1. A cyclone flue gas recirculation gas burner, comprising:

the section of the nozzle is annular;

the gas gun central tube is arranged in the nozzle and is an annular cavity, an outer air flow channel is formed in an area between the outer wall of the gas gun central tube and the inner wall of the nozzle, a central air flow channel is formed in an area between the inner walls of the gas gun central tube, and a first gas nozzle is arranged on the wall, close to the combustion end, of the gas gun central tube;

the gas spray gun is communicated with the gas gun central pipe through a branch pipe, the gas spray gun is an annular cavity, the gas spray gun is arranged between the gas gun central pipe and the inner wall of the nozzle, and a second gas spray head is arranged on the wall, close to the combustion end, of the gas spray gun;

the outer flue gas injection unit comprises an outer flue gas inlet and a deflection wall, the outer flue gas inlet is formed in the wall, close to the combustion end, of the spout, one end of the deflection wall is connected with the inner wall of the spout, the deflection wall extends in the direction towards the combustion end, and an outer flue gas circulation chamber is formed among the outer flue gas inlet, the deflection wall, the outer wall of the gas spray gun and the inner wall of the spout;

the inner flue gas injection unit comprises an annular baffling wall and an annular plate, one end of the annular baffling wall is connected with the inner wall of the gas spray gun, the annular baffling wall extends along the direction towards the combustion end, the annular plate is connected with the inner wall of the gas spray gun through a rib plate, the annular plate extends along the direction towards the combustion end, and an inner flue gas circulation chamber is formed among the annular baffling wall, the annular plate, the inner wall of the gas spray gun and the outer wall of the central tube of the gas spray gun;

a firing gun assembly disposed in said central air flow passage adjacent said combustion end;

and the swirl blades are arranged in the central air flow channel close to the combustion end and are connected with the inner wall surface of the central tube of the gas gun.

2. The swirling flue gas recirculation gas burner of claim 1, wherein said baffle wall is a trapezoidal baffle wall comprising a slanted wall surface and a horizontal wall surface.

3. The swirling flue gas recirculation gas burner of claim 2, wherein an angle α between the inclined wall surface and a wall surface line of the nozzle is 20-45 °.

4. The swirling flow flue gas recirculation gas burner of claim 1, wherein an angle β between a leeward side of the annular baffle wall and an inner wall surface line of the gas lance is 15-45 °.

5. The swirling flue gas recirculation gas burner of claim 1, wherein said first gas burner comprises an outer nozzle and an inner nozzle, said outer nozzle being provided on an outer wall of said gas gun center tube, said inner nozzle being provided on an inner wall of said gas gun center tube.

6. The swirling flue gas recirculation gas burner of claim 5, wherein said outer and inner jets are provided at opposite positions of said gas gun central tube, said outer and inner jets being evenly distributed circumferentially.

7. The swirling flue gas recirculation gas burner of claim 1, wherein said secondary gas burner comprises a side jet hole provided on a side wall of said gas lance and an angled jet hole provided on a front wall of said gas lance.

8. The swirling flue gas recirculation gas burner of claim 7, wherein the injection angle θ of said inclined nozzle holes is 25-45 °.

9. The swirling flue gas recirculation gas burner of claim 1, wherein an angle between the swirling vanes and an inner wall surface of the central tube of the gas gun is 30-60 °.

10. The swirling flue gas recirculation gas burner of any of claims 1-9, wherein said gas lance central tube and said gas lance are concentric annular cavities.

Background

The gas fuel burner is a device for burning gas fuel and providing heat or hot flue gas, and is widely applied to combustion devices such as gas boilers, hot blast stoves and the like. Gaseous fuels, such as natural gas, coal gas, pyrolysis gas, etc., have main pollutants after combustion, namely nitrogen oxides and sulfur dioxide. The formation of sulphur dioxide is mainly determined by the sulphur content of the fuel, while the formation of nitrogen oxides is closely related to the design of the burner. In recent years, the environmental protection requirement of combustion equipment in China is more and more strict, taking a gas boiler as an example, the emission standard of boiler atmospheric pollutants (DB11/139-2015) is promulgated by Beijing City, and the emission concentration of the atmospheric pollutants of the newly-built boiler is required to be not higher than 30mg/Nm³(conversion to 3.5% exhaust gas O)₂Concentration). This presents new challenges to the combustor technology of gaseous fuels.

The original emission of nitrogen oxides is generally 70-120 mg/Nm under the condition that the conventional mainstream non-premixed low-nitrogen combustor technology is not put into a flue gas recirculation technology³The initial emissions of a few burners can reach less than 30mg/Nm after the flue gas recirculation technique is used³Emission standard of nitrogen oxides. However, when a high proportion of flue gas recirculation is used, many burners suffer from unstable flames, oscillations, flameouts, etc. due to the reduced combustion flame temperature, which presents a significant risk to the operation of the combustion plant. Other premixed combustion technologies, such as surface combustion, porous medium combustion and the like, can realize the emission of nitrogen oxides less than 30mg/Nm on the premise of ensuring stable combustion³. However, premixed combustion technology requires that the fuel and air be thoroughly mixed prior to combustion, which may be the case if not done properlyExplosion can occur, which brings great potential safety hazard. On the other hand, industrial production often requires that low-heating value fuel gas, such as coal gas, industrial synthesis gas, and syngas, etc., be selected as fuel according to local conditions. Because of the low heating value of these low heating value fuels and the low flame temperature, greater problems arise in stability during low nitrogen combustion. Therefore, there is a strong need in the market to develop a low-nitrogen burner, which can effectively control the generation of nitrogen oxides through the technologies of swirl combustion and flue gas recirculation combustion while ensuring stable combustion.

Disclosure of Invention

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, the invention aims to provide a rotational flow flue gas recirculation gas burner, which realizes that the discharge amount of nitrogen oxides is less than 30mg/Nm on the premise of ensuring stable combustion³Thereby meeting increasingly severe environmental protection standards.

The invention provides a rotational flow flue gas recirculation gas burner. According to an embodiment of the invention, the swirling flue gas recirculation gas burner comprises:

the section of the nozzle is annular;

the gas gun central tube is arranged in the nozzle and is an annular cavity, an outer air flow channel is formed in an area between the outer wall of the gas gun central tube and the inner wall of the nozzle, a central air flow channel is formed in an area between the inner walls of the gas gun central tube, and a first gas nozzle is arranged on the wall, close to the combustion end, of the gas gun central tube;

the gas spray gun is communicated with the gas gun central pipe through a branch pipe, the gas spray gun is an annular cavity, the gas spray gun is arranged between the gas gun central pipe and the inner wall of the nozzle, and a second gas spray head is arranged on the wall, close to the combustion end, of the gas spray gun;

the outer flue gas injection unit comprises an outer flue gas inlet and a deflection wall, the outer flue gas inlet is formed in the wall, close to the combustion end, of the spout, one end of the deflection wall is connected with the inner wall of the spout, the deflection wall extends in the direction towards the combustion end, and an outer flue gas circulation chamber is formed among the outer flue gas inlet, the deflection wall, the outer wall of the gas spray gun and the inner wall of the spout;

the inner flue gas injection unit comprises an annular baffling wall and an annular plate, one end of the annular baffling wall is connected with the inner wall of the gas spray gun, the annular baffling wall extends along the direction towards the combustion end, the annular plate is connected with the inner wall of the gas spray gun through a rib plate, the annular plate extends along the direction towards the combustion end, and an inner flue gas circulation chamber is formed among the annular baffling wall, the annular plate, the inner wall of the gas spray gun and the outer wall of the central tube of the gas spray gun;

a firing gun assembly disposed in said central air flow passage adjacent said combustion end;

and the swirl blades are arranged in the central air flow channel close to the combustion end and are connected with the inner wall surface of the central tube of the gas gun.

According to the cyclone flue gas recirculation gas burner disclosed by the embodiment of the invention, firstly, an inner flue gas circulation chamber is formed among the annular baffling wall, the annular plate, the inner wall of the gas spray gun and the outer wall of the central tube of the gas gun, wherein an air flow channel with a throat part is formed between the annular baffling wall and the outer wall of the central tube of the gas gun, and a baffling gap is formed between the annular plate and the inner wall surface of the gas spray gun; the combustion-supporting air flow can accelerate when passing through the air flow channel with the throat and the baffling gap, a low-pressure area is formed, so that high-temperature flue gas near a nozzle for ejecting a gas spray gun sequentially flows through the baffling gap and the air flow channel with the throat to the outlet end of a central pipe of the gas gun (namely the position of a fuel nozzle of the central pipe of the gas gun), so that the high-temperature flue gas flows through an inner flue gas circulation chamber and is mixed with combustion-supporting air in the inner flue gas circulation chamber, the oxygen concentration of the combustion-supporting air is reduced while the combustion-supporting air is heated, the generation of nitrogen oxides is effectively inhibited, and the flame stability is improved. In the second place, the first place is,an outer flue gas circulation chamber is formed among the outer flue gas inlet, the deflection wall, the outer wall of the gas spray gun and the inner wall of the nozzle, wherein the outer flue gas inlet enables an outer air flow channel to be communicated with a hearth outside the wall surface of the nozzle to suck outer flue gas, and the air flow channel among the deflection wall, the inner wall of the nozzle and the outer wall surface of the gas spray gun forms a throat part; when the combustion-supporting air flow passes through the throat, the air flow speed at the throat is increased, and a low-pressure area is also formed, so that the flue gas sucked into the hearth through the outer flue gas inlet is mixed with the combustion-supporting air in the outer flue gas circulation chamber, the oxygen concentration of the combustion-supporting air is diluted, the temperature of the main combustion area is reduced, and the emission of nitrogen oxides is reduced. Thirdly, the swirl vanes strengthen the mixing of the central gas and the central combustion air, and the combustion air and the gas are uniformly mixed due to the swirl action of the swirl vanes near the gas outlet of the central tube of the gas gun, thereby enhancing the combustion stability and achieving the effect of stable combustion. Fourthly, set up gas shower nozzle on gas gun center tube and the gas spray gun respectively, can strengthen the connection of flame between central flame and the main burning torch effectively, guarantee combustion stability effectively. Therefore, when natural gas is used as fuel, under the condition of ensuring the output of the boiler, the mass ratio of the smoke which can be sucked by the inner smoke circulating chamber and the outer smoke circulating chamber to the combustion air is up to about 0.2:1, the temperature of the combustion air can be effectively improved, and the oxygen concentration of the combustion air is reduced; in the range of 30-100% of boiler load, the combustion is stable, and the phenomena of flameout or combustion oscillation do not occur; when external Flue Gas Recirculation (FGR) is not used, the emission of nitrogen oxides is 50-60 mg/Nm³(ii) a When the proportion of the flue gas recirculation is higher than 18 percent in cooperation with the external flue gas recirculation technology (FGR), the emission of nitrogen oxides can be controlled to be 30mg/Nm³The combustion is stable and no flame-out phenomenon occurs.

In addition, the cyclone flue gas recirculation gas burner according to the above embodiment of the present invention may further have the following additional technical features:

in some embodiments of the invention, the baffle wall is a trapezoidal baffle wall comprising an inclined wall surface and a horizontal wall surface.

In some embodiments of the present invention, an angle α between the inclined wall surface and a wall surface line of the nozzle is 20 to 45 °.

In some embodiments of the invention, an included angle β between a leeward side of the annular baffle wall and an inner wall surface line of the gas spray gun is 15-45 °.

In some embodiments of the invention, the first gas burner includes an outer nozzle disposed on an outer wall of the gas gun center tube and an inner nozzle disposed on an inner wall of the gas gun center tube.

In some embodiments of the invention, the outer nozzle orifices and the inner nozzle orifices are arranged at opposite positions of a central tube of the gas gun, and the outer nozzle orifices and the inner nozzle orifices are uniformly distributed along the circumference.

In some embodiments of the present invention, the second gas burner includes a side nozzle hole provided on a side wall of the gas torch and an inclined nozzle hole provided on a front wall of the gas torch.

In some embodiments of the present invention, the injection angle θ of the inclined injection hole is 25 to 45 °.

In some embodiments of the invention, the included angle between the swirling vanes and the inner wall surface of the central tube of the gas gun is 30-60 degrees.

In some embodiments of the invention, the gas gun central tube and the gas gun are concentric annular cavities.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a schematic structural diagram of a cyclonic flue gas recirculation gas burner according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of an external flue gas recirculation chamber according to an embodiment of the invention.

FIG. 3 is a three-dimensional schematic view of a baffle wall according to an embodiment of the invention.

FIG. 4 is a schematic view of an internal flue gas recirculation chamber according to an embodiment of the present invention.

FIG. 5 is a schematic view of a gas burner head of a gas burner gun according to an embodiment of the present invention.

Fig. 6 is a schematic view of a gas burner head of a central tube of a gas gun according to an embodiment of the present invention.

In the figure: 1-furnace wall; 2, a nozzle; 3-a gas spray gun; 4-central tube of gas gun; 5-a firing gun assembly; 6-swirl vanes; 7-external flue gas inlet; 8-baffle wall; 9-annular baffle wall; 10-a ring plate; 11-side spray holes; 12-inclined spray holes; 13-outer spout; 14-inner spout; a-an external air flow channel; b-a central air flow channel; c, an outer flue gas circulation chamber; d, an inner flue gas circulation chamber.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", and the like, indicate orientations and positional relationships based on the orientations and positional relationships shown in the drawings, and are used merely for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the device or element so referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, should not be construed as limiting the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

The invention provides a cyclone flue gas recirculation gas burner, which comprises the following components in part by weight with reference to the attached figure 1: the device comprises a nozzle 2, a gas gun central pipe 4, a gas spray gun 3, an outer flue gas injection unit, an inner flue gas injection unit, an ignition gun assembly 5 and swirl vanes 6. A swirling flue gas recirculation gas burner according to an embodiment of the present invention is further described in detail below.

In the embodiment of the present invention, referring to fig. 1, the nozzle 2 having a circular cross section, the nozzle 2 extending into the furnace through the furnace wall 1, the rear end of the nozzle 2 being connected to a wind box (not shown in the drawings) for supplying air required for combustion.

In the embodiment of the invention, referring to fig. 1, a gas gun central tube 4 is arranged in a nozzle 2, the gas gun central tube 4 is an annular chamber, an outer air flow channel a is formed in a region between the outer wall of the gas gun central tube 4 and the inner wall of the nozzle, a central air flow channel B is formed in a region between the inner walls of the gas gun central tube 4, and a first gas nozzle is arranged on the wall of the gas gun central tube 4 close to a combustion end. In the embodiment of the present invention, the specific number of the first gas nozzles is not particularly limited, and may be set by those skilled in the art according to actual needs.

According to an embodiment of the present invention, referring to fig. 6, the first gas nozzle comprises an outer nozzle 13 and an inner nozzle 14, the outer nozzle 13 is disposed on the outer wall of the gas gun center tube 4, and the inner nozzle 14 is disposed on the inner wall of the gas gun center tube 4. Therefore, the connection of the flame between the central flame and the main combustion torch is further effectively enhanced, and the combustion stability is effectively ensured.

According to a further embodiment of the invention, the outer nozzle 13 and the inner nozzle 14 are arranged opposite to each other on the central tube 4 of the gas gun, and the outer nozzle 13 and the inner nozzle 14 are circumferentially and uniformly distributed. Therefore, the connection of the flame between the central flame and the main combustion torch is further effectively enhanced, and the combustion stability is effectively ensured.

In the embodiment of the invention, referring to fig. 1, a gas spray gun 3 is provided, the gas spray gun 3 is communicated with a gas gun central tube 4 through a branch tube, the gas spray gun 3 is an annular chamber, the gas spray gun 3 is arranged between the gas gun central tube 4 and the inner wall of the nozzle, the gas gun central tube 4 and the gas spray gun 3 are concentric annular cavities, and the gas spray gun passes through the outlet end of the nozzle and enters the hearth. And a second gas nozzle is arranged on the wall of the gas spray gun 3 close to the combustion end. In the embodiment of the present invention, the specific number of the second gas nozzles is not particularly limited, and may be set by those skilled in the art according to actual needs.

According to another embodiment of the present invention, referring to fig. 5, the second gas burner includes a side nozzle hole 11 and an inclined nozzle hole 12, the side nozzle hole 11 is provided on a side wall of the gas torch 3, and the inclined nozzle hole 12 is provided on a front wall of the gas torch 3. Therefore, the connection of the flame between the central flame and the main combustion torch is further effectively enhanced, and the combustion stability is effectively ensured.

According to another embodiment of the present invention, the injection angle θ of the inclined nozzle 12 is 25 to 45 °. Therefore, the connection of the flame between the central flame and the main combustion torch is further effectively enhanced, and the combustion stability is effectively ensured.

In the embodiment of the present invention, referring to fig. 1 and 2, the outer flue gas injection unit includes an outer flue gas inlet 7 and a deflection wall 8, the outer flue gas inlet 7 is disposed on a wall of the nozzle close to the combustion end, one end of the deflection wall 8 is connected to an inner wall of the nozzle, the deflection wall 8 extends in a direction toward the combustion end, and an outer flue gas circulation chamber C is formed between the outer flue gas inlet 7, the deflection wall 8, an outer wall of the gas spray gun 3 and the inner wall of the nozzle. Therefore, the outer flue gas inlet 7 enables an outer air flow channel to be communicated with the hearth outside the wall surface of the nozzle to suck the outer flue gas, and the air flow channel among the deflection wall 8, the inner wall of the nozzle and the outer wall surface of the gas spray gun 3 forms a throat part; when the combustion-supporting air flow passes through the throat, the air flow speed at the throat is increased, and a low-pressure area is also formed, so that the flue gas sucked in the hearth through the outer flue gas inlet 7 is mixed with the combustion-supporting air in the outer flue gas circulation chamber C, the oxygen concentration of the combustion-supporting air is diluted, the temperature of the main combustion area is reduced, and the emission of nitrogen oxides is reduced.

According to a further embodiment of the present invention, with reference to fig. 2 and 3, the baffle wall 8 is a trapezoidal baffle wall comprising an inclined wall surface and a horizontal wall surface; further, the included angle alpha between the inclined wall surface and the wall surface line of the nozzle is 20-45 degrees. Thus, the included angle α between the inclined wall surface and the wall surface line of the nozzle is defined within the above range, which further facilitates the formation of an air flow passage with a throat portion between the baffle wall 8 and the inner wall of the nozzle and the outer wall surface of the gas lance 3, thereby increasing the air flow velocity at the throat portion to form a low pressure region.

In the embodiment of the present invention, referring to fig. 1 and 4, the inner flue gas injection unit includes an annular baffle wall 9 and an annular plate 10, one end of the annular baffle wall 9 is connected to the inner wall of the gas spray gun 3, the annular baffle wall 9 (in the shape of a circular truncated cone thin wall connected with a cylindrical thin wall) extends in the direction toward the combustion end, the annular plate 10 is supported by a rib plate and connected to the inner wall of the gas spray gun 3, the annular plate 10 extends in the direction toward the combustion end, and an inner flue gas circulation chamber D is formed between the annular baffle wall 9, the annular plate 10, the inner wall of the gas spray gun 3 and the outer wall of the gas gun central tube 4. Therefore, an air flow channel with a throat part is formed between the annular baffling wall 9 and the outer wall of the central tube 4 of the gas gun, and a baffling gap is formed between the annular plate 10 and the inner wall surface of the gas gun 3; the combustion-supporting air flow can accelerate when passing through the air flow channel with the throat and the deflection gap, a low-pressure area is formed, so that high-temperature flue gas near a nozzle for ejecting a gas spray gun 3 sequentially flows through the deflection gap and the air flow channel with the throat to the outlet end of a central tube 4 of the gas gun (namely the position of a fuel nozzle of the central tube 4 of the gas gun), so that the high-temperature flue gas flows through an inner flue gas circulation chamber D to be mixed with the combustion-supporting air in the inner flue gas circulation chamber D, the oxygen concentration of the combustion-supporting air is reduced while the combustion-supporting air is heated, the generation of nitrogen oxides is effectively inhibited, and the flame stability is improved.

According to another embodiment of the present invention, the included angle β between the leeward side of the annular baffle wall 9 and the inner wall surface line of the gas burner 3 is 15 to 45 °, so that the included angle β between the leeward side of the annular baffle wall 9 and the inner wall surface line of the gas burner 3 is limited to the above range, which further facilitates the formation of an air flow channel with a throat portion between the annular baffle wall 9 and the outer wall of the gas burner central tube 4, thereby increasing the air flow velocity at the throat portion to form a low pressure region.

In an embodiment of the present invention, referring to fig. 1, a light gun assembly 5, said light gun assembly 5 being disposed in said central air flow path adjacent to said combustion end, said light gun assembly 5 comprising a light electrode and a light gas tube (not shown in the figures), a flame monitor being operative to detect flame. Also, in the central air flow channel, a corresponding flame detector (not shown in the drawings) is provided.

In an embodiment of the present invention, referring to fig. 1, a swirl vane 6, wherein the swirl vane 6 is disposed in the central air flow passage near the combustion end, and the swirl vane 6 is connected to an inner wall surface of the central tube 4 of the gas gun. From this, swirl vane 6 has strengthened the mixture of central gas and central combustion air, and near the gas outlet of gas gun center tube 4 because swirl vane 6's whirl effect makes combustion air and gas misce bene, has strengthened combustion stability, has reached the effect of surely firing.

According to another embodiment of the invention, the included angle between the swirling vanes 6 and the inner wall surface of the central tube 4 of the gas gun is 30-60 degrees. Therefore, the included angle between the swirl vanes 6 and the inner wall surface of the central tube 4 of the gas gun is limited in the range, and the swirl vanes 6 are further favorable for promoting the mixing of central gas and central combustion air.

In the embodiment of the invention, the inlet end of the central tube 4 of the gas gun is introduced with gas fuel, a part of the gas fuel enters the gas gun 3 through a plurality of round tubes between the gas gun 3 and the central tube 4 of the gas gun, and the ignition assembly ignites the gas fuel at the outlet end of the central tube 4 of the gas gun and further ignites the gas fuel at the outlet end of the gas gun 3. A central air flow channel between the inner wall surfaces of annular cavities of a central tube 4 of the gas gun provides air for the combustion of central flame, the excess air coefficient is 1.2-1.3, and the mixing of the air and gas fuel is enhanced by the swirl blades 6.

According to the swirling flow gas recirculation gas burner of the above embodiment of the present invention, firstly, an inner gas circulation chamber D is formed between the annular baffle wall 9, the annular plate 10, the inner wall of the gas spray gun 3 and the outer wall of the gas gun central tube 4, wherein an air flow channel with a throat is formed between the annular baffle wall 9 and the outer wall of the gas gun central tube 4, and a baffle gap is formed between the annular plate 10 and the inner wall surface of the gas spray gun 3; the combustion-supporting air flow can accelerate when passing through the air flow channel with the throat and the baffling gap, a low-pressure area is formed, so that high-temperature flue gas near a nozzle of the gas spray gun 3 is injected to sequentially pass through the baffling gap and the air flow channel with the throat and reach the outlet end of the central tube 4 of the gas gun (namely the position of a fuel nozzle of the central tube 4 of the gas gun), the high-temperature flue gas flows through the inner flue gas circulation chamber D and is mixed with the combustion-supporting air in the inner flue gas circulation chamber D, the oxygen concentration of the combustion-supporting air is reduced while the combustion-supporting air is heated, the generation of nitrogen oxides is effectively inhibited, and the flame stability is improved. Secondly, an outer flue gas circulation chamber C is formed among the outer flue gas inlet 7, the deflection wall 8, the outer wall of the gas spray gun 3 and the inner wall of the nozzle, wherein the outer flue gas inlet 7 enables an outer air flow channel to be communicated with a hearth outside the wall surface of the nozzle to suck outer flue gas, and the air flow channel among the deflection wall 8, the inner wall of the nozzle and the outer wall surface of the gas spray gun 3 forms a throat part; when the combustion-supporting air flow passes through the throat, the air flow speed at the throat is increased, and a low-pressure area is also formed, so that the flue gas sucked in the hearth through the outer flue gas inlet 7 is mixed with the combustion-supporting air in the outer flue gas circulation chamber C, the oxygen concentration of the combustion-supporting air is diluted, the temperature of the main combustion area is effectively reduced, and the emission of nitrogen oxides is reduced. Thirdly, the swirl vanes 6 enhance the mixing of the central gas and the central combustion air, and the combustion air and the gas are uniformly mixed due to the swirl action of the swirl vanes 6 near the gas outlet of the central tube 4 of the gas gun, thereby enhancing the combustion stability and achieving the effect of stable combustion. Fourthly, set up gas shower nozzle on gas gun center tube 4 and the gas spray gun 3 respectively, can strengthen the connection of flame between central flame and the main burning torch effectively, guarantee combustion stability effectively.

Through field implementation verification, the invention can achieve the following performance indexes:

(1) the mass ratio of the smoke which can be sucked by the inner smoke circulating chamber and the outer smoke circulating chamber to the combustion air can reach 0.2:1, so that the temperature of the combustion air can be effectively improved, and the oxygen concentration can be reduced;

(2) in the range of 30-100% of boiler load, the combustion is stable, and the phenomena of flameout or combustion oscillation do not occur;

(3) when external Flue Gas Recirculation (FGR) is not used, the emission of nitrogen oxides is 50-60 mg/Nm³；

(4) When the proportion of the flue gas recirculation is higher than 18 percent in cooperation with the external flue gas recirculation technology (FGR), the emission of nitrogen oxides can be controlled to be 30mg/Nm³The combustion is stable and no flame-out phenomenon occurs.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.