MXPA97002053A - Additionally low nox b burner - Google Patents

Abstract

The present invention relates to a burner system for safely burning fuel with oxidant to control flashback, the system of the burner is characterized in that it comprises: a reaction chamber for substantially burning a mixture of fuel and oxidant , the reaction chamber further comprises a plurality of inlets for receiving the mixture, a burner shaft, an outlet for discharging the substantially burned mixture in a shoulder, the burner system further comprising: a plurality of mixing elements for mixing fuel and oxidant in a predetermined ratio to produce the mixture, the mixer elements comprise: a mixer inlet for each of the plurality of mixer elements where the fuel and oxidant are admitted in each inlet of the mixer; mixer for each of the plurality of mixer elements, where each mixer output is connected au The inlet of the respective reaction chamber, where the combustion occurs substantially near the outlet of the mixer, where each outlet of the mixer is located deviated from the center a significant distance from the axis of the burner to provide a flow imbalance in the reaction chamber for recirculating part of the substantially burned mixture within the reaction chamber towards each burner outlet, where the remainder of the substantially burned mixture is discharged from the outlet of the reaction chamber, where the burner system further comprises: at least one space of fuel to supply fuel to each of the plurality of mixer inlets, and at least one oxidant space for commonly supplying oxidant to each of the plurality of mixer inlets.

Description

ADDITIONALLY LOW NOX LOW BURNER FIELD OF THE INVENTION The invention relates to knocking down the NOX in industrial burner systems.

BACKGROUND OF THE INVENTION Nitrogen oxide (NOX) compounds are typically formed during combustion processes comprising high temperatures and other factors that make the combination of nitrogen and oxygen possible. It shows that NOX is an irritant in small quantities and a potential danger to human life in large quantities. It is also suspected that NOX is a significant source of pollution to the environment. In industrial burner systems, particularly those of the type that operate on one million BTU per hour with flame temperatures of approximately 3500 ° F, localized production of NOX can be dangerous. In addition, environmental protection agencies and state governments are controlling contaminants that are discharged from burner systems including those used in industrial furnaces. As these limits are reduced, including those of NOX and CO, it becomes more difficult for the manufacturers and operators of burners to reach these pollution regulations.

In a conventional burner premix system, it is common to mix the fuel and oxidant away from the combustion site in order to create a premix, which then flows into the burner. In the case of flashback, the amount of premix flowing down the mixing site can potentially combust, resulting in a detonation wave traveling back to the combustion site. Such flashback represents a risk to the safety of the staff and a destructive potential for the team. For this reason, these burner systems are typically limited to an explosion limit of the premix in the order of ten million BTU per hour. In pre-mix systems, noise and vibration are increased as the ratio of fuel to oxidant reaches the stoichiometric ratio. There may be a coupling between the external heat transfer rate and the intrinsic reaction ratio of a completely premixed mixture. This phenomenon is referred to as Rayleigh oscillation. It is responsible for the frequently issued "boat engine" sound when pilots are driven along long tubes. While this phenomenon is not a problem in itself, this oscillation may coincide with the natural frequencies in a chamber or explosion room. When this happens, the two friction with each other in a much stronger and violent noise or vibration. This vibration also has potentially destructive consequences. DESCRIPTION OF THE INVENTION The present invention solves the problems associated with prior art systems. The present invention is directed to a burner system for combustion of the fuel with an oxidant. The burner includes a mixer for mixing the fuel and the oxidant in a predetermined proportion. The mixer includes a mixer inlet with a fuel inlet and an oxidizer inlet to admit, respectively, the fuel and oxidant into the mixer. The mixer also includes a mixer outlet to discharge the mixed fuel and oxidant. The combustion occurs at or near the exit of the mixture. The mixer may be one of several mixing tubes, each of which includes respectively the fuel and oxidant inlets. The combustion inputs are each connected to a common fuel plenum, which supplies fuel to each mixer. Similarly, each oxidant inlet is connected to a common oxidizer plenum, which respectively supplies oxidant to each mixer. With the present invention, the mixture is made inside the burner itself, and in this way, the risk of danger due to the recoil of the flame is minimized. With this arrangement, larger burners can be built, which can burn over 200 million BTU per hour. The present invention can also be contemplated as including plural mixer tubes mounted with their mixer outputs defining an inlet to a reaction chamber. The mixing tubes are mounted off center on the axis of the chamber. By arranging the mixers in this way, part of the fuel and oxidant mixed with combustion is recirculated into the chamber in order to ignite the mixture of fuel and oxidant entering the chamber from the mixer outputs. In this way, a uniform flame temperature environment is created, substantially inhibiting NOX production. The reaction chamber may also include a tapered outlet section that further promotes recirculation within the chamber by restricting outward flow from the chamber, further decreasing the flame temperature and hence the production of NOX. Therefore, it is an objective of this invention to reduce the contaminants produced by the burner systems. It is an object of this invention to improve the efficiency and uniformity of combustion temperature of the burner systems. It is an object of this invention to reduce or eliminate the recoil of the flame in the burner systems and in this way increase the safety. It is an objective of this invention to produce a burner having low NOX and CO outputs. It is an objective of this invention to avoid the use of external plenums of gas mixtures in low-contamination burner systems. It is an object of this invention to improve the uniformity in temperature produced by the burner systems. Other objects and a more complete understanding of this invention can be obtained by referring to the following description and drawings in which: DESCRIPTION OF THE DRAWINGS Figure 1 is a longitudinal cross-sectional view of a burner system embodying the invention of the invention. request; Figure 2 is an enlarged partial cross-sectional view of a mixing tube of the preferred embodiment of Figure 1; Fig. 3 is an end view of the mixer taken generally along lines 3-3 of Fig. 1; Figure 4 are a series of transverse longitudinal views of the modified burner systems as Figure 1; and Figures 5, 6 and 7 are longitudinal cross-sectional views of other burner systems incorporating the invention. Figure 8 is an oblique view illustrating the mixing tube according to an alternative embodiment of the present invention. Figure 9 is a detailed view showing the operation of the mixing tube of the alternative embodiment. DETAILED DESCRIPTION OF THE INVENTION The uncovered design of the premix burner with additionally low NOX consists of 2 modules, a mixing section, a reaction chamber / pass gas section. The mixing section provides a highly uniform premix near the flammability limits for the reaction chamber, preferably with an equivalence ratio between .55 and .7, for natural gas as fuel and air as the oxidant. When combustion is made, these poor mixtures produce extremely low NOx emissions. The section of; reaction chamber / pass gas, provides a location for premix combustion, mechanisms to lower excess air throughout the system, and flame molding capacity. In many applications this will be the final incorporation of the burner, however, some specific applications may require a slightly different configuration. The plenum section 20 is for the interconnection of the burner system 10 to the fuel and oxidant supplies for the burner. The fuel inlet 21, in the preferred embodiment discovered, is fed through a fuel connection 22 to a plenum 24 in the mixing section 40 (described below). The plenum 24 serves to uniformly distribute the incoming fuel flow between the individual mixing elements. At the levels described below, this uniform distribution is essential to ensure that a high quality uniform premix is obtained by means of the initial section of the mixture. In the described preferred embodiment, the fuel input at this location is 940-1200 cubic feet per hour of natural gas at the normal pressure of 14"water column at 70 ° F. Other gaseous fuels including propane , air / propane, butane etc., and vaporized liquids such as oil, etc., can be burned in this type of burner.The oxidant inlet 25 is a precursor oxidant source for the burner system 10. This inlet 25 of The oxidant is directly interconnected to the plenum 26, which full of oxidant, in turn, surrounds the mixing section 40 (described later) .The full oxidant serves to evenly distribute the incoming stream between the individual mixing elements. It is essential to ensure that a high quality uniform premix is obtained by means of the initial mixing section When the oxidizer plenum 26 is isolated from the full 22 of the fuel, there is no mixing of the ustible and oxidant in section 20 of the plenary session. This avoids the explosion potential that is present if the oxidant and fuel are present in a plenum or pipe that is co-located separately from the area of actual combustion. By mixing the fuel and the oxidant inside the mixer, near the combustion point, safety is greatly improved, thus allowing the construction of larger burners with fuel capacities over 200 million BTU per hour. In the preferred embodiment discovered, the oxidant is air with normal oxygen at 21% and 16,000 cubic feet per hour at 70 ° F. In the preferred embodiment discovered, the air pressure inside the air plenum 26 is the 10"water column.

Note that if the air inlet 25 is at a temperature other than 70 ° F, described or with a different oxygen content, the volume of the fuel inlet may be reduced or increased as necessary in order to maintain the proper ratio for the primary section 60 of the burner (later described), particularly with respect to the poor flammability limit. The most common way for the oxidant inlet 25 to be at a different temperature would be if the oxidant were pre-heated prior to being mixed with the fuel. This would be caused by the use of a recuperator, as for example, article 300 of Figure 5, which is interconnected between the furnace and chimney 301, by a regenerator or a secondary burner in the air inlet lines, or otherwise as desired. Preferably, the change from environment oxidant to preheated oxidant can be accompanied by two changes of the primary module of the burner. First, as the temperature of the input oxidant rises, a corresponding increase in the temperature of the reaction chamber will occur. To maintain minimum NOX levels, this increase in oxidant temperature would be reduced by a corresponding decrease in the proportion of equivalence in the primary zone. Additionally, a refractory coating would be added to the module to maintain a low temperature of the burner body. For example, if preheated air is arranged at 1000 ° F, 21% 02 for the burner, the ratio of equivalence of the primary zone would be decreased, preferably to .445 of .65 for ambient air. The passage gas passages and the outlet diameter of the reaction chamber must also be modified for optimal burner performance. It is preferred that the temperature preheating mechanisms raise the temperature of the mixture supplied to the burner section with an increase in temperature below the ignition temperature of the fuel / oxidant mixture, (ie usually within the limit of 1200 ° F). This reduces the risk of premature ignition elsewhere than the chamber 60 of the burner. Note that by increasing the oxygen content of the combustion oxidant, air will also increase the adiabatic flame temperature of the primary zone. Similar to the preheated oxidant, this increase in flame temperature can be compensated for by a decrease in the equivalence ratio of the primary zone. The mixing section 40 is designed to provide a uniform concentration of mixed and combustible oxidant at a uniform rate at the head end of the burner section 60 (ie at the ends of both individual mixing tubes) and between the individual tubes of the burner. mixed. It is also designed to avoid the flashback potential of the flame inside the mixer and inside the chamber. The outlet of the mixing section is a uniform oxidizer / fuel mixture having a ratio of the poor flammability limit to 50% of excess fuel from this lower limit. The rate of flammability is described in Theory of Combustion by Forman A. Williams (page 266, also incorporated as an example). This limit is established as follows: "The limits of flammability are limits of composition or pressure over which a mixture of oxidizing fuel can not be put to burn". The flammability limit is a complex function of the fuel composition, oxidant composition, mixing pressure and temperature of the mixture, which can not always be calculated quickly. It is an objective of this invention that the ratio of equivalence of the combustion zone is kept as close as possible to the flammability limit of either side thereof, allowing the control of the reasonable proportion. For this reason, an operating limit for the ratio of equivalence of the primary zone is specified as being between the flammability limit and the midpoint of the flammability limit and the stoichiometric ratio.

This provides reasonable control of the burner system through a variety of explosion limits. The mixing section 40 achieves intimate mixing of both the primary fuel and the oxydant streams such that the resulting mixture has a high degree of uniformity. When the mixers are properly spaced at the inlet of the reaction chamber, the reacted mixture has only minimal levels of NOX. The typical mixing ratios and NOX levels are as follows: Ratio of equivalence NOX emissions .55 2.9 ppm v a 3% 02 .60 4.3 ppm v a 3% 02 .65 6.6 ppm v a 3% 02 .70 10.8 ppm a v 3% 02 Generally, the ratio of equivalence is the proportion of combustion air divided by the stoichiometric proportion of combustion air. In a preferred embodiment of the invention, the mixing section 40 includes a series of eight tubes 41 extending in a circle spaced from the central axis 42 of the burner system 10. Each mixing tube 41 of this embodiment includes an inlet 43, an inspirer 44, a mixer 45 and a discharge 46. All the mixing tubes are fed from a common fuel plenum 24 and a common plenum 30 of oxidant. This avoids the need for multiple plenums or interconnections. The preferred mixers 41 are placed in a common pin circle with sufficient spacing both between the individual mixing ports and between the radii of the collective mixing ports and the center of the circle to provide high levels of recirculation. The preferred mixing section 40 of Figure 1 further provides a flow imbalance to thereby cause reverse flow or recirculation within the section 60 of the described primary burner. This pushes the heat back to the face of the entry location of the incoming fuel oxidizer mixture to facilitate ignition and uniform burning (described later). In a preferred embodiment shown, this location is the discharge of the mixing section 40 at the entrance of the primary section 60 of the burner with the recirculation due, firstly to the arrangement of the mixing tubes 41, described later, within the 40 mixing section. The location of the discharge could be relocated, (for example, even near the exit of the primary burner section as in Figure 7), with other recirculation methods to carry the heat back to the discharge. The reason for this is that the desire to drag the heat back to the discharge is more important than the location of the discharge or the cause of the recirculation, that dragging the heat back promotes self-ignition and cooperates with the stability of the combustion of poor mixtures. As stated below, other types of mixtures, locations and recirculation mechanisms can be employed. The inlet 43 of the mixing tubes 41 is fed directly from the oxidant plenum 26. The oxidant such as air in this manner passes freely through these inlets 43. An inlet section 49 is located between the inlet 43 and the inspirer 44. Section 49 serves to straighten the incoming flow of oxidant and to spread it uniformly through the tube ring 41 mixer. The inspirer 44, itself, includes a series of holes 48 extending through the tubes 23 for the primary fuel plenum 26. In this way, the inspirer 44 utilizes a high fuel exit velocity through the orifices 48 to uniformly draw an oxidant through the inlet section 44 to the inlet 43. Intimate mixing of the fuel and oxidant is presented downstream in the mixing section 45. The annular passage of the mixing section 45 serves two purposes. First, as can be seen in Figure 8, the central part of the mixing section 45 is clogged, and thus the width of the passage of the fluid (and in this way, the effective diameter of the mixing section 45) is smaller. The average diameter of the flow passage is measured between the tube 23 and the mixing tube 41. In this manner, the annular passage increases the length of the mixing tube 41 for the diameter ratio (L / D ratio). In the preferred embodiment, the L / D ratio is approximately 12. It has been found that this ratio is effective to achieve complete mixing of the fuel and oxidant in the shortest possible distance. The annular shape also provides the prevention of flashback of the mixing flame by increasing the flow rate and keeping the passage sizes below the diameter off for the given mixture. In the preferred embodiment discovered, the velocity through the mixing section 45 is approximately 140 feet / s. The mixing section of each mixing tube 41 serves to combine the fuel and the oxidant to provide a mixture of uniform concentration of the two at a uniform rate. This is not only within the individual mixer tube 41, but also occurs between several separate mixer tubes 41. In the preferred embodiment, each mixer tube 41 is a tube about 2"in diameter having a total of 11" in length. The inlet section 49 has a diameter of about 1.25"with the eight holes 48 for each mixer tube having a diameter of .9375". In an alternative embodiment, shown in Fig. 9, the mixing section 45 includes a gas nose 50 mounted within the mixing tube 41, to distribute the gas evenly. The gas nose 50 includes a plurality of holes 52 that are designed to admit fuel into the annular passage. In this incorporation, the air is preferably supplied at a water column pressure of 10. The fuel is supplied at a pressure lower than that of the oxidant, preferably at a water column pressure of 4-5". In order to ensure that the fuel will enter the passage at such low pressure, a plurality of hollow half-cylinder channels 54 are respectively placed adjacent the holes 54, slightly upstream, so as to cover the holes and thus create a low pressure zone within the flow path behind channels 54. In this way, low pressure fuel is allowed to enter the annular passage. With this configuration, channels 54 present obstructions to the air flow, which additionally creates sufficient turbulence to substantially mix the gas with the air. With this embodiment, the entire nose section 50 is frictionally adjusted within the mixer tube 41. Such adjustment by friction allows the safe retention of the nose 50 and also its easy removal for maintenance. The discharge 46 of the mixing section 40 is directly within the primary section 60 of the burner. In the preferred embodiment, in order to provide a reverse recirculation flow to pull the heat back to the mixer, the location of the discharges 46 of the mixing tubes 41 are at the inlet of the primary section 60 of the burner, and are selected to provide an imbalance of the recirculating flow within the reaction chamber. In the preferred embodiment, this is provided by locating the discharge 46 of the mixing tubes 41 off-center at a significant distance from the axis 42 of the burner system 10. This provides the necessary imbalance of flow in the primary section 60 of the burner in order to recirculate the hot gases and in this way draw the heat back to the mixer discharges 46. This facilitates the operation of the burner by self-igniting the fuel and the oxidant and providing the uniform combustion temperatures. The mixing section 40 also works to stabilize the combustion in the primary burner section 60 as well as to cooperate in the recirculation flow in such primary section 60 of the burner. The discharges of each mixing tube 41 also have a location with respect to the surrounding walls 63 of the primary section 60 of the burner. This location is preferably selected to provide a backflow recirculation type back flow along the walls 63. This would cooperate with the autoignition without clamping the walls 63 at high temperatures or creating wall temperature losses (which one wants minimize). The net effect of the recirculation within the primary section 60 of the burner is that the flow of combustible materials having a temperature above the ignition temperature of the incoming mixtures of oxidant and fuel, exists, whose flow passes the entry location of such incoming mixture of oxidant and fuel. Therefore, autoignition, vo-lumens of output, wall leaks and other important factors will be presented. This self-ignition mechanism is self-sustaining (although possibly after the inclusion of a supplement by a pilot 61, the walls 63 of the burner or other storage device or heat additive). Note, again that other mixer designs and locations can be used. For example, in certain applications, particular designs of smaller burners may be employed, an integral mixer feeding several mixing ports through an intermediate plenum and / or pipes, ports in the same pattern or individual mixers in another. , usually large burners. Other designs can be used to provide the described uniform mixture of oxidant and fuel. Other recirculation mechanisms can also be used in order to draw the heat back to the discharge of the mixing section. Two examples are shown in Figures 5 and 6. In Figure 5, a secondary mixer assembly 200 is located near the outlet 65A of the primary section 60A of the burner with the discharge tube 46A of the secondary mixer assembly 200 which is generally directed towards the entrance of such section 60A of the burner. This discharge in the reverse direction recirculates the oxidant and fuel mixture with combustion within the section 60A of the burner. By varying the oxidant and fuel ratio between the main mixer 40 and the secondary mixer 200, oxidant and fuel leveling can be provided. In addition, the fuel gas can also be used in the secondary mixer 200 assembly. In Figure 6, the blender tubes 41B are positioned asymmetrically with respect to a section 60B of the revised burner having a conical silhouette designed to aggressively promote recirculation during combustion. However, recirculation of fuel and oxidizer with combustion is provided within the primary section 60 of the burner and this provides for auto ignition and combustion of the uniform mixture of oxidant and fuel coming from the discharges 46 of the mixing tubes 41 drag the heat to such discharge at a temperature above the ignition temperature of the oxidant and fuel mixture. This cooperates in the complete combustion of the fuel oxidant mixture, something important or close to the poor flammability ratios used in this burner. In order to reduce the vibration associated with Rayleigh oscillation, it is necessary to sufficiently wet the system so that the amplitude of the resonant frequencies are not very high. A high pressure blower, preferably with pressures higher than or equal to 16 osi (ounces per square inch), provides a high level of moisture by supplying a consistent non-pulsating air source. The primary section 60 of the burner is the area where virtually all of the primary combustion for the burner system 10 occurs. The primary section 60 of the discovered preferred burner is designed to have an insulating heat retaining wall with a thermal characteristic to cooperate in maintaining a uniform temperature within the primary section 60 of the burner. In the preferred embodiment, the walls 63 of the chamber also have a thermal mass to cooperate in maintaining a temperature above the flammability limit and more particularly the temperature of the chamber.; ignition of the described gas / air mixture. While this thermal mass could be designed to have properties, such as a mass, sufficient to be used alone to ignite the combustible oxidant mixture in the reaction chamber, it is preferred that other methods of ignition are used. , in the preferred embodiment, mainly the recirculation of the combustion gases. The reason for this is a combination of wanting to have a compact burner (high thermal mass walls add size and insulation demands) as well as a burner adjustment control (For example, high thermal mass walls operate differently in a cold start than when running hot). The inlet diameter of the burner primary section inlet is designed to provide a backflow recirculation of the combustion products back to the oxidizer and fuel inlet mixture to develop and maintain the ignition (the mixture it is also thermally stabilized through the heat transfer of the wall). The preferred primary section of the burner reaches the ignition ignition by operating a pilot burner 61 to provide a heat source having the necessary ignition temperature (and also possibly enrich the mixture with additional fuel to cooperate in the initial ignition. ). The location of the pilot 61 near the axis 42 of the burner facilitates uniform ignition. After the recirculation of the combustion gases back to the inlet is well established to maintain combustion, the pilot is preferably switched off. At this time (about 20 seconds for a cold ignition), the recirculation chamber 64 of the burner established by the location by the mixing tubes 41 in the incorporation maintained a very stable burn in the primary section 60 of the burner. The heat from the walls 63 of the primary section 60 of the burner helps maintain combustion within the primary section 60 of the burner. optionally the pilot 61 can be used for ignition on ignition and then be returned to a poor burn to assist in the continuous ignition of the fuel oxidant mixture or other modified wood as desired. Although the pilot can be included as an ignition then optional supplementary ignition mechanisms can be used for the burner during operation, other sources of heat, for example incandescent conductors. The section 60 of the particular burner shown includes a reaction chamber 62, a circumferential wall 63, an inlet and an outlet 65. The primary section wall 60 of the burner is a highly insulating high temperature wall. This helps the combustion previously established in the primary section 60 of the burner. In the preferred incorporation discovered is designed to maintain the temperature of about 1400-2300 ° F, under the stabilization of combustion within the reaction chamber 62. The wall 63 includes a cylindrical section 66 and the cylindrical outlet 65 interconnected by a tapered section 67. The tapered section 67 provides a gradual contraction in the output of the primary combustion chamber ensuring complete burnout of the premix. The tapered section is also part of the flam modifier section described below. The tapered section 67 provides restriction in the flow of products that suffered chamber combustion. This creates a controlled region within the chamber where the chamber conditions are kept separate from the oven conditions. Recirculation and mixing are inhibited between combustion chamber products and kiln products. In this way the tapered section 67 allows the chamber and ambient temperature to be maintained separately from the furnace. The cylindrical reaction section 66 is the primary combustion area for the burner. This section achieves combustion of the primary fuel oxidant mixture. Poor premix mixtures enter the chamber from the mixers and are initially ignited by a pilot. The stability of the flame is obtained mainly by the recirculation of partially combusted gases that return to the combustible oxidant mixture that enters without combustion. The reaction chamber has an impact on the molding and impulse of the flame. In the uncovered burner system an intermediate flame length and an intermediate speed are created due to the use of a small taper at the outlet of the chamber. This also prevents the flow of any gas from the furnace back into the recirculation paths within the reaction chamber. The parameters of the design of the reaction chamber are the cold flow spatial velocity (14 interchanges / sec), cold flow input velocity mechanism (15/20 '/ s), and hot flow exit velocity (180' / e). Other flame silhouettes can be provided by altering the design of the reaction chamber and more particularly the silhouette of the tapered section. The particular cylindrical section 66 discovered is approximately 8"in diameter and 10" in length. The dimensions of the reaction chamber will be adjusted to the change in volume flow for the calculated stoichiometry, the lateral passage passages and the output ports can also be changed. As established the tapered section 67 serves to facilitate recirculation 64 for the reaction chamber 62 as well as to aid in the flame mold. If desired, section 67 can be omitted. In the preferred incorporation discovered, the tapered section is approximately 4"in total length and an angled taper of 40 ° is included, due to the existence of reduced diameter, the recirculation of gases at 2000/2300 ° F inside the chamber is facilitated. of reaction back to the discharge 46 of the mixing tubes 41. This high temperature recirculation (caused mainly by the mixing section out of balance in the preferred embodiment), in combination with the pilot and the heat in the wall 63 serves to maintain The combustion inside the reaction chamber The outlet section 65 is about 6"in diameter and 1" in length The outlet section 65 is the main outlet of the primary section 60 of the burner. a speed of 35-400 'per second, something like 180' per second in the preferred embodiment through this outlet section 65. The pressure of the outlet 65 of the primary chamber 60 of co mbustión is preferable of column of water of .5 - 4". This proportion of equivalence in chamber 64 of the burner is from .5 to .75 pair natural gas and combustion air. The oxygen content is from 10 to 6.5%. There is a small flame in this outlet section 65 in the preferred embodiment discovered. This flame facilitates ignition with the passing gas (as will be described later). This flame could be eliminated or expanded as desired (along with the gas flow). Note that some unusual circumstances the burner chamber 60 could be used as a furnace. The optional flame modifier section 90 for the burner system is designed to work in conjunction with the primary section 60 of the burner (more particularly in the tapered section 67) in certain selected applications for molding the flame of the bypass gas that burns in the burner. oven 100. For example, flame modifier section 90 shown is a burner tile 91 of approximately 6"in length that has a gradual taper.This burner tile ensures burning in a cold oven (no oven will be needed. hot as in a cold furnace or a steel reheat furnace that could use a system like that in figure 4b.) The purpose of this particular flame modifier section is to clean the carbon monoxide outlet in an oven application cold (could reach 200 parts per million or more in a cold oven, while only 10 parts per million over 1400 ° F.) Section 90 modifier Flame also helps in the recirculation inside the oven as will be described later. In the preferred embodiment discovered, there are a series of secondary gas jets 101 located circumferentially surrounding the outlet 65 of the primary combustion chamber 62. These optional secondary gas jets are used to provide burning within the flame modifier section 90 of the burner and the secondary flame section 100 (described below). This type of combustion is desirable, for example, in heaters, process heating and aluminum castings and maintenance burners. Optional secondary flare section 100 is a location for secondary burning. The preferred embodiment uses the incoming jets to draw the furnace gases back to the burner, thus diluting the combustion. This secondary combustion causes some NOX emissions, but is compensated for by an increase in the heat released from the burner 60. The secondary fuel combustion section may consist of the final tile of the furnace and the jet outlets of the passing fuel. These two characteristics serve three purposes in the combustion system; increase the final release of heat at normal levels of industrial heating (2% 02 in the combustion gas), define the silhouette of the flame and its aesthetic appearance, and provide final control of NOX and CO emissions . The preferred design uses the well-spaced jets of the reaction chamber, angled towards the center line of the burner at 10-15 ° and cuts into the tile section of the furnace. This combination produces both NOX and CO emission levels below 20 ppm v (3% base 02) in a 1600 ° F chamber. The resulting silhouette of flame is compact with a compact diameter and an axial release of heat with ambient air of approximately 1 MMBTU / hr-ft. In the preferred embodiment discovered, the secondary flame section 100 is activated by means of a series of passive fuel (Gas) jets 101 which are located surrounding the outlet section 65 of the burner section 60. The passing fuel jets 101 are fed through a series of tubes 102 from a plenum 103, a plenum fed from their own fuel inlet 105 in the preferred embodiment uncovered. The secondary fuel plenum serves to distribute the fuel stream evenly between the individual passages. This uniform distribution gives the visible balance of the flame and the consistency through the envelope of the flame. This separate gas inlet 105 allows for individual control of the secondary flare section .. These bypass gas jets 101 provide gas (40-700 'per second and 300-600 cubic feet per hour in the preferred embodiment shown) with in order to provide a medium temperature burn (in excess of 1200 ° F in the preferred embodiment shown) inside the oven. They also introduce furnace gases to dilute the combustion process. This establishes the burning of the fuel in the secondary flame section. This eliminates the flame off and reduces the generation of carbon monoxide (it also provides a 3 'flame inside the furnace in the preferred embodiment). The recirculation 94 of the furnace aids in this secondary burning of the flame. In the preferred embodiment discovered, the NOX is substantially 18 ppm, 7 ppm carbon monoxide for an oven temperature of 1600 ° F, and a burner of 2,500,000 BTU. It is preferred that the distance, angle and speed of the passing gas jets 101 be selected such that the burning of the bypass gas is completed at a temperature above 1400 ° F. With lower furnace temperatures, a closer location of the gas jets 101 will be needed for the outlet 65 than in an oven having a temperature above 1400 ° F. In certain situations, such as those capable of taking the direct output of the burner (for example, 8% 02), the secondary jets can be eliminated, and no bypass gas will be used. For example, aggregate dryers typically run at approximately 7% 02 drying in the combustion products. To obtain the lowest possible emissions of NOX, pass gas will be used. Additionally, some manufacturers use an additional combustion chamber to complete the combustion, minimizing the carbon monoxide emissions due to the extinguishing of the flame by the drying process. In these applications, the reaction chamber / pass gas section will not be required. The primary element of the burner will be mounted directly to the combustion chamber, using it as a reaction chamber. The gases from the combustion product can be recirculated to one of the two locations. If it is included with the combustion air, it will result in a decrease in the flame temperature of the adiabatic zone. This must be diverted with a corresponding increase in the proportion of equivalence of the primary zone. Also the dimensions of the reaction chamber and the pass gas port should be changed to accommodate the difference in flow velocities. The second option for the addition of product gases is through the pass gas ports. If this method is used, the changes must be made to the pass gas supply passages and to the exit ports. In addition, by providing reduced levels of NOX emissions, the present invention also provides a highly significant level of security. Numerous factors contribute to improved levels of safety, including flame retardant control, the relatively small capacity of each mixer tube in the burner, and the small volume of fuel and oxidant mixture between the mixing site and the combustion site inside each tube. These advantages and others provide significant advantages over previous burner systems. Although the invention has been described in its preferred form with a certain degree of particularity, it should be noted that numerous changes can be made without deviating from the invention as will be claimed later. As an example, although a particular design of a mixing tube 41 is discovered from the mixing section 40, other mechanisms of uniformly inter-mixing the fuel and combustion air can be used instead. As a further example, although the primary section 60 of the burner is disclosed as having a tapered section 67 interconnecting with the cylindrical section 66 and outlet 65, and the flame modifier section 90 has a tapered section 91, another type of diameter reduction It can be used including an abrupt transition. Other modifications are also possible to fit several applications.

Claims (27)

1. NOVELTY OF THE INVENTION Having described the invention, it is considered as a novelty, and therefore, the content of the following clauses is claimed as property. CLAUSES 1. A burner system for combustion of fuel with an oxidant, said burner system consists of: a reaction chamber having an inlet and an outlet; a mixing assembly for mixing the fuel with the oxidant in a predetermined proportion including: a plurality of mixing tubes located around the axis of the reaction chamber and spaced therefrom at the inlet thereof, wherein the oxidant and fuel are mixed are provided at the entrance; wherein the mixing tubes are arranged to recirculate part of said fuel and oxidizer already mixed with combustion within said reaction chamber to maintain a temperature at the inlet of the chamber greater than the autoignition temperature of said oxidizer and fuel mixed with said reaction chamber, so as to ignite said oxidizer and fuel mixed in said reaction chamber to produce combustion wherein the remainder of said fuel already mixed with combustion is discharged outside said outlet of said chamber. reaction.
2. 2. The burner system of clause 1, wherein each of the mixing tubes has an annular cross-section with an effective diameter where the flashback is inhibited.
3. 3. The burner system of clause 1, which also consists of secondary passing jets, located in the vicinity of the outlet of the reaction chamber, to provide secondary fuel to the fuel and oxidant mixture already with combustion passing outside of the exit.
4. 4. The burner system of clause 1, wherein the passage jets are configured to induce the gases products of the furnace within the secondary fuel.
5. 5. The burner system of clause 1, wherein the secondary fuel of the secondary jets of bypass gas has a flow velocity of 40-700 feet per second.
6. 6. The burner system of clause 1, wherein the predetermined proportion of the mixed fuel and oxidant has an equivalence ratio between the flammability limit and the stoichiometric ratio.
7. 7. The burner system of clause 1, wherein said fuel is natural gas and said oxidant is air, wherein the predetermined proportion of air and natural gas mixed at room temperature has an equivalence ratio of .53 to .795 .
8. 8. The burner system of clause 1, which also consists of a flame modifier section, located between the outlet of the reaction chamber and the furnace, where the silhouette of the flame inside the furnace is modified.
9. 9. The burner system of clause 1, wherein the reaction chamber has chamber walls having a thermal mass and of sufficiently high insulation so that the chamber temperature is maintained at a temperature sufficient to produce the autoignition of the oxidant and mixed fuel.
10. 10. The burner system of clause 1, which also consists of an ignition arrangement that includes a pilot burner.
11. 11. The burner system of clause 1, where the oxidant is air.
12. 12. The burner system of clause 1, wherein the oxidant is air enriched with oxygen up to 50% of 02.
13. 13. The burner system of clause 1, wherein the oxidant temperature is elevated by a pre-heater.
14. 14. The burner system of clause 1, where it is a stale air stream of reduced oxygen.
15. 15. The burner system of clause 1, where the fuel is natural gas.
16. 16. The burner system of clause 1, wherein the fuel is a gaseous hydrocarbon fuel.
17. 17. The burner system of clause 1, wherein said outlet of the chamber has a smaller diameter than an inner diameter of the reaction chamber, and has a substantially tapered section from the inner diameter of the chamber to the outlet, wherein said tapered section prevents mixing between the combustion chamber products and the kiln products.
18. 18. A burner system for combustion of a fuel with an oxidant, said burner system comprising: a mixing tube for mixing the fuel and the oxidant in a predetermined proportion; a mixing inlet including a plurality of entries selected from the group consisting of a fuel inlet to admit the fuel into the mixing tube, and an oxidant inlet to admit the oxidant into the mixing tube, said inlets being displaced the one of the other inside the mixer; a mixing outlet for discharging the mixed fuel and oxidant wherein the combustion occurs substantially close to the mixing outlet.
19. 19. The burner system of clause 18, wherein the predetermined proportion of the mixed fuel and oxidant has an equivalence ratio between the flammability limit and the stoichiometric ratio.
20. 20. The burner system of clause 19, wherein said fuel is natural gas and said oxidant is air, wherein a predetermined proportion of the air and natural gas mixed at an ambient temperature has an equivalence ratio of .53 to .795 .
21. 21. The burner system of clause 18, wherein the mixing tube is one of several mixing tubes, each with respective fuel and oxidizer inlets, and wherein each fuel inlet is connected to at least one plenum. of fuel and each oxidant inlet is connected to at least one full of oxidant.
22. 22. A burner system for combustion of fuel with oxidant, said burner system comprising: a plurality of mixing tubes for mixing the fuel and the oxidant in a predetermined ratio; a mixing inlet for each of the plurality of mixing tubes wherein the fuel and the oxidant are admitted within each mixing inlet, - a mixing outlet wherein the combustion is substantially present near the mixing outlet; at least one full of fuel to commonly supply the fuel to each of the plurality of mixing inlets, and at least one full of oxidant to commonly supply the oxidant to each of the pluralities of the mixing inlets.
23. 23. The burner system of clause 22, wherein the predetermined proportion of mixed air and natural gas has an equivalence ratio between the flammability limit and the stoichiometric ratio.
24. 24. The burner system of clause 23, wherein said fuel is natural gas and said oxidant is air, wherein a predetermined proportion of the air and natural gas mixed at an ambient temperature has an equivalence ratio of .53 to .795 .
25. 25. A method for making safe combustion of a fuel / oxidant mixture in order to control the flashback of the flame, said method comprising the steps of: a) supplying the fuel to a full fuel within a burner system; b) supplying oxidant to a full oxidant within a burner system; c) maintain a separation between the fuel and oxidant external to the burner system; d) providing a plurality of mixing elements having an inlet and an outlet; e) admitting oxidant into each of the mixing elements from the oxidizer plenum through the mixing inlet; f) admitting fuel within each of the mixing elements from the fuel plenum through the mixing inlet in a position displaced from the position where the oxidant is admitted; g) mixing the oxidant and the fuel at a predetermined ratio within of the mixing elements in order to produce an oxidant / fuel mixture, wherein the total volume of the oxidant-te / fuel mixture is divided by the mixing elements, thereby reducing the total potential flashback of the flame, - h ) maintain fuel and oxidant flow rates within each mixing element at speeds higher than the flame velocity during mixing within each emixer; and i) combustion of the fuel / oxidant mixture substantially near the outlet of the mixer where the combustion site is close to the mixing site.
26. 26. The burner system of clause 25, wherein the predetermined proportion of mixed air and natural gas has an equivalence ratio between the flammability limit and the stoichiometric ratio.
27. 27. The burner system of clause 27, wherein said fuel is natural gas and said oxidant is air, wherein a predetermined proportion of the air and natural gas mixed at an ambient temperature has an equivalence ratio of .53 to .795 .