Low-NOx pure ammonia burner based on synergistic effect of air preheating and ammonia fuel reducing agent

Abstract

The invention discloses a low-NOx pure ammonia combustor based on the synergistic effect of air preheating and an ammonia fuel reducing agent, and belongs to the field of ammonia combustion. Comprising an air preheating system and an NH3 reduction system, the air preheating system comprises an air blower, an induced draft fan, two reversing valves and two honeycomb ceramic heat accumulators connected with the reversing valves, and the two honeycomb ceramic heat accumulators are used for preheating air; the NH3 reduction system comprises a rotational flow NH3 auxiliary inlet. The pure ammonia burner comprises at least one primary air inlet, at least one secondary air inlet, at least one NH3 auxiliary inlet and a nozzle used for conveying ammonia fuel. On the basis, the problems of pure ammonia fuel ignition and NOX emission can be remarkably solved, and actual clean application of the ammonia fuel is promoted.

Description

Technical field:

[0001] The present invention belongs to the technical field of pure ammonia burners, and in particular to a low NOx pure ammonia burner based on the synergistic effect of air preheating and an ammonia fuel reducing agent, and belongs to the technical field of energy conversion equipment and environmentally friendly combustion. Background technology:

[0002] Ammonia, as a hydrogen carrier fuel, has the advantages of high energy density, low liquefaction pressure, low storage and transportation costs, and no carbon dioxide in the combustion products. Therefore, the efficient use of ammonia fuel can make the concept of "zero carbon emission from combustion" possible, and has good application prospects. At the same time, ammonia fuel, as a renewable, low-carbon, clean energy, plays a vital role in alleviating global warming, reducing pollution gas emissions, improving energy structure, and achieving sustainable social and economic development.

[0003] However, since the calorific value of ammonia is slightly lower than that of other fuels, the energy required for ignition is relatively high, and direct combustion is still difficult at present. In addition, the flame propagation of ammonia is relatively slow, and the minimum ignition energy is high, which limits the combustion efficiency. Ammonia has poor ignition performance at low temperatures, resulting in a long ignition delay time, which affects the stability of the combustion process. As a new combustion technology, high-temperature air combustion technology (also known as heat storage combustion technology) has the advantages of high efficiency, energy saving, and low pollutant emissions. The key technology of high-temperature air combustion technology is the heat exchanger. In the early 1990s, Japan developed a method of using honeycomb ceramic bodies for heat storage, combining energy saving and environmental protection. This honeycomb ceramic heat storage body has a larger specific area while reducing its volume, and its heat exchange performance is greatly improved, which is widely used. Studies have shown that after air is preheated and enters the combustion chamber to mix with ammonia fuel for combustion, it can increase the ignition heat of ammonia fuel and improve the disadvantage of ammonia fuel being difficult to ignite in application.

[0004] In the actual combustion application process of ammonia fuel, in addition to the above problems, a large amount of NOx will be produced when it reacts with oxygen at high temperature. Due to the complex combustion characteristics of ammonia, it is relatively difficult to control NOx emissions from its fuel type. By adopting selective catalytic reduction (SCR) technology, NOx emissions can be reduced and meet the requirements of emission regulations.

[0005] The principle of SCR (Selective Catalytic Reduction) technology denitrification is to inject ammonia gas, a reducing agent, into the flue gas. Under the action of the catalyst, nitrogen oxides (NOx) react with ammonia gas to produce harmless nitrogen (N2) and water (H2O). The basic chemical equation of SCR denitrification reaction is:

[0006] 4NH3+6NO→5N2+6H2O

[0007] 8NH3+6NO2→7N2+12H2O

[0008] At present, ammonia is used as both a zero-carbon fuel and a reducing agent in the SCR denitrification system. It can effectively improve the denitrification efficiency, system stability and achieve NOx removal, and can significantly reduce pollutant emissions. It is of great significance to achieve the transformation and upgrading of low-carbon production in high-temperature industries, and contribute to the realization of green, low-carbon and sustainable energy development. Summary of the invention:

[0009] In order to improve the ignition difficulty of pure ammonia fuel, NO X The present invention proposes a pure ammonia burner that uses a honeycomb ceramic heat storage body to preheat air, and sets an NH3 reducing agent inlet on the burner to further improve the combustion efficiency and reduce nitrogen oxides NO X emissions.

[0010] The technical solution proposed by the present invention is as follows:

[0011] The present invention discloses an ammonia burner based on high-temperature preheating of a honeycomb ceramic heat accumulator and synergistic action of an ammonia fuel reducing agent, comprising a first honeycomb ceramic heat accumulator (4.1), a second honeycomb ceramic heat accumulator (4.2) and an NH3 reducing agent pure ammonia burner, wherein a blower (1) is connected to a first hole of a first flue gas through a reversing valve (3.1) through a pipeline, the first flue gas is connected to a second flue gas through the first hole of the reversing valve (3.2) through a pipeline via the second honeycomb ceramic heat accumulator (4.2) through the second hole of the reversing valve (3.1), and the second flue gas is divided into two branches through the outlet of the second hole of the reversing valve (3.2), one branch being a primary hot air duct (5) The first flue gas is connected to the primary air inlet (9) on the bottom side of the NH3 reducing agent pure ammonia burner, and the other branch is a secondary air hot air pipeline (6) connected to the secondary air inlet (10) on the middle side of the NH3 reducing agent pure ammonia burner; the first flue gas passes through the fourth hole of the reversing valve (3.1) and is connected to the third hole of the second flue gas reversing valve (3.2) via the first honeycomb ceramic heat storage body (4.1), and the first flue gas passes through the third hole of the reversing valve (3.1) and is connected to the induced draft fan (2) through a pipeline; the top of the NH3 reducing agent pure ammonia burner is provided with a hot flue gas pipeline (7) connected to the fourth hole of the second flue gas reversing valve (3.2);

[0012] The NH3 reducing agent pure ammonia burner is an inverted bottle-type structure, with an ammonia fuel nozzle (8) provided at the center of the bottom, a primary air inlet (9) provided at the side of the bottom, a premixed combustion zone in the middle and lower part of the NH3 reducing agent pure ammonia burner, that is, a diffusion combustion zone in the middle part of the NH3 reducing agent pure ammonia burner, a secondary air inlet (10) provided at the side of the diffusion combustion zone, a reduction zone (catalyst provided as required) above the diffusion combustion zone, and an NH3 reducing agent inlet (11) provided at the side of the reduction zone;

[0013] The NH3 reducing agent inlet (11) is further described as a swirl inlet with a consistent swirl direction. The specific structure includes: a barrel-shaped nozzle wall (15), i.e., an outer cylinder; a main shaft (13) is coaxially located in the barrel-shaped nozzle wall (15); a plurality of blades (12) are fixed to the outer periphery of the main shaft (13); the outer ends of the blades (12) are free relative to the inner surface of the barrel-shaped nozzle wall (15), so that the runner can drive the blades to rotate around the main shaft (13); the barrel-shaped nozzle wall (15) is fixed to the combustion zone wall (14) of the NH3 reducing agent pure ammonia burner; the barrel-shaped nozzle wall (15) is connected to the ammonia pipeline, and when ammonia enters, the blades (12) can be blown to rotate, and the ammonia is evenly distributed in the combustion zone of the NH3 reducing agent pure ammonia burner due to the rotational guidance of the blades (12).

[0014] The blade 12 is fixed on the main shaft 13 and is at an angle of 30°-45° to the main shaft. The main shaft 13 is connected to the external engine. When the external engine is started, the blade 12 starts to rotate clockwise, and the NH3 reducing agent can enter the combustion chamber at different swirl speeds at different speeds. The nozzle wall 15 at the inlet of the reducing agent NH3 is fixed to the combustion chamber wall 14 by welding.

[0015] As a further improvement of the technical solution of the present invention, a pair of honeycomb ceramic heat storage bodies are selected as heat exchangers for air preheating and flue gas cooling, which greatly improves the air preheating temperature, allowing the air temperature to be preheated to a maximum of 1000°C, and reduces the exhaust flue gas temperature to below 200°C, greatly reducing heat energy loss.

[0016] As a further improvement of the technical solution of the present invention, the primary air inlet of the pure ammonia burner is located at the front end of the burner, close to the fuel. The main function of the primary air is to ensure that the ammonia fuel and the combustion air can be fully mixed in the premixed combustion zone of the burner. This helps to achieve a more uniform and stable flame and reduce local high temperature points, thereby reducing the formation of thermal NOx.

[0017] As a further improvement of the technical solution of the present invention, a mixing device such as a vortex generator or a venturi nozzle can be installed in the premixed combustion zone of the pure ammonia burner to promote turbulent mixing of fuel and air.

[0018] As a further improvement of the technical solution of the present invention, the secondary air inlet of the pure ammonia burner is located in the middle of the burner. The main function of the secondary air is to provide additional combustion air for the incompletely reacted ammonia fuel for diffusion combustion. This stage allows the fuel particles to further decompose and contact with oxygen, ensuring more thorough combustion efficiency.

[0019] As a further improvement of the technical solution of the present invention, the secondary air inlet of the pure ammonia burner is a swirl inlet. The secondary air entering the swirl can prolong the residence time of the ammonia fuel, improve the burnout rate, and enhance the combustion intensity. On the other hand, it can greatly reduce the emission of nitrogen oxides, so that it meets the national standards for pollutant gas emissions.

[0020] As a further improvement of the technical solution of the present invention, a small-caliber NH3 nozzle is set at the head of the pure ammonia burner (i.e., the reduction zone) near the flame root as the reducing agent NH3 inlet to ensure that the reducing agent NH3 can be accurately injected into the back of the flame. X NH3, the reducing agent, enters the accumulated NO X A reduction reaction can occur rapidly.

[0021] As a further improvement of the technical solution of the present invention, the small-diameter reducing agent NH3 nozzle near the flame root of the pure ammonia burner head is a swirl inlet. The reducing agent NH3 entering the swirl can be fully mixed with the combustion products and undergo a chemical reaction, and the already formed NOx can be reduced into nitrogen (N2) and water (H2O) by utilizing its reducing properties, thereby significantly reducing NOx emissions.

[0022] As a further improvement of the technical solution of the present invention, the small-diameter reducing agent NH3 nozzle near the flame root of the pure ammonia burner head needs to accurately control the supply amount of the reducing agent NH3 through auxiliary equipment, so that it can fully participate in the NOx reduction reaction without excessively causing incomplete combustion, thereby reducing the emission of nitrogen oxides.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] The low NOx pure ammonia burner with synergistic air preheating and ammonia fuel reductant described in the present invention uses honeycomb ceramic heat storage technology for air preheating, making full use of the heat generated by the combustion of ammonia fuel, without the need to use excess heat input, and only using the heat of the flue gas can greatly increase the temperature of the air. In addition, this burner uses the reducing property of NH3 itself to fully reduce the nitrogen oxides in the combustion products at the same time, which can greatly reduce the emission of nitrogen oxides to a certain extent, without the generation of by-products, and will not cause secondary pollution to the environment. The pure ammonia burner of the present invention can significantly reduce the emission of pollutants, which is of great significance for realizing the transformation and upgrading of low-carbon production in high-temperature industries, contributing to the realization of green, low-carbon, and sustainable energy development, and providing a practical technical route for the realization of national emission standards at this stage and in the future. Description of the drawings:

[0025] Figure 1 It is a working schematic diagram of the present invention;

[0026] Figure 2 It is the NH3 reducing agent for pure ammonia burner;

[0027] Figure 3 This is a front view of the NH3 reducing agent swirl inlet of a pure ammonia burner;

[0028] In the figure: 1. blower; 2. induced draft fan; 3.1. first reversing valve; 3.2. second reversing valve; 4.1. first honeycomb ceramic heat storage body; 4.2. second honeycomb ceramic heat storage body; 5. primary hot air duct; 6. secondary hot air duct; 7. hot flue gas duct; 8. ammonia fuel nozzle; 9. primary air inlet; 10. secondary air inlet; 11. NH3 reducing agent inlet; 12. blades; 13. main shaft; 14. combustion zone wall; 15. nozzle wall; 16. gas duct; 17. gas duct; 18. gas duct; 19. gas duct; 20. cold flue gas duct. Specific implementation method:

[0029] The technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings in the present invention. In the specification, the same figure numerals represent the same or similar parts. The description of this example is intended to explain the present invention, and does not mean that all examples are limited to this. The embodiments obtained based on this example without making other creative work are all within the scope of protection of the present invention.

[0030] The matters not described in detail in the present invention are all known technologies in the technical field.

[0031] like Figure 1 As shown, the present invention is a low NOx pure ammonia burner based on the synergistic effect of air preheating and ammonia fuel reducing agent, including a blower 1, an induced draft fan 2, a first reversing valve 3.1, a second reversing valve 3.2, a first honeycomb ceramic heat storage body 4.1, a second honeycomb ceramic heat storage body 4.2 and an ammonia reducing agent burner.

[0032] During stable operation, air is introduced into the honeycomb ceramic heat storage body 4.1 through the blower 1, the reversing valve 3.1 and the gas pipeline 18. At this time, the air is heated up while the heat storage body is cooled down. The preheated temperature can reach up to 1000°C. The high-temperature air is transported to the primary air inlet 9 of the pure ammonia burner through the gas pipeline 19, the reversing valve 3.2 and the primary air hot air pipeline 5. As the primary air for the combustion of ammonia fuel, the fuel ammonia enters the premixed combustion zone of the combustion chamber through the nozzle 8 to mix and burn with the high-temperature primary air; the high-temperature air is transported to the secondary air inlet 10 of the pure ammonia burner through the reversing valve 3.2 and the secondary air hot air pipeline 6. As the secondary air for the combustion of ammonia fuel, it enters the diffusion combustion zone of the pure ammonia burner and re-diffusion-burns with the ammonia fuel that is not completely burned in the premixed combustion zone. Part of the reducing agent NH3 extracted from the main fuel flow enters the reduction zone of the pure ammonia burner through the NH3 reducing agent inlet 11 to undergo a reduction reaction with the nitrogen oxides in the combustion products. In order to make the reducing agent NH3 swirl into the reduction zone of the combustion chamber and fully react with the nitrogen oxides in the combustion products, a swirl device is set at the NH3 reducing agent inlet 11, wherein the blades 12 at the inlet of the swirl device are fixed on the main shaft 13 and are at an angle of 30°-45° with the main shaft. The main shaft 13 is connected to the external engine. When the external engine is started, the blades 12 begin to rotate clockwise, and the NH3 reducing agent can enter the combustion chamber at different swirl speeds at different speeds. The nozzle wall 15 at the reducing agent NH3 inlet is fixed to the combustion chamber wall 14 by welding.

[0033] The combustion products and reduction products flow into the honeycomb ceramic heat storage body 4.2 through the hot flue gas duct 7, the reversing valve 3.2 and the gas duct 16. At this time, the flue gas is cooled and the heat storage body is heated. The flue gas temperature passing through the honeycomb ceramic heat storage body 4.2 can be reduced to 200°C. The cooled flue gas is discharged through the gas duct 17, the reversing valve 3.1, the cold flue gas duct 20 and the induced draft fan 2.

[0034] According to the actual working conditions, the directions of the reversing valves 3.1 and 3.2 can be adjusted within a time range of 30s to 120s, and the gas flows in the gas pipelines 16, 17, 18 and 19 are opposite to the previous ones, so that the ceramic heat storage body 4.2 preheats the air while the ceramic heat storage body 4.1 cools the flue gas and stores heat, so that the ceramic heat storage body maintains a periodic heating and cooling process, thereby realizing continuous preheating of the air.

Claims

1. An ammonia burner based on high temperature preheating of honeycomb ceramic heat storage body and synergistic action of ammonia fuel reducing agent, characterized in that: The invention comprises a first honeycomb ceramic heat accumulator (4.1), a second honeycomb ceramic heat accumulator (4.2) and an NH3 reducing agent pure ammonia burner, wherein the blower (1) is connected to the first hole of the first flue gas through the reversing valve (3.1) through a pipeline, the first flue gas is connected to the first hole of the second flue gas through the reversing valve (3.2) through the pipeline via the second honeycomb ceramic heat accumulator (4.2) through the second hole of the reversing valve (3.2), and the second flue gas is divided into two branches through the outlet of the second hole of the reversing valve (3.2), one branch is a primary hot air duct (5) connected to the bottom side of the NH3 reducing agent pure ammonia burner. The primary air inlet (9) is connected, and the other branch is a secondary air hot air pipeline (6) connected to the secondary air inlet (10) on the side of the middle part of the NH3 reducing agent pure ammonia burner; the first flue gas passes through the fourth hole of the reversing valve (3.1) and is connected to the second flue gas through the third hole of the reversing valve (3.2) via the first honeycomb ceramic heat storage body (4.1), and the first flue gas passes through the third hole of the reversing valve (3.1) and is connected to the induced draft fan (2) through a pipeline; a hot flue gas pipeline (7) is provided on the top of the NH3 reducing agent pure ammonia burner and is connected to the second flue gas through the fourth hole of the reversing valve (3.2); The NH3 reducing agent pure ammonia burner is an inverted bottle-type structure, with an ammonia fuel nozzle (8) provided at the center of the bottom, a primary air inlet (9) provided at the side of the bottom, the lower middle part of the NH3 reducing agent pure ammonia burner is a premixed combustion zone, that is, the middle part of the NH3 reducing agent pure ammonia burner is a diffusion combustion zone, a secondary air inlet (10) is provided at the side of the diffusion combustion zone, the top of the diffusion combustion zone is a reduction zone, and an NH3 reducing agent inlet (11) is provided at the side of the reduction zone.

2. According to claim 1, an ammonia burner based on high temperature preheating of a honeycomb ceramic heat storage body and synergistic action of an ammonia fuel reducing agent, characterized in that: The NH3 reducing agent inlet (11) is a swirl inlet with a consistent swirl direction. The specific structure includes: a barrel-shaped nozzle wall (15), i.e., an outer cylinder; a main shaft (13) is coaxially located in the barrel-shaped nozzle wall (15); a plurality of blades (12) are fixed to the outer periphery of the main shaft (13); the outer ends of the blades (12) are free relative to the inner surface of the barrel-shaped nozzle wall (15), so that the runner can drive the blades to rotate around the main shaft (13); the barrel-shaped nozzle wall (15) is fixed to the combustion zone wall (14) of the NH3 reducing agent pure ammonia burner; the barrel-shaped nozzle wall (15) is connected to the ammonia pipeline, so that when ammonia enters, the blades (12) can be blown to rotate, and the ammonia is evenly distributed in the combustion zone of the NH3 reducing agent pure ammonia burner due to the rotational guidance of the blades (12); The blade (12) is fixed on the main shaft (13) and forms an angle of 30°-45° with the main shaft. The main shaft (13) is connected to an external engine. When the external engine is started, the blade (12) starts to rotate clockwise, and the NH3 reducing agent can enter the combustion chamber at different swirl speeds at different rotation speeds. The nozzle wall (15) at the inlet of the reducing agent NH3 and the combustion chamber wall (14) are fixed together by welding.

3. A method for operating an ammonia burner based on high temperature preheating of a honeycomb ceramic heat storage body and synergistic action of an ammonia fuel reducing agent as described in claim 1 or 2, characterized in that: During stable operation, air is introduced into the first honeycomb ceramic heat storage body (4.1) through the blower (1) and the first reversing valve (3.1). At this time, the air is heated up while the heat storage body is cooled down. The temperature after preheating can reach up to 1000°C. The high-temperature air is transported to the primary air inlet (9) of the pure ammonia burner through the second reversing valve (3.2) and the primary air hot air pipeline (5) as the primary air for the combustion of ammonia fuel. The fuel ammonia enters the premixed combustion zone of the combustion chamber through the nozzle (8) and is mixed and burned with the high-temperature primary air entering from the primary air inlet (9). At the same time, the high-temperature air is transported to the secondary air inlet (10) of the pure ammonia burner through the second reversing valve (3.2) and the secondary air hot air pipeline (6) as the secondary air for the combustion of ammonia fuel and enters the diffusion combustion zone of the pure ammonia burner to re-diffusion-burn with the ammonia fuel that has not been completely burned in the premixed combustion zone. Part of the reducing agent NH3 extracted from the main fuel flow enters the reduction zone of the pure ammonia burner through the NH3 reducing agent inlet (11) to undergo a reduction reaction with nitrogen oxides in the combustion products; The combustion products and the reduction products flow into the second honeycomb ceramic heat storage body (4.2) via the hot flue gas pipeline (7) and the second reversing valve (3.2). At this time, the flue gas is cooled and the heat storage body is heated. The temperature of the flue gas passing through the second honeycomb ceramic heat storage body (4.2) can be reduced to 200° C. The cooled flue gas is discharged via the first reversing valve (3.1) and the induced draft fan (2).

4. The method according to claim 3, characterized in that According to actual working conditions, the directions of the first reversing valve (3.1) and the second reversing valve (3.2) are adjusted within a time range of 30s to 120s, so that the gas flow direction is opposite to that before, so that the second ceramic heat storage body (4.2) preheats the air while the first ceramic heat storage body (4.1) cools the flue gas and stores heat, so that the ceramic heat storage body maintains a periodic heating and cooling process, thereby realizing continuous preheating of the air.

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