Flue gas internal circulation burner

Abstract

The application provides a gas inner circulation combustor, which comprises a refractory castable table, an outer combustor throat, a gas circulation guide device, an inner combustor throat, a flame stabilizer, a center gas gun and a main gas gun. The outer combustor throat has one end in the opening and the other end extending to the outside of the first surface. The gas circulation guide device has one end in the opening and the other end extending to the outside of the second surface. The inner combustor throat is in the gas circulation guide device. The flame stabilizer is outside the second surface and in the inner combustor throat and connected with the inner combustor throat. The center gas gun has one end extending to the outside of the first surface and the other end extending to the outside of the flame stabilizer. The main gas gun has one end extending to the outside of the first surface and the other end extending to the outside of the second surface. The combustion air pipe is outside the gas circulation guide device. The application does not have the condensate water problem existing in the flue gas outer circulation technology of the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of industrial gas burner combustion technology, in particular to a flue gas internal circulation burner. BACKGROUND

[0002] The flue gas external circulation technology is to take part of the flue gas in the tail of the boiler from the outside by a certain power, mix the flue gas with the combustion air, and then send them into the furnace for low-nitrogen combustion. However, the existing flue gas external circulation burner inevitably has the problem of condensate water in the mixing process of flue gas and air at room temperature, and the problem of condensate water needs to be removed at a greater cost, and it is also difficult to remove all of them, which has a safety hazard in winter operation. SUMMARY

[0003] To achieve the above object and other related objects, the present application provides a gas internal circulation burner, comprising:

[0004] A refractory castable platform comprising opposite first and second surfaces, an opening is formed in the refractory castable platform, the opening extends from the first surface to the second surface;

[0005] A burner outer throat, one end of which is located in the opening, and the other end extends to the outside of the first surface;

[0006] A gas circulation flow guide device, one end of which is located in the opening and has a spacing with the outside of the burner outer throat, and the other end extends to the outside of the second surface;

[0007] A burner inner throat, located in the gas circulation flow guide device, one end of which is located in the opening and inserted into the burner outer throat, and the other end extends to the outside of the second surface;

[0008] A flame stabilizer, located outside the second surface and in the burner inner throat, and connected with the burner inner throat;

[0009] A central gas gun, penetrating through the burner outer throat and the burner inner throat, one end of which extends to the outside of the first surface, and the other end extends to the side of the flame stabilizer away from the burner inner throat;

[0010] A main gas gun, located outside the burner inner throat, penetrating through the burner outer throat and the gas circulation flow guide device, one end of which extends to the outside of the first surface, and the other end extends to the outside of the second surface;

[0011] A supplementary combustion air pipe, located outside the gas circulation flow guide device, one end of which is located in the opening and communicates with the inside of the burner outer throat, and the other end extends to the outside of the second surface.

[0012] Optionally, the outer burner throat comprises an outer throat large-end straight pipe section, an outer throat taper section and an outer throat small-end straight pipe section; wherein one end of the outer throat large-end straight pipe section is located in the opening and the other end extends to the outside of the first surface; the outer throat small-end straight pipe section is located in the opening; the outer throat taper section is located in the opening, one end of which is connected with the outer throat large-end straight pipe section and the other end is connected with the outer throat small-end straight pipe section.

[0013] Optionally, the supplemental air pipe is in communication with the inner part of the outer burner throat via the outer throat taper section.

[0014] Optionally, the inner burner throat comprises an inner throat small-end straight pipe section, an inner throat taper section and an inner throat large-end straight pipe section; wherein the inner throat small-end straight pipe section is located in the opening and one end of which is inserted into the outer throat small-end straight pipe section; one end of the inner throat taper section is connected with the inner throat small-end straight pipe section and the other end is connected with the inner throat large-end straight pipe section; one end of the inner throat large-end straight pipe section, which is away from the inner throat taper section, extends to the outside of the second surface.

[0015] Optionally, the diameter of the outer throat large-end straight pipe section is less than or equal to the diameter of the opening and the diameter of the inner throat large-end straight pipe section is less than the diameter of the opening.

[0016] Optionally, the central axis of the opening, the central axis of the outer burner throat, the central axis of the inner burner throat, the central axis of the gas circulation guide device and the central axis of the central gas gun are all coincident with the central axis of the flue gas inner-circulation combustor.

[0017] Optionally, the number of the main gas guns and the number of the supplemental air pipes are both multiple; the multiple main gas guns are arranged along the circumference of the inner burner throat; the multiple supplemental air pipes are arranged along the circumference of the flue gas circulation guide device.

[0018] Optionally, the end of the central gas gun, which extends to the outside of the second surface, is provided with a plurality of axial flame stabilizing nozzles and the side wall of the central gas gun, which is adjacent to the axial flame stabilizing nozzles, is provided with a plurality of radial flame stabilizing nozzles.

[0019] Optionally, the end of the main gas gun, which extends to the outside of the second surface, is provided with a plurality of axial combustion-supporting gas nozzles and the side wall of the main gas gun, which is adjacent to the axial combustion-supporting gas nozzles, is provided with a plurality of lateral combustion-supporting gas nozzles, which are directed to the side away from the inner burner throat.

[0020] As mentioned above, the name of the present application has the following beneficial effects:

[0021] 1. The special structure and relative position of the outer throat of the burner, the inner throat of the burner, and the flue gas circulation guide device in the flue gas internal circulation burner of the present application can generate strong suction at the outer throat of the burner, and make a large amount of low-oxygen high-temperature flue gas flow back to the outlet of the outer throat of the burner through the flue gas internal circulation backflow channel and mix with most of the combustion air. The special structure and relative position of the outer throat of the burner and the inner throat of the burner make a small part of the combustion air enter the inner throat of the burner, and most of the combustion air enter the area between the inner throat of the burner and the flue gas circulation guide device. There is no problem of condensed water existing in the flue gas external circulation technology of the prior art.

[0022] 2. The large-scale necking of the outer throat of the burner makes the flow area of the combustion air decrease rapidly, and the speed of the combustion air increase greatly, generating strong suction; and there is no combustion air flowing into the flue gas internal circulation backflow channel, so the backflow of the high-temperature flue gas is not hindered. Therefore, under the action of the suction at the small-end straight pipe section of the outer throat of the burner, a large amount of high-temperature flue gas flows back to the outlet of the small-end straight pipe section of the outer throat of the burner and mixes with most of the combustion air, forming a low-oxygen mixed gas.

[0023] 3. The combustion air channel is arranged outside the flue gas circulation guide device, and draws the combustion air from the tapered section of the outer throat to the lateral main gas nozzle of the main gas gun, ensuring stable combustion. At the same time, the low-speed low-pressure area at the flame stabilizer and the pressure stabilizer can ensure the stability of the flame.

[0024] 4. The main gas gun has a gas nozzle facing outward, and the gas penetrates the air / mixed gas layer, forming external dense combustion and reducing the emission of NOx. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 Figure 1 is a top view of the flue gas internal circulation burner of the present application.

[0026] Figure 2 Figure 2 is a sectional view of the flue gas internal circulation burner of the present application.

[0027] Figure 3 Figure 3 is a partial perspective view of the center gas gun in the flue gas internal circulation burner of the present application.

[0028] Figure 4 Figure 4 is a partial perspective view of the main gas gun in the flue gas internal circulation burner of the present application.

[0029] Figure 5 Figure 5 is a schematic diagram of the flue gas internal circulation of the flue gas internal circulation burner of the present application during operation.

[0030] Element No. 1, central gas gun; 10, gas passage; 11, circumferential flame stabilizing nozzle; 12, radial flame stabilizing nozzle; 2, flame stabilizer; 3, inner throat of the burner; 31, small-end straight pipe section of the inner throat; 32, gradually expanding section of the inner throat; 33, large-end straight pipe section of the inner throat; 4, flue gas circulation guide device; 41, upstream section of the flue gas circulation guide device; 5, outer throat of the burner; 51, large-end straight pipe section of the outer throat; 52, gradually reducing section of the outer throat; 53, small-end straight pipe section of the outer throat; 6, main gas gun; 61, axial main gas nozzle; 62, lateral main gas nozzle; 7, supplementary combustion air pipe; 8, combustion air passage; 81, supplementary combustion air passage; 9, refractory pouring table; 91, opening; 92, first surface; 93, second surface. DETAILED DESCRIPTION

[0031] 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. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the scope of protection of the present application.

[0032] The preferred embodiments in the following description are only examples, and other obvious variations can be conceived by those skilled in the art. The basic principles of the present application defined in the following description can be applied to other embodiments, variations, improvements, equivalents and other technical solutions without departing from the spirit and scope of the present application.

[0033] Those skilled in the art should understand that in the disclosure of the present application, the orientations or positional relationships indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like are based on the orientations or positional relationships shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the above terms cannot be understood as a limitation of the present application.

[0034] The flue gas internal circulation technology is to make the high-temperature flue gas in the furnace backflow to the inner area of the burner through the structure of the burner, mix the low-oxygen high-temperature flue gas with the combustion air, make the fuel burn in low-oxygen, and then reduce the emission of NOx. If the "low-nitrogen technology coupling + flue gas internal circulation technology" on the burner can achieve a low-nitrogen emission of 30mg / Nm 3 , it has very great significance in the low-nitrogen combustion industry.

[0035] The flue gas external circulation technology is to take part of the flue gas in the tail flue of the boiler from the outside by a certain power, mix the flue gas with combustion air, and then send the mixture into the furnace for low-nitrogen combustion. However, in the mixing process of the flue gas and the air at normal temperature, the existing flue gas external circulation burner inevitably has the problem of condensed water, and the problem of condensed water needs to be removed at a greater cost and is difficult to be completely removed, and there is a safety hazard in winter operation.

[0036] Embodiment one

[0037] Please refer to Figure 1 and Figure 2 The present application provides a flue gas internal circulation burner, comprising: a refractory castable table 9, the refractory castable table 9 comprising opposite first and second surfaces 92 and 93, and an opening 91 is formed in the refractory castable table 9, the opening 91 extending from the first surface 92 to the second surface 93; a burner outer throat 5, one end of the burner outer throat 5 being located in the opening 91, and the other end extending to the outside of the first surface 92; a gas circulation guide device 4, one end of the gas circulation guide device 4 being located in the opening 91 and having a spacing with the outside of the burner outer throat 5, and the other end extending to the outside of the second surface 93; a burner inner throat 3, the burner inner throat 3 being located in the gas circulation guide device 4, one end of the burner inner throat 3 being located in the opening 91 and inserted into the burner outer throat 5, and the other end extending to the outside of the second surface 93; a flame stabilizer 2, located outside the second surface 93 and in the burner inner throat 3, and connected with the burner inner throat 3; a center gas gun 1, the center gas gun 1 penetrating the burner outer throat 5 and the burner inner throat 3, one end of the center gas gun 1 extending to the outside of the first surface 92, and the other end extending to the side of the flame stabilizer 2 away from the burner inner throat; a main gas gun 6, the main gas gun 6 being located outside the burner inner throat 3, penetrating the burner outer throat 5 and the gas circulation guide device 4, one end of the main gas gun 6 extending to the outside of the first surface 92, and the other end extending to the outside of the second surface 93; and a supplementary combustion air pipe 7, the supplementary combustion air pipe 7 being located outside the gas circulation guide device 4, one end of the supplementary combustion air pipe 7 being located in the opening 91 and connected with the inside of the burner outer throat 5, and the other end extending to the outside of the second surface 93.

[0038] The special structure and relative position of the burner outer throat 5, the burner inner throat 3 and the flue gas circulation guide device 4 in the flue gas internal circulation burner of the present application can generate strong suction at the burner outer throat 5, and make a large amount of low-oxygen high-temperature flue gas flow back to the outlet of the burner outer throat 5 through the flue gas internal circulation backflow channel and mix with most of the combustion air. The special structure and relative position of the burner outer throat 5 and the burner inner throat 6 make a small part of the combustion air enter the burner inner throat 3, and most of the combustion air enter the area between the burner inner throat 3 and the flue gas circulation guide device 4. There is no problem of condensed water existing in the flue gas external circulation technology in the prior art.

[0039] As an example, the supplemental combustion air pipe 7 is a supplemental combustion air channel 81, the central gas gun 1 is a gas channel 10, the main gas gun 6 can also be a gas channel 10, and the burner outer throat 5 is a combustion air channel 8.

[0040] As an example, the flue gas internal circulation backflow channel is formed between the burner outer throat 5 and the flue gas circulation guide device 4.

[0041] Embodiment two

[0042] Please continue to refer to Figures 1 to 2 In this embodiment, a flue gas internal circulation burner is also provided, and the flue gas internal circulation burner in this embodiment further comprises the following structure on the basis of the flue gas internal circulation burner described in embodiment one:

[0043] As an example, as Figure 2 shown, the burner outer throat 5 can include an outer throat large-end straight pipe segment 51, an outer throat tapering segment 52 and an outer throat small-end straight pipe segment 53; one end of the outer throat large-end straight pipe segment 51 is located in the opening 91, and the other end extends to the outside of the first surface 92; the outer throat small-end straight pipe segment 53 is located in the opening 91; the outer throat tapering segment 52 is located in the opening 91, one end of the outer throat tapering segment 52 is connected with the outer throat large-end straight pipe segment 51, and the other end is connected with the outer throat small-end straight pipe segment 53. That is, the burner outer throat 5 can be regarded as a reduced-diameter pipe with straight segments at both ends.

[0044] As an example, the supplemental combustion air pipe 7 is connected with the inside of the burner outer throat 5 through the outer throat tapering segment 52.

[0045] As an example, the inner throat 3 comprises: an inner throat small-end straight pipe section 31, an inner throat converging section 32, and an inner throat large-end straight pipe section 33; wherein the inner throat small-end straight pipe section 31 is located in the opening 91, and one end of the inner throat small-end straight pipe section 31 is inserted into the outer throat small-end straight pipe section 53; one end of the inner throat converging section 32 is connected to the inner throat small-end straight pipe section 31, and the other end is connected to the inner throat large-end straight pipe section 33; one end of the inner throat large-end straight pipe section 33, which is away from the inner throat converging section 32, extends to the outside of the second surface 93. That is, the inner throat 3 of the combustor can be regarded as a pipe with a diameter expanding at both ends.

[0046] As an example, the diameter of the outer throat small-end straight pipe section 53 is greater than the diameter of the inner throat small-end straight pipe section 31 and less than the diameter of the inner throat large-end straight pipe section 33.

[0047] The present application can generate strong suction at the outer throat small-end straight pipe section 53 of the combustor outer throat 5, and make a large amount of low-oxygen high-temperature flue gas flow back to the outlet of the outer throat small-end straight pipe section 53 of the combustor outer throat 5 through the flue gas internal circulation backflow channel, and mix with most of the combustion air. The large-scale contraction of the combustor outer throat 5 rapidly reduces the flow area of the combustion air, greatly increases the speed of the combustion air, and generates strong suction; and there is no flow of combustion air into the flue gas internal circulation backflow channel, so the backflow of high-temperature flue gas is not hindered. Therefore, under the action of the suction at the outer throat small-end straight pipe section 53 of the combustor, a large amount of high-temperature flue gas flows back to the outlet of the outer throat small-end straight pipe section 53 of the combustor, and mixes with most of the combustion air to form a low-oxygen mixture.

[0048] As an example, the diameter of the outer throat large-end straight pipe section 5 is less than or equal to the diameter of the opening 91, and the diameter of the inner throat large-end straight pipe section 33 is less than the diameter of the opening 91; specifically, the diameter of the outer throat large-end straight pipe section 5 can be slightly smaller than the diameter of the opening 91.

[0049] As an example, the flame stabilizer 2 is placed in the inner throat large-end straight pipe section 33, and the central gas gun 1 passes through the flame stabilizer 2, which can be in the form of a cyclone disc or a flame stabilizer plate, etc., to form a low-speed low-pressure area at the flame stabilizer 2 area.

[0050] As an example, the diameter of the upstream section 41 of the flue gas circulation guide device is greater than the diameter of the outer throat small-end straight pipe section 53, and the outer throat small-end straight pipe section 53 extends into the upstream section 41 of the flue gas circulation guide device.

[0051] As an example, the center axis of the opening 91, the center axis of the outer burner throat 5, the center axis of the inner burner throat 3, the center axis of the flue gas circulation guide device 4 and the center axis of the center flue gas gun 1 all coincide with the center axis of the flue gas inner circulation burner.

[0052] As an example, as shown in Figure 1 , the number of the main flue gas guns 6 and the number of the supplementary combustion air pipes 7 are both multiple; the multiple main flue gas guns 6 are arranged along the circumference of the inner burner throat 3, and can be uniformly arranged; the multiple supplementary combustion air pipes 7 are arranged along the circumference of the flue gas circulation guide device 4, and can be uniformly arranged.

[0053] As an example, Figure 1 only one layer of the main flue gas guns 6 arranged along the circumference of the inner burner throat 3 is taken as an example, in other examples, multiple layers of the main flue gas guns 6 arranged along the circumference of the inner burner throat 3. Similarly, Figure 1 only one layer of the supplementary combustion air pipes 7 arranged along the circumference of the flue gas circulation guide device 4 is taken as an example, in other examples, multiple layers of the supplementary combustion air pipes 7 arranged along the circumference of the flue gas circulation guide device 4.

[0054] As an example, as shown in Figure 3 , the end of the center flue gas gun 1 extending to the outside of the second surface 93 is provided with several axial stable flame nozzles 11, and the side wall of the center flue gas gun 1 near the axial stable flame nozzles 11 is provided with several radial stable flame nozzles 12, and the radial stable flame nozzles 12 can be arranged along the circumference of the center flue gas gun 1.

[0055] As an example, as shown in Figure 4 , the end of the main flue gas gun 6 extending to the outside of the second surface 93 is provided with several axial combustion-supporting gas nozzles 61, and the side wall of the main flue gas gun 6 near the axial combustion-supporting gas nozzles 61 is provided with several lateral combustion-supporting gas nozzles 62, and the lateral combustion-supporting gas nozzles 62 are directed away from the inner burner throat 3. The main flue gas gun 6 has a gas nozzle facing outward, and the gas penetrates the air / mixture layer to form external rich combustion, thereby reducing NOx emissions.

[0056] The supplementary combustion air passage 7 of the present application is placed outside the flue gas circulation guide device 4, and the combustion-supporting air is introduced from the outer throat tapering section 52 to the lateral main flue gas nozzles 62 of the main flue gas gun 6, thereby ensuring stable combustion and stable flame. The low-speed and low-pressure area at the flame stabilizer 2 can also ensure the stability of the flame.

[0057] Please refer to Figure 5 , Figure 5The dashed arrow in the figure is the direction of the air flow. When the smoke internal circulation burner of the application is working, the combustion air enters the burner from the combustion air channel 8, and the fuel enters from the gas channel 10, and enters the center gas gun 1 and the main gas gun 6 respectively. The combustion air enters the combustion air channel 8, and then passes through the outer throat large-end straight pipe section 51, the outer throat taper section 52, and the outer throat small-end straight pipe section 53. The flow rate of the combustion air is greatly increased in the outer throat taper section 52, and a strong negative pressure is formed at the outer throat small-end straight pipe section 53. A small part of the combustion air enters the burner inner throat 3, is sprayed from the flame stabilizer 2 to the furnace (the furnace is the area outside the second surface 93 of the refractory pouring platform 9) at a low speed, and the flow area of the center combustion air is increased and the flow rate is reduced, and a low pressure and low speed is formed in the center area with the cooperation of the flame stabilizer 2, the surrounding smoke is sucked back to the center flame area of the burner, low-oxygen combustion is carried out, and the generation of NOx is reduced; most of the combustion air flows out from the channel between the outer throat small-end straight pipe section 53 and the inner throat small-end straight pipe section 31. The low-oxygen high-temperature smoke is sucked into the outlet of the outer throat small-end straight pipe section 53 from the smoke internal circulation backflow channel under the strong suction of the negative pressure at the outlet of the outer throat small-end straight pipe section 53, a large amount of internal circulation smoke and most of the combustion air are mixed to form a low-oxygen mixed gas, and the low-oxygen mixed gas flows forward from the channel between the smoke circulation guide device 4 and the burner inner throat 3, and flows out of the burner and is sprayed into the furnace at a high speed.

[0058] A small part of the fuel enters the center gas gun 1, is sprayed from the axial flame stabilizing nozzle 11 and the radial flame stabilizing nozzle 12 on the center gas gun 1, enters the low-speed low-pressure area, meets the combustion air sprayed from the flame stabilizer 2 at a low speed, and is ignited, the low-oxygen circulation smoke and a small amount of combustion air that flow back enable the center gas to carry out low-oxygen dense combustion, and the generation of NOx is reduced; most of the fuel enters the main gas gun 6, the axial main gas nozzle 61 sprays the gas towards the depth direction of the furnace, and the lateral main gas nozzle 62 sprays the gas outward, the side-sprayed gas penetrates the air / mixed gas layer, the main gas meets the low-oxygen mixed gas, is ignited by the center flame to form a main flame, the low-oxygen mixed gas enables the main flame area to form a lean combustion / dense combustion working condition, suppresses and reduces the generation of NOx, the amount of NOx generated in the combustion process is extremely small, and the low-nitrogen emission of 30mg / Nm 3 of NOx is achieved. The fuel that is not fully combusted and the low-oxygen mixed gas are gradually mixed and combusted in the subsequent combustion process.

[0059] And the combustion air pipe 7 provides the main flame rich combustion area with the appropriate amount of fresh air without flue gas mixing, prevents flame instability or flameout under the lean oxygen working condition, appropriately increases the oxygen content of the flame root, improves the stability of the flame, and does not damage the overall lean oxygen combustion condition, forms a stable flame, and achieves stable low-NOx combustion effect.

[0060] Therefore, the flue gas internal circulation combustor can achieve stable and sufficient low-nitrogen combustion without using flue gas external circulation, and the emission of NOx can be less than 30mg / Nm 3 .

[0061] The flue gas internal circulation combustor of the present application realizes flue gas internal circulation, and the emission of NOx can be directly less than 30mg / Nm 3 . By the structural design of the combustor body, a large amount of low-oxygen high-temperature flue gas outside the outer throat 5 of the combustor is sucked back to the vicinity of the combustor throat, mixed with most of the combustion air to form a low-oxygen mixed gas, and the mixed gas is transported to the main gas gun to make the gas burn with low oxygen and low nitrogen, and further inhibit the generation of NOx by using part of the combustion intermediates. At the same time, the main gas gun 6 is provided with the combustion air pipe 7, which ensures the stability of the combustion. The low-oxygen mixed gas is gradually sucked and burned with the remaining unburned fuel. The present application can avoid the need for additional flue gas circulating fans, flue gas circulating pipelines and other equipment required by traditional flue gas external circulation technology, and at the same time, the problems of condensate and vibration generated by traditional flue gas external circulation technology are avoided, which has great significance.

[0062] It is apparent to those skilled in the art that the present application is not limited to the details of the foregoing exemplary embodiments, but can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, and the scope of the present application should be defined by the appended claims rather than the above description, and it is intended to encompass all changes falling within the meaning and range of equivalents of the elements of the claims. Any reference signs in the claims should not be considered as limiting the claims involved.

[0063] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A named flue gas internally recirculating burner characterized by, The application relates to a refractory castable platform, a burner outer throat, a burner inner throat, a flame stabilizer, a center gas gun, a main gas gun and a combustion air pipe. The refractory castable platform comprises a first surface and a second surface, and an opening is formed in the refractory castable platform and extends from the first surface to the second surface. The burner outer throat is located in the opening and extends to the outside of the first surface. The burner inner throat is located in the combustion gas circulation guide device and extends to the outside of the second surface. The flame stabilizer is located outside the second surface and in the burner inner throat. The center gas gun extends through the burner outer throat and the burner inner throat and extends to the outside of the first surface. The main gas gun is located outside the burner inner throat and extends to the outside of the second surface.

2. The internally recirculating flue gas combustor of claim 1, wherein: The combustion air pipe is located outside the combustion gas circulation guide device, one end of the combustion air pipe is located in the opening and communicates with the inside of the burner outer throat, and the other end of the combustion air pipe extends to the outside of the second surface. The burner outer throat comprises an outer throat large-end straight pipe section, an outer throat taper section and an outer throat small-end straight pipe section. The outer throat small-end straight pipe section is located in the opening.

3. The internally recirculating flue gas combustor of claim 2, wherein: The outer throat taper section is located in the opening and is connected with the outer throat large-end straight pipe section at one end and connected with the outer throat small-end straight pipe section at the other end.

4. The internally recirculating flue gas combustor of claim 2, wherein: The combustion air pipe communicates with the inside of the burner outer throat through the outer throat taper section. The burner inner throat comprises an inner throat small-end straight pipe section, an inner throat taper section and an inner throat large-end straight pipe section. The inner throat small-end straight pipe section is located in the opening and is inserted into the outer throat small-end straight pipe section at one end.

5. The internally recirculating flue gas combustor of claim 4, wherein: The inner throat large-end straight pipe section extends to the outside of the second surface at one end away from the inner throat taper section.

6. The internally recirculating flue gas combustor of claim 1, wherein: The diameter of the outer throat large-end straight pipe section is less than or equal to the diameter of the opening, and the diameter of the inner throat large-end straight pipe section is less than the diameter of the opening. The center axes of the opening, the burner outer throat, the burner inner throat, the combustion gas circulation guide device and the center gas gun are coincident with the center axis of the flue gas internal circulation burner.

7. The internally recirculating flue gas combustor of claim 1, wherein: The number of the main gas guns and the number of the supplementary combustion air pipes are both multiple; multiple main gas guns are arranged along the circumference of the inner throat of the combustor; multiple supplementary combustion air pipes are arranged along the circumference of the gas circulation guide device.

8. The internally recirculating flue gas combustor of claim 1, wherein: The end of the central gas gun extending to the outside of the second surface is provided with several axial flame stabilizing nozzles, and the side wall of the central gas gun near the axial flame stabilizing nozzles is provided with several radial flame stabilizing nozzles.

9. The internally recirculating flue gas combustor of claim 1, wherein: The end of the main gas gun extending to the outside of the second surface is provided with several axial combustion-supporting gas nozzles, and the side wall of the main gas gun near the axial combustion-supporting gas nozzles is provided with several lateral combustion-supporting gas nozzles, and the lateral combustion-supporting gas nozzles are directed to the side away from the inner throat of the combustor.

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