CN117091133A - Low nitrogen combustion head of flue gas inner loop - Google Patents

Abstract

The invention discloses a smoke internal circulation low-nitrogen combustion head which comprises a gas distributor, an air guide disc, a gas collector and a central combustion head, wherein the gas distributor comprises a cylindrical shell, one end of the cylindrical shell is connected with a burner flange, a circular cavity is arranged in the other end of the cylindrical shell, the air guide disc is hollow conical, the outer edge of the air guide disc is connected with the inner edge of the end part of the circular cavity, which faces one end of a combustion chamber, the outer edge of the air guide disc is positioned on the same plane with the inner wall of a front wall of the combustion chamber, and the central combustion head penetrates out of a hollow inner edge central hole of the air guide disc and stretches into the combustion chamber. The smoke internal circulation low-nitrogen combustion head does not use parts such as a flame tube, utilizes the space of the combustion chamber to the greatest extent, carries out smoke internal circulation, realizes effective mixing of smoke, fuel gas and air, reduces the combustion reaction intensity, enlarges the combustion reaction area, ensures that the temperature inside the combustion chamber is balanced, avoids local high temperature, and reduces the generation of nitrogen oxides.

Description

Low nitrogen combustion head of flue gas inner loop

Technical Field

The invention belongs to the technical field of burners and air-fuel gas-flue gas mixing devices related to the burners, and particularly relates to a flue gas internal circulation low-nitrogen combustion head. The present invention relates to an associated industrial burner of the type comprising a burner head mounted on a combustion chamber, the fuel being natural gas for systems without external fume circulation.

Background

Nitrogen oxides (NOx) are known to be toxic and harmful gases, wherein the combustion process mainly comprises thermal nitrogen oxides, and the method is characterized in that as the temperature of flame and combustion area increases, the emission of pollutant nitrogen oxides also increases exponentially, and how to control the flame temperature for reducing combustion becomes the main technical means for reducing thermal nitrogen oxides.

The flue gas circulation technology is widely used in boiler systems, and mainly comprises carbon dioxide, water vapor and nitrogen, wherein the main components of the flue gas generated by combustion are carbon dioxide, and the non-combustible flue gas is conveyed into a combustion area again in a circulation mode, so that combustible substances and oxidants are diluted by the flue gas and then burnt in the chemical reaction process of combustion, the intensity of the combustion reaction is reduced, the flame temperature is reduced, the temperature of the combustion area is also reduced, the condition that oxygen and nitrogen generate thermal nitrogen oxides is effectively weakened, and the generation of the nitrogen oxides is reduced.

The flue gas circulation technology is basically divided into two types of flue gas circulation technology, namely flue gas external circulation and flue gas internal circulation. The external circulation of the flue gas is that a part of flue gas is extracted at a flue gas outlet at the tail part of the boiler, the flue gas is sent into combustion air, and the flue gas and the combustion air are mixed and then enter a combustion area together; the internal circulation of the flue gas is to directly circulate the flue gas into the combustion area in the combustion chamber by the swirling airflow formed in the combustion chamber of the boiler. The difference between the internal and external flue gas circulation means whether the circulation of the flue gas occurs inside or outside the combustion chamber. In many cases, the internal and external circulation are combined, the internal circulation technology of NOx less than or equal to 80mg/m < 3 > is mature, and NOx less than or equal to 30mg/m < 3 > can be achieved by combining the external circulation.

The widely used machine type in the market is a diffusion type burner with an additional flue gas external circulation technology, so as to reduce the emission of nitrogen oxides. The burner head of this type of burner is relatively simple in construction and reliable in operation. Because the working principle is to circularly burn the smoke by using a fan, the power of the fan is required to be increased or the smoke circulating fan is used, which causes the increase of investment cost.

In addition, the flue gas return pipes of most field installation are connected to the combustor air-blower air inlet side, and flue gas temperature is higher, and combustion-supporting air temperature is lower, and vapor in the flue gas can condense when two meet cold and become water when crossing, causes the corruption of junction, and the comdenstion water gets into the combustor when serious and leads to flame detector sensing part and ignition element to break down, produces the potential safety hazard. In addition, condensed water enters the shell of the burner, and the inner parts of the burner and the shell of the shell are corroded by the impeller of the blower, so that the service life of the burner is influenced.

In order to meet the effect of reducing nitrogen oxides, the flue gas internal circulation machine type used in the market generally requires that the diameter of a boiler combustion chamber is large enough and the backflow space of the internal circulation is sufficient, so that the internal circulation effect of sufficient flue gas quantity can be ensured. The size of the combustion chamber is increased, resulting in a substantial increase in the cost of the boiler.

In these flue gas recirculation type burners, although the purpose of reducing nitrogen oxides is achieved by feeding flue gas into the combustion area by a circulation method, when a lower emission index is pursued, the circulation amount of flue gas must be increased to further reduce the intensity of combustion flame, and these methods cause a decrease in combustion stability, and combustion surge, flame instability and an increase in the failure rate accompanying the operation of the burner are likely to occur.

In the patent document DE 3811477 A1, it is described that for a gas burner, gas is mixed with air at the inlet of the combustion chamber, the gas being admitted through some mixing tubes. Wherein the fuel gas is directly sent into the inlet of the combustion chamber through the gas mixing pipe and the nozzle thereof, and is mixed with the combustion air to enter the combustion chamber. The outlets of the gas pipes are distributed in different tangential planes in the mixing cavity of the burner according to the divergent direction.

In DE 195 09 219, a burner is described for a burner head for a burner in which combustion air is supplied while combustion air is burned, nitrogen oxides are reduced by means of inert gas, wherein the fuel air is divided into two stages, one stage is superimposed behind the other stage, the combustion air is blown in from the root of the flame in the flow direction of the combustion air, the mixed gas of the combustion air and the fuel air of the first stage super-chemical reaction ratio flows to the flame, the supplementary fuel gas is added in the tangential plane of the second stage, the flue gas circulated back where is added as inert gas to the second stage, a part of the combustion gas is injected into the second stage to form a mixed gas lower than the chemical reaction ratio with the circulated flue gas, and the mixed gas is mixed before reaching the flame.

Patent EP 0 635 676 describes a low NOx burner for liquid or gaseous fuels, the burner of which projects into the combustion chamber of a boiler, the burner having at least one fuel nozzle in the burner cartridge for supplying fuel and adjacent to the burner plate, which delivers a large quantity of fuel gas from the burner plate outwards to the inner wall area of the burner cartridge, the rapid gas flow through the gap between the burner cartridge and the burner plate creating a negative pressure at the front edge of the burner cartridge, the flue gases produced in the combustion chamber being fed to this negative pressure area by internal circulation, the burner cartridge having a plurality of flow guide corners extending into the negative pressure area.

Chinese patent CN112178626B describes an internal circulation low nitrogen gas burner, a cyclone is sleeved at one end of a first gas pipe, an annular gas pipe is sleeved at the outer side of the cyclone and in clearance fit with the cyclone, a second gas pipe conveys gas to the annular gas pipe, a splitter pipe is sleeved at the outer side of the annular gas pipe, and a flow separation member is sleeved at the outer side of a splitter pipe and forms a flue gas channel with the splitter pipe. The gas components of the inner rings are positioned in the flue gas channel, and the gas components of the outer rings are arranged on the periphery of the flow separation piece. The shunt tubes are used for shunting air to form air for mixing cigarettes and air for mixing combustion, negative pressure is generated at a smoke inlet when the air for mixing cigarettes flows through a smoke channel, so that smoke in a combustion chamber is sucked, and the air for mixing cigarettes participates in combustion again. Because of the way of directly recycling the smoke by utilizing vacuum, not only is a smoke channel omitted and the potential safety hazard eliminated, but also the use cost is reduced.

Chinese patent CN107120652 describes a staged gas low nitrogen burner, which relates to the burner technical field. The staged gas low nitrogen burner includes a distributor, a baffle plate, an ignition electrode, an ignition fuel tube and a combustion can. The distributor is used for providing a flow path for fuel gas and air and comprises a body, a plurality of fuel gas spray pipes, a fuel gas distribution ring and a plurality of air distribution pipes. The body is a cylinder with a first interlayer, and the fuel gas is sprayed out from the fuel gas distribution ring after entering the fuel gas pipe through the body. The air flows through the hollow part of the body, the air distribution pipe and the outer side of the distributor to form an air flow path for providing combustion-supporting gas for the fuel gas. The distribution ring of CN107120652 is thinner, and is shown as not greater than 4 times the diameter of the gas distribution hole, but the gas is distributed as an inner and outer ring, and the function of separating air is not provided. The deflector of CN107120652 deflects the air introduced from the plurality of air distribution pipes to form a rotating air flow, the main body is air, and no gas distribution device is provided.

The above-mentioned known methods and structures are not adequate to achieve the increasing demands for reduction of pollutant emissions from combustion plants, especially when the emissions levels of nitrogen oxides are further reduced as required by legal regulations, which are limited or have problems with excessive levels of nitrogen oxides or unstable combustion, which are difficult to meet environmental emission standards.

The invention eliminates the flame tube used by the traditional burner. And the high-speed air flow is obtained by utilizing the conical closing-in structure of the air guide disc, so that the internal circulation of the flue gas is realized. Wherein the high velocity air stream, when blown into the combustion chamber, creates an accompanying vortex of surrounding air flow within the combustion chamber. When air flows through the conical air guide disc at high speed, a negative pressure area is formed on the back surface of the air guide disc, the negative pressure of the negative pressure area can guide vortex flow from the outer ring of the combustion chamber to the negative pressure area on the back surface of the air guide disc in a countercurrent direction, the air naturally turns after reaching the negative pressure area, and then is converged with air flow to the outlet direction of the combustion chamber together with combustion air in a forward flow direction. In the combustion state, the backflow vortex is the smoke generated by combustion, and the smoke forms an internal circulation mode.

The most important and different of the invention is that under the condition of not adopting the flame tube of the traditional burner, the air flow circulation is carried out by taking all the combustion chambers as free spaces, the optimized space proportion of the countercurrent and the downstream flue gas is naturally formed, the artificial interference is eliminated, and the space of the combustion chambers is utilized to the greatest extent. Through reasonable arrangement of the positions of the gas nozzles, the gas flow and the flue gas and the air flow are smoothly converged, well mixed and stably combusted. The combustion reaction intensity is reduced, the combustion reaction area is enlarged, the temperature inside the combustion chamber is balanced, the local high temperature is avoided, and the generation of nitrogen oxides is reduced.

Disclosure of Invention

The invention aims to solve the problems, and aims to provide the smoke internal circulation low-nitrogen gas burner which is stable, safe, compact in structure, efficient and environment-friendly.

The technical scheme of the invention is that the low-nitrogen combustion head comprises a gas distributor, an air guide disc, a gas collector and a central combustion head, wherein the gas distributor is cylindrical and comprises a cylindrical shell, one end of the cylindrical shell is connected with a burner flange, a circular annular cavity is arranged in the other end of the cylindrical shell, the air guide disc is hollow conical, the outer edge of the air guide disc is connected with the inner edge of the end part of the circular annular cavity, which faces one end of a combustion chamber, the outer edge of the air guide disc is positioned on the same plane with the inner wall of the front wall of the combustion chamber, the central combustion head penetrates through a central hole of the inner edge of the hollow air guide disc of the air guide disc and stretches into the combustion chamber, one end of the circular annular cavity is connected with the gas collector, and the other end of the circular annular cavity is connected with a plurality of gas nozzle pipes, and the gas nozzle pipes stretch into the combustion chamber, so that a gas channel is formed to introduce gas in the gas collector into the combustion chamber.

Further, the gas collector comprises a central gas connecting pipe and an outer ring gas connecting pipe, the inlet ends of the central gas connecting pipe and the outer ring gas connecting pipe are connected with a gas main pipe, the outlet end of the central gas connecting pipe is connected with the central burner, and the outlet end of the outer ring gas connecting pipe is connected with the annular cavity.

Furthermore, the outer ring gas connection pipes are multiple, and are connected to the annular cavity in an annular and uniform distribution mode.

Further, the end face of the annular cavity connected with the gas nozzle pipe is provided with a plurality of evenly distributed circular openings for connecting with the gas nozzle pipe to form a gas channel, and the inner space formed by connecting the cylindrical shell with the air guide disc forms a combustion air circulation channel.

Further, a circulating annular gap channel for combustion air is formed between the inner edge of the air guide disc and the central burner.

Further, the central burner comprises a central gas pipe and a sleeve, the sleeve is sleeved outside the central gas pipe, an air flow channel is formed between the sleeve and the central gas pipe, an air swirler is arranged at the outlet end of the sleeve, a flame stabilizing baffle plate and a gas distribution hole are arranged at the outlet end of the central gas pipe, and the central gas pipe is connected with a central gas connecting pipe of the gas collector.

In summary, the beneficial effects of the invention are as follows: the invention provides a smoke internal circulation combustion head technology for enabling parts such as a flameless tube to extend into a combustion chamber, which maximally utilizes all combustion chambers as circulation spaces and realizes low nitrogen oxide emission under the condition of smaller diameter of the combustion chambers. Because the combustion head does not use parts such as flame tubes, the structure of the combustion head is simplified, and the manufacturing cost is reduced. Parts such as a flame tube and the like are not exposed in the high-temperature combustion chamber, the height Wen Sunhao of the combustion head is avoided, and the service life of equipment is prolonged.

Drawings

FIG. 1 is a schematic diagram of a flue gas internal circulation low nitrogen combustion head of the present invention in a combustion chamber.

FIG. 2 is a schematic flow diagram of the gas and combustion air and flue gas of the flue gas internal circulation low nitrogen burner of the present invention in the combustion chamber.

FIG. 3 is a schematic diagram of the structure of the flue gas internal circulation low-nitrogen combustion head of the invention.

FIG. 4 is a cross-sectional view of a flue gas internal circulation low-nitrogen burner head structure according to the present invention

Reference numerals: 1. a combustion chamber; 2. a combustion head; 3. a gas distributor; 4. a gas collector; 5. an air guiding disc; 6. a central burning head; 11. a combustion chamber front wall; 12. a furnace wall of the combustion chamber; 13. a heating medium; 21. a burner flange; 31. a cylindrical housing; 32. a circular ring cavity; 33. a gas nozzle tube; 41. an air inlet main pipe; 42. an outer ring gas connecting pipe; 43. a central gas connection pipe; 51. the outer edge of the air guide disc; 52. the inner edge of the air guide disc; 61. a central gas pipe; 62. a sleeve; 63. a cyclone; 64. a gas jet orifice; 65. flame stabilizing baffle plate.

Detailed Description

In order to make the technical means, technical features, achieving the object and technical effects of the present invention easy to understand, the present invention is specifically described below with reference to the embodiments and the accompanying drawings.

As shown in fig. 1 to 4, which illustrate the specific principle and specific structure of the internal circulation low nitrogen burner head of the present invention.

As shown in fig. 1 and 3, an internal circulation low-nitrogen burner 2 of the present invention is mounted on a front wall 11 of a burner 1 through a burner flange 21, a heating medium 13 is provided outside a furnace wall 12 of the burner, an outer edge 51 of an air guiding plate 5 of the burner 2 is flush with an inner wall of the front wall 11 of the burner, and a gas nozzle tube 33 and a central burner 6 extend into the burner 1.

As shown in fig. 3 and 4, the present invention discloses a specific structure of an internal circulation low-nitrogen burner, which comprises a gas distributor 3, a gas collector 4, an air guiding disc 5 and a central burner 6, wherein the gas distributor 3 comprises a cylindrical shell 31, one end of the cylindrical shell 31 is connected with a burner flange 21, the other end is connected with an air guiding disc outer edge 51 of the air guiding disc 5, and an air circulation channel is formed in an inner space formed by the cylindrical shell 31. The central burner 6 penetrates out from the central hole of the hollow air guide disc inner edge 52 of the air guide disc 5, and an annular gap formed between the air guide disc inner edge 52 and the central burner 6 is an outlet for air to flow out of the burner, so that a combustion-supporting air circulation channel is formed. The cylindrical shell 31 of the gas distributor 3 comprises a circular cavity 32 in one end of the cylindrical shell facing the combustion chamber, one end of the circular cavity 32 is connected with an outer ring gas connecting pipe 42 of the gas collector and distributor 4, a plurality of uniformly distributed circular openings are arranged on the end face of the other end of the circular cavity 32 and are used for being connected with the gas nozzle pipe 33, the gas nozzle pipe 33 stretches into the combustion chamber 1 to form a gas channel, and an inner space enclosed by the connection of the cylindrical shell 31 and the air guide disc 5 forms a combustion air circulation channel. The air guide disc 5 is positioned on the inner wall of the front wall of the combustion chamber, and no other parts except the gas nozzle pipe 33 and the central burner 6 extend out of the air guide disc 5 and extend into the combustion chamber 1. The gas nozzle pipe 33 connected with the gas distributor extends into the combustion chamber 1 beyond the air guide disc 5 to form enough space, when the gas in the gas nozzle pipe 33 is sprayed out, the surrounding is completely the flue gas flow in the same flow direction, and the gas, the flue gas and the air are converged and mixed in the process of flowing towards the outlet direction of the combustion chamber 1, and stay in the backflow area for combustion. The central burner 6 provides a stable rooting flame for the whole combustion, ensuring the stability of the combustion.

As shown in fig. 3 and fig. 4, the air guiding disc 5 is located at the plane position of the inner wall of the front wall of the combustion chamber, and the air guiding disc 5 is used as a boundary, except that the gas nozzle 33 and the central burner 6 extend beyond the air guiding disc 5 and extend into the combustion chamber 1, no other parts extend into the combustion chamber, and the whole combustion chamber starts from the front wall to form a complete internal circulating and backflow space of flue gas.

As shown in fig. 3, the air guiding disc 5 has a hollow conical structure, the outer edge 51 of the air guiding disc is connected with the end face of the end of the gas distributor 3 with the nozzle, and the hollow part of the inner edge 52 of the air guiding disc is provided with a central burner 6 extending out of the central burner. Because the air guide disc 5 is in a conical closing structure, the air flow with the highest flow speed can be obtained, and the air flow with the highest flow speed is sprayed to the combustion chamber 1 through the annular gap formed by the inner edge 52 of the air guide disc and the central burner 6. The high velocity air stream, when blown into the combustion chamber, creates an accompanying vortex of surrounding air flow within the combustion chamber. Meanwhile, when air flows through the conical air guide disc 5 at a high speed, a negative pressure area is formed on the back surface of the air guide disc 5, the negative pressure can guide vortex flow from the outer ring of the combustion chamber to the negative pressure area on the back of the air guide disc 5 in a countercurrent direction, and after reaching the negative pressure area, the air naturally turns and then merges with high-speed air flow, and flows along with combustion air in a forward direction to the outlet direction of the combustion chamber 11. In the combustion state, the backflow vortex is the smoke generated by combustion, and the smoke forms an internal circulation mode.

In fig. 2, a schematic diagram of the flow direction of the gas and combustion air of the invention is shown, wherein the combustion air a enters the burner head 2, and enters the combustion chamber 11 through the air channel formed by the gas distributor 3 and the air guiding disc 5. Due to the conical closing structure of the air guiding disc 5, the combustion air A reaches the highest flow velocity when passing through, the air flow with high flow velocity is blown into the combustion chamber 11 to form an accompanying vortex D surrounding the air flow, meanwhile, when the air flow with high flow velocity flows through the air guiding disc 5, a negative pressure area is formed on the back surface of the air guiding disc, the part of negative pressure guiding vortex D flows to the air guiding disc 5 from the outer ring of the combustion chamber in the countercurrent direction C1, naturally turns after reaching the air guiding disc, merges with the air flow in the concurrent direction C2 and flows to the outlet direction of the combustion chamber together. In the combustion state, the backflow vortex flows C1 and C2 are smoke generated by combustion, and the smoke forms an internal circulation mode. The outer ring gas B2 part of the gas B enters the gas distributor 3 through the outer ring connecting pipe 42 of the gas collector 4 and enters the combustion chamber 1 through the nozzle pipe 33, the outer ring gas B2 is positioned in the middle of the gas flow of the forward flow gas C2 when being sprayed out, the converged gas B2, the gas C2 and the air stay in the vortex area for combustion, the combusted gas C is except the countercurrent flow C1, and the rest part of the combusted gas C flows out of the combustion chamber in the forward flow direction. The central fuel gas B1 is sent into the central burner 6 by the central fuel gas connection pipe of the fuel gas collector 4, and the central flame F provides a stable rooting flame base point for integral combustion.

As shown in fig. 4, the gas distributor 3 is a cylindrical shell with a circular annular cavity 32 embedded therein, one end of the annular cavity 32 is connected with an outer ring gas connection pipe 42 of the gas collector 4, and the other end face is provided with a plurality of circular openings uniformly distributed for connecting the gas nozzle pipe 33, so that gas enters from a main gas pipe 41 of the gas collector 4, then is connected into the annular cavity of the gas distributor 3 through four outer ring gas connection pipes 42, and is distributed into the combustion chamber through the gas nozzle pipe 33 to form an outer ring gas channel. One end of a cylindrical shell 31 of the gas distributor 3 is connected with a burner flange 21, and an inner space surrounded by the cylindrical shell 31 and the air guide disc 5 forms a passage for circulating combustion air.

As shown in fig. 1 and 3, the outlet of the gas nozzle pipe 33 exceeds the air guiding disc 5, and extends into enough space in the combustion chamber 1, so that when the gas is ejected, the gas flow is located in the concurrent flue gas flow circulating in the flue gas.

As shown in fig. 4, the gas collector 4 includes a central gas connection pipe 43 and an outer ring gas connection pipe 42, and an inlet end of the gas collector 4 is connected to the gas main pipe 41. The outlet end of the central gas connection pipe 43 is connected with a central gas pipe 61 of the central burner 6, and the outlet end of the outer ring gas connection pipe 42 is connected with the gas annular cavity 32 of the gas distributor 3.

As shown in fig. 4, the central burner 6 includes a central gas pipe 61 and a sleeve 62, the sleeve 62 is sleeved outside the central gas pipe 61, a combustion air channel is formed between the sleeve 62 and the central gas pipe 61, an air swirler 63 is disposed at the outlet end of the sleeve 62, a gas spray hole 64 is disposed at the outlet end of the central gas pipe 61, and a flame stabilizing baffle 65 is disposed at the outlet end. The central gas pipe 61 is connected to the outlet end of the central gas nipple 43 of the gas collector.

The sleeve 62 of the central burner 6 can protect the central flame from being blown off, and provides a reliable rooting flame base point for the whole combustion so as to ensure the stability of the whole combustion. When the high-flow-rate air flow is blown out by wrapping the sleeve 62, the central fire can be effectively cooled, and nitrogen oxides generated by the central fire can be reduced.

The air guide disc 5 used in the invention is arranged at the position of the inner wall 11 of the front wall of the combustion chamber, and provides a smoke internal circulation combustion head technology for enabling parts such as a flameless tube to extend into the combustion chamber, so that the parts such as the flame tube are not used, the space of the combustion chamber is utilized to the greatest extent, the smoke circulation is realized, the effect of effectively mixing the smoke, the fuel gas and the air under the condition of smaller diameter of the combustion chamber is realized, the combustion reaction intensity is reduced, the combustion reaction area is enlarged, the internal temperature of the combustion chamber is balanced, the local high temperature is avoided, the generation of nitrogen oxides is reduced, and the low nitrogen oxide emission is realized.

Meanwhile, as parts such as a flame tube and the like are not used, the structure of the combustion head is greatly simplified, and the manufacturing cost is reduced. Parts such as a flame tube and the like are not exposed in the high-temperature combustion chamber, the height Wen Sunhao of the combustion head is avoided, and the service life of equipment is prolonged.

Claims (6)

1. The utility model provides a flue gas internal circulation low nitrogen combustion head, its characterized in that includes gas distributor, air wind-guiding dish, gas collector and center burner, wherein gas distributor is the cylinder, and it includes the cylinder shell, the one end of cylinder shell is connected with the combustor flange, be equipped with the ring cavity in the cylinder shell other end, the air wind-guiding dish is hollow conical, the wind-guiding dish outer fringe of air wind-guiding dish with the ring cavity is connected towards the tip inner edge of combustion chamber one end, the wind-guiding dish outer fringe with the combustion chamber front wall inner wall is in the coplanar, center burner follow the hollow wind-guiding dish inner edge centre bore of air wind-guiding dish wears out and stretches into in the combustion chamber, ring cavity one end with gas collector is connected, its other end is connected with a plurality of gas nozzle pipes, the gas nozzle pipe stretches into in the combustion chamber, thereby forms the gas passageway with gas in the gas collector is introduced in the combustion chamber.

2. The flue gas internal circulation low-nitrogen combustion head according to claim 1, wherein the gas collector comprises a central gas connection pipe and an outer ring gas connection pipe, inlet ends of the central gas connection pipe and the outer ring gas connection pipe are connected with a gas main pipe, an outlet end of the central gas connection pipe is connected with the central combustion head, and an outlet end of the outer ring gas connection pipe is connected with the annular cavity.

3. The flue gas internal circulation low-nitrogen combustion head according to claim 1, wherein the outer ring of the fuel gas connection pipes are multiple, and are annularly and uniformly distributed and connected to the annular cavity.

4. The flue gas internal circulation low-nitrogen combustion head according to claims 1 and 2, wherein a plurality of evenly distributed circular openings are formed in the end face, connected with the gas nozzle pipe, of the circular cavity, so as to be connected with the gas nozzle pipe to form a gas channel, and an inner space surrounded by the cylindrical shell and the air guide disc is connected to form a circulating channel of combustion air.

5. The flue gas internal circulation low-nitrogen combustion head according to claim 1, wherein a circulating annular gap channel for combustion air is formed between the inner edge of the air guiding disc and the central combustion head.

6. The smoke internal circulation low-nitrogen combustion head according to claim 1, wherein the central combustion head comprises a central gas pipe and a sleeve, the sleeve is sleeved outside the central gas pipe, an air flow channel is formed between the sleeve and the central gas pipe, an air swirler is arranged at the outlet end of the sleeve, a flame stabilizing baffle plate and a gas distribution hole are arranged at the outlet end of the central gas pipe, and the central gas pipe is connected with a central gas connecting pipe of the gas collector.