Staged combustor and method of combustor regulation using water vapor to reduce NOx emissions

Abstract

The application provides a staged combustor and a combustor adjusting method for reducing NOx emission by using water vapor. The combustor comprises an air inlet shell, a steam coil, a secondary air shell, a fire tube, a gas gun and a displacement driving mechanism; the steam coil comprises a water inlet pipe, a heated coil and a steam ejection ring pipe connected in sequence. Water enters the water inlet pipe of the steam coil, cools the primary flame burning in the fire tube, prevents local high temperature, reduces NOx emission in the primary combustion area, and at the same time, the generated water vapor is ejected from the steam outlet hole of the steam ejection ring pipe, participates in the secondary combustion after being mixed with the secondary air in the secondary air shell, and the OH and H groups generated by the water vapor decomposition can carry out a chain reaction with the CO generated by the primary combustion, so that the reducing atmosphere is enhanced, the occurrence of the NO homologous reduction reaction is facilitated, and the H and OH free radicals generated by the water vapor dissociation can inhibit the oxidation of HCN to NO, and the joint action of the H and OH free radicals can reduce the generation of NO.

Description

Technical Field

[0001] This invention relates to the field of burner technology, specifically to a staged burner that utilizes water vapor to reduce NOx emissions. Background Technology

[0002] With increasing environmental awareness, reducing NOx emissions from burners has been a persistent focus in this field. While existing technologies document the mechanism of water vapor in NOx control, there is a lack of research on applying water vapor to reduce NOx emissions in burners. Therefore, there is an urgent need to propose a technical solution for reducing NOx emissions from burners using water vapor. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a staged burner and burner regulation method for reducing NOx emissions by utilizing water vapor.

[0004] To achieve the above objectives, the technical solution adopted by the present invention to solve its technical problem is: a staged burner that uses water vapor to reduce NOx emissions, comprising an air inlet shell, a steam coil, a secondary air shell, a flame shield, a gas gun, and a shifting drive mechanism;

[0005] The air inlet housing is provided with a first air inlet for inputting combustion-supporting gas, and the tail end of the fire shield is provided with a second air inlet. The secondary air housing is installed at the front end of the air inlet housing, and the fire shield is installed inside the secondary air housing. Part of the combustion-supporting gas input from the first air inlet enters the space between the secondary air housing and the fire shield, and the other part enters the inner cavity of the fire shield through the second air inlet.

[0006] The gas gun is provided with a gas inlet for inputting gas, a gas nozzle is provided at the front end of the gas gun, and a spark plug for ignition is also provided on the gas gun. The gas gun is movably installed on the fixed sleeve of the air inlet housing. The front end of the gas gun is located in the inner cavity of the fire shield tube. The displacement drive mechanism is used to drive the gas gun to move back and forth along the axis of the fire shield tube.

[0007] The steam coil includes a water inlet pipe, a heating coil, and a steam ejection ring pipe connected in sequence. The heating coil is located inside the fire shield, and the steam ejection ring pipe is located between the secondary air shell and the fire shield. The steam ejection ring pipe is provided with multiple steam outlet holes facing forward.

[0008] Using the technical solution of this invention, water enters from the inlet pipe of the steam coil, cooling the primary flame burning inside the flame shield to prevent localized high temperatures and reduce NOx emissions from the primary combustion zone. Simultaneously, the heated steam is ejected from the steam outlet of the steam ejection ring pipe. This steam mixes with secondary air in the secondary air shell and participates in secondary combustion. The OH and H groups produced by the decomposition of the steam can initiate a chain reaction with the CO produced in the primary combustion, enhancing the reducing atmosphere and facilitating the homogeneous reduction reaction of NO. Furthermore, the H and OH free radicals generated by the dissociation of the steam can inhibit the oxidation of HCN to NO. Together, these effects reduce NO formation. The shifting drive mechanism can move the gas gun axially back and forth, controlling the flame position to suit different combustion power levels. At low power, the gas gun can be moved backward to increase the heat exchange area and ensure that the water in the steam coil is fully heated to convert into superheated steam; at high power, the gas gun is moved forward to prevent insufficient cooling of the primary flame and damage to the steam coil due to overheating.

[0009] Furthermore, a flow regulating valve is provided on the water inlet pipe of the steam coil.

[0010] By adopting the above-mentioned preferred scheme, it is convenient to adjust the amount of water vapor produced according to changes in combustion power and air-fuel ratio. Increasing the water flow rate at high power suppresses the occurrence of high-temperature zones, while maintaining a reasonable ratio between the amount of water vapor and the total amount of flue gas produced by combustion, thereby improving the effect of reducing NOx emissions.

[0011] Furthermore, the volume of water vapor generated by the steam coil accounts for 5%-8% of the total flue gas volume generated by combustion.

[0012] The above-mentioned preferred scheme, with a reasonable ratio range, has a good effect on reducing NOx emissions.

[0013] Furthermore, it also includes a detector for detecting the temperature of the heated coil.

[0014] By adopting the above-mentioned preferred scheme, it is convenient to monitor the temperature of the heated coil and prevent insufficient primary flame cooling and damage to the heated coil caused by overheating.

[0015] Furthermore, a flow equalization plate is provided inside the fire shield tube behind the gas nozzle.

[0016] By adopting the above-mentioned preferred scheme, the uniformity of the combustion-supporting gas entering the gas nozzle is improved, and the stability of flame establishment is enhanced.

[0017] Furthermore, the flow rate of the combustion-supporting gas entering the inner cavity of the fire shield through the second air inlet accounts for 40%-45% of the total flow rate of the combustion-supporting gas input from the first air inlet.

[0018] By adopting the above-mentioned preferred scheme, the staged combustion effect is improved, the flame temperature is reduced, and NOx emissions are reduced.

[0019] Furthermore, the heating coil of the steam coil includes an outer spiral coil and an inner spiral coil connected together, wherein the inner diameter of the outer spiral coil is larger than the outer diameter of the inner spiral coil.

[0020] By adopting the above-mentioned preferred scheme, the heating effect is improved and the uniformity of primary flame cooling is enhanced.

[0021] Furthermore, the outer ring diameter of the outer spiral coil is 75%-90% of the inner diameter of the fire shield, the inner ring diameter of the inner spiral coil is 45%-55% of the inner diameter of the fire shield, and the distance between the inner ring of the outer spiral coil and the outer ring of the inner spiral coil is greater than 5mm.

[0022] By adopting the above-mentioned preferred scheme, both flame stability and flame cooling effect are kept in a better state.

[0023] Furthermore, the multiple steam outlet holes on the steam ejection ring pipe are distributed in a circular pattern.

[0024] By adopting the above-mentioned preferred scheme, the uniformity of water vapor ejection is improved.

[0025] Furthermore, taking the diameter of the circumference of the multiple steam outlet holes as D1, the outer diameter of the fire shield as D2, and the inner diameter of the secondary air shell as D3, then (D2+D3) / 2≤D1≤1.1*(D2+D3) / 2.

[0026] Furthermore, taking the outer diameter of the steam ejection ring pipe as d, then (D3-D2) / 6≤d≤(D3-D2) / 3.

[0027] Furthermore, the front end of the fire shield is provided with a forward-shrinking inward portion, the angle between the inward portion and the axial direction is 30°-45°, and the length of the inward portion in the axial direction is 10%D2-20%D2.

[0028] Furthermore, an inwardly retracting retaining ring is provided on the inner wall of the secondary air casing at a position corresponding to the inwardly retracting part. The angle between the inwardly retracting retaining ring and the axial direction is 30°-45°. With the inner diameter of the small opening at the front end of the inwardly retracting retaining ring as D4, then 0.95*(D2+D3) / 2≤D4≤1.05*(D2+D3) / 2.

[0029] By adopting the above-mentioned preferred scheme, the steam ejection ring pipe provides a certain resistance in the secondary air duct to achieve the rectification effect of the secondary air. It cooperates with the inner recess of the fire shield and the inner recess of the secondary air shell to ensure the mixing effect of water vapor and secondary air without generating excessive resistance to the secondary air, thereby further improving the effect of reducing NOx emissions by utilizing water vapor.

[0030] Furthermore, the gas nozzle includes a plurality of first gas holes extending forward along the axial direction, a plurality of second gas holes arranged at 45° to the axial direction, and a plurality of third gas holes arranged at 90° to the axial direction.

[0031] Furthermore, the total opening area of ​​the first gas orifice accounts for 40%-50% of the total opening area of ​​all gas orifices.

[0032] Furthermore, the total opening area of ​​the second gas hole is 0.8-1.2 times the total opening area of ​​the third gas hole.

[0033] By adopting the above-mentioned preferred scheme, the gas holes in the three directions of the gas nozzle are matched with the double-layer heating coil to ensure a uniform temperature field.

[0034] Furthermore, the displacement drive mechanism includes a lead screw motor connected to the fixed sleeve, and an ear plate with a threaded hole is fixedly connected to the gun body of the gas gun, with the lead screw of the lead screw motor connected to the threaded hole of the ear plate.

[0035] The preferred design described above has a compact structure and allows for rapid adjustment of the gas gun's forward and backward position.

[0036] The burner adjustment method includes the following steps:

[0037] Step 1: Calculate the total flue gas volume generated by combustion based on the amount of gas and combustion-supporting gas in the burner, and adjust the flow regulating valve of the water inlet pipe of the steam coil so that the volume of water vapor generated by the steam coil accounts for 5%-8% of the total flue gas volume generated by combustion.

[0038] Step 2: Detect the temperature of the heating coil using a detector. When the temperature of the heating coil exceeds the set range, move the gas gun forward using a shifting drive mechanism. When the temperature of the heating coil is below the set range, move the gas gun backward using a shifting drive mechanism until the temperature of the heating coil is within the set range.

[0039] By employing the aforementioned burner adjustment method, maintaining the water vapor quantity and the total flue gas volume generated by combustion within a reasonable ratio range effectively reduces NOx emissions. The shifting drive mechanism can move the gas gun axially back and forth, controlling the flame position to suit different combustion power levels. At low power, the gas gun can be moved backward to increase the heat exchange area and ensure that the water in the steam coil is fully heated to convert into superheated steam; at high power, the gas gun is moved forward to prevent insufficient primary flame cooling and coil damage caused by overheating of the steam coil. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a schematic diagram of the burner structure of the present invention.

[0042] Figure 2 This is one of the cross-sectional views of the burner of the present invention.

[0043] Figure 3 This is a second cross-sectional view of the burner of the present invention.

[0044] Figure 4 This is a schematic diagram of the steam coil structure.

[0045] Figure 5 This is a structural schematic diagram of the gas gun and its shifting drive mechanism.

[0046] The numbers and letters in the diagram represent the names of the corresponding components:

[0047] 10-Air inlet housing; 11-First air inlet; 12-Fixing sleeve; 20-Secondary air housing; 21-Inner retractable retaining ring; 30-Flame shield; 31-Second air inlet; 32-Flow equalization orifice plate; 33-Inner retractable part; 40-Steam coil; 41-Water inlet pipe; 42-Heating coil; 421-Outer spiral coil; 422-Inner spiral coil; 43-Steam ejection ring pipe; 431-Steam outlet hole; 44-Flow regulating valve; 50-Gas gun; 51-Gas inlet; 52-Gas nozzle; 521-First gas hole; 522-Second gas hole; 523-Third gas hole; 53-Spark plug; 60-Shifting drive mechanism; 61-Screw motor; 62-Screw; 63-Ear plate. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] For ease of description of technical features, the directional descriptions of "front" and "rear" in this invention refer to the direction in which the flame from the ignition gun is emitted as the front.

[0050] like Figure 1-5 As shown, one embodiment of the present invention is: a staged burner that uses water vapor to reduce NOx emissions, comprising an air inlet housing 10, a steam coil 40, a secondary air housing 20, a flame shield 30, a gas gun 50, and a shifting drive mechanism 60.

[0051] The air inlet housing 10 is provided with a first air inlet 11 for inputting combustion-supporting gas, and the tail end of the fire shield 30 is provided with a second air inlet 31. The secondary air housing 20 is installed at the front end of the air inlet housing 10, and the fire shield 30 is installed inside the secondary air housing 20. Part of the combustion-supporting gas input from the first air inlet 11 enters the space between the secondary air housing 20 and the fire shield 30, and the other part enters the inner cavity of the fire shield 30 through the second air inlet 31.

[0052] The gas gun 50 is provided with a gas inlet 51 for inputting gas, a gas nozzle 52 at the front end of the gas gun 50, and a spark plug 53 for ignition. The gas gun 50 is movably mounted on the fixed sleeve 12 of the air inlet housing 10. The front end of the gas gun 50 is located in the inner cavity of the flame shield 30. The shifting drive mechanism 60 is used to drive the gas gun 50 to move back and forth along the axial direction of the flame shield 30.

[0053] The steam coil 40 includes a water inlet pipe 41, a heating coil 42 and a steam ejection ring pipe 43 connected in sequence. The heating coil 42 is located in the inner cavity of the fire shield 30, and the steam ejection ring pipe 43 is located between the secondary air shell 20 and the fire shield 30. The steam ejection ring pipe 43 is provided with a plurality of steam outlet holes 431 facing forward.

[0054] The beneficial effects of adopting the above technical solution are as follows: Water enters from the inlet pipe of the steam coil, cooling the primary flame burning inside the flame shield, preventing localized high temperatures, and reducing NOx emissions in the primary combustion zone. Simultaneously, the steam generated by the heating is ejected from the steam outlet hole of the steam ejection ring pipe. The steam mixes with secondary air in the secondary air shell and participates in secondary combustion. The OH and H groups produced by the decomposition of the steam can initiate a chain reaction with the CO produced in the primary combustion. The reactions H+O2→OH+O and O+H2→OH+H enhance the reducing atmosphere, facilitating the homogeneous reduction reaction of NO. Simultaneously, the H and OH free radicals generated from the dissociation of water vapor inhibit the oxidation of HCN to NO, resulting in a reduction in NO formation. The shifting drive mechanism moves the gas gun axially back and forth, controlling the flame position to suit different combustion power levels. At low power, the gas gun can be moved backward to increase the heat exchange area and ensure that the water in the steam coil is fully heated to convert into superheated steam; at high power, the gas gun is moved forward to prevent insufficient primary flame cooling and coil damage due to overheating of the steam coil.

[0055] like Figure 2 , 4 As shown, in some other embodiments of the present invention, a flow regulating valve 44 is provided on the water inlet pipe 41 of the steam coil 40. The beneficial effects of adopting the above technical solution are: it facilitates the adjustment of the amount of steam generated according to changes in combustion power and air-fuel ratio. Increasing the water flow rate at high power suppresses the occurrence of high-temperature zones, while maintaining a reasonable ratio between the amount of steam and the total amount of flue gas generated by combustion, thereby improving the effect of reducing NOx emissions.

[0056] In other embodiments of the present invention, the volume of water vapor generated by the steam coil 40 accounts for 5%-8% of the total flue gas volume generated by combustion. The beneficial effect of adopting the above technical solution is that the reasonable proportion range has a better effect on reducing NOx emissions.

[0057] In other embodiments of the present invention, a detector for detecting the temperature of the heated coil 42 is also included. The advantages of employing the above technical solution are: it facilitates monitoring the temperature of the heated coil, preventing insufficient primary flame cooling and damage to the heated coil due to overheating.

[0058] like Figure 2 As shown, in some other embodiments of the present invention, a flow equalization plate 32 is provided inside the flame shield 30 behind the gas nozzle 52. The beneficial effects of adopting the above technical solution are: improving the uniformity of the combustion-supporting gas entering the gas nozzle and improving the stability of flame establishment.

[0059] In other embodiments of the present invention, the flow rate of the combustion-supporting gas entering the inner cavity of the flame shield 30 through the second air inlet 31 accounts for 40%-45% of the total flow rate of the combustion-supporting gas input from the first air inlet 11. The beneficial effects of adopting the above technical solution are: improving the staged combustion effect, reducing the flame temperature, and reducing NOx emissions.

[0060] like Figure 3 , 4As shown, in some other embodiments of the present invention, the heating coil 42 of the steam coil includes an outer spiral coil 421 and an inner spiral coil 422 connected to each other, wherein the inner diameter of the outer spiral coil 421 is larger than the outer diameter of the inner spiral coil 422. The beneficial effects of adopting the above technical solution are: improved heating effect and uniformity of primary flame cooling.

[0061] In other embodiments of the present invention, the outer ring diameter of the outer spiral coil 421 is 75%-90% of the inner diameter of the flame shield 30, the inner ring diameter of the inner spiral coil 422 is 45%-55% of the inner diameter of the flame shield 30, and the distance between the inner ring of the outer spiral coil 421 and the outer ring of the inner spiral coil 422 is greater than 5mm. The beneficial effect of adopting the above technical solution is that it maintains both flame stability and flame cooling effect in a relatively optimal state.

[0062] like Figure 4 As shown, in some other embodiments of the present invention, the plurality of steam outlet holes 431 on the steam ejection ring pipe 43 are distributed in a circular pattern. The beneficial effect of adopting the above technical solution is to improve the uniformity of water vapor ejection.

[0063] like Figure 2 , 3 As shown, in some other embodiments of the present invention, the front end of the fire shield 30 is provided with a forward-retracting inward portion 33.

[0064] like Figure 2 , 3 As shown, in some other embodiments of the present invention, a forward-retracting retaining ring 21 is provided on the inner wall of the secondary air housing 20 at a position corresponding to the inward retraction portion 33.

[0065] like Figure 3As shown, in some other embodiments of the present invention, with the diameter of the circumference of the center of the plurality of steam outlet holes 431 as D1, the outer diameter of the fire shield 30 as D2, and the inner diameter of the secondary air shell 20 as D3, then (D2+D3) / 2≤D1≤1.1*(D2+D3) / 2. With the outer diameter of the steam ejection ring pipe 43 as d, then (D3-D2) / 6≤d≤(D3-D2) / 3. The angle between the conical surface of the inward-retracting portion 33 and the axial direction is 30°-45°, and the axial length of the inward-retracting portion 33 is 10%D2-20%D2. The angle between the conical surface of the inward-retracting retaining ring 21 and the axial direction is 30°-45°, and with the inner diameter of the small opening at the front end of the inward-retracting retaining ring 21 as D4, then 0.95*(D2+D3) / 2≤D4≤1.05*(D2+D3) / 2. The beneficial effects of adopting the above technical solution are: the steam ejection ring pipe provides a certain resistance in the secondary air duct to achieve the rectification effect of the secondary air, and cooperates with the inner recess of the fire shield and the inner recess of the secondary air shell to ensure the mixing effect of water vapor and secondary air without generating excessive resistance to the secondary air, thereby further improving the effect of using water vapor to reduce NOx emissions.

[0066] like Figure 5 As shown, in some embodiments of the present invention, the gas nozzle 52 includes a plurality of first gas holes 521 extending forward along the axial direction, a plurality of second gas holes 522 arranged at 45° to the axial direction, and a plurality of third gas holes 523 arranged at 90° to the axial direction. The beneficial effect of adopting the above technical solution is that the gas holes in the three directions of the gas nozzle cooperate with the double-layer heating coil to ensure a uniform temperature field.

[0067] In other embodiments of the present invention, the total opening area of ​​the first gas hole 521 accounts for 40%-50% of the total opening area of ​​all gas holes.

[0068] In some other embodiments of the present invention, the total opening area of ​​the second gas hole 522 is 0.8-1.2 times the total opening area of ​​the third gas hole 523.

[0069] like Figure 5 As shown, in some other embodiments of the present invention, the shifting drive mechanism 60 includes a lead screw motor 61 connected to the fixed sleeve 12, and an ear plate 63 with a threaded hole is fixedly connected to the body of the gas gun 50. The lead screw 62 of the lead screw motor is connected to the threaded hole of the ear plate 63. The beneficial effects of adopting the above technical solution are: compact structure and ability to quickly adjust the forward and backward position of the gas gun.

[0070] The burner adjustment method includes the following steps:

[0071] Step 1: Calculate the total flue gas volume generated by combustion based on the amount of gas and combustion-supporting gas in the burner, and adjust the flow regulating valve of the water inlet pipe of the steam coil so that the volume of water vapor generated by the steam coil accounts for 5%-8% of the total flue gas volume generated by combustion.

[0072] Step 2: Detect the temperature of the heating coil using a detector. When the temperature of the heating coil exceeds the set range, move the gas gun forward using a shifting drive mechanism. When the temperature of the heating coil is below the set range, move the gas gun backward using a shifting drive mechanism until the temperature of the heating coil is within the set range.

[0073] By employing the aforementioned burner adjustment method, maintaining the water vapor quantity and the total flue gas volume generated by combustion within a reasonable ratio range effectively reduces NOx emissions. The shifting drive mechanism can move the gas gun axially back and forth, controlling the flame position to suit different combustion power levels. At low power, the gas gun can be moved backward to increase the heat exchange area and ensure that the water in the steam coil is fully heated to convert into superheated steam; at high power, the gas gun is moved forward to prevent insufficient primary flame cooling and coil damage caused by overheating of the steam coil.

[0074] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A staged burner for reducing NOx emissions using water vapor, characterized in that, It includes an air inlet housing, a steam coil, a secondary air housing, a flame shield, a gas gun, and a shifting drive mechanism; The air inlet housing is provided with a first air inlet for inputting combustion-supporting gas, and the tail end of the fire shield is provided with a second air inlet. The secondary air housing is installed at the front end of the air inlet housing, and the fire shield is installed inside the secondary air housing. Part of the combustion-supporting gas input from the first air inlet enters the space between the secondary air housing and the fire shield, and the other part enters the inner cavity of the fire shield through the second air inlet. The gas gun is provided with a gas inlet for inputting gas, a gas nozzle is provided at the front end of the gas gun, and a spark plug for ignition is also provided on the gas gun. The gas gun is movably installed on the fixed sleeve of the air inlet housing. The front end of the gas gun is located in the inner cavity of the fire shield tube. The displacement drive mechanism is used to drive the gas gun to move back and forth along the axis of the fire shield tube. The steam coil includes a water inlet pipe, a heating coil, and a steam ejection ring pipe connected in sequence. The heating coil is located inside the fire shield, and the steam ejection ring pipe is located between the secondary air shell and the fire shield. The steam ejection ring pipe is provided with multiple steam outlet holes facing forward.

2. The staged burner for reducing NOx emissions using water vapor according to claim 1, characterized in that, The steam coil is equipped with a flow regulating valve on its water inlet pipe, and the volume of water vapor generated by the steam coil accounts for 5%-8% of the total volume of flue gas generated by combustion.

3. The staged burner for reducing NOx emissions using water vapor according to claim 2, characterized in that, It also includes a detector for detecting the temperature of the heated coil.

4. The staged burner for reducing NOx emissions using water vapor according to claim 1, characterized in that, The fire shield is equipped with a flow equalization plate located behind the gas nozzle.

5. The staged burner for reducing NOx emissions using water vapor according to claim 1, characterized in that, The flow rate of combustion-supporting gas entering the inner cavity of the fire shield through the second air inlet accounts for 40%-45% of the total flow rate of combustion-supporting gas input from the first air inlet.

6. The staged burner for reducing NOx emissions using water vapor according to claim 1, characterized in that, The heating coil of the steam coil includes an outer spiral coil and an inner spiral coil connected together, wherein the inner diameter of the outer spiral coil is larger than the outer diameter of the inner spiral coil.

7. The staged burner for reducing NOx emissions using water vapor according to claim 6, characterized in that, The outer diameter of the outer spiral coil is 75%-90% of the inner diameter of the fire shield, the inner diameter of the inner spiral coil is 45%-55% of the inner diameter of the fire shield, and the distance between the inner circle of the outer spiral coil and the outer circle of the inner spiral coil is greater than 5mm.

8. The staged burner for reducing NOx emissions using water vapor according to claim 1, characterized in that, The multiple steam outlet holes on the steam ejection ring pipe are distributed in a circle. With the diameter of the circle containing the center of the multiple steam outlet holes as D1, the outer diameter of the fire shield tube as D2, and the inner diameter of the secondary air shell as D3, then (D2+D3) / 2≤D1≤1.1*(D2+D3) / 2. If the outer diameter of the steam ejection ring pipe is d, then (D3-D2) / 6≤d≤(D3-D2) / 3; The front end of the fire shield is provided with a forward-retracting inward section, the angle between the inward section and the axial direction is 30°-45°, and the length of the inward section in the axial direction is 10%D2-20%D2. An inwardly retracting retaining ring is provided on the inner wall of the secondary air casing at a position corresponding to the inwardly retracting part. The angle between the inwardly retracting retaining ring and the axial direction is 30°-45°. With the inner diameter of the small opening at the front end of the inwardly retracting retaining ring as D4, then 0.95*(D2+D3) / 2≤D4≤1.05*(D2+D3) / 2.

9. The staged burner for reducing NOx emissions using water vapor according to claim 1, characterized in that, The gas nozzle includes a plurality of first gas holes facing forward along the axial direction, a plurality of second gas holes set at 45° to the axial direction, and a plurality of third gas holes set at 90° to the axial direction. The total opening area of ​​the first gas holes accounts for 40%-50% of the total opening area of ​​all gas holes, and the total opening area of ​​the second gas holes is 0.8-1.2 times the total opening area of ​​the third gas holes.

10. A burner adjustment method, characterized in that, The staged burner for reducing NOx emissions using water vapor as described in claim 3 includes the following steps: Step 1: Calculate the total flue gas volume generated by combustion based on the amount of gas and combustion-supporting gas in the burner, and adjust the flow regulating valve of the water inlet pipe of the steam coil so that the volume of water vapor generated by the steam coil accounts for 5%-8% of the total flue gas volume generated by combustion. Step 2: Detect the temperature of the heating coil using a detector. When the temperature of the heating coil exceeds the set range, move the gas gun forward using a shifting drive mechanism. When the temperature of the heating coil is below the set range, move the gas gun backward using a shifting drive mechanism until the temperature of the heating coil is within the set range.

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