CN111121021B

CN111121021B - Low-nitrogen combustion device with free diffusion premixed combustion layer and combustion head thereof

Info

Publication number: CN111121021B
Application number: CN201911306888.0A
Authority: CN
Inventors: 史星宇
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-12-18
Filing date: 2019-12-18
Publication date: 2022-05-24
Anticipated expiration: 2039-12-18
Also published as: CN111121021A

Abstract

The invention discloses a low-nitrogen combustion device with a free diffusion premixed combustion layer and a combustion head thereof. The combustion head comprises a combustion head body, and the combustion head body is provided with a central pipeline, a plurality of first annular layer pipelines, a plurality of second annular layer pipelines and a free diffusion premixed combustion layer; the first annular layer and the second annular layer are sequentially arranged on the outer side of the central pipeline; according to the invention, the first annular layer pipeline and the second annular layer pipeline are arranged on the periphery of the central pipeline, so that the combustion head body can form a plurality of mutually independent premixing areas on the periphery of the central pipeline along the radial direction, and the normal work of other areas cannot be influenced if one premixing area cannot work normally due to faults in the combustion process. The gas and the air can be fully premixed through the free diffusion premixed combustion layer, so that no local high-temperature point exists during combustion, and the generation of nitrogen oxides can be effectively and remarkably reduced.

Description

Low-nitrogen combustion device with free diffusion premixed combustion layer and combustion head thereof

Technical Field

The invention relates to a combustion device, in particular to a low-nitrogen combustion device which realizes full premixing of air and fuel gas through free diffusion.

Background

According to the statistics of the Chinese energy report, about 40 thousands of industrial boilers used in China by 2017, and the number of small civil boilers is larger (no statistical data is available temporarily). With the strict requirements of the country on environmental protection, environmental protection departments in various regions continuously issue texts requiring that old boilers are required to be discharged and transformed to reach standards, the number of clean energy sources is expected to be utilized to reach more than 70% by 2021, and the total amount is huge. Wherein, most of the boiler reconstruction is to replace the low-nitrogen burner to meet the low-nitrogen emission requirement, and the old boiler is directly replaced to meet the emission requirement.

At present, the known gas boiler burner is a relatively mature combustion technology, European and American low-nitrogen burner brands occupy the mainstream market in China, and some Chinese low-nitrogen burner brands gradually appear after 2015. Commonly used burners consist essentially of: the system comprises an air supply system (blower), a fuel system (natural gas), an electric control system, an ignition system and a detection system.

Generally, a stable ultra-low nitrogen burner head system is the direction in which each burner manufacturer is struggling. The prior known ultra-low nitrogen combustion head mainly comprises a full-premixing surface combustion head and a diffusion type low nitrogen combustion head, and the diffusion type low nitrogen combustion head mainly comprises two types: a diffusion type low-nitrogen combustion head and a front premixing diffusion type low-nitrogen combustion head. Through years of research and discovery of the applicant, the existing combustion heads respectively have the following characteristics:

Full-premixing surface combustion head

The full-premixing surface combustion head, as disclosed in fig. 1, comprises a motor 1 ', a mixer 2' and a combustion head 3 ', wherein gas and air are respectively injected into the mixer 2' (metal barrel) through pipelines, and after colliding, pressurizing and premixing in the mixer 2 ', the gas and the air are effused from a plurality of tiny pores around the mixer 2'. The combustion flame is then formed on the surface of the metal felt on the outer layer of the mixer 2'. The advantages are that: the requirement on gas pressure is not high, the gas can be matched with various hearths, the premixing is uniform, the combustion is sufficient, and the NOX emission is less than or equal to 30mg/m 3. At present, the boiler is used more on a small-tonnage boiler.

The disadvantages are as follows:

1. after the full-premixing surface combustion head is combusted for a long time, dust in the air and combustion carbon deposition including oxides of the metal felt can block small holes on the periphery of the metal barrel, so that a mixed gas outlet is blocked, and flame deflagrates in the metal barrel to cause explosion accidents of the metal barrel. The existing improvement mode is to reduce the blocking probability by increasing the filtering measures (air and fuel gas), but the air filter is blocked after being used for a long time, the ventilation quantity is reduced if the air filter is not cleaned in time, the oxygen supply quantity is insufficient, the nitrogen oxide emission is influenced if the ventilation quantity is not cleaned in time, and accidents occur if the nitrogen oxide emission is serious.

Diffusion type low-nitrogen burner

2.1 pure diffusion type low-nitrogen combustion head

The pure diffusion type low-nitrogen combustion head is characterized in that a plurality of gas and air pipelines are arranged at the front end of the combustion head, and are sprayed into a hearth through pressure to form premixing in the hearth, and the layered and segmented combustion can also be made. The aim of low nitrogen emission needs an auxiliary means of FGR (flue gas recirculation), about 20-25% of low-temperature flue gas returns to a hearth through a flue gas circulating pipeline, and the aim of reducing NOX is fulfilled.

The disadvantages are that:

1. the requirement on the gas pressure is high, partial transformation areas cannot be boosted, and the transformation is difficult.

2. The requirement on the size of a hearth is high when the boiler is reconstructed, and the hearth cannot be enlarged by an old boiler. Many boilers which are just used for two or three years are forced to be changed, and the enterprise burden is increased.

3. The newly-built boiler requires enlarging a hearth and increases the manufacturing cost of the boiler.

4. Under the condition that NOX is less than or equal to 30mg/m3, an FGR (flue gas recirculation) means is needed for assistance, and the FGR means can generate acidic condensed water to enter a hearth, so that the heat efficiency of the boiler is reduced, a combustor and the hearth are corroded, and the service life of the boiler is reduced.

5. When some users find that the FGR valve is closed, the stealing discharge can be avoided.

6. The condensed water generated by FGR in extremely cold areas can be rapidly condensed into ice blocks to block the inlet of a fan, so that the phenomenon of furnace shutdown is caused. Or partial ice blocks are sucked into the fan to damage the impeller of the fan, so that the performance of the equipment is unstable, the maintenance rate is increased, and the service life of the equipment is shortened.

7. The air and the fuel gas are not mixed fully and uniformly, the combustion is incomplete, and the oxygen content is higher. The method has the defects that local high-temperature points exist, debugging is difficult, NOx emission is less than or equal to 30mg/m3 and can only be limited to a certain detection point, and the NOx emission is less than or equal to 30mg/m3 stably in the whole process.

2.2 Pre-mixing diffusion type low-nitrogen burner

The front premixing diffusion type low-nitrogen combustion head is characterized in that partial premixing gas is made in advance at the air inlet section of the combustor and then is injected into a hearth for combustion in a mode of combining a diffusion disc and a pipeline. The aim of low nitrogen emission needs an auxiliary means of FGR (flue gas recirculation), about 15-20% of low-temperature flue gas returns to a hearth through a flue gas circulation pipeline, and the mode can partially reduce oxygen content and reduce NOx generation.

The disadvantages are as follows:

1. the technology has the advantages that the section part of the gas premixing device is added, the combustor body (heavy) needs to be enlarged, and the manufacturing cost is also increased.

2. Because of the partial gas premixing device, the tempering phenomenon occurs when the gas pressure is unstable.

3. The requirement on the size of a hearth is high when the boiler is reconstructed, and the hearth cannot be enlarged by an old boiler. Many boilers which are just used for two or three years are forced to be changed, and the enterprise burden is increased.

4. The newly-built boiler requires enlarging a hearth and increases the manufacturing cost of the boiler.

5. Under the condition that NOX is less than or equal to 30mg/m3, an FGR (flue gas recirculation) means is needed for assistance, and the FGR means can generate acidic condensate water to enter a hearth, so that the heat efficiency of the boiler is reduced, a combustor and the hearth are corroded, and the service life of the boiler is reduced;

6. when some users are found to close the FGR valve, the FGR valve can be stolen and released;

7. the condensed water generated by FGR in extremely cold areas can be rapidly condensed into ice blocks to block the inlet of a fan, so that the phenomenon of furnace shutdown is caused. Or partial ice blocks are sucked into the fan to damage the impeller of the fan, so that the performance of the equipment is unstable, the maintenance rate is increased, and the service life of the equipment is shortened.

In view of the combination of the two combustion modes, the method has a plurality of defects, and the aim of low nitrogen is achieved mainly by sacrificing energy consumption. Is not a 'low nitrogen, energy-saving' product in the true sense.

Disclosure of Invention

The invention provides a low-nitrogen combustion head with a free diffusion premixed combustion layer, aiming at the defects of the prior art, which reasonably arranges a central pipeline (conveying the first gas), a first annular layer pipeline (conveying the second gas) and a second annular layer pipeline (conveying the first gas), so that the first gas jetted from the central pipe, the second gas jetted from the first annular layer pipe and the first gas output from the second annular layer pipe all pass through the free diffusion premixed combustion layer when finally jetted from the combustion head body, free diffusion and premixing are realized through the air holes in the fuel tank, so that local high temperature points are avoided during combustion, therefore, the generation of low nitrogen oxides is effectively reduced, in other words, the free diffusion premixed combustion layer can intercept mixed gas, the premixing effect is enhanced, the flame is prevented from floating and falling off, and the low nitrogen combustion effect can be achieved. In addition, the invention has a plurality of mutually independent premixing areas, so that when the combustion head part corresponding to one premixing area can not work, the normal work of other parts can not be influenced.

In order to achieve the technical purpose, the invention adopts the following technical scheme:

a low-nitrogen combustion head with a free diffusion premixed combustion layer comprises a combustion head body, wherein the combustion head body comprises a central pipeline, a plurality of first annular layer pipelines, a plurality of second annular layer pipelines and a free diffusion premixed combustion layer; wherein:

the central pipeline is arranged along the central line of the combustion head body;

each first annular layer pipeline in the plurality of first annular layer pipelines is arranged on the first annular layer at the periphery of the central pipeline; each second annular layer pipeline in the plurality of second annular layer pipelines is arranged on the second annular layer at the periphery of the central pipeline;

each first annular layer of pipelines is externally tangent to the central pipeline, and each first annular layer of pipelines is externally tangent to one second annular layer of pipelines; the circle center of each first annular layer pipeline, the circle center of a second annular layer pipeline externally tangent to the first annular layer pipeline and the circle center of the central pipeline are collinear;

an independent premixing area is formed between the outer walls of the first annular layer pipeline and the second annular layer pipeline with collinear circle centers and the outer walls of the adjacent first annular layer pipeline and the second annular layer pipeline with collinear circle centers;

The central pipeline, the first annular layer pipeline and the second annular layer pipeline are provided with injection holes capable of injecting to the premixing area;

the free diffusion premixed combustion layer is provided with a plurality of disordered air holes and is arranged in an annular shape as a whole; the inner ring of the free diffusion premixing combustion layer can be circumscribed with each second ring layer pipe, matched cone-like blocks are arranged at positions corresponding to the premixing area, and two sides of each cone-like block are attached to the side wall of the premixing area.

Furthermore, the free diffusion premixed combustion layer is formed by splicing a plurality of premixed filling blocks, and each premixed filling block comprises an inner ring sector, an outer ring sector and a cone-like block body positioned between the inner ring sector and the outer ring sector;

r1 is the inner diameter of the first ring layer conduit when the spacing D between the inner ring sector relative to the outer wall surface of the central conduit is <1/4R 1; the two side parts of the cone-like block body are respectively provided with a first embedded surface at the part attached to the first annular layer pipeline and a second embedded surface at the part attached to the second annular layer pipeline; the central pipeline is provided with a first hole injection area at the position adjacent to the inner ring sector; the first annular layer pipeline is provided with a second hole injection area at the part attached to the first embedded surface; the second annular layer pipeline is provided with a third hole injection area at the part attached to the second embedded surface; the first gas jetted from the first hole jet area, the second gas jetted from the second hole jet area and the third gas jetted from the third hole jet area can flow towards the outer ring sector of the premixing filling block through the disordered air holes of the premixing filling block and are premixed in the conical block body of the premixing filling block until the mixed gas reaching the outer ring sector can be combusted;

When the distance D between the inner ring sector and the outer wall surface of the central pipeline meets 1/4R 1 and D < R1, the first embedding surfaces are arranged at the parts, attached to the first annular layer pipeline, of the two side parts of the cone-like block body, and the second embedding surfaces are arranged at the parts, attached to the second annular layer pipeline, of the two side parts of the cone-like block body; the central pipeline is provided with a hole injection area a at two sides of the tangent position of each first annular layer pipeline; each first annular layer pipeline is provided with a hole injection area b at a corresponding position; the second annular layer pipeline is provided with a third hole injection area at the part attached to the second embedded surface; the first gas jetted from the hole jet area a can collide with the second gas jetted from the hole jet area b for premixing to form a primary mixed gas capable of flowing towards the premixing filling block; the primary mixed gas flowing into the premixing filling block can be freely diffused and mixed with the third gas jetted from the third hole jet area in the premixing filling block and finally combusted in the outer ring sector of the free diffusion premixing combustion layer;

when the distance between the sector of the inner ring and the outer wall surface of the central pipeline satisfies R1 ≤ D <1/4R2+ R1, R2 is the inner diameter of the second annular layer pipeline; two side parts of the similar conical block body can only be embedded with the adjacent second ring layer pipeline, and second embedding surfaces are arranged at the two side parts of the similar conical block body and the parts attached to the second ring layer pipeline; the central pipeline is provided with a hole injection area a at two sides of the tangent position of each first annular layer pipeline; each first annular layer pipeline is provided with a hole injection area b at a corresponding position; the second annular layer pipeline is provided with a third hole injection area at the part attached to the second embedded surface; the first gas jetted from the hole jet area a can collide with the second gas jetted from the hole jet area b for premixing to form a primary mixed gas capable of flowing towards the surface of the premixed filling block; the primary mixed gas flowing into the premixing filling block can be freely diffused and mixed with the third gas jetted from the third hole jet area in the premixing filling block and finally combusted in the outer ring sector of the free diffusion premixing combustion layer;

When the distance D between the inner ring sector and the outer wall surface of the central pipeline is not less than 1/4R2+ R1, the two side parts of the cone-like block body can only be embedded with the adjacent second ring-layer pipeline, and the two side parts of the cone-like block body are provided with second embedding surfaces at the parts attached with the second ring-layer pipeline; the central pipeline is provided with a porous spraying area a at both sides of the tangent position of each first annular layer pipeline; each first annular layer pipeline is provided with a hole injection area b at a corresponding position; hole injection areas c are arranged on two sides of each second annular layer pipeline at the position tangent to the first annular layer pipeline; the hole injection area a, the hole injection area b and the hole injection area c are provided with a plurality of injection holes; the first gas jetted from the hole jet area a can collide with the second gas jetted from the hole jet area b for premixing to form a primary mixed gas capable of flowing towards the surface of the premixed filling block; the primary mixed gas flowing towards the surface of the premixing filling block can collide with the third gas jetted from the hole jetting area c for premixing to form secondary mixed gas capable of continuously flowing towards the free diffusion premixing combustion layer; the secondary mixed gas can be freely diffused and mixed in each air vent of the free diffusion premixed combustion layer and finally combusted in the outer ring sector of the free diffusion premixed combustion layer.

Further, when the distance D between the inner ring sector and the outer wall surface of the central pipeline is larger than or equal to 1/4R2+ R1, the first annular layer pipeline and/or the second annular layer pipeline are cylindrical pipes or adopt spring-type wound pipelines or S-shaped pipes or non-font pipelines; when the first annular layer pipeline and/or the second annular layer pipeline are non-character-shaped pipelines, each branch pipe of the non-character-shaped pipelines is provided with an injection hole.

Further, when the distance D between the sector of the inner ring and the outer wall surface of the central pipe is larger than or equal to 1/4R2+ R1, the opening angle of the injection holes of the first ring layer pipe and/or the second ring layer pipe is 45 degrees inclined towards the central pipe; and the aperture of the jet hole is between 1mm and 6 mm.

Further, the cross-sectional shape of the central pipeline, the first annular layer pipeline and/or the second annular layer pipeline is circular, oval or polygonal.

Further, the injection hole is a tapered hole with gradually changed aperture.

The invention also aims to provide a low-nitrogen combustion head with a free diffusion premixed combustion layer, which comprises a combustion head body, wherein the combustion head body comprises a central pipeline, a plurality of first annular layer pipelines, a plurality of second annular layer pipelines and a free diffusion premixed combustion layer; wherein:

each first annular layer pipeline in the plurality of first annular layer pipelines is arranged on a first annular layer at the periphery of the central pipeline; each second annular layer pipeline in the plurality of second annular layer pipelines is arranged on a second annular layer at the periphery of the central pipeline;

the free diffusion premixed combustion layer is an integral component which is provided with a plurality of disordered air holes and is arranged in an annular shape as a whole; the inner ring of the free diffusion premixed combustion layer is a smooth circular surface and can be externally tangent to each second ring layer pipeline;

the central pipeline is provided with a hole injection area a at two sides of the tangent position of each first annular layer pipeline; each first annular layer pipeline is provided with a hole injection area b at a corresponding position; hole injection areas c are arranged on two sides of each second annular layer pipeline at the position tangent to the first annular layer pipeline; the hole injection area a, the hole injection area b and the hole injection area c are provided with a plurality of injection holes;

The first gas jetted from the hole jet area a can collide with the second gas jetted from the hole jet area b for premixing to form a primary mixed gas which can flow towards the inner ring of the free diffusion premixed combustion layer; the primary mixed gas flowing towards the inner ring of the free diffusion premixed combustion layer can collide with the third gas jetted from the hole jetting area c for premixing to form a secondary mixed gas capable of continuously flowing towards the inner ring of the free diffusion premixed combustion layer; the secondary mixed gas can be freely diffused through the air holes of the free diffusion premixed combustion layer and finally combusted on the surface layer of the free diffusion premixed combustion layer.

Further, the free diffusion premixed combustion layer is an annular component made of porous foam ceramic materials or refractory metal materials in an integrated mode.

Still another technical object of the present invention is to provide a combustion apparatus including the low-nitrogen combustion head with a free-diffusion premixed combustion layer, which includes a blower, a gas pipe, an adapter and a combustion head body; the air blower is characterized in that the adapter comprises a first gas adapter tube, a second gas adapter tube and an air adapter tube which are coaxially arranged, and the center line of the adapter and the center line of the air outlet of the air blower are arranged in a collinear manner;

The first gas transfer pipe is arranged along the middle position of the adapter, an inlet of the first gas transfer pipe is arranged on the side wall and communicated with an outlet of the gas pipe, and an outlet of the first gas transfer pipe is butted with a central pipeline of the combustion head body; the air adapter is an annular pipeline and is arranged between the first fuel gas adapter and the second fuel gas adapter, one end of the air adapter is communicated with an air outlet of the air blower, and the other end of the air adapter is butted with the first annular layer of the combustion head body; the second fuel gas adapter is annularly arranged and is positioned on the outer side of the air adapter, an inlet of the second fuel gas adapter is formed in the side wall, the second fuel gas adapter is communicated with the fuel gas pipe through a branch pipe, and the other end of the second fuel gas adapter is butted with a second annular layer of the combustion head body.

According to the technical scheme, compared with the prior art, the invention has the following advantages:

1. according to the invention, the first annular layer pipeline and the second annular layer pipeline are arranged on the periphery of the central pipeline, so that the combustion head body can form a plurality of mutually independent premixing areas on the periphery of the central pipeline along the radial direction, and the normal work of other areas can not be influenced if one premixing area can not work normally due to faults in the combustion process.

2. In the invention, the free diffusion premixed combustion layer is arranged on the outer side of the second annular layer pipeline, so that the first gas jetted from the central pipeline, the second gas jetted from the first annular layer pipeline and the first gas output from the second annular layer pipeline pass through the free diffusion premixed combustion layer when finally jetted from the combustion head body, and the free diffusion premixed combustion layer realizes the mutual free diffusion premixed through the air holes in the free diffusion premixed combustion layer, thereby avoiding the generation of local high-temperature points during combustion, effectively reducing the generation of low nitrogen oxides.

3. According to the invention, free diffusion premixed combustion layers with different thicknesses can be arranged according to requirements. When the free diffusion premixed combustion layer is thin and a large enough vacant area is arranged in the premixed area, the gas entering the free diffusion premixed combustion layer can be premixed in a collision mixing mode, specifically, hole injection areas (which can be symmetrical or asymmetrical) are arranged on two sides of the tangent positions of the first annular layer pipeline and the central pipeline, wherein the central pipeline is provided with a hole injection area a, the first annular layer pipeline is provided with a hole injection area b, and the gas sprayed by each injection hole of the hole injection area a can be in strong collision with the gas sprayed by each injection hole of the hole injection area b, so that the gas is fully and uniformly premixed, and primary mixed gas capable of flowing towards the premixed filler is formed; the primary mixed gas is fully and uniformly premixed through the strong collision of gas sprayed by the hole spraying areas c arranged on the two sides of the tangent position of the first annular layer pipeline and the second annular layer pipeline through the second annular layer pipeline, so that the secondary mixed gas which can still flow towards the free diffusion premixed combustion layer is formed.

Or a premixing area is formed between the outer walls of the first annular layer pipeline and the second annular layer pipeline with collinear circle centers and the other adjacent group of first annular layer pipeline and second annular layer pipeline with collinear circle centers; and a premixing filling block is arranged in the premixing area, and through disordered air holes in the premixing filling block, the first gas jetted from the first hole jet area, the second gas jetted from the second hole jet area and the third gas jetted from the third hole jet area are fully mixed and finally flow to the outer ring sector of the premixing filling block.

Therefore, after the secondary mixed gas is ignited by the ignition ring arranged at the root part of the combustion head body, the secondary mixed gas can be combusted at the position close to the surface of the outer ring sector of the free diffusion premixed combustion layer.

Drawings

FIG. 1 is a schematic structural diagram of a fully premixed low-nitrogen combustion device in the prior art;

FIG. 2 is a schematic diagram of a low-nitrogen combustion device with a free diffusion premixed combustion layer according to the present invention;

FIG. 3 is a first schematic view of the burner head of FIG. 2 according to the present invention;

FIG. 4 is an enlarged schematic view of the pre-mix pad a of FIG. 3;

FIG. 5 is a schematic view of a second embodiment of the burner head of FIG. 2 according to the present invention;

FIG. 6 is an enlarged schematic view of section A of FIG. 5 (which illustrates impingement mixing between the gas streams exiting the respective stages of the pipeline);

FIG. 7 is an enlarged schematic view of the pre-mix pad b of FIG. 5;

FIG. 8 is a schematic view (circular) of the first or second annular layer of tubing of FIG. 5;

FIG. 9 is a second schematic configuration (S-shape) of the first or second annular layer of tubing of FIG. 5;

FIG. 10 is a third schematic view (not in the shape of a letter) of the first or second annular duct of FIG. 5;

FIG. 11 is a schematic view of a third construction of the burner head of the present invention;

FIG. 12 is an enlarged view of portion B of FIG. 11 (which illustrates the impingement mixing of the gas streams exiting the various stages of the pipeline);

FIG. 13 is a schematic perspective view of the free diffusion premixed combustion layer of FIG. 11 according to the present invention;

in FIGS. 1-13: 1. a blower; 2. a gas pipe; 3. an adapter; 31-a first gas adapter tube; 32-a second gas transfer tube; 33-air connection pipe; 4-1, a burner body; 4-2, a central pipeline; 4-2-1, orifice jet zone a; 4-3, a first annular layer pipeline; 4-3-1, a hole injection zone b; 4-4, a second annular layer pipeline; 4-4-1, orifice jet zone c; 4-5, a pre-mixed filling block a; 4-5-1, outer ring sector; 4-5-2, inner ring sector; 4-5-3, a first chimeric surface; 4-5-4, a second chimeric surface; 4-6, a pre-mixing filling block b; 4-6-1, the outer ring sector of the premix filling block b; 4-6-2, a conical insert; 4-6-3, left side chimeric surface; 4-6-4, right side chimeric surface; 4-7, primary mixed gas; 4-8, secondary mixed gas; 41-branch pipe; 42-main tube.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. The relative arrangement of the components and steps, expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.

Spatially relative terms, such as "above … …," "above … …," "above … … surface," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial relationship to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, devices described as "above" or "on" other devices or configurations would then be oriented "below" or "under" the other devices or configurations. Thus, the exemplary term "above … …" can include both an orientation of "above … …" and "below … …". The device may also be oriented in other different ways (rotated 90 degrees or at other orientations).

Example 1

As shown in fig. 2-4, the low-nitrogen burner with the free diffusion premixed combustion layer according to the present invention comprises a burner body, wherein the burner body is provided with a central pipe, a plurality of first annular pipes, a plurality of second annular pipes, and a free diffusion premixed combustion layer; wherein:

the central pipeline, the first annular layer pipeline and the second annular layer pipeline are all provided with jet holes capable of jetting to the premixing area;

the free diffusion premixed combustion layer is provided with a plurality of disordered air holes and is arranged in an annular shape as a whole; can be an integral component or a spliced annular component; the inner ring of the free diffusion premixing combustion layer can be circumscribed with each second ring layer pipe, matched cone-like blocks are arranged at positions corresponding to the premixing area, and two sides of each cone-like block are attached to the inner wall of the premixing area.

In this embodiment, the free diffusion premixed combustion layer is formed by splicing a plurality of premixed filling blocks, and each premixed filling block comprises an inner ring sector, an outer ring sector and a cone-like block body located between the inner ring sector and the outer ring sector. Wherein: the inner ring sector is jointed with the central pipeline (in fact, the distance D between the inner ring sector and the outer wall surface of the central pipeline is only required to be smaller than 1/4R1, meanwhile, the inner ring sector cannot be completely jointed with the outer wall of the central pipeline, enough clearance needs to be reserved, and gas can be conveniently sprayed out of the central pipeline and injected into the premixing and filling block); the first embedded surface is attached to the first annular layer pipeline, and the second embedded surface is attached to the second annular layer pipeline;

the central pipeline is provided with a first hole injection area at the part attached to the inner ring sector; the first annular layer pipeline is provided with a second hole injection area at the part attached to the first embedded surface; the second annular layer pipeline is provided with a third hole injection area at the part attached to the second embedded surface; the first hole injection area, the second hole injection area and the third hole injection area are all provided with a plurality of injection holes.

The first gas jetted from the first hole jet area, the second gas jetted from the second hole jet area and the third gas jetted from the third hole jet area can flow towards the outer ring sector of the premixing filling block through the disordered air holes of the premixing filling block and are premixed in the conical block-like body of the premixing filling block until the mixed gas reaching the outer ring sector can be combusted.

Therefore, the low-nitrogen combustion head of the embodiment basically adopts a free diffusion mode to realize the mixing of air and fuel gas.

Example 2

As shown in fig. 2 and 5-10, the gas molecule collision diffusion premixing low-nitrogen combustion head comprises a combustion head body, wherein the combustion head body is provided with a central pipeline, a plurality of first annular layer pipelines, a plurality of second annular layer pipelines and a free diffusion premixing combustion layer; wherein:

A premixing area which is similar to a cone and is independently arranged is formed between the first annular layer pipeline and the second annular layer pipeline with collinear circle centers and the outer walls of the adjacent first annular layer pipeline and the second annular layer pipeline with collinear circle centers and the outer walls of the concentric pipelines;

the free diffusion premixed combustion layer is provided with a plurality of disordered air holes and is arranged in an annular shape as a whole; the inner ring of the free diffusion premixing combustion layer can be circumscribed with each second ring layer pipe, matched cone-like blocks are arranged at positions corresponding to the premixing area, and two sides of each cone-like block are attached to the inner wall of the premixing area. In this embodiment, the free diffusion premixed combustion layer is formed by splicing a plurality of premixed filling blocks, and each premixed filling block comprises an inner ring sector, an outer ring sector and a cone-like block body located between the inner ring sector and the outer ring sector.

The premixing area is provided with a cone-like block; the similar conical block can intercept mixed gas, enhance the premixing effect, prevent flame from floating and dropping fire, and achieve the low-nitrogen combustion effect.

In the embodiment, the distance D between the inner ring sector and the outer wall surface of the central pipeline is not less than 1/4R2+ R1, R2 is the inner diameter of the second annular layer pipeline, and R1 is the inner diameter of the first annular layer pipeline; therefore, in the embodiment, the central pipeline is provided with the hole injection areas a on two sides of the tangent position of each first annular layer pipeline; each first annular layer pipeline is provided with a hole injection area b at a corresponding position; hole injection areas c are arranged on two sides of each second annular layer pipeline at the position tangent to the first annular layer pipeline; the hole injection area a, the hole injection area b and the hole injection area c are all provided with a plurality of injection holes. As can be seen, in the present embodiment, the gas ejected from each ejection hole of the hole ejection area a can strongly collide with the gas ejected from each ejection hole of the hole ejection area b, and is sufficiently and uniformly premixed, so that the primary mixed gas that can flow toward the premixed packing is formed; the primary mixed gas is fully and uniformly premixed through the strong clash of the gas sprayed by each spray hole of the hole spray areas c arranged on the two sides of the tangent position of the first annular layer pipeline and the second annular layer pipeline by the second annular layer pipeline, and the secondary mixed gas which can still flow towards the free diffusion premixed combustion layer is formed.

In the invention, the central pipeline is an air micropore jet main pipeline (made of stainless steel high-temperature resistant pipe), wherein air is conveyed. The jet orifice of the orifice jet zone a is arranged at the position close to the root of the first annular layer pipeline and can impact and jet towards the root of the first annular layer pipeline. Therefore, the air flow columns flowing out of the hole injection area a can be broken up, and the air flow columns are quickly diffused into more dispersed air molecules, so that the upward multi-directional capture of the gas molecules is facilitated. The gas can not be directly blown against the middle, so that the flow rate of the mixed gas can be controlled, and the phenomenon that flame is blown off due to false drifting caused by too high flow rate is prevented.

The first annular layer pipeline is a gas micropore injection pipeline (made of a stainless steel high-temperature resistant pipe). The angle of the air outlet is 45 degrees downwards, so that the fuel gas is sprayed downwards and forms strong collision with the air from the central pipeline, the fuel gas can be diffused in multiple directions and dispersed into smaller fuel gas molecules, and the smaller fuel gas molecules can be conveniently captured by the air molecules. In addition, the concentration difference of the fuel can also generate driving force to diffuse to the periphery, so that the premixing effect with air is further enhanced, and the first premixing is formed.

The second annular layer pipeline is a secondary air injection pipeline (made of stainless steel high-temperature resistant pipes), and the opening angle is 45 degrees downwards. Thus, the secondary air is injected downwards to form strong collision with the primary premixed gas and diffuse in multiple directions. At this time, the gas molecules are basically captured by the air molecules, and the effect of complete premixing is achieved.

Therefore, the combustion head body can form a plurality of mutually independent premixing areas similar to cones (the pipe diameter of the first annular layer pipe is larger than that of the second annular layer pipe), namely premixing areas for placing the similar cone blocks, on the periphery of the central pipe along the radial direction, and the first gas jetted from the hole jetting area a can collide with the second gas jetted from the hole jetting area b for premixing to form primary mixed gas capable of flowing towards the inner circular surface of the similar cone blocks; the primary mixed gas flowing towards the inner circular surface of the cone-like block can collide with the third gas jetted from the hole jetting area c for premixing to form secondary mixed gas capable of continuously flowing towards the inner circular surface of the cone-like block; the secondary mixed gas can be freely diffused in the cone-like block through the disordered air holes. Therefore, in the embodiment, the premixing of the air and the fuel gas is performed by firstly adopting an impinging premixing mode and then adopting a free diffusion premixing mode.

The aperture of the spraying holes of the hole spraying area a, the hole spraying area b and the hole spraying area c is between 1mm and 6 mm.

The first annular layer pipeline and/or the second annular layer pipeline can be a cylindrical pipe as shown in fig. 5, or an S-shaped pipe as shown in fig. 6, or a spring-type wound pipeline or a non-square pipe as shown in fig. 7; when the first annular layer pipeline and/or the second annular layer pipeline are non-square pipelines, gas is input from a main pipe 42 of the non-square pipeline and then is output from an injection hole arranged on each branch pipe 41 of the non-square pipeline. The cross section of the central pipeline, the first annular layer pipeline and/or the second annular layer pipeline is circular, oval or polygonal. The jet hole is a tapered hole with gradually changed aperture. The hole injection zone a, the hole injection zone b and/or the hole injection zone c are micropore injection conical areas with the number of injection holes gradually changed along the length extension direction of the combustion head. The opening angle of the injection holes of the first annular layer pipeline and/or the second annular layer pipeline is 45 degrees inclined towards the central pipeline.

In addition, the central pipe according to the invention can also be used for transporting gas, in which case the first annular pipe is used for transporting air and the second annular pipe is used for transporting gas. In summary, the type of gas transported in the first annulus pipe needs to be inconsistent with the type in the central pipe and the second annulus pipe.

Another technical object of the present invention is to provide a combustion apparatus with the above combustion head, which comprises a blower, a gas pipe, an adapter and a combustion head body; the adapter comprises a first fuel gas adapter pipe, a second fuel gas adapter pipe and an air adapter pipe which are coaxially arranged, and the center line of the adapter and the center line of the air outlet of the air blower are arranged in a collinear manner;

the first gas adapter tube is arranged along the middle position of the adapter, an inlet of the first gas adapter tube is arranged on the side wall and communicated with an outlet of the gas tube, and an outlet of the first gas adapter tube is butted with a central pipeline of the combustion head body; the air connecting pipe is an annular pipeline and is arranged between the first fuel gas connecting pipe and the second fuel gas connecting pipe, one end of the air connecting pipe is communicated with an air outlet of the air blower, and the other end of the air connecting pipe is butted with the first annular layer of the combustion head body; the second gas adapter is annularly arranged and located on the outer side of the air adapter, an inlet of the second gas adapter is formed in the side wall and communicated with the gas pipe through a branch pipe, and the other end of the second gas adapter is butted with the second annular layer of the combustion head body.

According to the technical scheme, the scheme has the following advantages:

1. the technology is mainly characterized in that the existence of the metal barrel which is the biggest potential safety hazard in the original surface combustion device is avoided. The explosion accident in the metal barrel is fundamentally avoided.

2. The molecular clash premixing mode is adopted, the metal barrel pressure overflow mode without a surface combustion device is changed into a mode of premixing filler for overflowing premixed gas, and low-pressure gas can be combusted at the moment. Meanwhile, the problem that the pressure of the natural gas is not high in the boiler transformation project and cannot be transformed is solved, and the backfire accident is avoided.

3. High-pressure fuel gas injection is not needed, and the problem that the diffusion type combustor has higher requirements on the fuel gas pressure is solved.

4. The high-pressure air injection is not needed, a fan with lower power can be configured, and the power consumption is reduced.

5. The flame shape can be adjusted, the newly-built boiler does not need to enlarge a hearth, and the manufacturing cost of the boiler is reduced.

6. No FGR means is needed for assistance, and no low-temperature flue gas backflow exists. The problem of condensate water and low temperature flue gas get into furnace, reduce boiler thermal efficiency is solved, reach energy-conserving purpose.

7. No FGR means is needed for assistance, no condensed water exists, and the problems that acidic condensed water corrodes a combustor and a hearth and the service life of a boiler is shortened are solved.

8. Without the aid of FGR means, there is no smoke circulation duct. The problem of partial user close FGR pipeline valve, steal the arranging secretly is solved.

9. FGR means is not required for assistance, and no condensed water is generated. The problem of blocking due to freezing of the condensate water at the extremely cold temperature is solved. Meanwhile, the problem that the impeller is damaged due to the fact that condensed water ice cubes are mixed into the fan is solved. The maintenance rate is reduced, and the service life of the equipment is prolonged.

10. And (3) uniformly premixing by adopting a molecular formula collision mode. Solves the problems of insufficient premixing, incomplete combustion, high oxygen content and local high temperature point in a diffusion combustion mode.

11. The problem of tempering in a pre-mixing diffusion combustion mode is solved without pre-mixing.

From the above, it can be seen that: the combustion head is not greatly different from the original surface combustion head in the appearance, and the internal premixing mode and the mixed gas overflowing mode are essentially different. The combustion technology provided by the scheme solves various technical pain points of old burners in the current market at one stroke. The large-scale boiler adopts a multi-station arrangement method, the fire arrangement is not interfered with each other, the temperature of the hearth is more uniform, and the thermal efficiency of the boiler is improved. The technology also solves the problem of reducing atmospheric pollutants; the problem that the combustion efficiency is not improved can not be met at the same time. The burner is a real 'low-nitrogen and energy-saving' product.

The fuel and the air are injected through the dense fine pores which are uniformly distributed in a cross way, strong collision is formed during injection, the fuel and the air are quickly diffused and fully premixed, and combustion is uniformly distributed on the surface of the premixing filling block, so that local high-temperature points cannot be formed. The premixing is full, the combustion net rate is higher, the oxygen content can be effectively reduced, and the emission of NOX can be effectively reduced.

Example 3

The invention can select the free diffusion premixed combustion layers with different thicknesses according to different requirements. Different air-gas mixing modes can be formed by free diffusion premixed combustion layers with different thicknesses. Besides the two modes described in the embodiment 1 and the embodiment 2, the method also comprises the following steps:

when the distance D between the inner ring sector and the outer wall surface of the central pipeline meets 1/4R 1 and D < R1, the first embedding surfaces are arranged at the parts, attached to the first annular layer pipeline, of the two side parts of the cone-like block body, and the second embedding surfaces are arranged at the parts, attached to the second annular layer pipeline, of the two side parts of the cone-like block body; the central pipeline is provided with a hole injection area a at two sides of the tangent position of each first annular layer pipeline; each first annular layer pipeline is provided with a hole injection area b at a corresponding position; the second annular layer pipeline is provided with a third hole injection area at the part attached to the second embedded surface; the first gas jetted from the hole jet area a can collide with the second gas jetted from the hole jet area b for premixing to form a primary mixed gas capable of flowing towards the premixing filling block; the primary mixture flowing into the premix fill is allowed to diffuse freely in the premix fill with the tertiary gas injected from the third port injection zone and eventually combust in the outer ring sector of the free diffusion premix combustion zone.

When the distance between the inner ring sector and the outer wall surface of the central pipe satisfies that R1 is not less than D <1/4R2+ R1, R2 is the inner diameter of the second ring layer pipe; two side parts of the similar conical block body can only be embedded with the adjacent second annular layer pipeline, and second embedded surfaces are arranged at the parts, attached to the second annular layer pipeline, of the two side parts of the similar conical block body; the central pipeline is provided with a hole injection area a at two sides of the tangent position of each first annular layer pipeline; each first annular layer pipeline is provided with a hole injection area b at a corresponding position; the second annular layer pipeline is provided with a third hole injection area at the part attached to the second embedded surface; the first gas jetted from the hole jet area a can collide with the second gas jetted from the hole jet area b for premixing to form a primary mixed gas capable of flowing towards the surface of the premixed filling block; the primary mixture flowing into the premix fill is allowed to diffuse freely in the premix fill with the tertiary gas injected from the third port injection zone and eventually combust in the outer ring sector of the free diffusion premix combustion zone.

Example 4

As shown in fig. 11 to 13, it differs from example 2 only in that a free diffusion premixed combustion layer of a different structural form is employed. The method comprises the following specific steps:

The free diffusion premixed combustion layer is an integral component which is provided with a plurality of disordered air holes and is integrally arranged in an annular shape, and is preferably an annular component which is integrally made of porous foamed ceramic materials; the inner ring of the free diffusion premixed combustion layer is a smooth annular surface and can be circumscribed with each second annular layer of pipe. It differs from example 2 in that the inner ring of the free diffusion premixed combustion layer does not have a cone-like mass matching the premixing zone. Therefore, when the first gas sprayed from the central pipe, the second gas sprayed from the first annular layer pipe and the third gas sprayed from the second annular layer pipe are premixed in the premixing area, collision premixing is adopted, and the method specifically comprises the following steps: the central pipeline is provided with a hole injection area a at two sides of the tangent position of each first annular layer pipeline; each first annular layer pipeline is provided with a hole injection area b at a corresponding position; hole injection areas c are arranged on two sides of each second annular layer pipeline at the position tangent to the first annular layer pipeline; the hole injection area a, the hole injection area b and the hole injection area c are provided with a plurality of injection holes; the first gas jetted from the hole jet area a can collide with the second gas jetted from the hole jet area b for premixing to form a primary mixed gas which can flow towards the inner ring of the free diffusion premixed combustion layer; the primary mixed gas flowing towards the inner ring of the free diffusion premixed combustion layer can collide with the third gas jetted from the hole jetting area c for premixing to form secondary mixed gas capable of continuously flowing towards the inner ring of the free diffusion premixed combustion layer; the secondary mixed gas can be freely diffused and premixed in the free diffusion premixed combustion layer and finally combusted on the surface layer of the free diffusion premixed combustion layer. The free diffusion premixed combustion layer is an annular component which is made of porous foam ceramic materials integrally or made of refractory metal materials.

It can be seen that the present embodiment is different from the above embodiments in that the thickness of the free diffusion premixed combustion layer is thin, and the most important function is not the free diffusion premixed of the mixed gas therein, but the interception of the mixed gas is to avoid the adhesion of carbide on the free diffusion premixed combustion layer, which causes local blockage and local high temperature.

Claims

1. A low-nitrogen combustion head with a free diffusion premixed combustion layer comprises a combustion head body and is characterized in that,

the combustion head body comprises a central pipeline, a plurality of first annular layer pipelines, a plurality of second annular layer pipelines and a free diffusion premixed combustion layer; wherein:

The combustion head body can form a plurality of mutually independent and uniformly distributed premixing areas along the radial direction on the periphery of the central pipeline through the first annular layer pipeline and the second annular layer pipeline which are arranged on the periphery of the central pipeline;

an independent premixing area is formed between the outer walls of the first annular layer pipeline and the second annular layer pipeline with collinear circle centers and the other adjacent group of first annular layer pipeline and second annular layer pipeline with collinear circle centers;

the free diffusion premixed combustion layer is provided with a plurality of disordered air holes and is arranged in an annular shape as a whole; the inner ring of the free diffusion premixing combustion layer can be circumscribed with each second annular layer pipe, matched similar conical blocks are arranged at positions corresponding to the premixing area, and two sides of each similar conical block are attached to the side wall of the premixing area.

2. The low-nitrogen combustion head with the free-diffusion premixed combustion layer as claimed in claim 1, wherein the free-diffusion premixed combustion layer is formed by splicing a plurality of premixed filling blocks, and each premixed filling block comprises an inner ring sector, an outer ring sector and a cone-like block body positioned between the inner ring sector and the outer ring sector;

R1 is the inner diameter of the first ring layer tube when the separation D between the inner ring sector and the outer wall surface of the center tube is <1/4R 1; the two side parts of the similar conical block body are provided with first embedded surfaces at the positions attached to the first annular layer pipeline and second embedded surfaces at the positions attached to the second annular layer pipeline; the central pipeline is provided with a first hole injection area at the position adjacent to the inner ring sector; the first annular layer pipeline is provided with a second hole injection area at the part attached to the first embedded surface; the second annular layer pipeline is provided with a third hole injection area at the part attached to the second embedded surface; the first hole injection area, the second hole injection area and the third hole injection area are provided with a plurality of injection holes; the first gas jetted from the first hole jet area, the second gas jetted from the second hole jet area and the third gas jetted from the third hole jet area can flow towards the outer ring sector of the premixing filling block through the disordered air holes of the premixing filling block and are premixed in the conical block body of the premixing filling block until the mixed gas reaching the outer ring sector can be combusted;

when the distance D between the inner ring sector and the outer wall surface of the central pipeline meets 1/4R1 and D < R1, the first embedding surfaces are arranged at the parts, attached to the first annular layer pipeline, of the two side parts of the cone-like block body, and the second embedding surfaces are arranged at the parts, attached to the second annular layer pipeline, of the two side parts of the cone-like block body; the central pipeline is provided with a hole injection area a at two sides of the tangent position of each first annular layer pipeline; each first annular layer pipeline is provided with a hole injection area b at a corresponding position; the second annular layer pipeline is provided with a third hole injection area at the part attached to the second embedded surface; the first gas jetted from the hole jet area a can collide with the second gas jetted from the hole jet area b for premixing to form a primary mixed gas capable of flowing towards the premixing filling block; the primary mixed gas flowing into the premixing filling block can be freely diffused and mixed with the third gas jetted from the third hole jet area in the premixing filling block and finally combusted in the outer ring sector of the free diffusion premixing combustion layer;

When the distance between the inner ring sector and the outer wall surface of the central pipe satisfies that R1 is not less than D <1/4R2+ R1, R2 is the inner diameter of the second ring layer pipe; two side parts of the similar conical block body can only be embedded with the adjacent second annular layer pipeline, and second embedded surfaces are arranged at the parts, attached to the second annular layer pipeline, of the two side parts of the similar conical block body; the central pipeline is provided with a hole injection area a at two sides of the tangent position of each first annular layer pipeline; each first annular layer pipeline is provided with a hole injection area b at a corresponding position; the second annular layer pipeline is provided with a third hole injection area at the part attached to the second embedded surface; the first gas jetted from the hole jet area a can collide with the second gas jetted from the hole jet area b for premixing to form a primary mixed gas capable of flowing towards the surface of the premixed filling block; the primary mixed gas flowing into the premixing filling block can be freely diffused and mixed with the third gas jetted from the third hole jet area in the premixing filling block and finally combusted in the outer ring sector of the free diffusion premixing combustion layer;

when the distance D between the inner ring sector and the outer wall surface of the central pipeline is not less than 1/4R2+ R1, the two side parts of the cone-like block body can only be embedded with the adjacent second ring-layer pipeline, and the two side parts of the cone-like block body are provided with second embedding surfaces at the parts attached with the second ring-layer pipeline; the central pipeline is provided with a hole injection area a at two sides of the tangent position of each first annular layer pipeline; each first annular layer pipeline is provided with a hole injection area b at a corresponding position; hole injection areas c are arranged on two sides of each second annular layer pipeline at the position tangent to the first annular layer pipeline; the hole injection area a, the hole injection area b and the hole injection area c are provided with a plurality of injection holes; the first gas jetted from the hole jet area a can collide with the second gas jetted from the hole jet area b for premixing to form a primary mixed gas capable of flowing towards the surface of the premixed filling block; the primary mixed gas flowing towards the surface of the premixing filling block can collide with the third gas jetted from the hole jetting area c for premixing to form secondary mixed gas capable of continuously flowing towards the free diffusion premixing combustion layer; the secondary mixed gas can be freely diffused and mixed in each air vent of the free diffusion premixed combustion layer and finally combusted in the outer ring sector of the free diffusion premixed combustion layer.

3. The low-nitrogen combustion head with the free diffusion premixed combustion layer as claimed in claim 2, wherein when the distance D between the sector of the inner ring and the outer wall surface of the central pipe is greater than or equal to 1/4R2+ R1, the first annular layer pipe and/or the second annular layer pipe is cylindrical pipe or spring type wound pipe or S-shaped pipe or non-square pipe; when the first annular layer pipeline and/or the second annular layer pipeline are non-character-shaped pipelines, each branch pipe of the non-character-shaped pipelines is provided with an injection hole.

4. The low-nitrogen burner head with a free-diffusion premixed combustion layer according to claim 2, wherein when a distance D between an inner ring sector surface and an outer wall surface of the center pipe is equal to or greater than 1/4R2+ R1, an opening angle of the injection holes of the first and/or second annulus pipes is 45 degrees inclined toward the center pipe; and the aperture of the jet hole is between 1mm and 6 mm.

5. The low-nitrogen combustion head with a free-diffusion premixed combustion layer as claimed in claim 2, wherein the central tube, the first annular tube and/or the second annular tube has a tube cross-sectional shape of a circle, an ellipse or a polygon.

6. The low-nitrogen combustion head with a free-diffusion premixed combustion layer according to claim 2, wherein the injection holes are tapered holes with gradually changed hole diameters.

7. A low-nitrogen combustion head with a free diffusion premixed combustion layer comprises a combustion head body, and is characterized in that the combustion head body comprises a central pipeline, a plurality of first annular layer pipelines, a plurality of second annular layer pipelines and a free diffusion premixed combustion layer; wherein:

The free diffusion premixed combustion layer is an integral component which is provided with a plurality of disordered air holes and is arranged in an annular shape on the whole; the inner ring of the free diffusion premixed combustion layer is a smooth circular surface and can be externally tangent to each second ring layer pipeline;

the central pipeline is provided with a porous spraying area a at both sides of the tangent position of each first annular layer pipeline; each first annular layer pipeline is provided with a hole injection area b at a corresponding position; hole injection areas c are arranged on two sides of each second annular layer pipeline at the position tangent to the first annular layer pipeline; the hole injection area a, the hole injection area b and the hole injection area c are provided with a plurality of injection holes;

8. The low-nitrogen combustion head with a free diffusion premixed combustion layer according to claim 7, wherein the free diffusion premixed combustion layer is an annular member made of a porous foamed ceramic material integrally or made of a refractory metal material.

9. A combustion apparatus having the low-nitrogen combustion head with a free diffusion premixed combustion layer of claim 1 or 7, comprising a blower, a gas pipe, an adapter, and a combustion head body; the air blower is characterized in that the adapter comprises a first fuel gas adapter pipe, a second fuel gas adapter pipe and an air adapter pipe which are coaxially arranged, and the center line of the adapter and the center line of the air outlet of the air blower are arranged in a collinear manner;

the first gas transfer pipe is arranged along the middle position of the adapter, an inlet of the first gas transfer pipe is arranged on the side wall and communicated with an outlet of the gas pipe, and an outlet of the first gas transfer pipe is butted with a central pipeline of the combustion head body; the air adapter is an annular pipeline and is arranged between the first fuel gas adapter and the second fuel gas adapter, one end of the air adapter is communicated with an air outlet of the air blower, and the other end of the air adapter is butted with the first annular layer of the combustion head body; the second gas adapter is annularly arranged and located on the outer side of the air adapter, an inlet of the second gas adapter is formed in the side wall and communicated with the gas pipe through a branch pipe, and the other end of the second gas adapter is butted with the second annular layer of the combustion head body.