Low NO x and CO burner method and apparatus

Abstract

Systems and methods for reducing NO at a stack by thoroughly mixing primary fuel with a specific range of excess combustion air X and / or CO emissions. The primary fuel-air mixture is then discharged and anchored in the combustion chamber of a burner. Additionally, the systems and methods also provide dynamic control of NO in emissions from a furnace by regulating the flow rates of primary fuel and secondary stage fuel and, in some cases, controlling the amount or arrangement of combustion air entering the furnace X content.

Description

[0001] This application is a divisional application of an application with an application date of September 5, 2018, an invention title of "Low NO X and CO Burner Methods and Apparatus", an international application number of PCT / IB2018 / 056780, and a Chinese national application number of 201880057140.9.

[0002] Cross - Reference to Related Applications

[0003] This application claims the benefit of U.S. Provisional Application No. 62 / 554,327, filed on September 5, 2017, and U.S. Provisional Application No. 62 / 690,185, filed on June 26, 2018, which are incorporated herein by reference. Technical Field

[0004] The present disclosure relates to burner devices and methods for combusting fuel - air mixtures, thereby producing flue gas having low NOx and CO. Background Art

[0005] Due to strict environmental emission standards adopted by government authorities and agencies, burner devices and methods have been developed heretofore that suppress the formation of nitrogen oxides (NOx) in the flue gas produced by combusting fuel - air mixtures. For example, burner devices and methods have been developed in which liquid or gaseous fuel is combusted in air at less than stoichiometric concentration to reduce the flame temperature and thereby reduce thermal NOx. That is, staged - air burner devices and methods have been developed in which fuel is combusted in an oxygen - deficient atmosphere in a first combustion zone, thereby creating a reducing environment that inhibits NOx formation, and the remaining air portion is introduced into a second zone downstream of the first zone, where the unburned remaining fuel is combusted.

[0006] Staged - fuel burner devices have also been developed, in which all of the combustion air is supplied and a portion of the fuel is combusted in a first zone, with most of the fuel being combusted in a second downstream zone. In such staged - fuel burner devices and methods, the second zone is diluted with heated furnace flue gas prior to mixing with the excess air from the first zone, thereby reducing the formation of thermal NOx.

[0007] Although staged - fuel burners that produce flue gas containing low levels of NOx have been utilized heretofore, there is still a need for improved burner devices with a greater operating range, thereby producing flue gas having consistently lower NOx and CO emission levels and improved methods of using the burner devices. Summary of the Invention

[0008] Embodiments of the present disclosure relate to systems and methods for controlling the NOx and / or CO content in emissions from a furnace. Generally, the emissions will be determined in the furnace stack. As used herein, "stack" or "furnace stack" includes any point downstream of the furnace combustion zone where the emissions and excess oxygen content of the flue gas can be measured. Typically, this point will be in the stack or outlet flue of the radiant section of the furnace, but in some embodiments may be an area within the furnace but outside the combustion zone, or may be an area just downstream of the furnace outlet flue.

[0009] Broadly speaking, emissions of NOx and / or CO in the stack can be reduced by thoroughly mixing the primary fuel with a specific range of excess combustion air prior to combustion, where the excess combustion air exceeds the amount required to chemically combust the primary fuel stoichiometrically, so as to minimize thermal and prompt NOx emissions. The primary fuel-air mixture is then discharged and anchored in the combustion chamber of the burner. Anchoring the primary fuel-air mixture flame in the combustion chamber of the device does not allow the heat generated by the flame to be immediately transferred to the surrounding furnace environment, but rather uses the heat generated with sufficient residence time in the combustion chamber to significantly minimize NOx and / or CO emissions. The NOx and CO levels caused by this configuration relatively decouple the emission performance of the primary flame from the flue gas environment around the furnace. For prior art combustion devices, the hotter the surrounding furnace environment, the higher the NOx and the lower the CO. Additionally, for prior art combustion devices, the colder the surrounding furnace environment, the lower the NOx and the higher the CO. The current embodiments avoid these problems.

[0010] More specifically, these problems are avoided by a method of discharging fuel and a quantity of air into the furnace space where the fuel is combusted such that flue gas having a low NOx content and a low CO content is thereby formed, the method comprising the steps of:

[0011] Mixing a first portion of the fuel and substantially all of the air to form a lean primary fuel-air mixture;

[0012] Discharging the lean primary fuel-air mixture into the furnace space within a primary combustion zone defined by a burner tile such that there is a furnace environment surrounding the burner tile;

[0013] Combusting the primary fuel-air mixture in the primary combustion zone to produce a flame and thereby produce flue gas, where the primary combustion zone has a first end and a second end, and introducing the lean primary fuel-air mixture such that the flame is anchored adjacent the first end and the resulting flue gas is discharged into the furnace environment at the second end.

[0014] In addition, these problems are avoided in a fuel gas burner device including a plenum chamber, a burner tile, a plurality of flame holders, a plurality of primary fuel nozzles, a plurality of primary tubes, and a plurality of secondary fuel nozzles.

[0015] The plenum chamber includes a first end attached to a heating furnace, a second end opposite the first end; and side walls connecting the first end and the second end together. At least one of the side walls and the second end has an air inlet disposed therein.

[0016] The burner tile includes a base attached to the upper end of the plenum chamber, a discharge end opposite the base, the discharge end defining a discharge outlet, and a wall connecting the base to the discharge end and surrounding the discharge outlet. The wall extends into the heating furnace and has an outer surface and an inner surface defining a primary combustion chamber.

[0017] A plurality of flame holders are located within the combustion chamber. A plurality of primary fuel nozzles extend into the plenum chamber. The primary tubes include a first portion. Each primary tube in the first portion has an inlet end located within the plenum chamber and a discharge end located within the primary combustion chamber. The first portion of the primary tube is associated with the plurality of primary fuel nozzles such that fuel from the primary fuel nozzles flows into the inlet end of the first portion of the primary tube and draws air from the inside of the plenum chamber into the inlet end so as to produce a fuel-air mixture. The discharge end is positioned relative to the flame holders such that the fuel-air mixture is introduced into the primary combustion chamber through the discharge end so as to encounter the flame holders.

[0018] In addition, the bottom end of the tile and the upper end of the plenum chamber are closed to the air flow such that air does not transfer from the plenum chamber to the tile except through one or more of the primary tubes.

[0019] A plurality of secondary fuel nozzles are connected to a fuel gas source and operatively associated with the burner device such that secondary stage fuel gas is injected from the outside of the burner tile at a point downstream of the discharge outlet of the burner tile.

[0020] Embodiments of the above methods and devices may also include systems and methods for dynamically controlling the NOx content in the emissions of a heating furnace incorporating the above methods and devices. Although these systems and methods may be used with other burners and burner operating methods not described above, they may be particularly effective when used with the above methods and devices.

[0021] Systems and methods for regulating changes in a furnace system that result in changes in NOx and CO emissions. In many applications, the fuel composition can vary during the operation of a furnace. Due to the variation in fuel composition, there are variations in the emissions of NOx and CO. Additional variables that drive changes in NOx and CO emissions are combustion air conditions, such as the relative humidity in the air, and the flue gas temperature in the combustion chamber around the combustion flame. All of these conditions ultimately result in large variations in NOx and CO emissions.

[0022] Broadly speaking, these systems and methods for controlling emissions can include the following steps:

[0023] Determine the composition of the primary fuel and the secondary fuel;

[0024] Determine the flow rate of the primary fuel entering the system and the flow rate of the secondary fuel entering the system;

[0025] Determine the adiabatic flame temperature (first AFT) at which the primary fuel and the secondary fuel burn;

[0026] Based on the first AFT and the second AFT, determine the amount of excess air required to produce a predetermined amount of NOx; and;

[0027] Adjust at least one of the flow rate of the primary fuel, the flow rate of the secondary fuel, the primary amount of air based on the amount of excess air required to minimize NOx, and the distribution of air within the burner.

[0028] In some embodiments, the adjusting step is at least for both the flow rate of the primary fuel and the flow rate of the secondary fuel, and optionally, the adjustment is for both the flow rate of the primary fuel and the flow rate of the secondary fuel simultaneously.

[0029] The systems and methods can utilize sensors to determine the composition of the primary fuel and the secondary fuel, to measure the flow rates of the primary fuel and the secondary fuel. Additionally, sensors can be used to measure the flame temperature at various locations in the furnace or burner, and to measure the amounts of NOx, CO, and excess air in the furnace stack.

[0030] Various valves and actuators can be used to control the flow of fuel and air into the furnace. A computer processing system can be used to calculate the conditions of the furnace and the equipment, and more specifically for the burner. For example, the AFT can be calculated based on the fuel composition and the amount of air. Additionally, the target AFT for minimizing NOx can be calculated based on experimental curve data. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram for simplifying the conventional prior art flame anchoring in a burner tile.

[0032] Figure 2Schematic diagram of a simplified configuration according to the present disclosure, where the flame is anchored inside the combustion chamber (inside the burner tile).

[0033] Figure 3 Schematic diagram of a burner according to an embodiment of the present disclosure.

[0034] Figure 4 Schematic diagram of a burner according to a second embodiment of the present disclosure.

[0035] Figure 5 Schematic diagram of a heating furnace using a burner system according to a third embodiment.

[0036] Figure 6 Schematic diagram of a heating furnace using a burner system according to a fourth embodiment.

[0037] Figure 7 Schematic diagram of a heating furnace using a burner system according to another embodiment.

[0038] Figure 8 Schematically shows a possible arrangement of the staged fuel nozzles relative to the burner tile in the heating furnace wall.

[0039] Figure 9 Schematic top view of a burner system, which shows an embodiment of the tube arrangement inside the burner tile.

[0040] Figure 10 Schematic top view of a burner system, which shows another embodiment of the tube arrangement inside the burner tile.

[0041] Figure 11 Schematic diagram of an ignition unit according to an embodiment of the present disclosure suitable for use with a burner system.

[0042] Figure 12 For Figure 11 Schematic diagram of an embodiment of a suitable nozzle in the ignition unit.

[0043] Figure 13 For Figure 11 Schematic diagram of a second embodiment of a suitable nozzle in the ignition unit.

[0044] Figure 14 For Figure 11 Schematic diagram of a third embodiment of a suitable nozzle in the ignition unit.

[0045] Figure 15 Schematic diagram of another embodiment of an ignition unit according to the present disclosure suitable for use with a burner system.

[0046] Figure 16 for Figure 15 Top view of the ignition unit.

[0047] Figure 17 is a flow chart of a method for regulating NOx and CO emissions according to the present disclosure.

[0048] Figure 18 is an example of an excess air (λ) versus adiabatic flame temperature curve for one fuel composition.

[0049] Figure 19 For implementation Figure 17 Schematic diagram of the system of the method. DETAILED DESCRIPTION

[0050] By reference to the following description including examples, the present disclosure can be more easily understood. In addition, many specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it should be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other cases, methods, procedures, and components are not described in detail in order to avoid confusion with the related features described. In addition, this description should not be considered to limit the scope of the embodiments described herein.

[0051] In the drawings, various embodiments are shown and described, wherein similar reference numerals are used herein to designate similar elements throughout the various views. The drawings are not necessarily drawn to scale, and in some cases, several drawings have been enlarged and / or simplified for schematic illustration only. Where components of relatively well-known designs are employed, their structure and operation will not be described in detail. Those of ordinary skill in the art will appreciate the many possible applications and variations of the invention based on the following description.

[0052] The present disclosure relates to combustion methods and apparatus designed to achieve low nitrogen oxide and carbon monoxide emissions from start-up (cold furnace conditions) to maximum firing rate (design conditions). Unique emissions performance is achieved by targeting specific burner conditions, such as targeting a specific flame temperature, by premixing the fuel with a predetermined air flow in excess of the stoichiometric amount required for fuel combustion, and by anchoring the flame in a specifically designed combustion chamber to provide sufficient residence time to reduce carbon monoxide emissions, thereby isolating the apparatus performance from the effects of the surrounding environment.

[0053] The systems and methods of the present disclosure are generally applicable to furnaces of the type in which a primary fuel is burned in a primary combustion zone with a certain amount of air. The systems and methods are particularly applicable to cases in which, in addition to the primary combustion zone, a secondary fuel is burned in a secondary combustion zone. Typically, the secondary fuel is burned with the excess air from the primary combustion zone; however, the systems and methods are also applicable to furnaces in which additional air is added for the combustion of the secondary fuel.

[0054] Generally speaking, in many embodiments, the primary fuel is sufficiently premixed within a specific range of combustion air that exceeds the amount required for stoichiometric combustion of the primary fuel to minimize thermal and prompt NOx emissions. The resulting primary fuel-air mixture is then discharged and anchored within the combustion chamber of the burner tile. Anchoring the primary flame within the combustion chamber of the burner tile does not allow the heat generated by the flame to be immediately transferred to the surrounding furnace environment, but rather uses the heat generated with sufficient residence time achieved by a properly sized combustion chamber to significantly minimize CO emissions. The NOx and CO levels resulting from this configuration decouple the emission performance of the primary premixed flame from the air surrounding the furnace. Currently on the market, the emissions of NOx and CO are highly dependent on the surrounding environmental conditions and are therefore relatively variable, especially under startup and shutdown conditions. For other combustion devices, the hotter the surrounding environment, the higher the NOx and the lower the CO. Additionally, for other combustion devices, the colder the surrounding environment, the lower the NOx and the higher the CO. The current embodiments avoid these problems

[0055] For example, Figure 1 A simplified burner 110 for a furnace utilizing conventional prior art flame anchoring is shown. In burner 110, the flame anchor 112 appears at the top of the burner tile 114, and the flame length itself projects well from the burner tile 114 into the furnace chamber. Thus, most, if not all, of the combustion occurs outside the burner tile (outside the combustion chamber 116), where it is exposed to (and entrained with) the furnace flue gas. Without being bound by theory, it is believed that such a configuration results in the combustion being exposed to the lower temperature of the surrounding furnace environment, leading to quenching of the flame envelope and thus to additional generation of CO, and the CO in the flue gas is present in an amount greater than 400 ppm, corrected to 3% O2, and in some cases, greater than 500 ppm CO, greater than 600 ppm CO, or even greater than 800 ppm CO, corrected to 3% O2.

[0056] In contrast, some embodiments of the present disclosure utilize flame anchoring at the bottom of the combustion chamber defined by a burner tile contained within the inner side of the furnace, as Figure 2 shown. In Figure 2In [the figure], a simplified burner 210 is shown. The burner 210 is designed to have a flame anchor 212 (further described below) appear inside a combustion chamber 216 defined by a burner tile 214. The Figure 2 configuration shown is simplified and presented as being similar to Figure 1 , for direct comparison, and Figure 2 shows flame anchoring inside the combustion chamber 216 or inside the burner tile 214, rather than flame anchoring at the top of the burner tile 114 or at the outlet hole 118 of the burner tile as Figure 1 shown. In some embodiments, the burner tile may have an extended body (such as Figure 3 and 4 shown) in order to enlarge the burner chamber and increase the residence time of the fuel-air mixture and the resulting flue gas. As can be seen from Figure 2 , the combustion chamber is defined by the burner tile 214, and the combustion chamber is the space from the base 220 of the burner tile upward to the outlet hole 218 at the top of the burner tile. Thus, the combustion inside the combustion chamber 216 is shielded from the surrounding furnace environment by the tile wall 222.

[0057] Embodiments using the above low flame anchoring and / or other principles discussed herein utilize a longer residence time for the fuel-air mixture and the flue gas in a primary combustion zone shielded from the surrounding furnace environment. Traditionally, burners place most of the fuel outside the tile. Conventional burners that mix some fuel and air and emit it inside the burner tile have a minimal residence time (if any) where the fuel-air mixture and the resulting flue gas are shielded from the surrounding furnace environment. Many current devices and methods can result in a residence time of at least 0.01 seconds.

[0058] According to specific embodiments currently disclosed, a primary combustion chamber is utilized, which decouples the emission performance of the primary combustion zone from the surrounding environment and allows the primary flame to burn in a manner that suppresses the levels of prompt nitrogen oxides and carbon monoxide emissions, as well as the temperature of the thermal nitrogen oxides and carbon monoxide emissions. Generally speaking, embodiments of the present invention allow NOx levels of less than 15 ppm, corrected at 3% O2, and more typically less than 10 ppm, less than 9 ppm, or less than 5 ppm, NOx levels corrected at 3% O2. At the same time, embodiments of the present invention allow CO levels of less than 400 ppm, corrected at 3% O2, and more typically less than 350 ppm, less than 300 ppm, less than 200 ppm, less than 100 ppm, or even less than 50 ppm, corrected at 3% O2. Additional emissions that can be reduced as by-products are UHC, VOC, and possibly PM10 or PM2.5. Additionally, these advantages can be achieved at all stages of the operation of current devices and methods.

[0059] Accordingly, embodiments of the present invention have advantages over existing systems in that they are capable of reducing nitrogen oxides and carbon monoxide emissions both during start-up / shutdown heat release (cooler furnace temperature operation) and at maximum (designed) heat release (hotter furnace temperature operation). Commercially available solutions currently optimize the reduction of nitrogen oxides during designed heat release while sacrificing carbon monoxide emission performance under start-up / shutdown conditions. The embodiments described in the present disclosure can meet more stringent nitrogen oxide requirements than currently available on the market, as well as carbon monoxide emissions under both start-up / shutdown and designed heat release conditions.

[0060] Turning now to Figure 3 and Figure 4 , examples of devices utilizing the methods and designs of the present disclosure will now be further described. In these examples, the furnace utilizes a burner 310 including a burner tile 314, which is typically a refractory brick. The burner tile 314 has a base 320 mounted to the wall 306 of the furnace, which can be the bottom plate, side, or top of the furnace. The burner tile 314 has a wall 322 extending from the base 320 at a first end 324 to a second end 326 where the outlet hole 318 is located. The tile wall 322 defines a combustion chamber 316. In an embodiment, the combustion chamber is generally shown as a cylinder, and the tile wall typically has a cylindrical shape; however, the shape can be different. For example, shapes with rectangular, square, or elliptical cross-sections can be used for some operating conditions. In the illustrated embodiment, the first end 324 is closed by a mounting plate 328 such that fluid flowing into or out of the combustion chamber 316 is limited to the outlet hole 318 or extends through the mounting plate 328 via a tube, as further described below.

[0061] Figure 3 The tile wall 322 of the embodiment of Figure 4 extends along the burner axis 354 and provides an uninterrupted wall defining the combustion chamber 316; that is, the wall does not have an opening or hole.

[0062] The plenum chamber 330 is fixed to a mounting plate 328 on a side opposite to the burner 314 and is disposed on the opposite side where combustion air and fuel are introduced into the combustion chamber 316. The plenum chamber 330 has a solid plenum chamber wall 332 extending from the mounting plate 328 to a plenum chamber base 334. The plenum chamber wall 332 defines an air chamber 336. The plenum chamber base 334 has an opening 338 through which air can enter the air chamber 336, and the opening can be a screened opening. The screen, which can be a perforated restriction plate, surrounds the tube inlet 342 and the primary fuel nozzle 344, improving the air distribution to the tube 340. Additionally, the screen can prevent dirt particles and debris from entering with the air. The plenum chamber is thus configured to prevent air from entering the air chamber 336 other than through the opening 338. Additionally, air can only enter the combustion chamber 316 from the air chamber 336 through tubes 340 extending through the mounting plate 328, as described below.

[0063] Inside the plenum chamber 330 there are a plurality of tubes 340 for introducing a fuel and air mixture into the combustion chamber 316. Typically, there will be two or more such tubes, and there can be five or more tubes. From Figure 8 and Figure 9 it can be seen that some embodiments have up to 10 or more tubes. The cross-sectional profile of each tube can be circular, oval, rectangular, or any other shape, such as star-shaped.

[0064] For each such burner 310, the tube 340 serves as the main introduction of the fuel-air mixture into the furnace. An igniter ( Figure 3 and Figure 4 not shown in the figures) can be present in the combustion chamber 316 to ignite the fuel. In the example shown, the tubes are arranged in a circle and are adjacent to the inner surface of the combustion chamber, as Figure 8 and Figure 9 can be seen. Variable positioning relative to each other and the number of tubes inside the plenum chamber and the tile are possible and depend on the burner size and operating requirements.

[0065] The tubes 340 shown are fuel-air mixing tubes in that at the inlet 342 of each tube is a primary fuel nozzle 344 that discharges a high-momentum fuel jet from a fuel dispenser 349 and a fuel source 347 along the longitudinal axis of the tube into the associated tube 340. The high-momentum fuel jet entrains air from the plenum chamber base 334 of the plenum chamber and promotes mixing between the air and the fuel to produce a fully mixed stream at the outlet 348 of the tube 340. Figure 3 A natural draft plenum chamber without forced air is shown. However, as Figure 4As shown, air can be entrained and / or forced by using a fan or blower in fluid flow contact with the housing 435 around the opening 338 at the base 334 of the plenum chamber. Thus, the fan provides forced ventilation to the plenum chamber through the opening 339 in the housing 435.

[0066] The outlet 348 of each tube 340 can be equipped with a flame holder 350, which is positioned at a fixed distance from the outlet 348 and is used to help stabilize and anchor the flame. The flame stabilization / anchoring device (flame stabilizer 350) laterally expands the incoming fuel and air mixture so that it can diffuse through the inner surface 321 of the tile wall defining the combustion chamber and can be anchored on the inner surface 321 of the burner tile and the inner side of the base or flange 327. The flame stabilization / anchoring device 350 also helps to generate vortices for greater flame stabilization and anchoring.

[0067] The flame holder or flame stabilization / anchoring device 350 can be configured in a variety of shapes, such as cups, cones, honeycomb structures, rings, perforated disks. Additionally, embodiments can use other flame stabilization / anchoring devices and arrangements, such as bluff bodies, flanges built into the tile, or can employ vortices.

[0068] Although the above fuel-air mixing tubes introducing the fuel-air mixture are currently preferred, other delivery systems that provide thorough fuel-air mixing can also be used. For example, the fuel-air mixture can be generated upstream of the plenum chamber 330 and introduced into the tubes 340. In another example, fuel and air can be provided separately to the combustion chamber and then "rapidly mixed" at the combustion chamber inlet, as long as the fuel and air can be thoroughly mixed to ignition and can be anchored within the combustion chamber. This can be achieved by using high pressure drops and / or rotating air or fuel or both.

[0069] Near the level of the heating furnace wall 306 and just outside the tile wall 322, a plurality of additional raw gas fuel nozzles or staged fuel nozzles 352 are placed (usually there will be four or more, and it is not uncommon to have eight or ten nozzles). Each staged fuel nozzle 352 can receive fuel from the distributor 346 and the fuel source 347, and each staged fuel nozzle 352 is designed to discharge a fuel jet in a direction generally downstream of the outlet hole 318 outside the burner tile 314, so as to generate a secondary combustion zone outside the combustion chamber 316 and generally downstream of the outlet hole 318. For example, the staged fuel nozzle 352 can discharge fuel along the outer surface 323 of the tile wall 322 in the direction of the flame flow at a variable angle relative to the longitudinal burner axis 354.

[0070] Although Figure 3 and Figure 4Only the staged fuel nozzles outside the burner tile are utilized, but the current embodiments can be utilized in conjunction with designs that also utilize primary fuel nozzles outside the burner tile. For example, some of the current embodiments can utilize a Coanda design with fuel nozzles outside the burner tile, as disclosed in U.S. Patent No. 7,878,798, published on February 1, 2011. In that patent, there are multiple ignition fuel nozzles, as well as multiple nozzles for staged fuel outside the burner tile. Each ignition fuel nozzle is designed to discharge a fuel jet onto a Coanda profile window that leads to the combustion chamber of the tile. The purpose of the ignition fuel is to provide some local fuel-rich points with a minimal heat release in the combustion chamber, in order to minimize the overall emission impact from the ignition fuel.

[0071] When using such a combination of ignition fuel nozzles and staged fuel nozzles, they can be positioned in an alternating sequence on a circle of the same diameter. The distance between the nozzles and the number of nozzles can vary depending on the burner size. The nozzles can also be positioned at different locations around or within the burner. For example, the ignition nozzles can be located close to the Coanda profile window, while the staged nozzles can be placed at a larger radius from the burner axis. In another example, the staged nozzles can be introduced remotely into the roasting atmosphere (furnace) in order to target specific heat flux or other operating or emission (low NOx) requirements. In another example, the ignition nozzles can be only one or more ignition nozzles located within the combustion chamber itself. The design of the ignition fuel and staged fuel regions can vary depending on the design details.

[0072] Now turning to Figure 5 , which shows a third embodiment similar to Figure 3 and Figure 4 and related to a furnace 500. The furnace 500 includes a furnace enclosure 502 having a stack 504. The furnace at least partially contains a burner 310 with refractory bricks 314 that define a combustion chamber 316 inside the tile. The refractory bricks 314 are fixed to the furnace enclosure 502. As shown, the refractory bricks 314 are fixed to the furnace wall, in this case the furnace floor 506, but can be fixed to the side walls of the furnace. The refractory bricks 314 are also fixed to a plenum chamber 330, which can also be fixed to the outer furnace floor 506. The plenum chamber 330 has an air inlet 342, which is schematically shown and can be a natural draft arrangement or a forced air supply arrangement.

[0073] As noted, the burner 310 also includes an ignition unit 560 (usually ignited by an igniter (not shown)), a tube 340, a flame holder 350, and a primary fuel nozzle 344. The ignition tip 562 of the ignition unit 560 is located within the combustion chamber 316 and extends through the plenum chamber 330 to attach to a fuel source (not shown) at a second tip 564. Inside the plenum chamber 330 are a plurality of tubes 340 that discharge into the combustion chamber 316. The tubes 340 use the entrainment principle to mix fuel and air, as described above. Generally, the tubes 340 will surround the ignition unit 560; for example, five or six mixing tubes 340 may be positioned in a circle around the ignition unit 560. The outlet of each tube 340 is equipped with a flame holder 350, which is positioned at a fixed distance from the tube outlet and is used to help stabilize and anchor the flame.

[0074] As for Figure 3 and Figure 4 the case of Figure 5 the embodiment shown in

[0075] As can be seen from Figure 5As will be appreciated, fuel from the ignition unit 560 and the fuel-air mixture from the tube 340 combust in the combustion chamber 316 and immediately downstream of the combustion chamber 316 to form a primary combustion zone 566. In some embodiments, the fuel for combustion in the primary combustion zone 566 may be provided only by the tube 340 after startup or ignition. In some embodiments, the combustion air or oxygen for combustion within the furnace 500 is typically supplied only through the tube 340 and in an amount that exceeds the stoichiometric combustion of the fuel from the ignition unit 560 and the tube 340. The fuel from the staged fuel nozzle 352 mixes with the flue gas and the excess combustion air and then combusts in the secondary combustion zone 568. Thus, the primary combustion zone 566 is formed within the combustion chamber 316 and may extend into the furnace only downstream of the end of the combustion chamber 316. The secondary combustion zone 568 is formed outside the primary combustion zone 566. The secondary combustion zone 568 will be in the furnace outside the burner tile 314 and typically downstream of the flame anchoring of the primary combustion zone 566 and may be downstream of the primary combustion zone 566. Although the secondary combustion zone may be directly downstream of the primary combustion zone 566, it is currently believed that it will more typically at least partially surround a portion of the primary combustion zone and may have an annular shape or a cup shape and surround the downstream portion of the primary combustion zone and extend downstream of the primary combustion zone.

[0076] As Figure 5 shown, the secondary fuel jets discharged from the staged nozzle 352 are directed in a generally downstream direction; i.e., the direction in which the primary flame stream moves. The secondary fuel jets gradually mix with the primary zone flame stream and combust as they travel through the furnace space. Prior to mixing with the primary flame, these secondary staged fuel jets entrain and mix with the furnace atmosphere gas, which is mostly inert substances such as CO2, H2O, and N2. Thus, when mixed and combusted with the lean fuel flame stream from the tile, the secondary staged fuel jets saturated with inert gas do not create a region of elevated flame temperature. For example, the design can be arranged to have an adiabatic flame temperature of 2400 - 2600°F within the secondary combustion zone 568, which is low enough not to produce thermal NOx.

[0077] Figures 3 - 5 embodiments have all or substantially all of the required combustion air entrained or pushed through the tube 340 and delivered to the combustion chamber 316. For example, the edge (or side) of the tube 340 can be sealed to the mounting plate 328 of the plenum chamber 330 and the base 320 mounted to the burner tile 314, ensuring that no air can enter the combustion chamber from the plenum chamber 330 without traveling through the tube 340. In an alternative embodiment, such as those described below Figure 6 and 10 , a small amount of combustion air can be introduced in other regions of the combustion zone.

[0078] It is currently believed that the greatest beneficial effects are delivered by introducing all of the combustion air and the primary fuel into the combustion chamber 316 or by introducing the major portion of the combustion air into the combustion chamber 316. However, in some embodiments, a smaller portion of the combustion air may be introduced outside the combustion chamber 316. A "trace" or "small portion" of the combustion air generally refers to 25% or less of the stoichiometric air required to burn one unit of fuel. Typically, it will be less than 10% of the required stoichiometric air, and may be 10% or less. In many embodiments, the small amount of combustion air will be in the range of 5% to 25% of the stoichiometric air required to burn one unit of fuel. When all of the combustion air is supplied to the combustion chamber 316, those skilled in the art will understand that this may allow a negligible amount of combustion air to enter the combustion zone from other sources, such as from the orifices of the staging injectors, the ignition injectors, etc. Generally speaking, to account for such negligible amounts of combustion air, the present disclosure will refer to "substantially all" of the combustion air in the primary fuel-air mixture. In this case, "substantially all" means all of the air except for these trace amounts of air that are less than 3%, less than 2%, less than 1%, or less than 0.5% of the combustion air required to burn the fuel introduced for ignition, the primary fuel, and the staging fuel. Generally speaking, "substantially all of the air" may mean at least 97%, at least 98%, at least 99%, or at least 99.5% of the air required for fuel combustion, where the fuel includes the primary fuel, and optionally a second portion of fuel for ignition and a third portion of fuel for staging fuel combustion.

[0079] As will be achieved by the foregoing, the fuel and air mixture introduced into the combustion chamber by the tube 340 will not be stoichiometric; that is, the mixture will not have the ratio of fuel to oxidizer required for stoichiometric combustion of the primary fuel (the fuel introduced into the combustion chamber 316). Instead, the primary fuel will be introduced as a lean fuel-air mixture. A "lean" fuel-air mixture indicates a fuel / oxidizer mixture that contains more oxidizer than the amount required to completely burn the fuel. Generally speaking, the embodiments described herein may be in the range of 50% to 110% excess air (about 7% to 11% excess oxygen).

[0080] Now turning to Figure 6 an embodiment is shown in which a small amount of combustion air may be introduced separately from the fuel-air mixing tube. Figure 6Shows a heating furnace 500 that at least partially houses a burner 610 having a refractory brick 314 that defines a combustion chamber 316 having a tube 340 and a flame holder 350. Additionally, the tube 340 supplies fuel gas through a primary fuel nozzle 344 and receives combustion air from a surrounding plenum chamber 330. The heating furnace 500 has a staged fuel nozzle 352 outside and surrounding the tile 314. The above components are similar to Figure 5 those, but may be according to other embodiments shown herein. Thus, as with Figure 5 the embodiment shown, the heating furnace 500 forms a primary combustion zone 566 and a secondary combustion zone 568.

[0081] However, the burner 610 includes a bypass air tube 670 that introduces combustion air into the heating furnace 500 so as not to affect the combustion occurring in the primary combustion zone 566. It can be seen that the bypass air tube 670 even extends downstream of or from downstream of the primary combustion zone 566 such that the combustion air entering through the bypass air tube 670 is introduced into the secondary combustion zone 568 without being introduced into the primary combustion zone 566. Thus, when a relatively small amount of primary fuel is available for the primary combustion zone, the fuel-air mixture introduced through the tube 340 can be significantly lean, i.e., having sufficient excess air for complete combustion of the primary fuel in the primary combustion zone. Accordingly, additional combustion air - for secondary fuel combustion and for maintaining excess oxygen in the stack 504 - is provided through the bypass air tube 670. The introduction of combustion air through the bypass air tube 670 is controlled by an actuator 672. For example, a computer processing system can control the actuator 672 to reduce or increase the combustion air introduced through the bypass air tube 670 as necessary to control the adiabatic flame temperature (ATF) within the primary combustion zone, which will enable further control of the NOx and CO levels in the primary and secondary combustion zones, as further discussed below. This is particularly useful where the primary and secondary fuels are different and the amount of fuel available in the primary combustion zone is limited below the desired amount required to achieve an appropriate AFT with all of the combustion air introduced into the primary combustion zone.

[0082] Alternatively or in addition to the above, the regulation of the combustion air introduced through the tube 340 and the combustion air introduced through the bypass air tube 670 can be used to vary the air distribution within the burner 610. For example, the amount of excess air from the primary combustion zone can be increased or decreased as the corresponding amount of excess air from the bypass air tube 670 is decreased or increased.

[0083] Now turning to Figures 7 - 14 , certain features of the above-described embodiments and additional embodiments of the present disclosure will now be discussed. Specifically, Figure 7 another burner embodiment is shown.Figure 7 The burner 710 has many components similar to Figures 3 - 5 ; thus, like reference numerals denote like components. However, in view of Figures 3 - 5 using cylindrical burner tiles (inner and / or outer), embodiments of the present disclosure may also utilize burner tiles having convergent or divergent inner surfaces that define a burner chamber. For example, Figure 7 illustrates a burner tile 714 having a tile wall 722 that has a cylindrical outer surface 723 and a divergent inner surface 721. Thus, the tile wall 722 is thicker at a first end 724 than at a second end 726. Thus, in contrast to Figures 3 - 5 the cylindrical combustion chamber of the divergent inner surface 721 defines a conical combustion chamber 716. This divergence angle of the inner surface 721 allows the flame and recirculation vortices to expand freely towards the tile outlet hole or outlet 718, thereby preventing possible pressure fluctuations inside the tile combustion chamber, especially at higher heat releases.

[0084] As Figure 7 shown by the staged fuel nozzle 352, staged fuel jets are discharged outwardly from the outer surface 723 of the burner tile 714. The nozzle may be positioned at a greater distance from the burner and may even be placed in the furnace wall, rather than opposite the base 720 of the tile 714. Figure 8 illustrates such an arrangement where the furnace wall 306 has a plurality of burners 710 with staged fuel nozzles 352 positioned in the furnace wall 306 away from the burner tile 714. The positioning of the staged fuel nozzle 352 relative to the burner tile is determined to achieve the maximum possible saturation of the staged fuel jets by the inert furnace flue gas prior to mixing with the excess air from the primary combustion zone. Thus, the staged fuel nozzle 352 may discharge fuel jets outwardly from the outer surface 723, discharging the fuel jets in line with the outer surface 723 or even towards the outer surface 723 of the burner tile 714 to assist in achieving such saturation.

[0085] As previously mentioned, the number, diameter, and cross-sectional shape of the tubes 340 can vary significantly from one tile size to another. Figure 9 illustrates ten tubes 340 positioned in two rows inside the tile wall 722; each having a different radius from the center or central ignition unit 760. Figure 10 illustrates ten tubes positioned in a row around the center or central ignition unit 760. Although shown with respect to Figure 7 the embodiments of those skilled in the art will understand that the placement principle generally applies to most embodiments covered by the present disclosure, including other specific embodiments disclosed herein.

[0086] While igniters are known in the art, other embodiments provide novel igniter units that can be used as the ignition unit of the above embodiments. Figure 7 One such igniter unit 760 is shown relative to the burner tile 714. Figure 11 The igniter unit 760 is shown in more detail.

[0087] The igniter unit 760 includes a fuel supply lance 880 concentrically positioned within the riser tube 900. A first end 882 of the lance 880 is in fluid flow communication with a fuel gas source ( Figure 11 not shown). A second end 884 of the lance 880 terminates within the riser tube 900 at a fuel discharge nozzle 886 such that fuel flowing through the lance 880 is discharged through the fuel jet in a vortex pattern. In other words, the fuel is discharged so as to move circumferentially and longitudinally within the riser tube 900.

[0088] Some suitable configurations of the nozzle 886 are shown in Figure 12 , 13 and 14. As shown in Figure 12 and Figure 14 , the nozzle 886 can have one or more discharge arms 888 that serve as fuel jets. The discharge arms 888 discharge the fuel tangentially to the inner surface 902 of the riser tube 902, which is tangential with respect to the fuel supply lance 880. Typically, there will be a plurality of discharge arms 888 equally spaced around the circumference of the lance 880. Figure 12 Three discharge arms 888 are shown, and Figure 13 six discharge arms 888 are shown. As shown in Figure 14 , the vortex pattern can also be achieved by one or more channels within the lance 880 that serve as fuel injectors. The channels 890 extend from an inner surface 892 through the lance 880 to an outer surface 894. The channels 890 extend tangentially from the inner surface 892. Typically, either the discharge arms 888 or the channels 890, whichever is used, are angled toward the second end 908 of the riser tube 900; thus, the fuel is discharged tangentially to the center of the riser tube 900 and slightly forward (toward the second end 908). Typically, the forward angle will be from about 5 degrees to about 25 degrees.

[0089] The riser tube 900 has a first end 904 that can be closed (not shown) or can be in fluid flow communication with a supply of combustion air (as shown in Figure 11 ). Thus, the first end 904 can terminate at a hole 906 located at or near the base of the plenum chamber 334, either inside or outside the plenum chamber (as shown). Typically, the hole 906 will be outside the plenum chamber, especially where there is a forced air supply entering the plenum chamber.

[0090] The swirl cup 910 is connected to the second end 908 of the riser 900. The swirl cup 910 is positioned within the burner tile and is axially positionable along the center burner axis 354 of the burner 710. Additionally, the swirl cup 910 will generally be centered within the tube 340, as Figures 7 - 10 shown. The swirl cup 910 is configured to promote the swirling and forward movement of the fuel discharged from the nozzle 886. As shown, the swirl cup 910 includes a diverging curved wall 912.

[0091] In operation, high-pressure raw fuel gas is directed through the lance 880 towards the connected nozzle 886. The fuel is then discharged tangentially to the center of the riser 900 and slightly forward (5 - 25 degrees) by the fuel injection (such as the discharge arm 888 or the passage 890). Thus, the discharge angle is a compound angle that allows one or more fuel injections to swirl and move forward inside the riser 900. The swirling / helical movement continues along the inner surface of the swirl cup 910, resulting in the formation of a swirling flame inside the swirl cup 910 and further a swirling flame as it exits the swirl cup 910. A direct electric spark provided by an igniter 761 ( Figure 7 schematically shown therein) known in the art can be used to immediately ignite the flame. The vortex flame is very stable due to the formation of a strong counter-rotating vortex along the centerline 914 inside the swirl cup 910. This vortex permanently re-ignites the eddy current and maintains the overall stability of the ignition flame.

[0092] The vortex flame can be organized with or without a slight air flow through the riser 900 towards the swirling fuel jets. Figure 11 As shown, some air can pass through the toroidal channel 901 formed between the inner surface 902 of the tube 900 and the outer surface 894 of the lance 880. The air flow can be optimized to minimize NOx emissions.

[0093] As noted, the swirl cup 910 can be positioned along the center burner axis 354 of the burner 710 and in the center of the tube 340, as Figures 7 - 10 shown. In this position, the vortex flame can contact all of the primary fuel-air flow exiting the tube 340 and immediately ignite it. However, depending on the tile geometry, the number and geometry of the tubes, and other factors, the ignition unit 760 and the tube 340 can be positioned differently within the scope of this disclosure.

[0094] Figures 15 - 16 Another embodiment of a possible ignition unit is shown. This ignition unit 920 has a central duct or tube 922 that extends along the longitudinal centerline 924 of the burner tile, such as Figure 3 314. The duct 922 has at least one radially extending strut 926. Typically, the duct 922 will be divided into a plurality of radially extending struts (five, asFigure 16 as shown). Each strut 926 terminates in a nozzle 928 having one or more orifices 930 for discharging fuel jets along the inner circumference of the inner surface 321 of the burner tile 314. The fuel or air mixture is introduced through the central duct 922, through the struts 926, and then through the nozzle 928 onto the inner surface 321 of the tile wall 322 such that the fuel or fuel-air mixture moves circumferentially along the inner surface 321. Where only fuel is provided through the nozzle 928, or where insufficient air for stoichiometric combustion of the fuel is supplied through the nozzle 928, the air from the fuel-air mixture through the duct 340 is used to combust the fuel from the ignition unit.

[0095] Generally speaking, the discharge through the nozzle 928 will be along the flange 327, if used. Thus, the flame formed by the ignited fuel jets can be held inside the annular cavity 932 formed by the tile flange 327 and inside the ring 934 mounted on the flange. A direct electric spark device (igniter 761) known in the art can be used to ignite the fuel discharged from one of the nozzles 928. Once a flame is established from one nozzle, the flame propagates very reliably circumferentially in both directions.

[0096] In the above embodiments, the flow of the primary fuel and the secondary fuel can be controlled by adjusting the flow rate of the fuel introduced through the primary fuel nozzle 344 and the secondary fuel nozzle 352. Generally, the adjustment of the flow rate is inversely correlated, i.e., if the primary fuel flow increases, the secondary fuel decreases, or vice versa. Additionally, the combustion air introduced into the natural draft burner can be controlled by adjusting the plenum chamber, such as by changing the orifice size for introducing air, so as to allow more or less air to pass through the plenum chamber. The combustion air in the forced draft burner can be controlled by changing the air forced into the plenum chamber, such as by changing the fan or blower speed. In some embodiments, a computer processing system can be configured to control the fuel flow and the introduction of air into the plenum chamber, as further discussed below.

[0097] Additionally, the air chamber 336 of the plenum chamber 330 can be empty (except for air). Thus, the air above the air chamber 336 is heated near the end of the mounting plate 328, and the heated air gas can travel downward on the outside of the duct 340 from the end near the combustion chamber, preheating the primary combustion air in the duct 340 similar to a recuperative heat exchanger. It has been found that doing so can further improve the CO emission performance by increasing the fuel-air mixture temperature before it exits the duct 340, which is just sufficient to simulate additional residence time in the combustion chamber. In another example, the duct 340 can be directly mounted to the combustion chamber mounting plate and not surrounded by the plenum chamber.

[0098] As shown, the combustor design can include a calculated volume, a flange 327, an ignition and pressure relief / recycle window ( Figure 4 the orifice 425 of Figure 4 ), a tube 340 (substantially a mixing tube) disposed inside the combustor, and a flame holder 350. The above components are uniquely arranged relative to each other to ensure that the primary flame anchor is at the desired location inside the combustor. Any number of combustion anchor devices 350 can be utilized, and they are used to stabilize the primary flame on the inner side of the combustor of the tile.

[0099] As a result, the device can operate at an excess air level close to or even above the flammability limit of the fuel at room temperature. These conditions reduce the heat from the flame and the rapidly formed nitrogen oxides. The carbon monoxide emission level is suppressed because the combustor design of the tile raises the local ambient temperature inside the combustor of the tile. It is currently believed that this makes the CO emission level of the primary flame similar to that of a typical device installed in a thermal application (thermal heating furnace application), where the CO emission level is naturally reduced due to the rapid oxidation rate of CO2.

[0100] According to the above discussion, the general method of operation of the above embodiments includes first establishing a furnace negative pressure to cause a combustion air flow to pass through the tube 340 in an amount required for ignition. The flow of the raw ignition fuel from an ignition unit (e.g., ignition unit 760 or ignition unit 920) is delivered into the combustor of the burner tile and is ignited using an igniter. In some embodiments, the flow of the ignition fuel can be directed along the inner tile flange of the tile, such as through ignition unit 920 or due to the Coanda effect generated by the shape of the channel side (using the Coanda design of U.S. Patent No. 7,878,798).

[0101] After establishing the ignition flame, the primary fuel nozzle 344 injects fuel into the tube 340 such that the fuel is thoroughly mixed with the combustion air using the entrainment effect, and the mixture is ignited by the ignition unit by the ignition flame already present in the combustor. Thus, the primary flame is stabilized on the flame holder 350 and the inner stepped flange 327 of the tile, if used. Stability is maintained by the hot, re-igniting eddy just downstream of the flame holder and the recirculation zone formed by the flange of the tile. A portion of the air-fuel mixture is deflected by the flame holder onto the inner surface of the combustor of the tile. The mixture scrubs and burns on the surface, causing the surface to glow and act as an additional, reliable flame source for stabilization on the inner side of the combustor of the tile.

[0102] To form the lowest possible NOx emissions, it is necessary to suppress the thermal and rapidly formed nitrogen oxides. Preferably, without compromising flame stability, the air / fuel ratio at the outlet of the mixing tube is set as high as possible, as close as possible to the flammability upper limit. For example, the excess air level can be controlled to 50 - 110% (lean mixture, lean flame) excess air level. The fuel preferably travels through tube 340 as thoroughly as possible while being mixed with air; the uniformity of the air / fuel mixture is crucial for the performance of the device.

[0103] As previously discussed, in other embodiments, the fuel and air can be provided separately to the device combustion chamber, as long as they are quickly mixed to an appropriate level before ignition.

[0104] Anchoring the flame in the device combustion chamber allows an average and uniform adiabatic flame temperature of 2400 - 2600°F. Thus, the device combustion chamber space temperature is also around 2400 - 2600°F, regardless of the ambient temperature (the heater chamber temperature outside the burner).

[0105] To increase the heat release from normal to maximum heat release, the embodiment uses a staged fuel nozzle 352. Gradually discharging the staged fuel allows the heat release to be increased from the normal heat release to the maximum heat release by consuming the excess oxygen in the primary flame. For example, if the burner operates at a heat release of 5 MMBtu / hr, with only primary fuel and ignition fuel, and the mixture burns with the flame stabilized inside the tile, the oxygen concentration in the heater stack is set between 7 - 11% (space dry). At this time, the blower combustion air flow rate is fixed, and the staged fuel flow can be gradually increased to consume the excess oxygen and achieve a heat release rate of 8 MMBtu / hr. The stack oxygen content will be reduced to 2 - 3% (space dry), which is a common requirement for heater operation at maximum heat release to obtain the best fuel efficiency.

[0106] Once this condition is achieved, both the primary fuel and the staged fuel, as well as the air supply, can be proportionally changed to maintain 2 - 3% (space dry) excess O2 in the heater stack, as long as the ambient (heater flue gas firewall) temperature does not drop below a certain lower limit, below which the staged fuel will start to produce additional CO emissions. Before this occurs (usually at or below a heater temperature of ~1350°F), then the staged fuel can be shut off, and low CO and NOx emissions can be maintained by operating only the primary flame, which is anchored in the device combustion chamber.

[0107] In many applications, the fuel composition can change during the operation of a burner. Due to the change in fuel composition, the emissions of NOx and CO can vary. Additionally, variants that drive the changes in NOx and CO emissions are the combustion air conditions (such as the relative humidity in the air), and the furnace flue gas temperature around the combustion flame. All of these system conditions can result in large variations in NOx and CO emissions. Accordingly, the present disclosure also relates to systems and methods for adjusting a burner to maintain desired NOx and CO emissions.

[0108] Generally speaking, the systems and methods will monitor the fuel composition in order to detect changes in the fuel composition. This determination can be made at intermittent intervals or periodic intervals, or can be determined continuously. The systems and methods also monitor the flow rate of the primary fuel entering the system and the flow rate of the secondary fuel entering the system. Additionally, the systems determine the adiabatic flame temperature (AFT) at various locations in the furnace or burner. Typically, the locations will include at least a primary combustion zone and a secondary combustion zone. These AFT values can be calculated from the fuel composition and the amount of air introduced into the burner and / or furnace, in which case the combustion air flow into the burner / furnace is monitored. Alternatively, the actual flame temperature at each location can be monitored by sensors.

[0109] After the AFT values are determined, the amount of air required to minimize NOx is determined. The amount of air can be determined based on the AFT values and an experimental curve, where the experimental curve is derived from experimental data regarding the excess air amount (the amount of air in excess of the stoichiometric air flow required for the chemical reaction to complete combustion) and the adiabatic flame temperature (AFT) for a variety of fuel compositions.

[0110] Based on the air amount determination, at least one of the flow rate of the primary fuel, the flow rate of the secondary fuel, the amount of air introduced into the burner and / or furnace, and the distribution of the air introduced into the burner and / or furnace is adjusted. As will be appreciated, if the fuel flow rate is adjusted, the adjustment step generally corresponds to at least both the flow rate of the primary fuel and the flow rate of the secondary fuel. Additionally, the flow rate of the primary fuel and the flow rate of the secondary fuel are typically adjusted simultaneously. For example, when the flow rate of the primary fuel increases, the flow rate of the secondary fuel decreases simultaneously.

[0111] Reference may be made to Figure 17 for a further understanding of the method and system. Wherein a burner startup procedure 950 is outlined at various stages, followed by normal burner operation.

[0112] For an inactive furnace, activate the burner startup procedure 950. First, in step 952, establish a combustion air flow by starting the blower, and ignite the ignition fuel introduced through the ignition unit, for example, by using a direct spark igniter. The ignition unit can be of any suitable design, such as a vortex type ignition unit or a tile-flange ignition unit.

[0113] Once an ignition flame is established for the ignition unit, step 954 is activated. In step 954, the primary fuel and combustion-air mixture are initiated through the primary fuel injector. Then the mixture introduced into the burner through the primary fuel injector is ignited by the flame of the ignition unit.

[0114] After establishing the primary flame, step 956 continues to increase the primary fuel flow to obtain maximum heat release in the primary combustion zone. The combustion-air flow is also increased to maintain the oxygen level in the heater stack at a first excess oxygen level and to maintain an exact excess air / oxygen level within the primary combustion zone, which is related to the specific combustion temperature for emissions. Generally, this first excess oxygen level will be sufficient to allow the primary fuel to burn at an oxygen level calculated to minimize NOx and CO emissions. For example, the primary fuel can be introduced with sufficient oxygen to burn the primary fuel in the primary combustion zone and maintain the oxygen level in the stack at 7 - 11% (space dry) (the first excess oxygen level) in step 956. This can be calculated such that when the secondary fuel flow is initiated in step 958, the secondary fuel burns in the secondary combustion zone and a remaining oxygen level of 2 - 3% is left in the stack during normal burner operation 960. The 2 - 3% oxygen level is a typical standard applied as the normal excess oxygen level in a roasting apparatus to maximize fuel efficiency. As noted above, as used herein, "stack" or "furnace stack" includes any point downstream of the furnace combustion zone where the emissions and excess oxygen content of the flue gas can be measured. Generally, this point will be in the stack or outlet flue of the radiant section of the furnace, but in some embodiments can be an area within the furnace but outside the combustion zone, or can be an area just downstream of the furnace outlet flue.

[0115] Next, during the burner startup procedure 950, step 958 is activated, where the staged fuel or secondary fuel is discharged from the staged fuel nozzle into the furnace. To increase the heat release from the primary combustion zone and thus the maximum total heat release, the furnace is equipped with a staged fuel nozzle to discharge a secondary fuel jet. The discharge of the staged fuel allows the heat released from the primary fuel to increase, maximizing the total heat release by consuming the excess oxygen of the primary flame.

[0116] Therefore, after raising the temperature of the heating furnace to a temperature sufficient for the staged fuel by burning the primary fuel, the secondary fuel flow is initiated through the staged fuel nozzle. Once the secondary fuel flow is initiated, the primary fuel flow, the staged fuel flow, and / or the combustion-air flow can be adjusted to achieve the total burner heat release (primary fuel and secondary fuel together) required for the process.

[0117] For example, if the burner is operating with a heat release of 5 MMBtu / hr, with only primary fuel introduction (primary injector and ignition unit), and the mixture burns with the flame stabilized inside the tile, the oxygen concentration in the heating furnace stack can be set between 7 - 11% (bone dry). At this time, the blower combustion-air flow rate is fixed, and the secondary (staged) fuel flow can be gradually increased to consume the excess oxygen and achieve a heat release rate of 8 MMBtu / hr. The stack oxygen content will be reduced to 2 - 3% (bone dry), for example, which is a common requirement for heater operation at maximum heat release.

[0118] Alternatively, once the heating furnace temperature is sufficient for staged fuel firing, the staged fuel introduction can be initiated, and the primary fuel and air flows can be reduced while increasing the secondary fuel flow to achieve the desired oxygen content in the heating furnace stack - for example, 2 - 3% (bone dry) oxygen - without having to burn significantly more total fuel (primary fuel and secondary fuel combined).

[0119] Once the staged fuel has been initiated and a predetermined oxygen level in the stack has been achieved, the heating furnace is in normal burner operation. According to the current method, during normal burner operation 960, both the primary and secondary fuel flows and the air supply can be varied proportionally to maintain a predetermined excess oxygen in the heating furnace stack, in this example, above 2 - 3% (bone dry) excess oxygen in the heating furnace stack. Typically, only the primary and secondary fuel flows will be changed. Additionally, as long as the ambient (heater flue firewall) temperature drops below a predetermined lower limit at which the staged fuel will start to produce additional CO emissions, the heating furnace will continue to operate with the primary and secondary fuels and a low excess stack oxygen. However, if the temperature approaches the lower limit (e.g., at or below a heating furnace temperature of - 1350°F), the staged fuel can be shut off, and low CO emissions can be maintained by operating only the primary fuel flame attached to the flame holder inside the burner combustion chamber.

[0120] This method provides for normal operation of a heating furnace in response to changes in fuel (primary and secondary) composition and other system changes such as humidity levels. For example, during operation, the fuel may intermittently, periodically, or continuously change the ratio of the gas mixture that makes up the fuel. For example, the fuel typically comprises a combination of natural gas, ethane, propane, and hydrogen as well as additional heavy hydrocarbons. If the ratio of these components changes, the adiabatic flame temperature of the combustion changes. For example, if the proportion of hydrogen increases, the fuel will burn hotter, and if the proportion of hydrogen decreases, the fuel will burn cooler.

[0121] During the normal burner operation phase 960 of the method, the fuel mixture components are determined during step 962. Additionally, during step 962, the flow rates of the primary and secondary fuels into the heating furnace are measured and tracked. Typically, the fuel flow through the primary fuel nozzle, through the staging fuel nozzle, and through the ignition unit (if in use) is measured. Additionally, if there are other fuel nozzles used in the system, the flow of fuel through these fuel nozzles can also be tracked and measured.

[0122] Then in step 964, the measured data is used to calculate the adiabatic flame temperature (AFT) of the fuel composition for each measured point. In step 966, the experimental data curve of the fuel and the calculated AFT are used to determine the excess air (EXA) level required for each measured fuel composition. Maintaining this EXA level allows the system to minimize the NOx emissions output in the primary combustion zone, even if the fuel gas composition changes intermittently, continuously, or periodically.

[0123] The experimental data curve is an EXA (λ) versus AFT curve. An example of excess air versus AFT is shown as Figure 18 . λ is the ratio of the total air flow through the burner to the stoichiometric air flow. The excess air (EXA) can be expressed as a percentage above the stoichiometric flow rate. For example, if λ is 1.0, then EXA is 0%; if λ is 1.75, then EXA is 75%; if λ is 2.0, then EXA is 100%; and if λ is 3.0, then EXA is 200%. The AFT number is calculated based on the fuel gas composition and the combustion air characteristics. The EXA for each fuel composition is experimentally determined as the target for the lowest possible NOx emissions output. Additionally, experimental data can be used to determine the lowest possible AFT for each fuel composition to minimize NOx emissions while maintaining the AFT sufficient to make the combustion process self-sustaining (stable without an additional constant ignition source).

[0124] The method may include continuously sampling and measuring the varying fuel composition gas, then calculating the adiabatic flame temperature (AFT) (or directly measuring the flame temperature), along with further determining the excess air EXA required to operate the main components of the burner to obtain a minimum NOx emission output.

[0125] In an alternative embodiment, one or more sensors measure the oxygen content in the stack, the NOx and / or CO levels in the stack. Then these measured values can be used instead of EXA (λ) relative to the AFT curve to determine the adjustments to be made to the system in the following steps.

[0126] Due to changes in operating conditions, such as continuous, intermittent, or periodic variations in the fuel composition during heater operation - and thus resulting in changes in the AFT and ultimately the NOx and CO emissions - the next step 968 will be to adjust the primary fuel flow, secondary fuel flow, and / or combustion-air flow so as to keep the total heat released by the fuel combustion in the furnace constant. Thus, the system allows the fuel gas distribution and / or combustion air in each roasting zone within the furnace to be dynamically changed in such a way that the total fuel flow or heat release in the furnace (or heater) does not change (is constant).

[0127] For example, if the fuel composition changes to a higher flame temperature (such as caused by a higher hydrogen content), then with the combustion-air flow required in the primary combustion zone being fixed, the primary fuel flow can be reduced while increasing the secondary fuel flow. Thus, the primary and secondary fuel flows can be adjusted simultaneously in such a way that the total fuel flow to the burner (or heater / furnace) and the total heat released by the fuel combustion do not change; that is, they are constant. Thus, with the combustion-air flow fixed, reducing the primary fuel flow and simultaneously increasing the secondary fuel flow results in an increase in the EXA flow in the primary zone of the burner, which is exactly what is required for hotter burning fuels, such as higher hydrogen-containing fuels, to obtain NOx and CO emissions that do not vary based on the fuel composition.

[0128] When the fuel flow is changed, the oxygen content measured in the heater stack will generally need to be kept within a predetermined range, for example, based on the total gas content in the stack, 1 - 4% (space dry), or 2 - 3% (space dry) or 2.5 - 3% (space dry). Thus, changing the primary and secondary fuel flows may require adjusting the total combustion air in the final step 970 to ensure that the oxygen content in the stack is always within the predetermined range.

[0129] As will be appreciated, the normal burner operation procedure 960 is an ongoing process, with the fuel composition being continuously monitored at step 962 and steps 964 through 970 being performed whenever there is a significant change in the fuel composition; that is, whenever a change in the fuel composition is likely to result in at least a 5% change in NOx emissions, typically at least a 10% change in NOx emissions, and more typically, at least a 15% change in NOx emissions. However, this change can vary depending on the emission target and the set margin for the furnace. Conventional furnaces can vary their NOx emissions by 25% to 50% in a day; however, furnaces using the current systems and methods can be reduced to less than a 5% change in NOx emissions in a day.

[0130] Additionally, as will be appreciated, the fuel regulation can be the reverse of that described above, i.e., a change in the fuel composition may require increasing the primary fuel flow and simultaneously decreasing the secondary fuel flow. For example, when the fuel is changed to a composition that burns cooler than the previous composition, such as when the fuel composition changes to have less hydrogen content, it may be necessary to increase the primary fuel flow and decrease the secondary fuel flow. Additionally, such changes in the fuel flow may also require increasing or decreasing the total combustion air in order to keep the oxygen in the stack within a predetermined range.

[0131] Now referring to Figure 19 , which shows a schematic diagram of a system 972 for performing the above process. System 972 includes a furnace 500 having a stack 504, a plurality of fuel distributors 978, and a computer processing system (CPS) 980. Additionally, furnace 500 includes a burner that typically has components for igniting and burning fuel within the furnace, such components as refractory bricks, fuel nozzles, plenum chambers, etc., which can be according to the above burner embodiments. In Figure 19 , only the plenum chamber 985 of the burner is visible.

[0132] Fuel distributors 978 provide primary fuel (for both the primary fuel injector and the ignition unit) through fuel line 982 and secondary fuel through fuel line 984. Generally, there will be separate fuel distributors for the primary fuel and the secondary fuel so that the fuel flow rates of these can be individually controlled. Additionally, the primary fuel injector and the ignition unit will typically have separate distributors so that the fuel flow rates to them can be individually controlled. Fuel line 982 and / or 984 pass through plenum chamber 985 (which forms part of the burner that is at least partially housed within furnace 500), where combustion air from the plenum can be mixed with the fuel passing through the fuel line, such as by using a mixing tube. Generally, the fuel line 982 for the primary injector will introduce a fuel-air mixture.

[0133] One or more sensors 986 measure the fuel and transmit the resulting data to the CPS 980 to determine the composition of the primary and secondary fuels. One or more sensors 988 and 990 measure the flow rates of the primary and secondary fuels and transmit the resulting data to the CPS 980. In some embodiments, the system 972 uses sensors 992 and 994 to measure the adiabatic flame temperature at various locations within the primary and secondary combustion zones included within the heating furnace 500. In other embodiments, the adiabatic flame temperature is determined by the CPS 980 based on the fuel composition and pre-loaded experimental data. Additionally, the system 972 can utilize a sensor 996 to measure the NOx, CO, and / or excess air levels in the heating furnace bank 504. Various valves and actuators 998 can be used to control the fuel and, in some embodiments, the flow of air into the heating furnace. The CPS 980 can be configured to control the valves and actuators to independently regulate the primary fuel flow, secondary fuel flow, and combustion-air flow. As will be appreciated, the CPS 980 will include computer memory, a computer processing unit, and similar standard computer system components. The CPS is used to calculate various conditions regarding the heating furnace and regulate the flow rates of the primary fuel, secondary fuel, and combustion air. For example, the AFT can be calculated based on the fuel composition, and the amount of air that minimizes NOx can be calculated based on experimental curve data.

[0134] The system 972 correlates measurements, calculations, reference to experimental data, and regulation of the characteristics of the heating furnace system. The system 972 provides continuous sampling and measurement of a continuously varying fuel composition gas (e.g., natural gas, propane, hydrogen), followed by calculation or measurement of the adiabatic flame temperature (AFT) and / or prediction of emissions, while further determining the excess air (EXA) required to operate the burners to obtain a minimum NOx, CO, or other emissions output.

[0135] The above-described systems and methods are applicable to a variety of heating furnace (heater) systems. For example, the systems and methods can be used in a heating furnace system where all of the combustion air is introduced into the burner chamber along with the primary fuel using low flame anchoring.

[0136] The presently disclosed devices, systems, and methods have been described with reference to specific embodiments shown in the figures; however, these embodiments are not intended to be limited to those specific embodiments. It will be apparent to those skilled in the art that the features of one embodiment can be used in one of the other embodiments, provided they do not directly conflict with the elements of another embodiment. For example, Figure 7 The diverging tiles of Figure 7 can be used in combination with any of the other embodiments in the same manner as the specifically disclosed ignition unit. Additionally, for example, Figure 19 illustrates a system for performing the Figure 17 process. AlthoughFigure 19 The central air duct as shown in Figure 6 is not shown, and those skilled in the art will implement the Figure 17 system and method shown in Figure 19 and can be easily adapted to control the flow of air through the central air duct, such as that shown in FIG. 6.

[0137] Although the compositions and methods are described in terms of "comprising", "containing", or "including" various components or steps, the compositions and methods can also "consist essentially of the various components or steps" or "consist of the various components or steps". Whenever a numerical range with a lower and upper limit is disclosed, any number within that range and any included range are specifically disclosed. Specifically, each value range disclosed herein (in the form of "from about a to about b," or equivalently "from approximately a to b," or equivalently "from approximately a - b") should be understood to list every number and range included within the broader value range. Additionally, when the term "about" is used in relation to a range, unless the context indicates another definition for "about" to apply, it generally means plus or minus half of the last significant digit of the range value.

[0138] Furthermore, the terms in the claims have their plain ordinary meaning unless the patentee has otherwise clearly and explicitly defined them. Additionally, the indefinite article "a" or "an" as used in the claims is defined herein to mean one or more of the elements introduced by it. If there is any conflict in the usage of words or terms between this specification and one or more patents or other documents that may be incorporated herein by reference, the definition in this specification shall prevail.

Claims

1. A fuel gas burner device, comprising: A burner tile, comprising: A base; An emission end opposite to the base, the emission end defining an emission outlet; and A wall connecting the base to the emission end and surrounding the emission outlet, the wall extending into a heating furnace and having an outer surface and an inner surface defining a primary combustion chamber, wherein the emission outlet allows flow from the primary combustion chamber to the heating furnace; A plurality of flame holders located within the primary combustion chamber; and A plurality of primary tubes, each primary tube having an outlet end, and wherein each primary tube is configured to introduce a fuel-air mixture into the primary combustion chamber, and the outlet end is positioned relative to the flame holders such that the fuel-air mixture introduced into the primary combustion chamber through the outlet end encounters the flame holders to anchor the flame resulting from the combustion of the fuel-air mixture within the primary combustion chamber, Wherein the wall of the burner tile has an orifice serving as a pressure relief / recycle window, the orifice being placed downstream of the flame holders and, when observed in a plane perpendicular to the direction in which the wall extends, the orifice being placed between the plurality of primary tubes.

2. The fuel gas burner device according to claim 1, wherein the burner is configured such that substantially all of the air introduced into the heating furnace for fuel combustion is introduced through the primary tubes.

3. The fuel gas burner device according to claim 2, further comprising a plurality of secondary fuel nozzles, the secondary fuel nozzles being connected to a fuel gas source and operably associated with the burner device such that secondary stage fuel gas is injected from the outside of the burner tile to a point downstream of the emission outlet of the burner tile.

4. The fuel gas burner device according to claim 3, further comprising a control unit, wherein the amount of fuel introduced through the secondary fuel nozzles can be controlled.

5. The fuel gas burner device according to claim 1, wherein the flame holders are attached to the outlet ends of the primary tubes.

6. The fuel gas burner device according to claim 5, wherein the flame holders have a shape selected from cup-shaped, conical, pyramidal, and cylindrical with perforations.

7. The fuel gas burner device according to claim 1, further comprising an ignition unit, wherein the ignition unit comprises: A riser tube having an inner surface, a first end, and a second end, wherein the second end is within the tile and in fluid flow contact with the primary combustion chamber; A fuel lance having a second end within the riser tube and a first end in fluid flow contact with a fuel supply, wherein the second end has an emission nozzle configured to inject fuel so as to move circumferentially and longitudinally within the riser tube and to be delivered out of the second end of the riser tube into the primary combustion chamber; And An igniter that ignites the fuel-air mixture passing through the second end of the riser tube.

8. The fuel gas burner device according to claim 7, wherein the second end of the riser tube further includes a vortex cup having a curved and divergent wall.

9. The fuel gas burner device according to claim 8, wherein the first end is configured to allow air to enter the riser tube such that fuel from the discharge nozzle is mixed with air passing through the riser tube to produce a vortex air-fuel mixture.

10. The fuel gas burner device according to claim 1, further comprising an ignition unit, wherein the ignition unit includes: A fuel lance having a second end and a first end in fluid flow contact with a fuel supply, wherein the second end is within the primary combustion chamber and has at least one discharge nozzle configured to circumferentially discharge fuel inside the primary combustion chamber along an inner surface of the wall of the tile; and An igniter that ignites the fuel passing through the discharge nozzle.

11. The fuel gas burner device according to claim 10, wherein the ignition unit further includes a riser tube, and the fuel lance is positioned within the riser tube, and wherein the riser tube further includes one or more struts that extend outward from the riser tube toward the inner surface of the wall of the tile, and wherein the struts terminate adjacent the inner surface of the wall in one or more of the discharge nozzles.

12. The fuel gas burner device according to claim 11, wherein the nozzle is located within a cavity formed by a flange on the inner surface of the wall and a ring connected to the flange.

13. The fuel gas burner device according to claim 10, wherein the fuel discharged from the discharge nozzle is in a fuel-air mixture.

14. The fuel gas burner device according to claim 3, further comprising: One or more sensors for measuring the fuel flow rate of the primary fuel introduced through the primary tube and the fuel flow rate of the secondary fuel introduced through the secondary fuel nozzle; One or more valves for controlling the fuel flow rate of the primary fuel and the fuel flow rate of the secondary fuel; and A computer processing system operatively connected to the sensors and valves and configured to adjust the flow rate of the primary fuel and the flow rate of the secondary fuel based on one or more of the composition of the primary and secondary fuels, the adiabatic flame temperature of the primary and secondary fuels, and a measured value of the amount of NOx emissions.

15. The fuel gas burner device according to claim 14, wherein the burner is configured such that substantially all of the air introduced into the heating furnace for fuel combustion is introduced through the primary tube.

16. The fuel gas burner device according to claim 15, wherein the flame holder is attached to the discharge end of the primary tube.

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