Partially pre-decomposed ammonia gas reverse spraying burner

Abstract

The invention discloses a partially pre-decomposed ammonia gas reverse-spraying burner which is characterized in that a first-stage ammonia gas channel, a central air channel, a second-stage ammonia gas channel and a secondary air channel are arranged in the ammonia gas reverse-spraying burner step by step from inside to outside, and a third-stage ammonia gas channel is arranged in the secondary air channel; ammonia gas introduced from the first-stage ammonia gas channel is mixed with air in the central air channel for combustion, and a pyrolysis reaction of the ammonia gas is carried out in the pre-combustion chamber; ammonia gas introduced by the second-stage ammonia gas channel enters the pre-combustion chamber to be mixed with combustion flue gas, and the ammonia gas which is not subjected to combustion reaction is pyrolyzed into hydrogen and nitrogen under the oxygen-deficient and rich-combustion conditions; and the ammonia gas introduced into the third-stage ammonia gas channel and the mixed gas of the pyrolyzed hydrogen and nitrogen are mixed with the hot secondary air introduced into the secondary air channel for combustion. According to the invention, the air classification technology is utilized, and the effect of pyrolyzing part of ammonia gas in advance is achieved by igniting high-temperature flue gas generated by part of ammonia gas, so that NOx generated in the ammonia combustion process is reduced, and the purposes of energy conservation and emission reduction are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of boiler combustion devices, and particularly relates to a partially pre-decomposed ammonia reverse injection burner. Background Art

[0002] With the intensification of the greenhouse effect, countries have also increased their attention to greenhouse gases. Among them, carbon dioxide is the main greenhouse gas. However, a report released by the International Energy Agency (IEA) in 2023 shows that the global energy-related carbon dioxide emissions exceeded 36.8 billion tons in 2022. Carbon dioxide emissions from the combustion of fossil fuels account for a large proportion. Therefore, starting from fossil fuels is an effective way to reduce carbon dioxide emissions. Since most Asian countries still mainly rely on coal-fired power generation, the carbon dioxide emissions generated by its combustion are relatively high. Therefore, in the above background, exploring alternative fuels such as low-carbon or zero-carbon fuels has become a hot issue in the combustion field.

[0003] Ammonia, as a hydrogen carrier, is a typical carbon-free hydrogen-rich fuel with a high energy density. It can be compressed and stored in gas cylinders or liquid tanks for long-term storage. In addition, the infrastructure for ammonia transportation is very developed. Therefore, ammonia has advantages in terms of storage and transportation. The following several structures of ammonia burners are disclosed in the prior art, for example:

[0004] Chinese Patent CN116734255A discloses an ammonia burner that can form a pre-combustion cage flame inside. A guide vane is arranged in the shell to provide air for the gas at the outlet of the ammonia pipeline and the gas at the outlet of the gas pipeline and wrap it, and move it towards the outside of the front end of the shell, providing a high-temperature and oxygen-deficient atmosphere for ammonia to pyrolyze as much as possible.

[0005] Chinese Patent CN116379426A discloses a reverse injection ammonia burner, including an outer sleeve, an inner sleeve, and an injection body arranged at the outlet end of the inner sleeve. The outer diameter of the injection body increases along the outlet direction to form a ring-shaped conical guide wall. A plurality of ammonia injection holes facing the air inlet direction are annularly distributed on the guide wall to inject ammonia reversely, extending the residence time of ammonia, increasing the disturbance, strengthening the mixing of air and ammonia in this part. Under the guidance of the guide wall, the mixed gas flows forward and towards the periphery and is secondarily mixed with the air flowing through the outer ring area to further enhance the mixing.

[0006] Chinese Patent CN116608465A discloses an ammonia burner with a double-layer shell structure having a function of spatially graded ammonia injection. There is a gap between the inner combustion burner shell and the outer combustion burner shell, which is used as a reduction ammonia channel for injecting ammonia and reducing the products after ammonia combustion. The structure is simple and the maintenance cost is low.

[0007] Most of the existing ammonia burners only focus on the stable combustion of ammonia or only consider the NOx emission problem, and there are few ammonia burners that combine the two. How to achieve both the stable combustion of ammonia and low pollutant emissions is still an urgent problem to be solved. Summary of the Invention

[0008] The burner of the present invention utilizes air staging technology and relates to an economical and environmentally friendly ammonia burner. It can make some ammonia pyrolyze in advance by using the high-temperature flue gas generated by igniting part of the ammonia, thereby reducing the NOx generated during the ammonia combustion process and achieving the goal of energy conservation and emission reduction. The specific technical solution of the present invention is as follows:

[0009] A partially pre-decomposed ammonia reverse injection burner, in which a primary ammonia channel, a central air channel, a secondary ammonia channel, and a secondary air channel are arranged step by step from the inside out, and a tertiary ammonia channel is arranged in the secondary air channel;

[0010] The ammonia introduced into the primary ammonia channel is mixed with the air in the central air channel and burned, and the pyrolysis reaction of ammonia is carried out in the pre-combustion chamber;

[0011] The ammonia introduced into the secondary ammonia channel enters the pre-combustion chamber and is mixed with the combustion flue gas, and the ammonia that has not undergone a combustion reaction is pyrolyzed into hydrogen and nitrogen under oxygen-deficient and fuel-rich conditions;

[0012] The ammonia introduced into the tertiary ammonia channel is mixed with the pyrolyzed hydrogen and nitrogen mixed gas, and is mixed and burned with the hot secondary air introduced into the secondary air channel.

[0013] The present invention provides a burner that can make some ammonia pre-decompose in an oxygen-deficient environment, thereby ensuring stable combustion while reducing the content of nitrogen oxides generated during the co-combustion of coal and ammonia, and solving the problems of difficult stable combustion and high nitrogen oxide emissions in the process of co-combustion of pulverized coal and ammonia in the prior art.

[0014] The following also provides several optional ways, which are not additional limitations to the above overall solution, but only further supplements or optimizations. Without technical or logical contradictions, each optional way can be combined with the above overall solution alone, or multiple optional ways can be combined with each other.

[0015] Preferably, the primary ammonia channel is located inside the central air channel, and the end of the primary ammonia channel extending into the pre-combustion chamber is provided with a primary ammonia channel nozzle, and the ammonia in the primary ammonia channel nozzle is mixed with the air in the central air channel and then undergoes a pyrolysis reaction.

[0016] Preferably, the pre - combustion chamber has a shape that is wide in the middle and gradually tapers at both ends, and an umbrella - shaped reflux cap is arranged inside the pre - combustion chamber; the reflux cap enables the high - temperature flue gas after the combustion of primary ammonia to flow reversely in the pre - combustion chamber and mix with the ammonia introduced through the secondary ammonia channel.

[0017] Preferably, a swirl vane is arranged in the secondary ammonia channel to generate swirl for the introduced ammonia.

[0018] Preferably, the central air channel has a central air channel interface that extends radially out of the burner housing.

[0019] Preferably, the secondary air channel includes an inner secondary air channel and an outer secondary air channel, and the tertiary ammonia channel passes through the inner secondary air channel and its end extends into the main combustion zone at the end of the burner housing.

[0020] Preferably, swirl vanes are arranged at the outlet of the outer secondary air channel to make the outer secondary air generate swirl.

[0021] Preferably, a tertiary ammonia nozzle is arranged at the end of the tertiary ammonia channel extending into the main combustion zone, and the tertiary ammonia nozzle faces the inlet direction of the inner secondary air channel.

[0022] Preferably, both the inner secondary air channel and the outer secondary air channel are annular air ducts, and the ends of the air ducts leading to the main combustion zone are in a flared shape facing outward.

[0023] Preferably, a bluff body facing the pre - combustion chamber is arranged in the main combustion zone. The bluff body is located at the outlet of the burner. When the air flow passes through the bluff body, a flue gas recirculation zone will be generated behind it, which plays a role in stabilizing combustion.

[0024] Compared with the prior art, the innovative points and beneficial effects of the present invention are as follows:

[0025] Aiming at the problem of a relatively high generation amount of nitrogen oxides during the pure ammonia combustion process, compared with the existing ammonia burners, the generation amount of nitrogen oxides can be reduced. Since there is N element in ammonia, a large amount of NOx is easily generated during the combustion reaction with air. The present invention reduces the NOx generated in the subsequent combustion process by pyrolyzing the remaining ammonia with the high - temperature flue gas generated by igniting part of the ammonia, that is, decomposing ammonia into hydrogen and nitrogen in the high - temperature pre - combustion chamber before mixing with air for combustion. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural sectional view of the ammonia burner of the present invention;

[0027] In the figure: 1 - outer secondary air channel, 2 - inner secondary air channel, 3 - tertiary ammonia spray gun, 4 - secondary ammonia inlet, 5 - primary ammonia inlet, 6 - central air channel, 7 - central air channel inlet, 8 - ammonia header, 9 - outer secondary air swirl vane, 10 - secondary ammonia channel swirl vane, 11 - reflux cap, 12 - pre - combustion chamber, 13 - ignition gun, 14 - bluff body, 15 - tertiary ammonia nozzle, 16 - primary ammonia nozzle;

[0028] Figure 2 It is a schematic diagram of the working principle of the ammonia burner in the embodiment of the present application;

[0029] In the figure: 110 - burnout zone, 120 - main combustion zone, 130 - high - temperature pyrolysis zone, 140 - high - temperature flue gas recirculation zone. Detailed implementation manners

[0030] In the following description, many specific details are set forth to facilitate a thorough understanding of the present invention. However, the present invention may be implemented in other ways different from those described herein. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0031] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described by referring to the drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0032] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0033] In addition, in the present invention, descriptions such as "first", "second", "one", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined as "first" and "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0034] In the present invention, unless otherwise clearly specified or defined, terms such as "connection" and "fixation" shall be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral body; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] As Figure 1 and Figure 2 shown, a partially pre-decomposed ammonia reverse injection burner includes a burner housing. Inside the burner, a primary ammonia channel 5, a central air channel 6, a secondary ammonia channel 4, and a secondary air channel are arranged step by step from the inside outwards. A tertiary ammonia channel 3 is arranged in the secondary air channel; the ammonia introduced into the primary ammonia channel 5 mixes with the air in the central air channel 6 and burns, and the pyrolysis reaction of ammonia occurs in the pre-combustion chamber 12; the ammonia introduced into the secondary ammonia channel 4 enters the pre-combustion chamber and mixes with the combustion flue gas, and under the condition of oxygen-deficient and fuel-rich, the ammonia that has not undergone a combustion reaction is pyrolyzed into hydrogen and nitrogen; the ammonia introduced into the tertiary ammonia channel 3 mixes with the pyrolyzed hydrogen and nitrogen mixed gas, and mixes and burns with the hot secondary air introduced into the secondary air channel.

[0036] In this embodiment, the primary ammonia channel 5, the secondary ammonia channel 4, and the tertiary ammonia channel 3 are all connected to an ammonia header 8 serving as a gas source. The central air channel 6 and the secondary air channel are both used to introduce air.

[0037] In another preferred embodiment, the primary ammonia channel 5 is located inside the central air channel 6. An end of the primary ammonia channel 5 extending into the pre-combustion chamber 12 is provided with a primary ammonia nozzle 16. The ammonia at the nozzle of the primary ammonia channel 5 mixes with the air in the central air channel and undergoes a pyrolysis reaction. The primary ammonia nozzle 16 is one or more radially opened, perpendicular to the intake direction of the central air channel, and enters the pre-combustion chamber under the push of the air. The central air channel 6 has a central air channel inlet 7 extending radially out of the burner housing.

[0038] In this embodiment, the primary ammonia channel 5 is connected to the ammonia header 8. A primary ammonia channel nozzle 16 is provided at the top of the primary ammonia channel 5. Part of the ammonia introduced through the primary ammonia channel 5 is ejected from the primary ammonia nozzle 16. The central air channel 6 introduces central air through the central air channel interface 7, mixes with the ammonia ejected from the primary ammonia channel 5, and undergoes a combustion reaction after being ignited by an igniter 13. The generated high-temperature flue gas flows reversely after passing through an umbrella-shaped reflux cap 13 and enters the pre-combustion chamber 12, and the pyrolysis reaction of ammonia occurs in the pre-combustion chamber 12.

[0039] In another preferred embodiment, the pre-combustion chamber 12 is wide in the middle and gradually narrows at both ends. An umbrella-shaped reflux cap 11 is arranged in the pre-combustion chamber 12. The reflux cap 11 enables the high-temperature flue gas after the combustion of primary ammonia to flow reversely in the pre-combustion chamber 12 and mix with the ammonia introduced through the secondary ammonia channel. The side where the reflux cap 11 opens faces the outlet of the central air channel 6.

[0040] In another preferred embodiment, the primary ammonia channel 5 and the central air channel 6 are located on the central axis in the secondary ammonia channel 2. A secondary ammonia channel swirl vane 10 is installed in the secondary ammonia channel 2 to generate swirl for the introduced ammonia.

[0041] The secondary ammonia channel 4 is connected to the ammonia header 8. The secondary ammonia channel swirl vane 10 arranged in the secondary ammonia channel 4 makes the ammonia generate swirl, better mix with the flue gas, and thus undergo a pyrolysis reaction. Part of the ammonia introduced through the secondary ammonia channel 4 enters the pre-combustion chamber 12 after swirling, fully mixes with the counter-flowing flue gas, and under oxygen-deficient and fuel-rich conditions, the ammonia that has not undergone a combustion reaction is pyrolyzed into hydrogen and nitrogen.

[0042] In another preferred embodiment, the secondary air channel includes an inner secondary air channel 2 and an outer secondary air channel 1. The tertiary ammonia channel 3 passes through the inner secondary air channel 2 and its end extends into the main combustion zone 120 at the end of the burner housing. An outer secondary air swirl vane 9 is arranged at the outlet of the outer secondary air channel 1 to make the outer secondary air generate swirl. Both the inner secondary air channel 2 and the outer secondary air channel 1 are annular air ducts, and the ends of the air ducts leading to the main combustion zone are in a flared shape facing outward. The hot secondary air is divided into two parts, inner secondary air and outer secondary air, and is introduced into the furnace through the inner secondary air channel 1 and the outer secondary air channel 2 respectively. By means of air staging technology, the generation of some nitrogen oxides is inhibited, and the ammonia and the hydrogen and nitrogen mixed gas formed after pyrolysis are mixed and burned with the secondary air.

[0043] In another preferred embodiment, a tertiary ammonia nozzle 15 is arranged at the end of the secondary ammonia channel 3 extending into the main combustion zone, and the tertiary ammonia nozzle faces the air inlet direction of the inner secondary air channel. For the specific structure, reference can be made to the arrangement method of the ammonia injection holes in the patent document with the publication number CN116379426A.

[0044] In another preferred embodiment, a bluff body 14 facing the pre-combustion chamber 12 is arranged in the main combustion zone 120. The bluff body 14 is located at the outlet of the burner. When the air flow passes through the bluff body, a flue gas recirculation zone will be generated behind it, playing a role in stabilizing combustion.

[0045] The tertiary ammonia channel 3 is connected to the ammonia header 8. Tertiary ammonia is introduced through the tertiary ammonia channel 3, ejected through the tertiary ammonia nozzle 15, and the mixing of ammonia and air is enhanced by reverse jet to enhance combustion stability. At the same time, the tertiary ammonia is injected into the latter half of the combustion zone, and part of the already generated NOx can be reduced by the reaction 6NO + 4NH3 = 6H2O + 5N2, reducing the NOx generated by combustion. The outer secondary air channel 1 and the inner secondary air channel 2 are used to introduce hot secondary air. An outer secondary air swirl vane 9 is provided at the outlet of the outer secondary air channel 1, causing the outer secondary air to generate swirl, further enhancing the mixing of air and fuel, and ensuring the burnout characteristics of the burner.

[0046] The burner of the present application can ensure the stability during the ammonia combustion process by setting the reflux cap and the bluff body structure, and at the same time form a local recirculation zone behind it, which is beneficial to the heat exchange and combustion of ammonia, and to a certain extent, can reduce the content of nitrogen oxides generated during combustion while ensuring stable combustion.

[0047] Combined with the ammonia reverse injection burner in the above embodiments, the specific operation process is further described:

[0048] When the ammonia burner is in operation, as Figure 1 shown: In terms of ammonia supply, the ammonia header 8 stores and supplies sufficient ammonia in real time. The inlet end of the primary ammonia inlet 5 channel, the inlet section of the secondary ammonia inlet 4 channel, and the inlet end of the tertiary inlet spray gun 3 are all connected to the ammonia header 8 to obtain ammonia; in terms of air supply, the air in the central air channel 6 is supplied by the primary air through the central air channel inlet 7, and the inlet ends of the outer secondary air channel 1 and the inner secondary air channel 2 are connected to the secondary air fan to obtain hot secondary air.

[0049] The primary ammonia and the central air reach in front of the umbrella-shaped reflux cap 11 after passing through the primary ammonia channel 5 and the central air channel 6 respectively. The primary ammonia is ejected radially through the small holes at the end of the primary ammonia channel 5, and the central air is ejected axially, thereby forming a recirculation zone here and being ignited by the igniter 13. Due to the existence of the umbrella-shaped reflux cap 11, the mixing of the primary ammonia and the central air is strengthened, the residence time of the mixed gas is increased, and the temperature level in front of the umbrella-shaped reflux cap 11 is increased, further promoting the stable combustion of the primary ammonia.

[0050] The aforementioned high-temperature flue gas is carried by the secondary ammonia after recirculation to as Figure 2In the shown high-temperature pyrolysis zone, since the secondary ammonia gas comes through the secondary ammonia gas cyclone blades 10, the heat and mass transfer between the high-temperature flue gas and the secondary ammonia gas is strengthened. And in this area, because the central air has been consumed by the primary ammonia gas, a uniform high-temperature oxygen-deficient and ammonia-rich atmosphere is formed. Therefore, the secondary ammonia gas mainly pyrolyzes in this area to undergo the reaction 2NH3 = N2 + 3H2 to generate N2 and H2. For the NOx generated by the primary ammonia gas and the central air, it is reduced in this atmosphere to undergo the reactions 4NH3 + 6NO = 5N2 + 6H2O and 8NH3 + 6NO2 = 7N2 + 12H2O. Therefore, the generation amounts of the secondary ammonia gas and the primary ammonia gas NOx are greatly reduced.

[0051] The main components of the flue gas at the outlet of the high-temperature pyrolysis zone are N2, H2, H2O, NH3, etc. After leaving the pyrolysis zone, it is wrapped by the inner secondary air and impacts the bluff body 14 to change the flow direction and is fully mixed with the tertiary ammonia gas ejected radially from the tertiary ammonia gas channel nozzle 15 and the hot secondary air outside the nozzle. As shown in Figure 2 It burns in the main combustion zone. Due to the different flow directions of the airflows, the heat and mass transfer are strengthened, and the combustion of NH3 and H2 is stabilized. The existence of the bluff body 14 makes the high-temperature flue gas at the outlet of the high-temperature pyrolysis zone form a high-temperature flue gas recirculation zone behind it, further strengthening the stable combustion of ammonia gas. And in this area, since less outer secondary air enters and it is still under the reaction condition of slightly excessive fuel, the formation of NOx is inhibited.

[0052] Finally, the outer secondary air coming through the outer secondary air swirl blades 9 is strongly mixed with the aforementioned flue gas mixture in the Figure 2 burnout zone and completely reacts with the remaining fuel. At the same time, due to the principle of the main combustion zone and the uniform heat exchange between the outer secondary air and the flue gas, the temperature in this area is already lower than the highest temperature, reducing the generation amount of NOx.

[0053] In summary, the ammonia burner of the present application mainly combines the air staging technology (actually dividing both air and ammonia into 3 stages and sending them into combustion) and the bluff body flame stabilization technology (forming 2 recirculation zones). Considering the influence of the flow field, combustion, etc. comprehensively, it realizes stable combustion and low pollutant emissions, achieving the effect of being both economical and environmentally friendly.

[0054] The above description is only a preferred embodiment of the present invention and is not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A partially pre-decomposed ammonia reverse injection burner, characterized in that: The ammonia reverse injection burner is provided with a primary ammonia channel, a central air channel, a secondary ammonia channel and a secondary air channel from the inside to the outside, and a tertiary ammonia channel is provided in the secondary air channel; The ammonia introduced into the primary ammonia channel is mixed with the air in the central air channel and combusted, and a thermal decomposition reaction of the ammonia is performed in the pre-combustion chamber; The ammonia introduced into the secondary ammonia channel enters the pre-combustion chamber and mixes with the combustion flue gas, so that the ammonia that has not undergone combustion reaction is pyrolyzed into hydrogen and nitrogen under the condition of oxygen-poor and fuel-rich; The ammonia introduced into the tertiary ammonia channel and the mixed gas of hydrogen and nitrogen after pyrolysis are mixed with the hot secondary air introduced into the secondary air channel and burned.

2. The partially pre-decomposed ammonia reverse injection burner according to claim 1, characterized in that: The primary ammonia channel is located in the central air channel, and a primary ammonia channel nozzle is arranged at the end of the primary ammonia channel extending into the pre-combustion chamber. The primary ammonia channel nozzle is mixed with the air in the central air channel to generate a pyrolysis reaction.

3. The partially pre-decomposed ammonia reverse injection burner according to claim 1, characterized in that: The shape of the pre-combustion chamber is wide in the middle and gradually narrows at both ends. An umbrella-shaped reflux cap is arranged in the pre-combustion chamber; the reflux cap allows the high-temperature flue gas after the combustion of the primary ammonia to flow in reverse in the pre-combustion chamber and mix with the ammonia introduced into the secondary ammonia channel.

4. The partially pre-decomposed ammonia reverse injection burner according to claim 1, characterized in that: The secondary ammonia channel is provided with a secondary ammonia channel swirl blade for generating swirl of the introduced ammonia.

5. The partially pre-decomposed ammonia reverse injection burner according to claim 1, characterized in that: The central air passage has a central air passage interface which radially extends out of the burner housing.

6. The partially pre-decomposed ammonia reverse injection burner according to claim 1, characterized in that: The secondary air channel comprises an inner secondary air channel and an outer secondary air channel. The tertiary ammonia channel passes through the inner secondary air channel and its end extends into the main combustion zone at the end of the burner shell.

7. The partially pre-decomposed ammonia reverse injection burner according to claim 6, characterized in that: An external secondary air swirl blade is arranged at the outlet of the external secondary air channel so that the external secondary air generates a swirl.

8. The partially pre-decomposed ammonia reverse injection burner according to claim 6, characterized in that: The end of the tertiary ammonia passage extending into the main combustion zone is provided with a tertiary ammonia nozzle, and the tertiary ammonia nozzle faces the air inlet direction of the inner secondary air passage.

9. The partially pre-decomposed ammonia reverse injection burner according to claim 6, characterized in that: The inner secondary air channel and the outer secondary air channel are both annular air channels, and the ends of the air channels leading to the main combustion zone are in an outwardly flared shape.

10. The partially pre-decomposed ammonia reverse injection burner according to claim 1, characterized in that: A bluff body is arranged in the main combustion zone facing the pre-combustion chamber.

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