Graded ammonia-assisted combustor adopting exhaust gas recirculation preheating

Abstract

The invention provides a staged ammonia-assisted combustor adopting exhaust gas recirculation preheating, which belongs to the field of combustors, and comprises a reaction gas pipeline, an exhaust gas pipeline, a combustion pipeline, a secondary air pipeline, a swirler, an air distributor, an igniter and a flame arrester, an air distributor is installed at the junction of the reaction gas pipeline and the secondary air pipeline, flame arresters and igniters are installed on the front portion and the rear portion of an inlet of the combustion pipeline respectively, and flame arresters are installed at the two ends of an outlet of the secondary air pipeline respectively; after being preheated by exhaust gas recirculation, a small part of reaction gas is fed into the combustion pipeline by the air distributor and is ignited by the igniter to form stable stagnant flames, and a large amount of mixed gas from the secondary air pipeline is ignited. The device is used for solving the problem that stable ignition and combustion of ammonia are difficult, meanwhile, the device is simple in structure, easy to manufacture and high in component adaptability, and energy utilization of the ammonia is promoted.

Description

Technical Field

[0001] The invention belongs to the field of burners, and in particular relates to a staged ammonia-assisted burner using exhaust gas recirculation preheating. Background Art

[0002] Currently, ammonia energy as a zero-carbon fuel has received widespread attention. However, the high ignition energy and low laminar combustion velocity of ammonia have affected the energy utilization of ammonia. In order to ensure stable ignition and combustion of ammonia, ammonia is often mixed with highly reactive gases (such as hydrogen) to improve the combustion characteristics of ammonia.

[0003] The higher the temperature of the reaction gas, the easier it is to react. By preheating the reaction mixture, the probability of stable ignition and combustion of the mixture can be greatly increased. Note that the exhaust gas at the outlet of the combustion chamber has a high temperature and contains a large amount of heat energy that can be used. This part of the waste heat can be recovered and fully utilized.

[0004] Some scholars have successfully stabilized the ammonia / air flame using a stagnant flame structure: the flame spreads and extends in an extremely narrow channel, reaching a dynamic equilibrium state, allowing the mixture to continue to burn. Summary of the invention

[0005] In combination with the above background technology, the present invention provides a staged ammonia-assisted burner using exhaust gas recirculation preheating, which makes the ignition and combustion process of the ammonia mixture easier and more stable.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions.

[0007] A staged ammonia-assisted burner using exhaust gas recirculation preheating comprises a reaction gas pipeline, an exhaust gas pipeline, a combustion pipeline, a secondary air pipeline, a cyclone, an air distributor, an igniter and a flame arrester; The combustion duct is a U-shaped symmetrical U-shaped duct with two openings at both ends, and the end of the duct is bent inward; the secondary air duct has the same shape as the combustion duct and the length of each duct is greater, the secondary air duct is a U-shaped symmetrical U-shaped duct with two openings at both ends, the end of the secondary air duct is bent inward, and the secondary air duct is arranged on the periphery of the combustion duct; The end point p of the reaction gas pipeline is connected to the combustion pipeline at the center of the combustion pipeline, the middle point q of the reaction gas pipeline is connected to the secondary air pipeline at the center of the secondary air pipeline, and the starting point m of the reaction gas pipeline is connected to the exhaust gas pipeline at the end of the exhaust gas pipeline (that is, the intersection point of the reaction gas pipeline and the combustion pipeline is point p, the intersection point of the reaction gas pipeline and the secondary air pipeline is point q, and the intersection point of the reaction gas pipeline and the exhaust gas pipeline is point m); The cyclone is arranged between the starting point m and the middle point q in the reaction gas pipeline, the air distributor is arranged at the middle point q in the reaction gas pipeline, and the igniter is arranged at the end point p in the combustion pipeline; The flame arrester includes a combustion duct flame arrester, a first secondary air duct flame arrester and a second secondary air duct flame arrester. The combustion duct flame arrester is arranged at the intersection of the reaction gas duct and the combustion duct, and the first secondary air duct flame arrester and the second secondary air duct flame arrester are respectively arranged at the ends of both sides of the secondary air duct.

[0008] In the above technical solution, the distance between the intersection A of the extension lines of the pipe ends on both sides of the combustion pipe and the intersection B of the extension lines of the pipe ends on both sides of the secondary air pipe is less than the limit distance of flame diffusion, so that the flame at the intersection A can ignite the intersecting secondary air gas at the intersection B.

[0009] In the above technical solution, the reaction gas in the reaction gas pipeline is a mixture of ammonia, hydrogen and air, wherein the volume fraction ratio of ammonia to hydrogen is 7:3.

[0010] In the above technical solution, the igniter includes a main body cylinder and discharge ports, the number of the discharge ports is 3, and the discharge ports are evenly distributed on the main body cylinder.

[0011] In the above technical solution, the exhaust gas pipe is connected to the outlet of the combustion chamber, and the exhaust gas pipe contains post-combustion products with residual heat, the main components of which are nitrogen, nitrogen oxides, and very small amounts of ammonia and hydrogen.

[0012] In the above technical solution, the cyclone includes blades driven to rotate with the center as a circle, the number of the blades is 9, and the inclination angle of the blades is 40 degrees.

[0013] In the above technical solution, the air separator delivers 10-30% volume of the uniform mixed gas flow into the combustion duct, and delivers the remaining uniform mixed gas flow into the secondary air duct.

[0014] In the above technical solution, the flame arrester includes a main body and a channel arranged on the main body and penetrating in the radial direction, and the diameter of the channel is smaller than the quenching distance of the flame.

[0015] Beneficial effects: The present invention proposes a staged ammonia-assisted burner using exhaust gas recirculation preheating, including a reaction gas pipeline, an exhaust gas pipeline, a combustion pipeline, a secondary air pipeline, a cyclone, an air distributor, an igniter and a flame arrester; when the present invention is working, after exhaust gas recirculation preheating, a small part of the reaction gas is sent to the combustion pipeline by the air distributor, and after ignition by the igniter, a stable stagnant flame is formed, and a large amount of mixed gas from the secondary air pipeline is ignited. The present invention is used to solve the problem that ammonia is difficult to ignite and burn stably. At the same time, the present invention has a simple structure, is easy to manufacture, and has strong component adaptability, which promotes the energy utilization of ammonia. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of a staged ammonia-assisted burner using exhaust gas recirculation preheating according to the present invention; Figure 2 It is a structural schematic diagram of the flame arrester in the present invention; Figure 3 It is a structural schematic diagram of the igniter in the present invention.

[0017] In the figure: 1 is a reaction gas pipeline, 2 is an exhaust gas pipeline, 3 is a cyclone, 4 is an air distributor, 5 is a combustion pipeline flame arrester, 6 is an igniter, 7 is a combustion pipeline, 8 is a secondary air pipeline, 9 is a first secondary air pipeline flame arrester, 10 is a second secondary air pipeline flame arrester, 11 is a main body, 12 is a channel, 13 is a main body cylinder, and 14 is a discharge port. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Example A staged ammonia-assisted burner using exhaust gas recirculation preheating, comprising a reaction gas pipeline 1, an exhaust gas pipeline 2, a combustion pipeline 7, a secondary air pipeline 8, a cyclone 3, an air distributor 4, an igniter 6 and a flame arrester; The combustion pipe 7 is a U-shaped pipe with two ends opening in a central symmetry, and the end of the pipe is bent inward; the secondary air pipe 8 has the same shape as the combustion pipe 7 but is larger in size, and the secondary air pipe 8 is also a U-shaped pipe with two ends opening in a central symmetry, and the end of the pipe is bent inward, and the secondary air pipe 8 is arranged on the outer periphery of the combustion pipe 7; The intersection point of the reaction gas pipeline 1 and the combustion pipeline 7 is point p, the intersection point of the reaction gas pipeline 1 and the secondary air pipeline 8 is point q, and the intersection point of the reaction gas pipeline 1 and the exhaust gas pipeline 2 is point m; The cyclone 3 is arranged between the point m and the point q in the reaction gas pipeline 1, the air distributor 4 is arranged at the point q in the reaction gas pipeline 1, and the igniter 6 is arranged at the point p in the combustion pipeline 7; The flame arrester includes a combustion duct flame arrester 5, a first secondary air duct flame arrester 9 and a second secondary air duct flame arrester 10. The combustion duct flame arrester 5 is arranged at the intersection of the reaction gas duct 1 and the combustion duct 7, and the first secondary air duct flame arrester 9 and the second secondary air duct flame arrester 10 are respectively arranged at the ends of both sides of the secondary air duct 8.

[0020] like Figure 1 As shown, this embodiment provides a staged ammonia-assisted burner using exhaust gas recirculation preheating, and the volume fraction ratio of ammonia and hydrogen supplied into the reaction gas pipeline 1 is set to 7:3, which ensures that there is enough hydrogen to improve the combustion characteristics of ammonia (laminar combustion speed is increased, ignition delay time is reduced), and at the same time, excessive nitrogen oxides will not be generated.

[0021] like Figure 2 As shown, this embodiment provides a staged ammonia-assisted burner using exhaust gas recirculation preheating. In order to prevent the occurrence of flashback and burning of burner components, flame arresters are installed at the front of the combustion pipe inlet and both ends of the secondary air pipe outlet; the flame arrester includes a main body 11 and a channel 12 arranged on the main body 11 and radially penetrating, and the diameter of the channel 12 is smaller than the quenching distance of the flame; the principle of flame arrester is as follows: the flame arrester is made of refractory material and includes many small channels 12, which allow the mixed gas to flow, but the flashback flame will be diverted into many small flames when it enters the flame arrester; since the heat transfer area of ​​the channel 12 is large, the heat generated by the flame is much smaller than the heat dissipation to the wall of the channel 12, and its temperature drops sharply; when it drops to a certain temperature, the flame will be extinguished in the channel 12.

[0022] like Figure 3 As shown, this embodiment provides a staged ammonia-assisted burner using exhaust gas recirculation preheating, 10-30% volume fraction of mixed gas enters the combustion pipe 7 whose diameter is adjusted to the mixed gas quenching distance, and is discharged by the igniter 6, the igniter 6 includes a main body cylinder 13 and discharge ports 14, the number of the discharge ports 14 is 3, and the discharge ports 14 are evenly arranged on the main body cylinder 13. The mixed gas ignites and a weak but stable stagnant flow flame appears; after full development, the flame sprays out from both ends of the outlet of the combustion pipe 7 and gathers into a medium-sized flame, the outer flame part of which ignites the mixed gas from the secondary air pipe 8, and finally forms a stable large flame.

[0023] The working principle of a staged ammonia-assisted burner using exhaust gas recirculation preheating is as follows: The reaction mixture in the reaction gas pipeline is mixed with the high-temperature exhaust gas in the exhaust gas pipeline for heat exchange, and is fully mixed in the cyclone. A small amount of the mixed gas is then sent to the combustion pipeline through the air separator, and the remaining large amount of the mixed gas is sent to the secondary air pipeline. The mixed reaction gas in the combustion pipeline is ignited by the igniter to form a weak but stable stagnant flow flame, which is fully developed and ejected from both ends of the combustion pipeline outlet. The two small flames merge to form a medium-sized flame. The outer flame part of the medium-sized flame with the highest temperature ignites a large amount of mixed reaction gas ejected from the secondary air pipeline outlet, thereby forming a stable large flame. By stabilizing the flame and gradually expanding the scale, the difficulty of ammonia in ignition and combustion is significantly alleviated.

[0024] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A staged ammonia-assisted burner using exhaust gas recirculation preheating, characterized in that: Including reaction gas pipeline, exhaust gas pipeline, combustion pipeline, secondary air pipeline, cyclone, air distributor, igniter and flame arrester; The combustion duct is a U-shaped symmetrical U-shaped duct with two openings at both ends, and the end of the duct is bent inward; the secondary air duct has the same shape as the combustion duct and the length of each duct is greater, the secondary air duct is a U-shaped symmetrical U-shaped duct with two openings at both ends, the end of the secondary air duct is bent inward, and the secondary air duct is arranged on the periphery of the combustion duct; The end point p of the reaction gas pipeline is connected to the combustion pipeline at the center of the combustion pipeline, the middle point q of the reaction gas pipeline is connected to the secondary air pipeline at the center of the secondary air pipeline, and the starting point m of the reaction gas pipeline is connected to the exhaust gas pipeline at the end of the exhaust gas pipeline; The cyclone is arranged between the starting point m and the middle point q in the reaction gas pipeline, the air distributor is arranged at the middle point q in the reaction gas pipeline, and the igniter is arranged at the end point p in the combustion pipeline; The flame arrester includes a combustion duct flame arrester, a first secondary air duct flame arrester and a second secondary air duct flame arrester. The combustion duct flame arrester is arranged at the intersection of the reaction gas duct and the combustion duct, and the first secondary air duct flame arrester and the second secondary air duct flame arrester are respectively arranged at the ends of both sides of the secondary air duct.

2. The staged ammonia-assisted burner using exhaust gas recirculation preheating according to claim 1 is characterized in that: The distance between the intersection A of the extension lines of the pipe ends on both sides of the combustion pipe and the intersection B of the extension lines of the pipe ends on both sides of the secondary air pipe is less than the limit distance of flame diffusion, so that the flame at the intersection A can ignite the intersecting secondary air gas at the intersection B.

3. The staged ammonia-assisted burner using exhaust gas recirculation preheating according to claim 1 is characterized in that: The reaction gas in the reaction gas pipeline is a mixture of ammonia, hydrogen and air, wherein the volume fraction ratio of ammonia to hydrogen is 7:

3.

4. The staged ammonia-assisted burner using exhaust gas recirculation preheating according to claim 1 is characterized in that: The igniter comprises a main body cylinder and discharge ports, the number of the discharge ports is 3, and the discharge ports are evenly distributed on the main body cylinder.

5. The staged ammonia-assisted burner using exhaust gas recirculation preheating according to claim 1 is characterized in that: The exhaust gas pipeline is connected to the outlet of the combustion chamber, and the exhaust gas pipeline contains post-combustion products with residual heat, the components of which are nitrogen, nitrogen oxides, ammonia and hydrogen.

6. The staged ammonia-assisted burner using exhaust gas recirculation preheating according to claim 1 is characterized in that: The cyclone comprises blades which rotate around the center after being driven, the number of the blades is 9, and the inclination angle of the blades is 40 degrees.

7. The staged ammonia-assisted burner using exhaust gas recirculation preheating according to claim 1 is characterized in that: The air distributor delivers 10-30% of the volume of the uniform mixed gas flow into the combustion duct, and delivers the remaining uniform mixed gas flow into the secondary air duct.

8. The staged ammonia-assisted burner using exhaust gas recirculation preheating according to claim 1 is characterized in that: The flame arrester comprises a main body and a channel arranged on the main body and penetrating in the radial direction, wherein the diameter of the channel is smaller than the quenching distance of the flame.

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