Natural gas ammonia-doped combustor with porous structure and operation method

Abstract

The invention belongs to the field of combustors, and particularly relates to a natural gas ammonia-doped combustor with a porous structure and an operation method.The natural gas ammonia-doped combustor comprises an inner barrel and an outer barrel, and the outer barrel is coaxially arranged outside the inner barrel in a sleeving mode; a central pipe and a central ammonia gas pipe are arranged in the inner cylinder, and a flame holder is arranged at the tail end of the inner cylinder; an inner secondary air pipeline and an outer secondary air pipeline which are coaxially sleeved in sequence are arranged in the outer cylinder; a plurality of inner gas pipes comprising inner ammonia gas pipes and inner natural gas pipes are arranged in the inner secondary air pipeline at intervals in the annular direction, and an outer natural gas pipe composed of a plurality of outer natural gas pipes is arranged in the outer secondary air pipeline at intervals in the annular direction. Compared with the prior art, the problems that in the prior art, the ammonia combustion characteristic is poor, and the emission amount of atmospheric pollutant NOx is high are solved, a multi-stage ammonia supply mode is adopted in the scheme, ammonia gas can be conveyed more stably and evenly, the ammonia doping proportion is greatly increased, and therefore the combustion effect is enhanced; and a high-temperature backflow area is formed to facilitate ammonia gas cracking, so that the combustion effect is more efficient and stable.

Description

Technical Field

[0001] The invention belongs to the field of burners, and in particular relates to a natural gas ammonia-mixed burner with a porous structure and an operating method thereof. Background Art

[0002] With the rapid development of the global economy, the demand for fossil fuels is also increasing. As a clean fuel, natural gas has been widely used in many fields and has little impact on the environment and health. However, traditional natural gas combustion produces CO 2 The impact of its large-scale use on climate change still needs to be paid attention to. 2 In recent years, natural gas ammonia combustion technology has become a research field that has received much attention. 3 ) is a substance that does not contain carbon. When mixed with natural gas and burned, it can reduce the CO 2 Emission concentration. Ammonia as a fuel blend is a zero-carbon fuel that can be mass-produced through current wind and solar energy carriers. It has a high volume energy density and is easy to liquefy, store and transport. It is a very promising green energy carrier. However, since ammonia contains nitrogen, studies have shown that blending ammonia as a fuel can easily lead to a sharp increase in nitrogen oxide (NOx) emissions, which significantly affects the low NOx emission properties of natural gas as a clean fuel.

[0003] An analysis of the technical features of the currently publicly reported natural gas-ammonia-blended burners revealed that the burners mainly focus on how to enhance the combustion characteristics of ammonia and how to improve the combustion stability of ammonia. The burners have a tendency to be too strong in the early stage of the mixing organization of ammonia and the supply air, and the generation of NOx during the combustion process is difficult to control and leads to high emissions. As a result, the final emissions may far exceed the national atmospheric pollutant emission standards, thereby limiting the practical application of the technology. At the same time, the ammonia-blended combustion technology may also have problems such as excessive ammonia slip and the inability to increase the blending ratio due to high nitrogen oxide emissions.

[0004] In summary, the current combustion process of natural gas blended with ammonia fuel has problems such as high NOx emissions and low blending ratio, which has hindered the promotion and application of natural gas blended with ammonia fuel technology. Summary of the invention

[0005] The purpose of the present invention is to provide a natural gas ammonia-blended burner with a porous structure and an operating method in order to solve at least one of the above problems, so as to solve the problems of low ammonia blending ratio, high ammonia escape and high NOx emissions in the prior art. The present invention adopts a multi-stage ammonia supply method, which can make the ammonia delivery more stable and uniform, greatly improve the ammonia blending ratio, and thus enhance the combustion effect; a reflux zone is formed at the injection outlet to enhance ammonia cracking, thereby making the combustion effect more efficient and stable and greatly suppressing the generation of NOx.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] The first aspect of the present invention discloses a natural gas-ammonia-doped burner with a porous structure, comprising an inner cylinder and an outer cylinder, wherein the outer cylinder is coaxially sleeved outside the inner cylinder;

[0008] The inner tube is provided with a central tube and a central ammonia tube, and a flame stabilizer is provided at the end of the inner tube; the central tube and the central ammonia tube are coaxially arranged with the inner tube, and the central tube is arranged inside the central ammonia tube, and the central tube is used to arrange an ignition gun or as a fire viewing hole; the end of the central ammonia tube is a porous structure, and ammonia is transported in the central ammonia tube;

[0009] The inner part of the outer cylinder is provided with an inner secondary air duct and an outer secondary air duct which are coaxially sleeved in sequence; a plurality of inner gas pipes are arranged circumferentially at intervals inside the inner secondary air duct, and a plurality of outer natural gas pipes are arranged circumferentially at intervals inside the outer secondary air duct; the ends of the inner gas pipe and the outer natural gas pipe are porous structures; the inner gas pipe includes an inner natural gas pipe and an inner ammonia pipe, which transport natural gas and ammonia respectively, and the outer natural gas pipe transports natural gas;

[0010] A central secondary air channel is formed between the inner tube and the central ammonia pipe. The flame stabilizer is arranged at the end of the central secondary air channel. The central secondary air transported by the central secondary air channel passes through the flame stabilizer to form a flow field structure of the central reflow zone.

[0011] The flame stabilizer is a swirl blade, and the plane where the flame stabilizer is located is perpendicular to the central tube, so that the central secondary air passes through the flame stabilizer to form a central (high temperature) recirculation zone; ammonia passes through the central ammonia pipe located in the center of the flame stabilizer and is ejected from the porous structure at the nozzle to form an ammonia jet; then the ammonia jet can form an ammonia-rich and oxygen-poor atmosphere in front of the flame stabilizer, that is, in the central recirculation zone, which can promote rapid thermal decomposition of ammonia.

[0012] Preferably, an outer cylinder expansion opening is provided at the end of the outer cylinder, and the outer cylinder expansion opening is a fan-ring expansion structure.

[0013] Preferably, the end of the central ammonia pipe is provided with a central ammonia pipe nozzle, the ends of the inner natural gas pipe and the inner ammonia pipe are provided with an inner natural gas pipe nozzle and an inner ammonia pipe nozzle respectively, and the end of the outer natural gas pipe is provided with an outer natural gas pipe nozzle;

[0014] The central ammonia pipe nozzle is provided with a plurality of through holes arranged at intervals to form a porous structure;

[0015] The inner natural gas pipe nozzle and the outer natural gas pipe nozzle are respectively provided with four through holes to form a porous structure.

[0016] Preferably, the porous structures on the inner natural gas pipe nozzle and the outer natural gas pipe nozzle are:

[0017] One of the through holes is a central through hole located at the center of the nozzle, and the remaining three through holes are located at three vertices of an equilateral triangle centered on the central through hole.

[0018] Preferably, a wind shield is provided at the end of the inner ammonia pipe.

[0019] Preferably, the wind shield is V-shaped.

[0020] More preferably, the wind shield is in an obtuse V-shape.

[0021] Preferably, the number of the internal natural gas pipes and the internal ammonia pipes is arranged in a ratio of 2:1.

[0022] Preferably, an internal ammonia pipe is arranged behind every two internal natural gas pipes in the internal combustion gas pipes.

[0023] Preferably, the outer natural gas pipes are arranged at equal intervals along the annular direction.

[0024] Preferably, the head end of the inner secondary air duct is connected to the air inlet of the inner secondary air duct; the head end of the outer secondary air duct is connected to the air inlet of the outer secondary air duct.

[0025] The second aspect of the present invention discloses a method for operating a natural gas-ammonia-doped burner having a porous structure as described above, comprising the following steps:

[0026] Ammonia gas not exceeding 80 vol% of the total amount of ammonia gas enters the burner through the central ammonia gas pipe;

[0027] The secondary air enters the burner through the central secondary air channel, the inner secondary air duct and the outer secondary air duct respectively, and the natural gas and the remaining ammonia enter the burner through the inner natural gas pipe, the inner ammonia pipe and the outer natural gas pipe respectively;

[0028] The central reflux zone is a high-temperature anoxic zone, and ammonia is cracked into nitrogen and hydrogen in the high-temperature anoxic zone.

[0029] Preferably, the burner measures the flow field and flame structure of the natural gas-ammonia combustion flame, and optimizes the combustion parameters of the burner with the ammonia cracking level, the emission level of the harmful gas component NOx and the natural gas combustion state as the target.

[0030] Preferably, by increasing the diameter of the flame stabilizer and / or adjusting the appropriate angle of the rotating blades, the residence time of ammonia is prolonged, thereby enhancing ammonia cracking, improving combustion efficiency, and reducing nitrogen oxide emissions during the combustion process.

[0031] The working principle of the present invention is:

[0032] Ammonia gas, not exceeding 80 vol% of the total amount of ammonia gas in the amount of ammonia gas mixed with combustion gas, is delivered into the combustion chamber of the burner through the central ammonia gas pipe and the central ammonia gas pipe nozzle;

[0033] The secondary air enters the combustion chamber of the burner through the inner secondary air duct, the outer secondary air duct and the central secondary air channel, the natural gas is respectively delivered to the combustion chamber of the burner through the outer natural gas pipe and the inner natural gas pipe through the outer natural gas pipe nozzle and the inner natural gas pipe nozzle, and the remaining ammonia in the ammonia blending amount is delivered to the combustion chamber of the burner through the inner ammonia pipe through the inner ammonia pipe nozzle;

[0034] The rotating airflow generated by the flame stabilizer at the outlet of the central secondary air channel and the natural gas ejected from the inner and outer natural gas pipes work together to form a high-temperature flue gas recirculation area (central recirculation area) in the center of the combustion chamber, which is a high-temperature oxygen-deficient area; ammonia is sent into the high-temperature oxygen-deficient area through the central ammonia pipe, a small part of the ammonia is mixed with the central secondary air and burns to release heat to further increase the temperature of the central recirculation area, while most of the remaining ammonia is cracked into nitrogen and hydrogen under the high-temperature oxygen-deficient conditions in the central recirculation area.

[0035] In addition to the central reflux zone, a V-shaped wind shield is provided at the end of each internal ammonia pipe in the internal combustion gas pipe. A local high-temperature reflux zone will be formed at the rear of the wind shield, that is, the front end of the internal ammonia pipe nozzle. The ammonia sprayed from the internal ammonia pipe nozzle immediately enters the local high-temperature reflux zone, a small part of the ammonia combines with a small amount of oxygen in the local high-temperature reflux zone to burn and release heat, while most of the ammonia will be cracked into nitrogen and hydrogen under the high-temperature and oxygen-deficient conditions in the local high-temperature reflux zone.

[0036] The shortcomings of the current natural gas burners that blend ammonia are specifically manifested as follows: First, the existing technology is difficult to achieve better NOx emission control during the combustion process, and does not utilize the property that most ammonia is cracked into ammonia hydrogen under oxygen-deficient conditions, resulting in poor fuel utilization; second, the blending process is affected by the equipment structure and fuel characteristics, the ammonia blending ratio is low, and it is difficult to achieve the goal of better reducing carbon emissions.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) Ammonia enters the central recirculation zone of the burner from the central ammonia pipe, and in the central recirculation zone, it continuously draws in the flame formed by the combustion of natural gas on the outside, as well as the high-temperature flue gas formed by the combustion flame of ammonia and part of the cracked hydrogen, and can reach a very high temperature. The present invention can make full use of the heat of natural gas combustion at each level, and transfer the heat to the ammonia in the central recirculation zone to cause it to crack. It can also increase the diameter of the flame stabilizer and adopt an appropriate rotating blade angle to allow ammonia to obtain a longer residence time, thereby improving the combustion efficiency and extremely low nitrogen oxide emissions during the combustion process. The input energy of ammonia delivered by the central ammonia pipe should be controlled within the range of 0-80% of the total input energy of ammonia; the total input energy of ammonia should be controlled within the range of 0-50% of the total input energy of the burner.

[0039] (2) The secondary air enters the burner through the central secondary air channel, the inner secondary air duct and the outer secondary air duct, wherein the wind flow of the central secondary air channel enters through the air inlet of the central secondary air duct located at the rear end of the burner, turns to the axial direction through the flange elbow to form an axial airflow, and forms a rotating airflow after flowing through the flame stabilizer close to the burner nozzle. The wind flow of the inner secondary air duct flows through the air inlet of the inner secondary air duct located on the side of the burner, enters the inner secondary air duct vertically through the flange, and then turns to form a direct current airflow along the axial direction and sprays into the combustion chamber, which is mainly used to supply the air required for the combustion of the gas injected by the natural gas nozzle arranged in the inner secondary air duct. The wind flow of the outer secondary air duct flows through the air inlet of the outer secondary air duct located on the side of the burner, enters the outer secondary air duct vertically through the flange, and then turns to form a direct current airflow along the axial direction and sprays into the combustion chamber, which is mainly used to supply the air required for the combustion of the gas injected by the natural gas nozzle arranged in the outer secondary air duct and the cracking combustion of the ammonia injected by the central ammonia nozzle;

[0040] (3) The rotating airflow formed after passing through the flame stabilizer forms a central high-temperature flue gas recirculation zone, which is a high-temperature oxygen-deficient zone; the ammonia fuel introduced into the central ammonia pipe is cracked in this high-temperature oxygen-deficient zone and decomposed into nitrogen and hydrogen. During the entire combustion process, it can enhance the main flame combustion process, improve combustion efficiency, and effectively reduce NOx emissions generated by ammonia combustion. The rotating airflow helps to form a high-temperature flue gas recirculation zone for temperature combustion and enhances airflow mixing. The use of ammonia injection into the recirculation zone can make ammonia burn efficiently and greatly increase the ammonia blending ratio, thereby enhancing the low NOx emission combustion effect.

[0041] (4) The internal combustion gas pipe is arranged in a ring outside the inner tube and is located in the internal secondary air duct. In order to further increase the ammonia blending ratio, the internal combustion gas pipe is composed of four internal ammonia pipes and eight internal natural gas pipes arranged at intervals. A V-shaped wind shield is installed at the nozzle mouth at the end of the internal ammonia pipe to prevent the ammonia flow from mixing with the internal secondary air flow too early, causing unstable ammonia combustion and a large amount of NOx generation. The V-shaped wind shield adopts an obtuse angle, and the high-temperature flue gas recirculation zone formed on the leeward side of the secondary air flow helps ammonia to stay and crack in this area, so that part of the ammonia combustion is converted into hydrogen combustion, making the combustion effect more efficient and stable, and at the same time greatly reducing the amount of NOx generated.

[0042] (5) Compared with traditional burners, the innovative ammonia-doped burner proposed in the present invention has a more compact structure and more advantages in performance. The overall structure of the present invention adopts a split and modular design, which has good adjustability in controlling the ammonia-doped combustion at different stages and in different proportions during the combustion process. The various components of the burner can be replaced and adjusted according to the requirements of later experiments and engineering projects. Through the optimization and adjustment of some key points, a more efficient and stable combustion process can be achieved, the performance and efficiency of the burner can be improved, and NOx emissions can be greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic diagram of the rear view structure of a natural gas-ammonia-doped burner having a porous structure;

[0044] Figure 2 for Figure 1 Schematic diagram of the structural section of the AA section;

[0045] Figure 3 The schematic diagram of the structure of a natural gas ammonia-doped burner having a porous structure;

[0046] Figure 4 The figure is a schematic diagram of the arrangement of the gas nozzle surface of a natural gas-ammonia-doped burner having a porous structure;

[0047] In the figure: 1-external secondary air duct; 2-internal secondary air duct; 3-external natural gas pipe distribution pipe; 4-internal natural gas pipe distribution pipe; 5-central ammonia pipe; 6-central pipe; 7-external tube expansion; 8-inner ammonia pipe air inlet; 9-inner natural gas pipe air inlet; 10-central ammonia pipe air inlet; 11-external natural gas pipe nozzle; 12-inner natural gas pipe nozzle; 13-central ammonia pipe nozzle; 14-flame stabilizer; 15-wind shield; 16-inner secondary air duct air inlet; 17-external secondary air duct air inlet; 18-external natural gas pipe air inlet; 19-inner ammonia pipe nozzle; 20-central secondary air duct air inlet. DETAILED DESCRIPTION

[0048] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0049] Example 1

[0050] A natural gas ammonia-doped burner having a porous structure, such as Figure 1-4 As shown, it comprises an inner cylinder and an outer cylinder, wherein the outer cylinder is coaxially sleeved on the outside of the inner cylinder;

[0051] The inner tube is provided with a central tube 6 and a central ammonia tube 5, and a flame stabilizer 14 is provided at the end of the inner tube; the central tube 6 and the central ammonia tube 5 are coaxially arranged with the inner tube, and the central tube 6 is arranged inside the central ammonia tube 5; the nozzle at the end of the central ammonia tube 5 is a porous structure; the central tube 6 can be arranged with an ignition gun or used as a fire-watching channel, and ammonia is transported in the central ammonia tube 5; a central secondary air channel is formed between the inner tube wall and the outer wall of the central ammonia tube 5, and a small amount of central secondary air passes through the flame stabilizer 14 to form a central reflow zone flow field structure;

[0052] The inner part of the outer cylinder is provided with an inner secondary air duct 1 and an outer secondary air duct 2 which are coaxially sleeved in sequence; a plurality of inner gas pipes are arranged circumferentially at intervals inside the inner secondary air duct 1, and a plurality of outer natural gas pipes are arranged circumferentially at intervals inside the outer secondary air duct 2; the terminal nozzles of the inner gas pipe and the outer natural gas pipe are of a porous structure; the inner gas pipe includes an inner natural gas pipe and an inner ammonia pipe, through which natural gas and ammonia pass respectively, and the outer natural gas pipe 3 passes natural gas;

[0053] The flame stabilizer 14 is arranged between the central ammonia pipe 5 and the internal combustion gas pipe (inner tube), that is, at the end of the central secondary air channel.

[0054] More specifically, in this embodiment:

[0055] A natural gas-ammonia-blended burner with a porous structure comprises: a multi-stage air supply structure, a multi-stage air intake structure, a multi-stage natural gas / ammonia spray holes, a flame stabilizer 14, a wind shield 15 and an outer tube expansion 7; further specifically comprises the following structures: an outer secondary air duct 1, an inner secondary air duct 2, a central pipe 6, an inner secondary air duct air inlet 16, an outer secondary air duct air inlet 17, a wind shield 15, a flame stabilizer 14, an outer tube expansion 7, an outer natural gas pipe distribution pipe 3, an inner natural gas pipe distribution pipe 4, a central ammonia pipe 5, an inner ammonia pipe air inlet 8, an inner natural gas pipe air inlet 9, a central ammonia pipe air inlet 10, an outer natural gas pipe nozzle 11, an inner natural gas pipe nozzle 12, a central ammonia pipe nozzle 13, an outer natural gas pipe air inlet 18, an inner ammonia pipe nozzle 19 and a central secondary air duct air inlet 20.

[0056] Combination Figure 1 and Figure 2The multi-stage air supply structure of the burner includes an inner secondary air duct 2 and an outer secondary air duct 1, a central tube 6 located at the center of the burner (located at the central axis of the burner), and a central ammonia pipe 5 located outside the central tube 6. The central ammonia pipe nozzle 13 at the end of the central ammonia pipe 5 adopts a porous structure;

[0057] The central tube 6, the outer secondary air duct 1 and the inner secondary air duct 2 together constitute the burner body, presenting a three-stage sleeve structure; the outer secondary air duct air inlet 17 is located at the side of the burner and the lower end of the installation position, and is connected to the inlet of the outer secondary air duct 1, and the inner secondary air duct air inlet 16 is located at the side of the burner and the upper end of the installation position, and is connected to the inlet of the inner secondary air duct 2. The outer secondary air duct air inlet 17 and the inner secondary air duct air inlet 16 are both arranged perpendicular to the axis of the burner.

[0058] Reference Figure 1 The central tube 6 is used as an ignition gun feed channel or as a fire viewing window. The central ammonia pipe 5 only introduces ammonia, and utilizes the high temperature and oxygen-deficient conditions of ammonia in the central recirculation zone generated by the flame stabilizer 14 to crack and generate nitrogen and hydrogen, thereby reducing nitrogen oxide emissions. The outer secondary air duct 1 and the inner secondary air duct 2 are used to provide sufficient air to the combustion chamber at the end of the burner for combustion assistance, so that the natural gas burns fully, the combustion process is stable, the nitrogen oxide emissions are reduced, and the combustion efficiency is improved. The outer tube expansion 7 is located at the end of the outer secondary air duct 1 (outer tube) and is a fan-ring expansion structure.

[0059] Reference Figure 2 The multi-stage natural gas / ammonia nozzles include an outer natural gas pipe nozzle 11, an inner natural gas pipe nozzle 12, and a central ammonia pipe nozzle 13, all of which are arranged in a ring shape. The multi-stage arrangement allows the natural gas to be ejected and burned at the combustion site to produce high-temperature flue gas, and a high-temperature oxygen-deficient reflux combustion zone is formed on the combustion surface of the ammonia jet through the reflux action, which strengthens the decomposition of ammonia to produce hydrogen. The oxygen-deficient atmosphere is beneficial to suppressing the generation of NOx products, and the hydrogen produced by the decomposition further strengthens the combustion, making the combustion process more stable.

[0060] The multi-stage air intake structure includes an outer natural gas pipe distribution pipe 3, an inner natural gas pipe distribution pipe 4, a central ammonia pipe 5, an inner ammonia pipe air inlet 8, an inner natural gas pipe air inlet 9, and a central ammonia pipe air inlet 10; Figure 1 , Figure 3 and Figure 4The outer natural gas pipe distribution pipe 3 distributes natural gas to each outer natural gas pipe. They are located in the outer secondary air duct 1 and are thin tubes arranged in a parallel ring shape. There are 16 of them in total. The outer natural gas pipe nozzle 11 at the end has a porous structure. After being connected to the same annular outer natural gas pipe distribution pipe 3 at the starting end, it is led to the outer natural gas pipe air inlet 18 below the burner body; the inner natural gas distribution pipe 4 distributes natural gas to each inner natural gas pipe. They are located in the inner secondary air duct 2 and are thin tubes arranged in a parallel ring shape. The inner natural gas pipe nozzle 12 at the end has a porous structure. After being connected to the same annular inner natural gas pipe distribution pipe 4 at the starting end, it is led out from the inner natural gas pipe air inlet 9 behind the burner body.

[0061] Reference Figure 3 There are 12 internal natural gas pipes in the internal secondary air duct 2, including 4 internal ammonia pipes and 8 internal natural gas pipes; together with the central ammonia pipe 5, a two-stage ammonia spray gun is formed. As a combustion device structure for common reaction, the ammonia ratio is greatly improved compared with other traditional burners. The high-temperature reflux anoxic zone cracking mechanism produced by the mixed combustion of ammonia and natural gas used by the device improves the combustion efficiency of the burner in practical applications, reduces carbon emissions, and greatly reduces harmful combustion pollutants NOx. The reasonable mixing of internal and external secondary air with natural gas and ammonia improves the uniformity of gas combustion, the combustion temperature field is uniform, and the combustion is more sufficient and stable. Ammonia absorbs the heat generated by the high-temperature flame and cracks in the anoxic zone. There is no need for premixing, which improves the safety of the combustion system, enhances the burnout rate of the fuel, and forms a stable combustion process as a whole.

[0062] Reference Figure 3 In the channel between the inner tube and the outlet of the central ammonia pipe 5, i.e. the central secondary air channel, a swirl generator, a radial, annular flame stabilizer 14, is provided, and a wind shield 15 is installed at the outlet of the inner ammonia pipe nozzle in the inner secondary air duct 2, which is an obtuse V-shaped structure and arranged in a ring. After the gas flows through the swirl flame stabilizer 14 and the wind shield 15, a swirl airflow is generated, forming a combustion recirculation zone, so that the flame generates a swirl to achieve the purpose of stable combustion and prolonged residence time. At the same time, the ammonia fuel is cracked into hydrogen and nitrogen in the recirculation zone, which greatly reduces the generation of harmful nitrogen oxides and improves the efficiency and environmental protection of combustion.

[0063] Reference Figure 3, the outer natural gas pipe nozzle 11 is located at the end of the outer secondary air duct 1, and the specific hole arrangement is a central hole, and the outer ring is evenly arranged with three holes (the three endpoints of an equilateral triangle). The inner natural gas pipe nozzle 12 is located at the end of the inner secondary air duct 2. The hole form of the inner natural gas pipe nozzle 12 in the inner natural gas pipe is the same as that of the outer natural gas pipe nozzle 11, while the hole of the inner ammonia pipe nozzle 19 adopts a single hole arrangement. The central ammonia pipe nozzle 13 is located at the end of the central ammonia pipe 5, and the specific hole arrangement is two levels of holes arranged at equal intervals along the circumferential direction. The first level is the inner circle hole, with 6 holes, and the second level is the outer circle hole, with 8 holes.

[0064] By adopting the above scheme, a multi-stage annularly arranged natural gas / ammonia spray hole is set up, so that the natural gas jet is ejected and burned at the combustion site to produce high-temperature flue gas, and a high-temperature oxygen-deficient reflux combustion zone is formed on the combustion surface of the ammonia jet through the reflux action, thereby enhancing the decomposition of ammonia to produce hydrogen. The oxygen-deficient atmosphere is beneficial to inhibiting the formation of NOx products, and the hydrogen produced by decomposition strengthens the combustion, making the combustion process more stable.

[0065] By adopting the above scheme, a flame stabilizer 14 is arranged in the passage between the inner tube and the outlet of the central ammonia pipe 5. The gas flows through the flame stabilizer 14 to generate a swirl flow, forming a combustion recirculation zone, so that the flame generates a swirl to achieve the purpose of stable combustion and prolonged residence time. At the same time, the ammonia fuel is cracked into hydrogen and nitrogen in the recirculation zone, which greatly reduces the generation of harmful nitrogen oxides and improves the efficiency and environmental protection of combustion.

[0066] Based on the above steps, a method for using the porous swirl ammonia-blending burner is also proposed, comprising the following steps:

[0067] (1) Ammonia enters the central high-temperature flue gas recirculation zone of the burner from the central ammonia pipe 5. In the recirculation zone, the high-temperature flue gas formed by the natural gas combustion flames ejected from the inner and outer two-stage natural gas pipes, the ammonia ejected from the inner ammonia pipe, and the partial cracked hydrogen combustion flames will be continuously entrained, reaching a very high temperature. The present invention can make full use of the heat of natural gas combustion at each stage, transfer the heat to the ammonia in the central recirculation zone to crack it, and appropriately increase the diameter of the flame stabilizer 14 and adopt an appropriate rotating blade angle, so that the ammonia has a longer residence time, improves the combustion efficiency, and has extremely low nitrogen oxide emissions during the combustion process; the input energy of the ammonia delivered by the central ammonia pipe 5 should be controlled within the range of 0-80% of the total input energy of ammonia; the total input energy of ammonia should be controlled within the range of 0-50% of the total input energy of the burner;

[0068] (2) The secondary air enters the burner from the central secondary air channel, the inner secondary air duct 2 and the outer secondary air duct 1. The wind flow in the central secondary air channel passes through the central secondary air duct air inlet 20 located at the rear end of the burner, turns to the axial direction through the flange elbow to form an axial airflow, and forms a central reflow zone of the rotating airflow after passing through the flame stabilizer 14 close to the burner nozzle. The wind flow in the inner secondary air duct 2 passes through the inner secondary air duct air inlet 16 located on the side of the burner, vertically enters the inner secondary air duct through the flange, and then turns to form a direct current airflow along the axial direction and is ejected from the inner secondary air nozzle into the combustion chamber, so as to mainly supply the air required for the combustion of natural gas injected by the natural gas gun arranged in the inner secondary air duct. The wind flow in the outer secondary air duct 1 passes through the outer secondary air duct air inlet 17 located on the side of the burner, vertically enters the outer secondary air duct through the flange, and then turns to form a direct current airflow along the axial direction and is ejected from the outer secondary air nozzle into the combustion chamber, so as to mainly supply the air required for the combustion of natural gas injected by the natural gas gun arranged in the outer secondary air duct and the cracking combustion of ammonia injected by the central ammonia gun;

[0069] (3) The ammonia fuel introduced into the central ammonia pipe 5 is cracked in this high-temperature oxygen-deficient reflux area and decomposed into nitrogen and hydrogen. During the entire combustion process, it can enhance the main flame combustion process, improve the combustion efficiency, and effectively reduce NO x The mixed rotating airflow helps to form a high-temperature smoke recirculation zone for the ignition, and fully mixes the airflow. The multi-stage ammonia supply method can make the ammonia delivery more stable and uniform, greatly increase the ammonia blending ratio, and thus enhance the combustion effect;

[0070] (4) The internal gas pipe is arranged in a ring outside the inner tube, and is in the internal secondary air duct 2. In order to further increase the ammonia mixing ratio, the internal gas pipe is composed of four internal ammonia pipes and eight internal natural gas pipes arranged at intervals. The outlet of the internal ammonia pipe is equipped with a rotating wind shield 15 to prevent the ammonia flow from mixing with the internal secondary air flow too early, causing unstable ammonia combustion and a large amount of NOx generation. The V-shaped wind shield 15 adopts an obtuse angle, and the high-temperature flue gas recirculation zone formed on the leeward side of the secondary air flow helps ammonia to stay and crack in this area, so that part of the ammonia combustion is converted into hydrogen combustion, making the combustion effect more efficient and stable, and at the same time greatly reducing the amount of NOx generated;

[0071] In actual application, it can be replaced and adjusted according to later experiments and engineering requirements. Based on the burner in a specific combustion chamber space, the flow field and flame structure of the natural gas mixed with ammonia flame are measured. Under specific conditions, there is always an optimal equivalence ratio, which makes the harmful gas component NOx at a low emission level, the ammonia cracking level reaches the best, and the natural gas and ammonia combustion state is the best. Optimization and adjustment of some key points can achieve a more efficient and stable combustion process and improve the performance and efficiency of the burner.

[0072] The present invention strengthens the combustion process by utilizing the principle that ammonia can be decomposed into nitrogen and hydrogen under high temperature and oxygen-deficient conditions. The blending combustion mechanism under the joint action of the central ammonia pipe nozzle 13 and the inner ammonia pipe nozzle 19 increases the ammonia blending ratio, which not only improves the energy utilization efficiency, but also successfully reduces the emission level of nitrogen oxides.

[0073] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A natural gas ammonia-blended burner having a porous structure, characterized in that: It comprises an inner cylinder and an outer cylinder, wherein the outer cylinder is coaxially sleeved on the outside of the inner cylinder; The inner tube is provided with a central tube (6) and a central ammonia tube (5), and the end of the inner tube is provided with a flame stabilizer (14); the central tube (6) and the central ammonia tube (5) are coaxially arranged with the inner tube, and the central tube (6) is arranged inside the central ammonia tube (5), and the central tube (6) is used to arrange an ignition gun or as a fire viewing hole; the end of the central ammonia tube (5) is a porous structure, and ammonia is transported in the central ammonia tube (5); The outer cylinder is provided with an inner secondary air duct (2) and an outer secondary air duct (1) which are coaxially sleeved in sequence; a plurality of inner gas pipes are arranged circumferentially at intervals inside the inner secondary air duct (2), and a plurality of outer natural gas pipes are arranged circumferentially at intervals inside the outer secondary air duct (1); the ends of the inner gas pipes and the outer natural gas pipes are porous structures; the inner gas pipes include an inner natural gas pipe and an inner ammonia pipe, which transport natural gas and ammonia respectively, and the outer natural gas pipe transports natural gas; A central secondary air channel is formed between the inner cylinder and the central ammonia pipe (5), and the flame stabilizer is arranged at the end of the central secondary air channel. The central secondary air transported by the central secondary air channel passes through the flame stabilizer (14) to form a flow field structure of the central reflow zone.

2. The natural gas-ammonia-doped burner with a porous structure according to claim 1, characterized in that: The end of the outer cylinder is provided with an outer cylinder expansion opening (7), and the outer cylinder expansion opening (7) is a fan-ring expansion structure.

3. The natural gas-ammonia-blended burner with a porous structure according to claim 1, characterized in that: The end of the central ammonia pipe (5) is provided with a central ammonia pipe nozzle (13), the ends of the inner natural gas pipe and the inner ammonia pipe are provided with an inner natural gas pipe nozzle (12) and an inner ammonia pipe nozzle (19) respectively, and the end of the outer natural gas pipe is provided with an outer natural gas pipe nozzle (11); The central ammonia pipe nozzle (13) is provided with a plurality of through holes arranged at intervals to form a porous structure; The inner natural gas pipe nozzle (12) and the outer natural gas pipe nozzle (11) are each provided with four through holes to form a porous structure.

4. The natural gas-ammonia-doped burner with a porous structure according to claim 3, characterized in that: The porous structures on the inner natural gas pipe nozzle (12) and the outer natural gas pipe nozzle (11) are: One of the through holes is a central through hole located at the center of the nozzle, and the remaining three through holes are located at three vertices of an equilateral triangle centered on the central through hole.

5. The natural gas-ammonia-blended burner with a porous structure according to claim 1, characterized in that: A wind shield (15) is provided at the end of the inner ammonia pipe.

6. The natural gas-ammonia-doped burner with a porous structure according to claim 1, characterized in that: The number of the internal natural gas pipes and the internal ammonia pipes is set at a ratio of 2:

1.

7. The natural gas-ammonia-doped burner with a porous structure according to claim 6, characterized in that: An internal ammonia pipe is arranged behind every two internal natural gas pipes in the internal combustion gas pipes.

8. The natural gas-ammonia-blended burner with a porous structure according to claim 1, characterized in that: The head end of the inner secondary air duct (2) is connected to the inner secondary air duct air inlet (16); the head end of the outer secondary air duct (1) is connected to the outer secondary air duct air inlet (17).

9. A method for operating a natural gas-ammonia-doped burner having a porous structure as claimed in any one of claims 1 to 8, characterized in that: The steps include: Ammonia gas not exceeding 80 vol% of the total amount of ammonia gas enters the burner through the central ammonia gas pipe (5); The secondary air enters the burner through the central secondary air channel, the inner secondary air duct (2) and the outer secondary air duct (1), respectively, and the natural gas and the remaining ammonia enter the burner through the inner natural gas pipe, the inner ammonia pipe and the outer natural gas pipe, respectively; The central reflux zone is a high-temperature anoxic zone, and ammonia is cracked into nitrogen and hydrogen in the high-temperature anoxic zone.

10. The method for operating a natural gas-ammonia-doped burner having a porous structure according to claim 9, characterized in that: The burner measures the flow field and flame structure of the natural gas-ammonia combustion flame, optimizes the combustion parameters of the burner with the ammonia cracking level, the emission level of the harmful gas component NOx and the natural gas combustion state as the target.

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