then than a standard reference quenching distance.
  • each of the plurality of perforations 710 has a lateral dimension D between 0.05 inch and 1.0 inch.
  • each of the plurality of perforations 710 has a lateral dimension D between 0.1 inch and 0.5 inch.
  • the plurality of perforations 710 can each have a lateral dimension D of about 0.2 to 0.4 inch.
  • the void fraction of a perforated flame holder 102 is defined as the total volume of all perforations 710 in a section of the perforated flame holder 102 divided by a total volume of the perforated flame holder 102 including perforated flame holder body 708 and perforations 710.
  • the perforated flame holder 102 should have a void fraction between 0.10 and 0.90.
  • the perforated flame holder 102 can have a void fraction between 0.30 and 0.80.
  • the perforated flame holder 102 can have a void fraction of about 0.70. Using a void fraction of about 0.70 was found to be especially effective for producing very low NOx.
  • the perforated flame holder 102 can be formed from a fiber reinforced cast refractory material and/or a refractory material such as an aluminum silicate material.
  • the perforated flame holder 102 can be formed to include mullite or cordierite.
  • the perforated flame holder body 708 can include a metal superalloy such as Inconel or Hastelloy.
  • the perforated flame holder body 708 can define a honeycomb. Honeycomb is an industrial term of art that need not strictly refer to a hexagonal cross section and most usually includes cells of square cross section. Honeycombs of other cross sectional areas are also known.
  • the perforated flame holder 102 can be formed from VERSAGRID ® ceramic honeycomb, available from Applied
  • the perforations 710 can be parallel to one another and normal to the input and output faces 712, 714. In another embodiment, the perforations 710 can be parallel to one another and formed at an angle relative to the input and output faces 712, 714. In another embodiment, the perforations 710 can be non parallel to one another. In another embodiment, the perforations 710 can be non-parallel to one another and non-intersecting. In another embodiment, the perforations 710 can be intersecting.
  • the perforated flame holder body 708 can be one piece or can be formed from a plurality of sections.
  • the perforated flame holder 102 may be formed from reticulated ceramic material.
  • reticulated refers to a netlike structure. Reticulated ceramic material is often made by dissolving a slurry into a sponge of specified porosity, allowing the slurry to harden, and burning away the sponge and curing the ceramic.
  • the perforated flame holder 102 may be formed from a ceramic material that has been punched, bored or cast to create channels.
  • the perforated flame holder 102 can include a plurality of tubes or pipes bundled together.
  • the plurality of perforations 710 can include hollow cylinders and can optionally also include interstitial spaces between the bundled tubes.
  • the plurality of tubes can include ceramic tubes. Refractory cement can be included between the tubes and configured to adhere the tubes together.
  • the plurality of tubes can include metal (e.g., superalloy) tubes.
  • the plurality of tubes can be held together by a metal tension member circumferential to the plurality of tubes and arranged to hold the plurality of tubes together.
  • the metal tension member can include stainless steel, a superalloy metal wire, and/or a superalloy metal band.
  • the perforated flame holder body 708 can alternatively include stacked perforated sheets of material, each sheet having openings that connect with openings of subjacent and superjacent sheets.
  • the perforated sheets can include perforated metal sheets, ceramic sheets and/or expanded sheets.
  • the perforated flame holder body 708 can include discontinuous packing bodies such that the perforations 710 are formed in the interstitial spaces between the discontinuous packing bodies.
  • the discontinuous packing bodies include structured packing shapes.
  • the discontinuous packing bodies include random packing shapes.
  • the discontinuous packing bodies can include ceramic Raschig ring, ceramic Berl saddles, ceramic Intalox saddles, and/or metal rings or other shapes (e.g., Super Raschig Rings) that may be held together by a metal cage.
  • burner systems including the perforated flame holder 102 provide such clean combustion.
  • the perforated flame holder 102 may act as a heat source to maintain a combustion reaction 802 even under conditions where a combustion reaction 802 would not be stable when supported by a conventional flame holder. This capability can be leveraged to support combustion using a leaner fuel-to-oxidant mixture than is typically feasible.
  • an average fuel-to-oxidant ratio of the fuel stream 706 is below a (conventional) lower combustion limit of the fuel component of the fuel stream 706— lower combustion limit defines the lowest concentration of fuel at which a main fuel and oxidant mixture 706 will burn when exposed to a momentary ignition source under normal atmospheric pressure and an ambient temperature of 25° C (77° F).
  • the perforated flame holder 102 and systems including the perforated flame holder 102 and/or other distally placed flame holder described herein were found to provide substantially complete combustion of CO (single digit ppm down to undetectable, depending on experimental conditions), while supporting low NOx. According to one interpretation, such a performance can be achieved due to a sufficient mixing used to lower peak flame temperatures (among other strategies). Flame temperatures tend to peak under slightly rich conditions, which can be evident in any diffusion flame that is insufficiently mixed. By sufficiently mixing, a homogenous and slightly lean mixture can be achieved prior to combustion. This combination can result in reduced flame temperatures, and thus reduced NOx formation.
  • “slightly lean” may refer to 3% O2, i.e., an equivalence ratio of -0.87. Use of even leaner mixtures is possible, but may result in elevated levels of O2. Moreover, the inventors believe perforation walls 808 may act as a heat sink for the combustion fluid. This effect may alternatively or additionally reduce combustion temperatures and lower NOx.
  • production of NOx can be reduced if the combustion reaction 802 occurs over a very short duration of time.
  • Rapid combustion causes the reactants (including oxygen and entrained nitrogen) to be exposed to NOx-formation temperature for a time too short for NOx formation kinetics to cause significant production of NOx.
  • the time required for the reactants to pass through the perforated flame holder 102 is very short compared to a conventional flame.
  • the low NOx production associated with perforated flame holder combustion may thus be related to the short duration of time required for the reactants (and entrained nitrogen) to pass through the perforated flame holder 102.
  • FIG. 9 is a flow chart showing a method 900 for operating a burner system including the distal flame holder 102 (e.g., a perforated flame holder) shown and described herein, according to an embodiment.
  • the distal flame holder is first heated to a temperature sufficient to maintain combustion of the fuel and oxidant mixture.
  • the method 900 begins with step 902, wherein the distal flame holder is preheated to a start-up temperature, Ts. After the distal flame holder is raised to the start-up temperature, the method proceeds to step 904, wherein the fuel and oxidant are provided to the distal flame holder and combustion is held by the distal flame holder.
  • step 902 begins with step 906, wherein start-up energy is provided at the distal flame holder.
  • a decision step 908 determines whether the temperature T of the distal flame holder is at or above the start-up temperature, Ts. As long as the temperature of the distal flame holder is below its start-up temperature, the method loops between steps 906 and 908 within the preheat step 902. In decision step 908, if the temperature T of at least a predetermined portion of the distal flame holder is greater than or equal to the start-up temperature, the method 900 proceeds to overall step 904, wherein fuel and oxidant is supplied to and combustion is held by the distal flame holder.
  • Step 904 may be broken down into several discrete steps, at least some of which may occur simultaneously.
  • a fuel and oxidant mixture is provided to the distal flame holder, as shown in step 910.
  • the fuel and oxidant may be provided by a fuel and oxidant source that includes a separate fuel nozzle and oxidant (e.g., combustion air) source, for example.
  • the fuel and oxidant are output in one or more directions selected to cause the fuel and oxidant mixture to be received by the input face of the distal flame holder.
  • the fuel may entrain the combustion air (or alternatively, the combustion air may dilute the fuel) to provide a fuel and oxidant mixture at the input face of the distal flame holder at a fuel dilution selected for a stable combustion reaction that can be held within the perforations of the distal flame holder.
  • step 912 the combustion reaction is held by the distal flame holder.
  • heat may be output from the distal flame holder.
  • the heat output from the distal flame holder may be used to power an industrial process, heat a working fluid, generate electricity, or provide motive power, for example.
  • step 916 the presence of combustion may be sensed.
  • Various sensing approaches have been used and are contemplated by the inventors.
  • combustion held by the distal flame holder is very stable and no unusual sensing requirement is placed on the system.
  • Combustion sensing may be performed using an infrared sensor, a video sensor, an ultraviolet sensor, a charged species sensor, thermocouple, thermopile, flame rod, and/or other combustion sensing apparatuses.
  • a pilot flame or other ignition source may be provided to cause ignition of the fuel and oxidant mixture in the event combustion is lost at the distal flame holder.
  • step 918 if combustion is sensed not to be stable, the method 900 may exit to step 924, wherein an error procedure is executed.
  • the error procedure may include turning off fuel flow, re-executing the preheating step 902, outputting an alarm signal, igniting a stand-by combustion system, or other steps.
  • decision step 918 combustion in the distal flame holder is determined to be stable
  • the method 900 proceeds to decision step 920, wherein it is determined if combustion parameters should be changed. If no combustion parameters are to be changed, the method loops (within step 904) back to step 910, and the combustion process continues. If a change in combustion parameters is indicated, the method 900 proceeds to step 922, wherein the combustion parameter change is executed. After changing the combustion parameter(s), the method loops (within step 904) back to step 910, and combustion continues.
  • Combustion parameters may be scheduled to be changed, for example, if a change in heat demand is encountered. For example, if less heat is required (e.g ., due to decreased electricity demand, decreased motive power requirement, or lower industrial process throughput), the fuel and oxidant flow rate may be decreased in step 922. Conversely, if heat demand is increased, then fuel and oxidant flow may be increased. Additionally or alternatively, if the combustion system is in a start-up mode, then fuel and oxidant flow may be gradually increased to the distal flame holder over one or more iterations of the loop within step 904.
  • the burner system 700 includes a heater 728 operatively coupled to the distal flame holder 102.
  • the distal flame holder 102 operates by outputting heat to the incoming main fuel and oxidant mixture 706. After combustion is established, this heat is provided by the combustion reaction 802; but before combustion is established, the heat is provided by the heater 728.
  • the heater 728 can include a flame holder configured to support a flame disposed to heat the distal flame holder 102.
  • the fuel and oxidant source 702 can include a main fuel nozzle 718 configured to emit a fuel stream 706 and an oxidant source 720 configured to output oxidant (e.g., combustion air) adjacent to the fuel stream 706.
  • the main fuel nozzle 718 and oxidant source 720 can be configured to output the fuel stream 706 to be progressively diluted by the oxidant (e.g., combustion air).
  • the distal flame holder 102 can be disposed to receive a diluted main fuel and oxidant mixture 706 that supports a combustion reaction 802 that is stabilized by the distal flame holder 102 when the distal flame holder 102 is at an operating temperature.
  • a start-up flame holder in contrast, can be configured to support a start-up flame at a location corresponding to a relatively unmixed fuel and oxidant mixture that is stable without stabilization provided by the heated distal flame holder 102.
  • the burner system 700 can further include a controller 730 operatively coupled to the heater 728 and to a data interface 732.
  • the controller 730 can be configured to control a start-up flame holder actuator configured to cause the start-up flame holder to hold the start-up flame when the distal flame holder 102 needs to be pre-heated and to not hold the start-up flame when the distal flame holder 102 is at an operating temperature (e.g., when T > Ts).
  • a start-up flame holder actuator configured to cause the start-up flame holder to hold the start-up flame when the distal flame holder 102 needs to be pre-heated and to not hold the start-up flame when the distal flame holder 102 is at an operating temperature (e.g., when T > Ts).
  • the start-up flame holder includes a mechanically-actuated distal configured to be actuated to intercept the main fuel and oxidant mixture 706 to cause heat-recycling and/or stabilizing vortices and thereby hold a start-up flame; or to be actuated to not intercept the main fuel and oxidant mixture 706 to cause the main fuel and oxidant mixture 706 to proceed to the distal flame holder 102.
  • a fuel control valve, blower, and/or damper may be used to select a main fuel and oxidant mixture 706 flow rate that is sufficiently low for a start-up flame to be jet-stabilized; and upon reaching a distal flame holder 102 operating temperature, the flow rate may be increased to“blow out” the start-up flame.
  • the heater 728 may include an electrical power supply operatively coupled to the controller 730 and configured to apply an electrical charge or voltage to the main fuel and oxidant mixture 706.
  • An electrically conductive start-up flame holder may be selectively coupled to a voltage ground or other voltage selected to attract the electrical charge in the main fuel and oxidant mixture 706. The attraction of the electrical charge was found by the inventors to cause a start-up flame to be held by the electrically conductive start-up flame holder.
  • the heater 728 may include an electrical resistance heater configured to output heat to the distal flame holder 102 and/or to the main fuel and oxidant mixture 706.
  • the electrical resistance heater 728 can be configured to heat up the distal flame holder 102 to an operating temperature.
  • the heater 728 can further include a power supply and a switch operable, under control of the controller 730, to selectively couple the power supply to the electrical resistance heater 728.
  • An electrical resistance heater 728 can be formed in various ways.
  • the electrical resistance heater 728 can be formed from KANTHAL® wire (available from Sandvik Materials Technology division of Sandvik AB of Hallstahammar, Sweden) threaded through at least a portion of the perforations 710 defined by the distal flame holder body 708.
  • the heater 728 can include an inductive heater, a high-energy beam heater (e.g ., microwave or laser), a frictional heater, electro-resistive ceramic coatings, or other types of heating technologies.
  • the heater 728 can include an electrical discharge igniter or hot surface igniter configured to output a pulsed ignition to the oxidant and fuel.
  • a start-up apparatus can, as discussed in greater detail herein, include a pilot flame apparatus disposed to ignite the main fuel and oxidant mixture 706 that would otherwise enter the distal flame holder 102.
  • the electrical discharge igniter, hot surface igniter, and/or pilot flame apparatus can be operatively coupled to the controller 730, which can cause the electrical discharge igniter or pilot flame apparatus to maintain combustion of the main fuel and oxidant mixture 706 in or upstream from the distal flame holder 102 before the distal flame holder 102 is heated sufficiently to maintain combustion.
  • the burner system 700 can further include a sensor 734 operatively coupled to the controller 730.
  • the sensor 734 can include a heat sensor configured to detect infrared radiation or a temperature of the distal flame holder 102.
  • the control circuit 730 can be configured to control the heater 728 responsive to input from the sensor 734.
  • a fuel control valve 736 can be operatively coupled to the controller 730 and configured to control a flow of fuel to the fuel and oxidant source 702.
  • an oxidant blower or damper 738 can be operatively coupled to the controller 730 and configured to control flow of the oxidant (or combustion air).
  • the sensor 734 can further include a combustion sensor operatively coupled to the control circuit 730, the combustion sensor being configured to detect a temperature, video image, and/or spectral characteristic of a combustion reaction 802 held by the distal flame holder 102.
  • the fuel control valve 736 can be configured to control a flow of fuel from a fuel source to the fuel and oxidant source 702.
  • the controller 730 can be configured to control the fuel control valve 736 responsive to input from the combustion sensor 734.
  • the controller 730 can be configured to control the fuel control valve 736 and/or oxidant blower or damper 738 to control a preheat flame type of heater 728 to heat the distal flame holder 102 to an operating temperature.
  • the controller 730 can similarly control the fuel control valve 736 and/or the oxidant blower or damper 738 to change the main fuel and oxidant mixture 706 flow responsive to a heat demand change received as data via the data interface 732.
  • FIG. 10A is a simplified perspective view of a combustion system 1000, including another alternative distal flame holder 102, according to an
  • the distal flame holder 102 is a reticulated ceramic perforated flame holder configured to hold a combustion reaction, according to an embodiment.
  • FIG. 10B is a simplified side sectional diagram of a portion of the reticulated ceramic perforated flame holder 102 of FIG. 10A, according to an embodiment.
  • the distal flame holder 102 of FIGS. 10A, 10B can be
  • the distal flame holder 102 is configured to support a combustion reaction (e.g., combustion reaction 802 of FIG. 8) of the main fuel and oxidant mixture 706 received from the fuel and oxidant source 702 at least partially within the distal flame holder 102.
  • the distal flame holder 102 can be configured to support a combustion reaction of the main fuel and oxidant mixture 706 upstream, downstream, within, and adjacent to the reticulated ceramic perforated flame holder 102.
  • the perforated flame holder body 708 can include reticulated fibers 1039.
  • the reticulated fibers 1039 can define branching perforations 710 that weave around and through the reticulated fibers 1039.
  • the perforations 710 are formed as passages between the reticulated fibers 1039.
  • the reticulated fibers 1039 are formed as a reticulated ceramic foam. According to an embodiment, the reticulated fibers 1039 are formed using a reticulated polymer foam as a template. According to an embodiment, the reticulated fibers 1039 can include alumina silicate.
  • the reticulated fibers 1039 can be formed from extruded mullite or cordierite. According to an embodiment, the reticulated fibers 1039 can include Zirconia. According to an embodiment, the reticulated fibers 1039 can include silicon carbide.
  • the term“reticulated fibers” refers to a netlike structure.
  • the reticulated fibers 1039 are formed from an extruded ceramic material.
  • the interaction between the main fuel and oxidant mixture 706, the combustion reaction 802, and heat transfer to and from the perforated flame holder body 708 can function similarly to the embodiment shown and described above with respect to FIGS. 7-9.
  • One difference in activity is a mixing between perforations 710, because the reticulated fibers 1039 form a discontinuous perforated flame holder body 708 that allows flow back and forth between neighboring perforations 710.
  • the network of reticulated fibers 1039 is sufficiently open for downstream reticulated fibers 1039 to emit radiation for receipt by upstream reticulated fibers 1039 for the purpose of heating the upstream reticulated fibers 1039 sufficiently to maintain combustion of a main fuel and oxidant mixture 706.
  • heat conduction paths such as heat conduction paths 812 in FIG. 8 between reticulated fibers 1039 are reduced due to separation of the reticulated fibers 1039. This may cause relatively more heat to be transferred from a heat receiving region or area (such as heat receiving region 806 in FIG. 8) to a heat- output region or area (such as heat-output region 810 of FIG.
  • individual perforations 710 may extend between an input face 712 to an output face 714 of the perforated flame holder 102.
  • Perforations 710 may have varying lengths L. According to an
  • the perforated flame holder 102 is configured to support or hold a combustion reaction (see element 802 of FIG. 8) or a flame at least partially between the input face 712 and the output face 714.
  • the input face 712 corresponds to a surface of the perforated flame holder 102 proximal to the main fuel nozzle 718 or to a surface that first receives fuel.
  • the input face 712 corresponds to an extent of the reticulated fibers 1039 proximal to the main fuel nozzle 718.
  • the output face 714 corresponds to a surface distal to the main fuel nozzle 718 or opposite the input face 712.
  • the input face 712 corresponds to an extent of the reticulated fibers 1039 distal to the main fuel nozzle 718 or opposite to the input face 712.
  • the formation of thermal boundary layers 814, transfer of heat between the perforated flame holder body 708 and the gases flowing through the perforations 710, a characteristic perforation width dimension D, and the length L can each be regarded as related to an average or overall path through the perforated reaction holder 102.
  • the dimension D can be determined as a root-mean-square of individual Dn values determined at each point along a flow path.
  • the length L can be a length that includes length contributed by tortuosity of the flow path, which may be somewhat longer than a straight line distance TRH from the input face 712 to the output face 714 through the perforated reaction holder 102.
  • the void fraction (expressed as (total perforated reaction holder 102 volume - reticulated fiber 1039 volume)/total volume)) is about 70%.
  • the reticulated ceramic perforated flame holder 102 is a tile about 1” x 4” x 4”. According to an embodiment, the reticulated ceramic perforated flame holder 102 includes about 100 pores per square inch of surface area. Other materials and dimensions can also be used for a reticulated ceramic perforated flame holder 102 in accordance with principles of the present disclosure.
  • the reticulated ceramic perforated flame holder 102 can include shapes and dimensions other than those described herein.
  • the perforated flame holder 102 can include reticulated ceramic tiles that are larger or smaller than the dimensions set forth above.
  • the reticulated ceramic perforated flame holder 102 can include shapes other than generally cuboid shapes.
  • the reticulated ceramic perforated flame holder 102 can include multiple reticulated ceramic tiles.
  • the multiple reticulated ceramic tiles can be joined together such that each ceramic tile is in direct contact with one or more adjacent reticulated ceramic tiles.
  • the multiple reticulated ceramic tiles can collectively form a single perforated flame holder 102.
  • each reticulated ceramic tile can be considered a distinct perforated flame holder 102.
  • FIG. 11 is a flow chart showing a method 1100 for operating a distal flame holder burner system, according to an embodiment. According to an
  • the method 1100 includes, in operation 1102, providing heat to a distal flame holder (102) 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 may be disposed between the distal flame holder and one or more main fuel nozzles, and a distance between the pilot burner and the distal flame holder is smaller than a distance between the pilot burner and the one or more main fuel nozzles.
  • Operation 1104 includes introducing mixed main fuel and air to the distal flame holder.
  • Operation 1106 includes holding at least a portion of a combustion reaction of the mixed main fuel and air within the distal flame holder while the pilot burner continues to support the pilot flame.
  • Operation 1102 may include providing the pilot fuel to the pilot burner from a pilot fuel source, controlling a pilot fuel rate of flow, and emitting the pilot fuel from a plurality of orifices (e.g., 218 in FIGS. 2A, 2B, 4-6) of the pilot burner.
  • the orifices may be disposed across a breadth of the mixed main fuel and air.
  • the operation may further include igniting the mixed main fuel and air at the pilot burner with the pilot flame.
  • the method 1100 may further include 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. Reducing the size of the pilot flame relative to the size of the combustion reaction of the mixed main fuel and air may cause a reduction of emissions of oxides of nitrogen.
  • the introducing the mixed main fuel and air to the distal flame holder may include introducing at a proximal end of a mixing tube, the main fuel via the one or more main fuel nozzles, and the air.
  • the proximal end of the mixing tube may be disposed proximate to the one or more main fuel nozzles, while the distal end of the mixing tube may be disposed proximate to the distal flame holder.
  • the mixing tube may be open from its proximal end to its distal end.
  • the method 1100 may further include educing a flue gas into the proximal end of the mixing tube.
  • the pilot burner may be disposed between the distal flame holder and the distal end of the mixing tube.
  • FIG. 12 is a flow chart showing a method 1200 for operating a burner system, according to an embodiment.
  • the method 1200 includes, in operation 1202, supporting a diffusion flame across a portion of a width of a furnace volume at a position distal from a furnace floor.
  • Operation 1204 includes providing combustion air to the furnace volume from a location near the furnace floor.
  • Operation 1206 includes outputting a high pressure main fuel jet from each of one or more main fuel nozzles at one or more locations near the furnace floor.
  • Operation 1208 includes mixing the main fuel with the combustion air while the main fuel and combustion air travel from the locations near the furnace floor to the distal position.
  • Operation 1210 includes combusting the main fuel by exposing the mixed main fuel and air to the diffusion flame.
  • the method 1200 may further include holding a main flame, resulting from combusting the main fuel, at a stable position with a distal flame holder disposed more distal from the furnace floor than the diffusion flame.
  • the supporting of a diffusion flame may include producing and holding the diffusion flame at a pilot burner, the pilot burner being disposed in the furnace volume between the one or more main fuel nozzles and the distal flame holder.
  • the pilot burner may be disposed in closer proximity to the distal flame holder than it is to the furnace floor.
  • the holding of the diffusion flame at the pilot burner may include supplying a pilot fuel to the pilot burner, emitting the pilot fuel from one or more pilot fuel orifices of the pilot burner, and maintaining ignition of a mixture of combustion air and the emitted pilot fuel at the pilot burner to support the diffusion flame.
  • the one or more pilot fuel orifices may constitute a plurality of pilot fuel orifices disposed across the portion of the width of the furnace volume sufficiently wide to cause contact of the diffusion flame with the mixture of the main fuel and combustion air across a width of mixed main fuel and combustion air. Additionally and/or alternatively, the one or more pilot fuel orifices may include a plurality of pilot fuel orifices having a collective area sufficiently large to support the diffusion flame at a low momentum.
  • the holding the diffusion flame at the pilot burner may include controlling a rate of supply of a pilot fuel to the pilot burner.
  • the method 1200 may further include detecting a temperature of a distal flame holder disposed above the diffusion flame, and when the distal flame holder reaches at least a predetermined threshold temperature, reducing a rate of supply of a pilot fuel to a pilot burner supporting the diffusion flame.
  • the method 1200 may further include detecting the combusting of the main fuel at the distal flame holder using a an electrocapacitive sensor, the electrocapacitive sensor configured to output sensor signals to a controller.
  • a combustion system may include an oxidant source configured to output an oxidant into a furnace volume.
  • a pilot burner may be configured to support a pilot flame by outputting a pilot fuel to support a pilot diffusion flame at least during a preheating state, and a main fuel nozzle may be configured to output a main fuel into the furnace volume from a proximal position during a standard operating state at least after the preheating state is complete.
  • the combustion system may include includes a distal flame holder positioned in the furnace volume to be preheated by the pilot flame during the preheating state and to hold a combustion reaction of the main fuel and oxidant adjacent to the distal flame holder during the standard operating state, and 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.
  • the combustion system further includes one or more actuators configured to adjust a flow of the main fuel from the main fuel nozzle, to adjust a flow of the pilot fuel to the pilot burner, and to adjust a flow of the oxidant from the oxidant source.
  • a controller is communicatively coupled to the actuators and the combustion sensor.
  • the controller may be configured to receive the sensor signals 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 signals and in accordance with software instructions stored in a non-transitory computer readable medium coupled to the controller.
  • the combustion system further includes a pilot flame sensor configured to sense a condition of a pilot flame and to output a sensor signal indicative of the condition of the pilot flame.
  • the combustion sensor may include the pilot flame sensor.
  • the pilot flame sensor may include an electrocapacitive sensor, an electro-resistive sensor, and/or a tomographic sensor (e.g., employing electrocapacitive tomography (ECT).)
  • the combustion system further includes an ignitor configured to generate an arc.
  • the controller may be configured to control one or more of the actuators to cause the ignitor to generate the arc to ignite the pilot flame if the electrocapacitive sensor indicates that the pilot flame is not present and all safety interlocks are met.
  • the controller is configured to adjust a size of the pilot flame 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.
  • the combustion sensor may be configured to detect the combustion reaction at the distal flame holder and to output sensor signals to the controller responsive to a detected state of the combustion reaction.
  • the combustion sensor is configured for operation as a flashback sensor configured to detect a flashback of the
  • the combustion sensor may include an electrocapacitive sensor.
  • FIG. 13A is a diagram of a combustion system 1300 including a distal flame holder 102 and an electrocapacitive (EC) sensor 1305, according to an embodiment.
  • FIG. 13B is a top view of the distal flame holder 102 and an electrocapacitive sensor 1305, according to an embodiment.
  • EC electrocapacitive
  • the EC sensor may be configured as an
  • ECT electrocapacitive tomography
  • a combustion sensor may be configured as an electro-resistive or electro-conductive sensor by modifying the signal processing.
  • electocapacitive will be understood to refer also to electro-resistive or electro-conductive sensors.
  • An EC sensor is essentially a simplified ECT sensor in that it has fewer electrodes and can sense combustion presence, but not necessarily a specific location of combustion. It will be understood that references to ECT sensors similarly refer to EC sensors.
  • ECT electrocapacitive tomography
  • ECT sensing may be fundamentally capacitive, or may additionally or alternatively be made to measure a conductance, a resistance, an impedance, or other electrical parameter.
  • ECT may include a plurality of sensor channels, such as may be produced by moving a sensor through different positions or by using a sensor array, such as may be seen in more common (e.g., medical) tomography systems.
  • an ECT system may include a range of sensor channels as few as a single channel defined by two electrodes positioned relative to a sensed region (e.g., a flame holding region, a blow-off region, a flash-back region, a flue gas region, a pilot flame region, etc.).
  • a sensed region e.g., a flame holding region, a blow-off region, a flash-back region, a flue gas region, a pilot flame region, etc.
  • the combustion system 1300 may include a
  • the electrocapacitive sensor 1305 can include a first set of electrodes 1320, including multiple pairs of electrodes 1320, positioned laterally around the distal flame holder 102 in order to sense a parameter of the distal flame holder 102.
  • the electrocapacitive sensor 1305 can also include a second set of electrodes positioned upstream from the distal flame holder 102.
  • the first set of electrodes 1320 can sense a capacitance or other parameter in a vicinity of the distal flame holder 102.
  • the second set of electrodes can sense a capacitance or other parameter upstream from the distal flame holder 102, for example at a pilot burner (e.g., 104 in FIG. 3) or upstream from the pilot burner.
  • the controller 730 can compare the
  • the combustion system 1300 may include a distal flame holder sensor that includes the electrocapacitive sensor 1305.
  • the distal flame holder sensor can share use of the first set of electrodes 1320 described in relation to the combustion sensor.
  • the first set of electrodes 1320 including pairs of electrodes positioned laterally around the distal flame holder 102 can act as both the electrocapacitive sensor 1305, and at least a portion of the combustion sensor.
  • the combustion system 1300 may include a pilot flame sensor (not shown) that includes the electrocapacitive sensor 1305.
  • the pilot flame sensor and the combustion sensor can share use of electrodes positioned upstream from the distal flame holder 102 or laterally around the distal flame holder 102.
  • Two or more of the pilot flame sensors, the combustion sensor, and the distal flame holder sensor can share electrodes 1320 of an electrocapacitive sensor 1305.
  • the combustion system 1300 includes a fuel and oxidant source 702, a distal flame holder 102, a controller 730, an electrocapacitive tomography device 1305, and a memory 1307.
  • the fuel and oxidant source 702 can include main fuel nozzle(s) (e.g., the main fuel nozzles 106 described above) and the oxidant source 720. Additionally, the fuel and oxidant source 702 can include a pilot burner, such as the pilot burner 104 described above.
  • the fuel and oxidant source 702 includes, for example, a fuel nozzle configured to output the main fuel and oxidant onto the distal flame holder 102.
  • the distal flame holder 102 holds a combustion reaction of the fuel and oxidant primarily adjacent to and/or within the distal flame holder 102.
  • the electrocapacitive sensor 1305 may be configured as an image capture device (e.g., using ECT) that includes a plurality of electrodes 1320 positioned at selected locations adjacent to the distal flame holder 102.
  • the electrocapacitive sensor 1305 is configured to make images of the distal flame holder 102 based on the capacitance between the electrodes 1320.
  • the images represent slices of the distal flame holder 102 based on the capacitances between the electrodes 1320.
  • the capacitance between pairs of electrodes 1320 depends, in part, on the dielectric constant of the material(s) between the pairs of electrodes 1320.
  • the dielectric constant within the perforations of the distal flame holder 102 can change based on the characteristics of the combustion reaction within the perforations. Therefore, the images produced by the electrocapacitive sensor 1305 can give an indication of a temperature within the perforations or a concentration or flow of fuel, oxidant, and flue gasses at various locations corresponding to the distal flame holder 102 based on the dielectric constant at the various locations of the distal flame holder 102.
  • the controller 730 can analyze the images and adjust the combustion reaction based on the images.
  • the controller 730 is configured to cause the electrocapacitive sensor 1305 to capture one or more images of the combustion reaction. In one embodiment, the controller 730 is further configured to analyze the one or more images and to adjust the characteristics of the combustion reaction based on the analysis of the one or more images.
  • FIG. 13B is a top view of the distal flame holder 102 and the
  • electrocapacitive sensor 1305, according to an embodiment.
  • electrocapacitive sensor 1305 includes multiple pairs of electrodes 1320 positioned laterally around the distal flame holder 102.
  • Each pair of electrodes 1320 includes two electrodes 1320 opposite one another, with the distal flame holder 102 positioned between the pair of electrodes 1320 or in a fringing field therebetween.
  • the controller 730 controls each pair of electrodes 1320 to make a plurality of images (or an aggregate image) of the distal flame holder 102, according to an embodiment.
  • the electrodes 1320a and 1320a are a pair, the electrodes 1320b and 1320b are a pair, the electrodes 1320c and 1320c are a pair, the electrodes 1320d and 1320d are a pair, the electrodes 1320e and 1320e are a pair, and the electrodes 1320f and 1320f are a pair.
  • the electrocapacitive sensor 1305 can generate electrocapacitive tomography images based on a capacitance between the pairs of electrodes 1320.
  • the plurality of electrodes 1320 includes one or more first pairs of electrodes 1320 separated from each other by the distal flame holder 102 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 102.
  • the first pairs of electrodes 1320 can include the pair of electrodes 1320a and the pair of electrodes 1320b.
  • the first pairs of electrodes 1320a and 1320b sense the capacitance of the distal flame holder 102 along an X direction substantially perpendicular to a primary direction of flow of the main fuel and the oxidant toward the distal flame holder 102.
  • the primary direction of flow of the main fuel and the oxidant toward the distal flame holder 102 can correspond to a Z direction.
  • the plurality of electrodes 1320 includes one or more second pairs of electrodes separated from each other by the distal flame holder 102 and disposed opposite each other in a second orientation substantially perpendicular to both the first orientation and the primary direction of the flow of the main fuel.
  • the second pairs of electrodes 1320 can include the pair of electrodes 1320c and the pair of electrodes 1320d.
  • the second pairs of electrodes 1320c and 1320d sense the capacitance of the distal flame holder 102 along a Y direction substantially perpendicular to the primary direction of flow of the main fuel and the oxidant and substantially perpendicular to orientation of the first pairs of electrodes 1320a and 1320b.
  • the plurality of electrodes 1320 can include pairs of electrodes 1320 oriented transverse to both the first pairs of electrodes 1320a and 1320b and the second pairs of electrodes 1320c and 1320d.
  • the transverse pairs of electrodes 1320 can include the pair of electrodes 1320e and the pair of electrodes 1320f.
  • FIG. 13A and FIG. 13B have shown the same
  • electrocapacitive sensor 1305 including the electrodes 1320 positioned laterally around the distal flame holder 102
  • an electrocapacitive sensor in accordance with principles of the present disclosure can include pairs of electrodes
  • An electrocapacitive sensor can include pairs of electrodes positioned upstream from the distal flame holder 102, downstream from the distal flame holder 102, or in other locations depending on the particular aspect of a combustion system that the electrocapacitive sensor is intended to sense or monitor. Accordingly, other sensors described or contemplated in relation to embodiments disclosed herein (e.g., sensors 734, 1414) can include electrocapacitive sensors where suitable.
  • FIG. 14 is a diagram of a low emissions modular burner system 1400 including one or more burner modules 1401 according to an embodiment.
  • Each burner module 1401 may include a main fuel source, separately valved from all other fuel sources, configured to selectively deliver a main fuel stream 1404 for dilution by a flow of combustion air.
  • the main fuel source may, in certain embodiments, correspond to or be implemented to include one or more main fuel nozzles 1402.
  • Each burner module 1401 may include a main fuel igniter 1406 configured to cause ignition of the main fuel stream 1404 emitted from the main fuel nozzle(s) 1402.
  • Each burner module 1401 may respectively include a distal flame holder 102 configured to hold a combustion reaction supported by the main fuel stream 1404 when the distal flame holder 102 is at or above a predetermined temperature.
  • the predetermined temperature may be equal to or greater than a main fuel auto-ignition temperature.
  • Each burner module 1401 may include a pilot burner 1408 configured to pre-heat the distal flame holder 102 to the predetermined temperature, according to an embodiment.
  • the pilot burner 1408 of each burner module 1401 may include a continuous pilot burner that also may operate to ignite the main fuel.
  • the distal flame holder 102 may be separated from the main fuel nozzle(s) 1402 and from the pilot burner 1408 by respective non-zero distances (D1 , D2).
  • the low emissions modular burner system 1400 may include a common combustion air source 1405 configured to provide combustion air to each of the one or more burner modules 1401 , and a wall 1407 encircling all of the one or more burner modules 1401 , the wall 1407 being configured to laterally contain combustion fluids corresponding to the one or more burner modules 1401 .
  • the distal flame holder 102 is configured to hold a combustion reaction supported by the main fuel stream 1404 when the distal flame holder 102 is at or above the main fuel auto-ignition temperature.
  • each pilot burner 1408 includes a continuous pilot burner.
  • the pilot burner 1408 is configured selectively to output heat at any of a plurality of heating rates.
  • At least one heating rate may be selected to cause a rise in sensible temperature of the distal flame holder 102 to the predetermined operating temperature, and at least one other heating rate may be selected to cause the pilot burner 1408 to maintain a pilot flame function while a majority of total fuel consumed per unit of time is provided by the main fuel source 1402.
  • the common combustion air source 1405 is configured to provide natural draft combustion air to each burner module (1401 ) of the one or more burner modules 1401.
  • FIG. 15 is a diagram of a control circuit 1512 for use in the control system 1412 of FIG. 14, according to an embodiment.
  • the low emissions modular burner system 1400 further includes one or more separate main fuel valves 1410 for each burner module 1401 , each main fuel valve 1410 including separate main fuel valve actuators configured to operate responsive to receiving control signals, and further includes a control system 1412 configured to output respective control signals to each of the separate main fuel valve actuators.
  • the control system 1412 further includes an interface 1514 (see FIG. 15) between the control system 1412 and an input channel.
  • the input channel may include a physical (e.g., electrically conductive) connection or a wireless connection.
  • the interface 1514 may include a network interface and/or a hardware interface such as, but not limited to, a USB interface, a PID controller interface, a relay interface, a radio interface, a WiFi interface, a Bluetooth interface, etc.
  • the interface 1514 includes an interface to one or more sensors disposed to sense physical parameters related to each burner module 1401 and environs. Sensors (e.g., 1414 in FIG. 14) and operation thereof, may include capacitance coupled (e.g., patch) electrodes (which may alternatively be referred to as antennas) cooperating to emit and receive a radio frequency signal across a region intended to hold a combustion reaction.
  • capacitance coupled e.g., patch
  • a change in capacitance corresponds to a change in charged species concentration, which has been found to be covariant with the presence or absence of combustion.
  • the electrodes may be disposed in sufficient number, and be positioned, to provide a tomographic scan of the combustion region.
  • the sensors 1414 may be connected to the control system 1412 by a communication channel 1415.
  • the communication channel may wired (e.g., electrically conductive).
  • the communication channel 1415 may provide a voltage and/or current to electrodes of the sensors 1414.
  • the interface 1514 may be configured to receive a signal corresponding to a burner capacity requirement.
  • the control system 1412 may further include one or more burner module sensor inputs 1515a, 1515b, each of the one or more burner module sensor inputs 1515a, 1515b being configured to receive a signal corresponding to a burner module status, wherein the burner module status is provided by sensor hardware 1414.
  • the control system 1412 may further include a microcontroller or other logic processor 1516, a computer readable memory 1518, and a module sequencer 1520 (which may optionally be embodied as or by the logic processor 1516 and the computer readable memory 1518 when executing module sequencing functions) configured to select a subset of the one or more burner modules 1401 for ignition.
  • the control system 1412 may further include a respective one or more main fuel valve driver outputs, each operatively coupled to one of the separate main fuel valve actuators 1410.
  • the one or more burner module sensor inputs 1515a, 1515b are configured to receive input from one or more sensors, such as the sensor hardware 1414, or from one or more sensors external to the burner module(s) (1401 ).
  • the one or more sensors may include a demand sensor including one or more of a condensate pressure sensor, a heating energy demand sensor, and a condensate presence sensor.
  • a control circuit 1512 may include a module sequencer 1520.
  • the module sequencer 1520 may include a state machine configured to changeably sequence an actuation of the one or more burner modules 1401. For example, it may be desirable to periodically change an assignment of the burner modules to different positions in an actuation sequence in accord with demand.
  • a last module turned on in the previous module sequence may also operate as the first/only module turned on during a turn-down state.
  • the assignment of burner modules 1401 need not be identical with respect to capacity, age (e.g., cycle count), and design.
  • a start-up sequence may be at least partially identical with each base demand/surge capacity cycle.
  • the inventors contemplate various arrangements, actuation sequences, and selections of the assignment of burner modules 1401 may offer specific
  • the low emissions modular burner system 1400 further includes a run sequencer 1522.
  • the control circuit 1512 may include the run sequencer 1522.
  • the run sequencer 1522 may include a state machine configured to sequence steps in a burner module start-up schedule for one or more of the burner modules 1401. Start-up schedules may be stored in the memory 1518 and periodically updated via the interface 1514 that includes a network interface. Illustrative methods and aspects for start-up sequencing are described with respect to several of the other figures included herein.
  • control circuit 1512 (of control system 1412 of FIG. 14) of the low emissions modular burner system 1400 further includes an actuator driver module 1524.
  • the control circuit 1512 may include the actuator driver module 1524.
  • the actuator driver module 1524 may be configured to provide the respective control signals to each of the separate valve actuators.
  • the actuator driver module 1524 may include a state machine configured to load a driver shift register enable bit for amplification by a power module 1526, responsive to data from a start sequencer. Signals to/from the power module 1526 may be respectively coupled to actuatable main fuel valve(s) 1410, via connection(s) 1411. Similarly, actuatable pilot fuel valve(s) 1416may be respectively coupled to the power module 1526 via connection(s) 1417.
  • Sensors 1414 are described herein as performing sensory functions or functioning as signal outputs.
  • the power module 1526 may be employed to amplify such signal, e.g., for the aforementioned emission and receipt of radio frequency signals across a combustion region.
  • sensors 1414 may provide a signal for generating data, e.g., a flame tomogram.
  • dedicated sensor inputs 1515a, 1515b may be utilized.
  • the sensors 1414 may provide a subset of many data signals that communicate via interface 1514 of the control circuitry 1512.
  • the interface 1514 may provide wireless or wired connections using various communication protocols, which may permit the sensors 1414 to communicate via a standard method such as USB, WiFi, ethernet, or the like.
  • the low emissions modular burner system is configured to provide the low emissions modular burner system
  • the 1400 may further include a demand module 1528.
  • demand for system capacity is received in substantially real time via a network interface included in the interface 1514.
  • the demand module 1528 may be configured to supervise automatic operation of the one or more burner module(s)
  • the demand module 1528 may consist essentially of a data value in a register of the memory 1518.
  • the demand module 1528 may include a real time clock and, as data, a scheduled system capacity.
  • the demand module 1528 may operate as a supervisory state configured to automatically operate the modular burner system 1400 according to seasonal and/or periodic demand dynamics.
  • operation of the interface 1514 may be more crucial.
  • portions of the module sequencer 1520 may be virtualized and cloud-accessed.
  • the logic processor 1516 is configured to read and execute computer executable instructions supported by a non-transitory computer readable memory 1518 to receive capacity input data corresponding to the burner capacity requirement signal, read module status sensor data from sensor(s) corresponding to at least one burner module to verify that a selected one or more of the burner module(s) 1401 is ready for firing, select the subset of the one or more burner modules 1401 for firing, and drive at least one of the separate main fuel valve (1410) actuators corresponding to the selected one or more burner module(s) to open so as to provide fuel to a combustion reaction supported by the one or more burner module(s)1401.
  • control system 1412 further includes a demand sensor.
  • the demand sensor may include a heating energy demand sensor.
  • each burner module 1401 further includes a pilot fuel source configured to provide a pilot fuel, a pilot fuel igniter (e.g., 1406) configured to ignite a flow of the pilot fuel, and a distal pilot or start-up burner (e.g., constituting pilot burner 1408) 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 temperature of the distal flame holder 102 to the pre
  • the predetermined temperature is equal to or greater than a main fuel auto-ignition temperature.
  • pilot pilot burner, distal pilot and start-up burner and pre-heating apparatus shall be considered synonymous unless context dictates otherwise.
  • the main igniter 1406 comprises the distal pilot. According to another embodiment, the main igniter 1406 includes the distal flame holder 102 when the distal flame holder 102 is heated to the pre
  • the predetermined temperature is the main fuel auto-ignition temperature.
  • the distal pilot burner 1408 is configured to be controlled to provide the pilot flame sized to raise the distal flame holder 102 to the pre-determined temperature during a burner module start-up cycle, and to not provide the pilot flame sized to raise the distal flame holder 102 to the pre determined temperature at times other than during the burner module start-up cycle.
  • the distal pilot burner 1408 is configured to decrease to a pilot flame capacity at times other than during the burner module start-up cycle.
  • the distal pilot burner 1408 is configured to stop supporting a combustion reaction at times other than during the burner module start-up cycle.
  • the distal pilot burner 1408 may be disposed adjacent to the distal flame holder 102, and the distal pilot burner 1408 is controlled to be decreased to a pilot flame capacity at times other than during the burner module start-up cycle.
  • the pilot burner 1408 is disposed adjacent to the distal flame holder 102, and the distal pilot output is selected to maintain a constant capacity at all times during operation.
  • the pilot burner 1408 is configured to guarantee combustion of the main fuel, e.g., when the distal flame holder 102 does not support a combustion reaction.
  • the main fuel may be a hydrocarbon gas.
  • the pilot fuel may be one or more of hydrogen, natural gas or propane. According to embodiments, the pilot fuel and the main fuel may consist essentially of the same fuel.
  • a modular burner 1401 includes a housing 1403 having a combustion air inlet at a base.
  • Each burner module 1401 may include an inlet configured to be coupled to a main fuel supply and to receive combustion air via the housing 1403, a distal flame holder 102 positioned inside the housing 1403, and a main fuel nozzle 1402 configured to receive a flow of main fuel from the inlet, and to emit a main fuel stream toward the distal flame holder 102.
  • each of the one or more burner modules 1401 is configured to be freestanding, supported only by a coupling at the inlet.
  • the burner module 1401 is configured to be coupled to the burner and to be supported thereby.
  • the main fuel nozzle is one of a plurality of main fuel nozzles 1402, each of the main fuel nozzles 1402 configured to receive a flow of the main fuel from the inlet, and to emit a main fuel stream 1404 toward a respective portion of the distal flame holder 102.
  • the modular burner 1401 further includes a plurality of the main fuel valves 1410 operatively coupled between a common fuel line and a respective one of the plurality of main fuel nozzles 1402 and
  • FIG. 14 illustrates a main fuel valve 1410 shared by each of the main fuel nozzles 1402, an embodiment may include a separate— and separately controllable— main fuel valve 1410 for each main fuel nozzle 1402.
  • the modular burner 1401 further includes a distal pilot burner 1408 positioned between the distal flame holder 102 and the main fuel nozzle(s) 1402 for each burner module.
  • the modular burner 1401 may be a retrofit burner positioned within the housing 1407, the retrofit burner including the distal flame holder 102 and the main fuel nozzle(s) 1402.
  • Each distal pilot burner 1408 may include a plurality of pilot nozzles arranged in an array.
  • the distal pilot burner 1408 is configured to support a pilot flame between the distal pilot burner 1408 and the distal flame holder 102.
  • the main fuel nozzle(s) 1402 may include an aperture having a size that is variable.
  • the main fuel nozzle(s) 1402 may be configured to regulate a velocity of the main fuel stream.
  • the modular burner 1401 further includes an actuator operatively coupled to the main fuel nozzle(s) 1402 and configured to control the size of the aperture.
  • the main fuel nozzle(s) 1402 may each include a main nozzle outlet and a control element, the control element being positioned to occlude some portion of the main nozzle outlet, and wherein movement of the control element varies a degree to which the main nozzle outlet is occluded by the control element.
  • each burner module has a heating capacity of about 8 MBtu/Hr.
  • FIG. 16 is a block diagram of a burner system 1600, according to an embodiment.
  • the burner system 1600 includes a distal flame holder 1602 (corresponding to distal flame holder 102 described herein), a fuel and oxidant source 1620, and a mixing tube 1610.
  • the fuel and oxidant source 1620 may include an oxidant conduit 1604 for delivery of an oxidant 1606a, and one or more main fuel nozzle(s) 1618 for main delivery of a fuel 1606b.
  • the fuel 1606b and the oxidant 1606a mix in the mixing tube 1610 en route to the distal flame holder 1602, creating a fuel and oxidant mixture 1607.
  • the distal flame holder 1602 is disposed and oriented to receive and (when at an operating temperature) to ignite the fuel and oxidant mixture 1607.
  • the oxidant conduit 1604 provides a pathway for the oxidant 1606a (e.g., air), and directs the oxidant 1606a toward the distal flame holder 1602.
  • the main fuel nozzle(s) 1618 direct the fuel 1606b toward the distal flame holder 1602.
  • the main fuel nozzle(s) 1618 may receive the fuel 1606b from a fuel reservoir or pipeline (not shown, each or both referred to herein as a fuel supply) via a main fuel supply line 1608.
  • the burner system 1600 may include a single main fuel nozzle 1618 or a plurality of the main fuel nozzle(s) 1618, each disposed and configured as described herein.
  • the fuel 1606b emitted by the main fuel nozzle(s) 1618, and the oxidant 1606a emitted by the oxidant conduit 1604 become mixed as they travel toward the distal flame holder 1602.
  • the fuel 1606b and the oxidant 1606a achieve a sufficiently uniform fuel and oxidant mixture 1607 (see also element 706 in FIG. 7) to permit efficient and uniform combustion within the distal flame holder 1602 at the operating temperature.
  • the burner system 1600 may include a pilot burner 1612.
  • the pilot burner 1612 disposed proximate the distal flame holder and provides a pilot flame which may maintain ignition of the fuel and oxidant mixture 1607.
  • the pilot burner 1612 may receive fuel from a pilot fuel supply line 1614. Alternatively, the pilot burner 1612 may be in fluid connection with the main fuel supply line 1608.
  • the mixing tube may be disposed a predetermined distance from a floor of the burner system, and may be configured to receive at least the combustion air via the oxidant conduit 1604.
  • a source of flue gas diluent 1616 is contemplated.
  • the inventors have observed that the introduction of a mixing tube facilitates a recirculation of flue gas— as a substantial flue gas diluent— from downstream of the distal flame holder 1602.
  • the flue gas 1616 is educed to a proximal end (i.e. , the main nozzle end) of the mixing tube 1610 by a flow of main fuel and combustion oxidant between the main fuel nozzle(s) 1618 and the distal flame holder 1602 through the mixing tube 1610.
  • the recirculated flue gas 1616 mixes with the fuel and the combustion air before reaching the distal flame holder 1602.
  • the non-reactive elements of the resulting mixture minimize a potential for flashback upstream from the distal flame holder 1602 while permitting additional combustion of the reactive elements of the flue gas, thus reducing, e.g., NOx and other potential pollutants.
  • a burner system 1700 may include a distal flame holder 1602, a plurality of main fuel nozzles 1618, one or more distal pilot burners 1704 (e.g., corresponding to the pilot nozzle(s) 1612), and a mixing tube 1710.
  • the main fuel nozzles 1618 may be arranged in fluid connection with a main fuel source 1732.
  • flow of main fuel from the main fuel source 1732 may be controlled via a main fuel control valve 1736.
  • the one or more distal pilot burners 1704 may be arranged in fluid connection with a pilot fuel source 1730.
  • flow of pilot fuel from the pilot fuel source 1730 may be controlled via a pilot fuel control valve 1734.
  • the distal pilot burner(s) 1704 may be configured to support a pilot flame by outputting a pilot fuel received via a pilot fuel pipe 1712 from the pilot fuel source 1730.
  • the pilot fuel pipe 1712 may be disposed inside the mixing tube 1710 or— advantageously for maintenance, temperature regulation, etc.— outside the mixing tube 1710.
  • the pilot fuel pipe 1712 may form a portion of a support for the mixing tube 1710.
  • the distal pilot burner(s) 1704 may be supported by and receive fuel via the pilot fuel pipe 1712.
  • the pilot fuel pipe 1712 extends into the furnace volume 1701 via the opening 1740 in the floor 1738 of the furnace.
  • Each distal pilot burner 1704 may include a pilot manifold formed in any of several shapes.
  • the pilot manifold is formed in a Y shape. See also the discussion above corresponding to, e.g., FIGS. 3-6 with respect to pilot burner configurations.
  • each distal pilot burner 1704 includes one or more manifolds that define a plurality of fuel orifices 1718 having a large collective area to collectively support a low momentum pilot flame (not shown).
  • the main fuel output by the main fuel nozzles 1618 and combustion air form a combustible mixture that expands in breadth as it flows from a proximal position of the main fuel nozzles 1618 to the distal position of the distal pilot burner(s) 1704.
  • the plurality of fuel orifices 1718 may be disposed across the furnace volume 1701 sufficiently broadly to cause contact of the pilot flame with the main fuel and combustion air mixture across the breadth of the combustible mixture.
  • the main fuel nozzles 1618 may be configured to output fuel in co-flow with the air.
  • a distal pilot burner 1704 includes a fuel manifold having a plurality of segments 1719 joined together, each segment 1719 having a plurality of fuel orifices 1718 configured to pass fuel from inside the fuel manifold to the furnace volume 1701.
  • the plurality of segments 1719 may be formed as respective tubes configured to freely pass the fuel delivered from the pilot fuel pipe 1712 into the fuel manifold.
  • at least a portion of the tubes is arranged as spokes radiating from a center disposed substantially at a centerline along the axis.
  • at least a portion of the tubes is arranged as an“X”, a rectangle, an ⁇ ”, a wagon wheel, or a star.
  • a distal pilot burner 1704 includes a manifold including a curvilinear tube.
  • the curvilinear tube is arranged as a spiral,
  • the mixing tube 1712 may be arranged about a longitudinal axis of flow between the main fuel nozzles 1618 and the distal flame holder 1602.
  • the mixing tube 1710 may include a bell-shaped or flared portion 1714 at an end proximate the main fuel nozzles 1618.
  • the bell-shaped or flared portion 1714 may be disposed a predetermined distance from a floor 1738 of the burner system, and may be configured to receive at least the combustion air via an opening 1740 in the floor 1738.
  • a source of flue gas diluent is contemplated.
  • the inventors have observed that the introduction of a mixing tube facilitates a recirculation of flue gas— as a substantial flue gas diluent— from downstream of the distal flame holder 1602, and/or including combustion products of a pilot flame held at the pilot burner 1704.
  • the flue gas is educed to a proximal end (i.e., the floor end) of the mixing tube 1710 by a flow of main fuel and combustion oxidant between the floor 1738 and the distal flame holder 1602 through the mixing tube 1710.
  • the recirculated flue gas mixes with the fuel and the combustion air before reaching the distal flame holder 1602.
  • the non reactive elements of the resulting mixture minimize a potential for flashback upstream from the distal flame holder 1602 while permitting additional
  • the mixing tube 1710 may have a diameter appropriate for providing a mixture of fuel and oxidant (e.g., fuel and oxidant mixture 1607) to at least most of the input face (e.g., input face 712 of FIG. 7) of the distal flame holder 1602.
  • the opening at the proximal end of the mixing tube 1710, closest to the main fuel nozzles 1618, may have a largest diameter sized in correspondence to either the opening 1740 in the floor 1738 or sufficient to receive fuel input from each of the main fuel nozzles 1618.
  • the largest diameter of the bell-shaped or flared portion 1714 may correspond to either the opening 1740 in the floor 1738 or may correspond to at least the farthest distance between main fuel nozzles 1618.
  • a length of the mixing tube may be selected to permit sufficient time and/or distance for appropriate mixing of the fuel and the oxidant before reaching the distal flame holder 1602.
  • a burner system includes a distal flame holder configured to hold a combustion reaction of a fuel and an oxidant, and an oxidant conduit configured to direct the oxidant toward the distal flame holder.
  • the burner system includes a main fuel nozzle oriented to direct a flow of a main fuel into a combustion volume for mixture with the oxidant in a dilution region between the main fuel nozzle and the distal flame holder when a temperature of the distal flame holder is above a predetermined temperature, and a mixing tube disposed in the dilution region, and being open from a mixing tube inlet to a mixing tube outlet between the main fuel nozzle and the distal flame holder, the mixing tube being formed to cause flow of the oxidant and fuel to educe flue gas into the mixing tube for mixing with fuel and oxidant.
  • the mixing tube is configured to cause the flow of oxidant and fuel to form a flue gas recirculation path.
  • the flue gas recirculation path may be external to the combustion chamber.
  • the burner system further includes a pilot burner configured to support a pilot flame between the outlet of the mixing tube and the distal flame holder.
  • the mixing tube includes a flared portion at the mixing tube inlet.
  • the flue gas recirculation path may include at least a toroidal volume between the mixing tube and a wall of the combustion volume.
  • the flue gas may be educed into the fuel and oxidant stream at the mixing tube inlet for dilution of the fuel and oxidant stream.
  • the burner system further a continuous pilot disposed adjacent to the distal flame holder, the continuous pilot being
  • a controller operatively coupled to the main fuel source, the controller configured to receive an indication of a temperature of the distal flame holder and to control the flow of the main fuel responsive to the indication of the temperature.
  • the burner system further includes a mixing tube support structure configured to support the mixing tube, the mixing tube support structure configured to be supported by a surface defining the
  • FIG. 18 is an illustration showing a horizontally-fired burner system 1800 including a distal pilot burner 1804 and a mixing tube 1810, according to an embodiment.
  • the inventors have observed, in a variety of furnace applications, undesirable combustion oscillations occurring between a distal flame holder 1802 and a fuel and oxidant (combustion air) source 1820.
  • a fuel and oxidant (combustion air) source 1820 Although not necessarily restricted to a confined furnace configuration— e.g., a water heater, boiler, or once-through steam generator (OTSG)— such applications are representative environments that can permit such combustion oscillations.
  • OTSG once-through steam generator
  • insufficiently and/or non-uniformly cooled oxidant e.g., flue gas
  • the flashback reduces the efficiency of the burner 1800 at least in part because heat from this premature combustion is not (in a gas-fired burner) radiant heat, is not sufficiently absorbed by the distal flame holder 1802 and/or boiler tubes, and is thus wasted. Combustion products from the flashback can dilute the mixture and thus temporarily snuff the flashback combustion. Hence the oscillating nature of flashback.
  • the distal pilot burner 1804 may be configured for preheating of the distal flame holder 1802 and/or to address undesirable flashback by providing a constant and/or controllable ignition source for the fuel and combustion air mixture at a position sufficiently near to the distal flame holder 1802 to provide heat benefits from a diffusion pilot flame 1808 to the distal flame holder 1802.
  • the distal pilot burner 1804 may be disposed adjacent to the distal flame holder 1802 in a combustion volume 1801.
  • the distal flame holder 1802 may be formed of a plurality of columns including refractory materials.
  • the distal pilot burner 1804 is configured to maintain a diffusion pilot flame 1808 during combustion of main fuel in a combustion reaction held by the distal flame holder 1802.
  • the main fuel and the combustion air may be supplied by the fuel and combustion air source 1820 disposed a distance upstream from the distal pilot burner 1804.
  • the distance between main fuel nozzles 1806 of the fuel and combustion air source 1820 and the distal pilot burner 1804 may be at least 50 times a diameter of the main fuel nozzles 1806, at least 100 times a diameter of the main fuel nozzles 1806, or at least 200 times the diameter of the main fuel nozzles 1806.
  • the horizontally-fired burner system 1800 may include a mixing tube 1810 disposed between the fuel and combustion air source 1820 and the distal pilot burner 1804.
  • the mixing tube 1810 may include a flared portion at an opening proximal to the fuel and combustion air source 1820.
  • the mixing tube 1810 directs a flow of fuel and combustion air from the fuel and combustion air source 1820 toward the distal pilot burner 1804 and the distal flame holder 1802. Flue gas 1816 may be recirculated outside the mixing tube 1810 to enter the proximal end thereof for mixture with the fuel and the combustion air.
  • the horizontally-fired burner system 1800 includes the distal pilot burner 1804 disposed adjacent to the plurality of columns.
  • the distal pilot burner 1804 may be configured to successively provide a pre-heating flame to raise a temperature of the distal flame holder 1802 to at least an auto-ignition temperature of main fuel prior to introduction of the main fuel, and to maintain the diffusion pilot flame 1808 during combustion of the main fuel in the combustion reaction held by the distal flame holder 1802.
  • the distal pilot burner 1804 may be configured to support a large combustion reaction during pre-heating of the distal flame holder 1802 and to support a smaller combustion reaction during subsequent combustion of the main fuel.
  • a horizontally-fired burner system disclosed may include a controller 1812 (corresponding to, e.g., control system 1412 described herein) configured to receive sensor inputs, e.g., from sensor 1815, and to control output of fuel and combustion air.
  • the controller 1812 may control use of the distal pilot burner 1804.
  • the controller 1812 may control an actuator (not shown) that controls rate and/or amount of fuel provided to the distal pilot burner 1804 based on, e.g., sensor inputs showing temperature of the distal flame holder 1802, presence or absence or quality of a flame at the distal flame holder 1802 and/or at the distal pilot burner 1804.
  • combustion system in accordance with principles of the present disclosure can include sensors and actuators other than those disclosed herein, other combinations of sensors and actuators, as well as other kinds of actions to be taken by the controller (e.g., 730 of FIG. 7) responsive to sensor signals. All such other sensors, actuators, combinations, and actions fall within the scope of the present disclosure.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)

Abstract

Selon un mode de réalisation, la présente invention concerne un système de brûleur qui comprend un brûleur pilote disposé dans un four à une position distale le long d'un axe principal de flux d'air de combustion et de combustible, et une ou plusieurs buses principales de combustible disposées à une position proximale le long de l'axe principal de flux d'air de combustion et de combustible. Le brûleur pilote est conçu pour supporter une flamme pilote et la ou les buses de combustible principales sont conçues pour supporter une flamme principale en contact avec la flamme pilote. Le brûleur pilote est disposé de manière à provoquer l'allumage du combustible principal et de l'air de combustion par la flamme pilote.
PCT/US2020/031966 2019-05-07 2020-05-07 Brûleur pilote stabilisé WO2020227581A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
CN202080034369.8A CN113795713A (zh) 2019-05-07 2020-05-07 引燃稳定燃烧器
EP20803052.8A EP3966503A4 (fr) 2019-05-07 2020-05-07 Brûleur pilote stabilisé
US17/521,722 US20220205633A1 (en) 2019-05-07 2021-11-08 Pilot stabilized burner

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US201962844669P 2019-05-07 2019-05-07
US62/844,669 2019-05-07
US16/782,861 US20210239317A1 (en) 2020-02-05 2020-02-05 Low emission modular flare stack
US16/782,861 2020-02-05

Related Child Applications (1)

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US17/521,722 Continuation-In-Part US20220205633A1 (en) 2019-05-07 2021-11-08 Pilot stabilized burner

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WO2020227581A1 true WO2020227581A1 (fr) 2020-11-12

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EP (1) EP3966503A4 (fr)
CN (1) CN113795713A (fr)
WO (1) WO2020227581A1 (fr)

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US20120270161A1 (en) * 2006-06-14 2012-10-25 John Zink Company, Llc Coanda gas burner apparatus and methods
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US5551869A (en) * 1995-03-07 1996-09-03 Brais, Martres Et Associes Inc. Gas staged burner
WO2015070188A1 (fr) * 2013-11-08 2015-05-14 Clearsign Combustion Corporation Système de combustion avec commande de position de flamme
CN107923613B (zh) * 2015-09-14 2019-09-17 克利尔赛恩燃烧公司 穿孔火焰保持器的部分转变的火焰启动
CN107314371A (zh) * 2016-04-26 2017-11-03 克利尔赛恩燃烧公司 用于包括有孔火焰保持器的燃烧器的燃料喷嘴组件
WO2018236762A1 (fr) * 2017-06-19 2018-12-27 Clearsign Combustion Corporation Pilote de brûleur à stabilisateur de flamme
CN109442412A (zh) * 2018-12-17 2019-03-08 上海华之邦科技股份有限公司 一种结构新型的低氮燃烧装置

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US6074200A (en) * 1998-01-20 2000-06-13 Gas Research Institute Burner apparatus having an air dam and mixer tube
US6007325A (en) * 1998-02-09 1999-12-28 Gas Research Institute Ultra low emissions burner
US20120270161A1 (en) * 2006-06-14 2012-10-25 John Zink Company, Llc Coanda gas burner apparatus and methods
JP2009109180A (ja) * 2007-10-29 2009-05-21 General Electric Co <Ge> 希薄予混合半径方向流入マルチアニュラ多段ノズルの缶アニュラ型デュアル燃料燃焼器
US20150276212A1 (en) * 2013-02-14 2015-10-01 Clearsign Combustion Corporation Burner with a perforated flame holder and pre-heat apparatus

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Publication number Publication date
CN113795713A (zh) 2021-12-14
EP3966503A1 (fr) 2022-03-16
EP3966503A4 (fr) 2023-06-07

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