CN210069845U

CN210069845U - Combustor and gas system

Info

Publication number: CN210069845U
Application number: CN201920263350.5U
Authority: CN
Inventors: 吕宜德; 吕元; 吕复
Original assignee: Wuhan Aojie Technology Corp
Current assignee: Wuhan Aojie Technology Corp
Priority date: 2019-03-01
Filing date: 2019-03-01
Publication date: 2020-02-14
Anticipated expiration: 2029-03-01

Abstract

The utility model relates to a burner and a gas system, wherein the burner comprises a first combustion mechanism and a second combustion mechanism; the first gas supply pipeline of the first combustion mechanism is provided with a first gas inlet end and a first gas outlet end for supplying gas to the boiler, the first gas supply pipeline is sleeved on the first gas supply pipeline, the first ignition lance penetrates through the first gas supply pipeline and extends to the gas outlet end of the first gas supply pipeline, and the first cyclone is arranged at the first gas outlet end; the second air supply pipeline of the second combustion mechanism is sleeved on the first air supply pipeline, the second air supply pipeline is provided with a second air inlet end and a second air outlet end, the second ignition spray gun is arranged in the second air supply pipeline in a penetrating mode and extends to the air outlet end of the second air supply pipeline, and the second gas supply pipeline is arranged in the second air supply pipeline in a penetrating mode. The combustor and the gas system comprising the combustor can realize gas thin stream and cyclone combustion, multi-section combustion and thick-thin combustion on the whole, thereby inhibiting the generation of NOx.

Description

Combustor and gas system

Technical Field

The utility model relates to a combustor and gas system.

Background

Natural gas is used as a clean fossil energy, if the natural gas is roughly combusted, a large amount of nitrogen oxides (NOx) and carbon monoxide (CO) can be generated, and the aims of saving energy, reducing emission and eliminating the nitrogen oxides (NOx) and the carbon monoxide (CO) cannot be achieved.

In spite of the conventional low NOx natural gas burner at home and abroad, some insufficient or imperfect places still exist, and high-content NOx is still generated in the combustion process.

SUMMERY OF THE UTILITY MODEL

The utility model discloses to the technical problem who exists among the prior art, provide a combustor and gas system that can effectively reduce the NOx emission.

The utility model provides an above-mentioned technical problem's technical scheme as follows:

a burner comprising a first combustion means and a second combustion means;

the first combustion mechanism comprises a first gas supply pipeline, a first air supply pipeline, a first ignition spray gun and a first cyclone, the first gas supply pipeline is provided with a first gas inlet end used for connecting a gas source and a first gas outlet end used for supplying gas to the boiler, the first gas supply pipeline is sleeved on the first gas supply pipeline, the first air supply pipeline is provided with a first air inlet end and a first air outlet end covering the first gas outlet end, the first ignition spray gun is arranged in the first gas supply pipeline or the first gas supply pipeline in a penetrating manner and extends to the gas outlet end of the first gas supply pipeline for ignition, and the first cyclone is arranged at the first air outlet end for rotating combustion airflow;

the second combustion mechanism comprises a second air supply pipeline, a second gas supply pipeline, a second ignition spray gun and a second cyclone swirler, the second air supply pipeline is sleeved on the first air supply pipeline, the second air supply pipeline is provided with a second air inlet end and a second air outlet end, the second gas supply pipeline is arranged in the second air supply pipeline in a penetrating manner, the second gas supply pipeline is used for connecting a second gas inlet end of a gas source and a second gas outlet end used for supplying gas to the boiler, the second gas outlet end, the second air outlet end and the first gas outlet end are arranged on the same side, the second ignition spray gun is arranged in the second air supply pipeline or the second gas supply pipeline in a penetrating manner and extends to the gas outlet end for ignition, and the second cyclone swirler is arranged at the second air outlet end and used for rotating combustion airflow, the second cyclone is provided with a plurality of second cyclone, and the second cyclone is sequentially arranged at intervals to form an impeller ring system.

In one embodiment, the second air outlet end surrounds the first air outlet end and is matched with the first air outlet end to form a cavity communicated with the second air supply pipeline, and a partition plate is arranged in the cavity to form an internal circulation passage for circulating the combustion air flow.

In one embodiment, the burner further comprises a fire detection structure, and the fire detection structure is arranged in the first air supply pipeline in a penetrating mode and extends to the air outlet end of the first air supply pipeline.

In one embodiment, the first combustion mechanism further comprises a mixing bin for mixing air and combusted smoke, a first valve for regulating and controlling air inlet amount is arranged at an air inlet end of the mixing bin, and an air outlet end of the mixing bin is communicated with the first air supply pipeline.

In one embodiment, the second combustion mechanism further comprises an air bin and a gas bin, the gas bin and the air bin are sleeved in the first air supply pipeline in parallel, a second valve for regulating and controlling the air inlet amount is arranged at the air inlet end of the air bin, and the air bin is communicated with the second air inlet end; the air inlet end of the gas bin is provided with a third valve used for regulating and controlling the gas inlet amount, and the gas bin is communicated with the second gas inlet end.

In one embodiment, the first valve, the second valve and the third valve are all solenoid valves.

A gas system comprises a boiler, a first fan, an exhaust tower and the burner of any one of the above parts; the second air outlet end is connected with the boiler, the end parts of the first gas outlet end, the first air outlet end, the second air outlet end and the second gas outlet end extend into the boiler, an air outlet of the boiler is connected with a first fan, and the first fan is connected with the exhaust tower through an exhaust pipeline.

In one embodiment, the gas system further comprises a flue gas outer circulation pipeline and a second fan, wherein the gas inlet end of the flue gas outer circulation pipeline is connected with the exhaust pipeline, the second fan is connected in series with the flue gas outer circulation pipeline, the gas outlet end of the flue gas outer circulation pipeline is connected with the first air supply pipeline, and the flue gas outer circulation pipeline is further provided with a fourth valve.

In one embodiment, the gas system further comprises an air preheater and a third fan; the air preheater is connected in series between the first fan and the boiler, the air preheater is further connected with the first air inlet end and the second air inlet end through pipelines respectively, and the air preheater is connected with the third fan.

In one embodiment, the gas system further comprises a controller, and the controller is respectively connected with the first combustion mechanism, the second combustion mechanism, the air preheater, the first fan, the second fan and/or the third fan.

In one embodiment, the gas system further comprises an economizer connected in series between the air preheater and the boiler.

The combustor is a low NOx combustor, and the combustion principle of the combustor is as follows: nitrogen oxides (NOx) in gas combustion fumes are mainly NO, and NO₂And rarely. When the NO is introduced into the atmosphere,is oxidized to NO quickly₂. To prevent NO₂And photochemical smog pollution caused by the pollution, the generation of NO in gas combustion smoke must be inhibited. The NOx generating mechanism can be divided into a temperature type and a fuel type, and the method for reducing or controlling the NOx content in the flue gas mainly comprises three aspects of reducing the combustion temperature, diluting the oxygen concentration in a combustion area and reducing the residence time of the flue gas in a high-temperature area.

The utility model has the advantages that:

the burner can realize the combustion of gas thin stream and cyclone, multi-stage combustion and rich-lean combustion by adjusting the sizes of structures such as pipelines in the first combustion mechanism and the second combustion mechanism, can realize the combustion under the condition of excess air and the combustion under the condition of insufficient air quantity, reduces the combustion temperature, and inhibits the generation of NOx. In addition, the burner can also realize a smoke recycling method, and a part of smoke discharged from a gas combustion furnace (boiler) is mixed with the burner and then is sent into the furnace for combustion, thereby further reducing and inhibiting the generation of NOx; moreover, the combustor can also realize a staged combustion method, and multi-stage air supply is carried out according to different intervals, the coefficient of excess air is increased from small to large, and the oxygen content of the supplied air is increased from small to large, so that the aim of reducing the temperature is fulfilled, and the generation of NOx is inhibited.

Drawings

FIG. 1 is a schematic view of a burner according to an embodiment;

FIG. 2 is a schematic structural diagram of a first combustion mechanism and a flue gas external circulation passage in the combustor of FIG. 1;

FIG. 3 is a partial schematic view of a second combustion mechanism in the combustor of FIG. 1;

FIG. 4 is a schematic view of the structure of an internal circulation path in the combustor of FIG. 1;

FIG. 5 is a schematic view of another perspective in the combustor of FIG. 1;

fig. 6 is a schematic view of a gas system including the burner of fig. 1.

In the drawings, the components represented by the respective reference numerals are listed below:

100. the gas-fired boiler comprises a burner, a 111, a first gas supply pipeline, a 112, a first air supply pipeline, a 113, a first ignition spray gun, a 114, a first cyclone, a 115, a fire detection structure, a 116, a mixing bin, a 131, a flue gas internal circulation inlet, a 132, a flue gas internal circulation outlet, a 121, a second gas supply pipeline, a 1210, a gas bin, a 122, a first air supply pipeline, a 1220, an air bin, a 123, a second ignition spray gun, a 124 and a second cyclone;

200. the system comprises a boiler, 300, a first fan, 400, an exhaust tower, 500, an air preheater, 510, a third fan, 610, a flue gas external circulation pipeline, 620, a second fan, 630, a fourth valve, 700 and an economizer.

Detailed Description

The principles and features of the present invention are described below in conjunction with the following drawings, the examples given are only intended to illustrate the present invention and are not intended to limit the scope of the present invention. It will be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

Referring to fig. 1, a burner 100 of an embodiment includes a first combustion mechanism and a second combustion mechanism.

Referring to fig. 2, in the present embodiment, the first combustion mechanism includes a first gas supply duct 111, a first air supply duct 112 (primary air duct), a first ignition lance 113, and a first cyclone 114 (with a rotary impeller therein). Wherein the first gas supply pipeline 111 has a first gas inlet end for connecting a gas source and a first gas outlet end for supplying gas to the boiler. The first gas supply pipeline 111 is sleeved with the first air supply pipeline 112, and the first air supply pipeline 112 has a first air inlet end and a first air outlet end covering the first gas outlet end. The first ignition torch 113 is disposed through the first air supply duct 112 and extends to the air outlet end thereof for ignition. A first cyclone 114 is provided at the first air outlet end for swirling the combustion air flow in the central region.

Further, in this embodiment, the first combustion mechanism further comprises a mixing bin 116 for mixing air and combusted flue gas. The air inlet end of the mixing chamber 116 is provided with a first valve (not numbered in the figure) for regulating the air inlet amount, and the air outlet end of the mixing chamber 116 is communicated with the first air supply pipeline 112. The burned flue gas is mixed with the air (primary air) entering the first air supply pipeline 112 according to a certain proportion, and under the action of the first cyclone 114, a rotating airflow is generated, and low-oxygen and low-temperature rotating flame is formed with the help of an ignition gun, so that the generation of NOx can be greatly inhibited.

In addition, the burner of the present embodiment further includes a fire detection structure 115. The fire detection structure 115 is disposed through the first air supply duct 112 and extends to the air outlet end thereof.

Referring further to fig. 3, the second combustion mechanism includes a second fuel supply gas duct 121, a second air supply duct 122, a second ignition lance 123 and a second cyclone 124. The second air supply pipe 122 is sleeved on the first air supply pipe 112, and the second air supply pipe 122 has a second air inlet end and a second air outlet end. The second gas supply pipeline 121 is disposed through the second air supply pipeline 122, and the second gas supply pipeline 121 is used for connecting a second gas inlet end of the gas source and a second gas outlet end for supplying gas to the boiler. The second gas outlet end, the second air outlet end and the first gas outlet end are arranged on the same side. The second ignition lance 123 is disposed through the second gas supply pipeline 121 and extends to the gas outlet end thereof for ignition. A second cyclone 124 is provided at the second air outlet end for swirling the combustion air flow. Preferably, there are a plurality of second cyclone cyclones 124, and a plurality of second cyclone 124 are arranged at intervals in sequence to form an impeller ring system, so as to form a ring of small rotating flames, reduce the temperature of the combustion flame flow, and inhibit the generation of NOx.

The burner 100 of the present embodiment supplies fuel and air in a plurality of times, respectively, and can adjust the gas supply amounts in the first gas supply duct 111 and the second gas supply duct 121 and the air supply amounts in the first air supply duct 112 and the second air supply duct 122 according to circumstances, and can adjust and realize the gas thin stream and the cyclone combustion, the multi-stage combustion, and the rich-lean combustion as a whole by providing the impeller ring system formed by the first cyclone 114 and the second cyclone 124 that divides the flame stream, and can realize the combustion in the excess air and the combustion in the insufficient air amount, and can reduce the combustion temperature, thereby suppressing the generation of NOx.

Further, in this embodiment, the second air outlet end surrounds the first air outlet end and cooperates with the first air outlet end to form a cavity communicated with the air chamber 1220 or the second air supply pipeline 122, a partition is disposed in the cavity to form the internal flue gas circulation inlet 131 and the internal flue gas circulation outlet 132, so as to form an internal circulation passage for circulating the combustion air flow, absorb the unburnt fuel gas to enter the negative pressure region, so as to achieve uninterrupted combustion, and enable the unburnt fuel gas and the flue gas around to enter the internal circulation flue gas system under the action of the negative pressure and the cyclone air flow, thereby further reducing the temperature in the combustion region, shortening the residence time of the flue gas in the high temperature region, reducing the oxygen content in the region, and reducing or eliminating the generation of NOx.

Further, in the present embodiment, the second combustion mechanism further includes a gas silo 1210 and an air silo 1220. The gas cabin 1210 and the air cabin 1220 are sleeved in parallel on the first air supply pipeline 112. The air inlet end of the air chamber 1220 is provided with a second valve (not numbered) for controlling the amount of air introduced. The air reservoir 1220 communicates with the second air intake port. The air chamber 1220 is also in communication with the internal circulation passage to facilitate the internal circulation combustion of the flue gas. The air inlet end of the gas bin 1210 is provided with a third valve (not numbered in the figure) for regulating the gas inlet amount, and the gas bin 1210 is communicated with the second gas inlet end. Preferably, the first valve, the second valve and the third valve are all solenoid valves, so that the supply of gas and air can be automatically regulated and controlled conveniently.

Referring to fig. 5, the burner 100 of the present embodiment realizes low-nitrogen and low-carbon combustion by the following techniques:

(1) the dense-dilute type low NOx control technique is that the total amount of air supplied by natural gas combustion is kept constant, i.e. the air excess coefficient α is kept at a normal value, to ensure that the natural gas is completely burned out, the air is supplied in two parts, the natural gas is also supplied in two parts, one part is supplied to the central pilot burner for combustion, and the air can be mixed with the outer circulation flue gas, i.e. the outer exhaust flue gas after the industrial furnace is burned out is introduced by the second fan 610 (circulation flue gas fan), and is mixed into the air bin 1220 or the second air supply pipe 122 (secondary air pipe) with a certain proportion of flue gas amount (oxygen content is 3% -6%), and enters the central main ignition burner air duct with the secondary air, so that under the condition that the secondary air is sprayed out in a small amount (α < 1), the natural gas of the central main ignition burner is under the incomplete combustion condition, and a diffusion cone of the central main ignition burner is added to form a negative pressure zone, the fuel is used as over-dilute combustion, the cyclone type and the temperature of the cyclone type NOx is very low, thereby the generation of the generated gas is inhibited, and the secondary air flow of the cyclone burner generates a great amount of air, and the cyclone flame is formed under the condition that the ring flame generated by the ring of the ring flame generated by the high flame generated by the cyclone burner (α).

(2) Flame cutting type low NOx control technology: the natural gas fuel is split into two parts, primary and secondary fuel. The main fuel enters the gas cabin 1210 (annular fuel belt), under the action of the impeller ring system, a large amount of secondary air enters the second cyclone to form small flames of rotating air flow, so that a large amount of main fuel is divided into a plurality of small groups of flames, the temperature of the flames sprayed by the small groups of flame spray guns is lower (less than 1300 ℃), the generation of NOx is inhibited, the retention time of combustion flue gas in a high-temperature combustion area is shortened, and the generation of NOx is further prevented.

(3) A flue gas recycling control technology; when the natural gas is fully combusted, the natural gas and the supplied air produce violent thermochemical reaction, and oxygen O in the air₂The content is almost completely consumed, the oxygen content in the flue gas is only 3% -6%, the low-oxygen flue gas enters the combustion system again, great benefits are brought to the inhibition of NOx generation, and the method is one of effective means for reducing NOx.

With reference to fig. 2 and 4, the circulating flue gas can be divided into two types, one is that the circulating flue gas enters the combustion system from the outlet of the first fan (300 induced draft fan) of the industrial furnace, and then enters the ventilation duct of the central lance through the fourth valve 630 and air according to a proper ratio. Low temperature reduction combustion is formed at the diffusion cone of the lance head within the central passage, thereby suppressing the generation of NOx. The other is that the internally circulated flue gas enters a combustion system, under the action of a relative negative pressure region near the rear of the outlet end (the end part of the first fuel gas supply pipeline 111 is provided with a diffusion cone structure), a large amount of flue gas which is not combusted or incompletely combusted is generated, and under the action of reduction reaction, low-temperature CO and H are generated₂Equal combustible gas (natural gas with CH as main component)₄Over 95 percent) is sucked into the internal circulation channel under the action of the negative pressure area, and is mixed with a large amount of primary air and then is sprayed into the furnace for combustion. The internal circulation of the flue gas starts to continuously circulate and burn as long as the ignition of the natural gas is successful. The internal circulation of the flue gas is that the primary air is mixed with part of low-temperature flue gas, so that the oxygen content of the primary air is further reduced, the temperature of a high-temperature area for burning natural gas is further reduced, and the time for the flue gas to stay in the high-temperature area is further shortened. Therefore, the three major factors of NOx generation, namely ultrahigh smoke combustion temperature, overhigh oxygen content of a combustion area and even the oxygen content of pure air, can be broken one by one when the internal and external circulation smoke enters the combustion system. Namely, the addition of the circulating flue gas is one of effective means for reducing or eliminating NOx of the fuel (coal, oil and gas) burner.

(4) Fuel and air staging supply control techniques; for the natural gas with high thrust, if the natural gas with high injection quantity is injected at one time, the combustion is not good, and safety accidents are caused. Therefore, it is necessary to supply natural gas in stages. The gas ignition of the gas burner is divided into two stages, namely a central main ignition spray gun which supplies gas for one stage, and the stage is also an ignition spray gun; the secondary natural gas fuel is a natural gas spray pipe in an annular shape and is divided into a plurality of small spray guns to form a plurality of small rotary small flames to form an annular flame belt. The larger the power is, or the larger the heat supply capacity is, the more the small annular spray guns are formed, so that the lower the temperature generated by combustion is, the shorter the retention time of the flue gas in a high-temperature area is; thereby also suppressing the generation of NOx.

In addition, the air quantity for supplying the gas combustion is more than ten times of the natural gas consumption quantity under the condition according to working conditions. Such a larger fan is not possible to design and install integrally with the burner. Therefore, the air required for combustion must be supplied in multiple stages, which varies with the gas supply. The difference is that all the gas flows are led to the rotating jet flow to generate the rotating flame with the equidirectional gas trickle and air rotation mixing. In the flame produced in this way, the mixing effect of the fuel gas and the air is better, and the temperature is lower. The generation of NOx is further suppressed.

(5) The mixed control technology of the thin flow sprayed by the fuel gas and the rotating air flow; compared with fossil energy such as coal and oil, natural gas is clean fossil energy; the calorific value is 8500kcal/Nm³On the left and right, the products of thermal decomposition are CO and H₂And when combined with a certain proportion of air to reach the ignition point, the combustion is violent. Therefore, the ejected air stream must be thin and high-speed. Most of domestic and overseas fuel gas is sprayed out at a certain angle with high-speed fuel gas flow to meet and mix with the air trickle to generate combustion, but the effect is not ideal. If the high-speed gas trickle at a certain angle and the rotating air flow at a certain angle are mixed, the effect is more ideal. The combustor is based on the working principle and is completely a rotary gas flow and an air flow so as to achieve more ideal combustion flame and save more than 10% of gas. The combustion of combustible components is cleaner and more thorough, the CO content in the flue gas at the tail of the furnace is almost zero, the fuel gas almost contains no sulfur and no dust, and the national flue gas emission environmental protection standard can be reached only by removing NOx.

Referring to fig. 6, the present invention further provides a gas system, which includes the burner 100, the boiler 200, the first fan 300 and the exhaust tower 400. The second air outlet end of the burner 100 is connected to the boiler 200, the end portions of the first gas outlet end, the first air outlet end, the second air outlet end and the second gas outlet end all extend into the boiler 200, the exhaust port of the boiler 200 is connected to the first fan 300, and flue gas combusted in the boiler is discharged through the first fan 300. The first fan 300 is connected to the exhaust tower 400 through an exhaust duct, so that a negative pressure region is formed in the boiler 200, and the burned flue gas is discharged.

Further, the gas system of the present embodiment further includes a flue gas external circulation duct 610 and a second fan 620. The gas inlet end of the flue gas outer circulation pipeline 610 is connected with the exhaust pipeline, the gas outlet end of the flue gas outer circulation pipeline 610 is connected with the first air supply pipeline 112, the flue gas outer circulation pipeline 610 is further provided with a fourth valve 630, and the second fan 620 is connected in series with the flue gas outer circulation pipeline 610 so as to mix the flue gas exhausted from the boiler 200 with the air again and then perform circulating combustion, and the generation of NOx can be further reduced.

Further, the gas system of the present embodiment further includes an air preheater 500 and a third fan 510. Air heater 500 concatenates between first fan 300 and boiler 200, and air heater 500 still connects first air inlet end and second air inlet end respectively through the pipeline, and air heater 500 connects third fan 510 in order to absorb fresh air, treats the air that gets into in first air supply pipeline 112 and the second air supply pipeline 122 and preheats, not only can improve combustion efficiency and burn-off rate, can also make full use of the waste heat of burning flue gas, practices thrift the energy consumption.

Further, the gas system of the present embodiment further includes a controller. The controller is respectively connected with the first combustion mechanism, the second combustion mechanism, the air preheater 500, the first fan 300, the second fan 620 and the third fan 510. The controller is preferably a PLC program controller, so that the whole gas process can be automatically regulated and controlled conveniently.

Further, the gas system of the present embodiment further includes an economizer 700, and the economizer 700 is connected in series between the air preheater and the boiler.

In general, the burner 100 and the gas system remove NOx through five control techniques, thereby removing NOx to the maximum. In addition, the burner 100 and the gas system can strictly control the gas and air quantity through the cooperation of the controller, the detection element, the various valves, the interlocking, the automatic control and the like, so as to form the interconversion between big fire and small fire; the application of the ignition and fire detection technology forms a one-key switch, safe starting and safe operation are realized, and the control requirement of imported products and the DCS networking communication requirement are basically met. Compared with domestic and foreign gas burners of the same type and model, the natural gas can be saved by more than 10% at least, which is significant for the import of a large amount of natural gas in China today. Compared with the old natural gas burner with the same model, the natural gas can be saved by more than 15 percent.

Meanwhile, the combustor 100 has low manufacturing cost and high competitiveness, and the final economic performance of the product can reach: nitrogen oxides (NOx) < 30mg/m³The content of the active carbon can reach 20mg/m under ideal conditions³The following; the content of carbon monoxide (CO) is approximately 0-0.001 or less, which indicates that the combustion of the natural gas is complete.

The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above description is only for the preferred embodiment of the present invention, and is not intended to limit the present invention, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included within the protection scope of the present invention.

Claims

1. A burner, comprising a first combustion means and a second combustion means;

the second combustion mechanism comprises a second air supply pipeline, a second fuel gas supply pipeline, a second ignition spray gun and a second cyclone, the second air supply pipeline is sleeved on the first air supply pipeline and is provided with a second air inlet end and a second air outlet end, the second gas supply pipeline penetrates through the second air supply pipeline, the second gas supply pipeline is used for connecting a second gas inlet end of a gas source and a second gas outlet end for supplying gas to the boiler, the second gas outlet end, the second air outlet end and the first gas outlet end are arranged on the same side, the second ignition spray gun is arranged in the second air supply pipeline or the second fuel gas supply pipeline in a penetrating mode and extends to the air outlet end of the second air supply pipeline for ignition, and the second cyclone is arranged at the air outlet end of the second air and used for rotating combustion airflow.

2. The burner of claim 1, wherein the second air outlet end surrounds the first air outlet end and cooperates with the first air outlet end to form a cavity in communication with the second air supply conduit, and a partition is disposed in the cavity to form an internal circulation path for circulating the combustion air flow.

3. The burner of claim 1, further comprising a fire detection structure disposed through the first air supply conduit and extending to the air outlet end thereof.

4. The burner according to any one of claims 1 to 3, wherein the first combustion mechanism further comprises a mixing chamber for mixing air and combusted flue gas, a first valve for regulating and controlling the air inlet amount is arranged at the air inlet end of the mixing chamber, and the air outlet end of the mixing chamber is communicated with the first air supply pipeline.

5. The burner of claim 4, wherein the second combustion mechanism further comprises an air bin and a gas bin, the gas bin and the air bin are sleeved in the first air supply pipeline in parallel, a second valve for regulating and controlling the air inlet amount is arranged at the air inlet end of the air bin, and the air bin is communicated with the second air inlet end; the air inlet end of the gas bin is provided with a third valve used for regulating and controlling the gas inlet amount, and the gas bin is communicated with the second gas inlet end.

6. The burner of claim 5, wherein the first valve, the second valve, and the third valve are all solenoid valves.

7. A gas system comprising a boiler, a first fan, an exhaust tower and a burner as claimed in any one of claims 1 to 6;

the second air outlet end is connected with the boiler, the end parts of the first gas outlet end, the first air outlet end, the second air outlet end and the second gas outlet end extend into the boiler, an air outlet of the boiler is connected with a first fan, and the first fan is connected with the exhaust tower through an exhaust pipeline.

8. The gas system according to claim 7, further comprising a flue gas external circulation pipeline and a second fan, wherein an inlet end of the flue gas external circulation pipeline is connected to the exhaust pipeline, the second fan is connected in series to the flue gas external circulation pipeline, an outlet end of the flue gas external circulation pipeline is connected to the first air supply pipeline, and the flue gas external circulation pipeline is further provided with a fourth valve.

9. The gas system of claim 8, further comprising an air preheater and a third fan;

the air preheater is connected in series between the first fan and the boiler, the air preheater is further connected with a first air inlet end and a second air inlet end through pipelines respectively, and the air preheater is connected with the second fan.

10. The gas system of claim 9, further comprising a controller, said controller being connected to said first combustion mechanism, said second combustion mechanism, said air preheater, said first fan, said second fan, and/or said third fan, respectively.