Title of Invention	A METHOD FOR BURNING FUEL IN A COMBUSTION ZONE AND OPERATING OF A BURNER FOR THE SAME
Abstract	A method for burning fuel in a combustion zone comprising ; providing a fuel lean mixture of fuel and air; delivering said mixture to a centrally located point adjacent a face of a burner tile, said point being disposed adjacent said combustion zone; causing said mixture to flow radially outwardly from said p.oint in a. plurality of streams across the face of said tile; combusting the fuel in said mixture in an area of said combustion zone adjacent said face; and providing staged fuel to said zone at a location spaced from said area; and combusting said staged fuel' in an environment containing flue gases and not more than about 4% oxygen by volume.

Title of Invention

A METHOD FOR BURNING FUEL IN A COMBUSTION ZONE AND OPERATING OF A BURNER FOR THE SAME

Abstract

A method for burning fuel in a combustion zone comprising ; providing a fuel lean mixture of fuel and air; delivering said mixture to a centrally located point adjacent a face of a burner tile, said point being disposed adjacent said combustion zone; causing said mixture to flow radially outwardly from said p.oint in a. plurality of streams across the face of said tile; combusting the fuel in said mixture in an area of said combustion zone adjacent said face; and providing staged fuel to said zone at a location spaced from said area; and combusting said staged fuel' in an environment containing flue gases and not more than about 4% oxygen by volume.

Full Text	ORIGINAL 612/MUMNP/2004 I FORM 2 THE PATENTS ACT, 1970 (39 of 1970) COMPLETE SPECIFICATION [See section 10; Rule 13] A METHOD FOR BURNING FUEL IN A COMBUSTION ZONE AND OPERATING OF A BURNER FOR THE SAME JOHN ZINK COMPANY L.L.C., A CORPORATION ORGANIZED AND EXISTING UNDER THE LAWS OF SWITZERLAND WHOSE ADDRESS IS 11920, EAST APACHIE, TULSA OK 74116, U.S.A. GRANTED 28/12/2004 THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE NATURE OF THIS INVENTION AND THE MANNER IN, WHICH IT IS TO BE PERFORMED. BACKGROUND OF THE INVENTION Field of the Invention . The present invention relates to the field of radiant wall burners. In particular the invention relates to radiant wall burners wherein a number of technologies are combined in a single burner arrangement so as to achieve low i NOx and low noise. The State of the Prior Art Reduction and/or abatement of NOx in radiant burners has always been a desirable aim. Some NO, abatement has been achieved in the past by staging a portion of the gaseous fuel. Low pressure staged gas may be introduced into the combustion zone either from low pressure gas tips arranged around the periphery of the burner or from a center gas tip which protrudes through the center of the end cap! of the radiant burner nozzle. These arrangements have not always been successful because, for NO, abatement purposes, the stage fuel should not be introduced into areas of the combustion zone where the oxygen concentration is greater than about 4% by volume. Prior art proposals for gas fuel burners include those described in US-A-5271729, US-A-4257762 and US-A-3684424. The burner of US-A- 3684424 includes a burner tube delivers a mixture of air and gas to radially facing openings through which the gas-air mixture is directed across a radially ridged tile face. US-A-4257762 discloses a generally similar arrangement but with the openings being inclined to direct the gas-air mixture rearwardly towards the tile face from the forward end of the burner tube. The burner of US-A-5271729 includes a burner tube with openings at the forward end to direct the gas and air mixture radially outwardly at the centre of a cup-shaped tile face, and a second stage nozzle to which a gas and air mixture is supplied through an axial second stage premix tube, projects beyond the end of the burner tube and has ports arranged to direct the gas and air mixture radially and adjacent the front face of the tile. SUMMARY; OF THE INVENTION Various problems encountered in prior art burners are addressed by the concepts land principles of the present invention. In particular, the invention addresses the ever present need for NO, abatement. In accordance with one aspect of the invention, it has been found that when gas is buned in a staged manner it may sometimes be responsible only for about 6 ppm (vol) of the total NO, emissions of an individual burner. Accordingly it has been thought to be desirable to adapt the concept of fuel staging to radiant wall burners. Several different configurations have been tried, some more successful than others, but none with complete satisfaction. In some configurations, staged fuel has been delivered through a plurality of tubes at very low pressure around the circumference of the burner. In such a case the staged fuel is introduced in proximity to a combusting mixture which is still quite rich in oxygen. This excess oxygen leads to higher flame temperatures and higher NOx content in flue gases. In other configurations, staged gas has been introduced into the combustion zone from the axially distal end of the premix discharge nozzle. This configuration, where the staged fuel is injected coaxially at the center line of the premix burner assembly, has been somewhat more successful in achieving lower NO, emissions that the first configuration discussed above, at least in part due to the fact that the introduction point is located in spaced relationship to the face of the tile as well as away from the oxygen rich stream leaving the premix discharge nozzle. The down side of this particular methodology is that the momentum of the staged gas jet can and often does pull the primary oxygen rich premixed stream into the jet 'as an entrained flow thereby increasing the availability of excess oxygen as well as the production of NO,. This problem is exacerbated in applications requiring a multiplicity of individual burners in an array because of the interactions between burners. In accordance with an important aspect of the invention, a low NO, burner nozzle assembly is provided for a radiant wall burner. The assembly includes an elongated hollow burner tube, a discharge nozzle and n central. staged fuel nozzle. The burner tube has a central, longitudinally exuding axis and defines a conduit extending along the axis for supplying a mixture of fuel and air to a radiant combustion area of a combustion zone that extends radially and surrounds the nozzle assembly. This mixture may desirably be fuel lean. The discharge nozzle is mounted on the tube at a downstream end of the conduit i adjacent the combustion zone, and the same is adapted for receiving the mixture of fuel and air; from the conduit and directing the same into the radiant combustion area in an essentially radial direction relative to the axis of the tube. The discharge nozzle includes an end cap that is to prevent flow of the mixture in a direction along the axis. Thus, the mixture is caused to flow through the passageways in a generally radial direction. The staged fuel burner nozzle includes a length of tubing which extends along the axis of the conduit, and a staged burner nozzle tip at a downstream end of the length of tubing. The staged fuel burner nozzle is arranged so, as to protrude axially through a hole in the end cap. The tip has a fuel delivery orifice therein for delivering fuel to the combustion zone in spaced relationship; to the radiant combustion area of the zone. According to one construction in accordance with the invention, the delivery orifice is disposed so as to introduce fuel gas into the combustion zone at an upward and outward angle relative to a plane that is perpendicular to the axis. Preferably the angle may be at least about 30°. In another construction in accordance with the invention, the delivery orifice is disposed to introduce fuel gas in a direction along the axis. The discharge nozzle may include a plurality of flow directing members arranged in an array which extends circumferentially around the discharge nozzle and the members may desirably be arranged to define therebetween a plurality of passageways which extend in a generally radial direction relative to the axis. Preferably, the flow directing members may be arranged so that some of the passageways therebetween have a larger flow area than others. Desirably, the members may be in the form of plates which are essentially rectangular in shape. Ideally, the passageways may also extend ,„ an ax.al direction. In a much preferred form of the invention, the end cap may have a lateral edge which is located at a first radial distance from the axis, and the members may each have an outer edge located at a second radial distance fix,™ the axis The secoiid radial distance ideally may be greater than the first radial distance such that passageways defined by the members extend radially outward beyond the lateral edge of the end cap. accordance with another preferred form of the invention, the nozzle may inclide an internal baffle positioned and arranged to redirect at least a portion of the mixture flowing through the conduit and cause the same to flow through the passageways in a generally radial direction. The staged fuel burner nozzle may be positioned such that a downstream portion of the length of tubing protrudes beyond the end cap so that the tip is positioned in axially spaced relationship relative to the end cap. Ideally, in this particularly desirable form of the invention, the low NO, burner nozzle may include an elongated protective sheath disposed in surrounding relationship to the protruding portion of the length of tubing and the tip. Such sheath may desirably include an openihg disposed in alignment with the orifice. The sheath may also be provided with one or more vent openings configured to permit gases between the sheath and the length of tubing to escape into the combustion zone. In accordance ' with the foregoing aspects of the invention, the staged burner nozzle may be of significant value, regardless of the form of the discharge nozzle. Thus, the staged burner tip of the invention may be used with any sort of radial discharge nozzle that operates to spread a combustible mixture of fuel and air radially across the face of a radiant tile. In an embodiment the burner tube has an outer wall surrounding said conduit, ah inlet for a mixture of fuel and air is located at the end of the burner tube opposite the discharge nozzle, an air passageway is located outside the wall of the burner tube, and at least one port extends through said outer wall at a location between the discharge nozzle and said inlet intercommunicating the conduit and thejair passage. The burner tube may comprise a venturi tube having a throat that is in communication with an air supply and a source of fuel gas under pressure. The venturi tube may desirably be arranged such that the flow of fuel gas through the throat induces flow of air from the air source whereby the mixture of fuel and air is created in the throat and caused to flow toward the discharge nozzle. The invention also provides a low NO, radiant wall burner comprising a buner tile having a central opening surrounded by a radiant tile face and an elongated low NOx burner nozzle assembly as described above that extends through such opening. The face of the burner tile may be either dished or flat. In addition, the nozzle assembly and/or burner of the invention can be used for performing a method for burning fuel in a combustion zone comprising providing a fuel lean mixture of fuel and air, delivering said mixture to a centrally located point adjacent a face of a burner tile, said point being disposed adjacent said;combustion zone, causing said mixture to flow radially outwardly from the centrally located point in a plurality of streams across the face of the tile, combusting the fuel in said mixture in an area of the combustion zone adjacent the face of the tile, providing a staged fuel to said zone at a location spaced from said area, and combusting said staged fuel in an environment containing flue gases and not more thaniabout 4% oxygen by volume. In a preferred low NO, burner nozzle assembly which includes at least one port extending through the outer wall of the burner tube at a location between the discharge nozzle and the inlet to communicate the conduit with an air passageway located outside the burner tube, the port has a center axis which is essentially perpendicular to the central axis of the tube. Alternatively, the port may have a center axis which is at an angle relative to the central axis of the tube. Ideally the assembly may include a plurality of ports extending through the wall of the tube at respective locations between the discharge nozzle and the inlet. In one preferred form of the invention, the ports may be arranged in one or more rows which extend around the outer wall of the tube. The nozzle assembly having at least one port extending through the wall of the burner tube may be used as a component of a low NO, radiant wall buner that includcs a burner tile having a centra, opening , In such a case, nozzle assembly may extend through the central opening of ,e tile. Desirably, the discharge nozzle may-include a plurahty of now direchng members such are arrged to define therebetween a plurality of passageways which extend in generally radial directions relative to the axis of the buner tube, and an end cap flowing from; the end of the conduit and cause the same to How through said passage ays in a generally radial direction so that when ignited, the redirected ture of fuel and air provides a generally laterally extending flame having an outer peripheral extremity at a location in said zone spaced radially from said axis Also described herein is a method for operating a burner which includes the steps of causing a mixture of fuel and air to flow toward a centrally ,ocated point! adjacent a face of a burner tile, causing a stream of at least one of additional air and recirculated flue gas to flow toward a location.djacent said face which is spaced laterally from said point, and separating a portion of sa.d mixture and intermixing the same with said stream to thereby create an ultra lean admixture capable of flameless oxidation before the same reaches said location. More particularly, the method may include the steps of causing a mixture of fuel and air to flow toward a centrally located point adjacent a face of a burner t,lc. separating a first portion of said mixture into a plurality of separate streams and causing said streams to flow radially outwardly from said point across the face of said tile, causing said streams to combust to form flames, each having an outer peripheral iirminus spaced radially from said point, providing secondary an to said flame at a location adjacent said termini, adding a second portion of said mixture to slid secondary air at a location upstream from said location to create an admixture capable of flameless oxidation at the face of said tile, and flameless.y oxidizing said admixture at said face to create relatively cool oxidation products. Oxidation products may be admixed with the combusting gases to thereby dilute and cool the same, and a flow of recirculated flue gas may be provided to said flame at a location adjacent said termini. Prior art burners of the premix type of design have not been able to utilize as many NOx abatement technologies in a single burner as are provided in the burner arrangements, of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view, partly in cross-section, of a low NOx radiant wall burner which; embodies the concepts and principles of the invention; FIG. 2 is a side elevational view of the nozzle arrangement of the burner of FIG. 1; FIG. 3 is a schematic plan view of a preferred embodiment of the discharge nozzle of the nozzle arrangement of FIG. 2. FIG. 4 is an enlarged elevational, cross-sectional view of the discharge noz/.le of FIG.3; FIG. 5 is ah enlarged view, partly in cross-section, of the discharge nozzle of F IG.3; FIG. 6 is an enlarged view, similar to FIG. 5, which is partly in cross section to illustrate anjembodiment of an internal baffle; FIG. 7 is a schematic view of the nozzle arrangement of FIG. 1; FIGS. 8A and 8B respectively are side elevational and plan views an embodiment of a central staged nozzle tip for the nozzle arrangement of FIG. 2; FIG. 9 is a side elevational view of an embodiment of a tile for use with the burner of FIG.1; FIG. 10 is a plan view of the tile of FIG. 9; FIG. 11 is, a schematic side elevational view of one embodiment of a nozzle, arrangement that is useful in connection with the invention. FIG. 12 is a schematic side elevational view of an alternative embodiment of a nozzle arrangement that is useful in connection with the invention; FIG. 13 is a schematic side elevational view of another alternative embodiment of a nozzle arrangement that is useful in connection with the invention; FIG. 14 is a schematic side elevational view of yet another alternative embodiment of a nozzle arrangement that is useful in connection with the invention; FIG. 15 is a side elevational view of yet another burner arrangement which embodies the concepts and principles of the invention; FIG. 16 is an enlarged cross sectional view of the discharge nozzle of the burner of FIG. 15; and FIG. 17 is a schematic view illustrating the operation of the burner of FIG. 15, including a schematic showing of the flow paths of the several combustion and flameless oxidation streams. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION A burner 10 which embodies the concepts and principles of the invention is illustrated in Fig. 1 where it can be seen that the same includes a burner tile 12 having a centrally disposed opening 14 and a burner nozzle assembly 16 including a burner discharge nozzle 18 which protrudes through opening 14 and extends into a combustion zone 20. The burner 10 may also include conventional components such as a muffler 22, an air door 24 and an inlet tube 26 facilitating connection to a source of fuel gas. With reference to Fig. 2, it can be seen that the nozzle assembly 16 may include spud 28 whereby a supply of fuel gas is supplied to the nozzle assembly 16. Spud 28 is connected to a coupling 42 (See Fig. 7) whereby fuel gas is supplied to the discharge nozzle 18. The assembly 16 also includes an elongated, hollow burner tube 30 and a base 32. Tube 30 extends between base 32 and discharge nozzle 1.8 and provides a passageway for primary combustion air and accommodates the gas supply system (not shown) which interconnects spud 28 and coupling 42. Discharge nozzle 18 preferably includes a fuel distribution section 36 and i an end cap 38. With reference to Figs. 5, 6 and 7, it can be seen that the downstream portion 34 of tube 30 may preferably include a venturi tube 40 whereby fuel gas being ejected through an opening 44 in coupling 42 induces a flow of combustion air from the interior of tube 30. Preferably coupling 42 may be provided with a plurality of openings 44 as shown. The fuel gas ejected through the openings 44 mixes with the induced air to preferably form a combustible fuel lean fuel gas/air mixture which travels through portion 34 of tube 30 toward and into fuel distribution section 36. Fuel distribution section 36 is illustrated in Figs. 3 and 4. Section 36 includes a plurality of fin-like flow directing members 46 and 48 which define therebetween a plurality of passageways 50 and 52 which extend in a generally radial direction relative to the central axis 54 of the nozzle assembly 16. The members 46 and 48 may be sized and arranged such that the passageways 50 defined between adjacent members 46 may be larger in cross-sectional flow area than the passageways 52 denned between adjacent members 48. In operation, the fuel/air mixture flows through portion 34 of tube 30 in a direction which is generally parallel to axis 54. As the air/fuel mixture approaches end cap 38, the air/gas mixture is redirected so that it flows radially oui ward through the passageways 50 and 52. It is to be noted in this regard that the respective outer extremities 46a and 48a of members 46 and 48 are preferably spaced further from axis 54 than the outer edge 38a of cap 38. This provides respective openings 50a and 52a (see Fig!'5) at the axially outer ends of passageways 50 and 52 which permit a portion of the air/fuel combustible mixture adjacent thereto to bend slightly and flow tow lrd zone 20 rather than in a direction at right angles to axis 54.; With particular reference to Fig. 3, it can be seen that the membei s 46 and 48 may be arranged so as to provide respective groups 56 and 58 of passageway; 50 and 52. As shown, each group 56 includes five passageways 50 and each group 58 includes five passageways 52. As can clearly be seen from Fig. 3, the passageways 50 are wider than the passageways 52 so that the cross sectional flow areas provided by passageways 50 are greater than the cross-sectional flow areas provided by passageways 52. As shown, the groups 56 and 58 are arranged around section 36 in alternating positions. It can also be seen that in the presently preferred embodiment, the section 36 includes four groups 56 and four groups 58. However, it is to be noted that the passageways may be arranged in a variety of equally acceptable arrangements, depending upon the design and operational characteristics desired. The sizes of the passageways 52 and 50 may be varied to' facilitate increased velocity, particularly through passageways 52. Increased velocity through passageways 52 relative to the velocity through passageways 50 provides (increased diffusion of recirculated flue gas. In one preferred embodiment of the invention, shown particularly in Figs. 11 and 12, a central secondary staged fuel nozzle 60 protrudes through a hole 64 provided in end cap 38. Nozzle 60 includes a length of gas supply tubing 86 that extends along axis 54 and through portion 34. A staged burner tip 62 is mounted at the downstream end 88 of thejtubing 86. Tip 62 may be as is illustrated in Figs. 8A and 8B, where it can be seen that'the same may be provided with delivery openings 66 for directing the flow of preferably raw fuel into zone 20 in spaced relationship relative to a radiant combustion area 75 in zone 20 adjacent face 74 (see Fig. 1). As shown in Figs. 8 A and 8B, openings 66 may be disposed at an approximate angle of 45° from the plane of the the face; however the angle required for any given installation may vary depending upon the desired operational and performance characteristics of the burner. In this latter regard, the angle of openings 66 should desirably not be less than about 30°, as shown schematically in Fig. 11, to insure that premature mixing of the staged fuel with an oxygen rich mixture is avoided. Likewise, the number and spacing of the openings 66 is a function of the desired performance characteristics. In another embodiment of the invention, nozzle 60 may be as shown in Figs. 12,13 and 14, where the downstream portion .90 of tubing 86 protrudes beyond end cap 38 such that the tip 62 is positioned in spaced relationship relative to end cap 38. In this case, the assembly 16 may preferably include a cylindrical sheath 92 which is mounted on end cap 38 and extends along the entire length of protruding portion 90 in surrounding relationship to the latter. Appropriately positioned openings 94 nay be provided in sheath 92 to permit the entirety of tip 62 to be protected from the heat of the combustion zone and yet allow egress of staged fuel from tip 62. As shown in Fig. 12, the sheath 92 may also have an open end 96 which is adapted to vent the sheath 92 by permitting gases between the sheath 92 and the tubing 86 to escape into the combustion zone. Alternatively, the arrangement may be as shown in Figs. 13/and 14, where the end of the sheath 92 is closed by a flat (Fig. 13) or domed (Fig. 14) cap 98. In this case, appropriate vent holes 97 may be provided in the wall of the sheath 92. These vent holes 98 serve essentially the same purpose as the or en end 96, but as shown, the same may preferably be disposed at a downwardly incline 1 angle of about 10° relative to a plane which is perpendicular to the longitudinal axis of the sheath 92. Desirably, nozzle 60 may also be provided with an orifice 68 as shown in Fig. 5 to control the amount of fuel which flows into the combustion zone via nozzle 60. In accordance with the concepts and principles of the invention, the tip 62 desirably may be positioned far enough away from the premixed discharge nozzle 18 such that the flow patterns of the oxygen rich and radially moving combusting gases in the radiant combustion area 75 and the staged fuel injected via nozzle 60 are mechanically decoupled so as to avoid burning of the staged fuel in an oxygen rich environment. Thus, the staged gas jet leaving tip 62 is far enough from the premixed flow envelope such that the momentum of the jet is insufficient to cause the staged gas and the premixed gas/air mixture to intermingle, at least until the fuel from nozzle 60 has had an opportunity to become mixed with flue gas. This is extremely important, particularly when considered in conjunction with the ultralean concept of the primary air/fuel mixture where the large amount of excess air left over from the combustion in the radiant heating area 75 is significant enough to cause localized combustion to stare at the tip of the staged riser, thus increasing NOx emissions. Desirably, for best results in NOx abatement; the staged fuel should be combusted in an atmosphere which contains no more than about 4% oxygen by volume. With reference to Figs. 9 and 10, for some important applications utilizing the concepts and principles of the invention, the opening 14 may desirably be larger in internal diameter than the outer diameter of tube portion 34 so that secondary combustion air may flow into zone 20 through the annular space between opening 14 and cylindrical section 34. In accordance with the invention this aspect of the invention, fr.nd as illustrated in Figs. 9 and 10, secondary air ducts 70 may be provided to facilitate and improve the flow of secondary air. One end 72 of duct 70 is in communication with zone 20 at the face 74 of tile 12. The other end 16 of duct 70 is in communication with opening 14. As can be seen from Fig. 10, end 72 is arcuate in shape so that the same projects a fan-shaped flow of air into zone 20. End 76 is also arcuate in shape and in general is in the shape of a slot which extends around the internal surface 78 of opening 14. In accordance with the invention, the face 74 of tile 12 may be dished or flat: Dishing may facilitate recirculation of flue gas inside the dish. In the operation of a burner which incorporates the tile illustrated ir.. Figs. 9 and 10, the fuel lean fuel/air mixture leaving passageways 50 and 52 travels radially, outwardly of axis 54 and generally across face 74 of tile 12 where it is burned in a ridianc combustion area 75 adjacent face 74. The combustion products of the fuel/air mixture eventually intermix with raw fuel from nozzle 60. In many embodiments of the invention, 'the intermixture may be fuel rich, and after combustion, the same may provide a generally laterally extending flame having an outer peripheral extremity at the radial periphery of area 75, which periphery is spaced radially from the axis. Preferabl y, end 72 of duct 70 may be positioned so as to provide a fan a air to the flame at the outer peripheral extremity of the laterally extending flame. An embodiment of the nozzle of the invention which includes an irtenal baffle 84 is shown in FIG. 6. Baffle 84 is generally in the shape of an inverted cone and the same is positioned for redirecting the flow of the air/fuel mixture traversing tube 40. The combustible mixture travels along tube 40 in a generally axial direction until it encounters baffle 84 which redirects the flow so that it moves in a generally radial direction. In FIG.6 the baffle is shown in combination with a nozzle structure which includes a centrally located raw fuel nozzle 60. However, it will be recognized by one of ordinary skill that the internal baffle will be highly useful regardless of the presence or, absence of the central nozzle. EXAMPLE A burner embodying the concepts and principles of the invention was operated as follows : the burner is fixed at 185 kw (0.63 MMBtuh) excess air is 10%; furnace temperaturei is 1000 °C (1800 °F); burner differential pressure is 0.6 mbar (0.25 inches of water); secondary and primary burner damper is fully opened; combustible gas is 50% natural gas and 50% hydrogen; burner is aligned with outer cupped tile edge and then pushed in 6.4mm (0.25 inch). Measured results using a shgle burner: 2.5%O2; Oppm CO; and 8 to 10 ppm NOx. Measured results using an array of 13 burners : 2.5% O2; 0 ppm CO; and 15 to 19 ppm NOx. As a result of the experiment it was noted that with deeper staging of air through the tile, NOx emissions can be brought down by a significant percentage of the overall emissions. The advantages provided by the invention described above include very low NOx, low noise, partial premix with a rich gas stream axially staged for low NOx, prompt NOx alleviation with fuel induced furnace gas recirculation, simplicity, short flame profile, high pressure utilization at turndown for jet stability, high stability, operalion with either flat or cupped tile face, facilitation of the manipulation of L/D for defined combustion of premixed fuel and air, staged air tile further decreases NOx formations with staged air technology, staged gas is directed away from furnace wall for slowed combustion, and secondary air staging is integral part of tile such that no excess air is needed at the base of the premix tip. The burner of the invention is of a premix design. The burner may also include a venturi that is preferably optimized sufficiently to deliver an extremely fuel lean premix of air and fuel to the main discharge nozzle of the burner. The discharge nozzle may be designed so that its slots have a significant L/D (width to depth ration) to keep each individual premixed jet as a defined individual flame envelope. This allows for the natural recirculation patterns of the tile and furnace to inject furnace flue gas into each stream. This is one factor in the reduction of NOx. The discharge nozzle may be arranged in eight sections, four (4) that are high flow and four (4) that are of lower flow. Since the webbing between each section is proportional the recirculation of flue gasse in the tighter restricted area is more pronounced.' The variation of area assures stability in the larger flow areas while the smaller ratesiare subjected to a higher percentage of flue gas by diffusion due to the smaller mass. As described above, a center riser 60 may be inserted through the burner tube 34, which preferably may be a venturi, so that the riser protrudes through the end plate 38 of the discharge nozzle 36. The secondary or staged nozzle 60 is fed pure gas fuel (unpremixed) at a pressure of about 0.7 bar (10 psig). The gas is then expolled via a staged tip 62 designed to handle the high temperatures of the furnace and subsequently burned. This tip 62 desirably provides a L/D sufficient to ensure that the gas can be directed at an angle as required to oxidize the gas in a stable manner away from the,! heat of the furnace wall. This ensures that the combustion process is impeded, but not enough to induce appreciable amounts of CO. The tip pressure is maintained by an integral orifice 68 located in the line from the main gas spud to the staged tip. The discharge nozzle 36 and the staged tip 62 interact together in flow patterns created by the open slots in the face of the discharge nozzle 36 to insure appropriate staging of the raw fuel and the subsequent recirculation of the CO and CO2 formed to lower the NOx further in the primary premixed section of the flame. Another aspect of the burner of the invention is its capability to utilize a truly staged air tile formation, whereby secondary air is mixed into the premixed portion of the flame at its peripheral tip. The NOx can be further impeded by the mixing mechanics of this secondary air tile as it stages the air out instead of allowing the secondary air to come into contact with the base of the premixed flame envelope. In another preferred embodiment of the present invention, and as illustrated in Figs. 15, 16 and [17, the burner may be provided with one or more, preferably several, and ideally eight or more radially extending ports 100 in the wall of the centrally disposed tube 34 whjch provides a conduit for delivering the central air / fuel mixture to the burner tip. These ports 100 communicate with the space 102 surrounding the tube 34 whereby a portion of the air / fuel mixture flows through the ports 100 and becomes admixed with secondary air flowing along the outside of the tube 34 toward the combustion zone 20. The admixture thus formed may generally be too lean to support a conventional flame; however, low temperature oxidation thereof occurs at face 174 of the burner tile 104, whereby NOx emissions are minimized. In accordance with a particularly preferred form of the invention described Above, where the ports 100 are used in connection with a radiant burner having a cupped tile 104, the ports 100 provide for a prestaging of some of the premixed air and fuel resulting in decreased tip velocity through discharge nozzle 36, enhanced stability and minimization of NOx emissions. The cupped tile 104 enables the placement of the ports 100 at a location about 76mm (3 full inches) upstream from the discharge nozzle 36 whereby, as shown in Fig. 17, the already lean air / fuel mixture 152 escaping from the central tube 34 through the ports 100 is able to become thoroughly admixed with secondary air flowing in the direction of the arrows. 154 along the outside of tube 34 to present an ultra lean admixture well before the latter reaches the face 174 of the tile. This ultra lean admixture undergoes low temperature oxidation without conventional flame on the face of the tile. The products of this low temperature oxidation are then entrained into the main flame 150 created at the discharge nozzle 36 and provide a quenching, cooling effect to thereby reduce NOx in the main flame. The overall effect provides in a reduction of NOx emissions to a level well below 10 parts per million on a volumetric basis (ppmv). In Accordance with the principles and concepts of the present invention, NOx emissions below 5 ppmv can be achieved consistently. The attributes of this form of the invention include (1) low NOx emissions with staged fuel; (2) flameless combustion coupled with rapid oxidation in the proximity of the tile; (3) low noise as a function of tip pressure and heat release; (4) staged gas jets entraining flue gas external to the burner; (5) prompt NOx alleviation; (6) secondary air has less effect on NOx emissions; (7) short flame profile; (8) high turndown ratios with added premix tip velocities; (9) high stability; (10) minimization of CO emiss»ons; (11) very lean premixed zone; (12) oxidation against radiant tile with stoichionietry below LEL's (cold combustion); and (13) three separate fluid flow zones containing different stoichiometrics of gas and air. As shown in Fig. 16, the holes 100 for directing a portion of the primary air / fuel mixture into the flow of secondary air on the outside of the burner tube 34 to thus create an ultra lean mixture of air and fuel, desirably may be used in conjunction with a burner nozzle which includes flow directors such as the directors 46,48, a central no; :zle such as the nozzle 60, and an internal baffle such as the baffle 84. Broadly, in accordance with the concepts and principles of the configuration illustrated in Figs. 15, 16 and 17, by prestaging a volume of an ultra iean premixed air and fuel gas in conjunction with a premixed burner and a fuel rich staged tip, ultra low NOx emissions may be achieved in conjunction with a tile designed to facilitate flameless combustion of the prestaged ultra lean admixture while maintaining separation of the latter from the main flame until a appropriate product mix is achieved to dilute and cool the main flame so as to lower emissions therein. In the burner of Figs. 15, 16 and 17, once some fraction of the fuel, ranging from about 15% of the fuel to all of the fuel, is mixed with air, a small po.tion of the mixture is removed prior to the main discharge nozzle and redirected into a secondary air stream. In the case of a radiant wall burner, the premix is removed from the central tube 34, which may be in the form of a venturi, by means of ports (radially drilled holes) 100 positioned around the body of the burner prior to the tip. In another configuration the premix may be mixed with recirculated flue gas that is ported back through the tile using special ports. This creates a mixture that is below the flammability limits and incapable of sustaining combustion. This stream must pass then pass through the highly radiant tile section that is capable of accelerating the kinetics of the gas and causing a rapid oxidation of the fuel even though it is below its flammability limits. When substantial oxidation, if not complete oxidation, has taken place this stream is then remixed with the main premixed air and gas stream that is exiting the main burner tip and is just within its flammability limits. The main premix stream sustains and stabilizes the combustion. The oxidized stream has a quenching effect on the main flame, lowering its theoretical temperature by putting a heat load on the flame by means of extra mass. In addition, a secondary staging of pure fuel gas is also being introduced from a secondary tip 60 downstream of the main burner premix discharge nozzlu. The secondary fuel is introduced further into the furnace and uses the kinetic energy of its sonic jets to entrain and mix in substantial amounts of furnace flue gas before it is pulled back into the main flame by the momentum of the main flame and the force of recirculating furnace gases. This also has a quenching effect to the main flame and also serves to bring the flammability limits of the overall mixture into a range that is once again flammable. The stabilizing affect of the refractory helps to maintain a stable flame envelope during turndown and low oxygen regimes seen during operational excursions within the furnace. It is important to note that the premix prestaging_ technique described in connection with Figs. 15, 16 and 17 provides NOx reductions to approximately hdf of what was already an ultra-low NOx burner. It should be noted in this regard that the premix prestage concept facilitated by the holes 100 can be extended for use with essentially any burner shape and/or mounting pattern.' In other words, the premix prestaging technique can be extended to essentially any burner application. Thus; this concept may be used to make very low NOx round flame, upfired or sidefired burners, as well as rectangular flat flame burners and downfired burners.' The concept may also be utilized in both, what are fundamentally diffusion flame burners as well as full fledged premixed type burners. The use of a lean primary air/fuel mixture augmented by a flameless combustion zone within the tile located in proximity to the main flame, plus a substantial staged portion of the gas in fuel rich form that is subsequently returned to the main flame by entrainment and momentum via a nozzle such as the nozzle 60 to provide reduction of theoretical temperature by additional mass, is a very important feature of the invention. i, Overall, the invention is adaptable so as to provide several families of burners ranging from radiant wall burners to horizontal, upfired, and even downfired ' . burner designs with the capability of delivering NOx emissions much below current, burner technologies. In another configuration, in accordance with the concepts and principles of the invention, the ported nozzle arrangement may be used in conjunction with a specially ported version of a tile that is adapted to recirculate flue.gas which may then be used instead of secondary air to dilute the ported" primary air/fuel mixture. Such an arrangement also may be used to provide and maintain a lean premix behind the tile assuring that combustion which would be detrimental to the burner tip does not take place. The spin off to this is the loading of the flame that helps to lower the theoretical temperature of the flame much more than is typically seen in burner designs. The flaraeless combustion zone may be controlled and kept separate from the main flime until most of the initial oxidation is complete. The concepts and principles of the present invention add a new twist to an already evolving technology. Tne creation of a flameless combustion zone (lean premixed) coupled with specific hie designs to control and stabilize the combustion process operate together to provide low NO, without the use of flue gas recirculation and/or other dilution methods for reducing flame temperature. The burner of Figs. 15, 16 and 17 provides single digit NOx numbers in what may be considered "within the parts that are usually included in a conventional burner". By adding the flameless combustion zone behind the main flame, new ground has been broken in addressing what is considered the "prompt NOx regime" of NO, production. The joining of all of these various aspects of the invention allows the burner of the invention to deliver NO. emissions.in the range of single digits to the mid teens (ppm) depending on the number of burners in the array, and the specie;; and concentrations of the species in the fueimix. Thus, in accordance with the invention, it has been discovered that it is possible to combine many known meories of NO, abatement into a single bumer that provides stable operation and appropriate turndown while performing in a range that has not previously been thought possible. In accordance with the invention, shorter flame patterns are possible especially when the fuel comprises heavy hydrocarbons; larger turn down ratios are possible on high hydrogen fuels, particularly when an internal baffle is utilized; much lower noise is experienced around a burner with multiple ports and small jets; either cupped or flat tiles may be utilized interchangeably; staged air tile design allows for NO, adjustment while running; bumer adjustment capabilities in the tile allow for NO, adjustment; tips are easily removed and serviced by design; and the direction of the staged jets at turndown help to stabilize the primary flame. E CLAIM 1. A method for burning fuel in a combustion zone comprising ; providing a fuel lean mixture of fuel and air; delivering said mixture to a centrally located point adjacent a face of a burner tile, said point being disposed adjacent said combustion zone; causing said mixture to flow radially outwardly from said p.oint in a. plurality of streams across the face of said tile; combusting the fuel in said mixture in an area of said combustion zone adjacent said face; and providing staged fuel to said zone at a location spaced from said area; and combusting said staged fuel' in an environment containing flue gases and not more than about 4% oxygen by volume. 2. A method for burning fuel as claimed in claim 1, wherein said mixture includes all of the oxygen necessary for burning all of the fuel in the mixture plus all of the staged fuel. ... 3. A method for burning fuel as claimed in claim 1, wherein said staged fuel is provided to said zone as pure fuel. 4. A method for burning fuel as claimed in claim 2, wherein said staged fuel is provided to said zone as pure fuel. 5. A method for burning fuel as claimed in claim 1, wherein said staged fuel is combusted flamelessly in said environment. 6. A method for burning fuel as claimed in claim 1 or 5, wherein the fuel in said mixture is combusted flamelessly in said area. 7. A method for operating a burner comprising : causing a mixture of fuel and air to flow toward to centrally located point adjacent a face to a burner tile; causing a stream of at least one of additional air and recirculated flue gas to flow toward a location adjacent said face which is spaced laterally from said point; and separating a portion of said mixture and intermixing the same with said stream to thereby create an fuel lean admixture capable of flameless oxidation before the same reaches said location. 8. A method for operating a burner as claimed in claim 7, said method comprising separating a second portion of said mixture into a plurality of separate streams, causing said streams to flow radially outwardly from said point across the face of said tile and causing said streams to combust to form a flame which surrounds said point, and flamelessly oxidizing said admixture at said face to create relatively cool oxidation products. 9. A method as claimed in claim 8, comprising admixing said oxidation products with said flame to thereby dilute and cool the same. 10. A method as claimed in claim 7, wherein said stream comprises additional air. 11. A method as claimed in claim 7, wherein said stream comprises recirculated flue gas. 12. A method as claimed in claim 7, wherein said stream comprises recirculated flue gas and additional air. Dated this 29th day of October, 2004. FOR JOHN ZINK COMPANY L.L.C. By their Agent (MANISH SAURASTRI) KRISHNA & SAURASTRI

Full Text

ORIGINAL
612/MUMNP/2004

I
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
COMPLETE SPECIFICATION
[See section 10; Rule 13]

A METHOD FOR BURNING FUEL IN A COMBUSTION ZONE AND OPERATING OF A BURNER FOR THE SAME
JOHN ZINK COMPANY L.L.C., A CORPORATION ORGANIZED AND EXISTING UNDER THE LAWS OF SWITZERLAND WHOSE ADDRESS IS 11920, EAST APACHIE, TULSA OK 74116, U.S.A.

GRANTED
28/12/2004

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE NATURE OF THIS INVENTION AND THE MANNER IN, WHICH IT IS TO BE PERFORMED.

BACKGROUND OF THE INVENTION
Field of the Invention .
The present invention relates to the field of radiant wall burners. In
particular the invention relates to radiant wall burners wherein a number of
technologies are combined in a single burner arrangement so as to achieve low
i NOx and low noise.
The State of the Prior Art
Reduction and/or abatement of NOx in radiant burners has always
been a desirable aim. Some NO, abatement has been achieved in the past by
staging a portion of the gaseous fuel. Low pressure staged gas may be introduced
into the combustion zone either from low pressure gas tips arranged around the
periphery of the burner or from a center gas tip which protrudes through the center
of the end cap! of the radiant burner nozzle. These arrangements have not always
been successful because, for NO, abatement purposes, the stage fuel should not be
introduced into areas of the combustion zone where the oxygen concentration is
greater than about 4% by volume.
Prior art proposals for gas fuel burners include those described in
US-A-5271729, US-A-4257762 and US-A-3684424. The burner of US-A-
3684424 includes a burner tube delivers a mixture of air and gas to radially facing

openings through which the gas-air mixture is directed across a radially ridged tile
face. US-A-4257762 discloses a generally similar arrangement but with the
openings being inclined to direct the gas-air mixture rearwardly towards the tile
face from the forward end of the burner tube. The burner of US-A-5271729
includes a burner tube with openings at the forward end to direct the gas and air
mixture radially outwardly at the centre of a cup-shaped tile face, and a second
stage nozzle to which a gas and air mixture is supplied through an axial second
stage premix tube, projects beyond the end of the burner tube and has ports

arranged to direct the gas and air mixture radially and adjacent the front face of the
tile.
SUMMARY; OF THE INVENTION
Various problems encountered in prior art burners are addressed by
the concepts land principles of the present invention. In particular, the invention
addresses the ever present need for NO, abatement. In accordance with one aspect
of the invention, it has been found that when gas is buned in a staged manner it
may sometimes be responsible only for about 6 ppm (vol) of the total NO,
emissions of an individual burner. Accordingly it has been thought to be desirable
to adapt the concept of fuel staging to radiant wall burners. Several different
configurations have been tried, some more successful than others, but none with
complete satisfaction. In some configurations, staged fuel has been delivered
through a plurality of tubes at very low pressure around the circumference of the
burner. In such a case the staged fuel is introduced in proximity to a combusting
mixture which is still quite rich in oxygen. This excess oxygen leads to higher
flame temperatures and higher NOx content in flue gases.
In other configurations, staged gas has been introduced into the
combustion zone from the axially distal end of the premix discharge nozzle. This
configuration, where the staged fuel is injected coaxially at the center line of the
premix burner assembly, has been somewhat more successful in achieving lower
NO, emissions that the first configuration discussed above, at least in part due to
the fact that the introduction point is located in spaced relationship to the face of
the tile as well as away from the oxygen rich stream leaving the premix discharge
nozzle. The down side of this particular methodology is that the momentum of the
staged gas jet can and often does pull the primary oxygen rich premixed stream
into the jet 'as an entrained flow thereby increasing the availability of excess
oxygen as well as the production of NO,. This problem is exacerbated in
applications requiring a multiplicity of individual burners in an array because of
the interactions between burners.
In accordance with an important aspect of the invention, a low NO,
burner nozzle assembly is provided for a radiant wall burner. The assembly

includes an elongated hollow burner tube, a discharge nozzle and n central. staged fuel nozzle. The burner tube has a central, longitudinally exuding axis and defines a conduit extending along the axis for supplying a mixture of fuel and air to a radiant combustion area of a combustion zone that extends radially and surrounds the nozzle assembly. This mixture may desirably be fuel lean. The
discharge nozzle is mounted on the tube at a downstream end of the conduit
i adjacent the combustion zone, and the same is adapted for receiving the mixture of
fuel and air; from the conduit and directing the same into the radiant combustion
area in an essentially radial direction relative to the axis of the tube. The discharge
nozzle includes an end cap that is to prevent flow of the mixture in a direction
along the axis. Thus, the mixture is caused to flow through the passageways in a
generally radial direction. The staged fuel burner nozzle includes a length of
tubing which extends along the axis of the conduit, and a staged burner nozzle tip
at a downstream end of the length of tubing. The staged fuel burner nozzle is
arranged so, as to protrude axially through a hole in the end cap. The tip has a fuel
delivery orifice therein for delivering fuel to the combustion zone in spaced
relationship; to the radiant combustion area of the zone.
According to one construction in accordance with the invention, the
delivery orifice is disposed so as to introduce fuel gas into the combustion zone at
an upward and outward angle relative to a plane that is perpendicular to the axis.
Preferably the angle may be at least about 30°. In another construction in
accordance with the invention, the delivery orifice is disposed to introduce fuel
gas in a direction along the axis.
The discharge nozzle may include a plurality of flow directing
members arranged in an array which extends circumferentially around the
discharge nozzle and the members may desirably be arranged to define
therebetween a plurality of passageways which extend in a generally radial
direction relative to the axis.

Preferably, the flow directing members may be arranged so that some of the passageways therebetween have a larger flow area than others. Desirably, the members may be in the form of plates which are essentially

rectangular in shape. Ideally, the passageways may also extend ,„ an ax.al direction. In a much preferred form of the invention, the end cap may have a lateral edge which is located at a first radial distance from the axis, and the members may each have an outer edge located at a second radial distance fix,™ the axis The secoiid radial distance ideally may be greater than the first radial distance such that passageways defined by the members extend radially outward
beyond the lateral edge of the end cap.
accordance with another preferred form of the invention, the nozzle may inclide an internal baffle positioned and arranged to redirect at least a portion of the mixture flowing through the conduit and cause the same to flow through the passageways in a generally radial direction.
The staged fuel burner nozzle may be positioned such that a downstream portion of the length of tubing protrudes beyond the end cap so that the tip is positioned in axially spaced relationship relative to the end cap. Ideally, in this particularly desirable form of the invention, the low NO, burner nozzle may include an elongated protective sheath disposed in surrounding relationship to the protruding portion of the length of tubing and the tip. Such sheath may desirably include an openihg disposed in alignment with the orifice. The sheath may also be provided with one or more vent openings configured to permit gases between the sheath and the length of tubing to escape into the combustion zone. In accordance ' with the foregoing aspects of the invention, the staged burner nozzle may be of significant value, regardless of the form of the discharge nozzle. Thus, the staged burner tip of the invention may be used with any sort of radial discharge nozzle that operates to spread a combustible mixture of fuel and air radially across the
face of a radiant tile.
In an embodiment the burner tube has an outer wall surrounding
said conduit, ah inlet for a mixture of fuel and air is located at the end of the burner tube opposite the discharge nozzle, an air passageway is located outside the wall of the burner tube, and at least one port extends through said outer wall at a location between the discharge nozzle and said inlet intercommunicating the conduit and thejair passage.

The burner tube may comprise a venturi tube having a throat that is in communication with an air supply and a source of fuel gas under pressure. The venturi tube may desirably be arranged such that the flow of fuel gas through the throat induces flow of air from the air source whereby the mixture of fuel and air is created in the throat and caused to flow toward the discharge nozzle.
The invention also provides a low NO, radiant wall burner comprising a buner tile having a central opening surrounded by a radiant tile face and an elongated low NOx burner nozzle assembly as described above that extends through such opening. The face of the burner tile may be either dished or flat.
In addition, the nozzle assembly and/or burner of the invention can
be used for performing a method for burning fuel in a combustion zone
comprising providing a fuel lean mixture of fuel and air, delivering said mixture to
a centrally located point adjacent a face of a burner tile, said point being disposed
adjacent said;combustion zone, causing said mixture to flow radially outwardly
from the centrally located point in a plurality of streams across the face of the tile,
combusting the fuel in said mixture in an area of the combustion zone adjacent the
face of the tile, providing a staged fuel to said zone at a location spaced from said
area, and combusting said staged fuel in an environment containing flue gases and
not more thaniabout 4% oxygen by volume.
In a preferred low NO, burner nozzle assembly which includes at
least one port extending through the outer wall of the burner tube at a location
between the discharge nozzle and the inlet to communicate the conduit with an air
passageway located outside the burner tube, the port has a center axis which is
essentially perpendicular to the central axis of the tube. Alternatively, the port
may have a center axis which is at an angle relative to the central axis of the tube.
Ideally the assembly may include a plurality of ports extending through the wall of
the tube at respective locations between the discharge nozzle and the inlet. In one
preferred form of the invention, the ports may be arranged in one or more rows
which extend around the outer wall of the tube.
The nozzle assembly having at least one port extending through the wall of the burner tube may be used as a component of a low NO, radiant wall

buner that includcs a burner tile having a centra, opening , In such a case, nozzle assembly may extend through the central opening of ,e tile. Desirably, the discharge nozzle may-include a plurahty of now direchng members such are arrged to define therebetween a plurality of passageways which extend in generally radial directions relative to the axis of the buner tube, and an end cap
flowing from; the end of the conduit and cause the same to How through said passage ays in a generally radial direction so that when ignited, the redirected ture of fuel and air provides a generally laterally extending flame having an outer peripheral extremity at a location in said zone spaced radially from said axis
Also described herein is a method for operating a burner which
includes the steps of causing a mixture of fuel and air to flow toward a centrally ,ocated point! adjacent a face of a burner tile, causing a stream of at least one of additional air and recirculated flue gas to flow toward a location.djacent said face which is spaced laterally from said point, and separating a portion of sa.d mixture and intermixing the same with said stream to thereby create an ultra lean admixture capable of flameless oxidation before the same reaches said location. More particularly, the method may include the steps of causing a mixture of fuel and air to flow toward a centrally located point adjacent a face of a burner t,lc. separating a first portion of said mixture into a plurality of separate streams and causing said streams to flow radially outwardly from said point across the face of said tile, causing said streams to combust to form flames, each having an outer peripheral iirminus spaced radially from said point, providing secondary an to said flame at a location adjacent said termini, adding a second portion of said mixture to slid secondary air at a location upstream from said location to create an admixture capable of flameless oxidation at the face of said tile, and flameless.y oxidizing said admixture at said face to create relatively cool oxidation products. Oxidation products may be admixed with the combusting gases to thereby dilute and cool the same, and a flow of recirculated flue gas may be provided to said flame at a location adjacent said termini.

Prior art burners of the premix type of design have not been able to utilize as many NOx abatement technologies in a single burner as are provided in the burner arrangements, of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevational view, partly in cross-section, of a low NOx radiant wall burner which; embodies the concepts and principles of the invention;
FIG. 2 is a side elevational view of the nozzle arrangement of the burner of FIG. 1;
FIG. 3 is a schematic plan view of a preferred embodiment of the discharge nozzle of the nozzle arrangement of FIG. 2.
FIG. 4 is an enlarged elevational, cross-sectional view of the discharge noz/.le of FIG.3;
FIG. 5 is ah enlarged view, partly in cross-section, of the discharge nozzle of F IG.3;
FIG. 6 is an enlarged view, similar to FIG. 5, which is partly in cross section to illustrate anjembodiment of an internal baffle;
FIG. 7 is a schematic view of the nozzle arrangement of FIG. 1;
FIGS. 8A and 8B respectively are side elevational and plan views an embodiment of a central staged nozzle tip for the nozzle arrangement of FIG. 2;
FIG. 9 is a side elevational view of an embodiment of a tile for use with the burner of FIG.1;

FIG. 10 is a plan view of the tile of FIG. 9;
FIG. 11 is, a schematic side elevational view of one embodiment of a nozzle, arrangement that is useful in connection with the invention.
FIG. 12 is a schematic side elevational view of an alternative embodiment of a nozzle arrangement that is useful in connection with the invention;
FIG. 13 is a schematic side elevational view of another alternative embodiment of a nozzle arrangement that is useful in connection with the invention;
FIG. 14 is a schematic side elevational view of yet another alternative embodiment of a nozzle arrangement that is useful in connection with the invention;
FIG. 15 is a side elevational view of yet another burner arrangement which embodies the concepts and principles of the invention;
FIG. 16 is an enlarged cross sectional view of the discharge nozzle of the burner of FIG. 15; and
FIG. 17 is a schematic view illustrating the operation of the burner of FIG. 15,
including a schematic showing of the flow paths of the several combustion and flameless oxidation streams.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
A burner 10 which embodies the concepts and principles of the invention
is illustrated in Fig. 1 where it can be seen that the same includes a burner tile 12 having
a centrally disposed opening 14 and a burner nozzle assembly 16 including a burner
discharge nozzle 18 which protrudes through opening 14 and extends into a combustion
zone 20. The burner 10 may also include conventional components such as a muffler 22,
an air door 24 and an inlet tube 26 facilitating connection to a source of fuel gas.
With reference to Fig. 2, it can be seen that the nozzle assembly 16 may
include spud 28 whereby a supply of fuel gas is supplied to the nozzle assembly 16. Spud
28 is connected to a coupling 42 (See Fig. 7) whereby fuel gas is supplied to the
discharge nozzle 18. The assembly 16 also includes an elongated, hollow burner tube 30
and a base 32. Tube 30 extends between base 32 and discharge nozzle 1.8 and provides
a passageway for primary combustion air and accommodates the gas supply system (not
shown) which interconnects spud 28 and coupling 42.
Discharge nozzle 18 preferably includes a fuel distribution section 36 and i an end cap 38. With reference to Figs. 5, 6 and 7, it can be seen that the downstream
portion 34 of tube 30 may preferably include a venturi tube 40 whereby fuel gas being
ejected through an opening 44 in coupling 42 induces a flow of combustion air from the
interior of tube 30. Preferably coupling 42 may be provided with a plurality of openings
44 as shown. The fuel gas ejected through the openings 44 mixes with the induced air
to preferably form a combustible fuel lean fuel gas/air mixture which travels through

portion 34 of tube 30 toward and into fuel distribution section 36.
Fuel distribution section 36 is illustrated in Figs. 3 and 4. Section 36 includes a plurality of fin-like flow directing members 46 and 48 which define therebetween a plurality of passageways 50 and 52 which extend in a generally radial direction relative to the central axis 54 of the nozzle assembly 16. The members 46 and 48 may be sized and arranged such that the passageways 50 defined between adjacent members 46 may be larger in cross-sectional flow area than the passageways 52 denned between adjacent members 48. In operation, the fuel/air mixture flows through portion 34 of tube 30 in a direction which is generally parallel to axis 54. As the air/fuel mixture approaches end cap 38, the air/gas mixture is redirected so that it flows radially oui ward

through the passageways 50 and 52. It is to be noted in this regard that the respective outer extremities 46a and 48a of members 46 and 48 are preferably spaced further from axis 54 than the outer edge 38a of cap 38. This provides respective openings 50a and 52a (see Fig!'5) at the axially outer ends of passageways 50 and 52 which permit a portion of the air/fuel combustible mixture adjacent thereto to bend slightly and flow tow lrd zone 20 rather than in a direction at right angles to axis 54.;
With particular reference to Fig. 3, it can be seen that the membei s 46 and 48 may be arranged so as to provide respective groups 56 and 58 of passageway; 50 and 52. As shown, each group 56 includes five passageways 50 and each group 58 includes five passageways 52. As can clearly be seen from Fig. 3, the passageways 50 are wider than the passageways 52 so that the cross sectional flow areas provided by passageways 50 are greater than the cross-sectional flow areas provided by passageways 52. As shown, the groups 56 and 58 are arranged around section 36 in alternating positions. It can also be seen that in the presently preferred embodiment, the section 36 includes four groups 56 and four groups 58. However, it is to be noted that the passageways may be arranged in a variety of equally acceptable arrangements, depending upon the design and operational characteristics desired. The sizes of the passageways 52 and 50 may be varied to' facilitate increased velocity, particularly through passageways 52. Increased velocity through passageways 52 relative to the velocity through passageways 50 provides (increased diffusion of recirculated flue gas.
In one preferred embodiment of the invention, shown particularly in Figs. 11 and 12, a central secondary staged fuel nozzle 60 protrudes through a hole 64 provided in end cap 38. Nozzle 60 includes a length of gas supply tubing 86 that extends along axis 54 and through portion 34. A staged burner tip 62 is mounted at the downstream end 88 of thejtubing 86. Tip 62 may be as is illustrated in Figs. 8A and 8B, where it can be seen that'the same may be provided with delivery openings 66 for directing the flow of preferably raw fuel into zone 20 in spaced relationship relative to a radiant combustion area 75 in zone 20 adjacent face 74 (see Fig. 1). As shown in Figs. 8 A and 8B, openings 66 may be disposed at an approximate angle of 45° from the plane of the the face; however the angle required for any given installation may vary depending upon the desired operational and performance characteristics of the burner. In this latter regard, the angle of openings 66 should desirably not be less than about 30°, as shown

schematically in Fig. 11, to insure that premature mixing of the staged fuel with an oxygen rich mixture is avoided. Likewise, the number and spacing of the openings 66 is a function of the desired performance characteristics.
In another embodiment of the invention, nozzle 60 may be as shown in Figs. 12,13 and 14, where the downstream portion .90 of tubing 86 protrudes beyond end cap 38 such that the tip 62 is positioned in spaced relationship relative to end cap 38. In this case, the assembly 16 may preferably include a cylindrical sheath 92 which is mounted on end cap 38 and extends along the entire length of protruding portion 90 in surrounding relationship to the latter. Appropriately positioned openings 94 nay be provided in sheath 92 to permit the entirety of tip 62 to be protected from the heat of the combustion zone and yet allow egress of staged fuel from tip 62.
As shown in Fig. 12, the sheath 92 may also have an open end 96 which is adapted to vent the sheath 92 by permitting gases between the sheath 92 and the tubing 86 to escape into the combustion zone. Alternatively, the arrangement may be as shown in Figs. 13/and 14, where the end of the sheath 92 is closed by a flat (Fig. 13) or domed (Fig. 14) cap 98. In this case, appropriate vent holes 97 may be provided in the wall of the sheath 92. These vent holes 98 serve essentially the same purpose as the or en end 96, but as shown, the same may preferably be disposed at a downwardly incline 1 angle of about 10° relative to a plane which is perpendicular to the longitudinal axis of the sheath 92. Desirably, nozzle 60 may also be provided with an orifice 68 as shown in Fig. 5 to control the amount of fuel which flows into the combustion zone via nozzle 60.
In accordance with the concepts and principles of the invention, the tip 62 desirably may be positioned far enough away from the premixed discharge nozzle 18 such that the flow patterns of the oxygen rich and radially moving combusting gases in the radiant combustion area 75 and the staged fuel injected via nozzle 60 are mechanically decoupled so as to avoid burning of the staged fuel in an oxygen rich environment. Thus, the staged gas jet leaving tip 62 is far enough from the premixed flow envelope such that the momentum of the jet is insufficient to cause the staged gas and the premixed gas/air mixture to intermingle, at least until the fuel from nozzle 60 has had an opportunity to become mixed with flue gas. This is extremely important, particularly when considered in conjunction with the ultralean concept of the primary air/fuel mixture where the large amount of excess air left over from the combustion in the

radiant heating area 75 is significant enough to cause localized combustion to stare at the tip of the staged riser, thus increasing NOx emissions. Desirably, for best results in NOx abatement; the staged fuel should be combusted in an atmosphere which contains no more than about 4% oxygen by volume.
With reference to Figs. 9 and 10, for some important applications utilizing the concepts and principles of the invention, the opening 14 may desirably be larger in internal diameter than the outer diameter of tube portion 34 so that secondary combustion air may flow into zone 20 through the annular space between opening 14 and cylindrical section 34. In accordance with the invention this aspect of the invention, fr.nd as illustrated in Figs. 9 and 10, secondary air ducts 70 may be provided to facilitate and improve the flow of secondary air. One end 72 of duct 70 is in communication with zone 20 at the face 74 of tile 12. The other end 16 of duct 70 is in communication with opening 14. As can be seen from Fig. 10, end 72 is arcuate in shape so that the same projects a fan-shaped flow of air into zone 20. End 76 is also arcuate in shape and in general is in the shape of a slot which extends around the internal surface 78 of opening 14. In accordance with the invention, the face 74 of tile 12 may be dished or flat: Dishing may facilitate recirculation of flue gas inside the dish.
In the operation of a burner which incorporates the tile illustrated ir.. Figs. 9 and 10, the fuel lean fuel/air mixture leaving passageways 50 and 52 travels radially, outwardly of axis 54 and generally across face 74 of tile 12 where it is burned in a ridianc combustion area 75 adjacent face 74. The combustion products of the fuel/air mixture
eventually intermix with raw fuel from nozzle 60. In many embodiments of the

invention, 'the intermixture may be fuel rich, and after combustion, the same may provide a generally laterally extending flame having an outer peripheral extremity at the radial periphery of area 75, which periphery is spaced radially from the axis. Preferabl y, end 72 of duct 70 may be positioned so as to provide a fan a air to the flame at the outer peripheral extremity of the laterally extending flame.
An embodiment of the nozzle of the invention which includes an irtenal baffle 84 is shown in FIG. 6. Baffle 84 is generally in the shape of an inverted cone and the same is positioned for redirecting the flow of the air/fuel mixture traversing tube 40. The combustible mixture travels along tube 40 in a generally axial direction until it encounters baffle 84 which redirects the flow so that it moves in a generally radial

direction. In FIG.6 the baffle is shown in combination with a nozzle structure which includes a centrally located raw fuel nozzle 60. However, it will be recognized by one of ordinary skill that the internal baffle will be highly useful regardless of the presence or, absence of the central nozzle.
EXAMPLE
A burner embodying the concepts and principles of the invention was operated as follows : the burner is fixed at 185 kw (0.63 MMBtuh) excess air is 10%; furnace temperaturei is 1000 °C (1800 °F); burner differential pressure is 0.6 mbar (0.25 inches of water); secondary and primary burner damper is fully opened; combustible gas is 50% natural gas and 50% hydrogen; burner is aligned with outer cupped tile edge and then pushed in 6.4mm (0.25 inch). Measured results using a shgle burner: 2.5%O2; Oppm CO; and 8 to 10 ppm NOx. Measured results using an array of 13 burners : 2.5% O2; 0 ppm CO; and 15 to 19 ppm NOx.
As a result of the experiment it was noted that with deeper staging of air through the tile, NOx emissions can be brought down by a significant percentage of the overall emissions.
The advantages provided by the invention described above include very low NOx, low noise, partial premix with a rich gas stream axially staged for low NOx, prompt NOx alleviation with fuel induced furnace gas recirculation, simplicity, short flame profile, high pressure utilization at turndown for jet stability, high stability, operalion with either flat or cupped tile face, facilitation of the manipulation of L/D for defined combustion of premixed fuel and air, staged air tile further decreases NOx formations with staged air technology, staged gas is directed away from furnace wall for slowed combustion, and secondary air staging is integral part of tile such that no excess air is needed at the base of the premix tip.

The burner of the invention is of a premix design. The burner may also include a venturi that is preferably optimized sufficiently to deliver an extremely fuel lean premix of air and fuel to the main discharge nozzle of the burner. The discharge nozzle may be designed so that its slots have a significant L/D (width to depth ration) to keep each individual premixed jet as a defined individual flame envelope. This allows for the natural recirculation patterns of the tile and furnace to inject furnace flue gas into each stream. This is one factor in the reduction of NOx.
The discharge nozzle may be arranged in eight sections, four (4) that are high flow and four (4) that are of lower flow. Since the webbing between each section is proportional the recirculation of flue gasse in the tighter restricted area is more pronounced.' The variation of area assures stability in the larger flow areas while the smaller ratesiare subjected to a higher percentage of flue gas by diffusion due to the smaller mass.
As described above, a center riser 60 may be inserted through the burner tube 34, which preferably may be a venturi, so that the riser protrudes through the end plate 38 of the discharge nozzle 36. The secondary or staged nozzle 60 is fed pure gas fuel (unpremixed) at a pressure of about 0.7 bar (10 psig). The gas is then expolled via a staged tip 62 designed to handle the high temperatures of the furnace and subsequently burned. This tip 62 desirably provides a L/D sufficient to ensure that the gas can be directed at an angle as required to oxidize the gas in a stable manner away from the,! heat of the furnace wall. This ensures that the combustion process is impeded, but not enough to induce appreciable amounts of CO.
The tip pressure is maintained by an integral orifice 68 located in the line from the main gas spud to the staged tip. The discharge nozzle 36 and the staged tip 62

interact together in flow patterns created by the open slots in the face of the discharge nozzle 36 to insure appropriate staging of the raw fuel and the subsequent recirculation of the CO and CO2 formed to lower the NOx further in the primary premixed section of the flame.
Another aspect of the burner of the invention is its capability to utilize a truly staged air tile formation, whereby secondary air is mixed into the premixed portion of the flame at its peripheral tip. The NOx can be further impeded by the mixing mechanics of this secondary air tile as it stages the air out instead of allowing the secondary air to come into contact with the base of the premixed flame envelope.
In another preferred embodiment of the present invention, and as illustrated in Figs. 15, 16 and [17, the burner may be provided with one or more, preferably several, and ideally eight or more radially extending ports 100 in the wall of the centrally disposed tube 34 whjch provides a conduit for delivering the central air / fuel mixture to the burner tip. These ports 100 communicate with the space 102 surrounding the tube 34 whereby a portion of the air / fuel mixture flows through the ports 100 and becomes admixed with secondary air flowing along the outside of the tube 34 toward the combustion zone 20. The admixture thus formed may generally be too lean to support a conventional flame; however, low temperature oxidation thereof occurs at face 174 of the burner tile 104, whereby NOx emissions are minimized.
In accordance with a particularly preferred form of the invention described Above, where the ports 100 are used in connection with a radiant burner having a cupped tile 104, the ports 100 provide for a prestaging of some of the premixed air and fuel resulting in decreased tip velocity through discharge nozzle 36, enhanced stability and minimization of NOx emissions. The cupped tile 104 enables the placement of

the ports 100 at a location about 76mm (3 full inches) upstream from the discharge nozzle 36 whereby, as shown in Fig. 17, the already lean air / fuel mixture 152 escaping from the central tube 34 through the ports 100 is able to become thoroughly admixed with secondary air flowing in the direction of the arrows. 154 along the outside of tube 34 to present an ultra lean admixture well before the latter reaches the face 174 of the tile. This ultra lean admixture undergoes low temperature oxidation without conventional flame on the face of the tile. The products of this low temperature oxidation are then entrained into the main flame 150 created at the discharge nozzle 36 and provide a quenching, cooling effect to thereby reduce NOx in the main flame. The overall effect provides in a reduction of NOx emissions to a level well below 10 parts per million on a volumetric basis (ppmv). In Accordance with the principles and concepts of the present invention, NOx emissions below 5 ppmv can be achieved consistently.
The attributes of this form of the invention include (1) low NOx emissions with staged fuel; (2) flameless combustion coupled with rapid oxidation in the proximity of the tile; (3) low noise as a function of tip pressure and heat release; (4) staged gas jets entraining flue gas external to the burner; (5) prompt NOx alleviation; (6) secondary air has less effect on NOx emissions; (7) short flame profile; (8) high turndown ratios with added premix tip velocities; (9) high stability; (10) minimization of CO emiss»ons; (11) very lean premixed zone; (12) oxidation against radiant tile with stoichionietry below LEL's (cold combustion); and (13) three separate fluid flow zones containing different stoichiometrics of gas and air.
As shown in Fig. 16, the holes 100 for directing a portion of the primary air / fuel mixture into the flow of secondary air on the outside of the burner tube 34 to thus

create an ultra lean mixture of air and fuel, desirably may be used in conjunction with a burner nozzle which includes flow directors such as the directors 46,48, a central no; :zle such as the nozzle 60, and an internal baffle such as the baffle 84.
Broadly, in accordance with the concepts and principles of the configuration illustrated in Figs. 15, 16 and 17, by prestaging a volume of an ultra iean premixed air and fuel gas in conjunction with a premixed burner and a fuel rich staged tip, ultra low NOx emissions may be achieved in conjunction with a tile designed to facilitate flameless combustion of the prestaged ultra lean admixture while maintaining separation of the latter from the main flame until a appropriate product mix is achieved to dilute and cool the main flame so as to lower emissions therein.
In the burner of Figs. 15, 16 and 17, once some fraction of the fuel, ranging from about 15% of the fuel to all of the fuel, is mixed with air, a small po.tion of the mixture is removed prior to the main discharge nozzle and redirected into a secondary air stream. In the case of a radiant wall burner, the premix is removed from the central tube 34, which may be in the form of a venturi, by means of ports (radially drilled holes) 100 positioned around the body of the burner prior to the tip. In another configuration the premix may be mixed with recirculated flue gas that is ported back through the tile using special ports. This creates a mixture that is below the flammability limits and incapable of sustaining combustion. This stream must pass then pass through the highly radiant tile section that is capable of accelerating the kinetics of the gas and causing a rapid oxidation of the fuel even though it is below its flammability limits. When substantial oxidation, if not complete oxidation, has taken place this stream is then remixed with the main premixed air and gas stream that is exiting the main burner tip and is just within its flammability limits. The main premix stream sustains and stabilizes the combustion. The oxidized stream has a quenching effect on the main flame, lowering its theoretical temperature by putting a heat load on the flame by means of extra mass.
In addition, a secondary staging of pure fuel gas is also being introduced from a secondary tip 60 downstream of the main burner premix discharge nozzlu. The secondary fuel is introduced further into the furnace and uses the kinetic energy of its sonic jets to entrain and mix in substantial amounts of furnace flue gas before it is pulled back into the main flame by the momentum of the main flame and the force of recirculating furnace gases. This also has a quenching effect to the main flame and also

serves to bring the flammability limits of the overall mixture into a range that is once again flammable. The stabilizing affect of the refractory helps to maintain a stable flame envelope during turndown and low oxygen regimes seen during operational excursions within the furnace.
It is important to note that the premix prestaging_ technique described in connection with Figs. 15, 16 and 17 provides NOx reductions to approximately hdf of what was already an ultra-low NOx burner. It should be noted in this regard that the premix prestage concept facilitated by the holes 100 can be extended for use with essentially any burner shape and/or mounting pattern.' In other words, the premix prestaging technique can be extended to essentially any burner application. Thus; this
concept may be used to make very low NOx round flame, upfired or sidefired burners, as

well as rectangular flat flame burners and downfired burners.' The concept may also be utilized in both, what are fundamentally diffusion flame burners as well as full fledged premixed type burners.
The use of a lean primary air/fuel mixture augmented by a flameless combustion zone within the tile located in proximity to the main flame, plus a substantial staged portion of the gas in fuel rich form that is subsequently returned to the main flame by entrainment and momentum via a nozzle such as the nozzle 60 to provide reduction of theoretical temperature by additional mass, is a very important feature of the invention. i, Overall, the invention is adaptable so as to provide several families of
burners ranging from radiant wall burners to horizontal, upfired, and even downfired
' .
burner designs with the capability of delivering NOx emissions much below current, burner technologies.
In another configuration, in accordance with the concepts and principles of the invention, the ported nozzle arrangement may be used in conjunction with a specially ported version of a tile that is adapted to recirculate flue.gas which may then be used instead of secondary air to dilute the ported" primary air/fuel mixture. Such an arrangement also may be used to provide and maintain a lean premix behind the tile assuring that combustion which would be detrimental to the burner tip does not take place. The spin off to this is the loading of the flame that helps to lower the theoretical temperature of the flame much more than is typically seen in burner designs. The

flaraeless combustion zone may be controlled and kept separate from the main flime until most of the initial oxidation is complete.
The concepts and principles of the present invention add a new twist to an already evolving technology. Tne creation of a flameless combustion zone (lean premixed) coupled with specific hie designs to control and stabilize the combustion process operate together to provide low NO, without the use of flue gas recirculation and/or other dilution methods for reducing flame temperature.
The burner of Figs. 15, 16 and 17 provides single digit NOx numbers in what may be considered "within the parts that are usually included in a conventional burner". By adding the flameless combustion zone behind the main flame, new ground has been broken in addressing what is considered the "prompt NOx regime" of NO, production.
The joining of all of these various aspects of the invention allows the burner of the invention to deliver NO. emissions.in the range of single digits to the mid teens (ppm) depending on the number of burners in the array, and the specie;; and concentrations of the species in the fueimix. Thus, in accordance with the invention, it has been discovered that it is possible to combine many known meories of NO, abatement into a single bumer that provides stable operation and appropriate turndown while performing in a range that has not previously been thought possible. In accordance with the invention, shorter flame patterns are possible especially when the fuel comprises heavy hydrocarbons; larger turn down ratios are possible on high hydrogen fuels, particularly when an internal baffle is utilized; much lower noise is experienced around a burner with multiple ports and small jets; either cupped or flat tiles may be utilized interchangeably; staged air tile design allows for NO, adjustment while running; bumer adjustment capabilities in the tile allow for NO, adjustment; tips are easily removed and serviced by design; and the direction of the staged jets at turndown help to stabilize the primary flame.
E CLAIM
1. A method for burning fuel in a combustion zone comprising ;
providing a fuel lean mixture of fuel and air;
delivering said mixture to a centrally located point adjacent a face of a burner tile, said point being disposed adjacent said combustion zone;
causing said mixture to flow radially outwardly from said p.oint in a. plurality of streams across the face of said tile;
combusting the fuel in said mixture in an area of said combustion zone adjacent said face; and
providing staged fuel to said zone at a location spaced from said area; and
combusting said staged fuel' in an environment containing flue gases and not more than about 4% oxygen by volume.
2. A method for burning fuel as claimed in claim 1, wherein said
mixture includes all of the oxygen necessary for burning all of the fuel
in the mixture plus all of the staged fuel.
... 3. A method for burning fuel as claimed in claim 1, wherein said staged fuel is provided to said zone as pure fuel.
4. A method for burning fuel as claimed in claim 2, wherein said staged fuel is provided to said zone as pure fuel.

5. A method for burning fuel as claimed in claim 1, wherein said staged fuel is combusted flamelessly in said environment.
6. A method for burning fuel as claimed in claim 1 or 5, wherein
the fuel in said mixture is combusted flamelessly in said area.
7. A method for operating a burner comprising :
causing a mixture of fuel and air to flow toward to centrally located point adjacent a face to a burner tile;
causing a stream of at least one of additional air and
recirculated flue gas to flow toward a location adjacent said face which

is spaced laterally from said point; and
separating a portion of said mixture and intermixing the same with said stream to thereby create an fuel lean admixture capable of flameless oxidation before the same reaches said location.

8. A method for operating a burner as claimed in claim 7, said
method comprising separating a second portion of said mixture into a
plurality of separate streams, causing said streams to flow radially

outwardly from said point across the face of said tile and causing said
streams to combust to form a flame which surrounds said point, and
flamelessly oxidizing said admixture at said face to create relatively
cool oxidation products.

9. A method as claimed in claim 8, comprising admixing said
oxidation products with said flame to thereby dilute and cool the same.

10. A method as claimed in claim 7, wherein said stream comprises additional air.
11. A method as claimed in claim 7, wherein said stream comprises recirculated flue gas.
12. A method as claimed in claim 7, wherein said stream comprises recirculated flue gas and additional air.
Dated this 29th day of October, 2004.
FOR JOHN ZINK COMPANY L.L.C. By their Agent
(MANISH SAURASTRI) KRISHNA & SAURASTRI

Documents:

612-mumnp-2004-cancelled pages(28-4-2005).pdf

612-mumnp-2004-claims(granted)-(26-4-2005).doc

612-mumnp-2004-claims(granted)-(26-4-2005).pdf

612-mumnp-2004-correspondence(28-12-2005).pdf

612-mumnp-2004-correspondence(ipo)-(11-4-2007).pdf

612-mumnp-2004-drawing(26-4-2005).pdf

612-mumnp-2004-form 1(28-12-2005).pdf

612-mumnp-2004-form 19(11-11-2004).pdf

612-mumnp-2004-form 1a(18-1-2005).pdf

612-mumnp-2004-form 2(granted)-(26-4-2005).doc

612-mumnp-2004-form 2(granted)-(26-4-2005).pdf

612-mumnp-2004-form 3(29-10-2004).pdf

612-mumnp-2004-form 5(18-1-2005).pdf

612-mumnp-2004-form-pct-isa-210(26-4-2005).pdf

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Patent Number

205812

Indian Patent Application Number

612/MUMNP/2004

PG Journal Number

28/2007

Publication Date

13-Jul-2007

Grant Date

11-Apr-2007

Date of Filing

29-Oct-2004

Name of Patentee

JOHN ZINK COMPANY L.L.C.

Applicant Address

11920 EAST APACHE, TULSA, OK 74116,

Inventors:

#	Inventor's Name	Inventor's Address
1	ROGER L. POE	P.O.BOX 718, BEGGS, OK 74421,

PCT International Classification Number

F23D 14/12

PCT International Application Number

PCT/US01/07809

PCT International Filing date

2001-03-12

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	60/208,404	2000-05-31	U.S.A.
2	60/188,807	2000-03-13	U.S.A.