Plasma-assisted low-nox emission ammonia flat flame burner and combustion method

Abstract

The application provides a low-NOx emission ammonia flat flame burner with plasma combustion and a combustion method. The burner comprises a plasma structure, an air sleeve structure, a vortex air inlet structure, a secondary fuel pipe, a burner brick structure, a precombustion chamber and a combustion chamber. Fuel and air are supplied in stages. After ammonia is ignited by plasma, a rotating flame is generated by a plasma cyclone to mix with primary combustion air for combustion. Meanwhile, secondary combustion air is mixed with ammonia in the precombustion chamber to generate a strong rotating flame for stable combustion. Meanwhile, ammonia is directly injected into the flat flame formed by the secondary fuel injection pipe under high-temperature and low-oxygen combustion conditions, so that the combustion and reduction of ammonia are realized, thereby reducing the generation of NOx in the overall ammonia combustion.

Description

Technical Field

[0001] This invention relates to the technical field of low-pollutant emission combustion equipment, specifically a plasma-assisted low-NOx flat-flame ammonia burner and combustion method. Background Technology

[0002] Ammonia, as a carbon-free, clean, and high-calorific-value alternative fuel, has attracted widespread attention and can serve as a chemical energy storage carrier compatible with renewable energy sources. However, ammonia combustion still faces certain technical challenges: due to its high ignition temperature and slow flame propagation rate, ammonia combustion is unstable, resulting in low power output and the generation of large amounts of NOx pollutants during combustion. Currently, to improve ammonia combustion characteristics, hydrocarbon fuels are mixed with ammonia for combustion to increase combustion speed and temperature, but this also leads to increased carbon emissions. Therefore, it is necessary to find new technological means to improve ammonia combustion characteristics, enhance combustion stability, and reduce NOx formation.

[0003] The use of plasma-assisted combustion technology and its supporting combustion systems can significantly reduce fuel consumption and expand the utilization of low-calorific-value fuels. Plasma-assisted ammonia combustion, as an emerging energy technology, has broad application prospects and market potential because it combines plasma technology with ammonia fuel to produce a highly efficient and clean energy source. Plasma-assisted combustion refers to introducing ammonia fuel into plasma, achieving mutual coupling between plasma and ammonia fuel. In this process, plasma can achieve low-temperature combustion of ammonia fuel, improve combustion efficiency, and achieve zero-pollution emissions. While ammonia combustion easily produces high concentrations of NOx, ammonia is also a good NOx reducing agent. Therefore, rationally organizing the flame structure and fully utilizing ammonia's reduction of NOx is beneficial for reducing NOx generation and emissions. Summary of the Invention

[0004] The purpose of this invention is to provide a plasma-assisted combustion type low-NOx flat flame ammonia burner and combustion method, which enables ammonia to ignite rapidly and burn stably through plasma, and reduces NOx formation by directly injecting ammonia into the high-temperature flame.

[0005] To achieve the above objectives, this invention provides a low-NOx plasma-assisted combustion flat-flame ammonia burner employing fuel staging and air staging. The ammonia fuel and combustion air are supplied in stages. First, plasma is used to achieve stable ignition and combustion of primary ammonia fuel with combustion air in the pre-combustion chamber. Then, secondary air is introduced into the combustion chamber through a vortex air intake structure. Simultaneously, ammonia gas is injected through secondary fuel channels arranged in the burner structure, injecting ammonia fuel into the formed ammonia gas planar combustion flame. Under high-temperature and low-oxygen combustion conditions, the combustion and reduction effects of ammonia gas are utilized, thereby reducing the overall NOx formation from ammonia combustion.

[0006] The present invention discloses a low-NOx plasma-assisted flat flame ammonia burner employing fuel staging and air staging, comprising a plasma structure, an air jacket structure, a vortex air intake structure, a secondary fuel pipe, and a burner brick structure.

[0007] Specifically, a low-NOx regenerative flat-flame ammonia burner employing fuel staging includes a plasma structure, an air jacket structure, a vortex air intake structure, a secondary fuel pipe, a horn-shaped burner brick, a pre-combustion chamber, and a combustion chamber. The plasma structure includes a high-voltage electrode, an insulating medium, a cyclone separator, and a grounded metal shell. The horn-shaped burner brick is disposed on the combustion chamber. Preferably, the grounding electrode is sleeved outside the insulating medium, the high-voltage electrode is located inside the insulating medium, and a cavity is formed between the grounding electrode and the insulating medium. The cavity is a primary air ammonia passage (105), and the cyclone separator (104) is disposed inside the primary air ammonia passage. The air jacket structure is connected to the pre-combustion chamber. The plasma structure is connected to the air jacket structure.

[0008] The plasma structure contains a swirler that generates a swirling flow from the fuel flame.

[0009] After passing through the air jacket structure, the plasma structure is connected to the combustion chamber, which contains an ammonia swirling structure to rotate the ammonia. The plasma generates a high-energy, high-temperature, high-speed flame to ignite the ammonia, and the high-density active particles produced help to enhance the combustion performance of ammonia.

[0010] Secondary air is fully mixed with ammonia through a vortex intake structure and combusted to form a planar flame after passing through a trumpet-shaped burner brick; multiple secondary fuel channels are provided at different positions inside the trumpet-shaped burner brick; the secondary fuel pipe injects ammonia directly into the combustion chamber of the planar flame burner through the secondary fuel channels provided at different positions inside the burner brick.

[0011] Furthermore, the plasma structure is connected to the air jacket structure, and primary ammonia fuel is burned through the plasma structure, which contains a cyclone generator to produce ammonia gas swirl.

[0012] Furthermore, the vortex air intake structure is connected to the pre-combustion chamber, and the secondary combustion air is fully mixed and combusted with ammonia in the pre-combustion chamber through the vortex air intake structure, so that the air and ammonia are fully mixed and combusted and a swirling flame is formed in the combustion chamber.

[0013] Furthermore, the air and ammonia are mixed and burned through a trumpet-shaped burner brick to form a planar flame.

[0014] Furthermore, the secondary fuel pipe injects ammonia directly into the flame through secondary fuel nozzles located at different positions within the burner brick.

[0015] A combustion method employing a low-NOx plasma-assisted flat-flame ammonia burner with fuel staging, using the plasma-assisted flat-flame ammonia burner as described above, specifically includes the following steps:

[0016] Step (1): After ammonia enters the plasma structure, it is ignited by a high-temperature, high-speed flame generated by the plasma. The flame then enters the air jacket structure through the plasma cyclone generator and mixes with the primary combustion air for combustion. At the same time, the secondary combustion air is fully mixed with ammonia in the pre-combustion chamber through the vortex intake structure to form a strong swirling combustion. The ammonia plane combustion flame is formed in the trumpet-shaped burner brick. The strong swirling generates a central high-temperature recirculation zone, which further promotes the stable combustion of ammonia. At the same time, a high-temperature, low-oxygen-concentration flame is constructed to suppress the formation of NOx.

[0017] Step (2): Ammonia fuel is injected into the formed ammonia plane combustion flame through the secondary fuel pipe. Under high temperature and low oxygen combustion conditions, the secondary ammonia burns in the low oxygen and high temperature flame, which inhibits the formation of NOx and at the same time reduces the NOx that has already been generated, thereby reducing the overall NOx formation in the ammonia combustion.

[0018] As a further improvement of the present invention, plasma can enhance the stability of airflow and generate a high-temperature, high-speed flame with high energy in the combustion chamber to ignite the combustible mixture and high-density active particles to enhance combustion performance, thereby enabling ammonia to be ignited and combusted stably, reducing the difficulty and instability of ammonia ignition.

[0019] The technical solution provided by this invention has the following significant effects:

[0020] (1) Plasma is used to assist the combustion of ammonia, which promotes the ignition of ammonia, increases the combustion speed of ammonia, and ensures the stability of ammonia combustion; the gas swirl structure and the trumpet-shaped burner brick are used to generate a planar flame, which further promotes the stable combustion of ammonia and improves the combustion efficiency.

[0021] (2) By using the vortex intake structure to input secondary air, the air and ammonia are further mixed and burned to form a strong swirling airflow, thereby improving the combustion efficiency and stability of ammonia.

[0022] (3) By using a porous structure to arrange the ammonia input nozzle, the ammonia is directly injected into the high-temperature flame, so that the secondary ammonia fuel is evenly distributed and burned in the combustion chamber, which can further reduce NOx emissions and achieve the effect of low nitrogen oxide emissions and high-efficiency combustion. Attached Figure Description

[0023] Figure 1 A NOx concentration distribution diagram for a specific embodiment of the present invention;

[0024] Figure 2 The schematic diagram of the low-NOx plasma-assisted flat flame ammonia burner provided by the present invention includes: 100 plasma structure, 200 air sleeve structure, 300 vortex air intake structure, 400 secondary fuel pipe, and 500 horn-shaped burner brick.

[0025] Figure 3 The schematic diagram of the plasma structure of the low-NOx plasma-assisted flat flame ammonia burner provided by the present invention is shown below: 101 Grounding electrode; 102 Insulating medium; 103 High voltage electrode; 104 Cyclone separator; 105 Primary air ammonia gas passage.

[0026] Figure 4 The schematic diagram of the secondary fuel structure of the low-NOx plasma-assisted flat flame ammonia burner provided by the present invention includes: 401 secondary fuel nozzle A, 402 secondary fuel nozzle B, and 403 secondary fuel nozzle C.

[0027] Figure 5 A schematic diagram of gas flow in the low-NOx plasma-assisted flat flame ammonia burner provided by the present invention. Detailed Implementation

[0028] To make the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0029] like Figure 2-4 As shown, according to an embodiment of the present invention, a low-NOx plasma-assisted flat-flame ammonia burner employing fuel staging and air staging is proposed, comprising a plasma structure 100, an air jacket structure 200, a vortex air intake structure 300, a secondary fuel pipe 400, and a horn-shaped burner brick 500. The flat-flame burner also includes a pre-combustion chamber and a combustion chamber. The horn-shaped burner brick (500) is disposed on the combustion chamber.

[0030] The air jacket structure 200 is a tangential air intake structure. The air jacket structure 200 is connected to the pre-combustion chamber of the flat flame burner. The plasma structure 100 is connected to the air jacket structure 200, and ammonia gas undergoes discharge combustion through the plasma structure 100. The plasma structure 100 is a dielectric barrier discharge plasma.

[0031] The vortex intake structure 300 is connected to the air jacket structure 200 and the combustion chamber. The vortex intake structure 300 is a volute intake channel located in the pre-combustion chamber of the flat flame burner. The secondary combustion air is fully mixed and combusted with ammonia in the pre-combustion chamber through the vortex intake structure to form a strong swirling flow, which forms a planar flame in the combustion chamber, further improving the combustion efficiency of ammonia.

[0032] The plasma structure 100 includes a grounding electrode 101, an insulating medium 102, a high-voltage electrode 103, a cyclone separator 104, and a primary ammonia gas passage 105. A cylindrical insulating medium 102 is coaxially sleeved inside the cylindrical grounding electrode 101. The high-voltage electrode 103 is located inside the cylindrical insulating medium 102. The cavity formed between the grounding electrode 101 and the insulating medium 102 is the primary ammonia gas passage 105. A cyclone separator 104 is disposed inside the primary ammonia gas passage 105.

[0033] Air and ammonia are mixed and combusted, forming a planar flame through a horn-shaped burner brick 500. Multiple secondary fuel nozzles are installed at different locations within the horn-shaped burner brick 500. For example, secondary fuel nozzles A401, B402, and C403 are respectively installed at different locations within the horn-shaped burner brick 500. The secondary fuel pipes 400, through a porous structure located at different positions within the burner brick, directly inject ammonia into the combustion chamber of the planar flame burner. The secondary fuel pipe 400 serves as the main secondary fuel delivery pipe. Secondary fuel nozzles A401, B402, and C403 are each independently connected to this main secondary fuel delivery pipe.

[0034] like Figure 5 As shown, a combustion method using a low-NOx plasma-assisted flat-flame ammonia burner with a staged structure, employing the plasma-assisted flat-flame ammonia burner as described above, specifically includes the following steps:

[0035] Step (1): After ammonia enters the plasma structure 100, it passes through the plasma cyclone generator to generate a swirling flame, which enters the air jacket structure 200 and mixes with the primary combustion air for combustion. At the same time, the secondary combustion air passes through the vortex air intake structure 300 and mixes fully with ammonia in the pre-combustion chamber to form a strong swirling combustion. The ammonia plane combustion flame is formed in the trumpet-shaped burner brick 500. Furthermore, due to the strong swirling flow, a central high-temperature recirculation zone is generated, which further promotes the stable combustion of ammonia. At the same time, a high-temperature, low-oxygen-concentration flame is constructed to suppress the formation of NOx.

[0036] Step (2): Ammonia fuel is injected into the formed ammonia plane combustion flame through the secondary fuel pipe 400. Under high temperature and low oxygen combustion conditions, the secondary ammonia burns in the low oxygen and high temperature flame, which inhibits the formation of NOx and at the same time reduces the NOx that has already been generated, thereby reducing the overall NOx formation in the ammonia combustion.

[0037] Step (3): Stage ratio optimization step. When the flat flame ammonia burner is working normally, the air and fuel stage ratio is changed according to the actual combustion situation to explore the optimal low NOx emission point.

[0038] Step (4): Optimize the staged ammonia injection position. When the flat flame ammonia burner is working normally, measure the outlet temperature of different nozzles according to the actual combustion situation, change the staged ammonia injection position and injection angle, and explore the optimal low NOx emission point.

[0039] Step (5): Optimization steps for the horn-shaped burner brick. When the flat flame ammonia burner is working normally, the angle of the burner brick is changed according to the actual combustion situation to explore the best burner brick structure, thereby forming the best planar combustion flame.

[0040] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0041] The technical solution provided by this invention has been experimentally verified in actual experimental research and has achieved ideal experimental results.

[0042] Figure 1 NOx concentration graphs for different ammonia injection ratios and different ammonia injection positions (0mm / 20mm / 40mm / 60mm).

[0043] The technical solution provided by this invention has been experimentally verified in actual experimental research and has achieved ideal experimental results. Table 1 shows the experimental conditions used in the actual experimental research. In this experiment, methane is used as the primary fuel, and the high-temperature environment generated by the combustion of carbon monoxide is used to replace plasma to ignite ammonia. A staged combustion technology is adopted to maintain a certain total calorific value of the fuel. Methane is first introduced into the combustion chamber for stable combustion, and another part of ammonia is directly injected into the combustion chamber as secondary fuel. The staged ratio is the percentage of the total calorific value of the ammonia fuel to the total calorific value of the fuel while keeping the total calorific value of the fuel constant.

[0044] Table 1. Staged Combustion Conditions for Methane Blended with Ammonia

[0045]

[0046] By sampling and analyzing the flue gas inside the combustion chamber during methane-ammonia co-firing combustion under different stage ratios and different ammonia injection positions (0mm / 20mm / 40mm / 60mm) (distance from the combustion chamber), a NOx concentration distribution map was obtained, as shown below. Figure 1 As shown.

[0047] Depend on Figure 1 It can be clearly seen that after using ammonia staged combustion, the lowest NOx emission point appeared at the ammonia mixing position of 40mm under different ammonia mixing ratios. This shows that the burner provided by the present invention can effectively reduce NOx emissions.

[0048] As a further improvement of the present invention, a portion of the ammonia gas is introduced into the ammonia gas planar combustion flame through a staged secondary fuel structure. At this time, the combustion of ammonia gas further consumes oxygen to form a low-oxygen region. Meanwhile, the NOx generated in the flame is reduced under the action of low-oxygen ammonia gas, thereby effectively suppressing the formation of NOx.

[0049] The parts of this invention not described in detail are well-known to those skilled in the art. The embodiments described above are merely preferred embodiments of the invention, and do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Various modifications and improvements to the technical solutions of this invention made by those skilled in the art without departing from the spirit of the invention should fall within the protection scope defined by the claims of this invention.

Claims

1. A plasma-assisted combustion type low-NOx emission ammonia flat flame burner, characterized in that, The system includes a plasma structure (100), an air jacket structure (200), a vortex air intake structure (300), a secondary fuel pipe (400), a horn-shaped burner brick (500), a pre-combustion chamber, and a combustion chamber. The plasma structure (100) includes a grounding electrode (101), an insulating medium (102), a high-voltage electrode (103), a cyclone separator (104), and a primary air ammonia passage (105). The horn-shaped burner brick (500) is mounted on the combustion chamber. The grounding electrode (101) is mounted outside the insulating medium (102), and the high-voltage electrode (103) is located inside the insulating medium. A cavity is formed between the grounding electrode (101) and the insulating medium (102), which is the primary air ammonia passage (105). The cyclone separator (104) is located inside the primary air ammonia passage (105). The plasma structure (100) is connected to the air sleeve structure (200); The vortex air intake structure (300) is connected to the air sleeve structure (200) and the combustion chamber; the vortex air intake structure (300) is a volute air intake channel set in the pre-combustion chamber of the flat flame burner. The secondary combustion air is fully mixed and combusted with ammonia in the pre-combustion chamber through the vortex air intake structure, which further improves the combustion efficiency of ammonia. Air and ammonia are mixed and burned through a horn-shaped burner brick (500) to form a planar flame; multiple secondary fuel nozzles are set at different positions inside the horn-shaped burner brick (500); the secondary fuel pipe (400) directly injects ammonia into the flame of the combustion chamber of the flat flame burner through the secondary fuel nozzles set at different positions inside the burner brick. Ammonia fuel is ignited by flowing through the plasma structure (100); Air is mixed with rotating air and ammonia through an air sleeve structure (200) and combusted to form a planar flame; The vortex intake structure (300) is a volute intake channel located in the pre-combustion chamber of the flat flame burner. Ammonia fuel and combustion air are supplied in stages. First, plasma is used to achieve stable ignition and combustion of primary ammonia fuel and combustion air in the pre-combustion chamber. Then, secondary air is sent into the combustion chamber through the vortex intake structure. At the same time, ammonia is injected through the secondary fuel channel arranged in the burner structure. Ammonia fuel is injected into the ammonia plane combustion flame. Under high temperature and low oxygen combustion conditions, the combustion and reduction effects of ammonia are utilized, thereby reducing the overall NOx generation from ammonia combustion. The secondary fuel pipe (400) is the main secondary fuel delivery pipe.

2. A combustion method using a plasma-assisted combustion type low-NOx emission ammonia flat flame burner, characterized in that, The use of the plasma-assisted combustion type low-NOx emission ammonia flat flame burner as described in claim 1 specifically includes the following steps: Step (1): After ammonia enters the plasma structure (100), it is ignited by a flame generated by the plasma. The flame is then generated by the plasma cyclone generator and enters the air jacket structure (200) to mix with the primary combustion air for combustion. At the same time, the secondary combustion air is fully mixed with ammonia in the pre-combustion chamber through the vortex air intake structure (300) to form swirling combustion. The ammonia plane combustion flame is formed in the trumpet-shaped burner brick (500). The swirling flow generates a central high-temperature recirculation zone, which further promotes the stable combustion of ammonia. At the same time, a high-temperature, low-oxygen-concentration flame is constructed to suppress the formation of NOx. Step (2): Ammonia fuel is injected into the formed ammonia plane combustion flame through the secondary fuel pipe (400). Under high temperature and low oxygen combustion conditions, the secondary ammonia burns in the low oxygen and high temperature flame, which inhibits the formation of NOx and at the same time reduces the NOx that has already been generated, thereby reducing the overall NOx formation in the ammonia combustion.

3. The method according to claim 2, characterized in that, The method further includes: Step (3): Stage ratio optimization step. When the flat flame ammonia burner is working normally, the air and fuel stage ratio is changed according to the actual combustion situation to explore the optimal low NOx emission point.

4. The method according to claim 2, characterized in that, The method further includes: Step (4): Optimization of staged ammonia injection position. When the flat flame ammonia burner is working normally, measure the outlet temperature of different nozzles according to the actual combustion situation, change the staged ammonia injection position and injection angle, and explore the optimal low NOx emission point.

5. The method according to claim 2, characterized in that, The method further includes: Step (5): Optimization of the horn-shaped burner brick. When the flat flame ammonia burner is working normally, the angle of the burner brick is changed according to the actual combustion situation to explore the best burner brick structure, thereby forming the best planar combustion flame.

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