Flue gas internal circulation gas burner

Abstract

The application provides a flue gas internal circulation gas burner and relates to the technical field of ultra-low nitrogen diffusion type gas burners. The flue gas internal circulation gas burner comprises a base, an open front end of the base, a wind channel for entering combustion-supporting wind arranged in the base, an outer cylinder, a partial length of the outer periphery of the outer cylinder being sleeved on the front end of the base, the outer cylinder being configured as a hollow structure with open two ends and having a gas ring cavity, gas in the gas ring cavity being released from a plurality of outer ring slits, the gas being mixed with combustion-supporting wind released from the outer ring slits, being ignited at a position adjacent to the front end of the front cylinder, avoiding combustion when fuel concentration is too high in any combustion area, causing the generation of instantaneous nitrogen oxides, when the burner is installed in a boiler, combustion-supporting wind released through the outer ring slits and high-temperature flue gas in a furnace chamber generating momentum exchange, forming a rolling effect, and finally forming flue gas internal circulation, reducing the generation of thermal nitrogen oxides.

Description

Technical Field

[0001] This invention relates to the field of ultra-low nitrogen diffusion gas burner technology, specifically a flue gas internal circulation gas burner. Background Technology

[0002] Traditional ultra-low nitrogen diffusion gas burners generally use FGR external flue gas recirculation or internal flue gas recirculation technology. The internal flue gas recirculation technology generally uses a Venturi structure in traditional diffusion burners to achieve internal flue gas recirculation.

[0003] Furthermore, since traditional diffusion burners still involve simultaneous mixing and combustion in the main flame zone, with the mixing and combustion zones overlapping, high concentrations of fuel gas exist in the combustion zone. When the fuel concentration is too rich, the CH radicals generated from the high-temperature decomposition of hydrocarbons react with nitrogen in the air to produce HCN and N, which further react with oxygen to generate nitrogen oxides at an extremely rapid rate. Therefore, it is impossible to overcome the problem of transient nitrogen oxides. Moreover, due to the relatively long flame length, the flame stability is poor, and a high control ratio cannot be achieved, generally below 1:4, and a high excess air coefficient is required, generally above 1.2. To address this, we propose a flue gas recirculation burner that separates the mixing and combustion zones, resulting in a lower and more uniform fuel concentration distribution in the combustion zone, thus avoiding the generation of transient nitrogen oxides. The mixing of fuel gas and combustion air is basically completed in the mixing zone, which greatly improves combustion stability and thus increases the burner's control ratio. Summary of the Invention

[0004] The purpose of this invention is to provide a flue gas recirculation combustion burner, which aims to solve the problem that existing burners mix and burn simultaneously, resulting in high and uneven fuel concentrations in the combustion zone, leading to a large amount of transient nitrogen oxides.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a flue gas internal circulation gas burner, comprising: a base, the front end of which is open, and an air duct for combustion air to enter is provided therein; an outer cylinder, the outer periphery of which is partially fitted onto the front end of the base, the outer cylinder being a hollow structure with open ends and having a gas annular cavity, the gas annular cavity being provided with an annular tube to allow gas to enter the gas annular cavity; a front cylinder, the diameter of which is smaller than the diameter of the outer cylinder, the axes of which are substantially coincident with those of the outer cylinder, the front cylinder including a rectifying cone located inside the outer cylinder and a cylinder connected to the rectifying cone, the conical surface of the rectifying cone forming a rectifying cavity with the inner surface of the outer cylinder, and a portion of the cylinder... Located inside the outer cylinder, thus forming an outer annular gap with the outer cylinder, the distance between the conical surface of the rectifying cone and the inner surface of the outer cylinder gradually decreases from the air inlet direction, so that part of the combustion air in the air duct is released through the rectifying cavity and the outer annular gap; and multiple outer annular gap gas pipes, which are evenly distributed circumferentially inside the outer annular gap. The outer annular gap gas pipes are connected to the gas annular cavity, and the gas entering the gas annular cavity is released from the multiple outer annular gap gas pipes. After mixing with the combustion air released from the outer annular gap, it is ignited at the front end near the front cylinder. When the burner is installed inside the boiler, the combustion air released through the outer annular gap exchanges momentum with the high-temperature flue gas in the furnace, forming an entrainment effect, and finally forming internal flue gas circulation.

[0006] A further technical solution of the present invention is that the diameter of the outer annular gas pipe is smaller than the spacing of the outer annular seams, and the outer annular gas pipe is located on the inner side close to the outer annular seams.

[0007] A further technical solution of the present invention is that the distance between the axis of the outer annular gas pipe and the inner surface of the outer cylinder is less than the distance between the axis of the outer annular gas pipe and the outer circumferential surface of the cylinder.

[0008] A further technical solution of the present invention includes a core assembly, which is disposed at the axial position of the outer cylinder and the front cylinder. The core assembly includes a central gas pipe and a flame stabilizer. The central gas pipe includes an axial central gas pipe coaxially disposed with the front cylinder. The flame stabilizer includes a flame stabilizing plate that seals the front opening of the front cylinder and a baffle ring disposed at the center of the flame stabilizing plate. The front end of the axial central gas pipe is located inside the baffle ring. Thus, when the combustion air from the air duct enters the baffle ring through the rear opening of the front cylinder, it mixes with the gas released from the front end of the central gas pipe inside the baffle ring. When the mixed combustion air and gas are released from the front end of the front cylinder and ignited, high-temperature flue gas is formed.

[0009] A further technical solution of the present invention is that the central gas pipe further includes a radial central gas pipe, which is substantially perpendicular to the axial central gas pipe. The radial central gas pipe is connected to the base body, thereby providing rear-end support for the core assembly, and the flame stabilizer provides front-end support for the core assembly.

[0010] A further technical solution of the present invention is that the core assembly further includes a central air jet, the central air jet including a central air jet duct, a rectifier plate installed at the front end of the central air jet duct, and a gas ring gap baffle installed adjacent to the front end of the central air jet duct.

[0011] A further technical solution of the present invention is that the diameter of the central jet duct is smaller than the diameter of the axial central gas pipe, and both ends of the central jet duct are disposed through the axial position of the axial central gas pipe, so that a central gas passage is formed between the central jet duct and the axial central gas pipe. The gas annular gap baffle is located near the front opening of the axial central gas pipe, and a gas annular gap is formed between the gas annular gap baffle and the front end face of the axial central gas pipe. The gas annular gap is located inside the baffle ring, so that the gas entering the central gas passage is released from the gas annular gap into the baffle ring.

[0012] A further technical solution of the present invention is that the front end face of the axial center gas pipe and / or the side of the gas annular gap baffle facing the axial center gas pipe are provided with a conical inclined surface, thereby providing a velocity component toward the rectifier plate direction to the gas released from the gas annular gap.

[0013] A further technical solution of the present invention is that a main annular gap is formed between the rectifier plate and the baffle ring, so that the gas and combustion air mixed in the baffle ring pass through the main annular gap and are released outward along the radial direction of the rectifier plate. When the gas and combustion air released outward through the main annular gap are ignited, the resulting flue gas can ignite the gas released from the outer annular gap.

[0014] A further technical solution of the present invention is that a jet duct is provided axially in the central jet duct, and an air duct opening communicating with the jet duct is opened near the rear end of the central jet duct. It also includes a regulating valve for regulating the air intake volume entering the jet duct from the air duct opening.

[0015] A further technical solution of the present invention is that one end of the outer annular gas pipe extends from the front opening of the outer cylinder, and the length of the outer annular gas pipe extending out of the outer cylinder is less than the axial length of the cylinder.

[0016] The beneficial effects of this invention are:

[0017] 1. Avoid combustion in any area where the fuel concentration is too rich, which can lead to the production of transient nitrogen oxides.

[0018] 2. The flue gas is guided by a high-speed annular jet combustion air, which allows the flue gas to participate in mixing and combustion, reducing the hot spot temperature in the combustion zone and reducing the generation of thermal nitrogen oxides.

[0019] 3. The annular combustion air and the gas nozzles densely distributed within the annular gap of the combustion air are mixed in a more efficient manner, resulting in a shorter flame and improved flame stability, thereby increasing the burner's control ratio.

[0020] 4. Maintain the total excess air coefficient at 1.1-1.15 to reduce flue gas volume and improve boiler efficiency.

[0021] 5. The gas nozzle is located near the inner side of the annular gap, which ensures a very low gas concentration on the high-temperature side of the mixed gas, achieving lean combustion and very low nitrogen oxide emissions.

[0022] 6. As combustion progresses, fuel gas and combustion air are consumed. The further downstream the combustion zone, the higher the excess air coefficient and the lower the nitrogen oxide emissions. Attached Figure Description

[0023] Figure 1 This is a three-dimensional view of a diffusion burner;

[0024] Figure 2 yes Figure 1 Enlarged view of a portion of point A in the middle;

[0025] Figure 3 This is a side view of a diffusion burner;

[0026] Figure 4A yes Figure 3 A cross-sectional view along the middle AA section, with the reinforcing ribs omitted in the figure;

[0027] Figure 4B This is a schematic diagram of the burner installed inside the furnace, showing the direction of flue gas recirculation.

[0028] Figure 5 yes Figure 4A Cross-sectional view of the front cylinder;

[0029] Figure 6 yes Figure 4A Cross-sectional view of the inner and outer cylinders;

[0030] Figure 7 It is a 3D diagram of the core component;

[0031] Figure 8 This is a three-dimensional view of the core component from another perspective;

[0032] Figure 9 This is a 3D view of the central wind jet generator;

[0033] Figure 10This is an exploded view of the central air jet generator and valves;

[0034] Figure 11 This is an exploded view of the control valve;

[0035] Figure 12 yes Figure 7 Enlarged view of a section at point B in the middle;

[0036] Figure 13 This is a side view of the central gas pipe;

[0037] Figure 14 This is a cross-sectional view of the core assembly;

[0038] Figure 15 yes Figure 14 Enlarged view of a section at point C;

[0039] Figure 16 yes Figure 15 Modified embodiments;

[0040] Figure 17 This is a 3D diagram of a flame stabilizer;

[0041] Figure 18 This is a side view of the flame stabilizer.

[0042] In the picture:

[0043] 1. Matrix; 11. Air duct; 12. Exhaust fan;

[0044] 2. Outer cylinder; 21. Gas annular cavity; 22. Outer annular seam; 23. Rectifying cavity; 24. Annular cavity pipe; 25. Outer annular seam gas pipe; 26. Connecting parts;

[0045] 3. Front cylinder; 31. Cylinder body; 32. Rectifying cone; 32a. Conical surface;

[0046] 4. Central jet nozzle; 41. Central jet duct; 41a. Front end of central jet duct; 41b. Rear end of central jet duct; 42. Rectifier plate; 43. Gas annular seam baffle; 44. Rib plate; 45. Jet duct; 451. Duct opening;

[0047] 46. ​​Control valve; 461. Valve seat; 4611. Valve seat port; 4612. Mounting hole; 462. Valve core; 4622. Valve core port; 4621. Baffle; 463. Adjusting shaft; 464. Valve plate; 4641. Bayonet; 465. Annular mounting groove; 466. Fastening assembly; 4661. Bolt; 4662. Nut;

[0048] 5. Central gas pipe; 51. Axial central gas pipe; 511. Inclined surface; 52. Radial central gas pipe; 53. Central gas passage; 54. Gas annular joint; 55. Pipe seat; 56. Fixing seat;

[0049] 6. Flame stabilizer; 61. Connecting sleeve; 62. Reinforcing rib; 63. Flame stabilizer plate; 631. Vent hole; 64. Baffle ring; 65. Adjusting screw seat; 66. Main ring seam;

[0050] 7. First lead screw; 71. Annular limiting groove;

[0051] 8. Second lead screw;

[0052] 9. Gas supply device; 91. Annular gas inlet pipe; 92. Central gas inlet pipe; 93. Valve assembly;

[0053] 10. Furnace; Detailed Implementation

[0054] Firstly, traditional diffusion burners still involve simultaneous mixing and combustion in the main flame area. During operation, the burner is divided into a combustion zone and a mixing zone, which may overlap or not. Since the mixing of fuel gas and combustion air requires a process, there will inevitably be a fuel gas concentration gradient in the mixing zone. The closer to the fuel gas release port, the higher the fuel gas concentration. When the mixing zone and the combustion zone overlap, a large amount of transient nitrogen oxides will be generated when the area with excessively rich fuel gas concentration is in the overlapping zone. Therefore, the purpose of our diffusion burner is to effectively isolate the mixing zone and the combustion zone, ensuring that the fuel concentration in the combustion zone is low enough and evenly distributed while still being ignitable, thereby reducing the amount of transient nitrogen oxides generated.

[0055] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0056] refer to Figures 1 to 6 The diffusion burner includes a base 1, with an air duct 11 inside the base 1, and external air is introduced into the air duct 11 by an induced draft fan 12. An outer cylinder 2 is fitted onto the front opening of the base 1, and the outer circumferential wall of the outer cylinder 2 surrounds a portion of the outer circumference of the front end of the base 1. The outer cylinder 2 is a hollow structure with openings at both ends. The diameter of the rear end of the outer cylinder 2 is larger than the diameter of the front end of the base 1. The front end of the outer cylinder 2 extends axially from the front opening of the base 1, and the outer cylinder 2 and the base 1 are assembled to form a gas annular cavity 21 (Figure 4). Specifically, one sidewall constituting the gas annular cavity 21 is the outer wall of the base 1. Of course, the gas annular cavity 21 can also be set separately at the rear end of the outer cylinder 2. It should be explained that in this embodiment, one end of the outer cylinder 2 connected to the base 1 is the rear end, and the other end is the front end.

[0057] refer to Figure 4A and Figure 5The front cylinder 3 is inserted into the front end of the outer cylinder 2. The front cylinder 3 is also a hollow structure with openings at both ends. It includes a cylinder 31 with an annular cross-section and a rectifier cone 32 that is integrally formed with or welded to the cylinder 31. The rectifier cone 32 is located inside the outer cylinder 2. A portion of the outer periphery of the cylinder 31 and the outer periphery of the front portion of the outer cylinder 2 form an outer annular seam 22. The cone surface 32a of the rectifier cone 32 and the outer cylinder 2 form a rectifier cavity 23. Some of the air entering the air duct 11 enters the interior of the cylinder 31, while some air enters the rectifier cavity 23 and the outer annular seam 22 for discharge. It should be noted that the distance between the cone surface 32a and the outer circumferential wall of the outer cylinder 2 gradually decreases from the air inlet direction, thereby allowing as much air from the air duct 11 as possible to enter the outer annular seam 22.

[0058] refer to Figure 1 , Figure 4A and Figure 6 An annular cavity 21 is connected to an annular tube 24, allowing gas to enter the annular cavity tube 24. Multiple outer annular slit gas pipes 25 are arranged circumferentially within the outer annular slit 22, with one end of each outer annular slit gas pipe 25 connected to the annular cavity 21, ultimately mixing and igniting the gas and air passing through the outer annular slit 22. Preferably, one end of the outer annular slit gas pipe 25 extends beyond the outer annular slit; in other words, one end of the outer annular slit gas pipe 25 extends a certain distance from the outer annular slit 22, and the outer annular slit gas pipe 25 almost contacts the outer circumferential wall of the cylinder 31. That is, the outer annular slit gas pipe 25 is positioned close to the inner side of the outer annular slit 22. The distance between the axis of the outer ring gas pipe 25 and the inner surface of the outer cylinder 2 is less than the distance between the axis of the outer ring gas pipe 25 and the outer circumferential surface of the cylinder 31. Therefore, after the gas with a certain velocity is discharged through the outer ring gas pipe 25, it will be released axially forward close to the outer circumferential wall of the cylinder 31. The gas concentration is highest when it is released near the outer ring seam 22. As the gas is released towards the front cylinder 3, the gas concentration gradually decreases. The gas can be ignited near the front cylinder 3, effectively reducing the content of nitrogen oxides. It is worth noting that one end of the outer ring gas pipe 25 may not extend out of the outer ring seam 22, which can be adjusted according to the actual situation of the burner and boiler.

[0059] refer to Figure 2 and Figure 6 In order to connect the outer cylinder 2 and the front cylinder 3 together, multiple connectors 26 can be provided in the outer circumferential seam 22 to fix the outer cylinder 2 and the front cylinder 3 together.

[0060] refer to Figure 4A , Figure 7 and Figure 8 The diffuser burner also includes a core assembly, which is located at the axial position of the outer cylinder 2 and the front cylinder 3. The core assembly includes a central air jet 4, a central gas pipe 5, and a flame stabilizer 6. By setting the core assembly, a main flame can be generated at the front end of the front cylinder 3. The following will describe in detail how the main flame is generated.

[0061] refer to Figure 9 The central jet burner 4 includes a central jet duct 41, a rectifier plate 42 is installed at the front end 41a of the central jet duct 41, and a gas ring baffle 43 is installed near the front end 41a of the central jet duct 41. In order to improve the connection strength between the central jet duct 41 and the rectifier plate 42, one or more ribs 44 are welded and fixed between the front end 41a of the central jet duct 41 and the rectifier plate 42. The central jet duct 41 has a jet duct 45 in the axial direction, so that part of the air in the duct 11 enters the jet duct 45 to form a jet air, which is axially ejected from the front end of the diffuser burner. The rectifier plate 42 is preferably disc-shaped, but it can also be square or elliptical.

[0062] The central jet air can reduce the temperature of the central recirculation flue gas and increase its oxygen content. When the mixed central recirculation flue gas participates in the combustion of the central fuel gas, it reduces the temperature of the central flame and the thermal nitrogen oxides in the central flame. At the same time, due to the premixing of the central fuel gas, the generation of instantaneous nitrogen oxides in the central flame is avoided, thus achieving overall emission of the central flame.

[0063] The function of the central jet air is to cool the temperature of the central return flue gas. If the air volume is too small, the effect will not be obvious, and if the air volume is too large, the stability of the central flame may deteriorate.

[0064] refer to Figure 10 In order to adjust the air intake from the air duct 11 to the jet air duct 45, a regulating valve 46 is installed at the rear end 41b of the central jet air duct 41. Two opposing air duct ports 451 are opened on the outer peripheral wall of the jet air duct 45 near the rear end. The air intake of the air duct ports 451 is adjusted by the regulating valve 46.

[0065] refer to Figure 11 For example, the regulating valve 46 includes a valve seat 461, a valve core 462, and an regulating shaft 463. The valve seat 461 is a hollow structure with openings at both ends and has opposing valve seat ports 4611. One end of the valve core 462 is open so that the rear end 41b of the central jet duct 41 can be accommodated inside the valve core 462. The other end of the valve core 462 has a baffle 4621 to block the rear end face of the central jet duct 41. The valve core 462 also has two opposing valve core ports 4622. The outer diameter of the valve core 462 is slightly smaller than the inner diameter of the valve seat 461 so that the valve core 462 can rotate relative to the valve seat 461.

[0066] As a variation, the valve core 462 can also move axially relative to the valve seat 461, so that the positions of the valve core port 4622 and the valve seat port 4611 correspond or are offset, which can also regulate the air intake volume of the air duct port 451.

[0067] When the regulating valve 46 is open, the positions of the two opposing air duct ports 451 of the jet air duct 45, the two opposing valve core ports 4622 of the valve core 462, and the two opposing valve seat ports 4611 of the valve seat 461 are completely aligned. At this time, the valve core 462 can be rotated by the regulating shaft 463 to change the overlapping area of ​​the valve core port 4622 and the valve seat port 461, thereby adjusting the air intake from the air duct 11 into the jet air duct 45. When the positions of the valve core port 4622 and the valve seat port 4611 are completely misaligned, the regulating valve 46 is closed. It should be emphasized that the air duct port 451, valve core port 4622, and valve seat port 4611 can also be provided with only one, three, or more. By rotating the valve core 462, the overlapping area of ​​the valve core port 4622 and the valve seat port 4611 can be changed, or the valve core port 4622 and the valve seat port 4611 can be completely misaligned.

[0068] Continue to refer to Figure 11 A valve plate 464 is welded onto the valve seat 461 of the regulating valve 46, and the valve plate 464 is fixed to the core assembly.

[0069] refer to Figure 7 , Figure 10 and Figure 12 To facilitate the quick assembly of the valve seat 461, valve core 462, and adjusting shaft 463, the diameter of the adjusting shaft 463 is smaller than the diameter of the baffle 4621 of the valve core 462, and the axial length of the valve seat 461 is greater than the axial length of the valve core 462. This means that when the valve core 462 is rotatably assembled inside the valve seat 461, and the valve core port 4622 and the valve seat port 4611 are in corresponding positions, the end of the valve seat 461 near the adjusting shaft 463 has a portion extending out of the baffle 4621. This extended portion forms an annular mounting groove 465 with the baffle 4621 and the adjusting shaft 463. The fastening assembly 466 is provided on the extended portion, the baffle 4621, and the adjusting shaft 463, thereby installing the valve seat 461, valve core 462, and adjusting shaft 463 together.

[0070] refer to Figure 11 and Figure 12 The valve seat 461 has one or more mounting holes 4612 on the portion of the protruding baffle 4621. The fastening assembly 466 includes a bolt 4661 installed inside the mounting hole 4612 and a nut 4662 provided inside the annular mounting groove 465 and threadedly engaged with the bolt 4661. When tightened, the nut 4662 contacts the inner circumferential surface of the annular mounting groove 465, and one end of the bolt 4661 abuts against the outer circumferential surface of the adjusting shaft 463.

[0071] refer to Figure 13 and Figure 14The central gas pipe 5 includes an axial central gas pipe 51 and a radial central gas pipe 52. The axial central gas pipe 51 is located on the axis of the diffuser burner, and its inner diameter is larger than the outer diameter of the central jet duct 41. The two are coaxially arranged so as to form a central gas passage 53 between the axial central gas pipe 51 and the central jet duct 41.

[0072] The radial central gas pipe 52 is connected to the rear end of the axial central gas pipe 51 and extends radially along the air duct 11. The lower end of the radial central gas pipe 52 is connected to the outer wall of the base 1 through a flange, thereby supporting the rear end of the entire core assembly.

[0073] refer to Figure 15 The front end face of the radial central gas pipe 52 and the gas annular baffle 43 on the central air jet 4 form a gas annular gap 54, wherein the diameter of the gas annular gap baffle 43 is basically the same as the diameter of the axial central gas pipe 51. When the gas enters the central gas channel 53 formed by the axial central gas pipe 51 and the central jet air pipe 41 through the radial central gas pipe 52, the gas with a certain speed flows through the central gas channel 53 and is released from the gas annular gap 54. It should be noted that in order to make the gas released from the gas annular gap 54 have an axial forward velocity component, the front end face of the axial central gas pipe 51 has an inclined surface 511. When the gas with a certain speed is released from the gas annular gap 54, under the guidance of the inclined surface 511, the released gas has radial and axial velocity components.

[0074] refer to Figure 16 As a variation, the inclined surface 511 can be provided only on the outer edge of the gas annular gap baffle 43, or the inclined surface 511 can be provided on both the front end face of the axial center gas pipe 51 and the outer edge of the gas annular gap baffle 43; when the gas with a certain speed is released from the gas annular gap 54, the released gas has radial and axial velocity components under the guidance of the inclined surface 511.

[0075] refer to Figure 14 , Figure 17 and Figure 18The flame stabilizer 6 includes a connecting sleeve 61 fitted onto the front end of the axial central gas pipe 51. The connecting sleeve 61 is fixedly connected to a flame stabilizing disc 63 via reinforcing ribs 62. A retaining ring 64 is installed at the center of the flame stabilizing disc 63. The flame stabilizing disc 63 seals the front opening of the front cylinder 3. The gas annular gap baffle 43 and the front end of the axial central gas pipe 51 are both located within the retaining ring 64. That is, the gas annular gap 54 is located inside the retaining ring 64. As mentioned earlier, the gas released from the gas annular gap 54 has radial and axial velocity components. The inner circumferential surface of the retaining ring 64 can limit... The release range of the gas, that is, the gas released from the gas annular gap 54 will be obstructed by the inner circumferential surface of the baffle ring 64 in the radial direction. The combustion air that enters the front cylinder 3 through the air duct 11 will also enter the baffle ring 64 and mix with the gas released from the gas annular gap 54. Preferably, the flame stabilizer plate 63 is provided with multiple ventilation holes 631. The air entering the front cylinder 3 can be discharged through the ventilation holes 631, which can cool the flame stabilizer plate 63, effectively avoid the problem of long-term heat deformation of the flame stabilizer plate 63, and improve the service life of the flame stabilizer plate 63.

[0076] In order to increase the recirculation velocity of the central recirculation flue gas and reduce the thermal nitrogen oxides in the main flame;

[0077] refer to Figure 14 A main annular gap 66 is formed between the rectifier plate 42 on the central air jet 4 and the baffle ring 64 on the flame stabilizer 6. The gas and combustion air mixed together inside the baffle ring 64 are ejected from the main annular gap 66 in the radial direction of the rectifier plate 42. At this time, the mixed gas and combustion air are ignited by the spark plug (not shown in the figure) to form the main flame. Unlike conventional burners, in this embodiment, the main flame is diffused in the radial direction of the rectifier plate 42, and the mixture of gas and combustion air released through the outer annular gap is ignited by the high-temperature flue gas formed by the main flame. When the burner of this embodiment is installed on the boiler, the outer cylinder 2 and the front cylinder 3 extend into the furnace 10 of the boiler.

[0078] refer to Figure 4B During combustion, according to the principles of gas dynamics, the high-speed jet of combustion air released through the outer annular seam 22 exchanges momentum with the high-temperature flue gas in the furnace 10, forming an entrainment effect. A ring-shaped recirculation zone is generated in the area inside the furnace 10 near the outer annular seam 22. The high-temperature flue gas in the recirculation zone will return to the position near the outer annular seam 22, ensuring the ignition of the cold unburned mixture, while reducing the flame hot spot temperature and the oxygen content of the combustion air to reduce the generation of thermal nitrogen oxides.

[0079] Continue to refer to Figure 4BAccording to the principles of gas dynamics, the combustion air of the high-speed jet released through the main annular gap 66 exchanges momentum with the high-temperature flue gas in the furnace 10, which also forms an entrainment effect, creating a ring-shaped recirculation area in front of the front cylinder 3. The high-temperature flue gas in the recirculation area will return to the position adjacent to the front cylinder 3.

[0080] It is worth mentioning that the diameter of the rectifier plate 42 is larger than that of the baffle ring 64. The function of the rectifier plate 42 is to make the radial velocity of the main flame much higher than its axial velocity in the airflow direction of the main flame, so that the efficiency of injecting the central flue gas is higher and more central flue gas recirculation will be generated. At the same time, since the radial direction of the main flame is directly pointing to the outer main flame, the stability is higher. In addition, the pre-mixing of the central combustion gas and the central combustion air can reduce the instantaneous nitrogen oxides of the central flame.

[0081] refer to Figure 7 and Figure 14 Since the oxygen content in the combustion air varies in different regions and at different temperatures, the size of the gas annular gap 54 is adjustable in order to control the mixing ratio of the gas and the combustion air released from the main annular gap 66. For example, a first lead screw 7 is installed on the core assembly, which is used to drive the central air jet 4 to move axially relative to the central gas pipe 5.

[0082] refer to Figure 13 and Figure 14 The rear end of the central gas pipe 5 is connected to a pipe seat 55. The length direction of the first lead screw 7 is parallel to the axial direction of the central gas pipe 51. One end of the first lead screw 7 is threadedly connected to the pipe seat 55, and the other end extends to the outside of the base 1. The first lead screw 7 is rotatably connected to the valve plate 464. The first lead screw 7 can be connected to the valve plate 464 through a bearing, or as... Figure 11 and Figure 12 As shown, the valve plate 464 has a bayonet 4641 on one side, and the first lead screw 7 is provided with an annular limiting groove 71. The annular limiting groove 71 enters into the bayonet 4641 and is rotatably connected to the valve plate 464. In other embodiments, the first lead screw 7 can also be threaded to the base 1, and the front end of the first lead screw 7 is rotatably connected to the valve plate 464, which can also drive the central air jet 4 to move axially.

[0083] When adjusting the mixing ratio of gas and combustion air, the first lead screw 7 is rotated. Since the central gas pipe 5 is fixed on the base 1, the axial movement of the first lead screw 7 drives the central air jet 4 to move axially back and forth, thereby increasing or decreasing the distance between the gas annular gap baffle 43 and the axial central gas pipe 51. Finally, by adjusting the size of the gas annular gap 54, the amount of gas released from the gas annular gap 54 is adjusted. At the same time, the rectifier plate 42 also moves axially back and forth, causing the distance between the end faces of the rectifier plate 42 and the baffle ring 64 to increase or decrease, thereby increasing or decreasing the size of the main annular gap 66 accordingly.

[0084] refer to Figure 8 To better control the amount of combustion mixture released from the main annular gap 66, the flame stabilizer 6 is individually adjustable, meaning that the flame stabilizer 6 can move axially back and forth relative to the central air jet 4. For example, the flame stabilizer 6 also includes an adjusting screw seat 65 fixedly installed at the rear end of the connecting sleeve 61, a fixed seat 56 fixedly installed on the central gas pipe 5, a second screw 8 threadedly connected to the adjusting screw seat 65, and the second screw 8 and the fixed seat 56 can be rotatably connected by a bearing. One end of the second screw 8 extends through to the outside of the base 1, so that when the second screw 8 is rotated, the connecting sleeve 61 slides axially at the front end of the axial central gas pipe 51, ultimately adjusting the size of the main annular gap 66.

[0085] refer to Figure 1 As shown in Figure 4, the diffusion burner also includes a gas supply device 9, which delivers gas to the outer annular gap 22 and the central gas pipe 5. The gas supply device 9 includes a gas source (not shown in the figure) and a gas input pipe connected to the gas source. In this embodiment, the gas input pipe includes an annular gas input pipe 91 and a central gas input pipe 92. The annular gas input pipe 91 and the central gas input pipe 92 are connected to the same gas source and, in conjunction with the existing valve group 93, control the opening and closing of the annular gas input pipe 91 and the central gas input pipe 92. The annular gas input pipe 91 is connected to the annular pipe 24 through a flange, and the central gas pipe 5 is connected to the central gas input pipe 92, thereby releasing gas into the outer annular gap 22 and the main annular gap 66.

[0086] The working principle of the burner is as follows: the induced draft fan 12 introduces the combustion air into the air duct 11. Part of the combustion air enters from the rear end opening of the front cylinder 3 and exits from the front end opening of the front cylinder 3; another part of the combustion air enters from the rectifier chamber 23 and exits from the outer annular gap 22. At the same time, part of the gas enters the gas annular chamber 21 through the annular chamber pipe 24 and is released from the front of the outer annular gap 22 through the outer annular gap gas pipe 25. The gas released from the front of the outer annular gap 22 mixes with the combustion air discharged from the outer annular gap 22. Due to the existence of the outer annular gap 22, the gas is released in an annular shape, which ensures that the mixing area and the combustion area of ​​the burner are effectively isolated, so that the high gas concentration mixing area does not overlap with the combustion area. Moreover, the position of the gas nozzle is close to the inner side of the outer annular gap, so that the high temperature side gas concentration of the mixed gas is very low, achieving lean gas combustion and very low nitrogen oxide emissions.

[0087] On the other hand, when the combustion air entering the front cylinder 3 is released from the baffle ring 64, it mixes with the gas released from the gas ring 54 and is released in a ring from the main ring 66 along the radial direction of the rectifier plate 42. After being ignited by an ignition device (e.g., a spark plug), it forms high-temperature flue gas with a certain velocity. The high-temperature flue gas can ignite the mixture of gas released from the outer ring 22 and the combustion air, thereby achieving diffusion-type ultra-low nitrogen combustion.

[0088] This document describes in detail exemplary embodiments of the present invention with reference to preferred embodiments. However, those skilled in the art will understand that various modifications and alterations can be made to the above specific embodiments without departing from the concept of the present invention, and various combinations can be made to the various technical features and structures proposed in the present invention without exceeding the protection scope of the present invention, which is determined by the appended claims.

Claims

1. A gas burner with internal recirculation of the flue gases, characterized in that, It comprises: a base (1) with an open front end, in which a wind channel (11) for the entry of combustion-supporting air is arranged; an outer cylinder (2) with a length that is partially surrounded by the outer periphery of the front end of the base (1), the outer cylinder (2) being configured as a hollow structure with open ends and having a gas ring cavity (21), the gas ring cavity (21) being provided with a ring cavity pipe (24) to enable the entry of gas into the gas ring cavity (21); a front cylinder (3) with a diameter that is smaller than the diameter of the outer cylinder (2), the front cylinder (3) being arranged in substantial alignment with the axis of the outer cylinder (2), the front cylinder (3) comprising a flow-converging cone cylinder (32) arranged inside the outer cylinder (2) and a cylinder body (31) connected to the flow-converging cone cylinder (32), the flow-converging cone cylinder (32) having a conical surface (32a) that forms a flow-converging cavity (23) with the inner surface of the outer cylinder (2), part of the cylinder body (31) being arranged inside the outer cylinder (2) to form an outer ring gap (22) with the outer cylinder (2), the distance between the conical surface (32a) of the flow-converging cone cylinder (32) and the inner surface of the outer cylinder (2) gradually decreasing from the direction of air entry, so that part of the combustion-supporting air in the wind channel (11) is released through the flow-converging cavity (23) and the outer ring gap (22); and a plurality of outer ring gap gas pipes (25) arranged in the outer ring gap (22) in a uniform circumferential interval, the outer ring gap gas pipes (25) being connected to the gas ring cavity (21) to release the gas in the gas ring cavity (21) through the outer ring gap gas pipes (25) after mixing with the combustion-supporting air released from the outer ring gap (22) and being ignited at a position adjacent to the front end of the front cylinder (3), when the burner is installed in a boiler, the combustion-supporting air released through the outer ring gap (22) and the high-temperature flue gas in the furnace (10) produce momentum exchange to form a swirling effect, and finally form a flue gas internal circulation. It further comprises a core assembly. The core assembly further comprises a central air jet (4) comprising a central jet air pipe (41), a flow-converging plate (42) arranged at the front end of the central jet air pipe (41), and a gas ring gap baffle (43) arranged adjacent to the front end of the central jet air pipe (41).

2. The fume inner circulation gas burner according to claim 1, characterized in that, The diameter of the outer ring gap gas pipe (25) is smaller than the distance between the outer ring gap (22), and the outer ring gap gas pipe (25) is arranged at a position close to the inner side of the outer ring gap (22).

3. The internally recirculating flue gas gas burner according to claim 2, characterized in that The distance between the axis of the outer ring gap gas pipe (25) and the inner surface of the outer cylinder (2) is smaller than the distance between the axis of the outer ring gap gas pipe (25) and the outer circumferential surface of the cylinder body (31).

4. The fume inner circulation gas burner according to claim 1, characterized in that, The core assembly is arranged at the axial position of the outer cylinder (2) and the front cylinder (3), and comprises a central gas pipe (5) and a flame holder (6). The central gas pipe (5) comprises an axial central gas pipe (51) coaxially arranged with the front cylinder (3), and the flame holder (6) comprises a flame holding disc (63) blocked at the front end opening of the front cylinder (3) and a baffle ring (64) arranged at the center of the flame holding disc (63), and the front end of the axial central gas pipe (51) is located in the baffle ring (64), so that the combustion-supporting air from the air duct (11) enters into the baffle ring (64) through the rear end opening of the front cylinder (3), mixes with the gas released from the front end of the central gas pipe (5) in the baffle ring (64), and forms high-temperature flue gas when the mixed combustion-supporting air and gas are released from the front end of the front cylinder (3) and ignited.

5. The internally recirculating flue gas gas burner according to claim 4, characterized in that The central gas pipe (5) further comprises a radial central gas pipe (52) substantially perpendicular to the axial central gas pipe (51), and the radial central gas pipe (52) is connected with the base body (1) to provide rear end support for the core head assembly, and the flame holder (6) provides front end support for the core head assembly.

6. The fume inner circulation gas burner according to claim 5, characterized in that, The diameter of the central jet air pipe (41) is smaller than that of the axial central gas pipe (51), and the central jet air pipe (41) penetrates the axial position of the axial central gas pipe (51) at both ends, so that the central jet air pipe (41) and the axial central gas pipe (51) form a central gas passage (53) therebetween, the gas ring gap baffle (43) is located adjacent to the front end opening of the axial central gas pipe (51), and the gas ring gap baffle (43) and the front end face of the axial central gas pipe (51) form a gas ring gap (54) therebetween, and the gas ring gap (54) is located inside the baffle ring (64), so that the gas entering into the central gas passage (53) is released from the gas ring gap (54) into the baffle ring (64).

7. The fume inner circulation gas burner according to claim 6, characterized in that, The front end face of the axial central gas pipe (51) and / or the side of the gas ring gap baffle (43) facing the axial central gas pipe (51) is provided with a conical inclined surface (511), so as to provide the gas released from the gas ring gap (54) with a velocity component in the direction of the flow regulation plate (42).

8. The fume inner circulation gas burner according to claim 6, characterized in that, The flow regulation plate (42) and the baffle ring (64) form a main ring gap (66) therebetween, so that the mixed gas and combustion-supporting air in the baffle ring (64) pass through the main ring gap (66) and are released outward along the radial direction of the flow regulation plate (42), and when the gas and combustion-supporting air released outward through the main ring gap (66) are ignited, the flue gas formed can ignite the gas released from the outer ring gap (22).

9. The internally recirculating flue gas gas burner according to claim 6, characterized in that The central jet air pipe (41) is provided with a jet air duct in the axial direction, an air duct opening (451) is arranged adjacent to the rear end of the central jet air pipe (41) and communicates with the jet air duct, and an adjusting valve is further arranged to adjust the air inflow into the jet air duct from the air duct opening (451).

10. The inner-recirculation flue gas burner according to any one of claims 1 to 9, characterized in that One end of the outer ring slit gas pipe (25) extends from the front end opening of the outer cylinder (2), and the length of the outer ring slit gas pipe (25) extending out of the outer cylinder (2) is less than the axial length of the cylinder body (31).

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