A low-nitrogen gas combustor coupled with flue gas recirculation and staged combustion

Abstract

The application provides a low-nitrogen gas burner coupled with flue gas recirculation and staged combustion, and belongs to the field of gas burners.The application solves the problem that existing burners cannot guarantee both control of nitrogen oxide emission and stable combustion performance.The outlet end of an air passage is arranged in an air sleeve, and the inlet end of a standby sleeve is arranged in the air sleeve;first swirl vanes are arranged in the air sleeve;second swirl vanes are arranged in the standby sleeve;a standby flame gas pipe is sequentially arranged in the air passage, the air sleeve and the standby sleeve, and the outlet end of the standby flame gas pipe is provided with a group of injection holes;the outlet end of an outer ring main flame gas pipe is arranged in an outer ring mixing pipe;a plurality of outer ring gas and flue gas mixing injectors are arranged along the circumferential direction of the air sleeve;the outlet end of an inner ring main flame gas pipe is arranged in an inner ring mixing pipe;and a plurality of inner ring gas and flue gas mixing injectors are arranged along the circumferential direction of the air sleeve.The application can control nitrogen oxide emission and guarantee stable combustion.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of gas burners, in particular to a low-nitrogen gas burner coupled with flue gas recirculation and staged combustion. BACKGROUND

[0002] The tightening of the emission limit value of nitrogen oxides (NO x ) by the boiler air pollutant emission standard has prompted low-nitrogen combustion technology to become a hot spot in the industry. The emission of nitrogen oxides not only causes serious pollution to the atmospheric environment, but also has a negative impact on public health. Therefore, developing a gas burner with low nitrogen emission and high efficient combustion has become an urgent task for the current energy industry.

[0003] Although the low-nitrogen burner in the prior art can reduce the emission of nitrogen oxides to some extent, it often sacrifices the combustion efficiency, resulting in a decrease in the overall energy efficiency of the equipment and an increase in the operating cost. In addition, the complex design structure also increases the difficulty of installation and maintenance, which is not conducive to popularization and popularization in large-scale industrial applications.

[0004] Therefore, there is an urgent need to develop a new type of low-nitrogen burner that can effectively control nitrogen oxide emissions while ensuring high and stable combustion performance. SUMMARY

[0005] Therefore, in order to solve the problem that the low-nitrogen burner in the prior art cannot guarantee both effective control of nitrogen oxide emissions and high and stable combustion performance, the present application proposes a low-nitrogen gas burner coupled with flue gas recirculation and staged combustion.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A low-nitrogen gas burner coupled with flue gas recirculation and staged combustion, comprising:

[0008] An air passage, an air sleeve and a duty sleeve, the outlet end of the air passage is provided in the air sleeve, the inlet end of the duty sleeve is provided in the air sleeve, the inlet of the air sleeve is a central flue gas suction port, and the diameter of the central flue gas suction port is greater than the diameter of the outlet of the air passage;

[0009] A first swirl vane is arranged in the air sleeve between the outlet end of the air passage and the inlet end of the duty sleeve;

[0010] A second swirl vane is arranged in the duty sleeve;

[0011] A duty flame gas pipe is sequentially provided in the air passage, the air sleeve and the duty sleeve, and the outlet end of the duty flame gas pipe is provided with a group of injection holes.

[0012] A plurality of outer ring gas flue gas mixed injectors, comprising an outer ring main flame gas tube and an outer ring mixing tube, the outlet end of the outer ring main flame gas tube is arranged in the outer ring mixing tube, the diameter of the inlet of the outer ring mixing tube is larger than the diameter of the outlet of the outer ring main flame gas tube; a plurality of the outer ring gas flue gas mixed injectors are arranged along the circumferential direction of the air sleeve;

[0013] A plurality of inner ring gas flue gas mixed injectors, comprising an inner ring main flame gas tube and an inner ring mixing tube, the outlet end of the inner ring main flame gas tube is arranged in the inner ring mixing tube, the diameter of the inlet of the inner ring mixing tube is larger than the diameter of the outlet of the inner ring main flame gas tube; a plurality of the inner ring gas flue gas mixed injectors are arranged along the circumferential direction of the air sleeve; the inner ring gas flue gas mixed injectors are located between the outer ring gas flue gas mixed injectors and the air sleeve.

[0014] As a preferred solution of the above-mentioned low-nitrogen gas burner coupled with flue gas recirculation and staged combustion, the length of the inner ring mixing tube is smaller than the length of the outer ring mixing tube, and the outlet of the inner ring mixing tube is away from the outlet of the air sleeve relative to the outlet of the outer ring mixing tube.

[0015] As a preferred solution of the above-mentioned low-nitrogen gas burner coupled with flue gas recirculation and staged combustion, a plurality of the inner ring gas flue gas mixed injectors and a plurality of the outer ring gas flue gas mixed injectors are staggered.

[0016] As a preferred solution of the above-mentioned low-nitrogen gas burner coupled with flue gas recirculation and staged combustion, the outlet end of the outer ring mixing tube and the outlet end of the inner ring mixing tube are both provided with a bevel angle.

[0017] As a preferred solution of the above-mentioned low-nitrogen gas burner coupled with flue gas recirculation and staged combustion, the inlet end of the inner ring mixing tube is provided with an inner ring flue gas entraining flared nozzle; the inlet end of the outer ring mixing tube is provided with an outer ring flue gas entraining flared nozzle.

[0018] As a preferred solution of the above-mentioned low-nitrogen gas burner coupled with flue gas recirculation and staged combustion, the inner ring mixing tube is provided with a plurality of inner ring flue gas entraining rectangular holes arranged along the circumferential direction; the outer ring mixing tube is provided with a plurality of outer ring flue gas entraining rectangular holes arranged along the circumferential direction.

[0019] As a preferred solution of the low-nitrogen gas burner coupled with the flue gas recirculation and staged combustion, the group of injection holes comprises a duty flame radial injection hole and a duty flame axial injection hole arranged at an end face of an outlet end of the duty flame gas pipe; the duty flame gas pipe is fixed with a duty flame branch pipe, and the duty flame radial injection hole is arranged at a peripheral surface of the duty flame branch pipe.

[0020] As a preferred solution of the low-nitrogen gas burner coupled with the flue gas recirculation and staged combustion, the inlet end of the duty sleeve is provided with a duty sleeve flared portion.

[0021] As a preferred solution of the low-nitrogen gas burner coupled with the flue gas recirculation and staged combustion, the outlet end of the air passage is provided with an air passage flared portion.

[0022] As a preferred solution of the low-nitrogen gas burner coupled with the flue gas recirculation and staged combustion, the outlet end of the air sleeve is provided with an air sleeve flared portion.

[0023] Compared with the prior art, the low-nitrogen gas burner coupled with the flue gas recirculation and staged combustion has the following beneficial effects:

[0024] The low-nitrogen gas burner coupled with the flue gas recirculation and staged combustion is provided, which circulates the flue gas in the burner by the high-speed air entraining into the flue gas at the central flue gas entraining port and the high-speed gas entraining into the flue gas at the inner and outer ring flue gas entraining flared portions and the inner and outer ring flue gas entraining rectangular holes, so that the oxygen concentration can be reduced and the heat can be absorbed, thereby reducing the combustion speed and temperature to achieve the purpose of inhibiting the generation of nitrogen oxides. Moreover, the gas is divided into duty gas and double-layer staggered main flame gas which enters the furnace in sequence to complete the fuel staged combustion, so that the gas is combusted in different combustion areas to control the combustion speed and temperature level, reduce the generation of thermal NO x , and ensure high-efficiency and stable combustion performance. In addition, the mixed gas of air and flue gas passes through two swirl vanes of the first swirl vane and the second swirl vane in sequence, and has a certain swirl intensity. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and the illustrative embodiments of the present application and their description serve the purpose of explaining the present application, and do not constitute an improper limitation of the present application. In the drawings:

[0026] Figure 1 is a structural schematic view of the low-nitrogen gas burner coupled with the flue gas recirculation and staged combustion provided by the specific embodiments of the present application;

[0027] Figure 2 is a side view of a low-nitrogen gas burner provided by specific embodiments of the present application, which is coupled with flue gas recirculation and staged combustion.

[0028] In the drawings:

[0029] 1, air passage; 11, air passage expansion;

[0030] 2, air sleeve; 21, air sleeve expansion; 22, central flue gas suction port;

[0031] 3, duty sleeve; 31, duty sleeve expansion;

[0032] 4, first swirler vane;

[0033] 5, second swirler vane;

[0034] 6, duty flame gas pipe; 61, duty flame branch pipe; 62, duty flame axial injection hole;

[0035] 7, outer ring gas-flue gas mixing injector; 71, outer ring main flame gas pipe; 72, outer ring mixing pipe; 721, outer ring flue gas suction expansion; 722, outer ring flue gas suction rectangular hole;

[0036] 8, inner ring gas-flue gas mixing injector; 81, inner ring main flame gas pipe; 82, inner ring mixing pipe; 821, inner ring flue gas suction expansion; 822, inner ring flue gas suction rectangular hole. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other, and the described embodiments are only part of the embodiments of the present application, but not all the embodiments.

[0038] In the description of the present application, unless otherwise explicitly specified and limited, the terms "connected", "connected", "fixed" should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For ordinary skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0039] In the present application, unless otherwise explicitly specified and limited, "on" or "under" of a first feature to a second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, "on", "above" and "over" of a first feature to a second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the first feature is higher in horizontal height than the second feature. "Under", "below" and "underneath" of a first feature to a second feature includes that the first feature is directly below and obliquely below the second feature, or only indicates that the first feature is lower in horizontal height than the second feature.

[0040] In the description of the present embodiment, the terms "upper", "lower", "right", and the like orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" are only used to distinguish in the description, and have no special meaning.

[0041] Referring to Figure 1 and Figure 2To illustrate the present embodiment, the present application provides a low-nitrogen gas burner coupled with flue gas recirculation and staged combustion, which comprises an air channel 1, an air sleeve 2, a duty sleeve 3, a first swirler 4, a second swirler 5, a duty flame gas pipe 6, a plurality of outer-ring flue gas and gas mixing injectors 7, and a plurality of inner-ring flue gas and gas mixing injectors 8. The outlet end of the air channel 1 is arranged in the air sleeve 2, the inlet end of the duty sleeve 3 is arranged in the air sleeve 2, the inlet of the air sleeve 2 is a central flue gas suction port 22, and the diameter of the central flue gas suction port 22 is greater than that of the outlet of the air channel 1. The first swirler 4 is arranged in the air sleeve 2 between the outlet end of the air channel 1 and the inlet end of the duty sleeve 3. The second swirler 5 is arranged in the duty sleeve 3. The duty flame gas pipe 6 is sequentially arranged in the air channel 1, the air sleeve 2, and the duty sleeve 3, and the outlet end of the duty flame gas pipe 6 is provided with a set of injection holes. The outer-ring flue gas and gas mixing injector 7 comprises an outer-ring main flame gas pipe 71 and an outer-ring mixing pipe 72, the outlet end of the outer-ring main flame gas pipe 71 is arranged in the outer-ring mixing pipe 72, and the diameter of the inlet of the outer-ring mixing pipe 72 is greater than that of the outlet of the outer-ring main flame gas pipe 71. A plurality of outer-ring flue gas and gas mixing injectors 7 are arranged along the circumferential direction of the air sleeve 2. The inner-ring flue gas and gas mixing injector 8 comprises an inner-ring main flame gas pipe 81 and an inner-ring mixing pipe 82, the outlet end of the inner-ring main flame gas pipe 81 is arranged in the inner-ring mixing pipe 82, and the diameter of the inlet of the inner-ring mixing pipe 82 is greater than that of the outlet of the inner-ring main flame gas pipe 81. A plurality of inner-ring flue gas and gas mixing injectors 8 are arranged along the circumferential direction of the air sleeve 2. The inner-ring flue gas and gas mixing injector 8 is located between the outer-ring flue gas and gas mixing injector 7 and the air sleeve 2.

[0042] It can be understood that the inlet of the air sleeve 2 is the central flue gas suction port 22, the diameter of the central flue gas suction port 22 is greater than that of the outlet of the air channel 1, and thus there is a channel between the inner wall of the central flue gas suction port 22 and the outer wall of the air channel 1, through which flue gas can enter the air sleeve 2 and mix with air in the air sleeve 2.

[0043] It can be understood that the diameter of the inlet of the outer-ring mixing pipe 72 is greater than that of the outlet of the outer-ring main flame gas pipe 71, and thus there is a channel between the inner wall of the outer-ring mixing pipe 72 and the outer wall of the outer-ring main flame gas pipe 71, through which flue gas can enter the outer-ring mixing pipe 72 and mix with gas in the outer-ring mixing pipe 72. The diameter of the inlet of the inner-ring mixing pipe 82 is greater than that of the outlet of the inner-ring main flame gas pipe 81, and thus there is a channel between the inner wall of the inner-ring mixing pipe 82 and the outer wall of the inner-ring main flame gas pipe 81, through which flue gas can enter the inner-ring mixing pipe 82 and mix with gas in the inner-ring mixing pipe 82.

[0044] The flue gas is flue gas generated after combustion in the hearth, and the flue gas forms a backflow area in the hearth, can be sucked into the air sleeve 2 by the central flue gas suction port 22, and can also be sucked into the air sleeve 2 by the inlet of the inner ring mixing pipe 82 and the inlet of the outer ring mixing pipe 72.

[0045] In the working process of the low-nitrogen gas burner coupled with flue gas recirculation and staged combustion, air enters the air sleeve 2 through the air passage 1, and backflow flue gas is sucked into the air sleeve 2 from the central flue gas suction port 22. The air and the flue gas enter the first rotating blade 4, and the air and the flue gas are fully mixed through the first rotating blade 4. Then, part of the mixed gas is sprayed into the hearth from the outlet of the air sleeve 2, which reduces the oxygen concentration in the mixed gas, inhibits the generation of nitrogen oxides, and makes the mixed gas have a certain rotating flow intensity, so that the mixed gas can be rapidly mixed with fuel and form a stable combustion area. Another part of the mixed gas enters the standby sleeve 3 from the air sleeve 2, passes through the second rotating blade 5, and is sprayed into the hearth from the outlet of the standby sleeve 3. The mixed gas of air and flue gas has a rotating flow intensity after passing through the second rotating blade 5, so that the mixed gas can be rapidly mixed with fuel gas, increase the mixing uniformity, and ensure stable ignition and combustion. The fuel gas is sprayed into the hearth from the injection hole group of the standby flame gas pipe 6. The fuel gas is directly sprayed into the inner ring mixing pipe 82 and the outer ring mixing pipe 72 from the inner ring main flame gas pipe 81 and the outer ring main flame gas pipe 71 respectively. The high-temperature and high-speed fuel gas sucks backflow flue gas and re-sucks the flue gas generated by combustion into the inner ring mixing pipe 82 and the outer ring mixing pipe 72. After the fuel gas and the flue gas are mixed, the mixed gas is sprayed into the hearth, the flue gas generated by combustion is re-sucked into the combustion area, and the flue gas plays a role of heat absorber, which reduces the flame temperature in the high-temperature area and reduces the emission of nitrogen oxides.

[0046] The low-nitrogen gas burner coupled with flue gas recirculation and staged combustion is mainly used for small and medium-sized gas boilers equipped with a gas combustion system, and combines flue gas recirculation technology and fuel staging technology. The backflow flue gas is sucked in by the spraying of fuel gas and air, the flue gas circulates in the burner, the flue gas recirculation technology effectively reduces the oxygen concentration of the mixed gas and the flame temperature in the high-temperature area, and the fuel staging technology effectively improves the flame dispersion, makes the combustion temperature lower and more uniform, reduces the local high-temperature area, thereby inhibits the generation of nitrogen oxides (NO x ), and ensures high-efficiency and stable combustion performance.

[0047] In this embodiment, the outlet of the outer ring main flame gas pipe 71 and the outlet of the inner ring main flame gas pipe 81 are each provided with a main flame straight outlet, and the fuel gas is sprayed out through the main flame straight outlet, thereby improving the spraying speed of the fuel gas.

[0048] In this embodiment, the air sleeve 2 has a streamline structure, which can make the air flow speed field uniform and ensure stable combustion under low load conditions.

[0049] Optionally, the length of the inner ring mixing pipe 82 is less than the length of the outer ring mixing pipe 72, and the outlet of the inner ring mixing pipe 82 is farther away from the outlet of the duty sleeve 3 than the outlet of the outer ring mixing pipe 72. The outlet of the inner ring mixing pipe 82 can first spray the mixed gas of flue gas and fuel gas, and the outlet of the outer ring mixing pipe 72 can later spray the mixed gas of flue gas and fuel gas. The time difference in spraying the mixed gas of inner ring fuel gas and sucked flue gas and the mixed gas of outer ring fuel gas and sucked flue gas can avoid flame concentration.

[0050] Optionally, the plurality of inner ring fuel gas and flue gas mixing injectors 8 and the plurality of outer ring fuel gas and flue gas mixing injectors 7 are staggered. The plurality of inner ring fuel gas and flue gas mixing injectors 8 and the plurality of outer ring fuel gas and flue gas mixing injectors 7 are arranged in two rings and staggered. The flame can be dispersed to avoid flame concentration.

[0051] Optionally, the outlet end of the outer ring mixing pipe 72 and the outlet end of the inner ring mixing pipe 82 are both provided with a bevel. The flame dispersion can be further improved, the temperature field can be uniform, the local high temperature area can be reduced, and the generation of nitrogen oxides can be inhibited. In the embodiment, the long end of the bevel of the outlet end of the outer ring mixing pipe 72 is close to the inner ring mixing pipe 82, and the long end of the bevel of the outlet end of the inner ring mixing pipe 82 is close to the outer ring mixing pipe 72.

[0052] In the embodiment, the bevel is a 45° bevel.

[0053] Optionally, the inlet end of the inner ring mixing pipe 82 is provided with an inner ring flue gas suction expansion port 821, and the inlet end of the outer ring mixing pipe 72 is provided with an outer ring flue gas suction expansion port 721. The inlet amount of the backflow flue gas can be increased.

[0054] Optionally, the inner ring mixing pipe 82 is provided with a plurality of inner ring flue gas suction rectangular holes 822 arranged in the circumferential direction at intervals, and the outer ring mixing pipe 72 is provided with a plurality of outer ring flue gas suction rectangular holes 722 arranged in the circumferential direction at intervals. The plurality of inner ring flue gas suction rectangular holes 822 are arranged in the tapered section of the inner ring mixing pipe 82. The plurality of outer ring flue gas suction rectangular holes 722 are arranged in the tapered section of the outer ring mixing pipe 72. The flue gas can also be sucked into the inner ring mixing pipe 82 and the outer ring mixing pipe 72 through the inner ring suction rectangular holes and the outer ring suction rectangular holes, respectively. The resistance loss when the gas enters can be reduced by sucking the backflow flue gas through the inner ring suction rectangular holes and the outer ring suction rectangular holes.

[0055] Optionally, the group of injection holes comprises a group of primary flame radial injection holes and a group of primary flame axial injection holes 62 arranged on the end face of the outlet end of the primary flame gas tube 6; the primary flame gas tube 6 is fixed with a primary flame branch pipe 61, and the primary flame radial injection holes are arranged on the peripheral surface of the primary flame branch pipe 61. The primary flame axial injection holes 62 inject gas in the axial direction, and the primary flame radial injection holes inject gas in the radial direction. The gas is injected by the primary flame axial injection holes 62 and the primary flame radial injection holes on the primary flame branch pipe 61 in sequence, forming a diffusion flame and preventing the generation of local high temperature. It can be understood that the injection direction of the primary flame axial injection holes 62 is centripetal injection.

[0056] Optionally, the inlet end of the primary sleeve 3 is provided with a primary sleeve flared portion 31. The primary sleeve flared portion 31 increases the gas flow into the primary sleeve 3, increases the outlet velocity of the gas flow, and reduces the risk of backfire.

[0057] Optionally, the outlet end of the air channel 1 is provided with an air channel flared portion 11. Optionally, the outlet end of the air sleeve 2 is provided with an air sleeve flared portion 21.

[0058] Obviously, the above disclosed embodiments of the application are only used to help explain the application. The embodiments do not describe all the details and do not limit the application to the specific embodiments. According to the content of the specification, many modifications and changes can be made. The specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the application, so that those skilled in the art can well understand and utilize the application. It is not necessary and impossible to exhaust all the embodiments here. Any modification, equivalent replacement and improvement made within the spirit and principles of the application shall be included in the protection scope of the claims of the application.

Claims

1. A low NOx gas burner with coupling of flue gas recirculation and staged combustion, characterized in that, The application relates to a gas and smoke mixing burner, which comprises an air channel (1), an air sleeve (2) and a value sleeve (3), the outlet end of the air channel (1) is arranged in the air sleeve (2), the inlet end of the value sleeve (3) is arranged in the air sleeve (2), the inlet of the air sleeve (2) is a central smoke suction port (22), the diameter of the central smoke suction port (22) is larger than the diameter of the outlet of the air channel (1); a first rotating flow blade (4) is arranged in the air sleeve (2) and located between the outlet end of the air channel (1) and the inlet end of the value sleeve (3); a second rotating flow blade (5) is arranged in the value sleeve (3); a value flame gas pipe (6) is arranged in the air channel (1), the air sleeve (2) and the value sleeve (3) in sequence, the outlet end of the value flame gas pipe (6) is provided with a group of injection holes; a plurality of outer-ring gas and smoke mixing injectors (7) comprise an outer-ring main flame gas pipe (71) and an outer-ring mixing pipe (72), the outlet end of the outer-ring main flame gas pipe (71) is arranged in the outer-ring mixing pipe (72), the diameter of the inlet of the outer-ring mixing pipe (72) is larger than the diameter of the outlet of the outer-ring main flame gas pipe (71); the plurality of outer-ring gas and smoke mixing injectors (7) are arranged along the circumferential direction of the air sleeve (2) at intervals; a plurality of inner-ring gas and smoke mixing injectors (8) comprise an inner-ring main flame gas pipe (81) and an inner-ring mixing pipe (82), the outlet end of the inner-ring main flame gas pipe (81) is arranged in the inner-ring mixing pipe (82), the diameter of the inlet of the inner-ring mixing pipe (82) is larger than the diameter of the outlet of the inner-ring main flame gas pipe (81); the plurality of inner-ring gas and smoke mixing injectors (8) are arranged along the circumferential direction of the air sleeve (2) at intervals; the inner-ring gas and smoke mixing injectors (8) are located between the outer-ring gas and smoke mixing injectors (7) and the air sleeve (2); the length of the inner-ring mixing pipe (82) is smaller than the length of the outer-ring mixing pipe (72), the outlet of the inner-ring mixing pipe (82) is away from the outlet of the value sleeve (3) relative to the outlet of the outer-ring mixing pipe (72); the plurality of inner-ring gas and smoke mixing injectors (8) and the plurality of outer-ring gas and smoke mixing injectors (7) are arranged alternately; the outlet end of the outer-ring mixing pipe (72) and the outlet end of the inner-ring mixing pipe (82) are both provided with a bevel angle; the inner-ring mixing pipe (82) is provided with a plurality of inner-ring smoke suction rectangular holes (822) arranged along the circumferential direction at intervals; the outer-ring mixing pipe (72) is provided with a plurality of outer-ring smoke suction rectangular holes (722) arranged along the circumferential direction at intervals; the inlet end of the inner-ring mixing pipe (82) is provided with an inner-ring smoke suction flared mouth (821); the inlet end of the outer-ring mixing pipe (72) is provided with an outer-ring smoke suction flared mouth (721). ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2. The low NOx gas burner with flue gas recirculation and staged combustion coupling of claim 1, wherein: ​ 3. The low-NOx gas burner coupled with flue gas recirculation and staged combustion according to claim 1, characterized in that: The injection hole group comprises a standby flame radial injection hole and a standby flame axial injection hole (62) arranged at the end face of the outlet end of the standby flame gas pipe (6); the standby flame gas pipe (6) is fixed with a standby flame branch pipe (61), and the standby flame radial injection hole is arranged at the peripheral surface of the standby flame branch pipe (61).

4. The low NOx gas combustor with flue gas recirculation and staged combustion coupling of claim 1, wherein: The inlet end of the standby sleeve (3) is provided with a standby sleeve flared portion (31).

5. The low NOx gas combustor with flue gas recirculation and staged combustion coupling of claim 1, wherein: The outlet end of the air channel (1) is provided with an air channel flared portion (11).

6. The low NOx gas combustor with flue gas recirculation and staged combustion coupling of claim 1, wherein: The outlet end of the air sleeve (2) is provided with an air sleeve flared portion (21).

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