Sectional type combustion low-nitrogen combustion head

Abstract

The utility model discloses a sectional type combustion low-nitrogen combustion head which comprises a fuel gas distributor, an air guide disc, a fuel gas collecting and distributing device and a center combustion head, the fuel gas distributor comprises a cylindrical shell, one end of the cylindrical shell is connected with a combustor flange, and an annular cavity is formed in the other end of the cylindrical shell. The gas nozzle pipe comprises a straight-pipe-shaped nozzle pipe and a bent nozzle pipe, the bent nozzle pipe and the straight-through nozzle pipe are annularly and evenly distributed and connected to the annular cavity, the two kinds of nozzle pipes are arranged at intervals, the outlet end of the bent nozzle pipe abuts against the outer wall of the cylinder of the center burning head, the bent nozzle pipe distributes primary gas to the center of the burning head, and the bent nozzle pipe and the straight-through nozzle pipe are evenly distributed and connected to the annular cavity. The straight-pipe-shaped nozzle pipe distributes secondary fuel gas to the middle rear portion of the combustion chamber. Combustion is effectively divided into two stages, the initial stage combustion effect of oxygen-enriched lean combustion and nitrogen reduction is fully played, excessive excess air in the initial stage is consumed through secondary-stage flue gas internal circulation combustion, and the problem that combustion is unstable under the lower nitrogen oxide index emission requirement of most flue gas internal circulation combustors is solved.

Description

Technical Field

[0001] The utility model belongs to the technical field of burners and their related air-gas-flue gas mixing devices, and particularly relates to a low-nitrogen burner head for segmented combustion. The utility model relates to an associated industrial burner, and the types include burner heads installed on combustion chambers, with natural gas as the fuel, and are used in systems without external flue gas circulation. Background Art

[0002] As is well known, nitrogen oxides (NOx) are toxic and harmful gases, and among them, thermal nitrogen oxides are mainly generated during the combustion process. Its characteristic is that as the temperature of the flame and the combustion area increases, the emission of the pollutant nitrogen oxides also increases exponentially. How to control and reduce the flame temperature of combustion has become the main technical means to reduce thermal nitrogen oxides.

[0003] The flue gas circulation technology is a low-nitrogen combustion technology and is widely used in boiler systems. The flue gas circulation technology utilizes the flue gas generated by combustion, the main components of which are carbon dioxide, water vapor, and nitrogen. Through a circulation method, the non-combustible flue gas is transported back into the combustion area again, so that during the chemical reaction of combustion, the combustible and the oxidant are diluted by the flue gas and then burned, thereby reducing the intensity of the combustion reaction, lowering the flame temperature, and at the same time causing the temperature of the combustion area to also drop, effectively weakening the conditions for oxygen and nitrogen to generate thermal nitrogen oxides, and thus reducing the generation of nitrogen oxides.

[0004] The flue gas circulation technology is basically divided into two types: external flue gas circulation and internal flue gas circulation. External flue gas circulation is to extract a part of the flue gas at the flue gas outlet at the tail of the boiler, send the flue gas into the combustion-supporting air, and after mixing with the combustion-supporting air, enter the combustion area together; internal flue gas circulation is to form a swirling airflow inside the boiler combustion chamber, and directly circulate the flue gas inside the combustion chamber into the combustion area. The difference between internal and external flue gas circulation refers to whether the circulation of the flue gas occurs inside or outside the combustion chamber. In many cases, internal and external circulation are used in combination. The internal circulation technology with NOx ≤ 80 mg / m³ is relatively mature, and combined with external circulation, it can reach NOx ≤ 30 mg / m³.

[0005] The widely used models in the market are diffusion burners with additional external flue gas circulation technology to reduce the emissions of nitrogen oxides. The burner head structure of this type of burner is relatively simple and the operation is relatively reliable. Since its working principle is to use a blower to circulate and burn the flue gas, it is necessary to increase the power of the blower or use a flue gas circulation fan, which results in an increase in investment costs.

[0006] In addition, most on-site installed flue gas recirculation pipes are connected to the air inlet side of the burner blower. The flue gas temperature is relatively high, while the combustion-supporting air temperature is relatively low. When the two meet, the water vapor in the flue gas will condense into water when it encounters cold, causing corrosion at the intersection. In severe cases, the condensed water enters the burner, resulting in failures of the flame detector sensing components and ignition elements, posing safety hazards. In addition, the condensed water enters the burner casing, eroding the blower impeller, internal components of the burner, and the casing itself, affecting the service life of the burner.

[0007] For the flue gas internal circulation models used in the market, in order to achieve the effect of reducing nitrogen oxides, it is usually required that the diameter of the boiler combustion chamber be large enough and the recirculation space for internal circulation be sufficient to ensure the internal circulation effect of a sufficient amount of flue gas. Increasing the size of the combustion chamber has caused a significant increase in the cost of the boiler.

[0008] These flue gas recirculation burners use the method of sending flue gas into the combustion area in a cyclic manner. Although the purpose of reducing nitrogen oxides is achieved, in the case of pursuing lower emission targets, it is necessary to increase the flue gas circulation volume, further reducing the intensity of the combustion flame. These practices will cause a decline in combustion stability, prone to combustion surging, unstable flames, and an increase in the failure rate during the operation of the burner.

[0009] It is recorded in the patent document with the patent number DE 3811477 A1 that for a gas burner, the gas is mixed with air at the inlet of the combustion chamber, and the gas enters through some mixing pipes. Among them, the gas is directly sent into the combustion chamber inlet via the mixing gas pipe and its nozzle, and is mixed with the combustion-supporting air and enters the combustion chamber. The outlets of the gas pipes are distributed in different cross-sections in a divergent direction within the burner mixing chamber.

[0010] What is recorded in the patent document DE 195 09 219 is a method and the burner head of the burner. Regarding the simultaneous supply of combustion-supporting air during the combustion of fuel gas, using inert gas to reduce nitrogen oxides, where the fuel gas is in two stages, one stage is superimposed behind the other stage, and is blown into the flame root in the flow direction of the combustion-supporting air. The mixed gas of the combustion-supporting air with a super chemical reaction ratio and the fuel gas in the first stage flows towards the flame. The supplementary fuel gas is added at the second-stage cross-section, where the recycled flue gas is added as an inert gas to the second stage. A part of the combustion gas is injected into the second stage to form a mixed gas with a lower chemical reaction ratio with the recycled flue gas, and the mixing takes place before reaching the flame.

[0011] Patent EP 0 635 676 describes a method for a low-NOx combustion device for liquid fuel or gas fuel. The burner is inserted into the combustion chamber of the boiler. At least one fuel nozzle in the burner flame tube is used to supply fuel and is adjacent to the flame stabilizing disc. In this method, a large amount of gas is sent from the flame stabilizing disc to the inner wall area of the flame tube. The fast air flow flowing through the gap between the flame tube and the flame stabilizing disc will generate a negative pressure at the leading edge of the flame tube. The flue gas generated in the combustion chamber is sent to this negative pressure area through internal circulation. There are multiple guiding sharp corners on the flame tube that penetrate into the negative pressure area.

[0012] Chinese Patent CN112178626B describes an internal circulation low-nitrogen gas burner. The swirler is sleeved at one end of the first gas pipe. The annular gas head is sleeved outside the swirler and is in clearance fit with the swirler. The second gas pipe conveys gas to the annular gas head. The shunt pipe is sleeved outside the annular gas head. The baffle is sleeved outside the shunt pipe and forms a flue gas channel with the shunt pipe. Multiple groups of inner ring gas components are located in the flue gas channel. Multiple groups of outer ring gas components are installed on the periphery of the baffle. The shunt pipe is used to shunt air to form air for mixing with smoke and air for mixed combustion. When the air for mixing with smoke flows through the flue gas channel, a negative pressure is generated at the smoke inlet, thereby sucking in the flue gas in the combustion chamber and participating in combustion again. Due to the method of directly recovering flue gas using vacuum, not only the flue gas channel is omitted, potential safety hazards are eliminated, but also the use cost is reduced.

[0013] Chinese Patent CN107120652 describes a staged gas low-nitrogen burner, which relates to the technical field of burners. The staged gas low-nitrogen burner includes a distributor, a deflector, an ignition electrode, an ignition fuel pipe, and a combustion cylinder. The distributor is used to provide a flow path for gas and air, including a body, multiple gas nozzles, a gas distribution ring, and multiple air distribution pipes. The body is a cylinder with a first interlayer. The gas enters the gas pipe through the body and is ejected from the gas distribution ring. The air flows through the hollow part of the body, the air distribution pipes, and the outside of the distributor to form an air flow path, providing combustion-supporting gas for the gas. The thickness of the distribution ring in CN107120652 is relatively thin, not greater than 4 times the diameter of the gas distribution hole as shown in the figure. It only distributes gas into inner and outer circles and does not have the function of separating air. The deflector in CN107120652 deflects the air introduced by multiple air distribution pipes to form a rotating air flow. The main body is air, and no gas distribution device is provided.

[0014] These known patent methods and structures mentioned above are not sufficient to meet the increasing demand for reducing pollutant emissions from combustion equipment. Especially when the legal requirements for nitrogen oxide emission standards are further reduced, these methods and structures are limited, and there are still problems such as excessive nitrogen oxides or unstable combustion, making it difficult to meet the requirements of environmental protection emission standards.

[0015] The utility model utilizes the concept of staged combustion to control combustion in stages. In the initial stage, the principle of oxygen-rich lean combustion is adopted to control the generation of nitrogen oxides. In the secondary stage, the recirculated flue gas, as well as the flue gas and heat generated in the initial stage of combustion, are used to create a condition for the secondary stage of combustion, where the combustion-supporting air required for the secondary stage of combustion is diluted and preheated, and the fuel is also diluted and preheated. This enables the secondary stage of combustion to spread to a larger space and proceed in a manner similar to flameless combustion. After this diffusion, the more uniform combustion avoids the occurrence of local high temperatures, suppressing the formation of nitrogen oxides and thus achieving overall low-nitrogen combustion.

[0016] What is most important and different about the utility model is that it innovatively provides a hierarchical distribution method for the fuel, effectively dividing the combustion into two stages. That is, it fully exerts the combustion effect of the initial stage of oxygen-rich lean combustion to reduce nitrogen, and at the same time, uses the recirculated flue gas combustion in the secondary stage to consume the excessive excess air in the initial stage. While ensuring low-nitrogen emissions, it avoids the problems of high excess air coefficient and low efficiency in most premixed burners, and solves the problem of unstable combustion that occurs in most flue gas recirculation burners under the requirement of lower nitrogen oxide emission targets. Summary of the Utility Model

[0017] The utility model is developed to solve the above problems, aiming to provide a flue gas recirculation low-nitrogen gas burner that is stable, safe, structurally compact, highly efficient and environmentally friendly.

[0018] A low-nitrogen combustion head with staged combustion includes a gas distributor, an air deflector disc, a gas concentrator, and a central burner head. The gas distributor is cylindrical, including a cylindrical outer shell. One end of the cylindrical outer shell is connected to the burner flange, and a circular cavity is provided inside the other end of the cylindrical outer shell. The air deflector disc is a hollow cone. The outer edge of the air deflector disc of the air deflector disc is connected to the inner edge of the end of the circular cavity facing the combustion chamber. The outer edge of the deflector disc is in the same plane as the inner wall of the front wall of the combustion chamber. The central burner head passes through the central hole of the inner edge of the hollow deflector disc of the air deflector disc and extends into the combustion chamber. One end of the circular cavity is connected to the gas concentrator, and the other end is connected to a plurality of gas nozzle pipes. The gas nozzle pipes include straight nozzle pipes and bent nozzle pipes. The straight nozzle pipes and the bent nozzle pipes are arranged at intervals. The outlet end of the bent nozzle pipe abuts against the cylindrical outer wall of the central burner head, and the straight nozzle pipe extends into the interior of the combustion chamber. Among them, the bent nozzle pipe distributes primary gas towards the center of the combustion head, and the straight nozzle pipe extends into the combustion chamber to distribute secondary gas to the middle and rear parts of the combustion chamber.

[0019] Furthermore, the gas distributor includes a central gas connection pipe and an outer ring gas connection pipe. The inlet ends of the central gas connection pipe and the outer ring gas connection pipe are connected to the main gas pipe. The outlet end of the central gas connection pipe is connected to the central burner head, and the outlet end of the outer ring gas connection pipe is connected to the circular cavity.

[0020] Furthermore, there are multiple outer ring gas connection pipes, which are evenly distributed in a ring and connected to the circular cavity.

[0021] Furthermore, the end face of the circular cavity connected to the gas nozzle pipe is provided with a plurality of evenly distributed circular openings for connecting the gas nozzle pipe to form a gas passage. The internal space enclosed by the connection of the cylindrical outer shell and the air deflector forms a flow passage for combustion-supporting air.

[0022] Furthermore, the bent nozzle pipes and straight-through nozzles are evenly distributed in a ring and connected to the circular cavity. The distribution of the primary gas volume and the secondary gas volume can be adjusted by changing the number of the bent nozzle pipes and the straight-through nozzles.

[0023] Furthermore, the bent nozzle pipes and straight-through nozzles are evenly distributed in a ring and connected to the circular cavity. The distribution of the primary gas volume and the secondary gas volume can be adjusted by changing the sizes of the outlet openings of the bent nozzle pipes and the straight-through nozzles.

[0024] Furthermore, a circular annular gap passage for the flow of combustion-supporting air is formed between the inner edge of the air deflector and the central burner head.

[0025] Furthermore, the central burner head includes a central gas pipe and a sleeve. The sleeve is sleeved outside the central gas pipe. The outlet end of the central gas pipe is provided with gas distribution holes and an air swirler, and a flame stabilizing baffle is arranged at the outlet end. The central gas pipe is connected to the central gas connection pipe of the gas distributor.

[0026] In summary, the beneficial effects of the present utility model are as follows: The present utility model utilizes the concept of staged combustion to control combustion in stages. In the initial stage, the principle of oxygen-rich lean combustion is used to control the generation of nitrogen oxides. In the secondary stage, the internal circulation flue gas, as well as the flue gas and heat generated in the initial stage of combustion, create a condition for the secondary stage of combustion, where the combustion-supporting air required for the secondary stage of combustion is diluted and preheated, and the fuel is also diluted and preheated. This enables the secondary stage of combustion to spread to a larger space and proceed in a manner similar to flameless combustion. After this diffusion, the combustion becomes more uniform, avoiding local high temperatures and suppressing the generation of nitrogen oxides, thereby achieving overall low-nitrogen combustion.

[0027] The utility model innovatively proposes a grading and distribution method for fuel, effectively dividing combustion into two stages. That is, it fully exerts the combustion effect of the initial stage of oxygen-rich lean combustion to reduce nitrogen, and uses the flue gas internal circulation combustion in the secondary stage to consume the excessive excess air in the initial stage. While ensuring low nitrogen emissions, it avoids the problems of high excess air coefficient and low efficiency in most premix burners, and solves the combustion instability problem that occurs in most flue gas internal circulation burners under the requirement of lower nitrogen oxide emission targets. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 FIG. is a schematic structural diagram of a low-nitrogen burner with staged combustion of the present utility model placed in a combustion chamber.

[0029] Figure 2 FIG. is a schematic diagram of the flow directions of fuel gas, combustion-supporting air, and flue gas in the combustion chamber of a low-nitrogen burner with staged combustion of the present utility model.

[0030] Figure 3 FIG. is a schematic structural diagram of a low-nitrogen burner with staged combustion of the present utility model.

[0031] Figure 4 FIG. is a sectional view of the structure of a low-nitrogen burner with staged combustion of the present utility model.

[0032] Reference numerals: 1, combustion chamber; 2, burner; 3, gas distributor; 4, gas collector; 5, air guiding disk; 6, central burner; 11, front wall of the combustion chamber; 12, furnace wall of the combustion chamber; 13, heat medium; 21, burner flange; 31, cylindrical outer shell; 32, annular cavity; 33, straight nozzle tube; 34, bent nozzle tube; 41, intake main pipe; 42, outer ring gas connecting pipe; 43, central gas connecting pipe; 51, outer edge of the guiding disk; 52, inner edge of the guiding disk; 61, central gas pipe; 62, sleeve; 63, swirler; 64, central gas spray hole; 65, flame stabilizing baffle. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] In order to make the technical means, technical features, achieved objectives, and technical effects of the present utility model easy to understand, the following specifically describes the present utility model in combination with embodiments and the accompanying drawings.

[0034] As Figures 1 to 4 shown, it shows the specific principle and specific structure of a low-nitrogen burner with staged combustion of the present utility model.

[0035] As Figure 1 and Figure 3As shown in the figure, a segmented combustion low-nitrogen burner head 2 of the present utility model is installed on the front wall 11 of the combustion chamber 1 of the combustion chamber through a burner flange 21. The outside of the furnace wall 12 of the combustion chamber is a heat medium 13. The outer edge 51 of the air guiding disc 5 of the burner head 2 is in the same plane as the inner wall of the front wall 11 of the combustion chamber, that is, flush with each other. The gas nozzle tube includes a straight nozzle tube 33 and a bent nozzle tube 34. The straight nozzle tube 33, the bent nozzle tube 34 and the central burner head 6 extend into the combustion chamber 1, and the outlet end of the bent nozzle tube 34 abuts against the sleeve 62 of the central burner head 6.

[0036] As Figure 3 and Figure 4As shown in the figure, the present utility model discloses the specific structure of a segmented combustion low-nitrogen burner head. The burner head includes a gas distributor 3, a gas collector 4, an air guide disk 5, and a central burner head 6. Among them, the gas distributor 3 includes a cylindrical outer shell 31. One end of the cylindrical outer shell 31 is connected to the burner flange 21, and the other end is connected to the outer edge 51 of the air guide disk 5 of the air guide disk 5, and the internal space formed constitutes an air flow passage. The central burner head 6 passes through the central hole of the inner edge 52 of the hollow air guide disk of the air guide disk 5. The annular gap formed between the inner edge 52 of the air guide disk and the central burner head 6 is the outlet for air to flow out of the burner, forming a combustion-supporting air flow passage. The cylindrical outer shell 31 of the gas distributor 3 contains a circular cavity 32 at one end facing the combustion chamber. One end of the circular cavity 32 is connected to the outer ring gas connection pipe 42 of the gas collector 4. A plurality of uniformly distributed circular openings are provided on the end surface at the other end of the circular cavity 32 for connecting a straight nozzle pipe 33 and a bent nozzle pipe 34. The outlet end of the bent nozzle pipe 34 surrounds and abuts against the outer wall of the sleeve 62 of the central burner head 6, constituting a primary gas channel. The straight nozzle pipe 33 extends into the interior of the combustion chamber 1, forming a secondary gas channel. The internal space formed by the connection between the cylindrical outer shell 31 and the air guide disk 5 constitutes a combustion-supporting air flow passage. The air guide disk 5 is located at the inner wall position of the front wall of the combustion chamber. Except for the straight nozzle pipe 33, the bent nozzle pipe 34, and the central burner head 6 extending beyond the air guide disk 5 and extending into the interior of the combustion chamber 1, no other components extend into the combustion chamber. The primary gas is ejected from the bent nozzle pipe 34 connected to the gas distributor. This part of the primary gas adheres to the outer wall of the sleeve 62 of the central burner head 6 after flowing out of the nozzle and flows towards the combustion chamber outlet. After the combustion-supporting air flows through the annular gap between the air guide disk 5 and the central burner head 6, it wraps the primary gas and flows towards the combustion chamber outlet together, and is ignited by the central fire when flowing through the end of the central burner head, and forms an initial stage combustion in the central region of the combustion chamber with an oxygen-rich and fuel-lean ratio. The straight nozzle pipe 33 connected to the gas distributor extends beyond the air guide disk 5 and extends into the interior of the combustion chamber 1 by a sufficient space. When the gas in the straight nozzle pipe 33 is ejected, the surrounding is completely the same-flowing flue gas airflow. During the process of flowing towards the outlet of the combustion chamber 1, the gas merges and mixes with the flue gas and the tail gas of the initial stage combustion, and stays and burns in the recirculation zone, forming a secondary stage combustion in the outer region of the combustion chamber. The central burner head 6 provides a stable root flame for the primary combustion, preventing the flame from being blown out under oxygen-rich and fuel-lean conditions. The integration of the primary combustion and the central fire ensures the stability of the initial stage combustion. At the same time, the stable initial stage combustion also provides reliable conditions for the secondary stage combustion.

[0037] As Figure 3 and Figure 4As shown, the air guiding disc 5 is located at the planar position on the inner wall of the front wall of the combustion chamber. Taking this as the boundary, except for the straight nozzle tube 33, the bent nozzle tube 34, and the central burner head 6 extending beyond the air guiding disc 5 and into the combustion chamber 1, no other components extend into the combustion chamber. Starting from the front wall, the entire combustion chamber forms a complete inner circulation reflux space for the flue gas.

[0038] As Figure 3 shown, the air guiding disc 5 is a hollow conical structure. The outer edge 51 of the guiding disc is connected to the end face of the end of the gas distributor 3 with nozzles. The central burner head 6 extends out from the hollow part of the inner edge 52 of the guiding disc. Since the air guiding disc 5 has a conical constricting structure, the air flow with the highest velocity can be obtained. The high-speed air flow sprays into the combustion chamber 1 from the annular gap formed by the inner edge 52 of the guiding disc and the central burner head 6. When the high-speed air flow blows into the combustion chamber, an accompanying eddy current surrounding the air flow will be formed inside the combustion chamber. At the same time, when the air flows at high speed through the conical air guiding disc 5, a negative pressure area will be formed on the back of the guiding disc 5. This part of the negative pressure will guide the eddy current from the outer circle of the combustion chamber to flow in a countercurrent direction to the negative pressure area behind the air guiding disc 5. After reaching the negative pressure area, it will naturally turn and then converge with the high-speed air flow, and flow in the same direction as the combustion-supporting air towards the outlet direction of the combustion chamber 11. In the combustion state, the refluxed eddy current is the flue gas generated by combustion, which constitutes the inner circulation mode of the flue gas.

[0039] As Figure 2, shows a schematic diagram of the flow direction of the gas and combustion-supporting air of the utility model, wherein the combustion-supporting air A enters the combustion head 2, and enters the combustion chamber 11 through the air channel formed by the gas distributor 3 and the air guide plate 5. Due to the conical closing structure of the air guide plate 5, the combustion-supporting air A reaches the highest flow rate when passing through. After the high-flow air flow is blown into the combustion chamber 11, an accompanying vortex D surrounding the air flow will be formed. At the same time, when the high-flow air flow flows through the air guide plate 5, a negative pressure area will be formed on the back of the air guide plate. This part of the negative pressure guides the vortex D to flow from the outer circle of the combustion chamber to the air guide plate 5 in the direction of the countercurrent C1. After reaching the air guide plate, it naturally turns and then merges with the air flow in the direction of the downstream C2, and flows together to the outlet direction of the combustion chamber. In the combustion state, the reflux vortices C1 and C2 are the flue gas generated by the combustion, which constitutes an internal circulation mode of the flue gas. The outer ring gas B2 of gas B enters the gas distributor 3 through the outer ring pipe 42 of the gas collector 4, and enters the combustion chamber 1 through the straight nozzle pipe 33. This part of the secondary gas is located in the middle of the downstream flue gas C2 when it is ejected. The merged secondary gas, flue gas C2 and the initial stage combustion tail gas stay and burn in the vortex area. Except for the countercurrent C1, the remaining part of the combusted flue gas C flows out of the combustion chamber in the downstream direction. The outer ring gas B2 of gas B enters the gas distributor 3 through the outer ring gas connecting pipe 42 of the gas collector 4, and enters the combustion chamber 1 through the bent nozzle pipe 34. This part of the primary gas is attached to the outer wall of the sleeve 62 of the center burner 6 when it is ejected, and is wrapped by the combustion-supporting air A. The secondary gas merged with the air is ignited by the center fire when it flows through the end of the center burner 6 in the process of flowing toward the combustion chamber outlet, and then forms the initial stage of oxygen-rich and lean combustion in the center area of ​​the combustion chamber. The central gas B1 is delivered to the central burner 6 from the central gas pipe of the gas collector 4, and the central flame F provides a stable rooting flame base point for the initial stage of combustion.

[0040] like Figure 4 As shown, the gas distributor 3 is a cylindrical shell with an annular cavity 32 embedded therein. One end of the annular cavity 32 is connected to the outer ring gas pipe 42 of the gas collector 4, and the other end surface has multiple circular openings evenly distributed to connect the straight tube nozzle pipe 33 and the bent nozzle pipe 34. The gas enters from the main gas pipe 41 of the gas collector 4, and then enters the annular cavity of the gas distributor 3 through four outer ring gas connecting pipes 42, and then is distributed to the combustion chamber through the straight tube nozzle pipe 33 and the bent nozzle pipe 34, forming an outer ring gas channel. One end of the cylindrical shell 31 of the gas distributor 3 is connected to the burner flange 21, and the internal space surrounded by the cylindrical shell 31 and the air guide plate 5 constitutes a channel for the circulation of combustion-supporting air.

[0041] like Figure 1 and Figure 3As shown, the outlet of the straight nozzle tube 33 extends beyond the air deflector 5 and into the combustion chamber 1 by a sufficient distance to ensure that when the fuel gas is ejected, the fuel gas flow is located within the downstream flue gas flow of the internal flue gas circulation.

[0042] As Figure 4 shown, the fuel gas distributor 4 includes a central fuel gas connection pipe 43 and an outer ring fuel gas connection pipe 42. The inlet end of the fuel gas distributor 4 is connected to the main fuel gas pipe 41. The outlet end of the central fuel gas connection pipe 43 is connected to the central fuel gas pipe 61 of the central burner 6, and the outlet end of the outer ring fuel gas connection pipe 42 is connected to the fuel gas annular cavity 32 of the fuel gas distributor 3.

[0043] As Figure 4 shown, the central burner 6 includes a central fuel gas pipe 61 and a sleeve 62. The sleeve 62 is sleeved outside the sleeve 62. The outlet end of the central fuel gas pipe 61 is provided with an air swirler 63 and fuel gas spray holes 64, and a flame stabilizing baffle 65 is arranged at the end. The central fuel gas pipe 61 is connected to the outlet end of the central fuel gas connection pipe 43 of the fuel gas distributor.

[0044] The sleeve 62 of the central burner 6 of the present utility model can protect the central flame from being blown out, provide a reliable root flame base point for the entire combustion, and ensure the stability of the overall combustion. When the high-velocity air flow blows out while wrapping the sleeve 62, it can effectively cool the central flame and reduce the nitrogen oxides generated by the central flame.

[0045] The air deflector 5 used in the present utility model is arranged at the position of the inner wall 11 of the front wall of the combustion chamber, providing a flue gas internal circulation burner technology without components such as a flame tube extending into the combustion chamber. Without using components such as a flame tube, the combustion chamber space is utilized to the greatest extent for flue gas circulation. When the combustion chamber diameter is small, effective mixing of flue gas, fuel gas, and air is achieved, the combustion reaction intensity is reduced, the combustion reaction area is expanded, the temperature inside the combustion chamber is balanced, local high temperature is avoided, the generation of nitrogen oxides is reduced, and low nitrogen oxide emissions are achieved.

[0046] At the same time, since components such as a flame tube are not used, the structure of the burner is greatly simplified, and the manufacturing cost is reduced. Without components such as a flame tube exposed to the high-temperature combustion chamber, the high-temperature loss of the burner is eliminated, and the service life of the equipment is extended.

[0047] The technical solution of the present utility model is a low-nitrogen burner with staged combustion, which includes primary combustion mainly occurring in the central area of the combustion chamber and using the principle of oxygen-rich lean combustion and low nitrogen, and secondary combustion mainly occurring in the outer ring area of the combustion chamber and using the excess air containing the primary combustion flue gas remaining from the primary combustion stage to react with the secondary fuel gas mixed with the recirculated flue gas, based on the principle of low nitrogen in flue gas internal circulation.

[0048] The structure of the burner head described in this utility model mainly includes a gas distributor with an annular cavity. Through two types of nozzle pipes, namely bent nozzles and straight-through nozzles, installed on the gas distributor, the gas is distributed into primary gas in the center and secondary gas in the outer ring. There is a central burner head located in the center of the burner head, which plays a role in stabilizing the fire and taking root. It extends into the combustion chamber, and bent nozzles are arranged around the outer wall of the central burner head. After the primary gas flows out of the bent nozzles, it adheres to the outer wall of the sleeve of the central burner head and flows backward along the axial direction of the combustion chamber. Except for a small amount of air inside the sleeve of the central burner head, all the remaining combustion-supporting air enters the combustion chamber through the annular gap between the air guide plate and the central burner head, forming a wrap around the primary gas, and flowing together towards the outlet direction of the combustion chamber. During the flowing process, the air and the primary gas diffuse and mix with each other, and are ignited by the central flame when flowing through the end of the central burner head. In the case of wrapping a large amount of air, rich-oxygen lean-burn primary combustion in the central area of the combustion chamber is quickly achieved.

[0049] At the same time, the straight-through nozzles for the secondary gas are evenly arranged along the outer edge of the air guide plate. The outlet of the straight-through gas nozzles exceeds the air outlet end of the air guide plate and extends into the combustion chamber. There is a space interval with the size of the diameter difference between the inner and outer edges of the air guide plate between the straight-through nozzles for the secondary gas and the central air flow in the axial direction. The gas injection direction is the laminar flow direction same as the air flow. Since the space interval is filled with recirculating flue gas, this part of the secondary gas will not immediately contact the combustion-supporting air after being ejected, so it will not burn immediately. Instead, it diffuses and mixes with the accompanying eddy current formed in the middle and rear sections along with the main air flow, and a combustion reaction occurs when the flow rate is less than or equal to the flame propagation speed. The maximum central combustion power in the initial stage can reach 50% of the load. It can meet the requirement that the gas temperature generated after the combustion of the combustion-supporting air in the initial stage is not lower than the auto-ignition temperature of the gas. Since this part of the gas generated by the initial combustion contains the initial combustion flue gas, the remaining oxygen content has been diluted, and the secondary gas has also been diluted and heated by the recirculating flue gas. The combustion in the secondary stage spreads to a larger space. In an environment where the temperature is above the auto-ignition temperature of the gas, gas molecules and oxygen molecules react whenever they meet, there is no obvious stagnant flame, no local intense combustion occurs, no high-temperature area, the temperature is average, and the generation of nitrogen oxides is inhibited, thus achieving overall low-nitrogen combustion.

Claims

1. A low-nitrogen burner head with staged combustion, characterized in that: The invention comprises a gas distributor, an air guide plate, a gas collector and a center burner, wherein the gas distributor is cylindrical and comprises a cylindrical shell, one end of which is connected to a burner flange, and a circular cavity is arranged in the other end of the cylindrical shell, the air guide plate is a hollow cone, the outer edge of which is connected to the inner edge of the end of the circular cavity facing one end of the combustion chamber, the outer edge of which is in the same plane as the inner wall of the front wall of the combustion chamber, and the center burner is formed from the hollow inner edge of the air guide plate. The core hole extends into the combustion chamber, one end of the annular cavity is connected to the gas distributor, and the other end is connected to a plurality of gas nozzle pipes, the gas nozzle pipes include a straight tube nozzle pipe and a bent nozzle pipe, the straight tube nozzle pipe and the bent nozzle pipe are arranged at intervals, the outlet end of the bent nozzle pipe abuts against the cylindrical outer wall of the center burning head, the straight tube nozzle pipe extends into the combustion chamber, wherein the bent nozzle pipe distributes primary gas to the center of the burning head, and the straight tube nozzle pipe extends into the combustion chamber, thereby distributing secondary gas to the rear part of the combustion chamber.

2. The staged combustion low nitrogen burner according to claim 1, characterized in that: The gas collector includes a central gas pipe and an outer ring gas pipe, the inlet ends of the central gas pipe and the outer ring gas pipe are connected to the gas main pipe, the outlet end of the central gas pipe is connected to the central burner, and the outlet end of the outer ring gas pipe is connected to the annular cavity.

3. The staged combustion low nitrogen burner according to claim 2, characterized in that: The outer ring gas pipes are multiple and evenly distributed in an annular shape and connected to the annular cavity.

4. The staged combustion low nitrogen burner head according to claim 1 or 2, characterized in that: The end surface where the annular cavity is connected to the gas nozzle pipe is provided with a plurality of evenly distributed circular openings for connecting the gas nozzle pipe to form a gas channel. The internal space enclosed by the cylindrical outer shell and the air guide plate forms a circulation channel for combustion-supporting air.

5. The staged combustion low nitrogen burner according to claim 1, characterized in that: The bent nozzle tubes and the straight nozzles are evenly distributed in an annular shape and connected to the annular cavity, and the distribution of the primary gas volume and the secondary gas volume can be adjusted by changing the number of the bent nozzle tubes and the straight nozzles.

6. The staged combustion low nitrogen burner according to claim 1, characterized in that: The bent nozzle tube and the straight nozzle are evenly distributed in an annular shape and connected to the annular cavity, and the distribution of the primary gas volume and the secondary gas volume can be adjusted by changing the sizes of the outlet openings of the bent nozzle tube and the straight nozzle.

7. The staged combustion low nitrogen burner according to claim 1, characterized in that: An annular gap channel for supplying combustion-supporting air is formed between the inner edge of the air guide plate and the central burning head.

8. The staged combustion low nitrogen burner according to claim 1, characterized in that: The central burning head comprises a central gas pipe and a sleeve, wherein the sleeve is sleeved outside the central gas pipe, a gas distribution hole and an air cyclone are arranged at the outlet end of the central gas pipe, a flame stabilizing baffle is arranged at the outlet end, and the central gas pipe is connected to the central gas connecting pipe of the gas collector.

9. The staged combustion low nitrogen burner according to claim 8, characterized in that: The outlet end of the bent nozzle tube abuts against the cylindrical outer wall of the sleeve.

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