WO2018034947A1

WO2018034947A1 - Perforated flame holder support member for structural integrity

Info

Publication number: WO2018034947A1
Application number: PCT/US2017/046372
Authority: WO
Inventors: Douglas W. KARKOW; Donald Kendrick; Joseph Colannino; Jesse DUMAS; Jonathan P. DEES; James K. DANSIE; Christopher A. Wiklof
Original assignee: Clearsign Combustion Corporation
Priority date: 2016-08-18
Filing date: 2017-08-10
Publication date: 2018-02-22
Also published as: CN109416175A; EP3500797A4; EP3500797A1

Abstract

A furnace includes a perforated flame holder formed from an array of tiles. The perforated flame holder is stabilized by a support member extending between at least adjacent tiles. Elongated support members may be positioned to extend through each of the tiles in a respective column of the array of tiles.

Description

PERFORATED FLAME HOLDER SUPPORT MEMBER FOR STRUCTURAL INTEGRITY

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority benefit from U.S. Provisional Patent Application No. 62/376,776, entitled "PERFORATED FLAME HOLDER

SUPPORT MEMBER FOR STRUCTURAL INTEGRITY," filed August 18, 2016 (docket number 2651 -283-02); which, to the extent not inconsistent with the disclosure herein, is incorporated by reference.

SUMMARY

According to an embodiment, a row of burner tiles is provided, each having a receiving feature extending laterally therethrough. A support member extends through the receiving feature of each of the burner tiles. The burner tiles can be, for example, perforated flame holders.

According to another embodiment, each of the burner tiles includes a second receiving feature extending parallel to the first receiving feature, and a second support member extends through the second receiving feature of each of the burner tiles.

According to an embodiment, a quantity of bonding agent is positioned between the burner tiles of each adjacent pair of burner tiles of the row.

According to an alternative embodiment, the bonding agent is omitted, and the tiles are held in their relative positions by the support member or members. According to an embodiment, the support member is under tension, at least while the row of burner tiles is not at operating temperature. According to an embodiment, the tension is maintained by a fastener at each end of the support member.

According to an embodiment, the support member is generally circular in cross section.

According to an embodiment, the burner tiles of the row are aligned such that a respective face of each burner tile lies substantially in a same plane.

According to an alternative embodiment, the burner tiles are positioned, relative to each other, such that the row has a substantially arcuate shape.

According to an embodiment, a perforated flame holder of a furnace is provided, including an array of burner tiles with a support member extending through the burner tiles of each row of the array of burner tiles. One or more additional support members can be positioned to extend through each of the burner tiles of a respective column of the array.

According to an embodiment, a first face of each of the burner tiles of the array of burner tiles lies in a common plane. According to an alternative embodiment, a number of the burner tiles of the array of burner tiles are offset longitudinally with respect to others of the burner tiles of the array.

According to an embodiment, a method of assembly of the perforated flame holder is provided, in which each row of burner tiles is separately installed into a furnace, such that a final assembly of the perforated flame holder is performed inside the furnace.

According to an alternative embodiment, rows of burner tiles are coupled together outside the furnace to form larger segments of the perforated flame holder, which are then separately installed in the furnace to form the perforated flame holder.

According to another alternative embodiment, all of the rows of burner tiles are coupled together outside the furnace, then the fully assembled perforated flame holder is installed in the furnace. According to an embodiment, a perforated flame holder mounting structure is provided in the furnace, which includes coupling features configured to receive ends of the support members of each of the rows, thereby supporting the perforated flame holder within the furnace.

According to an embodiment, a perforated flame holder is provided, which includes a plurality of burner tiles. Support members extend between adjacent pairs of burner tiles in receiving features formed into facing lateral surfaces of each adjacent pair of burner tiles.

According to an embodiment, the receiving features are relieved at an angle selected to distribute stress between the support members the respective burner tiles.

According to an embodiment, each of the support members includes a strain relief member positioned and configured to distribute stress between the respective support member and the respective pair of burner tiles.

According to an embodiment, the strain relief members include sleeves of fibrous ceramic material that is formed into a flexible tube.

According to an embodiment, each of the support members includes a plurality of ridges extending lengthwise thereon.

According to an embodiment, a combustion system includes a fuel and oxidant source configured to output a fuel and an oxidant, and a perforated flame holder including a group of burner tiles arranged side by side. Each burner tile includes an input face aligned to receive the fuel and the oxidant, an output face, and a plurality of perforations extending between the input face and the output face. The perforated flame holder is configured to support a combustion reaction of the fuel and the oxidant within the perforations of the burner tiles. A first burner tile of the plurality of burner tiles includes a receiving feature. The combustion system includes a first support member extending into the first burner tile via the receiving feature and holding the perforated flame holder in alignment to receive the fuel and oxidant into the perforations.

According to an embodiment, a combustion system includes a fuel and oxidant source configured to output a fuel and an oxidant, and a perforated flame holder including a first group of burner tiles arranged side by side. Each burner tile of the first group includes an input face aligned to receive the fuel and the oxidant, an output face, a plurality of perforations extending between the input face and the output face, and a receiving feature. The perforated flame holder is configured to support a combustion reaction of the fuel and the oxidant within the perforations. The combustion system includes a plurality of support members, each extending into a respective burner tile of the first group via the receiving feature and supporting the perforated flame holder in alignment to receive the fuel and oxidant.

According to an embodiment, a method includes outputting a fuel into a furnace volume, outputting an oxidant into the furnace volume, and supporting a perforated flame holder, including a plurality of burner tiles arranged side by side in alignment to receive the fuel and oxidant by passing a support member into at least one of the burner tiles via a receiving feature of the at least one burner tile. Each burner tile includes an input face, an output face, and a plurality of perforations extending between the input face and the output face. The method includes receiving the fuel and oxidant into the perforations of each burner tile and supporting a combustion reaction of the fuel and oxidant within the perforations of each burner tile.

According to an embodiment, a device includes a first burner tile and a support member. The first burner tile includes an input face, an output face, a plurality of perforations extending between the input face and the output face, and a receiving feature. The support member extends into the burner tile via the receiving feature, the support member includes a portion protruding from the burner tile. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagram of a burner system, including a perforated flame holder configured to hold a combustion reaction, according to an

embodiment.

FIG. 2 is a side sectional diagram of a portion of the perforated flame holder of FIG. 1 , according to an embodiment.

FIG. 3 is a flow chart showing a method, according to an embodiment, for operating a burner system that includes a perforated flame holder similar to the flame holder of FIGS. 1 and 2.

FIGS. 4-6 are perspective views of perforated flame holders, according to respective embodiments, each of which includes a plurality of burner tiles coupled together to form the perforated flame holder.

FIG. 7 is a perspective view of a portion of a combustion system that includes a perforated flame holder, according to an embodiment.

FIGS. 8A-8D are partial side-sectional diagrams showing details of portions of burner tiles with examples of support members and fasteners, according to respective embodiments.

FIG. 9 is a side elevation view of a row of burner tiles, according to an embodiment, in which the burner tiles are arranged in an arcuate configuration.

FIGS. 10 and 11 are perspective views of examples of perforated flame holders that can include the row of burner tiles of FIG. 9, according to respective embodiments.

FIG. 12 is a plan view of a perforated flame holder, according to another embodiment, which includes a plurality of hexagonal burner tiles.

FIG. 13A is a diagrammatic plan view of a perforated flame holder, according to an embodiment.

FIG. 13B is a detail of a perforated flame holder, according to an embodiment, taken from a position indicated in FIG. 13A at 13B.

FIG. 14A is a cross sectional diagram of a portion of a perforated flame holder, according to an embodiment, as viewed along lines 14A-14A in FIG. 13B. FIG. 14B is a cross sectional diagram of the perforated flame holder of FIG. 14A, as viewed along lines 14B-14B in FIG. 14A.

FIG. 15 is a cross sectional diagram of a portion of a perforated flame holder in a view that corresponds to the view of FIG. 14A, according to another embodiment.

FIG. 16A is a cross sectional diagram of a portion of a perforated flame holder in a view that corresponds to the view of FIG. 14A, according to an embodiment.

FIG. 16B is a cross sectional diagram of the perforated flame holder as viewed as viewed along lines 16B-16B in FIG. 16A, according to an embodiment.

FIG. 17 is a cross sectional diagram of a portion of a perforated flame holder, according to an embodiment, in a view that corresponds to the views of FIGS. 14B and 16B

FIG. 18 is a partially cut away perspective view of a portion of a perforated flame holder, according to another embodiment.

FIG. 19A is a simplified perspective view of a combustion system, including a reticulated ceramic perforated flame holder, according to an embodiment.

FIG. 19B is a simplified side sectional diagram of a portion of the reticulated ceramic perforated flame holder of FIG. 19A, according to an embodiment.

FIG. 20A is a perspective view of a burner tile including a support member coupled to the burner tile, according to an embodiment.

FIG. 20B is a side-sectional diagram showing details of a portion of a burner tile with a support member, according to an embodiment.

DETAILED DESCRIPTION In the following detailed description, reference is made to the

accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here.

In some of the drawings, two or more elements may be indicated by reference numbers of the same numerical value, but that include a letter that is different, such as, e.g., 406x and 406y. This is to enable the detailed description to differentiate between specific elements or groups of elements that are otherwise similar or identical. However, where the description refers more generally to all of the elements, the letters may be omitted from the description. Additionally, in other drawings, the letters may be omitted from references to the same or similar elements, where there is no need in the description to

differentiate between the elements.

FIG. 1 is a simplified diagram of a burner system 100, including a perforated flame holder 102 configured to hold a combustion reaction, according to an embodiment. As used herein, the terms perforated flame holder, perforated reaction holder, porous flame holder, porous reaction holder, duplex, and duplex tile shall be considered synonymous unless further definition is provided.

Experiments performed by the inventors have shown that perforated flame holders 102 described herein can support very clean combustion. Specifically, in experimental use of systems 100 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 temperatures typical of industrial furnace applications (1400 - 1600 °F). Moreover, these results did not require any extraordinary measures such as selective catalytic reduction (SCR), selective non-catalytic reduction (SNCR), water/steam injection, external flue gas recirculation (FGR), or other heroic extremes that may be required for conventional burners to even approach such clean combustion.

According to embodiments, the burner system 100 includes a fuel and oxidant source 103 disposed to output fuel and oxidant into a combustion volume 104 to form a fuel and oxidant mixture 106. As used herein, the terms fuel and oxidant mixture and fuel stream may be used interchangeably and considered synonymous depending on the context, unless further definition is provided. As used herein, the terms 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 104 and positioned to receive the fuel and oxidant mixture 106.

FIG. 2 is a side sectional diagram 200 of a portion of the perforated flame holder 102 of FIG. 1 , according to an embodiment. Referring to FIGS. 1 and 2, the perforated flame holder 102 includes a perforated flame holder body 108 defining a plurality of perforations 1 10 aligned to receive the fuel and oxidant mixture 106 from the fuel and oxidant source 103. As used herein, 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 1 10 are configured to collectively hold a combustion reaction 202 supported by the fuel and oxidant mixture 106.

The fuel can include hydrogen, a hydrocarbon gas, a vaporized

hydrocarbon liquid, an atomized hydrocarbon liquid, or a powdered or pulverized solid. 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). For example, in a process heater application the fuel can include fuel gas or byproducts from the process that include carbon monoxide (CO), hydrogen (H₂), and methane (CH₄). In another application the fuel can include natural gas (mostly CH₄) or propane (C3H8). In another application, 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.

According to an embodiment, the perforated flame holder body 108 can be bounded by an input face 1 12 disposed to receive the fuel and oxidant mixture 106, an output face 1 14 facing away from the fuel and oxidant source 103, and a peripheral surface 1 16 defining a lateral extent of the perforated flame holder 102. The plurality of perforations 1 10 which are defined by the perforated flame holder body 108 extend from the input face 1 12 to the output face 1 14. The plurality of perforations 1 10 can receive the fuel and oxidant mixture 106 at the input face 1 12. The fuel and oxidant mixture 106 can then combust in or near the plurality of perforations 1 10 and combustion products can exit the plurality of perforations 1 10 at or near the output face 1 14.

According to an embodiment, the perforated flame holder 102 is configured to hold a majority of the combustion reaction 202 within the

perforations 1 10. For example, on a steady-state basis, more than half the molecules of fuel output into the combustion volume 104 by the fuel and oxidant source 103 may be converted to combustion products between the input face 1 12 and the output face 1 14 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 202 may be output between the input face 1 12 and the output face 1 14 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. As used above, heat energy and thermal energy refer generally to the released chemical energy initially held by reactants during the combustion reaction 202. As used elsewhere herein, heat, heat energy and thermal energy correspond to a detectable temperature rise undergone by real bodies characterized by heat capacities. Under nominal operating conditions, the perforations 1 10 can be configured to collectively hold at least 80% of the combustion reaction 202 between the input face 1 12 and the output face 1 14 of the perforated flame holder 102. In some experiments, the inventors produced a combustion reaction 202 that was apparently wholly contained in the perforations 1 10 between the input face 1 12 and the output face 1 14 of the perforated flame holder 102. According to an alternative interpretation, the perforated flame holder 102 can support combustion between the input face 1 12 and output face 1 14 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 1 14 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 1 12 of the perforated flame holder 102.

While a "flame" is described in a manner intended for ease of description, it should be understood that in some instances, no visible flame is present.

Combustion occurs primarily within the perforations 1 10, but the "glow" of combustion heat is dominated by a visible glow of the perforated flame holder 102 itself. In other instances, the inventors have noted transient "huffing" or

"flashback" wherein a visible flame momentarily ignites in a region lying between the input face 1 12 of the perforated flame holder 102 and the fuel nozzle 1 18, within the dilution region D_D. Such transient huffing or flashback is generally short in duration such that, on a time-averaged basis, a majority of combustion occurs within the perforations 1 10 of the perforated flame holder 102, between the input face 1 12 and the output face 1 14. In still other instances, the inventors have noted apparent combustion occurring downstream from the output face 1 14 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 202 and output a portion of the received heat as thermal radiation 204 to heat-receiving structures (e.g., furnace walls and/or radiant section working fluid tubes) in or adjacent to the combustion volume 104. As used herein, 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 108.

Referring especially to FIG. 2, the perforated flame holder 102 outputs another portion of the received heat to the fuel and oxidant mixture 106 received at the input face 1 12 of the perforated flame holder 102. The perforated flame holder body 108 may receive heat from the combustion reaction 202 at least in heat receiving regions 206 of perforation walls 208. Experimental evidence has suggested to the inventors that the position of the heat receiving regions 206, or at least the position corresponding to a maximum rate of receipt of heat, can vary along the length of the perforation walls 208. In some experiments, the location of maximum receipt of heat was apparently between 1/3 and 1/2 of the distance from the input face 1 12 to the output face 1 14 (i.e., somewhat nearer to the input face 1 12 than to the output face 1 14). The inventors contemplate that the heat receiving regions 206 may lie nearer to the output face 1 14 of the perforated flame holder 102 under other conditions. Most probably, there is no clearly defined edge of the heat receiving regions 206 (or for that matter, the heat output regions 210, described below). For ease of understanding, the heat receiving regions 206 and the heat output regions 210 will be described as particular regions 206, 210.

The perforated flame holder body 108 can be characterized by a heat capacity. The perforated flame holder body 108 may hold thermal energy from the combustion reaction 202 in an amount corresponding to the heat capacity multiplied by temperature rise, and transfer the thermal energy from the heat receiving regions 206 to heat output regions 210 of the perforation walls 208. Generally, the heat output regions 210 are nearer to the input face 1 12 than are the heat receiving regions 206. According to one interpretation, the perforated flame holder body 108 can transfer heat from the heat receiving regions 206 to the heat output regions 210 via thermal radiation, depicted graphically as 204. According to another interpretation, the perforated flame holder body 108 can transfer heat from the heat receiving regions 206 to the heat output regions 210 via heat conduction along heat conduction paths 212. The inventors contemplate that multiple heat transfer mechanisms including conduction, radiation, and possibly convection may be operative in transferring heat from the heat receiving regions 206 to the heat output regions 210. In this way, the perforated flame holder 102 may act as a heat source to maintain the combustion reaction 202, even under conditions where a combustion reaction would not be stable when supported from a conventional flame holder.

The inventors believe that the perforated flame holder 102 causes the combustion reaction 202 to begin within thermal boundary layers 214 formed adjacent to walls 208 of the perforations 1 10. Insofar as 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. As the relatively cool fuel and oxidant mixture 106 approaches the input face 1 12, the flow is split into portions that respectively travel through individual perforations 1 10. The hot perforated flame holder body 108 transfers heat to the fluid, notably within thermal boundary layers 214 that progressively thicken as more and more heat is transferred to the incoming fuel and oxidant mixture 106. After reaching 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 202 occurs. Accordingly, the combustion reaction 202 is shown as occurring within the thermal boundary layers 214. As flow progresses, the thermal boundary layers 214 merge at a merger point 216. Ideally, the merger point 216 lies between the input face 1 12 and output face 1 14 that define the ends of the perforations 1 10. At some position along the length of a perforation 1 10, the combustion reaction 202 outputs more heat to the perforated flame holder body 108 than it receives from the perforated flame holder body 108. The heat is received at the heat receiving region 206, is held by the perforated flame holder body 108, and is transported to the heat output region 210 nearer to the input face 1 12, where the heat is transferred into the cool reactants (and any included diluent) to bring the reactants to the ignition temperature.

In an embodiment, each of the perforations 1 10 is characterized by a length L defined as a reaction fluid propagation path length between the input face 1 12 and the output face 1 14 of the perforated flame holder 102. As used herein, the term reaction fluid refers to matter that travels through a perforation 1 10. Near the input face 1 12, the reaction fluid includes the fuel and oxidant mixture 106 (optionally including nitrogen, flue gas, and/or other "non-reactive" species). Within the combustion reaction region, the reaction fluid may include plasma associated with the combustion reaction 202, molecules of reactants and their constituent parts, any non-reactive species, reaction intermediates

(including transition), and reaction products. Near the output face 1 14, the reaction fluid may include reaction products and byproducts, non-reactive gas, and excess oxidant.

The plurality of perforations 1 10 can be each characterized by a

transverse dimension D between opposing perforation walls 208. The inventors have found that stable combustion can be maintained in the perforated flame holder 102 if the length L of each perforation 1 10 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. Preferably, the length L is sufficiently long for thermal boundary layers 214 to form adjacent to the perforation walls 208 in a reaction fluid flowing through the perforations 1 10 to converge at merger points 216 within the perforations 1 10 between the input face 1 12 and the output face 1 14 of the perforated flame holder 102. In experiments, the inventors have found 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 108 can be configured to convey heat between adjacent perforations 1 10. The heat conveyed between adjacent perforations 1 10 can be selected to cause heat output from the combustion reaction portion 202 in a first perforation 1 10 to supply heat to stabilize a combustion reaction portion 202 in an adjacent perforation 1 10.

Referring especially to FIG. 1 , the fuel and oxidant source 103 can further include a fuel nozzle 1 18, configured to output fuel, and an oxidant source 120 configured to output a fluid including the oxidant. For example, the fuel nozzle 1 18 can be configured to output pure fuel. The oxidant source 120 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 122 configured to hold the perforated flame holder 102 at a dilution distance D_D away from the fuel nozzle 1 18. The fuel nozzle 1 18 can be configured to emit a fuel jet selected to entrain the oxidant to form the fuel and oxidant mixture 106 as the fuel jet and oxidant travel along a path to the perforated flame holder 102 through the dilution distance D_D between the fuel nozzle 1 18 and the perforated flame holder 102. Additionally or alternatively (particularly when a blower is used to deliver oxidant contained in combustion air), the oxidant or combustion air source can be configured to entrain the fuel and the fuel and oxidant travel through the dilution distance D_D. In some embodiments, a flue gas recirculation path 124 can be provided. Additionally or alternatively, the fuel nozzle 1 18 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 fuel nozzle 1 18 and the input face 1 12 of the perforated flame holder 102.

The fuel nozzle 1 18 can be configured to emit the fuel through one or more fuel orifices 126 having an inside diameter dimension that is referred to as "nozzle diameter." The perforated flame holder support structure 122 can support the perforated flame holder 102 to receive the fuel and oxidant mixture 106 at the distance D_D away from the fuel nozzle 1 18 greater than 20 times the nozzle diameter. In another embodiment, the perforated flame holder 102 is disposed to receive the fuel and oxidant mixture 106 at the distance D_D away from the fuel nozzle 1 18 between 100 times and 1 100 times the nozzle diameter. Preferably, the perforated flame holder support structure 122 is configured to hold the perforated flame holder 102 at a distance about 200 times or more of the nozzle diameter away from the fuel nozzle 1 18. When the fuel and oxidant mixture 106 travels about 200 times the nozzle diameter or more, the mixture 106 is sufficiently homogenized to cause the combustion reaction 202 to produce minimal NOx.

The fuel and oxidant source 103 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 perforated flame holder 102 and be configured to prevent flame flashback into the premix fuel and oxidant source.

The oxidant source, whether configured for entrainment in the combustion volume 104 or for premixing can include a blower configured to force the oxidant through the fuel and oxidant source 103.

The support structure 122 can be configured to support the perforated flame holder 102 from a floor or wall (not shown) of the combustion volume 104, for example. In another embodiment, the support structure 122 supports the perforated flame holder 102 from the fuel and oxidant source 103. Alternatively, the support structure 122 can suspend the perforated flame holder 102 from an overhead structure (such as a flue, in the case of an up-fired system). The support structure 122 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 108. 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 122 can be configured to support the plurality of perforated flame holder sections. The perforated flame holder support structure 122 can include a metal superalloy, a cementatious, and/or ceramic refractory material. In an embodiment, 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 1 16 at least twice a thickness dimension T between the input face 1 12 and the output face 1 14. In another embodiment, the perforated flame holder 102 can have a width dimension W between opposite sides of the peripheral surface 1 16 at least three times, at least six times, or at least nine times the thickness dimension T between the input face 1 12 and the output face 1 14 of the perforated flame holder 102.

In an embodiment, the perforated flame holder 102 can have a width dimension W less than a width of the combustion volume 104. This can allow the flue gas circulation path 124 from above to below the perforated flame holder 102 to lie between the peripheral surface 1 16 of the perforated flame holder 102 and the combustion volume wall (not shown).

Referring again to both FIGS. 1 and 2, the perforations 1 10 can be of various shapes. In an embodiment, the perforations 1 10 can include elongated squares, each having a transverse dimension D between opposing sides of the squares. In another embodiment, the perforations 1 10 can include elongated hexagons, each having a transverse dimension D between opposing sides of the hexagons. In yet another embodiment, the perforations 1 10 can include hollow cylinders, each having a transverse dimension D corresponding to a diameter of the cylinder. In another embodiment, the perforations 1 10 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 1 12 to the output face 1 14. In some embodiments, the perforations 1 10 can each have a lateral dimension D equal to or greater than a quenching distance of the flame based on standard reference conditions. Alternatively, the perforations 210 may have lateral dimension D less than a standard reference quenching distance. In one range of embodiments, each of the plurality of perforations 1 10 has a lateral dimension D between 0.05 inch and 1.0 inch. Preferably, each of the plurality of perforations 1 10 has a lateral dimension D between 0.1 inch and 0.5 inch. For example the plurality of perforations 1 10 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 1 10 in a section of the perforated flame holder 102 divided by a total volume of the perforated flame holder 102 including body 108 and perforations 1 10. The perforated flame holder 102 should have a void fraction between 0.10 and 0.90. In an embodiment, the perforated flame holder 102 can have a void fraction between 0.30 and 0.80. In another embodiment, 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. For example, the perforated flame holder 102 can be formed to include mullite or cordierite. Additionally or alternatively, the perforated flame holder body 108 can include a metal superalloy such as Inconel or Hastelloy. The perforated flame holder body 108 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 inventors have found that the perforated flame holder 102 can be formed from VERSAGRID ® ceramic honeycomb, available from Applied

Ceramics, Inc. of Doraville, South Carolina.

The perforations 1 10 can be parallel to one another and normal to the input and output faces 1 12, 1 14. In another embodiment, the perforations 1 10 can be parallel to one another and formed at an angle relative to the input and output faces 1 12, 1 14. In another embodiment, the perforations 1 10 can be non- parallel to one another. In another embodiment, the perforations 1 10 can be non-parallel to one another and non-intersecting. In another embodiment, the perforations 1 10 can be intersecting. The body 208 can be one piece or can be formed from a plurality of sections. Embodiments described herein relate to a perforated flame holder 102 that is formed from a plurality of sections, referred to as tiles.

In another embodiment, which is not necessarily preferred, the perforated flame holder 102 may be formed from reticulated ceramic material. The term "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.

In another embodiment, which is not necessarily preferred, the perforated flame holder 102 may be formed from a ceramic material that has been punched, bored or cast to create channels.

In another embodiment, the perforated flame holder 102 can include a plurality of tubes or pipes bundled together. The plurality of perforations 1 10 can include hollow cylinders and can optionally also include interstitial spaces between the bundled tubes. In an embodiment, the plurality of tubes can include ceramic tubes. Refractory cement can be included between the tubes and configured to adhere the tubes together. In another embodiment, 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 108 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. In another embodiment, the perforated flame holder body 108 can include discontinuous packing bodies such that the perforations 1 10 are formed in the interstitial spaces between the discontinuous packing bodies. In one example, the discontinuous packing bodies include structured packing shapes. In another example, the discontinuous packing bodies include random packing shapes. For example, 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.

The inventors contemplate various explanations for why burner systems including the perforated flame holder 102 provide such clean combustion.

According to an embodiment, the perforated flame holder 102 may act as a heat source to maintain a combustion reaction even under conditions where a combustion reaction 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. Thus, according to an embodiment, at the point where the fuel stream 106 contacts the input face 1 12 of the perforated flame holder 102, an average fuel-to-oxidant ratio of the fuel stream 106 is below a (conventional) lower combustion limit of the fuel component of the fuel stream 106— lower combustion limit defines the lowest concentration of fuel at which a fuel and oxidant mixture 106 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 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. In one embodiment, "slightly lean" may refer to 3% O2, i.e. an equivalence ration of ~0.87. Use of even leaner mixtures is possible but may result in elevated levels of O2. Moreover, the inventors believe perforation walls 208 may act as a heat sink for the combustion fluid. This effect may alternatively or additionally reduce combustion temperatures and lower NOx.

According to another interpretation, production of NOx can be reduced if the combustion reaction 202 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. 3 is a flow chart showing a method 300, according to an embodiment, for operating a burner system that includes a perforated flame holder similar to the flame holder of FIGS. 1 and 2. To operate a burner system including a perforated flame holder, the perforated flame holder is first heated to a

temperature sufficient to maintain combustion of the fuel and oxidant mixture.

According to a simplified description, the method 300 begins with step 302, wherein the perforated flame holder is preheated to a start-up temperature, Ts. After the perforated flame holder is raised to the start-up temperature, the method proceeds to step 304, wherein the fuel and oxidant are provided to the perforated flame holder and combustion is held by the perforated flame holder.

According to a more detailed description, step 302 begins with step 306, wherein start-up energy is provided at the perforated flame holder.

Simultaneously or following providing start-up energy, a decision step 308 determines whether the temperature T of the perforated flame holder is at or above the start-up temperature, T_s. As long as the temperature of the perforated flame holder is below its start-up temperature, the method loops between steps 306 and 308 within the preheat step 302. In step 308, if the temperature T of at least a predetermined portion of the perforated flame holder is greater than or equal to the start-up temperature, the method 300 proceeds to overall step 304, wherein fuel and oxidant is supplied to and combustion is held by the perforated flame holder.

Step 304 may be broken down into several discrete steps, at least some of which may occur simultaneously.

Proceeding from step 308, a fuel and oxidant mixture is provided to the perforated flame holder, as shown in step 310. 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. In this approach, 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 perforated 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 perforated flame holder at a fuel dilution selected for a stable combustion reaction that can be held within the perforations of the perforated flame holder.

Proceeding to step 312, the combustion reaction is held by the perforated flame holder.

In step 314, heat may be output from the perforated flame holder. The heat output from the perforated flame holder may be used to power an industrial process, heat a working fluid, generate electricity, or provide motive power, for example.

In optional step 316, the presence of combustion may be sensed. Various sensing approaches have been used and are contemplated by the inventors. Generally, combustion held by the perforated 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. In an additional or alternative variant of step 316, 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 perforated flame holder. Proceeding to decision step 318, if combustion is sensed not to be stable, the method 300 may exit to step 324, wherein an error procedure is executed. For example, the error procedure may include turning off fuel flow, re-executing the preheating step 302, outputting an alarm signal, igniting a stand-by

combustion system, or other steps. If, in step 318, combustion in the perforated flame holder is determined to be stable, the method 300 proceeds to decision step 320, wherein it is determined if combustion parameters should be changed. If no combustion parameters are to be changed, the method loops (within step 304) back to step 310, and the combustion process continues. If a change in combustion parameters is indicated, the method 300 proceeds to step 322, wherein the combustion parameter change is executed. After changing the combustion parameter(s), the method loops (within step 304) back to step 310, 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 322. 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 perforated flame holder over one or more iterations of the loop within step 304.

Referring again to FIG. 1 , the burner system 100 includes a heater 128 operatively coupled to the perforated flame holder 102. As described in conjunction with FIGS. 2 and 3, the perforated flame holder 102 operates by outputting heat to the incoming fuel and oxidant mixture 106. After combustion is established, this heat is provided by the combustion reaction 202; but before combustion is established, the heat is provided by the heater 128.

Various heating apparatuses have been used and are contemplated by the inventors. In some embodiments, the heater 128 can include a flame holder configured to support a flame disposed to heat the perforated flame holder 102. The fuel and oxidant source 103 can include a fuel nozzle 1 18 configured to emit a fuel stream and an oxidant source 120 configured to output oxidant {e.g., combustion air) adjacent to the fuel stream. The fuel nozzle 1 18 and oxidant source 120 can be configured to output the fuel stream to be progressively diluted by the oxidant {e.g., combustion air). The perforated flame holder 102 can be disposed to receive a diluted fuel and oxidant mixture 106 that supports a combustion reaction 202 that is stabilized by the perforated flame holder 102 when the perforated 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 perforated flame holder 102.

The burner system 100 can further include a controller 130 operatively coupled to the heater 128 and to a data interface 132. For example, the controller 130 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 perforated flame holder 102 needs to be pre-heated and to not hold the start-up flame when the perforated flame holder 102 is at an operating temperature (e.g., when T > T_s).

Various approaches for actuating a start-up flame are contemplated. In one embodiment, the start-up flame holder includes a mechanically-actuated bluff body configured to be actuated to intercept the fuel and oxidant mixture 106 to cause heat-recycling and/or stabilizing vortices and thereby hold a start-up flame; or to be actuated to not intercept the fuel and oxidant mixture 106 to cause the fuel and oxidant mixture 106 to proceed to the perforated flame holder 102. In another embodiment, a fuel control valve, blower, and/or damper may be used to select a fuel and oxidant mixture flow rate that is sufficiently low for a start-up flame to be jet-stabilized; and upon reaching a perforated flame holder 102 operating temperature, the flow rate may be increased to "blow out" the start-up flame. In another embodiment, the heater 128 may include an electrical power supply operatively coupled to the controller 130 and configured to apply an electrical charge or voltage to the fuel and oxidant mixture 106. 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 fuel and oxidant mixture 106. 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.

In another embodiment, the heater 128 may include an electrical resistance heater configured to output heat to the perforated flame holder 102 and/or to the fuel and oxidant mixture 106. The electrical resistance heater can be configured to heat up the perforated flame holder 102 to an operating temperature. The heater 128 can further include a power supply and a switch operable, under control of the controller 130, to selectively couple the power supply to the electrical resistance heater.

An electrical resistance heater 128 can be formed in various ways. For example, the electrical resistance heater 128 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 1 10 defined formed by the perforated flame holder body 108. Alternatively, the heater 128 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.

Other forms of start-up apparatuses are contemplated. For example, the heater 128 can include an electrical discharge igniter or hot surface igniter configured to output a pulsed ignition to the oxidant and fuel. Additionally, or alternatively, a start-up apparatus can include a pilot flame apparatus disposed to ignite the fuel and oxidant mixture 106 that would otherwise enter the perforated flame holder 102. The electrical discharge igniter, hot surface igniter, and/or pilot flame apparatus can be operatively coupled to the controller 130, which can cause the electrical discharge igniter or pilot flame apparatus to maintain combustion of the fuel and oxidant mixture 106 in or upstream from the perforated flame holder 102 before the perforated flame holder 102 is heated sufficiently to maintain combustion. The burner system 100 can further include a sensor 134 operatively coupled to the control circuit 130. The sensor 134 can include a heat sensor configured to detect infrared radiation or a temperature of the perforated flame holder 102. The control circuit 130 can be configured to control the heating apparatus 128 responsive to input from the sensor 134. Optionally, a fuel control valve 136 can be operatively coupled to the controller 130 and configured to control a flow of fuel to the fuel and oxidant source 102. Additionally, or alternatively, an oxidant blower or damper 138 can be operatively coupled to the controller 130 and configured to control flow of the oxidant (or combustion air).

The sensor 134 can further include a combustion sensor operatively coupled to the control circuit 130, the combustion sensor being configured to detect a temperature, video image, and/or spectral characteristic of a combustion reaction 202 held by the perforated flame holder 102. The fuel control valve 136 can be configured to control a flow of fuel from a fuel source 1 18 to the fuel and oxidant source 102. The controller 130 can be configured to control the fuel control valve 136 responsive to input from the combustion sensor 134. The controller 130 can be configured to control the fuel control valve 136 and/or oxidant blower or damper 138 to control a preheat flame type of heater 128 to heat the perforated flame holder 102 to an operating temperature. The controller 130 can similarly control the fuel control valve 136 and/or the oxidant blower or damper 138 to change the fuel and oxidant mixture 106 flow responsive to a heat demand change received as data via the data interface 132.

FIG. 4 is a side-sectional diagram of a portion of a perforated flame holder 102, according to an embodiment 400. The perforated flame holder 102 includes a plurality of burner tiles 402 coupled together to form the perforated flame holder 102.

Each of the burner tiles 402 includes at least one receiving feature 404 extending into the burner tile laterally from a lateral surface of the burner tile. In some embodiments, the receiving feature 404 may extend entirely through a burner tile 402. In other embodiments, the receiving feature 404 may extend into but not through the burner tile 402. In the embodiment of FIG. 4, each tile 402 has a first receiving feature 404x extending parallel to a first lateral axis, and a second receiving feature 404y extending parallel to a second lateral axis, lying substantially perpendicular to the first axis, and longitudinally slightly offset therefrom. Thus, the first and second receiving features 404x, 404y cross in the approximate center of the respective tile 402 without intersecting. The plurality of burner tiles 402 is arranged in a closely spaced array, with the first receiving features 404x of each of the tiles 402 of the respective rows of the array in alignment and the second receiving features 404y of each of the tiles 402 of the respective columns in alignment.

Depending, in part, upon the material and manufacturing method used to produce the burner tiles 402, the receiving features 404 can be formed in a number of different ways. Examples of processes for forming the receiving features 404 include formation by movable or loose cores (in embodiments in which a casting process is used to make the burner tiles 402), drilling,

conventional machining, electrical discharge machining, waterjet machining, etc. The receiving features 404 can be formed prior to firing or sintering, i.e., in embodiments in which the burner tiles 402 are made from ceramic materials, or can be formed in otherwise complete burner tiles 402.

The perforated flame holder 102 includes a plurality of support members 406. A support member 406x extends through the first receiving feature 404x of each of the burner tiles 402 of a respective row, while a transverse support member 406y extends through the second receiving feature 404y of each of the burner tiles 402 of a respective column of the array. In embodiments in which the rows of burner tiles 402 are different in length from the columns, the support members 406x differ from the transverse support members 406y at least with respect to their respective lengths. In other embodiments, they may be substantially identical.

In the embodiment of FIG. 4, a transverse support member 406y is shown extending through the tiles 402 of each column of tiles. According to other embodiments, a smaller number of transverse support members 406y are employed. For example, according to an embodiment, the transverse support member 406y extends through the burner tiles 402 of the first and last columns of the perforated flame holder 102, but not through the intervening columns.

The support members 406 are preferably made of an alloy that is capable of tolerating sustained high temperatures, examples of which include, Inconel, Monel, Hastelloy, Stellite, etc. According to an embodiment, the support members 406 serve to reinforce a bond, formed by a bonding agent such as a refractory adhesive or cement, between the burner tiles 402, thereby reducing the likelihood of a failure of the bond. According to another embodiment, the bonding agent is omitted, and the tiles 402 are held in position solely by the support members 406. Omitting the bond between the burner tiles 402 can reduce the likelihood that damage to a single tile 402 will render the entire perforated flame holder 102 irreparable. Instead, the support members 406 that support the damaged tile 402 can be withdrawn far enough to release that tile, a new burner tile 402 positioned in its place, and the support members 406 reinserted.

In some embodiments, one or more of the receiving features 404 may extend through multiple perforations 1 10 in the body 108 of a burner tile 402. As a result, the receiving feature 404 may be discontinuous, as it passes through one perforation 1 10 after another. Nevertheless, for the purposes of the description and claims, where a plurality of individual openings extending between perforations 1 10 of a single burner tile 402 are in alignment with each other so as to define one, continuous, straight passage through the tile 402, the openings are considered to be comprised by a single receiving feature 404.

Additionally, although, in many embodiments, support members 406 may extend through, and partially obstruct some of the perforations 1 10 of the burner tile 402, most of the perforations 1 10 remain completely unobstructed. Thus, for the purposes of the specification and claims, the perforations 1 10, in such

embodiments, are considered to be substantially unobstructed.

In one embodiment, each support member 406 extends only partially into a single burner tile 402. Each receiving feature 404 may extend only a few cells or perforations deep into the burner tile 402. The support members 406 can be ceramic dowels that extend partially into the burner tiles 402.

In one embodiment, the perforated flame holder 102 can include a first group of burner tiles 402 and a second group of burner tiles 402. The first group of burner tiles 402 can include the three burner tiles on the right side of the perforated flame holder 102. The second group of burner tiles 402 can include the three burner tiles on the left side of the perforated flame holder. Each of the support members 406y can extend through both a burner tile 402 of the first group and an aligned burner tile 402 of the second group via the receiving features 404 of the burner tiles 402. Alternatively, each member 406y can pass only partially through a single burner tile 402 such that there can be a single support member 406y for each respective burner tile 402 of both the first and second groups.

In one embodiment, the support members 406 hold the perforated flame holder 102 in alignment above the fuel and oxidant source 103 of FIG. 1 , as part of a combustion system. Each burner tile 402 includes an input face 1 12 aligned to receive the fuel and oxidant 106, an output face 1 14 distal from the fuel and oxidant source 103, and a plurality of perforations 1 10 extending between the input face 1 12 and the output face 1 14. The fuel and oxidant source 103 outputs fuel and oxidant 106. The perforated flame holder 102 receives the fuel and oxidant 106 into the perforations 1 10 of the burner tiles 402. The perforated flame holder 102 supports a combustion reaction 202 of the fuel and oxidant 106 within the perforations 1 10 of the burner tiles 402.

In one embodiment, with reference to FIG. 1 and FIG. 4, a combustion system includes a fuel and oxidant source 103 configured to output a fuel and an oxidant 106. The combustion system includes a perforated flame holder 102 including a group of burner tiles 402 arranged side by side. Each burner tile 402 includes an input face 1 12 aligned to receive the fuel and the oxidant 106, an output face 1 14, and a plurality of perforations 1 10 extending between the input face 1 12 and the output face 1 14. The perforated flame holder is configured to support a combustion reaction of the fuel and the oxidant within the perforations 1 10. A first burner tile 402 of the plurality of burner tiles includes a receiving feature 404. The combustion system can include a first support member 406 extending into the first burner tile 402 via the receiving feature 404 and holding the perforated flame holder 102 in alignment to receive the fuel and oxidant 106 into the perforations 1 10. In one alternative embodiment, the first support member 406 terminates within the first burner tile 402. In one embodiment, the first support member is a ceramic dowel. In one alternative embodiment, the first support member extends entirely through the first burner tile along an axis substantially parallel to the input face of the first burner tile. In one alternative embodiment, a second burner tile of the plurality of burner tiles includes a receiving feature. In one alternative embodiment, the first support member extends through the first burner tile and into the second burner tile via the receiving feature of the second burner tile. In one alternative embodiment, the combustion system includes a second support member extending into the second burner tile via the receiving feature of the second burner tile. In one alternative embodiment, the plurality of burner tiles includes a first group of burner tiles including the first burner tile, each burner tile of the first group including a respective receiving feature. In one alternative embodiment, the first support member extends into each burner tile of the first group via the respective receiving features. In one alternative embodiment, the plurality of burner tiles includes a second group of burner tiles each including a respective receiving feature. In one alternative embodiment, the combustion system includes a second support member extending into each burner tile of the second group via the respective receiving features. In one alternative embodiment, the first group of burner tiles is a first row of burner tiles, and wherein the second group of burner tiles is a second row of burner tiles. In one alternative embodiment, the second support member passes through each burner tile of the second group along an axis transverse to a flow of the fuel from the fuel and oxidant source toward the perforated flame holder. In one alternative embodiment, the first support member passes through each burner tile of the first group along an axis transverse to a flow of the fuel from the fuel and oxidant source toward the perforated flame holder.

In one embodiment, with reference to FIG. 1 and FIG. 4, a combustion system includes a fuel and oxidant source 103 configured to output a fuel and an oxidant 106. The combustion system includes a perforated flame holder 102 including a group of burner tiles 402 arranged side by side. Each burner tile 402 includes an input face 1 12 aligned to receive the fuel and the oxidant 106, an output face 1 14, a plurality of perforations 1 10 extending between the input face 1 12 and the output face 1 14, and a receiving feature. The perforated flame holder is configured to support a combustion reaction of the fuel and oxidant 106 within the perforations 1 10. The combustion system includes a plurality of support members 406 each extending into a respective burner tile 402 of the first group via the receiving feature 404 and supporting the perforated flame holder 102 in alignment to receive the fuel and oxidant 106. In one alternative embodiment, each support member 406 extends through the respective burner tile 402 of the first group into a respective burner tile 402 of the second group. In one alternative embodiment, the support members 406 each terminate within the respective burner tile 402. In one alternative embodiment, the support members 406 are ceramic dowels. In one embodiment, each support member 406 extends entirely through the respective burner tile 402 along an axis substantially parallel to the input face 1 12 of the burner tile.

In one alternative embodiment, with reference to FIG. 1 and FIG. 4, a method includes outputting a fuel an oxidant 106 into the furnace volume 104 and supporting a perforated flame holder 102 including a plurality of burner tiles 402 arranged side by side in alignment to receive the fuel and oxidant 106 by passing a support member 406 into at least one of the burner tiles 402 via a receiving feature 404 of the at least one burner tile 402. Each burner tile 402 includes an input face 1 12, an output face 1 14, and a plurality of perforations 1 10 extending between the input face 1 12 and the output face 1 14. The method includes receiving the fuel and oxidant 106 into the perforations 1 10 of each burner tile 402 and supporting a combustion reaction of the fuel and oxidant 106 within the perforations 1 10 of each burner tile 402. In one alternative

embodiment, supporting the perforated flame holder 102 includes passing the support member 406 into multiple burner tiles 402. In one alternative

embodiment, supporting the perforated flame holder 102 includes passing multiple support members 406 each into a respective burner tile 402 of the plurality of burner tiles.

In one embodiment, the support members 404 are elongated support members.

FIG. 5 is a perspective view of a perforated flame holder 500 according to another embodiment, in which each burner tile 402 has multiple receiving features 404 extending parallel to a first lateral axis, with support members 406 maintaining a common orientation of all of the tiles 402 of a given row. The embodiment of FIG. 5 provide advantages during installation of the perforated flame holder 500, particularly in large furnaces, inasmuch as the perforated flame holder 500 can be installed one row of tiles 402 at a time. In embodiments that employ a single support member 406 per row of tiles, there is the possibility that individual tiles can rotate on the support member during handling, which may increase the difficulty of the installation. In contrast, with two or more support members 406 per row, each tile 402 is held in alignment with the entire row, simplifying the task, and reducing the likelihood of damage to the often-fragile tiles 402.

FIG. 6 is a perspective view of a perforated flame holder 600, according to an embodiment, which includes support members 602 that are non-circular in cross section. In the embodiment shown, the support members 602 are flat, with rounded edges. Receiving features 604 having a shape that substantially corresponds to the shape of the support members 602 extend into (and optionally through) the burner tiles 402 transverse to the burner tile 402 lateral wall. The longer sectional dimension of the flat support members 602— and the receiving features 604— may be aligned with a longitudinal axis relative to the burner tiles 402, so as to present a narrow edge to the flow of fuel and

combustion gases through the burner tiles 402. Support members 602 may have a variety of sectional shapes, including oval, flattened teardrop, polygonal, etc.

FIG. 7 is a perspective view of a portion of a combustion system 700, according to an embodiment. The combustion system 700 includes a perforated flame holder mounting structure 702 configured to couple to and support a perforated flame holder 102 made up of a plurality of burner tiles 402, within a combustion volume. In the embodiment shown, the perforated flame holder mounting structure 702 is configured to couple to a perforated flame holder 102, as described above with reference to FIG. 4. However, according to various embodiments, the perforated flame holder mounting structure 702 can be configured to couple to a wide variety of perforated flame holders, including those described with reference to various embodiments disclosed herein.

The perforated flame holder mounting structure 702 includes coupling features 704 positioned and shaped to receive respective ends of the support members 406 of the perforated flame holder 102. In the embodiment shown, the coupling features 704 are notches formed in the perforated flame holder mounting structure 702. The ends of the support members 406 rest on the bottoms of the respective coupling features 704, which thereby serve to support the perforated flame holder 102 in a selected position and orientation within the combustion volume.

As noted above, the receiving features 404x and 404y are offset longitudinally, so that the corresponding support members 406x and 406y can cross within the burner tiles 402 without intersecting. Accordingly, coupling features 704x, positioned to receive the ends of the support members 406x, have a first depth, while coupling features 704y, positioned to receive the ends of the transverse support members 406y, have a second depth that is greater than the first depth. Thus, the perforated flame holder 102 is fully supported along each side.

According to an embodiment, the perforated flame holder mounting structure 702 is sized to closely fit around the perforated flame holder 102. This holds the burner tiles 402 in close contact, even if the tiles are not bonded, or otherwise held together.

The coupling features are shown in FIG. 7 as notches formed in the perforated flame holder mounting structure 702. According to other

embodiments, the coupling features 704 have other shapes and configurations, including, for example, detents, hooks, apertures, etc.

FIGS. 8A-8D are partial side-sectional diagrams of perforated flame holders showing details of portions of burner tiles with examples of support members and fasteners, according to respective embodiments.

FIG. 8A shows a detail of a perforated flame holder 800. In this

embodiment, a support member 802 has a threaded portion 804 that extends from a lateral wall 805 of a burner tile 402 that is at one end of a row or column of burner tiles 402, the lateral wall 805 forming a portion of a peripheral surface of the perforated flame holder 800. A threaded nut 806, in the shape of an escutcheon, or boss, is screwed onto the threaded portion 804 of the support member 802. An inner face 808 of the threaded nut 806 bears against a lateral surface 810 of the burner tile 402 (the lateral surface 810 forming a portion of the peripheral surface 1 16 of the perforated flame holder 800). With a threaded nut 806 coupled to each end of the support member 802, the support member 802 can be placed under tension, thereby pulling the burner tiles 402 through which it passes into close contact, and placing them under a controlled degree of compression stress.

Tensioned support members 802 may reduce the likelihood of damage to burner tiles 402 during service and handling. For example, when a perforated flame holder 800— or row of burner tiles 402— is supported at opposite edges in a horizontal orientation, a bending stress is produced along its length. During handling of the perforated flame holder 800, the bending stress can fluctuate, and can momentarily spike, even with careful handling. During such spikes, the material of the burner tiles 402 can fracture, or a refractory cement bond can fail. In either case, damage to the perforated flame holder 800 or row 402 may render it unusable. However, even in embodiments in which the support member 802 itself is not sufficiently stiff to substantially limit flexion of the perforated flame holder 800 under tension, it can significantly increase the stiffness and structural strength of the perforated flame holder 800, reducing the likelihood of damage during handling.

FIG. 8B shows a detail of a perforated flame holder 820. In this

embodiment, a support member 822 extends through a retaining washer 824 having an inner face 808 that bears against a lateral surface 810 of the burner tile 402. A split pin 826 extends through a receiving feature 828 in the support member 822, capturing the retaining washer 824, and limiting inward lateral movement of the support member 822.

The retaining washer 824 is shown as having a shape that is similar to the shape of the threaded nut 806 of FIG. 8A. The actual shape of the retaining washer 824, the threaded nut 806, or any other fastener coupled to a support member 822 is a design choice, and is limited only by the conditions and requirements of a specific application. For example, the retaining washer 824 can be a standard fender washer, etc. Additionally, while a split pin 826 is shown in FIG. 8B as an example, other types of retaining elements can be used, including, for example, spring pins, R-clips, etc.

FIG. 8C shows a detail of a perforated flame holder 830. In this

embodiment, a burner tile 832 includes a lateral wall 805 with an increased thickness, as compared to others of the perforation walls 208. A countersunk cavity 836 is formed in the lateral wall 805 that is concentric with the receiving feature 404. A threaded countersink nut 838 is screwed onto the threaded portion 804 of the support member 802. An inner face 840 of the countersink nut 838 bears against a face 842 of the cavity 836, with the nut 838 countersunk into the lateral wall 805 of the burner tile 832, and with an outer face 844 of the countersink nut 838 recessed below a lateral surface 810 of the burner tile 832.

The embodiment shown in FIG. 8C is of particular use in applications where the lateral surface 810 of the burner tile 832 is to be in close contact with a furnace wall 848 or other surface during operation, inasmuch as the end of the support member 802 and the countersink nut 838 are recessed below the lateral surface 810.

It should be noted that typically, the ceramic or composite materials used for burner tiles has a much lower coefficient of thermal expansion than the refractory alloys that might be used for support members. For example, ceramics made from alumina or Mullite generally have coefficients of thermal expansion of around 3x10^"6/°F, and cordierite has a coefficient of less than 0.1x10^"6/°F. In contrast, alloys such as Monel, Hastelloy, and Inconel each have a coefficient of thermal expansion of around 7x10^"6/°F, or more. Perforated flame holders typically operate at temperatures exceeding 1500°F, and often exceeding 2000°F. If the support members (406, 802, 822, etc.) fit closely within the receiving features 404 at room temperature, there is a danger that as the perforated flame holder heats to its normal operating temperature, the greater expansion of the support members 822 will crack or break the material of the burner tiles. Accordingly, it is preferable that the receiving features 404 be dimensioned slightly larger than the dimensions of the support members 822, so as to accommodate the expansion of the support members 822.

Similarly, an allowance for lengthwise expansion of support members 822 is preferable, where clearance might otherwise be a problem. For example, referring to FIG. 8C, it is preferable that an expansion gap GE be allowed between the outer face 844 of the countersink nut 838 and the face of the furnace wall 848. The depth of the expansion gap GE is selected to be sufficient to accommodate lengthwise thermal expansion of the support member 802, to prevent contact of the threaded countersink nut 838 with the furnace wall 848.

FIG. 8D shows a detail of a perforated flame holder 850, according to an embodiment. The perforated flame holder 850 includes a support member 852 in the form of a wire, extending through a receiving feature 404 in a burner tile 402. A retaining clip 854 holds the support member 852 at each end. The retaining clip 854 can be, for example, in the form of a push nut, or similar device, configured to hold the support member 852 under tension. FIG. 8D also shows an opening 856 formed in a lateral wall 805 of the burner tile 402. The opening 856 is sized to permit the retaining clip 854 to bear against an inner perforation wall 208 of the burner tile 402, permitting the lateral surface 810 of the burner tile 402 to be positioned in close contact with a furnace wall 848, etc.

In the embodiments disclosed above, perforated flame holders are shown with the burner tiles in substantially planar configurations, with their respective lateral faces lying in common planes. However, in some furnace configurations, it may be desirable to have a perforated flame holder whose face is not planar, but that instead has some other selected shape. According to various

embodiments, the burner tiles of a perforated flame holder can be offset, longitudinally, with respect to other burner tiles, in order to modify the shape of the perforated flame holder.

FIG. 9 is a side elevation view of a row 900 of burner tiles 402, according to an embodiment, in which the burner tiles 402 are arranged in an arcuate configuration. The row 900 can be assembled with similarly configured rows to create a perforated flame holder having one shape, or with differently configured rows to create perforated flame holders having other shapes, as will be described later in more detail. According to various embodiments, the burner tiles 402 can be arranged to follow a catenary curve, a ballistic curve, an arc segment of a circle, etc. According to other embodiments, the burner tiles 402 can be arranged in other configurations, such as, for example, zig-zag, etc.

In the embodiment shown, the longitudinal separation of the burner tiles 402 is such that a single support member 802 cannot extend through all of the burner tiles 402 of the row 900. Accordingly, the row 900 includes first and second support members 802xi, 802x₂, which are offset longitudinally, with respect to each other. The first support member 802xi extends through all but the outermost tiles 402, while the second support member 802x₂ extends through two tiles at each end of the row 900, coupling the outermost tiles to the remaining tiles of the row 900.

Transverse receiving features 404y are configured to receive respective support members when the row 900 is combined with additional rows of burner tiles 402 to form a perforated flame holder, to hold the rows in close contact. Perforated flame holder support brackets 902 are configured to support the row 900, together with the other rows of a perforated flame holder, in a combustion volume, and to prevent lateral movement of the rows or of individual burner tiles 402 along the X axis.

In some embodiments in which the burner tiles 402 of the row 900 are bonded to each other, the first support member 802_xi may be omitted. The second support member 802χ₂ reinforces the row 900 and retains the arcuate shape of the row 900 during handling, while a bonding agent between the burner tiles 402 holds the inner tiles in place. Once the row 900 is installed in a combustion volume, the perforated flame holder support brackets 902 provide the necessary lateral support.

The row 900 is shown with support members 802 and threaded nuts 806. However, this is by way of example, only. According to various embodiments, other support members, as well as other fasteners can be employed, including, for example, the support members and fasteners previously disclosed herein.

FIGS. 10 and 11 are perspective views of examples of perforated flame holders that can include the row 900 of burner tiles 402 described above with reference to FIG. 9, according to respective embodiments.

FIG. 10 shows a perforated flame holder 1000 that includes a plurality of rows 900 of burner tiles 402, positioned side-by-side, held in close contact with each other by support members 802y extending through transverse receiving features 404y (see FIG. 9) of each row, giving the perforated flame holder 1000 a vault shape. The perforated flame holder support brackets 902 support the perforated flame holder 1000 along two opposite edges, providing lateral support and holding the perforated flame holder 1000 in a selected position within a combustion volume.

FIG. 11 shows a perforated flame holder 1 100 that includes a row 900 of burner tiles 402 in the center of the perforated flame holder 1 100, with rows 1 102 of burner tiles 402 positioned on either side of the row 900, rows 1 104 positioned outside the rows 1 102, and so on to the outermost rows 1 1 10 of burner tiles 402. The configuration of burner tiles 402 of the row 900 and of each pair of rows 1 102, 1 104, 1 1 10, etc., is different from the configuration of tiles of the other rows of the perforated flame holder 1 100. When assembled together to form the perforated flame holder 1 100, as shown in FIG. 11 , they give the perforated flame holder 1 100 a substantially symmetrical dome shape. Each row 900, 1 102, 1 104, 1 1 10 includes at least one support member 802x, while support members 802y extend through burner tiles 402 of selected columns, holding the rows in close contact. A perforated flame holder support bracket 1 1 12 is shown, configured to support the perforated flame holder 1 100 along four edges within a combustion volume.

According to various additional embodiments, perforated flame holders having other symmetrical and asymmetrical shapes can be made by selection of the number of rows of burner tiles, and the number, size, shape, and relative longitudinal displacement of the burner tiles of each row of the respective perforated flame holders.

FIG. 12 is a plan view of a perforated flame holder 1200, according to another embodiment, provided here to show an example of a perforated flame holder with elements having shapes other than square or rectangular. The perforated flame holder 1200 includes a plurality of rows 1202 of burner tiles 1204. The burner tiles 1204 of each row 1202 are hexagonal in plan view, and the burner tiles 1204 of adjacent rows 1202 nest together to form a hexagonal grid.

Each of a first plurality of support members 406x extends through each of the burner tiles 1204 of a respective one of the plurality of rows 1202. Each of a second plurality of support members 406y extends transversely through each of the burner tiles 1204 of a respective column 1206 of tiles of the perforated flame holder 1200. Because the tiles 1204 of the perforated flame holder 1200 are arranged in a hexagonal grid, the columns of the grid lie at an angle of 60 or 120 degrees, relative to the rows of the grid.

In the example shown, the burner tiles 1204 are configured as perforated flame holders 102, as described in detail above with reference to FIGS. 1 and 2, and thus include respective pluralities of perforations 1208, which, in this embodiment, are hexagonal in shape.

According to respective embodiments, various methods are provided for assembling, handling, and installing perforated flame holders like those disclosed herein. For example, according to an embodiment, a technician assembles pluralities of burner tiles and support members to form rows, then assembles the rows to form a perforated flame holder or segments thereof. According to another embodiment, a technician obtains pre-assembled rows of burner tiles, or pre-assembled segments, each having a plurality of rows, then assembles these to form the perforated flame holder. According to a further embodiment, the technician obtains a preassembled perforated flame holder. According to an embodiment, the pre-assembled rows, segments, or perforated flame holder include pre-positioned support members. According to another embodiment, the technician positions some or all of the support members after obtaining the pre- assembled rows, segments, or perforated flame holder.

According to an embodiment, a fully assembled perforated flame holder is installed as a unit into the combustion volume of a furnace. Support members extending through at least each row of burner tiles of the perforated flame holder stiffen the perforated flame holder and reduce the likelihood of damage during installation. According to an embodiment, at least some of the additional stiffness is a result of tension applied to the support members.

The perforated flame holder is similarly protected during service of the furnace. For example, where it becomes necessary to remove the perforated flame holder from the furnace, the support members again provide additional strength and stiffness, enabling removal of the perforated flame holder from the furnace and, later, reinstallation, while reducing the likelihood of damage during handling.

According to another embodiment, rows of burner tiles are coupled together outside the furnace to form segments of the perforated flame holder, which are then separately installed in the furnace to form the perforated flame holder. According to a further embodiment, each of the rows of burner tiles is installed separately into the furnace to form the perforated flame holder.

Embodiments in which the perforated flame holder is installed in pieces, either as individual rows, or as larger segments, are particularly useful where the perforated flame holder is relatively large. Very large perforated flame holders can be difficult to manipulate, particularly within the confines of a combustion volume, which increases the danger of damage to the plate. By moving segments or rows of a perforated flame holder at a time, instead of the entire plate at once, installation or removal is simplified. The smaller pieces are less unwieldy, and the risk of damage is reduced.

Because damage to a perforated flame holder is often irreparable, or at least costly, the use of support members in accordance with the principles of the invention can reduce maintenance costs. According to an embodiment in which the tiles of the individual rows are bonded together but the rows are not bonded, damage to one tile can be repaired by replacement of the corresponding row, rather than of the entire perforated flame holder.

For example, in an embodiment in which the rows are held together by two or more transverse support members— as described above, for example, with reference to FIGS. 4 and 10-12, the transverse support members are withdrawn from the perforated flame holder a distance sufficient to clear the row with the damaged tile. That row is then repaired or replaced, and the transverse support members reinserted, and, where appropriate, tensioned. Where there is sufficient space within the furnace, the repair can be made without removing the perforated flame holder from the furnace. Otherwise, the perforated flame holder is first removed from the furnace, then repaired, and then reinstalled.

FIG. 13A is a diagrammatic plan view of a perforated flame holder 1300, according to an embodiment, taken in a plane lying substantially parallel to, and between input and output faces of the perforated flame holder 1300. The perforated flame holder 1300 comprises an array of burner tiles 402 arranged in rows and columns. Support members 1302 extend between pairs of

corresponding receiving features 1304 in facing lateral sides of the burner tiles 402. In the embodiment of FIG. 13A, a support member 1302 is provided between each adjacent pair of burner tiles 402 of each row, and between adjacent pairs of burner tiles 402 of each column. According to another embodiment, multiple support members 1302 are provided between some or all of the adjacent pairs of burner tiles 402 of the array. According to an

embodiment, support members 1302 are provided between adjacent pairs of burner tiles 402 in each row, but not between tiles 402 in different rows, so that the rows can be moved and handled separately.

The support members 1302 are in the form of short pins that act primarily as shear members to hold the burner tiles 402 in their proper positions within the perforated flame holder 1300. The pins 1302 can be made from any of a number of different materials, including, for example, alumina, mullite, cordierite, ceramic binder, combinations of these and/or other suitable materials, etc. According to an embodiment, the pins 1302 are made of the same material used to make the burner tiles 402. The pins 1302 are preferably made of a material whose coefficient of thermal expansion is substantially equal to that of the material of the burner tiles 402— although other materials can be used, provided that the relative sizes of the receiving features 1304 and pins 1302 are selected to accommodate differences in thermal expansion rates. According to an

embodiment, the receiving features 1304 are round, with a diameter of about 1/2 inch and a depth exceeding one inch, and the pins 1302 are round, with a diameter of about ¾ inch and a length of about two inches.

Refractory cement can be used to fix the pins 1302 in place, in which case the perforated flame holder 1300 is substantially rigid, and strengthened by the pins 1302. Alternatively, the perforated flame holder 1300 can be assembled without adhesive or cement, which can result in some relative movement of the tiles 402, but also enables the removal and replacement of individual burner tiles 402, rather than requiring the replacement of the entire perforated flame holder 1300. According to an embodiment, a wire or strap is positioned around the perforated flame holder 1300, and tensioned to hold the burner tiles 402 in position during installation, and to prevent any of the burner tiles 402 from separating enough to permit a pin 1302 to slip entirely from the corresponding receiving feature 1304.

FIG. 13B is a detail of the perforated flame holder 1300, according to an embodiment, taken from a position indicated in FIG. 13A at 13B, and showing portions of two burner tiles 402a, 402b of the plurality of burner tiles 402 of the perforated flame holder 1300, with respective lateral walls 805a, 805b positioned in face-to-face contact. Respective receiving features 1304a, 1304b extend into the burner tiles 402a, 402b a distance that, in sum is slightly longer than the length of the pin 1302. The pin 1302 is captured within the receiving features 1304a, 1304b of the burner tiles 402a and 402b, and serves to prevent significant relative motion of the tiles 402, and to support the tiles 402 of the perforated flame holder 1300 during installation and servicing.

According to an embodiment, the burner tiles 402 include respective pluralities of perforations 1 10 defined by perforation walls 208. In the example shown, the perforations 1 10 are substantially square, with perforation walls 208x extending parallel to a first (longitudinal) axis, and perforation walls 208y extending parallel to a second axis, substantially perpendicular to the first axis. The receiving features 1304a, 1304b are slightly larger in diameter than the pin 1302. This may provide several potential benefits. For example, one possible advantage is that typical manufacturing processes can result in slight variations in dimensions of the burner tiles 402, and/or the exact positions of the receiving features 1304. In the case of a perforated flame holder 1300 that has a number of burner tiles 402, these slight variations can result in some minimal

misalignment of the receiving features 1304 of some of the tiles 402. The oversized receiving features 1304 can compensate for such misalignment in a manner that is generally more cost effective than the employment of more expensive processes that would be required to achieve higher tolerances.

Another potential advantage is that, during operation of a furnace, the temperature of a perforated flame holder 1300 in the furnace can vary

significantly at different locations of the plate 1300, particularly during startup and shutdown of the furnace. The loose fit of the pins 1302 in the receiving features 1304 can permit some limited relative movement of the burner tiles 402 caused by different degrees of thermal expansion, as some parts of the perforated flame holder 1300 heat or cool faster than others.

Finally, even though the pins 1302 may be made from the same material as the burner tiles 402, the pins are much stronger than the perforation walls 208 of the burner tiles 402 because the pins are far more massive than the walls. Thus, perforation walls 805 can be very easily broken by the pins 1302 during assembly of the perforated flame holder 1300 if there is any binding or tightness. The slightly oversized receiving features 1304 help reduce the likelihood of such damage.

During testing of prototype systems, the inventors found that the use of pins in receiving features was very effective in supporting the burner tiles of large perforated flame holders, and resulted in a reduction of damage to perforated flame holders during installation and service, and also reduced the cost and extent of repairs when such became necessary.

However, the inventors also noted that the burner tiles used in the tests often showed small cracks in the material of the burner tiles, extending upward in the lateral walls of the tiles from the receiving features to the upper surface of the tiles. The inventors believe that the cracks are caused by stresses imposed by the pins, as explained below with reference to FIGS. 14A and 14B.

FIG. 14A is a cross sectional diagram of a portion of a perforated flame holder 1300, according to an embodiment, as viewed along lines 14A-14A in FIG. 13B. FIG. 14B is a cross sectional diagram of the perforated flame holder 1300 of FIG. 14A, as viewed along lines 14B-14B in FIG. 14A, and shows, in particular, a lateral surface 810 of the burner tile 402b, and a section of a pin 1302 in the plane where it passes through the outer perforation wall 805b of the burner tile 402b, via the receiving feature 1304b.

FIGS. 14A and 14B show a pin 1302 positioned in receiving features 1304a and 1304b of burner tiles 402a and 402b. The burner tiles 402a and 402b are shown rotated away from each other such that their lateral surfaces 810a, 810b are in contact at their upper edges, while separated from each other at their lower edges. Although greatly exaggerated for clarity, this kind of relative orientation is not unusual between adjacent tiles in a perforated flame holder, during installation and during normal operation. The inventors believe that forces acting on the burner tiles 402a, 402b are concentrated to a point of stress S where the upper surface of the pin 1302 contacts the top of each receiving feature 1304a and 1304b at the lateral wall 805a, 805b of the respective burner tile 402a, 402b, inducing stress cracks in the lateral walls 805 of the burner tiles 402a, 402b.

FIG. 15 is a cross sectional diagram of a portion of a perforated flame holder 1500 in a view that corresponds to the view of FIG. 14A, according to another embodiment, in which the receiving features 1304 include an outer portion 1502 that is relieved at an angle that approximately corresponds to the angle at which the pin 1302 rests relative to the lateral surfaces 810. In the embodiment shown in FIG. 15, the relief is in the form of a slight chamfer, or taper 1504 of the receiving features 1304. The relief can be formed in a number of ways. For example, a cutting tool can be used whose profile includes the shape of the entire receiving feature 1304, so that during the manufacturing process, the entire receiving feature 1304 can be formed in a single operation. Alternatively, a straight-sided receiving feature 1304 can be formed first, followed by formation of the chamfer 1504 in a separate operation. Furthermore, it is not essential that the receiving features 1304 be radially symmetrical, such as the example of FIG. 15. According to another embodiment, an angled cutting tool is used to form the relief at the top of the receiving features 1304, while the lower portions remain straight.

The angled outer portion 1502 of the receiving features 1304 serves to distribute the stress across a broader surface area, compared to the embodiment described with reference to FIGS. 14A and 14B, reducing the likelihood that cracks will form in the perforation walls 208, and particularly in the outer perforation walls 805. In the example of FIG. 15, it can be seen that in each of the tiles 402, the stress load is shared by the lateral wall 805 and at least one of the inner walls 208y, so that the stress load is distributed across at least two points of stress S. Additionally, in the embodiment of FIG. 15, the receiving features 1304 are positioned such that one of the walls 208x that lies parallel to the X axis is positioned at the approximate center of the receiving features 1304 (see, for example, the transverse view of the embodiment of FIG. 14B), resulting in stress being distributed along a portion of its length.

FIG. 16A is a cross sectional diagram of a portion of a perforated flame holder 1600 in a view that corresponds to the view of FIG. 14A, according to an embodiment. FIG. 16B is a cross sectional diagram of the perforated flame holder 1600 as viewed along lines 16B-16B in FIG16A. In the embodiment of FIGS. 16A, 16B, a pin assembly 1602 is provided, which includes a pin 1302 surrounded by strain relief member 1604 made of a relatively flexible and resilient material. The strain relief member 1604 can be made, for example, as a tube segment of a refractory reticulated foam, a fibrous ceramic sleeve material that is woven or matted to form a hollow, flexible tube, a ceramic blanket that is wrapped, or partially wrapped around the pin 1302, etc. The strain relief member 1604 acts to distribute the stress load within the receiving features 1304, protecting the relatively fragile perforation walls 208 and limiting relative movement between adjacent pairs of burner tiles 402.

According to an embodiment, the outside dimensions of the strain relief member 1604 are selected to be equal to or larger than the dimensions of the receiving features 1304, so that the strain relief member 1604 engages the receiving features 1304 with a limited friction or interference fit.

FIG. 17 is a cross sectional diagram of a portion of a perforated flame holder 1700, according to an embodiment, in a view that corresponds to the views of FIGS. 14B and 16B. FIG. 17 shows a portion of a single burner tile 402b of the perforated flame holder 1700, including a lateral surface 810 of the burner tile 402b, and a section of a pin 1702 in the plane where it passes through the outer perforation wall 805b of the burner tile 402b, via the receiving feature 1304b. The pin 1702 includes a plurality of channels, or grooves 1704 that extend the length of the pin— i.e., parallel to the Y axis, as viewed in the drawings— and that are separated by ridges 1706. In the embodiment of FIG. 17, the ridges 1706 and grooves 1704 have a saw-tooth shape, in cross section, although other configurations can also be used. The ridges are thickest where they meet to form the grooves 1704, and taper outward, having a smallest thickness at their outermost edges.

At their outermost edges, the ridges 1706 preferably have a thickness that is much less than a thickness T_w of the perforation walls 208 that define the receiving feature 1304. According to an embodiment, the ridges 1706 have a smallest thickness that is less than about 10% the thickness T_w of the perforation walls 208. Because the ridges have a smallest thickness that is much less than the thickness T_w of the perforation walls 208, they are relatively quite fragile. Thus, when the burner tiles 402 of the perforated flame holder 1700 move with relation to each other, and stress is applied— as described above with respect to FIGS. 14A and 14B— the outermost portions of the ridges 1706 fracture and break away where stress is applied, at the points where they contact the perforation walls 208, 805 within the receiving features 1304. As a portion of one ridge 1706 breaks away, the remaining portion of that ridge 1706 contacts the respective perforation wall 208, 805 with a broadened surface area.

Simultaneously, a miniscule amount of movement occurs, bringing another one or more ridges 1706 into contact, which also break away, bringing further ridges 1706 into contact, etc. With each ridge 1706 that makes contact, the number of stress points S is increased, and the stress load is distributed across a broader total surface area, reducing the likelihood of formation of stress cracks in the burner tiles 402.

FIG. 18 is a partially cut away perspective view of a portion of a perforated flame holder 1800 according to another embodiment. The perforated flame holder 1800 includes a plurality of burner tiles 402, of which representative burner tiles 402a, 402b are shown in face-to-face contact. Burner tiles 402A and 402b each include a receiving feature, in the form of a channel 1802, extending through their respective lateral walls 805 and running parallel to input and output faces of the perforated flame holder 1800. A spline 1804 is captured in the closed space defined by the grooves 1802 of the burner tiles 402a, 402b. The support member 1804 acts as a shear member in the perforated flame holder 1800, holding the tiles 402a, 402b in relative position.

The spline 1804 can be flat and sufficiently broad as to occupy most of the combined depths of the grooves 1802a and 1802b. While shown as having lateral sides that are square, according to various embodiments, the lateral edges of the spline 1804 can have any shape that does not interfere with its operation, such as, e.g., rounded, chamfered, bull nosed, etc.

One potential advantage of a spline 1804 is that it can serve to distribute the stress load over a broad surface area, and reduce or prevent the occurrence of stress cracks in burner tiles 402.

According to an embodiment, the grooves 1802 extend the length of the burner tiles 402. According to another embodiment, the grooves 1802a, 1802b extend less than half the length of the respective burner tiles 402a, 402b.

According to an embodiment, the spline 1804 extends the length of an entire row of burner tiles 402 of the perforated flame holder 1800, and engages the grooves 1802 of each of the burner tiles 402 of two facing rows of burner tiles 402 of the perforated flame holder 1800. According to another embodiment, the spline 1804 is substantially equal in length to the grooves 1802. According to respective alternative embodiments, the length-to-height ratio of the spline 1804 is less than 2: 1 , less than 4: 1 , and less than 10: 1 .

The spline 1804 can be sized to extend the entire length of the grooves 1802, or to extend beyond the burner tiles 402a, 402b and engage the grooves of additional burner tiles 402. However, it is not essential that the spline 1804 occupy the entire length of the burner tiles 402. For example, according to an embodiment, the grooves 1802 extend the full length of the burner tiles 402, while the splines 1804 are less than half the length of the grooves 1802.

The grooves 1802 can be formed in any of a number of different ways. For example, a cutting tool such as an end mill, router, or flat bed tile saw can be used to form a groove 1802 of any length in a lateral face of a burner tile 402. Such a groove 1802 can be made to extend the entire length of the tile 402, or to be shorter than the length of the tile 402. The spline 1804 can be sized to extend the entire length of the grooves 1802, or to extend beyond the burner tiles 402a, 402b and engage the grooves of additional burner tiles 402. However, it is not essential that the spline 1804 occupy the entire length of the burner tiles 402. For example, according to an embodiment, the grooves 1802 may extend the full length of the burner tiles 402, while the splines 1804 are a fraction of the length of the grooves 1802.

On the one hand, it may be most economical to manufacture the burner tiles 402 with the channels 1802 extending their entire lengths. On the other hand, the splines 1804 occlude perforations 1 10 of the burner tiles along their length, and in many embodiments, a relatively short spline 1804 is sufficient to adequately distribute the stress load. Where a channel 1802 is unoccupied by a spline, the perforations 1 10 of the burner tile 402 will operate adequately to hold a flame under most conditions.

FIG. 19A is a simplified perspective view of a combustion system 1900, including another alternative perforated flame holder 102, according to an embodiment. The perforated flame holder 102 is a reticulated ceramic perforated flame holder, according to an embodiment. FIG. 19B is a simplified side sectional diagram of a portion of the reticulated ceramic perforated flame holder 102 of FIG. 19A, according to an embodiment. The perforated flame holder 102 of FIGS. 19A, 19B can be implemented in the various combustion systems described herein, according to an embodiment. The perforated flame holder 102 is configured to support a combustion reaction 202 of the fuel and oxidant 106 at least partially within the perforated flame holder 102. According to an

embodiment, the perforated flame holder 102 can be configured to support a combustion reaction 202 of the fuel and oxidant 106 upstream, downstream, within, and adjacent to the reticulated ceramic perforated flame holder 102.

According to an embodiment, the perforated flame holder body 108 can include reticulated fibers 1939. The reticulated fibers 1939 can define branching perforations 1 10 that weave around and through the reticulated fibers 1939.

According to an embodiment, the perforations 1 10 are formed as passages through the reticulated ceramic fibers 1939. According to an embodiment, the reticulated fibers 1939 can include alumina silicate. According to an embodiment, the reticulated fibers 1939 can be formed from extruded mullite or cordierite. According to an embodiment, the reticulated fibers 1939 can include Zirconia. According to an embodiment, the reticulated fibers 1939 can include silicon carbide.

The term "reticulated fibers" refers to a netlike structure. According to an embodiment, the reticulated fibers 1939 are formed from an extruded ceramic material. In reticulated fiber embodiments, the interaction between the fuel and oxidant 106, the combustion reaction 202, and heat transfer to and from the perforated flame holder body 108 can function similarly to the embodiment shown and described above with respect to FIGS. 1 -3. One difference in activity is a mixing between perforations 1 10, because the reticulated fibers 1939 form a discontinuous perforated flame holder body 108 that allows flow back and forth between neighboring perforations 1 10.

According to an embodiment, the reticulated fiber network is sufficiently open for downstream reticulated fibers 1939 to emit radiation for receipt by upstream reticulated fibers 1939 for the purpose of heating the upstream reticulated fibers 1939 sufficiently to maintain combustion of a fuel and oxidant 106. Compared to a continuous perforated flame holder body 108, heat conduction paths 212 between fibers 1939 are reduced due to separation of the fibers 1939. This may cause relatively more heat to be transferred from the heat- receiving region 206 (heat receiving area) to the heat-output region 210 (heat output area) of the reticulated fibers 1939 via thermal radiation.

According to an embodiment, individual perforations 1 10 may extend from an input face 1 12 to an output face 1 14 of the perforated flame holder 102.

Perforations 1 10 may have varying lengths L. According to an embodiment, because the perforations 1 10 branch into and out of each other, individual perforations 1 10 are not clearly defined by a length L.

According to an embodiment, the perforated flame holder 102 is

configured to support or hold a combustion reaction 202 or a flame at least partially between the input face 1 12 and the output face 1 14. According to an embodiment, the input face 1 12 corresponds to a surface of the perforated flame holder 102 proximal to the fuel nozzle 1 18 or to a surface that first receives fuel. According to an embodiment, the input face 1 12 corresponds to an extent of the reticulated fibers 1939 proximal to the fuel nozzle 1 18. According to an embodiment, the output face 1 14 corresponds to a surface distal to the fuel nozzle 1 18 or opposite the input face 1 12. According to an embodiment, the input face 1 12 corresponds to an extent of the reticulated fibers 1939 distal to the fuel nozzle 1 18 or opposite to the input face 1 12.

According to an embodiment, the formation of boundary layers 214, transfer of heat between the perforated reaction holder body 108 and the gases flowing through the perforations 1 10, a characteristic perforation width dimension D, and the length L can be regarded as related to an average or overall path through the perforated reaction holder 102. In other words, the dimension D can be determined as a root-mean-square of individual Dn values determined at each point along a flow path. Similarly, 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 T_RH from the input face 1 12 to the output face 1 14 through the perforated reaction holder 102. According to an embodiment, the void fraction (expressed as (total perforated reaction holder 102 volume - fiber 1939 volume)/total volume) is about 70%.

According to an embodiment, 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 10 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.

According to an embodiment, the reticulated ceramic perforated flame holder 102 can include shapes and dimensions other than those described herein. For example, the perforated flame holder 102 can include reticulated ceramic tiles 402 that are larger or smaller than the dimensions set forth above. Additionally, the reticulated ceramic perforated flame holder 102 can include shapes other than generally cuboid shapes.

According to an embodiment, the reticulated ceramic perforated flame holder 102 can include multiple reticulated ceramic burner tiles 402. 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 burner tiles 402. The multiple reticulated ceramic tiles 402 can collectively form a single perforated flame holder 102. Alternatively, each reticulated ceramic burner tile 402 can be considered a distinct perforated flame holder 102.

FIG. 20A is a perspective view of a burner tile 402 including a support member 406 configured to couple the burner tile 402 to a second burner tile 402, according to an embodiment. The support member 406 extends only partially into the burner tile 402. The receiving feature 404 may extend only a few cells, reticulated fibers, or perforations deep into the burner tile 402. The support member 406 can be a ceramic dowel that extends partially into the burner tile 402.

According to an embodiment, the portion of the support member 406 that protrudes from the burner tile 402 is configured to be received into a receiving feature 404 of the second burner tile 402. When the support member 406 is positioned in the receiving feature 404 of the second burner tile 402, the two burner tiles 402 are coupled together. The two burner tiles 402, when coupled together, form a perforated flame holder 102. Alternatively, each individual burner tile 402 can be a perforated flame holder 102.

According to an embodiment, the burner tile 402 can include multiple receiving features 404, each configured to receive a support member 406 substantially similar to the support member 406 shown in FIG. 20A. In one example, multiple lateral faces of the burner tile 402 can include one or more receiving features 404 configured to receive respective support members 406. A perforated flame holder 102 can include an array of burner tiles 402 coupled together by support members 406. According to an embodiment, the support member 406, is configured to couple to a support structure to hold the burner tile 402 in alignment to receive a mixture of fuel and air. According to an embodiment, the burner tile 402 can include multiple support members 406 configured to couple to the support structure.

FIG. 20B is a side-sectional diagram showing details of a portion of the burner tile 402 of FIG. 20A, according to an embodiment. In this embodiment, a support member 406 is positioned in a receiving feature 404 of the burner tile 402. The support member 406 extends partially into the burner tile 402. The burner tile can include additional support mechanisms to facilitate securely and stably coupling the support member 406 to the burner tile 402, such as those described herein in reference to other embodiments.

Arrows indicating X, Y, and Z-axes are provided in many of the drawings. These are intended to aid a viewer in recognizing the relationship of the drawings with each other. Except as explained below, neither the arrows nor the orientation of the structures depicted in the drawings is intended to suggest any necessary orientation of physical structures on which the claims read.

Accordingly, unless defined otherwise, the claims can be read on any structure that otherwise conforms to the claim language, without regard to its orientation.

As used herein, the term longitudinal refers to a direction or dimension along an axis that is substantially parallel to a general direction of flow of fuel and combustion gases through or around a burner tile or perforated flame holder, such as, e.g., the perforated flame holder 102 described with reference to

FIGS. 1 and 2. The Z-axis shown in the drawings extends longitudinally. The term lateral refers to a direction or dimension along an axis that is substantially perpendicular to a longitudinal axis. The X and Y-axes shown in the drawings extend laterally. A lateral surface of an element extends parallel to the Z-axis and can define a lateral extent or dimension of the element.

In many of the drawings, elements are designated with a reference number followed by a letter, e.g., "218a, 218b." In such cases, the letter designation is used where it may be useful in the corresponding description to differentiate between otherwise similar or identical elements. Where the description omits the letter from a reference, and refers to such elements by number only, this can be understood as a general reference to all the elements identified by that reference number, unless other distinguishing language is used.

Ordinal numbers, e.g., first, second, third, etc., are used in the claims according to conventional claim practice, i.e., for the purpose of clearly

distinguishing between claimed elements or features thereof. The use of such numbers does not suggest any other relationship, e.g., order of operation or relative position of such elements, etc. Furthermore, an ordinal number used to refer to an element in a claim does not necessarily correlate to a number used in the specification to refer to an element of a disclosed embodiment on which that claim reads, nor to numbers used in unrelated claims to designate similar elements or features.

The abstract of the present disclosure is provided as a brief outline of some of the principles of the invention according to one embodiment, and is not intended as a complete or definitive description of any embodiment thereof, nor should it be relied upon to define terms used in the specification or claims. The abstract does not limit the scope of the claims. While various aspects and embodiments have been disclosed herein, other aspects and embodiments are contemplated, including the combination of elements selected from different disclosed embodiments to create further embodiments. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the claims.

Claims

CLAIMS What is claimed is:

1 . A combustion system, comprising:

a fuel and oxidant source configured to output a fuel and an oxidant; a perforated flame holder including a group of burner tiles arranged side by side, each burner tile including:

an input face aligned to receive the fuel and the oxidant;

an output face; and

a plurality of perforations extending between the input face and the output face, the perforated flame holder being configured to support a

combustion reaction of the fuel and the oxidant within the perforations, wherein a first burner tile of the plurality of burner tiles includes a receiving feature; and a first support member extending into the first burner tile via the receiving feature and holding the perforated flame holder in alignment to receive the fuel and oxidant into the perforations.

2. The combustion system of claim 1 , wherein the first support member terminates within the first burner tile.

3. The combustion system of claim 2, wherein the first support member is a ceramic dowel.

4. The combustion system of claim 1 , wherein the first support member extends entirely through the first burner tile along an axis substantially parallel to the input face of the first burner tile.

5. The combustion system of claim 1 , wherein a second burner tile of the plurality of burner tiles includes a receiving feature.

6. The combustion system of claim 5, wherein the first support member extends through the first burner tile and into the second burner tile via the receiving feature of the second burner tile.

7. The combustion system of claim 5, further comprising a second support member extending into the second burner tile via the receiving feature of the second burner tile.

8. The combustion system of claim 1 , wherein the plurality of burner tiles includes a first group of burner tiles including the first burner tile, each burner tile of the first group including a respective receiving feature.

9. The combustion system of claim 8, wherein the first support member extends into each burner tile of the first group via the respective receiving features.

10. The combustion system of claim 9, wherein the plurality of burner tiles includes a second group of burner tiles each including a respective receiving feature.

1 1 . The combustion system of claim 10, further comprising a second support member extending into each burner tile of the second group via the respective receiving features.

12. The combustion system of claim 10, wherein the first group of burner tiles is a first row of burner tiles, and wherein the second group of burner tiles is a second row of burner tiles.

13. The combustion system of claim 10, wherein the second support member passes through each burner tile of the second group along an axis transverse to a flow of the fuel from the fuel and oxidant source toward the perforated flame holder.

14. The combustion system of claim 9, wherein the first support member passes through each burner tile of the first group along an axis transverse to a flow of the fuel from the fuel and oxidant source toward the perforated flame holder.

15. The combustion system of claim 1 , wherein the first burner tile includes a second receiving feature.

16. The combustion system of claim 15, further comprising a second support member extending into the first burner tile via the second receiving feature.

17. The combustion system of claim 1 , comprising a fastener coupled to an end of the first support member.

18. The combustion system of claim 17, wherein the fastener is configured to distribute a tension load to a surface of one of the plurality of burner tiles such that while the support member is under tension, the plurality of burner tiles is under compression.

19. The combustion system of claim 1 , wherein the first support member is configured to maintain an arrangement of the burner tiles by providing compression to the burner tiles tending to force the burner tiles together.

20. The combustion system of claim 1 , wherein the first support member is cylindrical in shape.

21 . The combustion system of claim 1 , wherein the first support member is in crosswise section.

22. The combustion system of claim 1 , wherein the plurality of burner tiles is arranged in an arcuate shape.

23. The combustion system of claim 1 , wherein the first support member is a rod that passes through the first burner tile.

24. The combustion system of claim 1 , wherein each burner tile is a reticulated ceramic burner tile.

25. The combustion system of claim 24, wherein each burner tile includes a plurality of reticulated fibers.

26. The combustion system of claim 25, wherein each burner tile includes zirconia.

27. The combustion system of claim 25, wherein each burner tile includes alumina silicate.

28. The combustion system of claim 25, wherein each burner tile includes silicon carbide.

29. The combustion system of claim 25, wherein the reticulated fibers are formed from extruded mullite.

30. The combustion system of claim 25, wherein the reticulated fibers are formed from cordierite.

31 . The combustion system of claim 25, wherein the perforated flame holder is configured to support a combustion reaction of the fuel and oxidant upstream, downstream, and within the burner tiles.

32. The combustion system of claim 25, wherein each burner tile includes about 10 pores per square inch of surface area.

33. The combustion system of claim 25, wherein the perforations of each burner tile are formed as passages between the reticulated fibers.

34. The combustion system of claim 33, wherein the perforations of each burner tile are branching perforations.

35. The combustion system of claim 34, wherein the input face of each burner tile corresponds to an extent of the reticulated fibers proximal to the fuel and oxidant source.

36. The combustion system of claim 34, wherein the output face of each burner tile corresponds to an extent of the reticulated fibers distal to the fuel and oxidant source.

37. A combustion system, comprising:

a fuel and oxidant source configured to output a fuel and an oxidant;

a perforated flame holder including a first group of burner tiles arranged side by side, each burner tile respectively including:

an input face aligned to receive the fuel and the oxidant;

an output face;

combustion reaction of the fuel and the oxidant within the perforations; and

a receiving feature; and

a plurality of support members each extending into a respective burner tile of the first group via the receiving feature and supporting the perforated flame holder in alignment to receive the fuel and oxidant.

38. The combustion system of claim 37, wherein the perforated flame holder includes a second group of burner tiles arranged side by side with the first group of burner tiles, each burner tile of the second group including:

an input face aligned to receive the fuel and the oxidant;

an output face;

a plurality of perforations extending between the input face and the output face, the perforated flame holder being configured to support the combustion reaction of the fuel and the oxidant within the perforations of the second group of burner tiles; and

a receiving feature.

39. The combustion system of claim 38, wherein each support member extends through the respective burner tile of the first group and into a respective burner tile of the second group.

40. The combustion system of claim 37, wherein the support members each terminate within a respective burner tile.

41 . The combustion system of claim 37, wherein the support members are ceramic dowels.

42. The combustion system of claim 37, wherein the each support member extends entirely through a respective burner tile along an axis substantially parallel to the input face of the first burner tile.

43. A method, comprising:

outputting a fuel into a furnace volume;

outputting an oxidant into the furnace volume;

supporting a perforated flame holder including a plurality of burner tiles arranged side by side in alignment to receive the fuel and oxidant by passing a support member into at least one of the burner tiles via a receiving feature of the at least one burner tile, each burner tile including:

an input face;

an output face;

a plurality of perforations extending between the input face and the output face;

receiving the fuel and oxidant into the perforations of each burner tile; and supporting a combustion reaction of the fuel and oxidant within the perforations of each burner tile.

44. The method of claim 44, wherein supporting the perforated flame holder includes passing the support member into multiple burner tiles.

45. The method of claim 43, wherein supporting the perforated flame holder includes passing multiple support members each into a respective burner tile of the plurality of burner tiles.

46. A device, comprising:

a plurality of burner tiles arranged side-by-side, forming a portion of a perforated flame holder, each burner tile having a first receiving feature extending along a first axis parallel to a lateral plane; and

a support member extending into at least one of the burner tiles via the receiving feature of the at least one of the burner tiles.

47. The device of claim 46, wherein the plurality of burner tiles collectively form a perforated flame holder having a plurality of perforations extending longitudinally therethrough.

48. The device of claim 46, wherein the portion of the perforated flame holder is a single row of an array of burner tiles comprised by the perforated flame holder.

49. The device of claim 48, wherein the single row is one of a plurality of rows comprised by the array of burner tiles, each row comprising a respective plurality of burner tiles, and wherein the support member is one of a first plurality of support members, each extending through a first receiving feature formed in each of the plurality burner tiles of a respective one of the plurality of rows.

50. The device of claim 49, wherein a first face of each of the plurality of burner tiles of each of the plurality of rows lies in a common plane.

51 . The device of claim 49, wherein a number of the burner tiles of the plurality of rows of the perforated flame holder are offset longitudinally with respect to others of the burner tiles of the plurality of rows.

52. The device of claim 49, comprising a quantity of bonding agent between the burner tiles of each adjacent pair of burner tiles of each of the plurality of rows.

53. The device of claim 52, comprising a quantity of bonding agent between each adjacent pair of the plurality of rows.

54. The device of claim 49, wherein each of the plurality of burner tiles of each of the plurality of rows comprises a second receiving feature extending parallel to the first receiving feature, the device further comprising a second plurality of support members, each extending through the second receiving feature of each of the plurality of burner tiles of a respective one of the plurality of rows.

55. The device of claim 49, wherein a first one of the plurality of burner tiles of each of the plurality of rows comprises a second receiving feature extending at a non-zero angle relative to the first receiving feature and parallel to the

longitudinal plane, the device further comprising a second support member, extending through the second receiving feature of the first one of the plurality of burner tiles of each of a respective one of the plurality of rows.

56. The device of claim 46, comprising a fastener coupled to an end of the support member.

57. The device of claim 56, wherein the support member is under tension, at least while the device is not in operation.

58. The device of claim 56, wherein the fastener is configured to distribute a tension load to a surface of one of the plurality of burner tiles such that while the support member is under tension, the plurality of burner tiles is under compression.

59. The device of claim 46, wherein the support member is cylindrical in shape.

60. The device of claim 46, wherein the support member is elongate in crosswise section.

61 . The device of claim 46, wherein the plurality of burner tiles is arranged in an arcuate shape.

62. A process, comprising:

arranging a first row of burner tiles with a first support member extending through respective first lateral receiving features in each of a first plurality of burner tiles;

arranging a second row of burner tiles with a second support member extending through respective first lateral receiving features in each of a second plurality of burner tiles; and assembling a perforated flame holder, including positioning the first and second rows of burner tiles adjacent to each other.

63. The process of claim 62, comprising positioning a quantity of bonding agent between adjacent pairs of the first plurality of burner tiles and between adjacent pairs of the second plurality of burner tiles.

64. The process of claim 62, comprising positioning a quantity of bonding agent between tiles of the first row of burner tiles and tiles of the second row of burner tiles.

65. The process of claim 62, comprising applying tension to the first and second support members.

66. The process of claim 62, comprising positioning a third, transverse support member so as to extend through a second lateral receiving feature in one of the first plurality of burner tiles and through a second lateral receiving feature in one of the second plurality of burner tiles.

67. The process of claim 62, wherein the arranging a first row of burner tiles comprises obtaining the first plurality of burner tiles as a preassembled row of burner tiles.

68. The process of claim 67, wherein the arranging a first row of burner tiles comprises positioning the first support member so as to extend through first lateral receiving features formed in each of the first plurality of burner tiles.

69. The process of claim 62, wherein:

the arranging a first row of burner tiles comprises arranging the first row of burner tiles outside of a combustion volume; the arranging a second row of burner tiles comprises arranging the second row of burner tiles outside of the combustion volume; and

the assembling a perforated flame holder comprises positioning the first row of burner tiles in the combustion volume, followed by positioning the second row of burner tiles adjacent to the first row of burner tiles in the combustion volume.

70. The process of claim 62, comprising:

positioning a first segment of the perforated flame holder, including the first and second rows of burner tiles, in the combustion volume; and

following the positioning a first segment of the perforated flame holder in the combustion volume, positioning a second segment of the perforated flame holder adjacent to the first segment in the combustion volume.

71 . The process of claim 70, wherein the positioning the first and second rows of burner tiles adjacent to each other comprises obtaining the first and second rows of burner tiles prepositioned adjacent to each other, as part of the first segment.

72. The process of claim 62, comprising, following the assembling a perforated flame holder, moving the assembled perforated flame holder into a combustion volume.

73. The process of claim 72, wherein the assembling a perforated flame holder comprises obtaining a preassembled perforated flame holder that includes the first and second rows of burner tiles positioned adjacent to each other.

74. A device, comprising:

a first burner tile having a first lateral surface and a first receiving feature extending into the first lateral surface of the first burner tile; a second burner tile having a lateral surface positioned adjacent to the first lateral surface of the first burner tile, and having a first receiving feature extending into the lateral surface of the second burner tile in a position

corresponding to the position of the first receiving feature of the first burner tile, the first and second burner tiles forming a portion of a perforated flame holder; and

a first support member extending between the first receiving feature of the first burner tile and the first receiving feature of the second burner tile.

75. The device of claim 74, wherein each of the first and second burner tiles is a perforated flame holder having a plurality of perforations extending

longitudinally therethrough.

76. The device of claim 74, comprising a third burner tile having a lateral surface positioned adjacent to a second lateral surface of the first burner tile, and having a first receiving feature extending into the lateral surface of the third burner tile in a position corresponding to the position of the first receiving feature of the first burner tile, and wherein the first support member extends from the first receiving feature of the first burner tile to the first receiving feature of the third burner tile.

77. The device of claim 76 wherein the first, second, and third burner tiles are ones of a plurality of burner tiles forming a first row of burner tiles in an array of burner tiles of the perforated flame holder, each having a first receiving feature extending therein.

78. The device of claim 77 wherein the first support member extends through each of the plurality of burner tiles via their respective first receiving features.

79. The device of claim 74, wherein the first burner tile includes a second lateral surface and a second receiving feature extending therein, the device further comprising:

a third burner tile having a lateral surface positioned adjacent to the second lateral surface of the first burner tile, and having a first receiving feature extending into the lateral surface of the third burner tile in a position

corresponding to the position of the second receiving feature of the first burner tile; and

a second support member extending between the second receiving feature of the first burner tile and the first receiving feature of the third burner tile.

80. The device of claim 74, wherein the first and second burner tiles are ones of a plurality of burner tiles forming a row of an array of burner tiles of the perforated flame holder, each of the plurality of burner tiles having a lateral surface positioned adjacent to a lateral surface of another of the plurality of burner tiles, and a receiving feature extending therein, and wherein the first support member is one of a plurality of support members, each extending from a receiving feature of a respective one of the plurality of burner tiles to a receiving feature of an adjacent one of the plurality of burner tiles.

81 . The device of claim 74, wherein:

the first and second burner tiles are ones of a plurality of burner tiles forming an array of rows and columns of burner tiles of the perforated flame holder;

receiving features extend into facing lateral surfaces of each adjacent pair of the plurality of burner tiles, and a respective support member extends between the receiving features extending into the facing surfaces of each adjacent pair of the plurality of burner tiles.

82. The device of claim 74, further comprising a strain relief member positioned and configured to distribute stress between the first support member and each of the first and second burner tiles.

83. The device of claim 82 wherein the strain relief member comprises a layer surrounding the first support member and being relatively flexible and resilient as compared to the first support member and the first and second burner tiles.

84. The device of claim 83 wherein the strain relief member is made from a fibrous ceramic sleeve material that is formed into a flexible tube.

85. The device of claim 83 wherein the strain relief member is formed from a ceramic fabric wrapped at least partially around the first support member.

86. The device of claim 83 wherein the strain relief member comprises a tube of a refractory reticulated foam.

87. The device of claim 74, wherein the first receiving features of the first and second burner tiles are relieved at a transition between the first receiving features and the lateral surface of the respective burner tile.

88. The device of claim 87 wherein the relief comprises a chamfer formed at the transition between each of the first receiving features and the lateral surface of the respective burner tile.

89. The device of claim 88 wherein an angle of the chamfers is selected to be approximately equal to an angle of the support member relative to an axis of the respective first receiving feature while the perforated flame holder is positioned in a furnace.

90. The device of claim 74, wherein the support member includes a plurality of ridges formed on the surface thereof.

91 . The device of claim 90, wherein each of the plurality of ridges has a smallest dimension that is less than a thickness of a perforation wall of the first perforated flame holder.

92. The device of claim 90, wherein each of the plurality of ridges has a smallest dimension that is no greater than about 10% of a thickness of a perforation wall of the first perforated flame holder.

93. The device of claim 74, wherein:

the first receiving features extending into lateral surfaces of the first and second burner tiles each comprise a groove extending along and into the respective lateral surface;

wherein the support member comprises a spline that extends into the grooves of the first and second burner tiles.

94. The device of claim 74, wherein the support member is an elongated support member.

95. A device, comprising:

a first burner tile including:

an input face;

an output face;

a plurality of perforations extending between the input face and the output face; and

a receiving feature; and

a support member extending into the burner tile via the receiving feature, the support member including a portion protruding from the burner tile.

96. The device of claim 95, wherein the support member is a ceramic dowel.

97. The device of claim 95, wherein the protruding portion is configured to couple the first burner tile to a second burner tile by extending into a receiving feature of the second burner tile.

98. The device of claim 95, wherein the protruding portion is configured to couple the first burner tile to a support structure configured to hold the burner tile in a selected position.

99. The device of claim 95, comprising a second burner tile coupled to the first burner tile by the support member.

100. The device of claim 99, wherein the protruding portion of the support member extends into the second burner tile.

101. The device of claim 95, wherein the receiving feature includes an aperture in a lateral face of the first burner tile.

102. The device of claim 95, further comprising a fuel and oxidant source configure to output fuel and oxidant onto the first burner tile.

103. The device of claim 101 , further comprising a support structure coupled to the first burner tile by the protruding portion of the support member and configured to hold the first burner tile in alignment to receive the fuel and oxidant from the fuel and oxidant source.

104. The device of claim 95, wherein the first burner tile includes multiple receiving features and multiple support members.

105. The device of claim 95, wherein the first burner tile is a reticulated ceramic burner tile including a plurality of reticulated fibers extending between the input face and the output face.