HK1120100B - Coanda gas burner apparatus and methods - Google Patents
Coanda gas burner apparatus and methods Download PDFInfo
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- HK1120100B HK1120100B HK08108716.8A HK08108716A HK1120100B HK 1120100 B HK1120100 B HK 1120100B HK 08108716 A HK08108716 A HK 08108716A HK 1120100 B HK1120100 B HK 1120100B
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Description
Technical field the present invention relates to the combustion of fuel gas containing air and furnace flue gas to suppress nitrogen oxides (' NO)x") and carbon monoxide (" CO ") while producing a stable flame.
Background
Various gas burners with diffusion and premixing capabilities have been developed and successfully utilized. The premixing mode mixes the air and fuel gas into a homogeneous mixture before they enter the furnace for combustion. The diffusion mode injects fuel gas into the air stream so that mixing occurs without a venturi. The flame stabilizes near the exit point and forms thermal and transient oxides of nitrogen. Both of these approaches are conventionally applied to the ignition and combustion of a given fuel gas to generate heat within the process burner.
In a premix diffusion burner, an optimal way of reducing the formation of thermal and transient nitrogen oxides can be determined. Governments are strictly controlling the emissions of nitrogen oxides and carbon monoxide gas produced by process burners and other combustion equipment. Governments are continually demanding better ways to further reduce emissions from existing combustion equipment.
In order to reduce the production of nitrogen oxides and other potentially polluting gases, various improved gas burner devices are being developed. In one approach, all of the air is combusted in the primary zone along with the primary fuel, and the remaining fuel is combusted in the secondary zone. In this method of fuel gas staging, the staged fuel is diluted by the furnace flue gas, which dilutes most of the gas stream during combustion, thereby lowering the combustion temperature of the gases. The nitrogen in the air and flue gas acts as a heat sink by absorbing the heat of the flame. The flue gas can come from the furnace body (external flue gas) or from the furnace itself (internal flue gas). Lowering the gas combustion temperature reduces the formation of nitrogen oxides in the resulting flue gas. U.S. Pat. Nos.5,275,552 (issued to John Zink company on 1/4 of 1994) and 6,729,874B2 (issued to John Zink company on 5/4 of 2004) disclose low NOxExamples of burners and associated methods, both of which are incorporated herein by reference.
Staged combustion and fuel gas dilution additionally create issues that must be addressed, including incombustibility and flame instability. A certain amount of air or flue gas is required to dilute the flame to adequately achieve the reduction of nitrogen oxides. However, if the fuel gas is overly diluted, pilot combustion may be difficult or the ignited flame may become unstable. Flame instability can further destabilize the entire furnace.
Coanda (Coanda) surfaces have been used for flare tubes (flare) to achieve effective flow rates at elevated pressures therein. A coanda surface is simply a curved surface designed to allow the fluid to adhere. A fluid stream ejected at or near a coanda surface tends to adhere to the surface and follow its trajectory. The negative pressure and viscous forces push the fluid flow against the surface. The fluid flow spreads into a thin film or sheet, which causes nearby fluid to mix with the fluid flow in a very efficient manner. The additional surface area imparted to the gas significantly facilitates mixing. For example, in a flare that can emit tens of thousands of pounds of exhaust gas per hour, rapid mixing is desirable. Thus, the coanda surface and coanda effect are commonly used in flare apparatus because it does not require steam, blowers and related equipment.
However, coanda surfaces have not been applied to low NOxIn a process burner arrangement. The burner assembly is smaller and requires much less airflow than a flare tube arrangement. Thus, coanda technology has not been actively applied to process burners. Also, because of the costs involved, many refinery managers have not replaced refiners. Therefore, replacement burner assemblies often must be adapted to existing hearths that define the performance criteria (e.g., length and diameter of the flame) that the burner must meet.
The invention discloses that at low NOxVarious methods of utilizing coanda surfaces in staged fuel gas burners have greatly increased burner efficiency while avoiding problems such as non-combustibility and flame instability.
Disclosure of Invention
According to the present invention, a gas burner apparatus and method are provided which meet the above-mentioned needs and overcome the drawbacks of the prior art. It has been found that coanda surfaces can be combined with a free fluid stream to mix fuel gas with air and dilution (in this example furnace flue gas) while maintaining extended turndown capability and enhanced stability. The coanda surfaces greatly promote mixing of the fuel gas with other fluids in the gas stream. In addition, by using various coanda surfaces, the amount of flue gas introduced into the mixing zone and flame can be greatly increased. Thus, the ability to reduce the nitrogen oxide and carbon monoxide emissions of the burner can be greatly improved while improving the flame quality and heat flux distribution in the furnace. The coanda surfaces and the manner in which the surfaces are disposed inside and outside the burner tile allow flue gas to enter the various mixing and combustion zones of the burner without diluting the fuel gas in the inner boundary layer to a point where it becomes non-combustible or creates an unstable flame. The coanda surfaces also enable the flame shape to be accurately controlled without the need for other components such as flame holders, cones, wings, impingement plates, and the like. These and other advantages of the present invention will be described below.
According to one aspect of the present invention, a gas burner apparatus is provided for injecting a fuel gas and air mixture into a furnace, wherein the mixture combusts in the presence of flue gas while producing small amounts of nitrogen oxides and carbon monoxide. The gas burner apparatus includes a plenum, burner tile, a first fuel gas injection means and a second fuel gas injection means. The device may also include a premix first device for injection.
The plenum includes a housing for attachment to the furnace. The housing includes an upper end connected to the furnace and having an air outlet provided therein, a lower end opposite the upper end, and a sidewall connecting the upper and lower ends together. An air inlet is provided in the interior of at least one of the side wall and the lower end.
The burner tile has a central aperture for receiving air from the housing air outlet. The burner tile includes a bottom end connected to the upper end of the housing and positioned above the air outlet, a top end opposite the bottom end and including a discharge outlet, and a wall connecting the bottom end and the top end and surrounding the central aperture. The wall extends into the furnace and has an inner surface, an outer surface, and at least one gas circulation port extending through the wall. The inner surface of the wall includes an internal coanda surface projecting into the central opening. The internal coanda surface is disposed on the inner surface of the wall adjacent to (preferably above) the gas circulation port.
First fuel gas injection means are connected to a source of fuel gas and operatively associated with the burner means for injecting primary fuel gas into the central opening of the burner tile. The primary fuel gas injection means comprises an outer gas riser connected to a source of fuel gas, the outer gas riser having an outer primary fuel gas discharge nozzle connected thereto and disposed externally of the wall of the burner tile to inject primary fuel gas through the gas circulation ports into the central aperture of the burner tile. The first fuel gas injection device may also include various other components.
In one embodiment, the first fuel gas injection means comprises a premixing unit. The premixing unit comprises a premixing partition plate and a Venturi mixer. The pre-mix baffle extends around the interior surface of the wall of the burner tile and is located below the gas circulation ports while having a plurality of pre-mix gas discharge orifices ("ports") at the top thereof. The venturi mixer includes an inner gas riser connected to a source of fuel gas and having an inner first fuel gas discharge nozzle connected thereto, and a venturi housing operatively associated with the inner gas riser and the first fuel gas discharge nozzle. The venturi housing is connected to the premix membrane to supply a primary fuel gas and air mixture to the premix membrane. The pre-mix unit is capable of delivering a range of lean mixtures of primary fuel gas and air into the central opening of the burner tile.
The secondary fuel gas injection means is connected to a source of fuel gas and operatively associated with the burner means for injecting a secondary stage fuel gas from outside the burner tile to a point adjacent the discharge outlet of the burner tile (preferably on or adjacent the exterior surface of the burner tile). The secondary fuel gas injection means comprises an outer gas riser connected to a source of fuel gas and having a secondary fuel gas discharge nozzle connected thereto for injecting a secondary fuel gas onto or adjacent the outer surface of the wall of the burner tile. In one configuration, the primary fuel gas injection means and the secondary fuel gas injection means utilize the same outer gas riser and fuel gas discharge nozzle. The fuel gas discharge nozzle serves as both the first fuel gas discharge nozzle and the second fuel gas discharge nozzle. The nozzle includes one or more ports for injecting fuel gas through a gas circulation port extending through the wall of the burner tile and one or more ports for injecting fuel gas on or near the exterior surface of the wall of the burner tile.
The exterior surface of the wall of the burner tile preferably also includes an external coanda surface projecting outwardly therefrom. The outer gas risers and secondary fuel gas discharge nozzles inject secondary stage fuel gas onto or near the external coanda surface. The external coanda surfaces preferably extend around the entire exterior surface of the wall of the burner tile; however, it may also extend in spaced relation around the exterior surface of the wall of the burner tile. The spaced external coanda surfaces are preferably separated by an external plane which can be vertical or inclined toward the interior of the central opening of the burner tile.
In another embodiment, the gas burner apparatus includes a plenum, burner tile, a first fuel gas injection means and a second fuel gas injection means. The plenum includes a housing for attachment to the furnace. The housing includes an upper end connected to the furnace and having an air outlet provided therein, a lower end opposite the upper end, and a sidewall connecting the upper and lower ends together. An air inlet is provided in an interior of at least one of the side wall and the lower end.
The burner tile has a central aperture for receiving air from the housing air outlet. The burner tile includes a bottom end connected to the upper end of the housing and positioned above the air outlet, a top end opposite the bottom end and including a discharge outlet, and a wall connecting the bottom end and the top end and surrounding the central aperture. The wall extends into the furnace and has an inner surface, an outer surface, and at least one gas circulation port extending through the wall. The wall extends into the furnace space and has an inner surface and an outer surface, the outer surface of the wall including an external coanda surface projecting outwardly from the outer surface.
First fuel gas injection means are connected to a source of fuel gas and operatively associated with the burner means for injecting primary fuel gas into the central opening of the burner tile. Secondary fuel gas injection means is also connected to the source of fuel gas and is operatively associated with the burner means for injecting secondary stage fuel gas from outside the burner tile to a point adjacent the discharge outlet of the burner tile. The secondary fuel gas injection means comprises an outer gas riser connected to a source of fuel gas and having a secondary fuel gas discharge nozzle connected thereto for injecting secondary stage fuel gas onto or adjacent the external coanda surface.
In another aspect, the invention comprises a burner tile for use in conjunction with a burner plenum to form a gas burner apparatus for injecting a fuel gas and air mixture into a furnace, wherein the mixture is combusted in the presence of flue gas while producing small amounts of nitrogen oxides and carbon monoxide. The burner tile of the present invention is the burner tile described above in connection with the gas burner apparatus of the present invention. The burner tile of the present invention may be used in retrofit applications.
In another aspect, the present invention includes a gas tip for use in conjunction with a gas burner apparatus. The gas tip includes a gas tube for connection to a source of fuel gas, a gas deflector connected to the gas tube, and a fuel gas outlet disposed between the gas tube and the gas deflector. The gas deflector has an outer surface including a coanda surface and the coanda surface is positioned relative to the fuel gas outlet such that fuel gas discharged from the fuel gas outlet follows the path of the coanda surface. The gas deflector is preferably in the shape of a tulip. The gas tip of the present invention may be used, for example, as a secondary stage fuel gas discharge nozzle of the gas burner apparatus of the present invention, a pilot burner tip of the gas burner apparatus of the present invention, or a primary inner fuel gas discharge nozzle attached to a central inner gas riser (e.g., a central gas lance). The gas tip of the present invention may also be used in conjunction with a set of gas nozzles as the first gas tip around the inner perimeter of the showerhead.
In another aspect, the present invention provides a method of combusting a mixture of gas and air in the presence of furnace flue gas to generate heat within a furnace, wherein a gas burner apparatus is utilized having a mixing zone for mixing air, fuel gas and flue gas prior to combustion, the method comprising the steps of: (a) providing a coanda surface within the mixing zone; (b) injecting fuel gas onto or adjacent the coanda surface in a manner that entrains flue gas from outside the mixing zone into the mixing zone and causes the flue gas to mix with the air and fuel gas in the mixing zone; (c) discharging a mixture of combustion air, fuel gas and flue gas from the mixing zone into the furnace; and (d) combusting the mixture of air, fuel gas and flue gas from the mixing zone in a furnace.
In one embodiment, the mixing zone is surrounded by walls and the mixture of air, fuel gas and flue gas is injected from the mixing zone into the main reaction zone in the furnace. In this embodiment, the method further comprises the steps of: (e) providing an external coanda surface on the outer surface of the wall; and (f) injecting a second staged fuel gas stream onto or adjacent the external coanda surface in a manner to entrain flue gas into the second staged fuel gas stream to produce a second fuel gas/flue gas mixture and combust the second fuel gas/flue gas mixture in a second reaction zone within the furnace.
In another embodiment, the invention of the present invention comprises the steps of: (ii) (a) providing a coanda surface on an exterior surface of a wall of a burner apparatus; (b) injecting the main fuel gas into the mixing zone in a manner such that the fuel gas mixes with the air in the mixing zone; (c) discharging the mixture of air and fuel gas from the mixing zone; and (d) combusting the mixture of air and fuel gas discharged from the mixing zone in a first reaction zone within the furnace; (e) injecting the second staged fuel gas stream onto or adjacent to the external coanda surface in a manner that entrains flue gas into the second staged fuel gas stream to produce a second fuel gas/flue gas mixture and combusts the second fuel gas/flue gas mixture in a second reaction zone within the furnace.
The interior surface of the wall of the burner apparatus preferably also includes an internal coanda surface. The fuel gas injected into the mixing zone is injected onto or near the internal coanda surfaces in a manner that entrains flue gas from outside the mixing zone into the mixing zone and causes the flue gas to mix with the air and fuel gas in the mixing zone.
The objects, features and advantages of the present invention will become apparent to those skilled in the art when the preferred embodiments described below are read in conjunction with the accompanying drawings.
Drawings
FIG. 1 is a sectional view of the gas burner apparatus of the present invention installed on the bottom of a furnace.
Fig. 2 is a perspective view of a burner tile of the gas burner apparatus of the present invention.
Fig. 3 is a cross-sectional view of a burner tile of the gas burner apparatus of the present invention.
FIG. 3A is a cross-sectional view similar to FIG. 3, further illustrating a gas circulation restriction arrangement that may be incorporated into the burner tile of the present invention.
FIG. 4 is an enlarged detail view of a portion of the burner tile shown in FIG. 3 illustrating the flow of gas in conjunction with the burner tile.
FIG. 4A is an enlarged detail view of the portion of the burner tile shown in FIG. 3A depicting the gas flow associated with the burner tile.
FIG. 4B is an enlarged detail view of another portion of the burner tile shown in FIG. 4.
Fig. 5 is a cross-sectional view taken along line 5-5 of fig. 2.
Fig. 6 is a cross-sectional view taken along line 6-6 of fig. 2.
FIG. 7 is another detail view of a portion of the burner tile of FIG. 3 depicting a portion of the pre-mix unit.
FIG. 8 is a cross-sectional view similar to FIG. 1, but depicting the use of a central venturi mixer in place of the air gun shown in FIG. 1.
FIG. 9 is a cross-sectional view similar to FIGS. 1 and 8, but depicting the use of multiple inner gas risers in place of the pre-mix unit. Fig. 9 also depicts the use of a conventional pilot burner assembly in conjunction with the gas burner assembly of the present invention.
FIG. 10 is a cross-sectional view of the burner tile of FIG. 3, but depicting a different outer gas riser configuration.
FIG. 11 is a sectional view illustrating an alternative embodiment of the burner tile of the present invention.
FIG. 11A is a cross-sectional view taken along line 11A-11A of FIG. 12, illustrating a variation of the flat wall section (angled) of the burner tile of FIG. 11.
FIG. 11B is a cross-sectional view taken along line 11B-11B of FIG. 12, illustrating another variation of the flat wall section (vertical/perpendicular) of the burner tile of FIG. 11.
Fig. 12 is a cross-sectional view taken along line 12-12 of fig. 11.
FIG. 13 is a sectional view illustrating another embodiment of the burner tile of the present invention.
FIG. 14 is an enlarged detail view of a portion of the burner tile shown in FIG. 13.
Fig. 15 is a cross-sectional view taken along line 15-15 of fig. 13.
FIG. 16 is a sectional view illustrating yet another embodiment of the burner tile of the present invention.
FIG. 17 is an enlarged detail view of a portion of the burner tile shown in FIG. 16.
Fig. 18 is a cross-sectional view taken along line 18-18 of fig. 16.
Fig. 19 is a cross-sectional view taken along line 19-19 of fig. 16.
FIG. 20 is a sectional view illustrating yet another embodiment of the burner tile of the present invention.
Fig. 21 is a cross-sectional view taken along line 21-21 of fig. 20.
FIG. 22 is a partial cross-sectional view depicting a gas tip of the present invention configured for use as a pilot assembly.
FIG. 23 is an enlarged detail view of a portion of the gas tip shown in FIG. 22.
Detailed Description
Referring now to the drawings, and more particularly to FIG. 1, there is depicted a gas burner apparatus of the present invention, generally designated by the numeral 10. As shown in FIG. 1, the burner apparatus 10 is sealingly mounted to a wall 12 (preferably a bottom wall or floor) of a furnace space 14 of a furnace 16 (the entire furnace not shown) above an opening 18 in the wall. Although the gas burner apparatus is generally vertically mounted and upwardly directed as shown in fig. 1, it should be understood that the gas burner apparatus 10 may be otherwise mounted. For example, the gas burner 10 may be mounted horizontally and pilot horizontally or vertically, or may be mounted vertically and pilot downward (flame downward). Preferably, the gas burner apparatus 10 is mounted vertically on the bottom wall of the furnace space 14 as shown and the flame is directed upwardly.
The gas burner apparatus 10 discharges a fuel gas and air mixture into the furnace space 14 of the furnace 16 where the mixture is combusted in the presence of flue gas, while producing small amounts of nitrogen oxides and carbon monoxide. The gas burner apparatus 10 includes a plenum 20, the plenum 20 including a housing 22 for mounting on a furnace. The housing includes an upper end 24, a lower end 26 opposite the upper end, and a sidewall 28 connecting the upper and lower ends. The upper end 24 of the housing 22 is provided with an air outlet 30. As shown in FIG. 1, the upper end 24 of the housing 22 is attached to the furnace wall 12 such that the air outlet 30 is located below the furnace wall opening 18. An air inlet 32 is provided in the interior of at least one of the side wall 28 and the lower end 26 of the housing 22. Preferably, as shown in FIG. 1, the air inlet 32 is disposed in the side wall 28 of the housing 22.
As shown in FIG. 1, the housing 22 is secured to the bottom wall or base 12 of the furnace 16 by a flange 34 and a plurality of bolts 36 that pass through complementary holes 38 in the flange and the bottom wall of the furnace. The furnace wall 12 includes an inner layer of insulating material 40 attached thereto. An airflow regulator or damper 42 for regulating the flow rate of air through the air inlet 32 is mounted on the air inlet. The damper 42 includes a plurality of adjustable vanes 44, and the vanes 44 are rotatable between vertical and horizontal directions to open and close the damper. A silencer 46 for reducing jet and combustion noise is also mounted on the air inlet 32. As will be appreciated by those skilled in the art, the gas burner apparatus 10 may be a natural draft burner (i.e., air required for combustion is automatically introduced into the enclosure 22), a forced draft burner (e.g., a fan is used to blow combustion air into the enclosure), a balanced draft burner (e.g., a plurality of fans are used to blow air into or out of the burner to achieve proper balance of combustion air), or variations thereof. The burner assembly 10 can burn a variety of different types of fuel gases, including natural gas, hydrogen, propane, ethane, or other refinery-type fuels.
The gas burner apparatus 10 further includes a burner tile 50 having a central aperture 52 for receiving air from the air outlet 30 of the housing 22. The burner tile 50 includes a bottom end 54, a top end 56 opposite the bottom end, and a wall 58 connecting the bottom and top ends and surrounding the central opening 52. The bottom end 54 of the burner tile 50 is attached to the upper end 24 of the housing 22 above the air outlet 30 of the housing. The top end 56 of the burner tile 50 includes a discharge outlet 60 therein.
Referring now to fig. 1-6, the wall 58 of the burner tile 50 extends into the furnace space 14 and has an upper portion 62, a lower portion 64, an inner surface 66 and an outer surface 68. The wall 58 further includes a plurality of gas circulation ports 70 extending therethrough. The interior surface 66 of the wall 58 includes a plurality of internal coanda surfaces 80 disposed adjacent to or above (above as shown) the gas circulation ports 70, each internal coanda surface projecting toward the central opening 52 of the burner tile 50. Each internal coanda surface 80 and gas circulation port 70 are disposed within a recessed section 82 of the inner surface 66 of the wall 58. Each recessed section 82 includes opposing sidewalls 84 and 86 that extend from the inner surface 80 of the wall 58 into the central bore 52. As shown in FIG. 4B, the side walls 84 and 86 extend further into the central bore 52 than the internal coanda surfaces 80 located within the respective recessed sections 82. Stated another way, the internal coanda surfaces 80 are inset into the interior surface 66 of the wall 58. The internal coanda surfaces 80 are preferably inset about 0.25 to about 0.75 inches into the interior surface 66 of the wall 58. As further described below, the space between the internal coanda surfaces 80 and the interior surface 66 of the remainder of the wall 58 prevents fuel gas and/or flue gas from being blown off of the internal coanda surfaces by the flow of flue gas and/or air through the central opening 52 of the burner tile 50.
To produce an effective coanda effect, the surface of the internal coanda surface 80 should be substantially smooth and have a substantially uniform radius or the same arc. Also, it is important for each internal coanda surface to have sufficient curvature to adequately attract the gas stream at the split. If the coanda surface does not have sufficient curvature and surface area, the surface may not have sufficient surface area to initiate the coanda effect caused by the momentum of the gas (i.e., the gas stream is not attracted to the surface). To ensure a sufficient coanda effect, the ratio of the diameter of the fuel discharge port (the average diameter of each port if multiple fuel discharge ports are used) of the gas injection fuel gas entering and passing through the gas circulation ports 70 at or near the internal coanda surface 80 ("primary port diameter") to the radius of the internal coanda surface ("internal coanda radius") must be at least 7: 1. For example, the ratio of the discharge port diameter (or average diameter of the plurality of discharge ports) of first fuel gas discharge nozzle 166 to the internal coanda radius needs to be at least 7: 1. Preferably, the ratio of the primary port diameter to the internal coanda radius is at least 10: 1, and most preferably at least 12: 1. Thus, for example, with a primary port diameter of 0.0625 inches and an internal coanda radius of 0.75 inches, the ratio of primary port diameter to coanda radius is 12: 1.
Assuming that the coanda surface has sufficient curvature or surface area, even for small gas ports, the gas flow or jet is aligned tangential to the curvature of the coanda surface to initiate the proper coanda effect. This can vary significantly with large coanda surfaces used in flare tubes, for example, that employ a slotted spray scheme in combination with a greater mass flow.
In addition to the parameters described above, the particular size and shape of the internal coanda surfaces 80 can vary depending on the size and shape of the gas circulation ports, the size and shape of the burner tile, and other factors associated with the particular application. The orientation (i.e., vertical, horizontal, etc.) of the internal coanda surfaces 80 on the inner surface 66 can also vary depending on the factors discussed above.
The internal coanda surfaces 80 are a very important component of the gas burner 10 of the present invention. They can entrain large amounts of flue gas without over diluting the fuel gas and without hindering combustion or causing flame instability. This is due at least in part to the fuel-rich inner boundary layer. The primary fuel gas and air flow injected through the gas circulation ports 70 is pushed against and maintained on the coanda surfaces 80. The fuel gas stream separates and expands into a membrane having a larger surface area. Exposing the center of the gas core. Thus, the distance and time required to mix the flue gas with the fuel gas (and any other fluids involved in a particular application, such as air and/or steam) is substantially reduced. More flue gas and air (and other fluids if desired) can be mixed with the fuel gas jet. Thus, the flame is more stable, the content of nitrogen oxides in the flue gas produced by the burner is reduced, and the flame can be shaped more easily.
As shown in FIGS. 3A and 4A, in one configuration, the burner tile 50 further includes a circulation choke means 87 disposed in the gas circulation port 70 for inhibiting the flow of air from the central opening 52 of the burner tile 50 through the gas circulation port and into the exterior of the burner tile. The circulation choke means 87 comprises a baffle 88 for each gas circulation port 70. The baffles 88 are attached to the wall 58 of the burner tile 50 and extend upwardly to the respective gas circulation ports 70. As shown, the baffle 88 may be an integral part of the refractory burner tile. The circulation choke means 87 is used in applications where it is necessary to reduce the flow of fluid from the interior of the sprinkler head through the gas circulation ports 70 to the exterior of the burner tile. For example, when a diffusion jet is not injected through the recycle gas port 70, outward flow of fluid may occur. Eliminating the outward flow of air through the ports 70 helps reduce emissions and improves the ability of the flame to form a designed shape (when a diffusion jet is not injected through the ports 70 to maintain a fluid seal between the two fluid flow regions). The circulation choke means 87 prevents air from shorting across the burner tile and thus prevents increased emissions of oxides of nitrogen while keeping the flame from contacting the exterior surface of the wall of the burner tile. The circulation choke 87 also prevents any premature contact between the premixed gas and the diffusion gas in the central bore 52. In some cases, if the baffle 88 is not in place, the momentum of the diffusion gas will push the premixed flame into the circulation port 70 where it will prematurely carry air into the bottom of the diffusion jet.
The entire burner tile 50, including the baffle 88 (when utilized) is made of a heat and flame resistant refractory material, i.e., a material that has the ability to retain its physical shape and chemical characteristics even at high temperatures. Examples of refractory materials that may be used include silicon carbide, alumina mixtures, and ceramic fiber materials.
Referring now particularly to fig. 4, 4A and 4B, the gas circulation ports 70 are described in detail. Each gas circulation port 70 includes a flange 90, an upper surface 92 (part of the internal coanda surface 80) and a pair of opposed side walls 94 and 96 connecting the flange and the upper surface. As shown in FIG. 4, the burner tile does not include a circulation choke 87, and the flange 90 is either flat, i.e., substantially coplanar with the upper surface 92 of the port 70, or slopes downwardly from the inner surface 66 to the outer surface 68 of the wall 58. Preferably, the flange 90 slopes downwardly from the inner surface 66 to the outer surface 68 of the wall 58 at an angle of 15 to-60. For example, the flanges 90 may be angled downwardly at a greater angle when the outer gas risers (discussed below) do not substantially penetrate the wall 12 of the furnace. In a configuration where the outer gas risers extend substantially above the furnace bottom wall 12, the flanges 90 are inclined downwardly at an angle, for example, from about 10 ° to about 60 °. Preferably, the flange 90 slopes downwardly from the inner surface 66 to the outer surface 68 of the wall 58 at an angle of 15 ° to 25 °. When the burner tile 50 includes the circulation choke means 87, as shown in FIG. 4A, the flange 90 slopes downwardly from the inner surface 66 to the outer surface 68 of the wall 58 at a substantial angle due to the presence of the baffle 88 in the gas circulation port 70. The downward slope of the flange serves to prevent air within the central bore 52 from radially exiting the central bore 52 through the port 70. Whether the circulation choke 87 is used and the angle at which the flange 90 is inclined will depend on the particular application.
The inner surface 66 of the upper portion 62 of the wall 58 further includes a first bluff body 100 having an upwardly facing flat surface 102 that faces the discharge outlet 66 of the burner tile. The first bluff body 100 extends around the entire inner surface 66 of the wall 58. Each internal coanda surface 80 includes a lower end 104, an upper end 106 and a lug 108 connecting the lower end and the upper end. The lower end 104 of the internal coanda surface 80 extends above the top of the gas circulation port 70. The upper end 106 of the internal coanda surface 80 terminates at the flat surface 102 of the primary bluff body 100. The top end 56 of the burner tile 50 includes a second bluff body 110 having an upwardly facing flat surface 112 that faces the furnace space 14. The second bluff body 110 extends around the entire inner surface 66 of the wall 58. The primary bluff body 100 creates a low pressure region and provides a mixing region above the central bore 52. The secondary bluff body 110 serves to stabilize the gas at the discharge opening 60 of the burner tile 50. The staged fuel has the ability to enrich the stabilized fuel at the top 56 of the burner tile 50 in the event that the fuel is too little or diffuse.
The exterior surface 68 of the wall 58 of the burner tile 50 includes a plurality of open sections 116 (which include the gas circulation ports 70) and a plurality of non-open sections 118 (which do not include the gas circulation ports 70). The upper portion 62 of the exterior surface 68 of the wall 58 of the burner tile 50 also includes an external coanda surface 130 projecting from the exterior surface 68.
In one embodiment, as shown in FIGS. 1-10, the external coanda surfaces 130 extend around the entire outer surface 68 of the wall 58. This arrangement allows the shape of all of the staged fuel to be determined by the coanda surfaces.
In another embodiment, as shown in FIGS. 11-12, the upper portion 62 of the exterior surface 68 of the wall 58 of the burner tile 50 includes a plurality of external coanda surfaces 130, each external coanda surface 130 projecting outwardly from the exterior surface 68. In the embodiment shown in FIGS. 11-12, the external coanda surfaces 130 are spaced apart by external planes 132. As shown in FIGS. 11A and 11B, the outer planar surface 132 can be inclined toward the central opening of the burner tile (FIG. 11A) or upright or perpendicular (substantially parallel to the longitudinal axis of the burner tile) (FIG. 11B). If inclined, the outer flat surface 132 is inclined inwardly at an angle of 5 to 25. The alternating use of external coanda surfaces and flat (straight) surfaces (inclined or perpendicular) provides better control over the shape of the flame. The staged fuel can be shaped more quickly to maintain a tongue flame. This is particularly important where it is desired to eliminate the effect of the wall 58. A portion of the fuel gas may be injected at an aggressive angle to further promote flame shaping, or to obtain a more aggressive staging fuel bias.
In yet another embodiment, as shown in FIGS. 13-15, the upper portion 62 of the exterior surface 68 of the wall 58 of the burner tile 50 includes an outer planar surface 134 that extends around the entire exterior surface 68 of the wall 58. The outer flat surfaces 134 are inclined inwardly at an angle of 5 ° to 25 °. It may also be substantially upright or vertical (not inclined inwardly). This embodiment makes the staged injection more vigorous, thereby achieving effective flame shaping capability.
Thus, the various configurations of the upper portion 62 of the exterior surface 68 of the burner tile 50 allow the size and shape of the flame to be precisely controlled depending on the application. In addition, other advantages are also provided.
To produce a significant coanda effect, the surface of the external coanda surface 130 should be substantially smooth and have a substantially uniform radius or the same arc. Also, it is important for each external coanda surface to have sufficient curvature to adequately attract the gas stream at the split. If the coanda surface does not have sufficient curvature and surface area, the surface will not have sufficient surface area to initiate the coanda effect caused by the momentum of the gas (i.e., the gas stream will not be attracted to the surface). To ensure a sufficient coanda effect, the ratio of the diameter of the fuel discharge ports that inject fuel gas at or near the external coanda surface 130 (the average diameter of the ports if multiple fuel discharge ports are used) ("second port diameter") to the radius of the external coanda surface ("external coanda radius") must be at least 7: 1. For example, the secondary fuel gas nozzles 166 have a ratio of port diameter (or average diameter if multiple ports are used) to external coanda radius of at least 7: 1. It is preferred that the ratio of the diameter of the secondary port to the external coanda radius is at least 10: 1, most preferably at least 12: 1.
In addition to the above parameters, the particular size and shape of the external coanda surfaces 130 can vary depending on the size and shape of the burner tile and other factors associated with a particular application. The orientation (i.e., vertical, horizontal, etc.) of the external coanda surfaces 130 on the outer surface 68 can also vary depending on the factors discussed above.
The external coanda surfaces 130 are a very important component of the gas burner apparatus 10 of the present invention. The surface 130 serves to entrain more flue gas into the staged fuel gas stream and greatly facilitate this mixing process. In combination with the more conventional external flats 132 or flats 134, the external coanda surfaces allow for a high degree of accuracy and flexibility in achieving the type and degree of staged combustion required for a particular application. The external coanda surfaces 132 promote dilution of the fuel gas while maintaining a stable flame. If desired, the external coanda surfaces 132 can be used in conjunction with the burner tile 50 of the present invention without the gas circulation ports 70 in the burner tile.
In another embodiment, as shown in FIGS. 16-19, the burner tile 50 further includes a lip 140 extending transversely from the inner surface 66 of the wall 58 to the central opening 52 of the burner tile. A lip 140 is attached to the wall 58 adjacent the top end 56 of the burner tile 50 and extends around the inner surface 66 of the wall. The lip 140 includes a lower end 142, an upper end 144, and a body 146 connecting the lower and upper ends. The body 146 includes a plurality of projections 150 extending toward the central opening 52 of the burner tile. The projections 150 include various cross-sectional shapes (e.g., oval, square, and triangular) and are separated by grooves 152. As best shown in fig. 17, the lower end 142 is curved, which facilitates the flow of fluid under the lip 140. The entire lip 140 is used to turn the fluid through a 90 bend. The fluid is fully diluted by air; the flame speed becomes low. In the event that stabilization is required due to excessive fuel dilution, the protrusion 150 and groove 152 stabilize the gas and help stabilize the flame. The radial projections act as bluff bodies to trap the lean mixture and stabilize it at the end of the tile surface. This geometry may also be used for the central air gun 170 or the central venturi mixer 176 to provide a better flameout mechanism for the flame.
Depending on the application, the gas burner apparatus 10 may include both internal coanda surfaces 80 and external coanda surfaces 130. Preferably, the gas burner apparatus 10 includes both internal coanda surfaces 80 and external coanda surfaces 130.
The gas burner apparatus 10 further comprises a first fuel gas injection means 160 and a second fuel gas injection means 162. The primary fuel gas injection means 160 is connected to a source of fuel gas (not shown) and is operatively associated with the burner apparatus 10 for injecting primary fuel gas into the central opening 52 of the burner tile 50. The secondary fuel gas injection means 162 is connected to a source of fuel gas (not shown) and is operatively associated with the burner apparatus 10 for injecting secondary stage fuel gas from the exterior of the central opening 52 and burner tile 50 to a point adjacent the discharge outlet 60 of the burner tile. As used herein and in the appended claims, primary fuel gas refers only to fuel gas injected into the central opening 52 of the burner tile (i.e., any gas injected into the combustion zone defined by the burner tile 50). The secondary stage fuel gas refers only to the fuel gas sprayed on the exterior or above the wall 58 of the burner tile 50.
The first fuel gas injection means may include various components that may be used alone or in combination according to a specific application.
As a first component, the first fuel gas injection device 160 includes a plurality of outer gas risers 164 connected to a source of fuel gas. Each outer gas riser 164 has an outer primary (diffusion) fuel gas discharge nozzle 166 (which includes one or more gas ports therein) disposed externally of the wall 58 of the burner tile for injecting primary fuel gas through the gas circulation ports 70 on or near the internal coanda surface 80. The primary fuel gas is preferably injected directly onto the internal coanda surfaces 80. As used herein and in the appended claims, a "nozzle," such as a "fuel gas discharge nozzle," is any type of gas tip (typically connected to a gas riser) that includes one or more gas discharge orifices (e.g., ports or slots) therein for discharging or injecting a stream or jet of gas from the nozzle. As used herein and in the appended claims, injecting fluid "at or near a surface" (herein fuel gas) means injecting fluid directly onto the surface or in close enough proximity to the surface to produce an effect (e.g., a coanda effect) on the surface. For example, it is sufficient that the fuel gas stream or jet is injected very close to the curved portion of the coanda surface because the pressure of the stream or jet in combination with the surface area of the curved surface will initiate the coanda effect. In applications where the temperature of the burner apparatus 10 is very high (e.g., 2000F. or greater), the outer gas risers 164 do not extend substantially above the furnace wall 12 in order to avoid damage. In other applications, the standpipe 164 and nozzle 166 pass through and above the wall 12.
As another component, the first fuel gas injection means 160 may further comprise one or more inner gas risers 167, each inner gas riser being connected to a source of fuel gas and being disposed inside the burner housing 22. Each inner gas riser has an inner primary fuel gas discharge nozzle 168 (which includes one or more gas ports therein) for directly injecting primary staged fuel gas into the central opening 52 of the burner tile. As shown in FIG. 9, a plurality of inner gas risers 167 and inner primary fuel gas discharge nozzles 168 are used to inject fuel gas directly into the central opening 52 of the burner tile 50. As shown, one or more risers 167 and corresponding nozzles 168 may be provided at each gas circulation port 70 to inject a portion of the primary fuel gas directly onto or near the internal coanda surface 80 to help stabilize the flame.
As shown in fig. 1, 3 and 3A, an inner gas riser 167 and corresponding inner fuel gas discharge nozzle 168 may be used to form a central air gun 170. The inner gas riser 167 is connected to a source of fuel gas and extends to the center of the central opening 52 of the burner tile 50. An inner fuel gas discharge nozzle 168 in the form of a round head is connected to the inner gas riser 167. A gas dispersion cone 172 is mounted on the central riser and surrounds the rounded tip 168 for dispersing gas exiting the tip. The central air gun 170 may be used to inject a free jet of primary fuel gas directly into the burner tile 50. The momentum of the free jet of primary fuel gas together with the momentum of the air pushes the flue gas into the central opening 52 of the burner tile 50, helping to reduce harmful emissions.
As shown in fig. 8, an inner gas riser 167 and corresponding inner fuel gas discharge nozzle 168 may be used to form a central venturi mixer 176. The inner gas riser 167 is connected to a source of fuel gas and is disposed inside the burner housing 22. An inner fuel gas discharge nozzle 168 in the form of a gas tip (which includes one or more gas ports therein) is connected to inner gas riser 167. The venturi housing 178 is operably associated with the standpipe 167 and nozzle 168. A venturi housing 178 is mounted on the inner gas riser 167 above the tip 168 for receiving fuel gas discharged from the tip. The venturi housing 178 includes an inlet 180, an outlet 182, and a venturi body 184 having a narrowed portion 186. The venturi body 184 creates a low pressure zone that draws air into the housing 178. A mixture of fuel gas and air is formed within the housing 178. The central venturi mixer may be used to directly inject a premixed stream of primary fuel gas and air to the burner tile 50. It creates a lean or over lean premixing zone, thereby shortening the flame length and further reducing nitrogen oxide emissions. Multiple venturi mixers 176 may be used if desired.
As shown in FIGS. 1, 3A, 7 and 8, the first fuel gas injection means 160 may further comprise a pre-mix unit 190 extending into the central opening 52 of the burner tile 50. As best shown in FIG. 7, the pre-mix unit 190 includes a pre-mix baffle 192, the pre-mix baffle 192 surrounding and slightly inset (for optimal stability) within the interior surface 66 of the wall 58 of the burner tile 50 below the gas circulation ports 70 in the wall. A plurality of premix gas ports 194 are provided at the top of the baffle 192. A pair of venturi mixers 196 supply premixed streams of fuel gas and air into the membrane 192. Each venturi mixer 196 includes an inner gas riser 198, the inner gas riser 198 being connected to a source of fuel gas and having an inner primary fuel gas discharge nozzle 200 in the form of a gas tip (which includes one or more gas ports therein) connected thereto. A venturi housing 202 is operatively associated with the standpipe 198 and the nozzle 200. A venturi housing 202 is attached to the standpipe 198 and is configured to receive fuel gas discharged from the nozzle 200. The venturi housing 202 includes an inlet 204, an outlet 206, and a venturi body 208 preferably having a narrow portion 210 therein. In some applications, the narrow portion 210 is not necessary. The venturi body 208 creates a low pressure zone that draws air into the housing 202. A mixture of fuel gas and air is formed within the housing 202 and directed into the premix membrane 192. The pre-mix unit 190 may be used to inject a pre-mixed stream of primary stage fuel gas and air around the perimeter of the inner surface 66 of the wall 58 of the burner tile 50.
The premixing unit 190 may be used to premix the entire main fuel gas, or to premix a portion of the main fuel gas, while the remainder is supplemented by diffused main fuel gas. The premixing unit may be a fixed or adjustable heat-releasing component as with the rest of the combustor. The pre-mix units 190 release fuel evenly along the inner circumference of the wall 58 of the burner tile 50, thereby improving turndown and stability. It also helps to reduce nitrogen oxide emissions because the uniform release of air and fuel can reduce the temperature of the nuclei, typically measured in a diffusion free jet. When the premixing unit 190 is used in conjunction with diffusion, the diffusion jet will be fluxed more thinly and/or dispersed because the diffusion flame will then be a flame stabilized by a lean premixed flame. Because the diffusion jets are stabilized flames, the flow area of the gas circulation ports 70 can be increased to more than 6 times the flow area that would normally be available without adversely affecting flame stability (the flame being stabilized by the premixed flame produced by the premixing unit). The premix units maintain a constant heat release. This makes it possible to design the zone such that flashback (flashback) is not a problem in the fuel range. This not only improves turndown capability due to flame holding, but also ensures that less main fuel is available while maintaining acceptable port sizes. This means that the heat release of the primary zone can be generated from as little as one percent (1%) of the total fuel in the primary zone. Due to the larger gas circulation ports, carbon monoxide (CO) emissions can be minimized during cold start. The significantly larger gas circulation ports push a large amount of flue gas into the burner where the CO is re-combusted to reduce the CO content measured in the oven box.
The pre-mix unit 190 also provides a pilot source for the remaining burner combustion zones. It may take on a variety of shapes and hole numbers as required by a particular application. It can be deliberately adjusted to produce a fuel gas-air mixture that is as lean as necessary to further reduce nitrogen oxide emissions. The pre-mix unit 190 serves as the minimum heat release component of the burner so that a decoking cycle of low heat release can be accomplished without affecting flame stability if desired. The main gas delivery components can be shut down in addition to the pre-mix unit. It then serves to give off very little heat while maintaining stability. Upon re-pilot of the main portion of the combustor, the premix unit can be brought back online at a very low pressure, which is much lower than what would normally be possible.
The secondary fuel gas injection means 162 comprises a plurality of outer gas risers, each of which is connected to a source of fuel gas and to which is connected a secondary fuel gas discharge nozzle (comprising one or more ports therein). The secondary fuel gas injection means is used to inject a secondary stage fuel gas onto or adjacent to the exterior surface 68 (e.g., the external coanda surface 130) of the wall 58 of the burner tile 50. The secondary stage fuel gas is preferably injected directly onto the outer surface 68 (e.g., the external coanda surface 130). The risers and nozzles can take a variety of configurations. For example, as shown in FIGS. 1, 4 and 4A, the outer gas standpipe and second fuel gas discharge nozzle of the second fuel gas injection device are also the outer gas standpipe 164 and nozzle 166 of the first fuel gas injection device. The nozzle 166 includes a first port for injecting primary fuel gas into the gas circulation port 70 and a second port for injecting secondary stage fuel gas onto or adjacent the exterior surface 68 (e.g., the external coanda surface 130) of the wall 58 of the burner tile 50. In another configuration, each outer gas riser 164 includes separate primary and secondary fuel gas discharge nozzles. In yet another configuration, as shown in FIG. 10, the first fuel gas injection means and the second fuel gas injection means employ respective outer gas risers. A plurality of outer gas risers 164 are provided for injecting primary fuel gas through the gas circulation ports 70 into the central opening 52 of the burner tile 50, wherein each outer gas riser 164 is connected to a source of fuel gas and has an outer primary fuel gas discharge nozzle 166 (which includes one or more gas ports therein) attached thereto. Independent outer gas risers 214 are used to inject secondary stage fuel gas onto or adjacent to the outer surface 68 (e.g., the external coanda surface 130) of the wall 58 of the burner tile 50, each outer gas riser 214 being connected to a source of fuel gas and having a secondary fuel gas discharge nozzle 216 (comprising one or more gas ports therein) connected thereto. The particular configuration of riser employed will depend on the amount of staging gas and the desired flame shape.
The burner housing 22 and burner tile 50 are preferably circular in cross-sectional shape. However, the housing 22 and burner tile can have other shapes. For example, the cross-sectional shape of the housing 22 and the burner tile 50 can be oval, square, or rectangular. The shape may be symmetrical or asymmetrical as long as the coanda surface is properly applied. The shape of the housing 22 need not be the same as that of the burner tile 50. Fig. 20 and 21 depict a burner tile 50 having a rectangular cross-sectional shape. For example, a rectangular burner tile 50 can be used to create a flat flame and is quite effective in wall-burning applications.
As shown in FIG. 1, in addition to the premixing unit 190, several components of the primary fuel gas injection apparatus 160 and the secondary fuel gas injection apparatus 162 are connected to a burner header 217, and the burner header 217 is connected to a source of fuel gas (e.g., a main furnace header). The gas burner manifold 217 includes a manifold inlet 218, a plurality of manifold outlets 219, and corresponding manifold valves 220. The pre-mix unit 190, and in particular its inner gas risers 198, are preferably connected directly to a separate source of fuel gas (e.g., from the overall furnace gas header). Risers 198 are typically interconnected by pipes 220 that connect to a separate source of fuel gas. A valve 222 is provided inside the tube 220 for controlling the flow rate of the fuel gas through the tube. Connecting the premix unit 190 with a separate fuel source enables the premix unit 190 to operate at a fixed pressure while functioning as the primary combustor first component (primary). It also enables the flow rate of the fuel gas and air mixture exiting the pre-mix unit to be increased to a value such that injection of the main fuel gas through the gas circulation ports 70 is not required if this configuration is used. The pre-mix unit may also be connected to the combustor gas header 218 with only a single connector, if desired.
As shown in FIG. 9, the gas burner apparatus 10 can also include a conventional pilot 223 for igniting the primary fuel gas within the burner tile 50. The pilot assembly 223 includes an inner gas riser 226 connected to a source of fuel gas, a venturi mixer 228 connected to the inner gas riser, and a gas tip 230 (which includes one or more ports therein) connected to the venturi mixer. The gas tip 230 extends into the central opening 52 of the burner tile. A shroud 232 is provided around the gas tip to stabilize the pilot flame by adding additional air and protection to the flame to ensure proper stoichiometry. Air is drawn through the apertures in the hood 232 as shown by the arrows in fig. 9. The flame is released from the top of the shroud.
As mentioned above, the particular configuration of the gas burner apparatus 10, including the arrangement of the burner tile 50 and the first and second fuel gas injection means 160 and 162, can vary depending on the application. In most cases, both internal coanda surfaces 80 and external coanda surfaces 130 will be employed. Regardless of the particular configuration employed, the objective is to mix a large amount of flue gas with the fuel gas and air without adversely affecting flame stability. The coanda surfaces allow the use of new tools to entrain and mix flue gas, shape the flame and output gas. The enhanced mixing caused by the coanda surfaces improves the heat flux, flame quality, and the amount of heat released to the furnace floor (flux). The staged fuel and the second combustion zone are used to reduce nitrogen oxide emissions and shape the flame. The compact gas diameter can now be applied by using the appropriate surface curvature to obtain the necessary or desired flame shape. The stabilizing mechanism of the coanda surfaces allows the burner to be successfully pilot at very low fuel flow rates. This design also allows the diffusion primary tip to be positioned slightly deeper within the furnace, thereby lengthening the entrainment length. Previous designs did not allow for longer entrainment lengths without creating instability. The use of a coanda surface allows the inner boundary layer to remain rich enough to remain flammable. The addition of a lean premixing ring or distribution header allows diffusion of the main fuel flame by low NOxHomogeneous flame inletAnd (5) one-step stabilization. The premixed flame allows the burner turndown capability to be exceeded by the typical design without creating instability. It also makes the burner stable when instability has occurred in the other burner. The combination of the above geometries enables the burner designer to design a medium NO on the basis of the same basic burner configurationxLow NO contentxOr very low NOxThe burner of (1). The stability of the burner is almost entirely superior to typical natural or forced air process burners, which enables the coanda surfaces to add additional flue gas to the primary flame zone. The turndown capability of the burner can now exceed 10 to 1 depending on the fuel and the operating parameters of the burner.
The overall size of the gas burner apparatus, which generally includes the size of the burner tile 50, may also vary depending on the manner in which the apparatus is used. Also, as mentioned above, the shape, size, length, height and orientation of the internal and external coanda surfaces can be adjusted as desired, provided that certain other parameters (e.g., sufficient curvature) are maintained to produce a sufficient coanda effect.
In some applications, the burner tile 50 may be retrofitted to an existing burner plenum. For example, the burner tile 50 may be retrofitted to a gas burner apparatus having a staged gas design. The burner tile 50 allows the addition of new tips and risers that utilize the coanda method, thereby reducing emissions and improving flame stability. Nitrogen oxides in the hot blast furnace can be reduced at the same time as the reduction of carbon monoxide in the cold box or during start-up.
The present invention also includes a coanda gas tip as shown in FIGS. 22 and 23. For example, the tip may be used as a primary fuel gas discharge nozzle 168 or a central venturi mixer 176 connected to a central gas gun 170 (e.g., a round tip). It may also be used as first and second fuel gas discharge nozzles, or pilot gas tips 230. FIG. 22 depicts the use of a coanda gas tip as a pilot gas tip.
The coanda gas tip of the present invention, generally designated 240 in FIGS. 22 and 23, comprises a gas pipe 242 for connection to a source of fuel gas (e.g., a gas riser), a gas deflector 244 attached to the gas pipe, and a fuel gas outlet 246 disposed between the gas pipe and the gas deflector. The gas deflector 244 is attached to the gas pipe 242 with an internally threaded connection 248 (other mechanical or welded connections may also be used). The gas deflector 244 has an outer surface that includes a coanda surface 250 positioned in correspondence with the fuel gas outlet 246 so that fuel gas discharged from the fuel gas outlet follows the path of the coanda surface. The gas deflector 244 of the coanda gas tip 240 preferably has a tulip shape that provides the deflector with an annular coanda surface 250.
To produce an effective coanda effect, the surface of the coanda surface 250 should be substantially smooth and have a substantially uniform radius or the same arc. Also, it is important for the external coanda surfaces 250 to have sufficient curvature to adequately attract the gas stream at the split. If the coanda surface does not have sufficient curvature or surface area, the surface will not have sufficient surface area to initiate the coanda effect caused by the momentum of the gas (i.e., the gas stream will not be attracted to the surface). To ensure a sufficient coanda effect, the ratio of the port diameter of the fuel gas outlet 246 (if a port is used), or the slot width of the fuel gas outlet 246 (if a slot is used) (if multiple ports or slots are used, the average port diameter or the average slot width) ("tip discharge port diameter") to the radius of the coanda surface 250 ("tip coanda radius") must be at least 7: 1. Preferably, the ratio of the tip discharge opening diameter to the tip coanda radius is at least 10: 1, most preferably at least 12: 1. Assuming that the coanda surface 250 has sufficient curvature or surface area, even for small gas ports, the gas flow or jet is aligned tangential to the curvature of the coanda surface to initiate the proper coanda effect.
In one embodiment, the fuel gas outlet 246 includes an annular seam 252 that releases fuel gas from the gas tube 242 at an appropriate angle (e.g., 0 to 45 °) depending on the particular application. The fuel gas outlet 246 may also include a plurality of small circular ports (not shown) in place of or in addition to the slots 252. As shown in FIG. 22, in pilot applications and other applications where flame stability is a concern or where enhanced mixing is desired, a shroud 254 may be mounted on the gas tube 242 to encase the deflector 244 and the outlet 246. The shroud 254 includes one or more air inlets 260.
The annular coanda surface 250 of the coanda gas tip 240 is positioned to correspond to the fuel gas outlet 246 so that the fuel gas discharged from the fuel gas outlet flows along the coanda surface. The coanda surfaces spread the fuel gas into a thin film, entraining more air or flue gas or both into the fuel gas stream and rapidly creating a mixture of the three fluids, forming a fuel-rich inner boundary layer of increased stability. The method can stabilize the flame of main body and solve the problem of incombustibility. The amount of flue gas entrained into the fuel gas stream can be suitably increased without affecting stability. The overall size of the coanda gas tip 240, including the length and diameter of the gas pipe 242 and the size of the deflector 244, can vary depending on the overall burner size and the manner in which the tip is used. For example, the tip may be relatively larger when used as the rounded tip 168 of the center air gun 170 than when used as the pilot tip 230. Smaller sized tips are typically used when generating heat release amounts of about 0.05 to about 1.5 MMBtuh. Larger sized tips can be used to deliver more fuel gas, such as when the tip is used as a primary injector in the center of a burner tile (the tip of the central air gun 170). In this case, the tip can deliver, for example, 3 to 10 million MMBtuh or more fuel gas, and more fuel gas if required by a particular application. The cone or other redundant components typically used in air guns are not necessary.
Referring to fig. 1, the operation of the gas burner apparatus 10 of the present invention will now be described. The device 10 is initially ignited with an internal pilot or manually pilot with an external torch. Once main pre-mix unit 190 is ignited, warmed up, and burned, each manifold valve 220 is opened to supply fuel gas to the remaining combustion components. Air is introduced into the burner housing 22 through the air inlet 32. An air regulator or damper 42 regulates the flow rate of air into the housing 22. Air passes through the housing 22 and enters the central opening 52 of the burner tile 50 through its air outlet 30.
The mixture of primary fuel and air is introduced into the central opening 52 of the burner tile 50 by the pre-mix unit 190. The fuel gas-air mixture exits through the premix gas ports 194 that surround the inner surface 66 of the burner tile wall 58. The primary fuel gas is also injected into the central opening 52 of the burner tile 50 by a central gas gun 170. The arrows in the drawing indicate the flow of fuel gas and combustion air. Simultaneously, primary fuel gas passes through the outer gas risers 164, through the primary fuel gas discharge nozzles 166 into and through the gas circulation ports 70. The fuel gas jet entering the gas circulation port 70 from the first fuel gas discharge nozzle 166 entrains the furnace flue gas into the central opening 52 of the burner tile 50. The primary fuel gas and flue gas flowing through the ports 70 encounter the internal coanda surfaces 80 and follow their path to the burner tile tip 56. As described above, the internal coanda surfaces 80 provide for rapid mixing of the fuel gas and flue gas together and for the mixture to remain in close proximity to the interior surface 66 of the wall 58 of the burner tile 50, which allows for a significant amount of flue gas to be entrained into the central opening to control the flame temperature and thereby control the emission of nitrogen oxides and carbon monoxide without unduly diluting the fuel gas within the central opening 52 (e.g., to an incombustible point). The primary fuel gas, air, and flue gas are ignited by the pre-mix unit 190 (or other pilot means) within the central bore 52, released by the exhaust 60, and combusted within the primary reaction zone 270. The primary reaction zone 270 is inside the central opening 52 of the burner tile 50 and outside the burner tile adjacent the discharge opening 60.
The secondary stage fuel gas is simultaneously transported by the outer gas risers 164 and discharged through the secondary fuel gas discharge nozzles 168 (which may also be primary fuel gas discharge nozzles) onto or near the continuous external coanda surface 130. The secondary stage fuel gas follows the path of the external coanda surface 130 to the burner tile tip 56 where it is ignited by the flame in the primary combustion zone and combusts in a secondary combustion zone 280 around and above the primary combustion zone. The flow of fuel gas and flue gas relative to the internal and external coanda surfaces 80 and 130 is best shown in FIGS. 4 and 4A. Figure 4A illustrates the flow of gas when the circulation choke means 87 is used to reduce the outflow of fluid through the gas circulation port 70.
As shown in FIG. 8, the central venturi mixer 176 may replace the central air gun 170 as a flame quenching mechanism, thereby reducing nitrous oxide emissions and producing a shorter flame. As shown in fig. 9, a plurality of inner gas risers 167 and corresponding fuel gas discharge nozzles 168 may be used in place of or in conjunction with the premixing unit 190. A recirculation restriction is typically required when the inner gas standpipe 167 and nozzles 168 are positioned near the gas recirculation ports 70 and diffused fuel gas is not injected through these ports. As shown in FIGS. 11-16, various configurations of the wall 58 and the outer surface 68 (e.g., multiple external coanda surfaces 130 separated by multiple inclined external flats 132 or one continuous external flat 132) can be employed to achieve a smaller diameter flame and help control the flame. As shown in fig. 16-19, a tip 140 may be included in the burner tile 50 to provide further mixing and stability of the bluff body. Finally, different shapes of the gas burner apparatus 10 may be employed to suit particular applications.
The fuel gas is combusted in the furnace space 14 at a flow rate that produces the desired amount of heat release. Air is introduced into the enclosure 22 through the air inlet 32 and the air regulator or damper 42 at a rate to achieve a desired stoichiometric mixture of fuel gas and air in the furnace space 14. That is, air is introduced therein at a flow rate proportional to the total flow rate of fuel gas introduced into the furnace space 14, which results in a fuel-air ratio greater than the stoichiometric ratio. Preferably, the air ratio is in the range of about 10% to about 25% above the stoichiometric ratio. The flue gas formed by combustion of the fuel gas in the furnace space 14 has a very low content of nitrogen oxides. The portion of the fuel gas used as the main fuel gas typically comprises from about 5% to about 25% by volume of the total fuel gas entering the furnace space 14 from the burner assembly 10. That is, the flow rate of the primary fuel gas into the furnace space is about 5% to about 25% of the total fuel gas flow rate delivered to the burner apparatus 10, while the flow rate of the secondary stage fuel gas is about 95% to about 75% of the total fuel gas flow rate. The primary fuel gas is mixed with the flue gas at a value in the range of about 1 to about 30 volumes of flue gas per unit volume of primary fuel gas, depending on the effective pressure, entrainment length, and size of the gas circulation ports 70. The staging gas can be biased to almost any percentage between the first port and the staging port of the staging riser to optimize heat flux. The heat release of the burner will be distributed to most of the openings between the different risers.
In the preferred embodiment, both internal coanda surfaces 80 and external coanda surfaces 130 are utilized. The primary fuel gas injection means includes an outer gas standpipe 164 and a premixing unit 190. That is, the primary fuel gas is injected into the burner tile 50 through the gas circulation port 70 and above the pre-mix unit 190. In another preferred embodiment, both internal coanda surfaces 80 and external coanda surfaces 130 are utilized. However, the first fuel gas injection device may be composed of only the premixing unit 190. That is, the only source of primary fuel gas is the premix unit 190. Even if the primary fuel gas is not injected through the gas circulation ports, the fuel gas and air exiting the pre-mix unit 190 and the air flow through the central bore 52 will still entrain flue gas flowing into the gas circulation ports into the central bore. Flue gas entrained by the air flow through the burner will still flow through the circulation ports in the burner tile, after which most of the flue gas will adhere to the internal coanda surfaces.
The present invention also provides a method of combusting a mixture of air and fuel gas containing flue gas in a furnace. The method comprises the following steps:
first, the gas burner apparatus of the present invention is installed through a wall of the furnace space, preferably the bottom wall or bottom wall of the furnace space. As mentioned above, a plurality of gas circulation ports 70 extend through the wall 58 of the burner tile 50. The inner surface 66 of the wall 58 includes a plurality of internal coanda surfaces 80 each proximate the gas circulation port 70. The gas burner apparatus 10 may also include one or more of the other components described above, depending on the application.
Air is injected into the central opening 52 of the burner tile 50. The primary fuel gas passes through the gas circulation ports 70 on or near the internal coanda surfaces 80 and entrains flue gas outside the wall 58 (e.g., the furnace space) into the central opening 52 of the burner tile 50 and forms a uniform mixture of air, fuel gas and flue gas within the central opening. The mixture of air, fuel gas and flue gas is discharged from the discharge opening 60 at the top end 56 of the burner tile 50 into the furnace space 14 where it is combusted while being diluted with a large amount of flue gas.
In another embodiment, a method of combusting an air and fuel gas mixture in the presence of furnace flue gas to generate heat within a furnace comprises the steps of:
the gas burner 10 of the present invention is installed through a wall of the furnace space 14, preferably the bottom wall or bottom wall of the furnace space 14. The exterior surface 68 of the wall 58 of the burner tile 50 includes an external coanda surface 130 extending outwardly therefrom.
Air and fuel gas are injected into the central opening 52 of the burner tile 50, thereby forming a mixture of air and fuel gas within the central opening. The air and fuel gas mixture then enters the furnace space 14 from the discharge opening 60 of the burner tile 50 and is combusted within the primary reaction zone 270 in the furnace space. The staged fuel gas is also injected on or near the external coanda surface 130 in a manner to entrain flue gas from the furnace space 14 to obtain a staged fuel gas/flue gas mixture and combust it in a second reaction zone 280 in the furnace space.
The steps of the above-described method may constitute a single method, if desired.
To further illustrate the present invention, the following examples are provided. Examples of the present invention
The gas burner apparatus 10 of the present invention was subjected to performance testing. The internal coanda surfaces 80 and the continuous coanda surfaces 130 are formed on the wall 58 of the burner tile 50. The first fuel gas injection means within the particular combustor configuration being tested includes outer gas risers 164 and fuel gas discharge nozzles 166. The fuel gas discharge nozzle includes ports for injecting primary fuel gas through the gas circulation ports 80 and ports for injecting secondary fuel gas onto or near the external coanda surface 130. A pre-mix unit 190 is also employed to reduce nox emissions. The premix baffle 192 includes 36 premix gas ports 194 having a diameter of 0.261 inches. These ports are spaced around the top surface of premix baffle 192. One 0.125 inch port is centered on each 0.261 inch port, or the 0.261 inch port may be a counterbore with a 0.125 inch port superimposed above it. The purpose of the small port is to act as a firing port in combination with the large port. The inner gas riser 167, the central gas gun 170, and the central venturi mixer 176 are all unused. Generally, the gas burner apparatus 10 being tested is constructed similar to the gas burner apparatus 10 shown in FIGS. 1-7, except that the center air gun 170 is not included.
The premix unit is manually ignited, and other components immediately following the burner are also ignited. The regulator 42 is fully open at all test points. The main premixing unit is precisely ignited, and a group of uniform small blue fire tongues are formed on the inner periphery of the burner tile. The main portion of the burner is then ignited at a pressure of about 0.1 psig. The heat release of the burner was then increased to about 0.84MMBtuh and the furnace was started to heat. The flame is very rigid and appears to be very stable. Carbon monoxide and nitrogen oxide levels were very good at all test points, maintaining a recordable emissions of less than 26ppmv (avg) from light-off to saturation. Redness of the burner tile 50 was observed throughout the testing period.
The following test data were obtained. Test data
| Heat release amount | 0.85MMBtuh |
| Pressure at the end | 0.4psig |
| Fuel gas | 100％TNG* |
| Tip size | #52MTD |
| Premixed gas | |
| NOxDischarge capacity | 5.31ppmv |
| CO emission amount | 34.80ppmv |
| O2 percent | 18.63％ |
| Quality of flame | Is very good |
| Type of mixer | Std.Brnr.Pilot |
| Premix end (big mouth) | 0.261” |
| Premix end (Small opening) | 0.125” |
| Temperature of furnace bottom | 336°F |
| Furnace temperature | 384°F |
*Talsa natural gas
| Heat release amount | 2.07MMBtuh |
| Pressure at the end | 2.6psig |
| Fuel gas | 100％TNG* |
| Tip size | #52MTD |
| Premixed gas |
| NOxDischarge capacity | 11.2ppmv |
| CO emission amount | 9.04ppmv |
| O2 percent | 16.15 |
| Quality of flame | Is very good |
| Type of mixer | Std.Brnr.Pilot |
| Premix end (big mouth) | 0.261” |
| Premix end (Small opening) | 0.125” |
| Temperature of furnace bottom | 683°F |
| Furnace temperature | 717°F |
*Talsa natural gas
| Heat release amount | 3.0MMBtuh |
| Pressure at the end | 5.4psig |
| Fuel gas | 100％TNG* |
| Tip size | #52MTD |
| Premixed gas | |
| NOxDischarge capacity | 12.42ppmv |
| CO emission amount | 12.33ppmv |
| O2 percent | 14.38％ |
| Quality of flame | Is very good |
| Type of mixer | Std.Brnr.Pilot |
| Premix end (big mouth) | 0.261” |
| Premix end (Small opening) | 0.125” |
| Temperature of furnace bottom | 859°F |
| Furnace temperature | 893°F |
*Talsa natural gas
| Heat release amount | 4.00MMBtuh |
| Pressure at the end | 9.4psig |
| Fuel gas | 100％TNG* |
| Tip size | #52MTD |
| Premixed gas | |
| NOxDischarge capacity | 10.19ppmv |
| CO emission amount | 26.62ppmv |
| O2 percent | 12.56％ |
| Quality of flame | Is very good |
| Type of mixer | Std.Brnr.Pilot |
| Premix end (big mouth) | 0.261” |
| Premix end (Small opening) | 0.125” |
| Temperature of furnace bottom | 1015℉ |
| Furnace temperature | 1036℉ |
*Talsa natural gas
| Heat release amount | 4.97MMBtuh |
| Pressure at the end | 15.3psig |
| Fuel gas | 85％TNG*And 15% H2 |
| Tip size | #52MTD |
| Premixed gas | |
| NOxDischarge capacity | 9.95ppmv |
| CO emission amount | 10.99ppmv |
| O2 percent | 10.22％ |
| Quality of flame | Is very good |
| Type of mixer | Std.Brnr.Pilot |
| Premix end (Large)Mouth) | 0.261” |
| Premix end (Small opening) | 0.125” |
| Temperature of furnace bottom | 1138℉ |
| Furnace temperature | 1161℉ |
*Talsa natural gas
| Heat release amount | 6.01MMBtuh |
| Pressure at the end | 20.9psig |
| Fuel gas | 85％TNG*/15％H2 |
| Tip size | #52MTD |
| Premixed gas | |
| NOxDischarge capacity | 10.74ppmv |
| CO emission amount | 9.30ppmv |
| O2 percent | 8.12％ |
| Quality of flame | Is very good |
| Type of mixer | Std.Brnr.Pilot |
| Premix end (big mouth) | 0.261” |
| Premix end (Small opening) | 0.125” |
| Temperature of furnace bottom | 1216℉ |
| Furnace temperature | 1256℉ |
*Talsa natural gas
| Heat release amount | 6.50MMBtuh |
| Pressure at the end | 23.6psig |
| Fuel gas | 85％TNG*/15％H2 |
| Tip size | #52MTD |
| Premixed gas | |
| NOxDischarge capacity | 12.99ppmv |
| CO emission amount | 1.10ppmv |
| O2 percent | 7.01％ |
| Quality of flame | Is very good |
| Type of mixer | Std.Brnr.Pilot |
| Premix end (big mouth) | 0.261” |
| Premix end (Small opening) | 0.125” |
| Temperature of furnace bottom | 1242℉ |
| Furnace temperature | 1322℉ |
*Talsa natural gas
| Heat release amount | 7.04MMBtuh |
| Pressure at the end | 26.7psig |
| Fuel gas | 85％TNG*/15％H2 |
| Tip size | #52MTD |
| Premixed gas | |
| NOxDischarge capacity | 13.66ppmv |
| CO emission amount | 0.00ppmv |
| O2 percent | 5.63％ |
| Quality of flame | Is very good |
| Type of mixer | Std.Brnr.Pilot |
| Premix end (big mouth) | 0.261” |
| Premix end (Small opening) | 0.125” |
| Temperature of furnace bottom | 1271℉ |
| Furnace temperature | 1367℉ |
*Talsa natural gas
| Heat release amount | 7.28MMBtuh |
| Pressure at the end | 28.1psig |
| Fuel gas | 85％TNG*/15％H2 |
| Tip size | #52MTD |
| Premixed gas | |
| NOxDischarge capacity | 13.37ppmv |
| CO emission amount | 0.00ppmv |
| O2 percent | 4.68％ |
| Quality of flame | Is very good |
| Type of mixer | Std.Brnr.Pilot |
| Premix end (big mouth) | 0.261” |
| Premix end (Small opening) | 0.125” |
| Temperature of furnace bottom | 1283℉ |
| Furnace temperature | 1376℉ |
*Talsa natural gas
| Heat release amount | 7.98MMBtuh |
| Pressure at the end | 31.9psig |
| Fuel gas | 85％TNG*/15％H2 |
| Tip size | #52MTD |
| Premixed gas | |
| NOxDischarge capacity | 11.32ppmv |
| CO emission amount | 0.00ppmv |
| O2 percent | 2.56％ |
| Flame articleQuality of food | Is very good |
| Type of mixer | Std.Brnr.Pilot |
| Premix end (big mouth) | 0.261” |
| Premix end (Small opening) | 0.125” |
| Temperature of furnace bottom | 1294℉ |
| Furnace temperature | 1469℉ |
*Talsa natural gas
| Heat release amount | 8.10MMBtuh |
| Pressure at the end | 32.4psig |
| Fuel gas | 85％TNG*/15％H2 |
| Tip size | #52MTD |
| Premixed gas | |
| NOxDischarge capacity | 10.82ppmv |
| CO emission amount | 0.00ppmv |
| O2 percent | 1.93％ |
| Quality of flame | Is very good |
| Type of mixer | Std.Brnr.Pilot |
| Premix end (big mouth) | 0.261” |
| Premix end (Small opening) | 0.125” |
| Temperature of furnace bottom | 1286℉ |
| Furnace temperature | 1475℉ |
*Talsa natural gas
| Heat release amount | 8.33MMBtuh |
| Pressure at the end | 34.0psig |
| Fuel gas | 85％TNG*/15％H2 |
| Tip size | #52MTD |
| Premixed gas | |
| NOxDischarge capacity | 10.24ppmv |
| CO emission amount | 0.00ppmv |
| O2 percent | 2.08％ |
| Quality of flame | Is very good |
| Type of mixer | Std.Brnr.Pilot |
| Premix end (big mouth) | 0.261” |
| Premix end (Small opening) | 0.125” |
| Temperature of furnace bottom | 1282℉ |
| Furnace temperature | 1499℉ |
*Talsa natural gas
| Heat release amount | 8.58MMBtuh |
| Pressure at the end | 35.1psig |
| Fuel gas | 85％TNG*/15％H2 |
| Tip size | #52MTD |
| Premixed gas | |
| NOxDischarge capacity | 10.34ppmv |
| CO emission amount | 0.00ppmv |
| O2 percent | 0.67％ |
| Quality of flame | Is very good |
| Type of mixer | Std.Brnr.Pilot |
| Premix end (big mouth) | 0.261” |
| Premix end (Small opening) | 0.125” |
| Temperature of furnace bottom | 1282℉ |
| Furnace temperature | 1532℉ |
*Talsa natural gas
| Heat release amount | 8.62MMBtuh |
| Pressure at the end | 35.3psig |
| Fuel gas | 85％TNG*/15％H2 |
| Tip size | #52MTD |
| Premixed gas | |
| NOxDischarge capacity | 9.71ppmv |
| CO emission amount | 2.44ppmv |
| O2 percent | 0.37％ |
| Quality of flame | Is very good |
| Type of mixer | Std.Brnr.Pilot |
| Premix end (big mouth) | 0.261” |
| Premix end (Small opening) | 0.125” |
| Temperature of furnace bottom | 1284℉ |
| Furnace temperature | 1537℉ |
*Talsa natural gas
| Heat release amount | 8.65MMBtuh |
| Pressure at the end | 35.3psig |
| Fuel gas | 85％TNG*/15％H2 |
| Tip size | #52MTD |
| Premixed gas | |
| NOxDischarge capacity | 9.22ppmv |
| CO emission amount | 131.8ppmv |
| O2 percent | 0.15％ |
| Quality of flame | Good taste |
| Type of mixer | Std.Brnr.Pilot |
| Premix end (big mouth) | 0.261” |
| Premix end (Small opening) | 0.125” |
| Temperature of furnace bottom | 1283℉ |
| Furnace temperature | 1501℉ |
*Talsa natural gas
The performance of the gas burner device of the invention is therefore very good. The pre-mix unit 190 works well. Carbon monoxide is not observed for most of the time during ignition, warm-up and steady operation. The observed nitrogen oxide emissions are also very low.
Claims (59)
1. A gas burner apparatus for discharging a mixture of fuel gas and air to a furnace, wherein the mixture is combusted in the presence of flue gas while forming small amounts of nitrogen oxides, comprising:
a plenum comprising a housing for connection to the furnace, the housing comprising:
an upper end connected to the furnace, the upper end being provided with an air outlet in its interior;
a lower end opposite the upper end; and
a sidewall connecting the upper end and the lower end, wherein at least one of the sidewall and the lower end is provided with an air inlet therein;
a burner tile having a central opening therein for receiving air from said air outlet of said housing, said burner tile comprising:
a bottom end connected to the upper end of the housing and located above the air outlet;
a top end opposite the bottom end, the top end including a discharge outlet; and
a wall connecting said bottom end and said top end and surrounding said central bore, said wall extending into said furnace and having an inner surface, an outer surface and at least one gas circulation port extending through said wall, said inner surface of said wall including an internal coanda surface projecting into said central bore for enhancing mixing of flue gas and primary fuel gas therein;
first fuel gas injection means connected to a source of fuel gas and operatively associated with said burner means for injecting primary fuel gas into said central opening of said burner tile; and
second fuel gas injection means connected to a source of fuel gas and operatively associated with said burner means for injecting a second stage fuel gas from outside said burner tile to a point adjacent said discharge outlet of said burner tile.
2. A gas burner apparatus as in claim 1, wherein the internal coanda surfaces are disposed on the inner surface of the wall adjacent the gas circulation port.
3. A gas burner apparatus as in claim 1, wherein said combustion air inlet is provided in said side wall of said housing.
4. The gas burner apparatus of claim 1 wherein the primary fuel gas injection means comprises an outer gas riser connected to the source of fuel gas, the outer gas riser having an outer primary fuel gas discharge nozzle connected thereto and disposed outside of the wall of the burner tile to inject primary fuel gas through the gas circulation port and onto or adjacent the internal coanda surface.
5. A gas burner apparatus as in claim 1, wherein said first fuel gas injection means comprises an inner gas riser connected to said source of fuel gas and disposed inside said housing, said inner gas riser having an inner first fuel gas discharge nozzle connected thereto for injecting primary fuel gas into said central opening of said burner tile.
6. A gas burner apparatus as in claim 1, wherein said first fuel gas injection means comprises an inner gas riser connected to said fuel gas source and disposed inside said housing, said inner gas riser having an inner first fuel gas discharge nozzle connected thereto and a venturi housing operatively associated therewith for injecting a primary fuel gas and air mixture into said central opening of said burner tile.
7. A gas burner apparatus as claimed in claim 1, wherein said first fuel gas injection means includes a premixing unit including:
a premix baffle extending around the inner surface of said wall of said burner tile and located below said gas circulation ports while having a plurality of premix gas ports at the top thereof;
a venturi mixer, comprising:
an inner gas standpipe connected to said fuel gas source and having an inner first fuel gas discharge nozzle connected thereto; and
a venturi housing operatively associated with the inner gas riser and the first fuel gas discharge nozzle and connected to the premixing partition for supplying a primary fuel gas and air mixture into the premixing partition.
8. A gas burner apparatus as in claim 1, wherein said burner tile further comprises a circulation choke means disposed within said gas circulation port for inhibiting the flow of fluid from within said central opening of said burner tile through said gas circulation port.
9. A gas burner apparatus as claimed in claim 8, wherein said circulation choke means comprises a baffle plate attached to said wall of said burner tile and positioned below said gas circulation ports and extending upwardly into said gas circulation ports.
10. A gas burner apparatus as in claim 1, wherein the interior surface of the wall of the burner tile includes a recessed section, the gas circulation port and the internal coanda surface being disposed within the recessed section.
11. A gas burner apparatus as in claim 10, wherein the recessed section comprises opposed side walls extending from the interior surface into the central opening of the burner tile, the opposed side walls extending further into the central opening than the internal coanda surface.
12. A gas burner apparatus as in claim 1, wherein said wall of said burner tile includes a plurality of gas circulation ports extending through said wall.
13. The gas burner apparatus of claim 12, wherein the interior surface comprises a plurality of internal coanda surfaces, each of the internal coanda surfaces projecting into the central opening of the burner tile.
14. A gas burner apparatus as in claim 13, wherein said interior surface of said wall of said burner tile includes a plurality of recessed sections, each of said recessed sections having a gas circulation port and an internal coanda surface disposed therein.
15. A gas burner apparatus as in claim 14, wherein each of the recessed sections includes opposed side walls extending from the interior surface into the central opening of the burner tile, the opposed side walls extending further into the central opening than do interior coanda surfaces disposed within the recessed sections.
16. A gas burner apparatus as in claim 1, further comprising a pilot means for igniting said burner connected to said source of fuel gas and extending into said central opening of said burner tile.
17. A gas burner apparatus as in claim 16, wherein the pilot means comprises a gas riser and a gas tip having one or more gas ports therein.
18. A gas burner apparatus as in claim 17, wherein the gas tip comprises a gas tube connected to the riser, a gas deflector connected to the gas tube, and a fuel gas outlet disposed between the gas tube and the gas deflector, the gas deflector having an outer surface comprising a coanda surface disposed opposite the fuel gas outlet to cause fuel gas discharged from the fuel gas outlet to flow along a path of the coanda surface.
19. A gas burner apparatus as claimed in claim 1, wherein said secondary fuel gas injection means comprises an outer gas riser connected to said source of fuel gas and having a secondary fuel gas discharge nozzle connected thereto for injecting secondary stage fuel gas onto or adjacent said outer surface of said wall of said burner tile.
20. A gas burner apparatus as in claim 19, wherein said exterior surface of said wall of said burner tile includes an external coanda surface projecting outwardly therefrom for enhancing mixing of flue gas and a second stage fuel gas thereabout.
21. The gas burner apparatus of claim 20 wherein the exterior surface of the wall of the burner tile includes a plurality of external coanda surfaces each projecting outwardly therefrom and the secondary fuel gas injection means comprises a plurality of external gas risers each connected to a source of the fuel gas and having a secondary fuel gas discharge nozzle thereon for injecting secondary stage fuel gas onto or adjacent to one of the external coanda surfaces.
22. The gas burner apparatus of claim 20 wherein the external coanda surface extends around the entire outer surface of the wall of the burner tile and the secondary fuel gas injection means comprises a plurality of external gas risers each connected to the source of fuel gas and having a secondary fuel gas discharge nozzle thereon for injecting secondary stage fuel gas onto or adjacent to the external coanda surface.
23. The gas burner apparatus of claim 1 wherein the first fuel gas injection means comprises an outer gas riser connected to the source of fuel gas and disposed outside the wall of the burner tile, the outer gas riser having a first fuel gas discharge nozzle connected thereto and disposed outside the gas circulation port for injecting primary fuel gas through the gas circulation port and onto or adjacent the internal coanda surface, and the second fuel gas injection means comprises the outer gas riser of the first fuel gas injection means and a second fuel gas discharge nozzle connected to the riser for injecting secondary stage fuel gas onto or adjacent the outer surface of the wall of the burner tile.
24. A gas burner apparatus as in claim 1, wherein said burner tile has a substantially circular cross-sectional shape.
25. A gas burner apparatus as recited in claim 1, wherein said burner tile further includes a lip extending laterally from said interior surface of said wall into said central aperture, said lip being attached to said wall adjacent said top end of said burner tile and extending around said interior surface of said wall of said burner tile.
26. A gas burner apparatus as in claim 25, wherein the lip includes a lower end, a top end, and a body joining the lower end and the top end, the body including a plurality of projections extending into the central bore.
27. A gas burner apparatus for discharging a mixture of fuel gas and air to a furnace, wherein the mixture is combusted in the presence of flue gas while forming small amounts of nitrogen oxides, comprising:
a plenum comprising a housing for connection to the furnace, the housing comprising:
an upper end connected to the furnace, the upper end having an air outlet disposed therein;
a lower end opposite the upper end; and
a sidewall connecting the upper end and the lower end, wherein at least one of the sidewall and the lower end is provided with an air inlet therein;
a burner tile having a central opening therein for receiving air from said air outlet of said housing, said burner tile comprising:
a bottom end connected to the upper end of the housing and located above the air outlet;
a top end opposite the bottom end, the top end including a discharge outlet; and
a wall connecting said bottom end and said top end and surrounding said central opening, said wall extending into said furnace and having an inner surface and an outer surface, said outer surface of said wall including an external coanda surface projecting outwardly from said outer surface for enhancing mixing of flue gas and a second stage fuel gas thereabout;
first fuel gas injection means connected to a source of fuel gas and operatively associated with said burner means for injecting primary fuel gas into said central opening of said burner tile; and
secondary fuel gas injection means connected to a source of fuel gas and operatively associated with said burner means for injecting secondary stage fuel gas from outside said burner tile onto or adjacent said external coanda surface.
28. The gas burner apparatus of claim 27, wherein the secondary fuel gas injection means comprises an outer gas riser connected to the source of fuel gas and having a secondary fuel gas nozzle connected thereto for injecting secondary stage fuel gas onto or adjacent the external coanda surface.
29. The gas burner apparatus of claim 27 wherein said exterior surface of said wall of said burner tile includes a plurality of external coanda surfaces each projecting outwardly therefrom and said secondary fuel gas injection means comprises a plurality of external gas risers each connected to said fuel gas and having a secondary fuel gas nozzle connected thereto for injecting secondary stage fuel gas onto or adjacent one of said external coanda surfaces.
30. A gas burner apparatus as claimed in claim 27, wherein said external coanda surfaces extend around the entire outer surface of said wall of said burner tile and said secondary fuel gas injection means comprises a plurality of external gas risers each connected to a source of said fuel gas and having a secondary fuel gas nozzle connected thereto for injecting secondary stage fuel gas onto or adjacent to said external coanda surfaces.
31. A gas burner apparatus as in claim 27, wherein said wall of said burner tile includes at least one gas circulation port extending through said wall.
32. A gas burner apparatus as in claim 31, wherein said interior surface of said wall includes an internal coanda surface projecting into said central opening of said burner tile for enhancing mixing of flue gas and primary fuel gas therein.
33. A gas burner apparatus as in claim 32, wherein the internal coanda surfaces are disposed on the inner surface of the wall adjacent the gas circulation port.
34. A gas burner apparatus as claimed in claim 33, wherein said primary fuel gas injection means comprises an outer gas riser connected to said source of fuel gas, said outer gas riser having an outer primary fuel gas nozzle connected thereto and disposed outwardly of said wall of said burner tile for injecting primary fuel gas through said gas circulation ports and onto or adjacent said internal coanda surface.
35. A gas burner apparatus for discharging a mixture of fuel gas and air to a furnace, wherein the mixture is combusted in the presence of flue gas while forming small amounts of nitrogen oxides, comprising:
a plenum comprising a housing for connection to the furnace, the housing comprising:
an upper end connected to the furnace, the upper end having an air outlet disposed therein;
a lower end opposite the upper end; and
a sidewall connecting the upper end and the lower end, wherein at least one of the sidewall and the lower end is provided with an air inlet therein;
a burner tile having a central opening therein for receiving air from said air outlet of said housing, said burner tile comprising:
a bottom end connected to the upper end of the housing and located above the air outlet;
a top end opposite the bottom end, the top end including a discharge outlet; and
a wall connecting said bottom end and said top end and surrounding said central opening, said wall extending into said furnace and having an inner surface, an outer surface and at least one gas circulation port extending through said wall, said inner surface of said wall including an internal coanda surface projecting into said central opening for enhancing mixing of flue gas and primary fuel gas therein, said outer surface of said wall including an external coanda surface projecting outwardly from said outer surface for enhancing mixing of flue gas and secondary stage fuel gas thereabout;
first fuel gas injection means connected to a source of fuel gas and operatively associated with said burner means for injecting primary fuel gas into said central opening of said burner tile; and
secondary fuel gas injection means connected to a source of fuel gas and operatively associated with said burner means for injecting secondary stage fuel gas from outside said burner tile onto or adjacent said external coanda surface.
36. A gas burner apparatus as in claim 35, wherein the internal coanda surfaces are disposed on the inner surface of the wall adjacent the gas circulation ports.
37. A gas burner apparatus as claimed in claim 35, wherein said primary fuel gas injection means comprises an outer gas riser connected to said source of fuel gas, said outer gas riser having an outer primary fuel gas nozzle connected thereto and disposed outwardly of said wall of said burner tile for injecting primary fuel gas through said gas circulation port and onto or adjacent said internal coanda surface.
38. The gas burner apparatus of claim 35, wherein the secondary fuel gas injection means comprises an outer gas riser connected to the source of fuel gas and having a secondary fuel gas nozzle connected thereto for injecting secondary stage fuel gas onto or adjacent the external coanda surface.
39. A gas burner apparatus as in claim 38, wherein said secondary fuel gas injection means comprises said outer gas riser of said primary fuel gas injection means and a secondary fuel gas discharge nozzle connected to said riser for injecting a secondary stage fuel gas onto or adjacent to said external coanda surface.
40. A gas burner apparatus for discharging a mixture of fuel gas and air to a furnace, wherein the mixture is combusted in the presence of flue gas while forming small amounts of nitrogen oxides, comprising:
a housing for connection to the furnace, the housing comprising:
an upper end connected to the furnace, the upper end having an air outlet disposed therein;
a lower end opposite the upper end; and
a sidewall connecting the upper end and the lower end, wherein at least one of the sidewall and the lower end is provided with an air inlet therein;
a burner tile having a central opening therein for receiving air from said air outlet of said housing, said burner tile comprising:
a bottom end connected to the upper end of the housing and located above the air outlet;
a top end opposite the bottom end, the top end including a discharge outlet; and
a wall connecting said bottom end and said top end and surrounding said central bore, said wall extending into said furnace and having an inner surface, an outer surface and at least one gas circulation port extending through said wall, said inner surface of said wall including an internal coanda surface projecting into said central bore for enhancing mixing of flue gas and primary fuel gas therein;
first fuel gas injection means connected to a source of fuel gas and operatively associated with said burner means for injecting primary fuel gas into said central opening of said burner tile, said first fuel gas injection means comprising a premixing unit comprising:
a premix baffle extending around the inner surface of said wall of said burner tile and located below said gas circulation ports while having a plurality of premix gas ports at the top thereof; and
a venturi mixer comprising an inner gas riser connected to said source of fuel gas and having an inner first fuel gas discharge nozzle connected thereto, and a venturi housing operatively associated with said inner gas riser and first fuel gas discharge nozzle and connected to said premixing partition for supplying a mixture of primary fuel gas and air to said premixing partition; and
second fuel gas injection means connected to a source of fuel gas and operatively associated with said burner means for injecting a second stage fuel gas from outside said burner tile to a point adjacent said discharge outlet of said burner tile.
41. A gas burner apparatus as in claim 40, wherein the burner tile further comprises a circulation choke means disposed within the gas circulation port for inhibiting the flow of fluid from within the central opening of the burner tile through the gas circulation port.
42. A gas burner apparatus as in claim 41, wherein said circulation choke means comprises a baffle plate attached to said wall of said burner tile and extending upwardly into said gas circulation port.
43. A burner tile for use in conjunction with a burner plenum and first fuel gas injection means to form a gas burner means for discharging a mixture of fuel gas and air to a furnace, wherein the mixture combusts in the presence of flue gas while generating a small amount of nitrogen oxides, wherein the burner plenum comprises a housing for connection to the furnace and including an upper end in which is disposed an air outlet, and wherein said first fuel gas injection means is connected to a source of fuel gas and is operatively associated with said gas burner means, said burner tile having a central aperture therein for receiving air from the plenum housing outlet and primary fuel gas from the first fuel gas injection means, and said burner tile further comprising:
a bottom end connected to an upper end of the plenum housing and positioned above an air outlet provided therein;
a top end opposite the bottom end, the top end including a discharge outlet; and
a wall connecting said bottom end and said top end and surrounding said central opening, said wall extending into said furnace and having an inner surface, an outer surface and at least one gas circulation port extending through said wall for receiving primary fuel gas and flue gas from the outside of said wall and directing said primary fuel gas and flue gas into said central opening, said inner surface of said wall including an internal coanda surface projecting into said central opening for enhancing mixing of the flue gas and primary fuel gas therein.
44. The burner tile of claim 43, wherein said internal coanda surfaces are disposed on said interior surface of said wall adjacent said gas circulation ports.
45. The burner tile of claim 44, wherein said interior surface of said wall of said burner tile includes a recessed section, and said gas circulation port and said internal coanda surface are disposed within said recessed section.
46. The burner tile of claim 45, wherein said recessed section comprises opposed side walls extending from said interior surface into said central opening of said burner tile, said opposed side walls extending further into said central opening than said internal coanda surface does.
47. A burner tile for use in conjunction with a burner plenum to form a gas burner apparatus for discharging a mixture of fuel gas and air to a furnace, wherein the mixture combusts in the presence of flue gas while generating a small amount of nitrogen oxides, wherein the burner plenum comprises a housing for connection to the furnace and including an upper end having an air outlet disposed therein, said burner tile having a central aperture for receiving air from the plenum housing outlet and comprising:
a bottom end connected to the upper end of the plenum housing and positioned above an air outlet provided therein;
a top end opposite the bottom end, the top end including a discharge outlet; and
a wall connecting said bottom end and said top end and surrounding said central bore, said wall extending into said furnace and having an inner surface and an outer surface, said outer surface of said wall including an external coanda surface projecting outwardly therefrom for enhancing mixing of flue gas and a second stage fuel gas thereabout.
48. The burner tile of claim 47, wherein said exterior surface of said wall of said burner tile includes a plurality of external coanda surfaces, each of said external coanda surfaces projecting outwardly from said exterior surface.
49. The burner tile of claim 48, wherein said external coanda surface extends around the entire exterior surface of said wall of said burner tile.
50. A burner tile for use in conjunction with a burner plenum and a first fuel gas injection means to form a gas burner means for discharging a mixture of fuel gas and air to a furnace, wherein the mixture combusts in the presence of flue gas while generating a small amount of nitrogen oxides, wherein the burner plenum comprises a housing for connection to the furnace and including an upper end in which an air outlet is disposed, and wherein the first fuel gas injection means is connected to a source of fuel gas and is operatively associated with the gas burner means, the burner tile having a central aperture for receiving air from the plenum housing outlet and primary fuel gas from the first fuel gas injection means, and the burner tile further comprising:
a bottom end connected to an upper end of the plenum housing and positioned above an air outlet provided therein;
a top end opposite the bottom end, the top end including a discharge outlet; and
a wall connecting said bottom end and said top end and surrounding said central bore, said wall extending into said furnace and having an inner surface, an outer surface and at least one gas circulation port extending through said wall for receiving primary fuel gas and flue gas from outside said wall and directing said primary fuel gas and flue gas into said central bore, said inner surface of said wall including an inner coanda surface projecting into said central bore for enhancing mixing of flue gas and primary fuel gas therein, said outer surface of said wall including an outer coanda surface projecting outwardly from said outer surface for enhancing mixing of flue gas and secondary stage fuel gas thereabout.
51. The burner tile of claim 50, wherein said wall of said burner tile includes a plurality of gas circulation ports extending through said wall.
52. The burner tile of claim 51, wherein said interior surface of said wall includes a plurality of internal coanda surfaces, each of said internal coanda surfaces projecting into said central opening of said burner tile.
53. The burner tile of claim 52, wherein said exterior surface of said wall of said burner tile includes a plurality of external coanda surfaces, each of said external coanda surfaces projecting outwardly from said exterior surface.
54. The burner tile of claim 52, wherein said external coanda surface extends around the entire exterior surface of said wall of said burner tile.
55. The burner tile of claim 54, wherein the tile is substantially circular in cross-section.
56. A method of combusting a mixture of air, fuel gas and flue gas within a furnace space of a furnace to generate heat within the furnace space, wherein a gas burner apparatus is employed having a mixing zone for mixing the air, fuel gas and flue gas prior to combustion, the method comprising:
providing a coanda surface within said mixing zone for enhancing mixing of flue gas and fuel gas therein;
injecting fuel gas onto or adjacent to the coanda surface in a manner that entrains flue gas from outside the mixing zone into the mixing zone and causes the flue gas to mix with the air and fuel gas in the mixing zone;
discharging the mixture of air, fuel gas and flue gas from the mixing zone to the furnace space; and
combusting the mixture of air, fuel gas and flue gas from the mixing zone within the furnace space.
57. The method of claim 56, wherein the mixing zone is surrounded by a wall, the mixture of air, fuel gas, and flue gas being discharged from the mixing zone to a primary reaction zone of the furnace space, and wherein the method further comprises the steps of:
providing an external coanda surface on said exterior surface of said wall for enhancing mixing of flue gas and fuel gas thereabout;
injecting a second staged fuel gas stream onto or adjacent to said external coanda surface in a manner that entrains flue gas into said second staged fuel gas stream to produce a second fuel gas/flue gas mixture and causes combustion of said second fuel gas/flue gas mixture in a second reaction zone of said furnace space.
58. A method of combusting a mixture of air, fuel gas and flue gas within a furnace space of a furnace to generate heat within the furnace space, wherein a gas burner apparatus is employed that includes a wall surrounding a mixing zone for mixing the air, fuel gas and flue gas prior to combustion, the method comprising:
providing a coanda surface on the exterior surface of the wall of the burner apparatus for enhancing mixing of the flue gas and the fuel gas thereabout;
injecting primary fuel gas into the mixing zone in a manner that the fuel gas mixes with air in the mixing zone;
discharging a mixture of air and fuel gas from the mixing zone;
combusting the air and fuel gas mixture discharged from the mixing zone in a first reaction zone of the furnace space;
injecting a second staged fuel gas stream onto or adjacent to said external coanda surface in a manner that entrains flue gas into said second staged fuel gas stream to produce a second fuel gas/flue gas mixture and causes combustion of said second fuel gas/flue gas mixture in a second reaction zone of said furnace space.
59. The method of claim 58 wherein the interior surface of the wall of the burner apparatus includes internal coanda surfaces for enhancing mixing of the flue gas and the fuel gas therein to inject the fuel gas injected into the mixing zone onto or adjacent to the internal coanda surfaces in a manner that entrains the flue gas from outside the mixing zone into the mixing zone and causes the flue gas to mix with the air and fuel gas in the mixing zone.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US11/454,071 | 2006-06-14 | ||
| US11/454,071 US7878798B2 (en) | 2006-06-14 | 2006-06-14 | Coanda gas burner apparatus and methods |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| HK1120100A1 HK1120100A1 (en) | 2009-03-20 |
| HK1120100B true HK1120100B (en) | 2011-11-25 |
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