WO2023216529A1 - Gas-air double-stage ultralow-nitrogen bottom combustor and combustion method therefor - Google Patents

Abstract

Provided are a gas-air double-stage ultralow-nitrogen bottom combustor. The gas-air double-stage ultralow-nitrogen bottom combustor mainly comprises an air box, an air inlet, an air inlet partition plate, an air box partition plate, a first-stage gas spray gun and a second-stage gas spray gun; the air inlet is installed on the air box, the air inlet partition plate divides the air inlet into a primary air inlet and a secondary air inlet, the air box partition plate divides the interior of the air box into a primary air area and a secondary air area, the first-stage gas spray gun is mounted in the primary air area, and the second-stage gas spray gun penetrates through the secondary air area and a burner brick and extends into a hearth. In the gas-air double-stage ultralow-nitrogen bottom combustor, the emission of NO _X is effectively reduced by means of a combustion organization mode of coupling of overall gas grading and local air grading; and further by means of the design of the first-stage gas spray head and the second-stage gas spray head, stable and reliable combustion is guaranteed, the temperature field is uniform, and NO _X emission is further reduced. The invention further provides a combustion method for the combustor.

Description

A gas-air dual-stage ultra-low nitrogen bottom burner and its combustion method

This application requests the priority of the Chinese patent application submitted to the China Patent Office on May 7, 2022, with the application number 202210494766.4 and the invention title "A gas-air dual-stage ultra-low nitrogen bottom burner and its combustion method", which The entire contents are incorporated herein by reference.

Technical field

The invention relates to a gas-air dual-stage ultra-low nitrogen bottom burner and a combustion method thereof, and belongs to the technical field of burners.

Background technique

Nitrogen oxides (NOx) are one of the main sources of air pollution. They are toxic to humans, animals and plants, and are an important factor in the formation of haze (PM2.5), acid rain, and acid fog. The harm _{of NO} High-temperature petrochemical heating furnaces such as cracking furnaces mostly use gas as fuel, and their _NOx emissions usually exceed national environmental protection emission requirements. Under the promotion of new environmental protection standards, burners are required to achieve lower _NOx emissions. At present, many low _NOx technologies are used at home and abroad, including staged combustion, rich and light combustion, flue gas recirculation technology, etc. As the requirements for _NOx emission indicators become more stringent, conventional low-nitrogen burners can no longer meet the requirements for reducing _NOx emissions.

Contents of the invention

The technical problem solved by the present invention is to overcome the shortcomings of the existing technology and provide a gas-air double-stage ultra-low nitrogen bottom burner and its combustion method, which can effectively reduce _NOx emissions and ensure stable and reliable combustion and uniform temperature field.

The technical solution of the present invention is:

A gas-air double-stage ultra-low nitrogen bottom burner includes an air box, an air inlet, an air inlet partition, an air box partition, a first-level gas spray gun, and a second-level gas spray gun. The air inlet is installed on the air box, so The air inlet partition divides the air inlet into a primary air inlet and a secondary air inlet. The air box partition divides the interior of the air box into a primary air area and a secondary air area. The air box partition is in contact with the air inlet. The air inlet partitions are vertically connected, and the combustion-supporting air enters the primary air area through the primary air inlet, and enters the secondary air area through the secondary air inlet; the first-level gas spray gun is installed on the first-level The wind area is parallel to the wind box partition, and the first-level gas nozzle is installed on the head of the first-level gas nozzle. The first-level gas nozzle is used to form a V-shaped plane flame; the second-level gas nozzle passes through the secondary air The area extends into the furnace, and a secondary gas nozzle is installed on the head of the secondary gas nozzle. The secondary gas nozzle includes at least 2 layers of nozzle holes, and each layer includes at least 2 nozzle holes.

Preferably, the first-level gas nozzle is provided with two rows of nozzle holes evenly distributed along the axial direction.

Preferably, the angle between the spray directions of the two rows of nozzle holes is 40° to 120°.

Preferably, the total number of the two rows of nozzle holes is 10 to 60.

Preferably, the length of the first-level gas nozzle accounts for more than 40% of the cross-sectional length of the primary air area.

Preferably, a V-shaped flame stabilizer is installed on the first-level gas nozzle, and the angle between two sides of the V-shaped flame stabilizer is consistent with the angle between the injection directions of the two rows of nozzle holes in the first-level gas nozzle.

Preferably, there are openings on both sides of the V-shaped flame stabilizer, and any nozzle hole of the first-level gas nozzle is located between two adjacent openings of the V-shaped flame stabilizer.

Preferably, the air inlet is equipped with air inlet adjustment handles for primary air and secondary air adjustment respectively.

Preferably, the outlet section of the secondary air area is a contraction channel with a smaller cross-sectional area.

Preferably, the secondary gas nozzle includes three layers of nozzle holes, namely a first layer of nozzle holes, a second layer of nozzle holes, and a third layer of nozzle holes.

Preferably, the angle α between the injection direction of the first layer nozzle hole and the axis of the secondary gas nozzle satisfies 15°≤α≤25°.

Preferably, the angle β between the injection direction of the second layer nozzle holes and the axis of the secondary gas nozzle satisfies 30°≤β≤45°.

Preferably, the angle θ between the injection direction of the third layer nozzle hole and the axis of the secondary gas nozzle satisfies 50°≤θ≤65°.

Preferably, the number of nozzle holes in the first layer is 3, the middle nozzle hole is the first middle nozzle hole, and the nozzle holes on both sides are symmetrically distributed with the first middle nozzle hole as the center.

Preferably, the number of nozzle holes in the second layer is 2, and they are arranged in the middle of the intervals between the nozzle holes in the first layer.

Preferably, the number of nozzle holes in the third layer is 3, the middle nozzle hole is the second middle nozzle hole, the horizontal position of the second middle nozzle hole is consistent with the first middle nozzle hole, and the remaining two nozzle holes are in the third layer. The two middle nozzles are distributed symmetrically about the center.

Preferably, the diameter of the nozzle holes in the first layer is greater than 3 mm.

Preferably, the gas flow rate injected by the first layer of nozzle holes is greater than 50% of the total gas flow rate of the burner.

Preferably, the diameter of the nozzle holes in the second layer is 3mm.

Preferably, the gas flow rate injected by the second layer nozzle holes is 10% to 15% greater than the total gas flow rate of the burner.

Preferably, the diameter of the nozzle holes of the third layer is 2 mm.

Preferably, the gas flow rate injected by the third layer nozzle holes is 3% to 5% greater than the total gas flow rate of the burner.

Preferably, it also includes a continuous light, and the continuous light is installed in the secondary air area.

A combustion method for a gas-air dual-stage ultra-low nitrogen bottom burner, including the following steps:

S201: Use the first-level gas nozzle to spray gas, mix it with the combustion air in the primary air area for first-level combustion, and adjust the primary combustion air volume through the air inlet adjustment handle to make the first-level combustion a hypoxic combustion far away from the chemically appropriate ratio; gas A V-shaped plane primary flame is formed through the primary gas nozzle, and a low-speed reflow area is further formed through the V-shaped flame stabilizer;

S202: Mix the unburned gas in the primary combustion and the flue gas generated in the combustion with the combustion air in the secondary air area to perform secondary combustion;

S203: Use the secondary gas lance to inject the furnace flue gas into the secondary combustion area to mix with the flue gas generated by primary combustion and secondary combustion to perform third-level combustion.

The advantages of the present invention compared with the prior art are:

(1) A gas-air dual-stage ultra-low nitrogen bottom burner provided by the present invention adopts a combustion organization mode that couples overall gas classification and local air classification to effectively reduce the amount of NO _X generated;

(2) The present invention provides a gas-air double-stage ultra-low nitrogen bottom burner. The first-level gas nozzle adopts a T-shaped porous gas nozzle to form a long V-shaped plane flame, and the gas is mixed and burned with all the primary air as quickly as possible to avoid Generate local hotspot areas;

(3) In a gas-air dual-stage ultra-low nitrogen bottom burner provided by the present invention, the first-stage flame and the air-staged partition are parallel to ensure that the second-stage air can meet the first-stage flame evenly and the flame temperature field is uniform;

(4) The present invention provides a gas-air dual-stage ultra-low nitrogen bottom burner. The first-stage gas nozzle is equipped with a V-shaped flame stabilizer to form a low-speed reflow area. On the basis of improving the stability of the low-nitrogen combustion flame, it further Reduce _NOx production;

(5) The present invention provides a gas-air dual-stage ultra-low nitrogen bottom burner that adjusts the ratio of primary air and secondary air through the air inlet adjustment handle to achieve ideal expected combustion effects under different working conditions and improve ignition stability. performance, reducing _NOx emissions;

(6) The present invention provides a gas-air dual-stage ultra-low nitrogen bottom burner. The secondary gas nozzle adopts a three-layer nozzle structure to ensure stable and reliable combustion, improve the uniformity of the secondary combustion reaction, and reduce the secondary combustion reaction. Generation of NO _X in the area;

(7) Using the gas-air dual-stage ultra-low nitrogen bottom burner cracking furnace or other high-temperature furnace heating furnace (furnace temperature > 1050°C) provided by the present invention can achieve NO _X emissions of less than 55 mg/Nm ³ under normal operating conditions. , NO _X emissions less than 30 mg/Nm ³ can be achieved in a heating furnace with a lower furnace temperature.

Description of the drawings

Figure 1 is a schematic structural diagram of a gas-air dual-stage ultra-low nitrogen bottom gas burner of the present invention;

Figure 2 is a schematic structural diagram of the first-stage T-shaped porous gas nozzle of the present invention;

Figure 3 is a schematic assembly diagram of the first-stage T-shaped porous gas nozzle and V-shaped flame stabilizer of the present invention;

Figure 4 is a schematic structural diagram of a two-stage gas nozzle of the present invention, where Figure 4(a) is a side view and Figure 4(b) is a front view;

Detailed ways

The invention provides a gas-air dual-stage ultra-low nitrogen bottom burner and a combustion method thereof that couple the overall gas classification and local air classification.

Figure 1 shows a preferred embodiment of a gas-air dual-stage ultra-low nitrogen bottom burner provided by the present invention. As shown in Figure 1, the burner mainly includes: air box 4, air inlet 1, air inlet partition 2, air box partition 10, first-level gas spray gun 5, second-level gas spray gun 7, and constant light 6. An air inlet 1 is installed on the air box 4, and an air box partition 10 and an air inlet partition 2 are respectively provided in the burner air box 4 and the air inlet 1. The air inlet partition 2 divides the combustion air into primary air and secondary air and enters the interior of the air box 4. The air box partition 2 is parallel to the longitudinal axis of the air box and divides the interior of the air box 4 into a primary air area and a secondary air area. The air inlet partition 2 and the wind box partition 10 are vertical and connected by welding; the outlet section of the primary air area is a straight channel with a constant cross-sectional area. The outlet section of the secondary air area is a contraction channel with a smaller cross-sectional area, which increases the speed of the secondary air to fully mix it with the primary flame. The first-level gas spray gun 5 penetrates from the bottom 4 of the wind box and is installed in the first-level air area through the air inlet partition 2. The first-level gas spray gun 5 is parallel to the wind box partition 10. The first-level gas nozzle 12 is installed on the head of the first-level gas nozzle 5 for forming a long V-shaped plane flame; the second-level gas nozzle 7 passes through the bottom of the wind box 4, the secondary air area and the burner brick 9 and extends into the furnace. , a secondary gas nozzle 8 is installed on the head of the secondary gas nozzle 7; the secondary gas nozzle 8 ejects the furnace flue gas and then enters the primary combustion area for combustion; preferably, the burner also includes a permanent light 6, which passes through The bottom of the air box is installed in the secondary air area.

The burner adopts a gas classification method as a whole. The first-level gas and combustion-supporting air are mixed and burned. The second-level gas nozzle injects the furnace flue gas and then enters the first-level combustion area for combustion. The first-level combustion area is the key area for generating NO _X. Since The combustion here is direct combustion of fresh air and gas, and the amount of _NOx produced is consistent with conventional diffusion combustion. The present invention significantly reduces _{the NO}

Preferably, two air inlet adjusting handles 3 are installed on the burner air box 4, which are respectively responsible for adjusting the primary air and secondary air volumes. By adjusting the proportion of the primary air and the secondary air by adjusting the air inlet adjusting handle 3 Adjustments are made to achieve the ideal desired combustion effect under different operating conditions. During ignition and small load operation, by adjusting the primary air volume, the primary combustion area is close to the chemical ratio, and the air excess coefficient is between 0.9 and 1.3, thereby improving ignition stability and achieving a higher regulation ratio; during large load operation , by adjusting the primary air volume to keep the primary combustion area away from the chemically appropriate ratio, the air excess coefficient is between 0.6~0.9 or 1.6~2.3, reducing _NOx emissions.

Preferably, the first-level gas nozzle 12 is a T-shaped multi-hole gas nozzle. As shown in Figure 2, the first-level gas nozzle has two rows of nozzle holes evenly distributed along the circumferential direction. The line between the nozzle hole and the axis is The angle λ between them is 40° to 120°, the total number of the two rows of nozzle holes is 10 to 60, and the length accounts for more than 40% of the channel cross-sectional length. When the first-level gas nozzle 12 performs a combustion reaction, a long V-shaped plane flame is formed. The flame length accounts for more than 40% of the cross-sectional length of the primary air area. The gas is mixed and burned with all the primary air as quickly as possible, which significantly improves the uniformity of the combustion temperature field. , to avoid the generation _of thermal _NO

Further, a V-shaped flame stabilizer 11 is installed on the first-level gas nozzle 12. As shown in Figure 3, the V-shaped flame stabilizer 11 is a low-nitrogen flame stabilizer with porous spaced distribution. Preferably, the V-shaped flame stabilizer is The angle between both sides of the device is 40° to 120°, which is consistent with the angle between the two rows of nozzle holes of the first-level gas nozzle 12 and the axis; it is opened 1/3 to 2/3 away from the V-shaped tip on both sides. hole, the opening rate is 3% to 15%, the hole diameter is ≤4mm; the length of the V-shaped flame stabilizer accounts for more than 40% of the cross-sectional length of the primary air area, and the cross-sectional area accounts for more than 35% of the entire primary air flow area; the first-level The injection direction of each nozzle hole of the gas nozzle 12 is located between the openings of the V-shaped flame stabilizer 11 to ensure that when the primary air and the primary gas nozzle meet, each nozzle hole is sprayed at the low speed of the return flow formed by the orifice plate of the V-shaped flame stabilizer 11 In this area, on the basis of improving the combustion stability of low-nitrogen flame, a small amount of air is injected through the small holes to partially react the gas. In a reducing environment, the methane in the gas can reduce part of NO, further reducing _NOx emissions.

Preferably, the secondary gas nozzle 8 has a three-layer structure, as shown in Figure 4(b), including a first layer of nozzle holes, a second layer of nozzle holes, and a third layer of nozzle holes. As shown in Figure 4(a), the angle between the first layer nozzle hole and the 8-axis axis of the secondary gas nozzle satisfies 15°≤α≤25°, and the angle between the second layer nozzle hole and the secondary gas nozzle axis satisfies 15°≤α≤25°. The angle between the 8 axes of the nozzle meets 30° ≤ β ≤ 45°, and the angle between the third layer nozzle holes and the 8 axes of the secondary gas nozzle satisfies 50° ≤ θ ≤ 65°. The number of nozzle holes in the first layer is 3, and the nozzle holes on both sides are symmetrically distributed with the middle nozzle hole as the center. The nozzle holes in this layer are the flame holes at the top of the secondary combustion. The diameter of the nozzle holes is greater than 3mm, and the gas flow rate injected is greater than 50% of the total gas flow rate, thereby significantly increasing the length of the combustion flame and reducing the combustion reaction speed. The number of nozzle holes in the second layer is 2, and the horizontal position of the nozzle holes is in the middle of the intervals between the nozzle holes in the first layer. The nozzle holes in this layer are secondary combustion intermediate flame holes with a larger hole diameter of 3 mm, and the gas flow rate injected accounts for 10 to 15% of the total gas flow rate of the burner. The first layer of nozzle holes and the second layer of nozzle holes form a multi-layer combustion reaction area, which effectively improves the temperature exchange between the combustion area and the surrounding environment, improves the uniformity of the secondary combustion reaction, further reduces the temperature high point of the secondary combustion area, and thereby reduces the temperature of the secondary combustion area. Thermal NO _X generation in the first-stage combustion reaction zone. The number of nozzle holes in the three layers is 3, the horizontal position of the middle nozzle hole is consistent with the middle nozzle hole of the first layer of nozzle holes, and the remaining two nozzle holes are symmetrically distributed with the middle nozzle hole as the center. The nozzle holes in this layer are pilot holes with a diameter of 2 mm, and the gas flow rate injected accounts for 3 to 5% of the total gas flow rate of the burner. The lower nozzle holes quickly enter the high-temperature area at the bottom and are ignited, ensuring stable and reliable combustion.

The working process of the gas-air dual-stage ultra-low nitrogen bottom burner provided by the invention is as follows:

The first-level gas nozzle 5 sprays gas, which is mixed and burned with the combustion-supporting air in the primary air area. By adjusting the primary air volume, the first-level combustion is an oxygen-deficient combustion far away from the chemically appropriate ratio. In an oxygen-deficient combustion environment, the amount of _NO Low; a long V-shaped plane first-level flame is formed through the first-level gas nozzle 12, and the flame cross section covers the entire primary air area, significantly improving the uniformity of the combustion temperature field, thereby avoiding the thermal _NO The low-speed reflow zone formed by the flame stabilizer 11, on the basis of ensuring the flame stability, injects a small amount of air through the small holes, so that the gas reacts partially first. In the reducing environment, the methane in the gas can reduce part of the NO, further reducing the NO _X is generated.

The unburned gas in the primary combustion meets the combustion-supporting air in the secondary air area and undergoes secondary combustion; a large amount of flue gas generated in the primary combustion simultaneously participates in the combustion reaction, diluting the concentration of reactants and significantly reducing combustion and NOx production. The reaction speed; and the flow directions of the primary combustion flue gas and the secondary air are basically parallel, and the mixing flow between them is low, which further reduces the reaction speed, thereby significantly reducing the _NOx generation of the secondary combustion.

The secondary gas lance 7 injects the furnace flue gas into the secondary combustion area for third-stage combustion. The methane in the gas first reduces _{the NO} area, the flue gas generated by the primary and secondary combustion and the flue gas emitted by the secondary gas nozzle will significantly reduce the concentration of reactants in the two reactions of combustion and _NO The temperature is significantly lowered and the reaction temperature field is more uniform, ultimately reducing the generation of thermal _NOx . On the other hand, by reducing the concentration of reactants in the _NOx generation reaction, the generation of _NOx is significantly reduced.

The present invention also provides a combustion method for a gas-air dual-stage ultra-low nitrogen bottom burner as described above, which includes the following steps:

S201: Use the first-level gas spray gun 5 to eject gas, mix it with the combustion air in the primary air area to perform first-level combustion, and adjust the primary combustion air volume through the air inlet adjustment handle 3 to make the first-level combustion a hypoxic combustion far away from the chemically appropriate ratio. ; The gas passes through the first-level gas nozzle 12 to form a V-shaped plane first-level flame, and further passes through the V-shaped flame stabilizer 11 to form a low-speed reflow area;

S202: Mix the unburned gas in the primary combustion and the flue gas generated in the combustion with the combustion air in the secondary air area to perform secondary combustion;

S203: Use the secondary gas lance 7 to inject the furnace flue gas into the secondary combustion area to mix with the flue gas generated by primary combustion and secondary combustion to perform third-level combustion.

The gas-air double-stage ultra-low nitrogen bottom burner provided by the present invention can effectively reduce the emission of _NO Achieve NO _X emissions of less than 55 mg/Nm ³ under normal operating conditions. In a heating furnace with a lower furnace temperature, the _NOx emission can be less than 30 mg/Nm ³ .

Contents not described in detail in the specification of the present invention are well-known technologies to those skilled in the art.

Claims (24)

1. A gas-air dual-stage ultra-low nitrogen bottom burner, which is characterized by: including an air box (4), an air inlet (1), an air inlet partition (2), an air box partition (10), and a first-level gas spray gun (5 ), a secondary gas spray gun (7), the air inlet (1) is installed on the air box (4), and the air inlet partition (2) divides the air inlet (1) into a primary air inlet and a secondary air inlet. The air box partition (10) divides the interior of the air box (4) into a primary air area and a secondary air area. The air box partition (10) and the air inlet partition (2) ) are vertically connected, the combustion air enters the primary air area through the primary air inlet, and enters the secondary air area through the secondary air inlet; the primary gas spray gun (5) is installed on the primary air area, parallel to the bellows partition (10), the first-level gas nozzle (12) is installed on the head of the first-level gas nozzle (5), and the first-level gas nozzle (12) is used to form a V-shaped plane flame; The secondary gas nozzle (7) extends into the furnace through the secondary air area, and a secondary gas nozzle (8) is installed on the head of the secondary gas nozzle. The secondary gas nozzle (8) includes at least 2 Layer nozzle holes, each layer includes at least 2 nozzle holes.
2. A gas-air dual-stage ultra-low nitrogen bottom burner according to claim 1, characterized in that the first-stage gas nozzle (12) has two rows of nozzle holes evenly distributed along the axial direction.
3. A gas-air dual-stage ultra-low nitrogen bottom burner according to claim 2, characterized in that the angle between the injection directions of the two rows of nozzle holes is 40° to 120°.
4. A gas-air dual-stage ultra-low nitrogen bottom burner according to claim 3, characterized in that the total number of the two rows of nozzle holes is 10 to 60.
5. A gas-air dual-stage ultra-low nitrogen bottom burner according to claim 4, characterized in that the length of the first-stage gas nozzle (12) accounts for more than 40% of the cross-sectional length of the primary air area.
6. A gas-air dual-stage ultra-low nitrogen bottom burner according to claim 5, characterized in that: a V-shaped flame stabilizer (11) is installed on the first-stage gas nozzle (12), and the V-shaped flame stabilizer The angle between the two sides of the flame device (11) is consistent with the angle between the injection directions of the two rows of nozzle holes of the first-level gas nozzle (12).
7. A gas-air double-stage ultra-low nitrogen bottom burner according to claim 6, characterized in that: there are openings on both sides of the V-shaped flame stabilizer (11), and the first-level gas nozzle (12) can be A nozzle hole is located between two adjacent openings of the V-shaped flame stabilizer (11).
8. A gas-air double-stage ultra-low nitrogen bottom burner according to claim 1, characterized in that: the air inlet (1) is equipped with air inlet adjustment handles (1) for primary air and secondary air adjustment respectively. 3).
9. A gas-air double-stage ultra-low nitrogen bottom burner according to claim 1, characterized in that: the outlet section of the secondary air area is a contraction channel with a reduced cross-sectional area.
10. A gas-air double-stage ultra-low nitrogen bottom burner according to claim 1, characterized in that: the two-stage gas nozzle (8) includes three layers of nozzle holes, namely a first layer of nozzle holes, a second layer of nozzle holes, and a second layer of nozzle holes. Spray holes, third layer of spray holes.
11. A gas-air dual-stage ultra-low nitrogen bottom burner according to claim 10, characterized in that: the angle α between the injection direction of the first layer nozzle hole and the axis of the second-level gas nozzle (8) satisfies 15 °≤α≤25°.
12. A gas-air dual-stage ultra-low nitrogen bottom burner according to claim 10, characterized in that: the angle β between the injection direction of the second layer nozzle hole and the axis of the secondary gas nozzle (8) satisfies 30 °≤β≤45°.
13. A gas-air double-stage ultra-low nitrogen bottom burner according to claim 10, characterized in that: the angle θ between the injection direction of the third layer nozzle hole and the axis of the secondary gas nozzle (8) satisfies 50 °≤θ≤65°.
14. A gas-air dual-stage ultra-low nitrogen bottom burner according to claim 10, characterized in that: the number of nozzle holes in the first layer is 3, the middle nozzle hole is the first middle nozzle hole, and the nozzle holes on both sides are The first middle nozzle hole is centrally symmetrically distributed.
15. A gas-air dual-stage ultra-low nitrogen bottom burner according to claim 14, characterized in that: the number of nozzle holes in the second layer is 2, and they are arranged in the middle of the intervals between the nozzle holes in the first layer.
16. A gas-air dual-stage ultra-low nitrogen bottom burner according to claim 14, characterized in that: the number of nozzle holes in the third layer is 3, the middle nozzle hole is a second middle nozzle hole, and the second middle nozzle hole is a second middle nozzle hole. The horizontal position of the nozzle holes is consistent with the first middle nozzle hole, and the remaining two nozzle holes are symmetrically distributed with the second middle nozzle hole as the center.
17. A gas-air double-stage ultra-low nitrogen bottom burner according to claim 10, characterized in that: the diameter of the first layer of nozzle holes is greater than 3 mm.
18. A gas-air dual-stage ultra-low nitrogen bottom burner according to claim 10, characterized in that the gas flow rate injected by the first layer of nozzle holes is greater than 50% of the total gas flow rate of the burner.
19. A gas-air dual-stage ultra-low nitrogen bottom burner according to claim 10, characterized in that: the diameter of the second layer of nozzle holes is 3 mm.
20. A gas-air dual-stage ultra-low nitrogen bottom burner according to claim 10, characterized in that the gas flow rate injected by the second layer nozzle holes is 10% to 15% greater than the total gas flow rate of the burner.
21. A gas-air dual-stage ultra-low nitrogen bottom burner according to claim 10, characterized in that: the diameter of the third layer nozzle hole is 2 mm.
22. A gas-air dual-stage ultra-low nitrogen bottom burner according to claim 10, characterized in that the gas flow rate injected by the third layer nozzle holes is 3% to 5% greater than the total gas flow rate of the burner.
23. A gas-air dual-stage ultra-low nitrogen bottom burner according to claim 1, characterized in that it also includes a continuous light (6), and the continuous light (6) is installed in the secondary air area.
24. A combustion method for a gas-air dual-stage ultra-low nitrogen bottom burner, which is characterized by including the following steps:

    S201: Use the first-level gas spray gun (5) to eject gas, mix it with the combustion air in the primary air area for first-level combustion, and adjust the primary combustion air volume through the air inlet adjustment handle (3) to make the first-level combustion far away from the chemically appropriate ratio. Oxygen-deficient combustion; the gas passes through the first-level gas nozzle (12) to form a V-shaped plane first-level flame, and further passes through the V-shaped flame stabilizer (11) to form a low-speed reflow area;

    S202: Mix the unburned gas in the primary combustion and the flue gas generated in the combustion with the combustion air in the secondary air area to perform secondary combustion;

    S203: Use the secondary gas lance (7) to inject the furnace flue gas into the secondary combustion area to mix with the flue gas generated by primary combustion and secondary combustion to perform third-level combustion.

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