US20170146232A1

US20170146232A1 - Burner system including a moveable perforated flame holder

Info

Publication number: US20170146232A1
Application number: US15/372,943
Authority: US
Inventors: Douglas W. KARKOW; Joseph Colannino; Christopher A. Wiklof
Original assignee: Clearsign Combustion Corp
Current assignee: Clearsign Technologies Corp
Priority date: 2014-07-07
Filing date: 2016-12-08
Publication date: 2017-05-25
Also published as: WO2016007564A1

Abstract

A burner includes a perforated flame holder configured to be disposed at a plurality of locations relative to a fuel and air source.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a U.S. National Phase application under 35 U.S.C. §120 of co-pending International Patent Application No. PCT/US2015/039458 entitled “BURNER SYSTEM INCLUDING A MOVEABLE PERFORATED FLAME HOLDER,” filed Jul. 7, 2015 (Docket No.: 2651-218-04), co-pending herewith; which claims priority benefit from U.S. Provisional Patent Application No. 62/021,549, entitled “BURNER SYSTEM INCLUDING A MOVEABLE PERFORATED FLAME HOLDER,” filed Jul. 7, 2014 (Docket No.: 2651-218-02); each of which, to the extent not inconsistent with the disclosure herein, is incorporated by reference.

BACKGROUND

Conventional burners (which may be used in boilers, process heaters, or electrical generation systems, for example) typically hold a flame relatively close to an assembly including a fuel nozzle, air source, and flame holder. The flame holder is typically refractory tile disposed adjacent to the fuel nozzle and air source.
Perforated flame holders are typically supported some distance away from the fuel nozzle and air source.

SUMMARY

Perforated flame holders, also referred to as perforated reaction holders, are disclosed in PCT Patent Application No. PCT/US2014/016632, entitled “FUEL COMBUSTION SYSTEM AND PERFORATED REACTION HOLDER,” filed Feb. 14, 2014 (Docket no.: 2651-188-04); PCT Patent Application No. PCT/US2014/016626, entitled “SELECTABLE DILUTION LOW NOX BURNER,” filed Feb. 14, 2014 (Docket no.: 2651-167-04); PCT Patent Application No. PCT/US2014/016628 entitled “PERFORATED FLAME HOLDER AND BURNER INCLUDING A PERFORATED FLAME HOLDER,” filed Feb. 14, 2014 (Docket no.: 2651-172-04); and PCT Patent Application No. PCT/US2014/016622, entitled “STARTUP METHOD AND MECHANISM FOR A BURNER HAVING A PERFORATED FLAME HOLDER,” filed Feb. 14, 2014 (Docket no.: 2651-204-04); each of which, to the extent not inconsistent with the disclosure and claims herein, is incorporated by reference in its entirety.
As described variously herein, a perforated flame holder can benefit from being positioned a distance from a fuel nozzle, and more particularly at a selected one of a plurality of distances from the fuel nozzle.
According to an embodiment, a burner system includes a fuel and oxidant source and a perforated flame holder configured to receive fuel and oxidant from the fuel and oxidant source and support a combustion reaction collectively in a plurality of perforations defined by the perforated flame holder. A flame holder support mechanism is configured to support the perforated flame holder at each of a plurality of selected positions at respective distances from the fuel and oxidant source. The burner system may include a flame holder actuator configured to move the perforated flame holder between the plurality of positions. The burner system may include a flame holder controller operatively coupled to the flame holder actuator. The flame holder controller may be configured to receive a command to position the flame holder and responsively drive the flame holder actuator to move the perforated flame holder to the commanded position. Additionally or alternatively, the flame holder controller may be configured to sense a combustion parameter, determine a flame holder position, and drive the flame holder actuator to move the perforated flame holder to the determined flame holder position.
According to an embodiment, a burner includes a body defining a combustion chamber having a main axis and a plurality of rails operatively coupled to the body. The plurality of rails are disposed parallel to the main axis. A flame holder in the combustion chamber is configured to be disposed at any one of a plurality of positions along the plurality of rails.
According to an embodiment, a method includes supporting a flame holder in a combustion chamber on a plurality of rails arranged to have a direction component parallel to the main axis of the combustion chamber. Fuel and oxidant are emitted into the combustion chamber toward the flame holder. The fuel and oxidant are received at a proximal surface of the flame holder. A combustion reaction is supported with the fuel and oxidant at least partially in perforations formed to pass through the flame holder from the proximal surface to a distal surface of the flame holder.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified view of a burner including a flame holder configured to be selectively positioned at a plurality of positions along a main axis of a combustion chamber, according to an embodiment.

FIG. 2 is a view of a proximal surface of the flame holder, including a plurality of tiles forming the flame holder, and a sectional view of a plurality of rails configured to support the flame holder of FIG. 1, according to an embodiment.

FIG. 3 is a side sectional view of the burner of FIGS. 1 and 2, according to an embodiment.

FIG. 4 is a perspective view of a perforated flame holder, according to an embodiment.

FIG. 5A is a top view of an assembly including the plurality of rails and a carriage for supporting the flame holder of FIGS. 1-4, according an embodiment.

FIG. 5B is a side view of an assembly of FIG. 5A, according to an embodiment.

FIG. 5C is an end view of the assembly of FIGS. 5A and 5B, according to an embodiment.

FIG. 6A is a view of a portion of a proximal surface of a flame holder having an interlocking arrangement of tiles, according to an embodiment.

FIG. 6B is a view of a portion of a proximal surface of a flame holder having a different interlocking arrangement of tiles, according to another embodiment.

FIG. 6C is a sectional view of a flame holder having a different interlocking arrangement of tiles including tapered surfaces, according to another embodiment.

FIG. 7 is a flow chart of a method for operating the burner of FIGS. 1-5C, according to an embodiment.

FIG. 8 is a flow chart of a method 800 for starting and operating the burner of FIGS. 1-5C, 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.
FIG. 1 is a simplified view of a burner 100 including a flame holder 110 configured to be selectively positioned at a plurality of positions 112 a, 112 b along a main axis 106 of a combustion chamber 104, according to an embodiment. FIG. 2 is a view 200 of a proximal surface 304 of the flame holder 110, including a plurality of tiles 202 forming the flame holder 110, and a sectional view of a plurality of rails 108 configured to support the flame holder 110 of FIG. 1, according to an embodiment. FIG. 3 is a side sectional view of the burner 100 of FIGS. 1 and 2, according to an embodiment. Referring to FIGS. 1-3, according to embodiments, the burner 100 includes a body 102 defining a combustion chamber 104 having a main axis 106. The main axis 106 is defined as a nominal flow axis of at least one of the fuel and/or oxidant. A plurality of rails 108 are operatively coupled to the body 102, the plurality of rails 108 being disposed parallel to the main axis 106. A flame holder 110 is supported in the combustion chamber 104 by the plurality of rails 108. The flame holder 110 configured to be selectively disposed at one of the plurality of positions 112 a, 112 b along the plurality of rails 108. Alternatively, the burner 100 can include bearing surfaces other than rails 108 to selectively support the flame holder 110 at one of the plurality of positions 112 a, 112 b within the combustion chamber 104. For example, the bearing surfaces can include ceramic balls in a track or depression, ceramic cylinders, or any other type of bearing surface suitable for supporting the flame holder 110 within the combustion chamber 104.
The flame holder 110 can include a perforated flame holder 110.
FIG. 4 is a side sectional view of a perforated flame holder 110, according to an embodiment. The perforated flame holder 110 can include a perforated flame holder body 402 defining a plurality of perforations 404 aligned to receive a fuel and oxidant mixture 406 from the fuel and oxidant source 114 (see FIGS. 1 and 3). The perforations 404 can be configured to collectively hold a combustion reaction supported by the fuel and oxidant mixture 406. The combustion reaction can be held substantially within the perforated flame holder body 402 when the perforated flame holder 110 is disposed at one or more of the plurality of (working) positions 112 b (see FIGS. 1 and 3).
The perforated flame holder body 402 can be bounded by a proximal surface 304 (also see FIG. 3) disposed to receive the fuel and oxidant mixture 406 when the perforated flame holder 110 is disposed at one or more of the plurality of positions corresponding to a working position 112 b. The perforated flame holder body 402 is further bounded by a distal surface 302 (also see FIG. 3) facing away from the fuel and oxidant source 114. A peripheral surface 306 (also see FIG. 3) defines a lateral extent of the perforated flame holder 110. The plurality of perforations 404 defined by the perforated flame holder body 402 can extend from the proximal surface 304 to the distal surface 302. In the embodiment 400 of FIG. 4, a tile of the perforated reaction holder body 402 is continuous. That is, the tile 402 is formed from a single piece of material. The embodiment 400 of FIG. 4 also illustrates perforations 404 that are non-branching. That is, the perforated reaction holder body 402 defines perforations 404 that are separated from one another such that no flow crosses between perforations 404.
Optionally, the perforated flame holder 110 can be formed form one or more pieces of material, and the perforations 404 can be branching or non-branching. Non-branching perforations can be referred to as elongated apertures 408.
The perforated reaction holder body 402 defines a plurality of perforations 404 configured to convey the fuel and oxidant 406 and to hold the oxidation reaction supported by the fuel and oxidant 406. The perforated reaction holder body 402 is configured to receive heat from the combustion reaction, hold the heat, and output the heat to the fuel and oxidant 406 entering the perforations 404. The perforations 404 can maintain a combustion reaction of a leaner mixture of fuel and oxidant 406 than is maintained outside of the perforations 404.
The perforated reaction holder 110 has an extent defined by a proximal surface 304 facing the fuel and oxidant source 114 and a distal surface 302 facing away from the fuel and oxidant source 114. The perforated reaction holder body 402 defines the plurality of perforations 404 that can be formed as a plurality of elongated apertures 408 extending from the proximal surface 304 to the distal surface 302.
The perforated reaction holder 110 receives heat from the oxidation reaction and outputs sufficient heat to the fuel and oxidant mixture 406 to maintain the combustion reaction in the perforations 404. The perforated reaction holder 110 can also output a portion of the received heat as thermal radiation 410 to combustor walls of the combustion chamber 104.
Each of the perforations 404 can bound a respective finite portion of the fuel combustion reaction.
In an embodiment, the plurality of perforations 404 are each characterized by a length L defined as a reaction fluid propagation path length between the proximal surface 304 and the distal surface 302 of the perforated reaction holder 110. The reaction fluid includes the fuel and oxidant mixture 406 (optionally including air, flue gas, and/or other “non-reactive” species), reaction intermediates (including transition states that characterize the combustion reaction), and reaction products.
The plurality of perforations 404 can be each characterized by a transverse dimension D between opposing perforation walls 412. According to an embodiment, the length L of each perforation 404 can be 8 or more times the transverse dimension D of the perforation 404. In another embodiment, the length L can be at least twelve times the transverse dimension D. In another embodiment, the length L can be at least sixteen times the transverse dimension D. In another embodiment, the length L can be at least twenty-four times the transverse dimension D. The length L can be sufficiently long for thermal boundary layers 414 formed adjacent to the perforation walls 412 in a reaction fluid flowing through the perforations 404 to converge within the perforations 404, for example. In an alternative embodiment, the length L can be less than 8 times the transverse dimension D.
According to an embodiment, the perforated reaction holder 110 can be configured to cause the fuel combustion reaction to occur within the thermal boundary layers 414 formed adjacent to the perforation walls 412 of the perforations 404. As relatively cool fuel and oxidant 406 approaches the proximal surface 304, the flow is split into portions that respectively travel through individual perforations 404. The hot perforated reaction holder body 402 transfers heat to the fluid, notably within thermal boundary layer 414 that progressively thicken as more and more heat is transferred to the incoming fuel and oxidant 406. After reaching a combustion temperature, the reactants flow while a chemical ignition delay time elapses, after which the combustion reaction occurs. Accordingly, the combustion reaction is shown as occurring within the thermal boundary layers 414. As flow progresses, the thermal boundary layers 414 merge at a point 416. Ideally, the point 416 lies between the proximal surface 304 and distal surface 302. At some point, the combustion reaction causes the flowing gas (and plasma) to output more heat than it receives from the perforated reaction holder body 402. The received heat (from a region 418 is carried to a region nearer to the proximal surface 304, where the heat recycles into the cool reactants.
The perforations 404 can include elongated squares, each of the elongated squares has a transverse dimension D between opposing sides of the squares. In another embodiment, the perforations 404 can include elongated hexagons, each of the elongated hexagons has a transverse dimension D between opposing sides of the hexagons. In another embodiment, the perforations 404 can include hollow cylinders, each of the hollow cylinders has a transverse dimension D corresponding to a diameter of the cylinders. In another embodiment, the perforations 404 can include truncated cones, each of the truncated cones has a transverse dimension D that is rotationally symmetrical about a length axis that extends from the proximal surface 304 to the distal surface 302. The perforations 404 can each have a lateral dimension D equal to or greater than a quenching distance of the fuel.
In one range of embodiments, the plurality of perforations 404 have a lateral dimension D between 0.05 inch and 1.0 inch. Preferably, the plurality of perforations 404 have a lateral dimension D between 0.1 inch and 0.5 inch. For example the plurality of perforations 404 can have a lateral dimension D of about 0.2 to 0.4 inch.
The perforated reaction holder body 402 can include a refractory material. The perforated reaction holder body 402 can include a metal superalloy, for example, or the perforated reaction holder body 402 can be formed from a refractory material such as cordierite or mullite, for example. The perforated reaction holder body 402 can define a honeycomb.
The perforations 404 can be parallel to one another and normal to the proximal and distal surfaces 304, 302. In another embodiment, the perforations 404 can be parallel to one another and formed at an angle relative to the proximal and distal surfaces 304, 302. In another embodiment, the perforations 404 can be non-parallel to one another. In another embodiment, the perforations 404 can be non-parallel to one another and non-intersecting.
Referring still to FIG. 4, the perforated reaction holder body 402 defining the perforations 404 can be configured to receive heat from the (exothermic) combustion reaction at least in heat-receiving regions 418 of perforation walls 412. (e.g., near the distal surface 302 of the perforated reaction holder 110). The perforated reaction holder body 402 defining the perforations 404 can be characterized by a heat capacity. The perforated reaction holder body 402 can be configured to hold heat from the combustion fuel reaction in an amount corresponding to the heat capacity.
The perforated reaction holder body 402 can be configured to transfer heat from the heat-receiving regions 418 to heat-output regions 420 of the perforation walls 412. (e.g., wherein the heat output regions 420 are near the proximal surface 304 of the perforated reaction holder 110). For example, the perforated reaction holder body 402 can be configured to transfer heat from the heat-receiving regions 418 to the heat-output regions 420 of the perforation walls 412 via thermal radiation 410. Additionally or alternatively, the body 402 can be configured to transfer heat from the heat-receiving regions 418 to the heat-output regions 420 of the perforation walls 412 via a heat conduction path 422.
In another embodiment, the perforated reaction holder body 402 can be configured to transfer heat to a working fluid. The working fluid can be configured to transfer heat from a portion of the body near the heat-receiving regions 418 of the perforation walls 412 to a portion of the body near the heat-output regions 420 of the perforation walls 412.
The perforated reaction holder body 402 can be configured to output heat to the boundary layers 414 at least in heat-output regions 420 of perforation walls 412. (e.g., near the proximal surface 304 of the perforated reaction holder 110). Additionally or alternatively, the body 402 can be configured to output heat to the fuel and oxidant mixture 406 at least in heat-output regions 420 of perforation walls 412 (e.g., near the proximal surface 304 of the perforated reaction holder 110), wherein the perforated reaction holder body 402 is configured to convey heat between adjacent perforations 404. The heat conveyed between adjacent perforations can be selected to cause heat output from the combustion reaction portion in a perforation to supply heat to stabilize a combustion reaction portion in an adjacent perforation 404.
The perforated reaction holder body 402 can be configured to receive heat from the fuel combustion reaction and output thermal radiated heat energy 410 to maintain a temperature of the perforated reaction holder body 402 below an adiabatic flame temperature of the fuel combustion reaction. Additionally or alternatively, the perforated reaction holder body 402 can be configured to receive heat from the fuel combustion reaction to cool the fuel combustion reaction to a temperature below an oxides of nitrogen NOx formation temperature and/or cause the gas to remain above an NOx formation temperature for a time insufficient for NOx to be evolved.
The plurality of perforations 404 can include a plurality of elongated squares. In another embodiment, the plurality of perforations 404 can include a plurality of elongated hexagons.
Honeycomb shapes used in the perforated reaction holder 110 can be formed from VERSAGRID® ceramic honeycomb, available from Applied Ceramics, Inc. of Doraville, S.C.
Referring again to FIGS. 1-4, as indicated above, when the perforated flame holder 110 is disposed at one or more of the plurality of positions (particularly at a working position 112 b), the perforated flame holder 110 can hold the combustion reaction substantially within the perforated flame holder body 402 such that a majority of the combustion reaction occurs between the proximal surface 304 and the distal surface 302 of the perforated flame holder 110. For example, at least 80% of the combustion reaction may occur between the proximal surface 304 and the distal surface 302 of the perforated flame holder 110 when the perforated flame holder 110 is disposed at a working position 112 b.
In operation, the perforated flame holder 110 receives heat from the combustion reaction and outputs a portion of the received heat as thermal radiation 410 to heat-receiving structures (e.g., 102) in or adjacent to the combustion chamber 104. Moreover, the perforated flame holder 110 can be configured to receive heat from the combustion reaction, output a portion of the received heat as thermal radiation 410, and output another portion of the received heat to the fuel and oxidant mixture 406 received at the proximal surface 304 of the perforated flame holder 110.
According to an embodiment, the perforated flame holder 110 is formed of tiles 202 having a width dimension W_FTless than the width dimension W_FHof the perforated flame holder 110. In some embodiments, the perforated flame holder 110 can have a width dimension W_FHless than a width W of the combustion chamber 104.
According to an embodiment, the perforated flame holder 110 can have a width dimension W_FHbetween opposite sides of the peripheral surface 306 at least twice a thickness dimension T_FHbetween the proximal surface 304 and the distal surface 302. In another embodiment, the perforated flame holder 110 can have a width dimension W_FHbetween opposite sides of the peripheral surface 306 at least three times a thickness dimension T_FHbetween the proximal surface 304 and the distal surface 302. In other embodiments, the perforated flame holder 110 can have a width dimension W_FHbetween opposite sides of the peripheral surface 306 at least six times a thickness dimension T_FHbetween the proximal surface 304 and the distal surface 302. For example, the perforated flame holder 110 can have a width dimension W_FHbetween opposite sides of the peripheral surface 306 at least nine times a thickness dimension T_FHbetween the proximal surface 304 and the distal surface 302. Alternatively, the width dimension W_FHcan be substantially equal to the thickness dimension T_FH.
The perforated flame holder can also have a length dimension L_FHbetween opposite sides of the peripheral surface 306. According to an embodiment, the length dimension L_FHcan be equal to the width dimension W_FH. Alternatively, the width dimension W_FHand the length dimension can be different.
The perforated flame holder 110 can be formed from a refractory material such as an aluminum silicate material. For example, the perforated flame holder 110 can be formed from mullite or cordierite.
According to an embodiment, the flame holder 110 is formed from 16 cells per square inch, 6 inch thick, 6 inch by 6 inch square cordierite flame holder tiles 202. Tiles 202 are stacked edgewise with high temperature mortar in between. Higher density, 2 inch thick tiles 402 are doubled with the 6 inch thick tiles 202 at and near the centerline of the main axis 106 of the combustion chamber 104 (which may correspond to the center of the flame holder 110). The doubled tiles 202 are 100 cells per square inch, two inch thick, 6 inch by 6 inch square cordierite flame holder tiles 202.
The perforated flame holder tiles 202 can be square, as illustrated in FIG. 4. Alternatively, other flame holder tile 202 shapes are contemplated. FIG. 6A is a view 600 of a portion of a proximal surface 304 of a flame holder 110 having an interlocking arrangement of tiles 202, according to an embodiment. The perforated flame holder tiles 202 each include a keyed shape selected to interlock with neighboring flame holder tiles 202. FIG. 6B is a view 601 of a portion of a proximal surface 304 of a flame holder 110 having a different interlocking arrangement of tiles 202, according to another embodiment.
FIG. 6C is a cross-sectional view 603 of a flame holder 110 including interlocking tiles 202 having tapered surfaces 604, according to an embodiment. According to an embodiment, the keyed shape of the tiles 202 is tapered so as to restrict motion in a particular direction and lock the tiles 202 in place. For example, one or more of the tiles 202 can be tapered such that if the flame holder 110 is suspended above a burner, the influence of gravity would keep the tiles 202 locked together so that the tiles 202 cannot slide past each other.
FIG. 5A is a top view of an assembly 500 including the plurality of rails 108 and a carriage 118 for supporting the flame holder 110 of FIGS. 1-4, according to an embodiment. FIG. 5B is a side view 501 of an assembly 500 of FIG. 5A, according to an embodiment. FIG. 5C is an end view 503 of the assembly 500 of FIGS. 5A and 5B, according to an embodiment.
Referring to FIGS. 1-3 and 5A-5C, the burner 100 can further include a fuel and oxidant source 114 disposed to output fuel and oxidant through the combustion chamber 104 in a direction having a component parallel to the main axis 106. The plurality of positions 112 a, 112 b correspond to a respective plurality of distances from the fuel and oxidant source 114. The plurality of rails 108 can collectively support a weight of the flame holder 110 through a combustion chamber wall 113. The main axis 106 can lie along a horizontal plane.
One or more saddles 116 can be operatively coupled to the flame holder 110 and configured to support the flame holder 110 relative to each of the plurality of rails 108. The carriage 118 can be operatively coupled to each saddle 116 and to the flame holder 110. The carriage 118 can be configured to support the weight of the flame holder 110 through the saddles 116 and the plurality of rails 108.
A mechanical linkage 120 can be operatively coupled to the flame holder 110 and configured to convey physical force to cause the flame holder 110 to move between positions 112 a, 112 b along the rails 108. The mechanical linkage 120 can optionally be cooled using air, water, or other heat transfer fluid. In an embodiment, the mechanical linkage 120 can include a cable. One or more winches 122 can be disposed outside the combustion chamber 104 and operatively coupled to the cable. The one or more winches 122 can include a hand-crank winch, a synchronous drive motor, and/or a servo-controlled motor, for example.
In another embodiment, the mechanical linkage 120 includes a lead screw. A nut (not shown) can be operatively coupled to the carriage 118 and configured to convert rotary motion received from the lead screw into translational motion of the flame holder 110. In another embodiment, the mechanical linkage 120 can include a ball screw and a nut (not shown) operatively coupled to the carriage 118 and configured to convert rotary motion received from the ball screw into translational motion of the flame holder 110.
In some embodiments, the flame holder 110 is configured to be locked into position during operation. In other embodiments, the flame holder 110 can be configured to move between positions during operation of the burner 100.
The plurality of positions 112 a, 112 b can include a first position 112 a adjacent to a fuel and oxidant source 114. When the flame holder 110 is at the first position 112 a, the flame holder 110 may be configured to hold a fuel rich flame adjacent to the fuel and oxidant source 114. In such an operating regime, the rich flame may be referred to as a start-up flame. For example, the flame holder 110 may be selected to be positioned at the first position 112 a and to hold the fuel rich flame adjacent to the fuel and oxidant source 114 during a start-up operating regime. During start-up, the fuel rich flame can cause the flame holder 110 to be heated to an elevated operating temperature. For example, perforated flame holders have been found to operate well at a range of temperatures between about 2400° F. and 2700° F., and can operate beyond this range, depending on conditions. In other embodiments, a start-up flame can be held between the fuel and oxidant source 114 and the perforated flame holder 110 during start-up. The start-up flame is used to raise the perforated flame holder 110 to an operating temperature.
As described above, the flame holder 110 includes a distal surface 302 disposed away from the fuel and oxidant source 114. The flame holder 110 may be configured to hold a conventional flame extending away from the flame holder distal surface 302 when the flame holder 110 is at the first position 112 a. When the flame holder 110 is at the first position 112 a, the flame holder 110 can be configured to pass fuel and air through the flame holder 110 to the flame holder distal surface 302.
The plurality of positions 112 a, 112 b can additionally or alternatively include at least one working position 112 b distal from the fuel and oxidant source 114. The flame holder 110 can be configured to hold a lean combustion reaction substantially contained by the plurality of perforations 404 in the flame holder 110, between the flame holder proximal surface 304 and the flame holder distal surface 302 when the flame holder 110 is at the distal working position 112 b. The flame holder 110 can be configured to receive mixed fuel and air at the proximal surface 304 of the flame holder 110 when the flame holder 110 is disposed at the distal working position 112 b.
FIG. 7 is a flow chart of a method 700 for operating the burner 100 of FIGS. 1-5C, according to an embodiment. The method 700 includes step 714 wherein a flame holder is supported in a combustion chamber having a main axis on a plurality of rails arranged to have a direction component parallel to the main axis. Supporting the flame holder on the plurality of rails can include supporting the flame holder against gravitational acceleration.
In step 702, fuel and oxidant are emitted into the combustion chamber toward the flame holder. In step 704, the fuel and oxidant are received at a proximal surface of the flame holder. Proceeding to step 706, a combustion reaction is supported with the fuel and oxidant at least partially in perforations formed to pass through the flame holder from the proximal surface to a distal surface of the flame holder.
According to an embodiment, supporting the flame holder on the plurality of rails in step 714 includes supporting the flame holder at a selected position along the plurality of rails.
The selected position can be adjacent to a fuel and oxidant source, for example during a start-up procedure such as when the flame holder is below an operating temperature. During start-up, the method 700 can include a step (not shown) wherein a conventional flame is supported distal from the distal surface of the flame holder. During start-up, the combustion reaction can be supported only at least partially within the perforations in an annular region of the flame holder characterized by a mass flow velocity below a higher mass flow velocity through a portion of the flame holder axial to the annular region. Alternatively, during start-up, the combustion reaction can be supported only at least partially within the perforations in an elliptical region of the flame holder characterized by a mass flow velocity below a higher mass flow velocity through a portion of the flame holder circumferential to the elliptical region.
The selected position (e.g., see 112 b, FIGS. 1 and 3) can be away from the fuel and oxidant source, such as when the flame holder supports an ultra-low NOx production combustion reaction. During operation, the selected position may be a position away from the fuel and oxidant source only when the flame holder is within a nominal operating temperature range.
The selected position can be away from the fuel and oxidant source. The method 700 can further include supporting a conventional flame with the fuel and oxidant between the fuel and oxidant source and the flame holder, whereby the conventional flame heats the flame holder to a nominal operating temperature range.
Additionally or alternatively, the method 700 can include heating the flame holder to a nominal operating temperature range before emitting the fuel and oxidant toward the proximal surface of the flame holder.
The method 700 can further include step 712 wherein the flame holder is moved to a selected position along the plurality of rails. In step 710, the flame holder position in the combustion chamber can be selected. In step 708, a combustion reaction parameter can be sensed. For example, sensing a combustion reaction parameter can include receiving infrared energy from the flame holder, wherein the infrared energy corresponds to a temperature of the flame holder. Additionally or alternatively, sensing a combustion reaction parameter can include receiving ultraviolet energy from the flame holder, the ultraviolet energy corresponding to the presence of the combustion reaction (e.g., evolution of hydroxyl groups).
FIG. 8 is a flow chart of a method 800 for operating the burner 100 of FIGS. 1-5C, according to an embodiment. In step 802 the method begins. In step 804 the furnace is purged for a selected time. In step 806 the furnace is checked to ensure that oxygen (O₂) concentration is greater than 20%. In step 808 the furnace is checked to ensure that the concentration of carbon monoxide (CO) within the furnace is less than 50 ppm. When the O₂and CO concentrations are above 20% and below 50 ppm, respectively, the pilot light is lit in step 810. In step 812 the pilot light is proved. If the pilot light is in proper operating condition, the start-up flame is lit in step 814. In step 816 the start-up flame is checked to ensure that the start-up flame is in proper operating condition. In step 818 the start-up flame is monitored. If the start-up flame is in proper condition in step 820 then the method proceeds to step 824 at which the perforated flame holder is preheated to a threshold operating temperature. At step 826 if the perforated flame holder is above the threshold temperature the method proceeds to step 828 in which the flame is transferred to the perforated flame holder. In step 830 transfer of the flame is proven. If the flame has properly transferred to the perforated flame holder then, in step 832, the perforated flame holder is monitored. In step 834 if the flame in the perforated flame holder is in proper condition then the method returns to 832 in which the perforated flame holder is monitored. If the flame held by the perforated flame holder is not okay then the method proceeds to step 822 in which the furnace is shut down. In step 830, if the flame has not properly transferred then the method proceeds to step 822 in which the furnace is shut down. In step 820 if the start-up flame is not in proper condition then the method proceeds to step 822 in which the furnace is shut down. In step 836, a manual interrupt causes the method to proceed to step 822 in which the furnace is shut down.
While various aspects and embodiments have been disclosed herein, other aspects and embodiments are contemplated. 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 following claims.

Claims

1. A burner system, comprising:

a fuel and oxidant source;

a perforated flame holder configured to receive fuel and oxidant from the fuel and oxidant source and support a combustion reaction collectively in a plurality of perforations defined by the perforated flame holder; and

a flame holder support mechanism configured to support the perforated flame holder at each of a plurality of selected positions at respective distances from the fuel and oxidant source.

2. The burner system of claim 1, further comprising:

a flame holder actuator configured to move the perforated flame holder between the plurality of positions.

3. The burner system of claim 2, further comprising:

a flame holder controller operatively coupled to the flame holder actuator;

wherein the flame holder controller is configured to receive a command to position the flame holder and responsively drive the flame holder actuator to move the perforated flame holder to the commanded position.

4. The burner system of claim 2, further comprising:

a flame holder controller operatively coupled to the flame holder actuator;

wherein the flame holder controller is configured to sense a combustion parameter, determine a flame holder position, and drive the flame holder actuator to move the perforated flame holder to the determined flame holder position.

5. A burner, comprising:

a body defining a combustion chamber having a main axis;

a plurality of rails operatively coupled to the body, the plurality of rails being disposed parallel to the main axis; and

a flame holder disposed in the combustion chamber and configured to be disposed at a plurality of positions along the plurality of rails.

6. The burner of claim 5, wherein the flame holder comprises a perforated flame holder.

7. The burner of claim 5, wherein the flame holder comprises a perforated flame holder including a perforated flame holder body defining a plurality of perforations aligned to receive the fuel and oxidant mixture from the fuel and oxidant source;

wherein the perforations are configured to collectively hold a combustion reaction supported by the fuel and oxidant mixture.

8. The burner of claim 7, wherein the perforated flame holder is configured to hold the combustion reaction substantially within the perforated flame holder body when the perforated flame holder is disposed at one or more of the plurality of positions.

9. The burner of claim 7, wherein the perforated flame holder body is bounded by a proximal surface disposed to receive the fuel and oxidant mixture when the perforated flame holder is disposed at one or more of the plurality of positions corresponding to a working position, a distal surface facing away from the fuel and oxidant source, and a peripheral surface defining a lateral extent of the perforated flame holder; and

wherein the plurality of perforations defined by the perforated flame holder body extend from the proximal surface to the distal surface.

10. The burner of claim 7, wherein, when the perforated flame holder is disposed at one or more of the plurality of positions, the perforated flame holder is configured to hold the combustion reaction substantially within the perforated flame holder body such that a majority of the combustion reaction occurs between a proximal surface and a distal surface of the perforated flame holder.

11. The burner of claim 7, wherein, when the perforated flame holder is disposed at one or more of the plurality of positions, the perforated flame holder is configured to hold the combustion reaction substantially within the perforated flame holder body such that at least 80% of the combustion reaction occurs between a proximal surface and a distal surface of the perforated flame holder.

12. The burner of claim 7, wherein, when the perforated flame holder is disposed at one or more of the plurality of positions, the perforated flame holder is configured to receive heat from the combustion reaction and output a portion of the received heat as thermal radiation to heat-receiving structures in or adjacent to the combustion chamber.

13. The burner of claim 7, wherein, when the perforated flame holder is disposed at one or more of the plurality of positions, the perforated flame holder is configured to:

receive heat from the combustion reaction;

output a portion of the received heat as thermal radiation; and

output another portion of the received heat to the fuel and oxidant mixture received at a proximal surface of the perforated flame holder.

14. The burner of claim 7, wherein the perforated flame holder has a width dimension W_FHbetween opposite sides of the peripheral surface at least twice a thickness dimension T_FHbetween the proximal surface and a distal surface.

15. The burner of claim 14, wherein the perforated flame holder includes a plurality of tiles coupled together and each having a width dimension W_FTless than the width dimension W_FHof the perforated flame holder.

16. The burner of claim 14, wherein the perforated flame holder has a width dimension W_FHbetween opposite sides of the peripheral surface at least three times a thickness dimension T_FHbetween the proximal surface and the distal surface.

17. The burner of claim 14, wherein the perforated flame holder has a width dimension W_FHbetween opposite sides of the peripheral surface at least six times a thickness dimension T_FHbetween the proximal surface and the distal surface.

18. The burner of claim 14, wherein the perforated flame holder has a width dimension W_FHbetween opposite sides of the peripheral surface at least nine times a thickness dimension T_FHbetween the proximal surface and the distal surface.

19. The burner of claim 7, wherein the perforated flame holder has a width dimension W_FHless than a width W of the combustion chamber.

20. The burner of claim 7, wherein the perforated flame holder is formed from a refractory material.

21. The burner of claim 7, wherein the perforated flame holder is formed from an aluminum silicate material.

22. The burner of claim 21, wherein the perforated flame holder is formed from mullite or cordierite.

23. The burner of claim 7, wherein the perforated flame holder tiles are rectangular.

24. The burner of claim 7, wherein the perforated flame holder tiles are square.

25. The burner of claim 7, wherein the perforated flame holder tiles each include a keyed shape selected to interlock with neighboring flame holder tiles.

26. The burner of claim 25, wherein the perforated flame holder tiles are tapered to restrict motion in one direction.

27. The burner of claim 5, further comprising:

a fuel and oxidant source disposed to output fuel and oxidant through the combustion chamber in a direction having a component parallel to the main axis;

wherein the plurality of positions correspond to a respective plurality of distances from the fuel and oxidant source.

28. The burner of claim 5, wherein the plurality of rails collectively support a weight of the flame holder through a combustion chamber wall.

29. The burner of claim 5, wherein a largest dimension of the perforated flame holder is substantially normal to the fluid flow direction.

30. The burner of claim 5, further comprising:

one or more saddles operatively coupled to the flame holder and configured to support the flame holder relative to each of the plurality of rails.

31. The burner of claim 30, further comprising:

a carriage operatively coupled to each saddle and to the flame holder;

wherein the carriage is configured to support the weight of the flame holder through the saddles and the plurality of rails.

32. The burner of claim 31, further comprising:

a mechanical linkage operatively coupled to the flame holder, the mechanical linkage being configured to convey physical force to cause the flame holder to move between positions along the rails.

33. The burner of claim 32, wherein the mechanical linkage comprises a cable.

34. The burner of claim 33, further comprising one or more winches disposed outside the combustion chamber and operatively coupled to the cable.

35. The burner of claim 34, wherein the one or more winches comprises a hand-crank winch.

36. The burner of claim 34, wherein the one or more winches comprises a synchronous drive motor.

37. The burner of claim 34, wherein the one or more winches comprises a servo-controlled motor.

38. The burner of claim 32, wherein the mechanical linkage comprises a screw; and

further comprising:

a nut operatively coupled to the carriage and configured to convert rotary motion received from the lead screw into translational motion of the flame holder.

39. The burner of claim 30, wherein the mechanical linkage comprises a ball screw; and

further comprising:

a nut operatively coupled to the carriage and configured to convert rotary motion received from the ball screw into translational motion of the flame holder.

40. The burner of claim 5, wherein the flame holder is configured to move between positions during operation of the burner.

41. The burner of claim 5, wherein the flame holder is configured to be locked into position during operation.

42. The burner of claim 5, wherein the plurality of positions include a first position adjacent to a fuel and air source.

43. The burner of claim 42, wherein the flame holder is configured to hold a fuel rich flame adjacent to the fuel and air source when the flame holder is at the first position.

44. The burner of claim 43, wherein the flame holder is selected to be positioned at the first position and to hold the fuel rich flame adjacent to the fuel and air source during a start-up operating regime;

whereby the fuel rich flame causes the flame holder to be heated to an elevated operating temperature.

45. The burner of claim 42, wherein the flame holder includes a distal surface disposed away from the fuel and air source; and

wherein the flame holder is configured to hold a conventional flame extending away from the flame holder distal surface when the flame holder is at the first position.

46. The burner of claim 42, wherein the flame holder includes a distal surface disposed away from the fuel and oxidant source; and

wherein the flame holder is configured to pass fuel and air through the flame holder to the flame holder distal surface when the flame holder is at the first position.

47. The burner of claim 5, wherein the plurality of positions includes at least one working position distal from the fuel and oxidant source.

48. The burner of claim 5, wherein the flame holder is configured to hold a lean combustion reaction substantially contained by a plurality of perforations formed through the flame holder when the flame holder is at the distal working position.

49. The burner of claim 48, wherein the flame holder includes a proximal surface disposed toward the fuel and air source; and

wherein the flame holder is configured to receive mixed fuel and air at the proximal surface of the flame holder when the flame holder is disposed at the distal working position.

50.-70. (canceled)

71. A burner, comprising:

a body defining a combustion chamber having a main axis;

a plurality of bearing surfaces operatively coupled to the body; and

a flame holder disposed in the combustion chamber and supported by the plurality of bearing surfaces, the flame holder including:

a distal surface;

a proximal surface; and

a plurality of perforations extending between the distal and proximal surfaces, the plurality of bearing surfaces being configured to selectively support the flame holder at a plurality of positions within the combustion chamber.

72. The burner of claim 71, wherein the bearing surface includes rolling cylinders or balls.

73. The burner of claim 71, wherein the bearing surface includes rails.