CN115789640A - Ultralow-nitrogen combustor and combustion method thereof - Google Patents

Abstract

The invention relates to the technical field of burners and discloses an ultralow nitrogen burner and a burning method thereof, wherein a burning head of the ultralow nitrogen burner is fixedly connected with an auxiliary burning chamber, and comprises an outer cylinder, an air inlet cylinder and a burning cylinder; an inner cylinder is coaxially arranged in the outer cylinder, and one end of the inner cylinder is open; the other end of the inner cylinder is fixedly connected with the combustion cylinder; a central gas system is arranged in the inner cylinder and comprises a central gas pipe and a central gas nozzle; the outer cylinder is provided with a main gas system, and the main gas system comprises a main gas collecting bag, a plurality of main gas branch pipes and a plurality of main gas nozzles; be provided with on the urceolus and assist the gas system, assist the gas system including assisting gas collection package, a plurality of gas branch pipes of assisting and a plurality of gas nozzle of assisting. The invention adopts a sectional combustion mode, wherein the upstream is lean premixed combustion, the downstream is inert flue gas participating in combustion, and the lean premixed combustion forms two combustion areas, so that heat exchange is generated between the two combustion areas, the combustion temperature is greatly reduced, and the generation of NOx is inhibited.

Description

Ultralow-nitrogen combustor and combustion method thereof

Technical Field

The invention belongs to the technical field of combustors, and particularly relates to an ultralow-nitrogen combustor and a combustion method thereof.

Background

The industrial boiler combustor mostly adopts the traditional combustion mode of forced air supply and diffusion, and the main purpose of the industrial boiler combustor is burnout and safety, and few measures are taken for NOx emission. Today, the main technical routes that have emerged and adopted for the environmental requirements of NOx emissions below 30mg/m 3 in some regions include staged combustion, premixed combustion and flue gas recirculation:

(1) Staged combustion of fuel or staged combustion of air

Both methods will eventually maintain the excess air factor of the entire system at a constant value. This technical system is complex and does not eliminate the high temperature zone of the flame.

(2) Lean premixed combustion technology

An advantage of this technique for controlling NOx production is that control of combustion temperature can be achieved with full control of equivalence ratio, thereby reducing the rate of thermal NOx production, and in some cases premixed combustion and partial premixing can reduce NOx production by 85% -90% over non-premixed combustion. In addition, full premixing may also reduce the reduction in NOx generation control due to excess air ratio non-uniformity. If the lean premixed burner is added with the wire mesh burner to form surface combustion, the flame is more dispersed, and the NOx emission is further reduced.

(3) External flue gas recirculation and internal flue gas recirculation techniques

The reduction of the combustion temperature can be achieved by adding flue gas in the flame zone, which absorbs heat and thereby reduces the combustion temperature. Combustion products of the flue gas are added into the combustion area, so that the combustion temperature is reduced, and the generation of NOx is reduced; meanwhile, the added flue gas reduces the partial pressure of oxygen, which weakens the process of generating thermal NOx by oxygen and nitrogen, thereby reducing the generation of NOx. According to different application principles, the flue gas recirculation has two application modes, namely external flue gas recirculation and internal flue gas recirculation.

Typically, the flame after ignition generally acts as an igniter itself to ignite the incoming flow. This requires a high enough flame temperature to achieve minimum ignition energy, but high flame temperatures can result in increased NOx production.

Although the above technology reduces the generation of NOx to some extent, as the national importance of energy saving and emission reduction increases, a new challenge is provided to how to further reduce the generation of NOx in the combustor.

The applicant believes that the mechanism of formation of NOx for the combustion of fuel gases is primarily of the thermodynamic type, i.e. when the flame temperature is high enough, the covalent bonds of N2 are broken to give free N ions, which combine with oxygen atoms to form NOx. The production of NOx can be reduced by lowering the combustion temperature of the flame.

Therefore, the applicant provides a novel technical route, and a sectional combustion mode is adopted, wherein the upstream is lean premixed combustion, and the downstream is inert flue gas to participate in combustion, so that the combustion temperature can be greatly reduced, and the generation of NOx is inhibited.

Disclosure of Invention

The purpose of the invention is: the ultra-low nitrogen combustor and the combustion method thereof are used for solving the problems of further reducing NOx generated in the operation process of the boiler and avoiding air pollution emission in the prior art.

In order to achieve the technical purpose, the technical scheme adopted by the invention is as follows:

an ultra-low nitrogen burner applied to an auxiliary combustion chamber comprises a combustion head:

the combustion head is fixedly connected with the auxiliary combustion chamber and comprises an outer cylinder, an air inlet cylinder and a combustion cylinder; one end of the outer cylinder is fixedly connected with the air inlet cylinder, and the other end of the outer cylinder is fixedly connected with the combustion cylinder; a main combustion chamber is formed between the inner walls of the combustion cylinders; an inner cylinder is coaxially arranged in the outer cylinder, and two ends of the inner cylinder are open; an air supply channel is formed between the inner cylinder and the outer cylinder; a central gas system is arranged in the inner cylinder and comprises a central gas pipe and a central gas nozzle; a central air duct is formed between the central gas pipe and the inner cylinder;

the outer barrel is provided with a main gas system, the main gas system comprises a main gas collecting bag, a plurality of main gas branch pipes and a plurality of main gas nozzles, and the main gas collecting bag is fixedly connected with the outer barrel; the main gas nozzles are arranged in an air supply channel;

an auxiliary gas system is arranged on the outer barrel and comprises an auxiliary gas collecting bag, a plurality of auxiliary gas branch pipes and a plurality of auxiliary gas nozzles, and the auxiliary gas collecting bag is fixedly connected with the outer side of the outer barrel; the plurality of auxiliary gas nozzles are arranged between the combustion cylinder and the auxiliary combustion chamber.

Further, a rotational flow disk is sleeved outside the central gas nozzle; and a plurality of holes are uniformly distributed in the circumferential direction of the central gas nozzle.

Further, be provided with the spinning disk in the air feed passageway, the spinning disk is located between main gas nozzle and the combustion cylinder.

Furthermore, the combustion cylinder is a contraction opening, and the aperture of one end, close to the outer cylinder, of the combustion cylinder is larger than the aperture of one end, far away from the outer cylinder, of the combustion cylinder.

The air inlet cylinder is a contraction opening, and the aperture of one end, close to the outer cylinder, of the air inlet cylinder is smaller than the aperture of one end, far away from the outer cylinder, of the air inlet cylinder.

Further, a sealing sleeve is arranged at the bottom of the combustion cylinder; the seal sleeve is tightly attached to the auxiliary combustion chamber.

Further, the main gas nozzle and the auxiliary gas nozzle are four.

Furthermore, the main gas nozzle and the auxiliary gas nozzle are arranged in parallel with the outer cylinder and the inner cylinder, and the spraying directions of the main gas nozzle and the auxiliary gas nozzle are vertical to the plane of the bottom of the combustion cylinder.

The invention also provides a combustion method of the ultra-low nitrogen combustor, which comprises the following steps:

step A, supplying combustion-supporting air: supplying combustion-supporting air into the air supply channel, wherein most of the combustion-supporting air enters the air supply channel, and a small part of the combustion-supporting air enters the central air duct;

step B, injecting fuel gas: injecting fuel gas to the air supply channel through a plurality of main fuel gas nozzles of the main fuel gas system;

c, mixing combustion-supporting air and fuel gas: combustion-supporting air and fuel gas are mixed in the air supply channel, and the excess air coefficient alpha is more than 1.2;

d, premixing and burning: the premixed combustion is completed in the main combustion chamber, and because the air is relatively excessive, the premixed combustion is lean, the combustion temperature is low, the combustion process is short, and the generation of NOX is favorably inhibited;

step E, central flame stabilization: a small part of combustion-supporting air enters the central air duct, and forms rotating flame with gas sprayed by a central gas spray head of a central gas system at an outlet of the central air duct after the rotational flow of the rotational flow disc, so that a fire source is provided for stable combustion of lean premixed gas in the main combustion chamber.

Step F, supplementary combustion: and the gas is injected into the auxiliary combustion chamber through a plurality of auxiliary gas nozzles of the auxiliary gas system, and is subjected to supplementary combustion with the smoke flowing out of the main combustion chamber in the auxiliary combustion chamber, so that the combustion temperature is low, the combustion process is short, and the generation of NOX is favorably inhibited.

Furthermore, the distributed air quantity of the supplied combustion-supporting air in the air supply channel accounts for more than 90 percent of the total air quantity, and the air quantity accounts for less than 10 percent of the central air channel;

the gas supply amount of the main gas system is less than 70 percent of the total gas supply amount, and the excess air coefficient alpha is more than 1.4.

Further, the gas quantity supplied by the main gas system accounts for less than 60 percent of the total gas supply quantity, and the excess air coefficient alpha is more than 1.6.

The invention adopting the technical scheme has the following advantages:

1. compared with a combustor adopting a diffusion combustion technology, the combustor reduces the combustion temperature and inhibits the generation of NOx.

2. Compared with a combustor which purely adopts a premixed combustion technology, the total excess air coefficient is low, and the heat exchange efficiency can be greatly improved.

3. The central air duct is an interlayer channel, air and gas are premixed in the interlayer channel, the tempering risk can be greatly reduced due to the self-extinguishing effect of the slit, and the tempering risk is further reduced due to the fact that the air and gas proportion approaches to the lean-burn limit.

Drawings

The invention is further illustrated by the non-limiting examples given in the accompanying drawings;

FIG. 1 is a cross-sectional view of an ultra-low nitrogen burner of the present invention;

FIG. 2 is a schematic flow field diagram of an ultra low nitrogen burner of the present invention;

FIG. 3 is a partial block diagram of an ultra low nitrogen burner of the present invention;

fig. 4 is a perspective view of an ultra-low nitrogen burner of the present invention.

The main element symbols are as follows:

a burner head 100; an air supply passage 110; a spinning disk 111; an outer tub 112; an inner cylinder 113; an air inlet drum 114; the combustion can 115; a sealing sleeve 116; a main gas system 120; a main gas collection bag 121; main gas branch 122; a main gas nozzle 123; a central gas system 130; a central gas tube 131; a central gas burner 132; a spinning disk 133; a secondary gas system 140; an auxiliary gas collection bag 141; an auxiliary gas branch pipe 142; a secondary gas nozzle 143; a main combustion chamber 200; the secondary combustor 300.

Detailed Description

The present invention will be described in detail with reference to the drawings and specific embodiments, wherein like reference numerals are used for similar or identical parts in the drawings or the description, and implementations not shown or described in the drawings are known to those of ordinary skill in the art. In addition, directional terms, such as "upper", "lower", "top", "bottom", "left", "right", "front", "rear", and the like, used in the embodiments are only directions referring to the drawings, and are not intended to limit the scope of the present invention.

As shown in fig. 1 to 4, an ultra-low nitrogen burner, applied to a secondary combustor 300, includes a burner head 100:

the combustion head 100 is fixedly connected with the auxiliary combustion chamber 300, and the combustion head 100 comprises an outer cylinder 112, an air inlet cylinder 114 and a combustion cylinder 115; one end of the outer cylinder 112, which is far away from the auxiliary combustion chamber 300, is fixedly connected with the air inlet cylinder 114, and the other end of the outer cylinder 112 is fixedly connected with the combustion cylinder 115; a main combustion chamber 200 is formed between the inner walls of the combustion cylinders 115; an inner cylinder 113 is coaxially arranged in the outer cylinder 112, and two ends of the inner cylinder 113 are open; an air supply channel 110 is formed between the inner cylinder 113 and the outer cylinder 112; a large amount of combustion-supporting air and a small amount of fuel gas are premixed in the air supply channel 110;

a central gas system 130 is arranged in the inner barrel 113, the central gas system 130 comprises a central gas pipe 131 and a central gas spray head 132, and the central gas spray head 132 is arranged at one end of the central gas pipe 131 close to the combustion barrel 115; the central gas pipe 131 and the inner cylinder 113 are coaxially arranged; a central air duct is formed between the central gas pipe 131 and the inner cylinder 113; a small part of combustion-supporting air passes through the central air duct and is combusted with the fuel gas jetted by the central fuel gas nozzle 132;

a main gas system 120 is arranged at a position, close to the air inlet drum 114, of the outer drum 112, the main gas system 120 comprises a main gas collecting bag 121, a plurality of main gas branch pipes 122 and a plurality of main gas nozzles 123, and the main gas collecting bag 121 is fixedly connected with the outer side of the outer drum 112; the main gas nozzles 123 are arranged in the air supply channel 110, and the main gas collecting bag 121 is communicated with the nozzles through main gas branch pipes 122; the main gas system 120 injects gas into the air supply channel 110 through the main gas nozzle 123; the gas and air are mixed in the air supply channel 110;

an auxiliary gas system 140 is arranged at a position of the outer cylinder 112 close to the combustion cylinder 115, the auxiliary gas system 140 comprises an auxiliary gas collecting bag 141, a plurality of auxiliary gas branch pipes 142 and a plurality of auxiliary gas nozzles 143, and the auxiliary gas collecting bag 141 is fixedly connected with the outer side of the auxiliary gas outer cylinder 112; the plurality of auxiliary gas nozzles 143 are disposed between the combustion cylinder 115 and the auxiliary combustion chamber 300, and the auxiliary gas collecting bag 141 and the auxiliary gas nozzles 143 are communicated through the auxiliary gas branch pipes 142; the top of the secondary gas nozzle 143 is slightly lower than the top of the combustion can 115; the secondary gas system 140 injects gas into the secondary combustor 300 through the secondary gas nozzle 143 and completes combustion therein.

When the combustion-supporting air supply device is used, a large amount of combustion-supporting air enters the air supply channel 110 between the interlayers of the inner cylinder 113 and the outer cylinder 112 through the air inlet shell, a small amount of fuel gas uniformly sprays the fuel gas into the air supply channel 110 through the main fuel gas nozzle 123 in the main fuel gas system 120, the combustion-supporting air and the fuel gas are fully mixed in the air supply channel 110, and the mixed gas is premixed and combusted in the main combustion chamber 200. Because the mixed gas has the excess air coefficient alpha larger than 1.4 and the air content is relatively excessive, the combustion in the main combustion chamber 200 is lean premixed combustion to form a first combustion area, and the combustion temperature of the first combustion area is low, the combustion range is short, and the generation of NOx is favorably inhibited; in addition, a small part of combustion-supporting air passes through the central air duct, forms a rotating flame with the gas sprayed by the central gas spray head 132 of the central gas system 130 after being swirled by the swirling disc 133 at the outlet of the central air duct, and provides a fire source for stable combustion of the lean premixed gas; and forming a second combustion zone within the primary combustion chamber 200; although the combustion temperatures of the two combustion areas are lower, the combustion temperatures are different, and at the moment, because heat exchange is generated between the flame areas with low combustion temperature and high combustion temperature, the combustion stability is ensured, stable and efficient combustion areas are formed together, and the generation of NOx is reduced; the flue gas after burning in the main combustion chamber 200 enters the auxiliary combustion chamber 300 and burns again with the gas jetted by the auxiliary gas nozzle 143 in the auxiliary gas system 140, and because the flue gas has certain inertia to the cooling and inhibiting effect of the flame and the flue gas, the temperature of the burning flame is reduced, the formation of NOx is further reduced, and the emission of atmospheric pollution is reduced.

In some embodiments, a swirl disk 133 is sleeved outside the center gas nozzle 132; a plurality of holes are uniformly distributed in the circumferential direction of the central gas nozzle 132; a plurality of holes uniformly distributed on the circumferential direction of the central gas nozzle 132 are positioned between the cyclone disk 133 and the combustion cylinder 115; on one hand, the arrangement ensures that a small part of combustion-supporting air is more fully mixed with the fuel gas, thereby being beneficial to improving the combustion stability; on the other hand, under the swirling action of the swirling disc 133, the second combustion area and the first combustion area generate a mixing effect and a shearing effect, intense substance and heat transfer is performed, a stable and efficient combustion area is formed together, the combustion stability is improved, and the formation of NOx is further reduced.

In some embodiments, a swirl plate 111 is disposed in the air supply passage 110, and the swirl plate 111 is located between the main gas nozzle 123 and the burner barrel 115; the mixing of gas and combustion-supporting wind is strengthened to the setting like this for mix more abundant even.

In some embodiments, the combustion cylinder 115 is a converging port, and the diameter of the combustion cylinder 115 at the end close to the outer cylinder 112 is larger than the diameter of the combustion cylinder 115 at the end far from the outer cylinder 112.

The air inlet drum 114 is a contraction opening, and the aperture of the end of the air inlet drum 114 close to the outer drum 112 is smaller than the aperture of the end of the air inlet drum 114 far away from the outer drum 112.

The contraction of the contraction port leads to the reduction of the flow area, the flow rate of peripheral combustion-supporting air is increased, and a negative pressure injection effect is formed, so that mixed gas in the air supply channel 110 can automatically flow into the main combustion chamber 200, in addition, smoke generated after lean premixed combustion in the main combustion chamber 200 also can automatically flow into the auxiliary combustion chamber 300, and a small amount of gas ejected by the auxiliary gas system 140 in the auxiliary combustion chamber 300 is combusted again.

In some embodiments, the bottom of the combustion cylinder 115 is provided with a sealing sleeve 116; the sealing sleeve 116 is tightly attached to the auxiliary combustion chamber 300; and a seal between the combustion cylinder 115 and the auxiliary combustion chamber 300 is formed, so that combustion-supporting air, gas and combusted smoke are prevented from flowing out from a gap between the combustion cylinder 115 and the auxiliary combustion chamber 300, and the atmosphere is prevented from being polluted.

In some embodiments, the number of the main gas nozzles 123 and the number of the auxiliary gas nozzles 143 are four, and the four main gas nozzles 123 and the four auxiliary gas nozzles 143 are uniformly distributed in the air supply channel 110, the main gas nozzles 123 and the auxiliary gas nozzles 143 are both arranged in parallel with the outer cylinder 112 and the inner cylinder 113, and the injection directions of the main gas nozzles 123 and the auxiliary gas nozzles 143 are perpendicular to the plane where the bottom of the combustion cylinder 115 is located. The combustion-supporting air and gas, and the flue gas and gas are mixed more sufficiently and uniformly by the arrangement, so that the combustion is more stable, and the formation of NOx is further reduced.

In some embodiments, the aperture of the main gas nozzle 123 is larger than that of the auxiliary gas nozzle 143, and the burner can adjust the gas quantity ratio supplied by the main gas system 120 and the auxiliary gas system 140 by adjusting the ratio of the aperture of the main gas nozzle 123 to the aperture of the auxiliary gas nozzle 143; on the other hand, the gas flow rate in the main gas system 120 and the auxiliary gas system 140 can be adjusted to control the gas quantity ratio supplied by the main gas system 120 and the auxiliary gas system 140; finally, the lean premixed combustion is completed in the main combustion chamber 200, and the supplementary combustion is completed in the auxiliary combustion chamber 300.

A small part of gas is injected into the auxiliary combustion chamber 300 from the four auxiliary gas nozzles 143 of the auxiliary gas system 140, and is subjected to supplementary combustion with the residual oxygen in the flue gas after the lean premixed combustion, and because the inert flue gas participates in the combustion and the flue gas has the cooling and inhibiting effects on the flame, the combustion flame temperature is reduced, the combustion temperature is low, the generation of NOX is favorably inhibited, the treatment capacity of a factory on the NOX is reduced, and the environment is protected at the same time.

The invention also provides a combustion method of the ultra-low nitrogen combustor, which comprises the following specific steps:

step A, supplying combustion-supporting air: supplying combustion-supporting air into the air supply channel 110, wherein most of the combustion-supporting air enters the air supply channel 110, and a small part of the combustion-supporting air enters the central air channel;

step B, injecting fuel gas: injecting gas into the air supply passage 110 through a plurality of main gas nozzles 123 of the main gas system 120;

c, mixing combustion-supporting air and fuel gas: combustion-supporting air and fuel gas are mixed in the air supply channel 110, and the excess air coefficient alpha is more than 1.2;

d, premixing and burning: the premixed combustion is completed in the main combustion chamber 200, and because the air is relatively excessive, the premixed combustion is lean, the combustion temperature is low, the combustion process is short, and the generation of NOX is favorably inhibited;

step E, central flame stabilization: a small part of the combustion-supporting air enters the central air duct, and forms rotating flame with the gas sprayed by the central gas nozzle 132 of the central gas system 130 at the outlet of the central air duct after the swirling flow of the swirling disc 133, so as to provide a fire source for the stable combustion of the lean premixed gas in the main combustion chamber 200.

Step F, supplementary combustion: the gas is injected into the auxiliary combustion chamber 300 through the plurality of auxiliary gas nozzles 143 of the auxiliary gas system 140, and the gas is complementarily combusted with the flue gas flowing out from the main combustion chamber 200 in the auxiliary combustion chamber 300, so that the combustion temperature is low, the combustion process is short, and the suppression of the generation of NOX is facilitated.

In some embodiments, the air distribution ratio of the supplied combustion air in the air supply channel 110 is more than 90% of the total air quantity, and the air distribution ratio in the central air channel is less than 10%;

the gas quantity supplied by the main gas system 120 accounts for less than 70% of the total gas supply quantity, and the excess air coefficient alpha is more than 1.4.

In some embodiments, the main gas system 120 supplies gas in an amount less than 60% of the total gas supply, and the excess air factor α is greater than 1.6.

The ultra-low nitrogen burner and the combustion method thereof provided by the invention are described in detail above. The description of the specific embodiments is only intended to facilitate an understanding of the method of the invention and its core ideas. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

Claims (10)

1. An ultra-low nitrogen burner applied to an auxiliary combustion chamber (300) comprises a combustion head (100), and is characterized in that:

the combustion head (100) is fixedly connected with the auxiliary combustion chamber (300), and the combustion head (100) comprises an outer cylinder (112), an air inlet cylinder (114) and a combustion cylinder (115); one end of the outer cylinder (112) is fixedly connected with the air inlet cylinder (114), and the other end of the outer cylinder (112) is fixedly connected with the combustion cylinder (115); a main combustion chamber (200) is formed between the inner walls of the combustion cylinders (115); an inner cylinder (113) is coaxially arranged in the outer cylinder (112), and two ends of the inner cylinder (113) are open; an air supply channel (110) is formed between the inner cylinder (113) and the outer cylinder (112); a central gas system (130) is arranged in the inner barrel (113), and the central gas system (130) comprises a central gas pipe (131) and a central gas spray head (132); a central air duct is formed between the central gas pipe (131) and the inner cylinder (113);

the outer cylinder (112) is provided with a main gas system (120), the main gas system (120) comprises a main gas collecting bag (121), a plurality of main gas branch pipes (122) and a plurality of main gas nozzles (123), and the main gas collecting bag (121) is fixedly connected with the outer cylinder (112); the plurality of main gas nozzles (123) are arranged in an air supply channel (110);

an auxiliary gas system (140) is arranged on the outer cylinder (112), the auxiliary gas system (140) comprises an auxiliary gas collecting bag (141), a plurality of auxiliary gas branch pipes (142) and a plurality of auxiliary gas nozzles (143), and the auxiliary gas collecting bag (141) is fixedly connected with the outer side of the outer cylinder (112); the plurality of secondary gas nozzles (143) are disposed between the combustion can (115) and the secondary combustion chamber (300).

2. The ultra-low nitrogen burner of claim 1, wherein:

a swirl disc (133) is sleeved outside the central gas nozzle (132); and a plurality of holes are uniformly distributed on the periphery of the central gas spray head (132).

3. The ultra-low nitrogen burner of claim 1, wherein:

be provided with spinning disk (111) in air feed passageway (110), spinning disk (111) are located between main gas nozzle (123) and combustion tube (115).

4. An ultra-low nitrogen burner as set forth in claim 2, wherein:

the combustion cylinder (115) is a contraction opening, and the aperture of one end, close to the outer cylinder (112), of the combustion cylinder (115) is larger than that of one end, far away from the outer cylinder (112), of the combustion cylinder (115).

The air inlet cylinder (114) is a contraction opening, and the aperture of one end, close to the outer cylinder (112), of the air inlet cylinder (114) is smaller than the aperture of one end, far away from the outer cylinder (112), of the air inlet cylinder (114).

5. The ultra-low nitrogen burner of claim 4, wherein:

a sealing sleeve (116) is arranged at the bottom of the combustion cylinder (115); the sealing sleeve (116) is tightly attached to the auxiliary combustion chamber (300).

6. An ultra-low nitrogen burner as set forth in claim 5, wherein:

the main gas nozzle (123) and the auxiliary gas nozzle (143) are four.

7. The ultra-low nitrogen burner of claim 6, wherein:

the main gas nozzle (123) and the auxiliary gas nozzle (143) are arranged in parallel with the outer cylinder (112) and the inner cylinder (113), and the spraying directions of the main gas nozzle (123) and the auxiliary gas nozzle (143) are vertical to the plane of the bottom of the combustion cylinder (115).

8. The combustion method of an ultra-low nitrogen burner as set forth in claims 1 to 7, characterized by comprising the steps of:

step A, supplying combustion-supporting air: supplying combustion-supporting air into the air supply channel (110), wherein most of the combustion-supporting air enters the air supply channel (110), and a small part of the combustion-supporting air enters the central air channel;

step B, injecting fuel gas: injecting gas into the air supply channel (110) through a plurality of primary gas nozzles (123) of the primary gas system (120);

c, mixing combustion-supporting air and fuel gas: combustion-supporting air and fuel gas are mixed in the air supply channel (110), and the excess air coefficient alpha is more than 1.2;

d, premixing and burning: the premixed combustion is completed in the main combustion chamber (200), and because the air is relatively excessive, the premixed combustion is lean, the combustion temperature is low, the combustion range is short, and the generation of NOX is favorably inhibited;

step E, central flame stabilization: a small part of combustion-supporting air enters the central air duct, forms rotating flame with gas sprayed by a central gas spray head (132) of the central gas system (130) at the outlet of the central air duct after being swirled by the swirling disc (133), and provides a fire source for stable combustion of lean premixed gas in the main combustion chamber (200).

Step F, supplementary combustion: the auxiliary combustion chamber (300) is injected with gas through a plurality of auxiliary gas nozzles (143) of the auxiliary gas system (140), the gas and the flue gas flowing out from the main combustion chamber (200) are subjected to supplementary combustion in the auxiliary combustion chamber (300), the combustion temperature is low, the combustion process is short, and the generation of NOX is favorably inhibited.

9. The combustion method of an ultra-low nitrogen burner as set forth in claim 8, wherein:

the distributed air quantity of the supplied combustion-supporting air in the air supply channel (110) accounts for more than 90 percent of the total air quantity, and the air quantity accounts for less than 10 percent of the central air channel;

the gas quantity supplied by the main gas system (120) accounts for less than 70 percent of the total gas supply quantity, and the excess air coefficient alpha is more than 1.4.

10. The ultra-low nitrogen combustion method as set forth in claim 8, wherein:

the gas quantity supplied by the main gas system (120) accounts for less than 60 percent of the total gas supply quantity, and the excess air coefficient alpha is more than 1.6.

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