MXPA96005152A - Apparatus and method to reduce nox, co, and hydrocarbon emissions when gas combustibles are burned - Google Patents

Abstract

A forced extraction burner apparatus for burning a gaseous fuel while producing low levels of NOx, CO and hydrocarbon emissions comprising: a cylindrical internal burner having a tubular wall; a generally cylindrical body mounted within the tubular wall of the internal burner, an annular flow channel (110) being defined between said body and the internal wall of said tubular section, said channel constituting a throat for oxidizing gases, and having a downstream outlet for the internal burner, means (102, 106) for supplying oxidizing gases to said throat of the internal burner, a divergent refractory brick 116 for said internal burner having its smaller end connected to the outlet of said internal burner, and exiting towards a combustion chamber, a plurality of curved axial swirl vanes 112 being mounted on said annular flow channel of the internal burner to impart swirl movement to oxidizing gases flowing downstream to said throat, fuel gas injection means of the internal burner for the internal burner being provided in said annular channel next to the swirl vanes to inject into the flow of oxidizing gases at an upstream point from said outlet end, an external burner surrounding at least a portion of said internal burner and including a wall separated from the outlet wall of the internal burner to define an external burner flow channel 120 having a downstream outlet end for gases provided to said channel, means for providing a flow of oxidant to the flow channel of the external burner 104, 108, and fuel gas injection means of the external burner 126, 128 for the external burner being provided in said channel of external burner flow, upstream of the outlet end of the external burner

Description

APPARATUS AND METHOD TO REDUCE NOx, CO, AND HYDROCARBON EMISSIONS WHEN BURNING GASEOUS FUELS FIELD OF THE INVENTION This invention relates generally to a combustion apparatus and, more particularly, relates to a burner that combines the advantageous operating characteristics of the burners of the inepial type and to the nozzle, to obtain exhaust emissions. low NOx, CO and hydrocarbons.

BACKGROUND OF THE INVENTION NOx emissions to par + r flames can be created either by means of Zeldevitoh itself (often referred to as thermal NOx) or by the formation of HCN and / or NH3, which can be oxidized to NOx (NOx i stantá eo). Typical calculations show that NOx emissions, measured by the flames of natural gas, are fairly close to one to two orders of magnitude, of the value of the typical nuclear power. l-st? Lndica q? e, and most d \, ^ siciones, 1 -t NOx formation is controlled cin.ticamente.Kinetic calculations indicate that the emissions of Thermal NOx typically, on the important source of MOx for the natural gas lines, creating NOx by means of this guide: N «• 02 - NO + 0 (1.) N •• OH - • = NO - * H (2) 2 • 0 - NO f N (3) Kinetic calculations were performed using a PC version of the CHEMK1N computer program. the calculations using this program have given a valuable insight into the changes in the fuel and air characteristics of the burner, which may reduce the NO's. As the name implies, the thermal NOx can be controlled by regulating the peak flame temperature; and as shown in Figure 1, using kinetic calculations, if the temperature can sufficiently reduce the emissions of NOx of a "true" natural gas flame previously mixed, which operates at an excess of 15% ai re, up to extremely low values (less than 1 ppm on volume). In fact, Figure 1 shows the relationship between thermal NOx and temperature, since, for a pre-mixed natural gas flame, with an excess of oxygen, thermal NOx is the only route through which it can be used. What kind of emission is it from N? "Under appropriate flame conditions, immediate NOx formation can also be important when using natural gas." 171 used kinetic model shows that, under fuel-rich conditions, particularly when the stoichiometry is below about 0.6, both HCN and NH3 can be formed by the reaction of OH with N2 to form HCN and N. These calculations were made using gas and air mixtures with this ornithos ranging from 1.0 to 0. "The model predicted that instant NOx becomes important when the temperature is lower, see figure 2. Below a stequiornetpa of 0.5, almost all the NOx formed is NOx instantaneous. The NOx instant NOx formation regime (as the name implies) is also very fast, being completed almost anywhere from 1 milliliter to a temperature of 1.31 ° 0. Kinetic calculations also indicate that hydrocarbon fragments, in addition to being important for instantaneous NO x, are also important for the formation of tertiary NOx, since they can act as a source of 0 atoms and OH radicals. Kinetic calculations show the importance of hydrocarbon concentration in NOx formation, even under oxidizing conditions. At temperatures below 1, B71 ° C, the predicted emissions of NOx were approximately 4 ppm by volume, after a residence time of 5 thousand 1 second, for a mixture of N2, O2, H2O and CO2, when no hydrocarbons were present, compared to 80 ppm by volume when a combustion of about 1% CH was present in the gas mixture. c.,? the concentration of the presently present methane was reduced to about 11.5%, the concentration of NOx, after 5 mi 11 seconds, was reduced to around 75 ppm by volume. The kinetic model used predicts that the following mechanisms are important: 1. The reaction of CH4 with O2, OH and H to form CH3. 2. The reaction of CH3 with O2 to form CH3O and 0. 3. The reaction of N2 with 0 pair-to form NO and 0. 4. Different reactions to form OH. 5. The reaction of N2 with OH to form NO and NH. Gas burners with low NOx emission have undergone considerable development in recent years, as government regulations have demanded that burner manufacturers comply with increasingly lower NOx limits. Most existing low-NOx gas burner designs have designs mixed into the nozzle. In this approach, the fuel is mixed with the air immediately downstream of the throat (the burner). These designs attempt to reduce NOx emissions by slowing the mixing of fuel and air, by some way of arranging in stages the air or to stage the fuel, combined with the recirculation of the burner gas ("COR"). The delayed mixing can be effective to reduce both the flame temperature and the availability of oxygen and, consequently, to provide a degree of thermal NOx control, however, retarded mixing burners are not effective in reducing immediate NOx emissions and can actually exacerbate immediate NOx emissions. The delayed mixing can also lead to increased CO and total hydrocarbon emissions.There are often stability problems with delayed mixing burners, which limit the amount of GOR that can be injected. ctar in the flame zone. Typically, the GQR levels at which the current burners operate, are at a rate of about 20% recirculated burner gas, with respect to the total flue gas flow. Another additional type of burner with low NOx emission, which has been developed in recent years, is the pre-blended type. In this approach, the fuel gas and oxidizing gases are mixed well upstream of the burner throat, for example, on or before the windbox. These burners can be effective to reduce the emissions of both thermal and instantaneous NOx or immediate. However, problems with the type of burners include the difficulty of applying high air preheat, concerns about flashback and explosions, as well as difficulties in applying the concept to dual fuel burners. . Premixed burners also typically have stability problems at high GOR regimes. In the case of US applications Serial No. 09 ?, 979 and 188,586, from the same inventor as the present one (whose descriptions are incorporated herein by reference), extremely low emissions of NOx, CO and hydrocarbons had been obtained, while maintaining the convenient aspects of a burner - mixing in nozzle. This was achieved by injecting the fuel gas, such as natural gas, in a position that was typical for a nozzle mixing burner, but generating rapid mixing that, in effect, would create pre-rimmed conditions upstream of the ignition point. In said burner apparatus there is provided an outer jacket that includes a wind box and a restricted tubular section, in fluid communication with it. A generally cylindrical body is mounted on the sleeve, axially with and spaced inwardly from the tubular section, so that the annular flow channel or throat is defined in the body and the inner wall of the tubular section. The oxidizing gases are fl uid under pressure from the fall of winds towards the throat and are healed from the outlet end located downstream. A diverging hole is attached to place a burner at the exit end of the throat and define a combustion zone for the burner. A plurality of curved axial vortex spans are mounted in the flume channel to impart swirling action to the oxidizing gases flowing downstream in the throat. Fuel gas injectors are provided in the annular flow channel, near or adjacent to the whirling blades for injecting the combustion gas into the flow of oxidizing gases, at a point upstream of the outlet end. The fuel gas injection means comprises a plurality of spaced gas injectors, each of which is defined by a gas ejection hole and means for feeding the gas. The ratio of the number of holes for ejection of gas with respect to the projected area (i.e. with r-es? Ecto to the cross-sectional area) of the annular flow channel-which is fed with the fuel gas by the medium or injector , is at least 2.152 per square meter. Optionally, one or more turbulence enhancing means may be mounted in the throat, at least on one of the upstream or downstream sides of the whirling blades. These serve to induce turbulence at a fine scale in the flow, to promote the microscale mixing of the oxidant and the combustible gases, before combustion in the hole for the placement of the burner. The gas injectors may be located at the leading or trailing edges of the whirling blades or inject the combustible gas in the direction of the tangential component of the flow imparted by the whirling blades. The gas injectors may also be arranged in a plurality of concentric, hollow rings, which are mounted in the throat, downstream of the whirlwind blades. The injectors may also comprise openings arranged in opposite concentric bands, on the walls defining the internal and external radii of the annular flow channel. The gas injectors can also be located on the surfaces of the whirling blades, the blades being hollow structures, fed by a suitable manifold. Preferably the geometry of the burner is such that the product of the swirl number S and the hole outlet to place the burner, with respect to the ratio of outlet diameter to inlet diameter 0 / B of the hole to place the burner is in the scale of 1 (1 to '3. (1) In accordance with another aspect of the invention of the US applications Serial No. 092,979 and 188,586, a method for injecting gaseous fuel in a forced burner is provided. , of the type that includes an annular groove of outer diameter B, which has an inlet connected to receive a flow of forced air and recirculated burner gases, and an outlet attached to a divergent hole to place a burner. in an axial coordinate that is spaced less than B in the upstream direction, from the axial coordinate at which divergence of the hole begins to place the burner; and sufficient mixing of the gaseous fuel with the air and recirculated burner gases is provided, so that the components mix well to a molecular scale at the axial ignition co-ordinate. This procedure results in low omissions of NOx, CO and hydrocarbons from the burner. In another aspect of the invention of the US applications Serial No. 092,979 and 108,586, the whirling blades that are mounted with their leading edges parallel to the axial flow of the fuel and the oxidizing gases, and then slowly bend to the final angle desired, they have a constant radius of curvature along the curved portion of the blade, so that the curved portion is a section of a cylinder. This form simplifies manufacturing using conventional metal fabrication techniques. A further background, which will be u + il to understand this invention, can be obtained by reviewing figures 3, k, 5, and 6 of the present, which describe a representative mode of the apparatus described in the previous applications of the same inventor. In Figure 3 there is an isometric perspective view of the burner apparatus 51 of said prior art embodiment. That figure can be consigned simultaneously to Figures 4, 5 and 6, which are, respectively, longitudinal section and extreme front and rear views of the apparatus 51. In the burner apparatus 51 the combustion air (which can be mixed with burner gas recirculated) is provided to the wind box 53, to ra "of a cylindrical conduit 55. The wind box 53 joins a tubular section 5 ?, which ends in a flange 59, which is secured to a divergent hole 58 for In the embodiment shown, the inner coaxial cylindrical body 61 consists of a cylindrical hub 63, hollow, central, intended to receive an oil gun or an observation glass, and a surrounding tubular member. or cylinder 65, which is spaced from the outer wall of the tube 63 and is closed at each end by seals 67. A hollow annular space 68 is thus formed between the tubular member 63 and the cylinder 65, which serves as a manifold 68 for the fuel gas that is provided to said space through the connector 69. The cylindrical body 61 is disposed and spaced within the wind box 53 and the tubular section 51, passing it through the flanges, one of which it looks in 71. The latter is secured to a plate 73, at the end of the windbox, by means of bolts 75 and suitable fasteners (not shown). This arrangement allows easy disassembly, for example, to provide service and the like. In the burner arrangement 51 is provided a series of whirling blades 77 in the annular space or throat? 79, which is defined between the tubular body 61 (specifically, in -e the outer wall of the cylinder 65) and the inner wall of the tubular member- 57). At the immediately upstream end of each of the whirling blades 77 is provided a gas injector means, which takes the form of a plurality of tubes 81, each of which is provided with multiple holes 83. It will be apparent that the tubes 81, which are hollow members, are in communication, at their open end, with the interior of the gas manifold 68, defined within the member 65; which serves, therefore, as a power source for the fuel gas. The fuel gas is discharged in the direction of the openings 83, so that, in each case, fuel is injected into the throat directly at the leading edges of the whirling blades and in the direction of the tangential component of the flow imparted. by whirlwind blades 77. Consequently, gas injection also acts to increase the vortex number of the flow. While the invention of the US applications Serial No. 092,979 and 188,586, from the inventor hereof, (hereinafter sometimes referred to as the "basic mixer" or "basic OMR") is extremely effective in obtaining the desired results, the basic OMR design results in a size of burner that is significantly higher than many existing burners. While the burner handle is not inherently important for the fast mixing aspect, the large size of the burner is important to create an extremely stable flame, which permits the use of high burner gas recirculation rates, without concern about the flame becoming unstable. Another limitation of the OMR design is that the burner geometry should be kept circular. This is clearly a limitation in a boiler or furnace using square, rectangular or other burners. When the basic OMR is incorporated into existing furnaces, the larger size, relative to the existing burner, can create significant difficulties and increase the cost of adaptation. Problems with the larger size of the burner are particularly apparent when the burner wall of the boiler or furnace is a "water wall" consisting of pressurized steam or pressurized water pipes. For this type of design the burner openings are made by bending the boiler tubes. Any significant increase in burner size involves bending new tubes to form a larger opening. Large industrial utility and field boilers typically have burners inserted through a pair of water. One method to reduce the size of the burner is to increase the speeds through the burner. Without error, that method has the disadvantage of increasing the pressure drop through the burner. A greater pressure drop through the burner creates adjustment or adaptation difficulties, which include the replacement of forced draft fans, increased operating costs, and associated with the higher operating pressure, the structural limits:. in the wind box and increased operating costs.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the present invention, a two-stage rapid mixing burner design provides an apparatus and method that significantly reduce the size of the burner-of a rapid-mix burner and / or the drop of a burner. burner pressure, at the same time as the fast mixing aspect and the stability of the basic rapid mixing design. The simplicity of the two-stage mixing burner of the invention can also be easily altered to be used in non-circular geometries, such as a burner that is ignited from the corner or tangentially ignited. The present invention uses a basic, circular rapid mixing burner (i.e., as in previous applications by the same inventor), located internally within a larger burner that may be non-circular. The internal burner provides the flow of hot gases that stabilizes the external burner. In effect, the combustion gases produced in the internal burner replace the strong internal recirculation flow, generated by the basic QMRs, as an ignition source for the external burner flow. The interior burner uses the same type of vortex agitator, burner and burner hole geometry, as in the basic burner QfR described in previous applications of the same inventor and, consequently, has the desired stability and desired performance of NOx , CO and HC. The outer portion of the burner uses a fast mixing injection grid and, consequently, also has the desired performance of NOx, 00 and HC. Because or that the stability of the flame is provided by the internal burner, there is no need for the whirling blades or a burner-divergent hole for the outer portion of the burner. The inner burner is circular, with a cylindrical tube mounted in the center that defines an annular space-between the external and internal tubes. A plurality of fixed, curved axial blades are mounted in the annular space to impart the oxidizing gases flowing through the burner to the liquid. The number of blades varies linearly with the diameter of the burner. The typical separation between the blades, in the inner ring, is approximately 2.54 cm. Injection means are provided in the annular flow channel, close to or adjacent to the whirling blades, to inject the combustible gas into the flow of oxidizing gases. The fuel gas injection means comprises a plurality of spaced gas injectors, each of which is defined by a gas injection-bore and a means for feeding gas to it. The proportion of the number of holes for gas injection, with respect to the projected area of the flood channel anu Lar, which is fed with fuel gas by the injector means, is at least 2,152 / m2 »A hole for divergent burner it is attached to the outlet end of the inner burner and defines a combustion zone for the burner. The purpose of the burner hole is to both promote the strong inner flame within the burner, and provide sufficient residence time to allow the flame stability from the internal burner to be relatively unaffected by the outer portion of the burner. burner. Consequently, a hole length / diameter ratio of the burner hole of at least 1.75 is desirable. The gas injectors for the inner burner-may be located on the leading and trailing edges of the whirling blades, and inject the fuel in the direction of the tangential component and / or opposite the direction of the tangential velocity component of the flow imparted pearls whirlwind blades. The gas injectors may also be arranged in a plurality of concentric, hollow rings, which are mounted in the throat, downstream of the whirlwind blades. The injected gas may also comprise openings arranged in opposite concentric bands on the walls defining the internal and external radii of the annular flow channel. You can also place the gas nozzles on the surfaces of the whirling blades, the blades being hollow structures, fed by a suitable manifold. The details of these positions are most commonly found in US applications No. of senes. 092,979 and 188,586, from the same inventor as the present. The inner burner is enclosed by a second annular space or several external burner cells, for which the inner burner acts as a source of ignition.

The air towards the ring or the outer burner regions can be fed either from a separate windbox or from a windbox even to the inner burner and the outer burner. The two most common geometries for the outer burner are in an annular space, concentric to the inner burner, or in a rectangular region with the diameter of the inner burner smaller than or equal to the smallest dimension of the rectangular aperture. However, the basic two-stage QI1R concept can work with other external burner geometries in different ways. Within the region defined by the flow of oxidant to the external burner, fast-mixing gas injectors are provided to provide rapid mixing between the oxidant and the fuel. The gas injectors can adopt the form of radial lighters, fed either from an external manifold or from an internal manifold. The burners are perforated with holes to give the desired speed of mixing between the fuel and the oxidant. The gas injection burners can also take the form of concentric rings, horizontal or vertical grids or other forms compatible with the external burner geometry. Typically, the separation between the gas injection lighters is approximately 2.54 cm, the separation being between the holes drilled within the lighters in the order of 5.08 nm to 10.16 m. The separation of fuel gas injection holes gives a uniform distribution of gas within the oxidant. The cross-sectional area of each gas burner is at least three times the total area of the injection holes in each burner, to provide an adequate distribution of gas to each hole. Typically, if the number of holes in each lighter is greater than 4, preferably a cylindrical t-tube with a diameter of 6.35 min is not used for injection lighters. Instead, oval tubing in the form of a "racetrack", aerodynamic tubes or manufactured injectors, having a maximum width, in a plane defined by the cross-sectional area and the burner throat, of 6.35 mm and a length, normal to the same plane, determined by the required cross-sectional area and the required wall thickness of the tube. The "flattened" faces of these tubes, in such a manner, are the surfaces in which the eye holes are present and, thus, generate the gas ejection direction tangentially to a radius drawn to the hole, and in one or more planes tran e salts to the axis of the burner. With an example of a typical injector design, an injection lighter can have a height of 7.62 cm, with an average gap between holes of 6.35 m (which results in 12 holes.) Using holes of 1.58 inrn, the area Total serious injection of 14.18 ern * If a tube with a 0.88 mm wall is used and the minor axis of the tube is of b.35 mm, it would take a long for the major axis of the tube of at least 15. U7 mm to maintain an area of entry torque to the lighter of at least triple the injection area The ratio of the number of gas injection holes to the projected cross sectional area of the annular flow channel is at least 2.152 / m2 .. The diameter of the holes is determined by the same criteria discussed in previous patent pending applications.Means can be provided to increase the mixing of the gas and the oxidant in the outer portion of the burner These means may include the use of sieves or perforated plates, which induce fine-scale turbulence within the flow, or axial vortex blades can be used in the external flow, both to induce mixing and to control the shape of the flame. The rate of heat input between the internal and external burners is typically in the range of 5% to 20% when the burner is operated at its maximum capacity. In an operation mode, the heat input to the internal portion of the burner would remain fixed and, if a lower heat input is required, the fuel and oxidant regime in the external burner would be reduced only. In extreme cases, the burner could be operated with fuel inlet to the inner portion of the burner only, in which case the burner would function as a common and current OMR. however, if desired, the thermal inputs of the inner and outer burner could be controlled together. That way, the inner burner and burner L9 would be controlled outside, from which the heat input- from both burner portions would vanish limeiinente, that is, if the total input is 50%, both, burner-is, internal and external, would operate at 50% of its maximum capacity. Typically, recirculated burner gas is added (GOR) to the recirculated combustion air of 1 internal burner and of the external burner. The GOR is added far enough, upstream of the burner, to result in pre-mixed air and GOR at the gas injection point. As an alternative to GOR, air or other inert materials can be used to reduce the temperature of Jalarna. The amount of GOR used depends on the desired NOx level. It is also disclosed in the cited US patent applications 092,979 and 188,586, from the same inventor as hereby, that an oil gun can be inserted through the center, along the ee of the inner burner, to provide the capacity of burned oil, backup. When operating with oil, the blades or whirling blades and the burner hole of the inner burner will provide the necessary stability of the flame. All the oil will be injected through the center of the burner, providing the mixed fuel and air mixing (i-ter steps) necessary for the control of NOx with oils that contain a significant amount of combustible nitrogen.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated diagramatically, by way of example, in the accompanying drawings, in which: Figure 1 is a graphic illustration showing the NOx calculated against the adiabatic temperature of the flame, for a pre-mixed flame with 15% excess air. Figure 2 is another graph showing the kinetic calculation of instantaneous NOx (HCN and NH3) - Figure 3 is a perspective view of a burner-like embodiment of the prior art, in accordance with the description of U.S. Patent Applications Serial No. 092,979 and 188,586, of the same invention as the present invention. Figure 4 is a longitudinal sectional view taken through the apparatus of Figure 3. Figures 5 and 6 are respectively front and rear end views of the apparatus of Figures 3 and 4. Figure 7 is a viewed in longitudinal section, turned through a first embodiment of apparatus according to the present invention. Figure 8 is a front end view of the illustration of Figure 7. Figure 9 is seen in longitudinal section, taken through a second embodiment of apparatus in accordance with the present invention.

Figure 10 is a front end view of the apparatus of Figure 9. Figure 11 is a schematic longitudinal sectional view of a two-stage apparatus in accordance with the invention, which is provided with an outer burner portion, rectangle r. Figure 12 is an end view of the apparatus of Figure Ll. Figure L3 is a schematic end view of six burners, as they would appear in a corner of a typical burner application that is lit by the corner. Figure 14 is a graphical illustration showing the effect of varying the ratio of the internal / photal burner heat input, as a function of the GOR regime to ambient air, and also compares the operation of the two-stage OMR with that of the Basic OMR. Figure 15 is a graph showing the emissions of 00 and total hydrocarbon (HCT) as a function of the GOR regime for the two-stage burner of the present invention. Figure L6 is a graph that compares the effect of the total burner heat input / total as a function of the GOR rate for air preheat at 260 ° C. Figure 17 is a graph q? and illustrates an example of operation of NOx, CO and HCT of the invention, as a function of excess air levels. 00 Figure 18 is a graph showing the operation of a burner according to the invention, calculated from the chemical kinetics, co or a function of the stoichiometry of the burner; and Figure 19 is a graph comparing the measured results, which operate a two-stage burner according to the invention, in a shifting mode, operating the fuel-poor burner to 94% excess air, and the burner rich in fuel at 0.63 of estequiornetpa, which maintains a level of excess air, in general, of 10%; with the same burners operating at an excess of 10%.

DESCRIPTION OF THE PREFERRED MODALITIES Figures 7 and 8 illustrate, respectively, a longitudinal sectional view and a front end view of an OMR 100 according to the present invention. This arrangement employs separate wind boxes 102 and 104 for the internal and external portions of the burner. Ai re and GOR (recirculated burner gas) are provided under positive pressure, by means of conventional fan means (not shown) through ducts 106 and 108, to both wind boxes. The mixture of air and burner gas proceeds through the inner burner throat 110 to the torpedo blades 112. The design of the whirling blades and the gas injectors corresponds to the description of the previous requests of the same inventor as the present one. On the attack edge of the whirling blades gas is injected in the same direction as the curvature of the whirling blades; this arrangement being similar to that shown in Figures 3 to 6. The mixture of air, gas, burner gas-, then passes through the whirling blades, resulting in a well-mixed composition at the beginning of the divergence 114 of the burner hole. The ignition of the mixture occurs early in the burner hole 116 and, in the axial position corresponding to the outlet of the burner hole, a significant amount of the fuel is burned. The ignited gases proceed to a combustion bed, which, in use, is connected to the burner, at the outlet of the burner hole. The geometrical design of the interior burner consistent with the design of the basic OMR (see, for example, Figures 3 to 6). The dimensions of the annular region defined by the ratio of the inner diameter of the whirlwind blades, divided by the outer diameter of the whirlwind blades, is preferably on the scale of 0.6 to 0.8. In addition, the product of the vortex number with the output to burner hole inlet ratio, preferably is in the range of 1.0 to 3.0. In order to help isolate the infernal burner flame from the fluids in the outer portion of the burner, the outlet angle 118 of the burner hole would typically be zero degrees. However, burner-hole output angles ranging from more (diverging at the output) to less than zero degrees (converging at the output) may be suitable for some applications. To give adequate residence time within the burner hole, the burner hole length / burner hole outlet diameter ratio should be a minimum of 1.75. The mixture of air and burner gas - comprising the oxidant is also fed to the wind box 104, which feeds the external burner. This oxidant stream is fed to the annular flow region - or channel 120, between the outdoor burner par-ed 122 and the backwardly extending and partially-defining tube 124 of the inner burner. The oxidant passes through two rows 126, 128 of gas injectors, which extend radially towards the flow channel to λ Lar 120 of the external burner. The gas injectors are supplied with fuel gas from the manifold L31, inside which the injectors extend and with which they are in communication. The fuel gas for the manifold 131 is provided through the screw 133. the wall 122 is secured to an outer refractory piece 135, by means of the flange 139. The piece 135 functions essentially as a burner hole, for the external burner . It has a central core 137 which forms part of the flow channel 120. Gas is fed through several injectors in the fixed 126, 128 which extend along the radii. Each radial burner 132 has a plurality of injection holes which inject the normal gas to the flow of oxidant in the same direction as the tangential component provided to the oxidant, using the whirling blades of the inner burner. Nevertheless, the fuel injection opposite to the whirling direction of the inner burner or in both directions simultaneously, are also effective means to produce the desired mixing results. The totality of the gas injection holes, in effect, define a grid of injection points, spaced about 6.35 rn in the radial direction and 1.27 cm in the circumferential direction. The objective is to supply the pre-refurbished i / GOR / busbars before the external burner gases are ignited by the combustion gases of the internal burner. The diameter of the holes is based on the rapid mixing design described in the aforementioned patent applications, of the same inventor as the present one. The outdoor burner gas burners, shown in Figure 7, are aligned in two rows, in order to generate additional mixing energy in the wake of each row. In the apparatus 100 there are two rows of lighters, each of which consists of 20 eylindrical tubes. The tubes in one row are displaced 15 ° from the tubes in the other row. The lighters can be aligned in a single row or in multiple rows. The lighters can take the form of cylindrical tubes, oval tubes or other manufactured forms, which have a small outside diameter, axis about 6.35 mm. The area of cross-sectional area of each gas burner is typically at least three times the total area of the injection holes, in total, in each lighter, to give even gas distribution to each hole. As shown in Figures 9 and 10, the whirlwind blades 134 can be added to the outer annular or flow channel 120. The purpose of the whirlwind blades 134 is to accelerate the mixing between the fuel and the oxidant. The whirlwind blades will also provide a degree of control over the shape of the flame, resulting in a higher whirlpool level a shorter and wider flame. Typically, whirlwind blades are used with an output shaft angle of 30 degrees; but you can use blades with exit angles on the scale of 10 to 50 degrees to control the shape of the flame. The radial lighters 160, in the embodiment of FIGS. 9 and LO, are oval or flattened tubes, in contrast to the cylindrical tubes of FIGS. 7 and 8. Within an outer tube diameter downstream of the gas injectors, the outside burner flow-enter a lefractapa section. The refractory will extend downstream, ending-typically in the same axial position or extending slightly downstream of the inner burner hole. However, the refractory section could be replaced with a cylinder formed from the surrounding water par-ed tubes, if sufficient wall space is not available < 1e water Figures 1 1 and 12 show a two-stage OMR having a rectangular outer burner portion. This geometry corresponds to corner burners (or tangentially produced) that constitute a significant fraction of the market of industrial burners and public services. Figure 13 also shows a view of six burners, as they would appear in a corner of a typical ignition switch appli- cation in the corner. The interior conceptual burner is the same as the two-stage annular burner, described for FIGS. 7 to 10. The burner hole of the internal burner has the same outer diameter as the smaller dimension of the rectangular boundary compressing the outer burner. The gas injection manifold in the external burner consists of a series of vertical, parallel lighters, 6.35 mm wide, and spaced at 2.54 cm l center-to-center. The horizontal lighters, parallel, would be equally effective to generate the desired rapid mixing. The cross sectional area of each vertical injection burner is large enough to give a uniform distribution of gas to each hole in the injector. Typically, the cross-sectional area of each lighter is at least three times the total area of the holes < 1e injection. Each lighter - has a series of holes, spaced at increments of 6.35 mm, with toejo along the same Jel. The gas axis injection burners in the upper and lower burner cells are fed from separate manifolds, located near the upper and lower surface of the external burner. The gas axis injection holes can be on either side of the vertical manifold or on either side, depending on the application. A screen, perforated plate? Another mixing increment may be placed downstream of the gas injectors in the outer burner shaft cells, to increase mixing between the fuel and the oxidant. The objective of the gas distribution system and of any screen or perforated plate, located downstream of the gas injection point, is to generate a pre-mixed fuel and oil, upstream of the ignition point. Experiments were carried out with a burner that had a geometry similar to that shown in figure 11, in a calder-a ele 980.9 KJ, where 0.279 MMc L / sec represents the total load. Vapanelo tests were carried out on the heat input (load) to the burner, in the scale from 0.104 to 0.244 MMcal / sec. The tests were carried out varying the ratio of heat input (.on to the burner i ntepor / t ot to, from 6.6% to 15%.) Tests were carried out with e-ombssion at the temp The ambient temperature is already 260 ° C. The results of the tests varying the proportion of the input of the total / total burner heat, as a function of the GOR regime with air at room temperature, are shown in Figure 14. The stability of the mixer and the NOx, at a constant GOR rate, is not affected, relatively, by the ratio of the input of "heat from 5 internal burner to total burner." Figure 14 compares tarnbLen the OMR burner operation of two stages, rectangular, with normal OMR For GOR regimes of more than apr-or 20%, the two-stage burner has fewer NOx emissions for a given GOR regime, than the burner The normal. Both the two-stage burner and the normal GOR are capable of having NOx axis emissions well below 10 ppm. Figure 15 shows the emissions of CO and total hydrocarbons (HCT) as a function of the GOR regime for the two-stage burner. CuaneJo NOx emissions were obtained from L5 only 5 ppm, both the CO and HCT emissions were below the limit of detection of ppm. Figure 16 compares the effect of the internal / total burner heat input as a function of the GOR regime for air preheating at 260 ° C. Again the NOx emissions and the stability of the two-stage burner were not a marked function of the proportion of heat input between the internal burner and the total burner. For a given GOR regime, above 20% axis, the NOx emissions from the two-stage burner were lower or < - that for the normal QI1R, for a given GOR regime .. The data in figures 17 to 19 show that the two-stage OMR has the ability to reduce NOx emissions well below 10 ppm, with regimes of GOR less than or equal to those used for the normal OMR. Low NOx emissions can be maintained with less than 1 pprn of CO or HCT emissions.

EXAMPLE To illustrate the reduction in burner size, which would result from a two-stage design, the following example is given, in which the burner diameters are compared for a normal annular OMR and a two-stage OMR. Design criteria Maximum input: 6.999 MMcal / sec. Water pressure drop through the burner, at full load: . 32 crn. Air preheating: 260 ° C GOR axis temperature: 260 ° C Excess air: 15% GOR: 20%. Normal QMR: Gauge diameter: 1.01 m Hole diameter of burner hole (expansion hole for burner 1 .5) = 1.52 rn Two-stage QMR: Outside diameter of hole for internal burner : 50. 8 crn (0.699 MMcaL / sec) diameter of external burner = 83.82 crn. The design of ejuemaejor of two stages will result in a maximum burner diameter of 83.82 crn, compared to the maximum diameter of the normal OMR axis, of 1.52 rn, for the same burner capacity, the ism r regimen of GOR and La mi pressure drop, with approximately the same flame stability and emissions of NOx, CO and HCT. Size reduction occurs primarily for two reasons: firstly, since the external burner does not require whirling blades, a higher axial speed can be used for a given pressure drop. Secondly, since the flame in the exterior burner is stabilized with the flame of the interior burner, the expansion of the burner shaft hole for the exterior burner is not necessary. The two-stage OMR burner can also be operated at excess shaft levels in the air to reduce the levels of NOx to extremely low levels, in the same way as a normal OMR. An example of the operation of NOx, CO and HCT of the OMR, as a function of the level of excess air, is shown in Figure 17. Excess air is equally effective (ie the GOR to reduce NOx levels). below 3 ppm, maintaining the omissions of CO and HCT below L ppm, since NOx emissions can be controlled using the OMR equally effectively, using excess air or GOR, a boiler with OMR. The multiple burners can operate in what is commonly referred to as a first axis mode of shifting ignition operation to control NOx emissions Fl flipped ignition means, in? n furnace shaft multiple burners, that some burners operate with enriched air and others with fuel Figure 18 shows the operation of the OMR, calculated from the chemical kinetics, as a function of the burner's stoichiometry, the data of figure 18 shows that, even with preheating of the burner. re, operate a burner about 80% of excess air and another burner to an acid temperature of 0.6, resulting in NOx emissions, from both burners, of less than 10 ppm. Figure 19 compares the results measured by operating a two-burner OMR axis installation, in a shifting ignition mode, with the fuel-poor burner operating at 94% excess air, and the fuel-rich burner operating at 0.63 ele stoichiomet Ría, maintaining a level axis excess air in total axis 10% with the same burners, both operating at 10% excess air. The data in Figure 9 show that, without the GOR, the ignition shifted resulting in a reduction in NOx emissions from 300 ppm to 20 ppm. SL is used GOR, the ignition displaced r eejuce The amount of GOR necessary to obtain 10 ppm of NOx, ejosejo 40% to less than 20%. Although the data shown in Figure 19 come from a normal, two-burner OMR operation, it would be expected-the same operation of the two-stage, multi-burner OMR operation. Although the present invention has been given in detail, in terms of its specific embodiments, it will be understood, in view of the present disclosure, that numerous variations on the invention are now possible, for those skilled in the art, maintaining said variations still within the scope of the teachings of the present. Consequently, the invention should be considered broadly and only limited by the scope and spirit of the claims that follow.

Claims (11)

NOVELTY OF THE INVENTION CLAIMS

1. - A forced draft burner apparatus for burning a gaseous fuel while producing low levels of NOx, CO and hydrocarbon emissions, characterized in that it comprises: a cylindrical inner burner having a tubular wall; a generally cylindrical body, mounted inside the tubular wall of the inner burner; an annular flow flow channel that is defined between the. body and the inner wall of the tubular section; the channel forming a throat for the oxidizing gases, and having an outlet downstream of the inner burner; means for supplying oxidizing gases to the throat of the inner side; a divergent burner hole for the inner burner, which has its smaller end connected to the outlet of the inner burner, and which exits towards a combustion chamber; a plurality of axial, curved whirlwind blades, which are mounted in the annular flow channel of the inner burner, for whirlwind Imparti to the giants that flow downstream in the throat; means for injecting combustible gas from the inner burner, for the internal burner, which are provided in the annular channel next to the whirling blades, for injecting the gas into the flow of oxidizing gases at a point upstream of the end of the burner. s fill, in a manner that results in uniform mixing of the fuel and the oxidant, upstream of the ignition point; the fuel gas injection means for the inner burner comprise a plurality of spaced gas injectors, each of which is defined by a gas injection hole and means for feeding the gas; the ratio of the number of gas injection holes to the cross-sectional area of the annular flow channel of the inner burner being at least 2.152 / m2; an exterior burner that surrounds at least a portion of the interior burner and that includes a spaced wall of the exterior wall of the interior, to define an exterior burner flow channel, having a downstream outlet end, for the gases provided to ejicho canal; means to provide a flow of oxidant to the flow channel of the external burner; and external burner fuel gas injection means, for the outdoor burner, are provided in the exterior burner channel and flow, upstream of the outlet end of the outdoor burner, and comprise a plurality of spaced gas injectors; each of which is defined by a hole eg injection of gas and means to feed it gas; the ratio of the number of gas injection holes, with respect to the cross-sectional area of the flow channel of the external burner, being at least 152 / p >

2. Apparatus according to claim 1, further characterized in that the outer burner has a rect rect cross-section.

3. Apparatus axis according to claim 1, further characterized in that the external burner has a cylindrical cross section,

4. Apparatus according to claim 1, further characterized in that the outdoor burner has irregular cross section.

5. Apparatus according to claim 1, further characterized in that means are provided to pre-flush the burner gases recirculated to the combustion air pair-both of < | inside and outside brakes.

6. Apparatus according to claim 1, further characterized in that the ratio of heat input to the burner? Ntepor / ex < erior, at full load, is on the scale of 5% to 20%.

7. Apparatus according to claim 1, further characterized because the product of the number < The whirlwind and the inlet to burner hole inlet number for the inner burner is in the scale of 1.0 to 3.0.

8. Apparatus axis according to claim 1, further characterized in that the ratio of the inner diameter-ai outer diameter of the whirlwind blades of the inner burner is in the range of 0.6 to 0.8.

9. Apparatus according to claim 1, further characterized in that increased turbulence means are provided in the external burner, to promote fine-scale turbulence within the flow and generate a microscale mixing between the fuel and the oxidant, prior to combustion.

10. Apparatus according to claim 8, further characterized in that swirl vanes are provided in the flow channel of the external burner, to promote mixing and control the shape of the flame.

11. Apparatus according to claim 8, further characterized in that screens or perforated plates are provided in the annular flow channel to promote mixing at the microscale. 1.2.- Apparatus according to claim 1, further characterized in that it has a burner bore length ratio of the inner burner to an exit diameter of .1.75 or more, with a ratio of outlet diameter to burner bore entrance. Approximation 1.5 13. Apparatus according to claim 1, further characterized in that the internal paddle gas injectors are located at the leading edge of the whirling blades and inject the fuel gas countercurrent, concurrent or both countercurrent and concurrent with the direction of the tangent component L of the flow imparted by the whirlwind blades of the inner burner. 14. Apparatus axis according to claim 1, further characterized in that the internal burner gas injectors are located on the trailing edge of the whirling blades and inject the fuel gas countercurrent, concurrent or both countercurrent and concurrent with the direction of the tangential component of the flow imparted by the whirlwind blades of the inner burner. 15. Apparatus according to claim 1, further characterized in that the burner gas injectors are disposed in a plurality of concentric, hollow rings, which are mounted in the throat, next to the bell-shaped blades of the internal burner. 16. Apparatus according to claim 15, further characterized in that it comprises at least two spaced rings; I walk the holes of the outer ring towards the duct e and looking at the holes of the inner ring in distance from the axis; to thereby produce a flow of gas from each ring to eL or ro. 17. Confounding apparatus with claim 1, further characterized in that the fuel gas injection means of the external burner comprises gas burners along the radii of the external burner, the injection holes being oriented for eject combusible gas countercurrent, concurrent, or upstream as concurrent with the vortex direction of the inner burner. 18. Apparatus according to claim 1, further characterized in that the fuel gas injection means of the external burner comprises multiple rows of gas burners, in more than one axial position, along the radii of the annular external burner, the injection holes being oriented to eject the combustible gas countercurrent, concurrent or both countercurrent and concurrent with the swirl axis direction of the interior burner. 19. Apparatus according to claim 1, further characterized in that it has gas injectors par-a to one or more sides of a rectangular external burner. 20. Apparatus according to claim 1, further characterized by the generally cylindrical body, spaced inwardly, axis the tubular section, includes? N liquid fuel injector means that provides, axis that way, to the burner, with capacities of burn gaseous fuel and liquid fuel. 21. Apparatus according to claim 20, further characterized in that the liquid-injector comprises a liquid feeding tube eμj extends along the axis ejel generally cylindrical body; and a nozzle from the end of the tube extending from the outlet extrusion shaft the throat, a hollow cylinder surrounding said tube and which is open at the end toward the nozzle; and said part includes means for diverting the preceding air from the wind box to the hollow cylinder, to provide a stream of air that prevents the coke particles and ash from being deposited on the lni gun? 22. Apparatus according to claim 1, further characterized in that the geometry of one or more of the external burners corresponds to the normal burner openings of an ignition burner in the corner. A method to operate a two-stage, multi-burner QMR furnace, in a shifting ignition mode, where some burners are operated fuel-poor and other burners are operated rich in fuel, resulting in a level of An excess of general oil similar to that present when all burners are operating at the same osteosome 24. A method according to claim 23, further characterized in that it is added e GOR to both burners. 25. A method according to claim 73, further characterized by the fact that GOR is added to the fuel-rich burners only. SUMMARY OF THE INVENTION A forced extraction burner apparatus for burning a gaseous fuel while producing low levels of NO, CO, and hydrocarbon emissions comprises: a cylindrical internal burner b having a tubular wall; A generally cylindrical body mounted inside the tubular wall of the internal burner, an annular flow channel (110) being defined between said body and the internal wall of said tubular section-, said channel constituting a throat for gases 0 oxidant, and having a downstream outlet for the internal burner, means (102, 106) for supplying oxidizing gases to said internal burner throat, a divergent refractory brick 116 even to said inner burner having its smaller end connected to the inner burner. outputting said internal burner 5, and exiting towards a combustion chamber; a plurality of curved axial swirl vanes 112 being mounted in said annular flux channel of the internal quernadoi to impart swirling motion to oxidizing gases flowing downstream to said throat; means for injecting or combusible gas of the internal burner for the internal burner is provided in said annular channel next to the swirling vanes to inject gas into the flow of "oxidant phases"; m a point upstream of said outlet end; an external burner surrounding at least a portion b of said internal burner and including a wall separated from the outlet wall of the internal burner to define an external burner flow channel 1.20 having a downstream outlet end for gases provided to said channel, means for providing a flow of oxidant to it. flow channel of external burner 104, 108; and means for injecting fuel gas from the external burner 126, 128 for the external burner being provided in said channel with external burner flow, upstream of the outlet end of the. burner-external.