CN206130963U - Low NOx combustor of high temperature flue gas backward flow pre -burning formula with SOFA - Google Patents

Abstract

The utility model discloses a high-temperature flue gas return pre-combustion type low NOx burner equipped with SOFA, which comprises a pre-combustion chamber, a central core tube is arranged on the entrance side of the pre-combustion chamber, and an external secondary air is arranged on the pre-combustion chamber. and SOFA air sleeve, there are several outer secondary air nozzles on the side wall of the pre-combustion chamber, and several SOFA air direct-flow nozzles are arranged on the outside of the pre-combustion chamber shell; The secondary air passages are connected, and the outlet is connected with the pre-combustion chamber. The utility model adopts the low-temperature pre-combustion technology of pulverized coal, and carries the pulverized coal into the pre-combustion chamber through the primary wind, and performs pre-combustion in the reducing atmosphere of the pre-combustion chamber. The internal secondary air is divided into two streams through the flap valve, mainly for disturbance and mixing. It can also form different internal secondary air by adjusting the opening degree of the swirling internal secondary air regulating valve and the direct current internal secondary air regulating valve. swirl strength. The utility model can effectively reduce the emission of NOx, and at the same time has good flame stability, and contributes to reducing the emission of NOx pollutants in thermal power enterprises.

Description

High temperature flue gas recirculation pre-combustion low NOx burner equipped with SOFA

【Technical field】

The utility model belongs to the technical field of thermal energy and power engineering, and relates to a high-temperature flue gas recirculation pre-combustion type low NOx burner equipped with SOFA.

【Background technique】

NO _x is one of the main culprits causing large-scale smog in recent years. In addition, NO _x can also induce a series of environmental problems such as photochemical smog and acid rain. Coal-fired boilers are also one of the main sources of NO _x emissions in China. After years of Great efforts have been made in dust and SOx pollution control, but _NOx emission control is still relatively backward. According to the latest data from the Ministry of Environmental Protection, the total national nitrogen oxide emissions in 2012 were 23.378 million tons, and thermal power emissions accounted for about 35% to 40%, posing a serious threat to our environment. Therefore, the country has formulated more and more stringent measures to control the emission of _NOx . The latest "Emission Standard of Air Pollutants for Thermal Power Plants GB13223-2011" NO _x emission standard is stricter than that of Europe and the United States, and the NO _x emission of coal-fired boilers should be less than 100mg/m ³ .

At present, the control methods of nitrogen oxides mainly include flue gas denitrification and combustion denitrification. The commonly used flue gas denitrification methods mainly include selective catalytic reduction and selective non-catalytic reduction. Combustion denitrification technologies include low NOx burners, air staged combustion, and flue gas recirculation. Pulverized coal combustion device is the main equipment of thermal power production, therefore, how to improve the stability of pulverized coal combustion while reducing NOx emissions is the focus of research on pulverized coal combustion device. The pulverized coal low-temperature pre-combustion technology is a low-NOx combustion technology developed in recent years. Before the pulverized coal enters the burner, it first flows into a pre-combustion chamber with a reducing atmosphere. Due to the high temperature in the pre-combustion chamber, the pulverized coal carried in the primary air is directly burned in the pre-combustion chamber, and the nitrogen organic compounds in the fuel are first pyrolyzed into intermediate products such as hydrogen cyanide (HCN), ammonia (NH ₃ ) and CN. . Since the oxygen content in the air in the pre-combustion chamber is very limited, oxygen preferentially reacts with intermediate products (HCN, NH ₃ and CN) to generate H ₂ O, N ₂ and CO ₂ , reducing the oxygen concentration of the combustion air and reducing the formation of nitrogen oxides. In addition, the graded air distribution arrangement technology makes the oxygen ratio in the mixed gas entering the furnace small, ensures that the pulverized coal is burned in a low-oxygen environment, and reduces the flame temperature, which can not only reduce the generation of fuel-type NOx but also reduce the generation of thermal-type NOx. A reducing atmosphere is locally formed to effectively reduce NOx emissions. The rotating jet of the secondary air of the burner has a great effect on the disturbance of the air flow and the mixing of coal powder, which can stabilize the combustion, and the recirculation zone formed by the revolving jet, on the one hand, returns the high-temperature flue gas from the recirculation zone; on the other hand, the revolving jet also flows from the jet flow The outer boundary entrains the surrounding high-temperature flue gas, thereby improving the ignition and combustion stability of the pulverized coal, entraining a large amount of flue gas through the high-speed jet, making the pulverized coal burn in a low-oxygen environment, reducing the peak temperature of the flame, and reducing the generation of thermal NOx . The thick-lean separation of primary air pulverized coal and the flame-stabilizing teeth also help to reduce the amount of NOx generated and improve combustion stability.

SOFA air is the abbreviation of Separated Over Fire Air (Separated Over Fire Air), which is the overfire air in the furnace that is a certain distance away from the main combustion zone. Because in order to reduce the formation of NOx, the main combustion zone is generally burned in a micro-anoxic environment (that is, a reducing atmosphere), and the excess air coefficient is less than 1, so the combustibles (C, CO, etc.) cannot be completely burned. Therefore, it is necessary to configure SOFA air in the furnace at a certain distance from the main combustion area, so that the combustibles will be further burned in the later stage, and because the distance is far away, when the unburned flue gas reaches here, the temperature will be reduced and it will be suppressed. NOx formation. The utility model introduces the SOFA air into the low NOx burner, so that the burner can reduce the NOx emission and stabilize the combustion through the graded air distribution, rotating jet and coal powder pre-combustion, and at the same time, the combustibles can be further burned up in the later stage. Reduce fly ash and further reduce NOx.

【Content of utility model】

The purpose of the utility model is to overcome the above-mentioned shortcomings of the prior art, and provide a high-temperature flue gas recirculation pre-combustion type low NOx burner equipped with SOFA.

In order to achieve the above object, the utility model adopts the following technical solutions to achieve:

High-temperature flue gas recirculation pre-combustion low NOx burner equipped with SOFA, including a pre-combustion chamber, a central core tube is set on the inlet side of the pre-combustion chamber, and a primary air sleeve is set outside the central core tube, and a direct-flow internal secondary The air sleeve and the secondary air sleeve in the swirling flow; the oil gun and the high-energy ignition device extend from the end of the core tube, and extend from the front end into the pre-combustion chamber; the pre-combustion chamber is equipped with external secondary air and SOFA The air sleeve, the side wall of the pre-combustion chamber is provided with a number of external secondary air nozzles, and the outer side of the pre-combustion chamber is provided with a number of SOFA air direct-flow nozzles; the inlet of the primary air sleeve is connected with the primary air inlet; The inlet of the air sleeve is connected with the secondary air channel in the direct flow, and the outlet is connected with the pre-combustion chamber; the inlet of the secondary air sleeve in the swirl flow is connected with the secondary air channel in the swirl flow, and the outlet is connected with the pre-combustion chamber Pass.

The further improvement of the utility model is:

The ends of the oil gun and the high-energy ignition device are connected to a combined pneumatic propeller. When ignition is required, the combined pneumatic propeller sends the oil gun and the high-energy ignition device to the ignition position. After the ignition is completed, the oil gun and the high-energy ignition The device retracts back into the mandrel.

The end of the core tube is provided with a first fire sighting device, and the rear end side wall of the pre-combustion chamber is provided with an infrared flame detection device and a second fire sighting device.

The outlet of the primary air sleeve is provided with a pulverized coal concentration ring and flame stabilizing teeth for improving the stability of pulverized coal combustion.

The inlets of the secondary air channel in the direct current and the secondary air channel in the swirling flow are provided with flap valves for adjusting the air intake ratio of the secondary air in the direct current and the secondary air in the swirling flow; the secondary air channel in the swirling flow Tangential swirl blades are set at the outlet of the outlet.

The flap valve is provided with a secondary air regulating valve in the direct current and a secondary air regulating valve in the swirling flow. By adjusting the openings of the secondary air regulating valve in the direct current and the secondary air regulating valve in the swirling flow, the The proportion of secondary air and secondary air in the swirl.

The outlet of the direct-flow internal secondary air sleeve expands outward at an angle α, 20°≤α≤30°.

The angle between the inner wall on the inlet side of the pre-chamber and the horizontal direction is β, 25°≤β≤35°.

The axial positioning angle of the external secondary air nozzle is γ, 25°≤γ≤35°, and the circumferential positioning angle is θ, 25°≤θ≤35°, so that the ejected external secondary air surrounds the pre-combustion chamber The outlet axis forms the secondary air outside the swirling flow.

18 SOFA air direct-flow nozzles are arranged on the outside of the pre-chamber housing.

Compared with the prior art, the utility model has the following beneficial effects:

The utility model adopts the low-temperature pre-combustion technology of pulverized coal, and carries the pulverized coal into the pre-combustion chamber through the primary wind, and performs pre-combustion in the reducing atmosphere of the pre-combustion chamber. Nitrogen organic compounds in fuels are first pyrolyzed into intermediate products such as hydrogen cyanide (HCN), ammonia (NH ₃ ) and CN when heated. Since the oxygen content in the air in the pre-combustion chamber is very limited, oxygen preferentially reacts with intermediate products (HCN, NH ₃ and CN) to generate H ₂ O, N ₂ and CO ₂ , reducing the oxygen concentration of the combustion air and reducing the formation of nitrogen oxides. The pulverized coal concentration ring at the primary air outlet can realize the separation of pulverized coal concentration and light, and obtain a high-concentration pulverized coal airflow, which has good ignition and combustion stability. Increasing the concentration of pulverized coal can further reduce the amount of NOx generated. The flame stabilizing tooth at the primary air outlet can also play a role in stabilizing combustion. In terms of graded air supply, the internal secondary air is divided into two streams through the flap valve, that is, the direct current internal secondary air and the swirling internal secondary air, which supplement the air needed for the continuous combustion of pulverized coal, and mainly play the role of disturbance and mixing , and the ratio of the two internal secondary air can be controlled by adjusting the opening of the swirling internal secondary air regulating valve and the direct current internal secondary air regulating valve, thereby forming different internal secondary air swirl intensities. The external secondary air is ejected through 18 inclined swirling holes. The swirling external secondary air has a great effect on the disturbance of the airflow and the mixing of coal powder, which can stabilize combustion. The high-temperature flue gas reflows in the recirculation zone; on the other hand, the rotating jet also entrains the surrounding high-temperature flue gas from the outer boundary of the jet, thereby improving the ignition and combustion stability of pulverized coal, and the lower oxygen content of the high-temperature flue gas also helps to suppress NOx generation. The combustion device introduces SOFA air, which is sprayed from 18 SOFA air direct-flow nozzles on the edge of the pre-combustion chamber shell, so that combustibles can be further burned in the later stage, reducing fly ash and further reducing NOx. The utility model can effectively reduce the emission of NOx, and at the same time has good flame stability, and contributes to reducing the emission of NOx pollutants in thermal power enterprises.

【Description of drawings】

Fig. 1 is the overall structural representation of the utility model;

Fig. 2 is a sectional view in the direction of Fig. 1A-A;

Fig. 3 is the right view of Fig. 1;

FIG. 4 is a top view of FIG. 1 .

Marks in the picture: 1-high-energy ignition device, 2-oil gun, 3-combined pneumatic propeller, 4-first fire sighting device, 5-center core tube, 6-primary air sleeve, 7-direct current secondary Air channel, 8-swirl inner secondary air channel, 9-flap flap valve, 10-infrared flame monitoring device, 11-second fire viewing device, 12-external secondary air and SOFA air inlet, 13-pre-combustion chamber Shell, 14-pre-combustion chamber, 15-external secondary air nozzle, 16-SOFA air direct current nozzle, 17-stabilizing flame teeth, 18-direct current internal secondary air flare, 19-coal powder concentration ring, 20-direct current Inner secondary air sleeve, 21-swirl inner secondary air sleeve, 22-tangential swirl blade, 23-primary air inlet, 24-swirl inner secondary air regulating valve, 25-DC inner secondary air regulator valve.

【detailed description】

Below in conjunction with accompanying drawing, the utility model is described in further detail:

Referring to Fig. 1-Fig. 4, the utility model is composed of an ignition system (high-energy ignition device 1, oil gun 2, combined pneumatic propeller 3), core tube 5, primary air sleeve 6, flame stabilizing teeth 17, coal powder concentration Ring 19, DC internal secondary air channel 7, swirl internal secondary air channel 8, DC internal secondary air sleeve 20, swirl internal secondary air sleeve 21, flap valve 9, infrared flame monitoring device 10, It consists of a fire-watching device, a pre-chamber casing, a pre-chamber 14, an external secondary air nozzle 15, a SOFA air direct-flow nozzle 16, and the like.

The utility model comprises a pre-combustion chamber 14, a central core tube 5 is arranged on one side of the entrance of the pre-combustion chamber 14, and a primary air sleeve 6, a direct current internal secondary air sleeve 20 and a swirl internal The secondary air sleeve 21; the oil gun 2 and the high-energy ignition device 1 extend from the end of the core tube 5, and extend from the front end into the pre-combustion chamber 14; the pre-combustion chamber 14 is provided with external secondary air and SOFA The air sleeve, the side wall of the pre-combustion chamber 14 is provided with a number of external secondary air nozzles 15, and the outer side of the pre-combustion chamber 14 shell is provided with a number of SOFA air direct current nozzles 16; the inlet of the primary air sleeve 6 is connected with the primary air inlet 23 The inlet of the secondary air sleeve 20 in the DC is connected with the secondary air channel 7 in the DC, and the outlet is connected with the pre-combustion chamber 14; the inlet of the secondary air sleeve 21 in the swirl is connected with the secondary air in the swirl The channels 8 communicate with each other, and the outlet communicates with the pre-chamber 14 .

The ends of the oil gun 2 and the high-energy ignition device 1 are connected to the combined pneumatic propeller 3. When ignition is required, the combined pneumatic propeller 3 sends the oil gun 2 and the high-energy ignition device 1 to the ignition position. The gun 2 and the high energy ignition device 1 are retracted into the core tube 5 . The end of the core tube 5 is provided with a first fire sighting device 4 , and an infrared flame detection device 10 and a second fire sighting device 11 are arranged on the side wall of the rear end of the pre-combustion chamber 14 .

The outlet of the primary air sleeve 6 is provided with a pulverized coal concentration ring 19 and flame stabilizing teeth 17 for improving the stability of pulverized coal combustion. The inlets of the secondary air channel 7 in the direct current and the secondary air channel 8 in the swirling flow are provided with a flap valve 9 for adjusting the air intake ratio of the secondary air in the direct current and the secondary air in the swirling flow; A tangential swirl vane 22 is arranged at the outlet of the channel 8 . The flap valve 9 is provided with a direct current internal secondary air regulating valve 25 and a swirling internal secondary air regulating valve 24. By adjusting the openings of the direct current internal secondary air regulating valve 25 and the swirling internal secondary air regulating valve 24, Adjust the ratio of the secondary air in the direct flow and the secondary air in the swirling flow.

The outlet of the DC inner secondary air sleeve 20 expands outwards at an angle α, 20°≤α≤30°. The angle between the inner wall on the inlet side of the pre-chamber and the horizontal direction is β, 25°≤β≤35°. The axial positioning angle of the external secondary air nozzle 15 is γ, 25°≤γ≤35°, and the circumferential positioning angle is θ, 25°≤θ≤35°, so that the ejected external secondary air gathers in the pre-combustion chamber 14 near the exit axis. 18 SOFA air direct-flow nozzles 16 are arranged on the outer side of the pre-combustion chamber 14 housing.

Principle of the utility model:

The utility model uses the high-temperature flue gas swept into the pre-combustion chamber by the recirculation area formed by the secondary air outside the swirling flow to preheat the coal powder in the pre-combustion chamber. On the one hand, it is beneficial to stable combustion; Indoor partial combustion and pyrolysis, nitrogen organic compounds in the fuel are first pyrolyzed into intermediate products such as hydrogen cyanide, and react with oxygen under low oxygen conditions to generate N ₂ , effectively reducing the amount of NOx produced. The oxygen content of the high-temperature flue gas flowing back into the pre-combustion chamber is relatively low, which further reduces the oxygen content in the pre-combustion chamber and suppresses the formation of NOx.

In order to ensure the low oxygen environment in the pre-combustion chamber, it is required to:

(primary air volume (coal powder) + internal secondary air volume) / theoretically calculated total air volume required for pulverized coal combustion < 0.2

That is to say, the total excess air coefficient in the preheating chamber should be less than 0.2.

Since the air consumption coefficient in the pre-combustion chamber is less than 0.2, the oxygen in the pre-heating chamber is almost consumed by the combustion of pulverized coal. Therefore, the mixed gas that transports pulverized coal, unburned volatile matter, etc. into the furnace contains almost no oxygen, which is conducive to organizing the combustion of pulverized coal at high temperature and low oxygen in the furnace, and further reducing the emission of NOx pollutants.

In order to obtain better denitrification efficiency, in the boiler where the high-temperature flue gas return pre-combustion low NOx burner with SOFA (remote burn-out air) is applied, it is necessary to reasonably design the diameter of the external secondary air nozzle and the size of the SOFA The diameter of the direct-flow nozzle is used to adjust the ratio of the secondary air outside the swirling flow to the SOFA air, so that the air consumption coefficient of the main combustion area is <1.0, and the air consumption coefficient of the ember area is >1.0.

In order to improve the level of automation and monitor the stability of combustion, the combustion device is equipped with high-energy ignition device, oil gun and infrared flame monitoring device. In order to prolong the service life of the oil gun and high-energy ignition device, it is equipped with a combined pneumatic propeller. When ignition is required, the thruster moves forward to send the oil gun and high-energy igniter to the ignition position. But after the ignition is over, the thruster runs backwards, shrinking the oil gun and high-energy igniter back to the core tube, avoiding high-temperature erosion, corrosion and coking pollution.

In order to improve the stability of pulverized coal combustion, flame stabilizing teeth are installed at the outlet of the primary air; internal secondary air is installed around the periphery of the primary air pulverized coal flow; the internal secondary air is divided into direct current internal secondary air and cyclone through the flap valve The secondary air in the flow; the outlet of the secondary air in the direct current expands at a certain angle α, and the angle α is required to be in the range of 20 to 30 degrees.

In order to ensure the combustion effect, it is required that the radian β angle range of the pre-combustion chamber is 25-35 degrees; the positioning angle γ angle range of the secondary air nozzle outside the swirl flow is required to be within 25-35 degrees; the positioning angle of the secondary air nozzle outside the swirl flow is required The θ angle ranges from 25 to 35 degrees.

In order to improve the stability of pulverized coal combustion, a number of tangential swirl blades are set in the secondary air channel in the swirl flow. The secondary air in the swirl flow generated by the tangential swirl blades can not only strengthen disturbance and mixing, but also A recirculation zone can be formed in the pre-combustion chamber, thereby improving the stability of pulverized coal combustion; by adjusting the internal secondary air flap valve, the ratio of the secondary air in the direct current and the secondary air in the swirling flow can be adjusted, and then it can be adjusted according to the type of coal To adjust the swirl intensity of the internal secondary air and the size of the recirculation zone; set a pulverized coal concentration ring in the primary air casing. When the pulverized coal airflow collides with the enrichment ring, the pulverized coal is separated into an airflow that is dense inside and thin outside due to inertia. After the pulverized coal is sprayed into the preheating chamber, the air flow is thick in the center and light on both sides.

The external secondary air is ejected from 18 oblique swirl holes to form a return flow area. Among them, the oblique swirl hole is close to the outlet of the pre-combustion chamber, and the external secondary air ejected by it forms a swirling external secondary air around the axis of the pre-combustion chamber outlet, which can ensure that the excess air coefficient in the pre-combustion chamber does not increase, thereby ensuring the pre-combustion chamber. The low-oxygen environment of the combustion chamber further reduces the emission of NOx pollutants.

The SOFA air is ejected from 18 SOFA air direct-flow nozzles on the periphery of the pre-combustion chamber to supplement the oxygen needed in the later stage of combustion, so that the combustibles can be further burned out in the later stage, reducing fly ash, and the injection of SOFA air also reduces the combustion temperature , so further reduce NOx.

Oxygen in the preheating chamber is almost consumed by pulverized coal combustion. Therefore, the mixed gas that transports pulverized coal, soot, unburned volatile matter, etc. into the furnace contains almost no oxygen, which is conducive to organizing the combustion of pulverized coal at high temperature and low oxygen in the furnace, and further reducing the emission of NOx pollutants.

Primary air, internal secondary air, external secondary air, SOFA air, etc. adopt graded air distribution to ensure that the main combustion area in the furnace is a low-oxygen environment, so that hydrogen cyanide entering the furnace can react with oxygen under low-oxygen conditions Generate N ₂ , CO ₂ and H ₂ O to further reduce the amount of NOx produced.

Working process of the present utility model:

First, the internal secondary air is sent in through the internal secondary air inlet, and the internal secondary air enters the DC internal secondary air channel 7 and the swirling internal secondary air channel 8 respectively, and passes through the DC internal secondary air sleeve 20 respectively. And the secondary air sleeve 21 in the swirling flow enters the pre-combustion chamber 14, and the pre-combustion chamber is purged for more than 1 minute. Then the combined pneumatic propeller 3 is moved forward, and the high-energy ignition device 1 and the oil gun 2 are sent to the designated ignition position. The high-energy ignition device 1 works to ignite the fuel gun 2 . The internal secondary air is sent in through the internal secondary air inlet, and the internal secondary air enters the DC internal secondary air channel 7 and the swirling internal secondary air channel 8 respectively, and passes through the DC internal secondary air sleeve 20 and the swirling internal secondary air channel respectively. The in-flow secondary air sleeve 21 enters the pre-chamber 14 . Some tangential swirl vanes 22 provided in the secondary air passage 8 in the swirl flow can make the secondary air in the passage rotate, and the secondary air in this swirl flow can generate a recirculation zone at the front end of the pre-combustion chamber 14, thereby Helps to stabilize combustion. The mixture of pulverized coal and air is fed into the pulverized coal inlet 23 of the primary air, and the mixture flows in the annular passage between the primary air sleeve 6 and the central core pipe 5. Due to the effect of inertia, after passing through the pulverized coal concentration ring 19, it is Separation into a pulverized coal flow that is thick in the center and light in the surroundings, after it enters the pre-combustion chamber 14, a calorific value occurs and is ignited by the flame formed by the oil gun 2 . The pulverized coal concentration ring 19, the flame stabilizing teeth 17 and the secondary air flaring 18 in the direct current make the pulverized coal burn stably. By controlling the opening of the secondary air regulating valve 25 in the direct current and the secondary air regulating valve 24 in the swirling flow in the flap valve 9, the ratio of the secondary air in the direct current and the secondary air in the swirling flow can be adjusted, and then can be adjusted according to Different types of coal are used to adjust the swirling intensity of the internal secondary air and the size of the recirculation zone. When the oxygen produced by the primary air and internal secondary air is insufficient, the hydrogen cyanide produced by the pyrolysis of coal powder reacts with oxygen under low oxygen conditions to form _N2 , _CO2 and _H2O , which reduces the NOx Generation volume. The external secondary air is ejected through the inclined external secondary air nozzle 15 arranged in the second half of the pre-combustion chamber housing 13, and then replenishes the oxygen needed for continuous combustion. Since the secondary air nozzle 15 is obliquely positioned, the The external secondary air is injected by the swirling flow, and the external secondary air of the swirling flow gathers near the outlet axis of the pre-combustion chamber, which can form a recirculation zone, and then entrain the high-temperature flue gas in the furnace for stable combustion, reduce the oxygen content, and maintain the reducibility atmosphere, further reducing the amount of NOx produced. The external secondary air, entrained high-temperature flue gas, incompletely burned fuel and fly ash combustibles are evenly mixed in the second half of the pre-combustion chamber, and then sent to the furnace for combustion. The SOFA air is sprayed into the furnace by 18 SOFA air direct-flow nozzles 16 on the periphery of the pre-combustion chamber shell 13 to supplement the oxygen needed in the later stage of combustion, so that the combustibles can be further burned out in the later stage, reducing fly ash, and the SOFA air is also injected into the furnace. The combustion temperature is lowered, so the amount of NOx produced is further reduced. After the pre-combustion chamber 14 burns stably, the combined pneumatic propeller 3 acts to retract the oil gun 2 and the high-energy ignition device 1 into the core tube 5 to prolong its service life. Simultaneously, the infrared flame monitoring device 10 monitors the flame state in the combustion in real time through the second fire watching device 11. When a fire is extinguished, an alarm is issued, and the input of pulverized coal is stopped in time, and the purge and ignition operations are re-executed.

The above content is only to illustrate the technical idea of the utility model, and cannot limit the protection scope of the utility model. Any changes made on the basis of the technical solution according to the technical idea proposed by the utility model all fall into the scope of the utility model. within the scope of protection of the claims.

Claims (10)

1. The high-temperature flue gas recirculation pre-combustion type low NOx burner that is provided with SOFA is characterized in that, comprises pre-combustion chamber (14), and the entrance side of pre-combustion chamber (14) is provided with central core tube (5), central core The pipe (5) is sequentially provided with a primary air sleeve (6), a direct current internal secondary air sleeve (20) and a swirling internal secondary air sleeve (21); an oil gun (2) and a high-energy ignition device ( 1) It extends from the end of the core pipe (5), and extends from the front end into the pre-combustion chamber (14); the pre-combustion chamber (14) is provided with an external secondary air and SOFA air sleeve, and the pre-combustion chamber The side wall of (14) is provided with some outer secondary air spouts (15), and some SOFA air direct current spouts (16) are arranged on the outside of the pre-combustion chamber (14) housing; the inlet of the primary air sleeve (6) is connected with the primary air The inlet (23) is connected; the inlet of the DC internal secondary air sleeve (20) is connected with the DC internal secondary air channel (7), and the outlet is connected with the pre-combustion chamber (14); the swirl internal secondary air sleeve The inlet of the cylinder (21) communicates with the secondary air channel (8) in the swirling flow, and the outlet communicates with the pre-combustion chamber (14). 2. The high-temperature flue gas return pre-combustion low NOx burner equipped with SOFA according to claim 1, characterized in that, the end of the oil gun (2) and the high-energy ignition device (1) is connected to a combined pneumatic propulsion device (3), when ignition is required, the combined pneumatic propeller (3) sends the oil gun (2) and the high-energy ignition device (1) to the ignition position, and after the ignition is completed, the oil gun (2) and the high-energy ignition device The device (1) is retracted into the mandrel (5). 3. The high-temperature flue gas recirculation pre-combustion low NOx burner equipped with SOFA according to claim 1 or 2, characterized in that, the end of the core tube (5) is provided with a first fire sighting device (4) An infrared flame detection device (10) and a second fire sighting device (11) are arranged on the side wall of the rear end of the pre-combustion chamber (14). 4. The high-temperature flue gas return pre-combustion low NOx burner provided with SOFA according to claim 1, characterized in that, the outlet of the primary air sleeve (6) is provided for improving the stability of pulverized coal combustion Permanent pulverized coal concentration ring (19) and stable flame teeth (17). 5. The high-temperature flue gas return pre-combustion low NOx burner provided with SOFA according to claim 1, characterized in that, the secondary air passage (7) in the direct flow and the secondary air passage (8 in the swirling flow ) is provided with a flap valve (9) for adjusting the air intake ratio of the secondary air in the direct current and the secondary air in the swirl; the outlet of the secondary air channel (8) in the swirl is provided with tangential swirl blades (twenty two). 6. The high-temperature flue gas return pre-combustion low NOx burner equipped with SOFA according to claim 5, characterized in that, the flap valve (9) is provided with a secondary air regulating valve (25) in the direct current and the secondary air regulating valve (24) in the swirling flow, by adjusting the opening of the secondary air regulating valve (25) in the direct current and the secondary air regulating valve (24) in the swirling flow, adjust the secondary air and the swirling flow in the direct current The ratio of internal secondary air. 7. The high-temperature flue gas return pre-combustion low NOx burner provided with SOFA according to claim 1, characterized in that, the outlet of the direct-flow internal secondary air sleeve (20) expands outward at an angle α, 20 °≤α≤30°. 8. The high-temperature flue gas recirculation pre-combustion low NOx burner provided with SOFA according to claim 1, characterized in that the angle between the inner wall on the inlet side of the pre-combustion chamber and the horizontal direction is β, 25° ≤β≤35°. 9. The high-temperature flue gas return pre-combustion low NOx burner equipped with SOFA according to claim 1, characterized in that, the axial positioning angle of the external secondary air nozzle (15) is γ, 25°≤ γ≤35°, the circumferential positioning angle is θ, 25°≤θ≤35°, so that the ejected external secondary air forms a swirling external secondary air around the outlet axis of the pre-combustion chamber (14). 10. The high-temperature flue gas return pre-combustion type low NOx burner provided with SOFA according to claim 1, characterized in that 18 SOFA air direct-flow nozzles (16) are arranged outside the housing of the pre-combustion chamber (14) .