A staged ammonia-assisted burner using exhaust gas recirculation preheating

Abstract

The present invention provides a staged ammonia-assisted burner that utilizes exhaust gas recirculation for preheating. This burner, belonging to the field of burners, includes a reaction gas duct, an exhaust gas duct, a combustion duct, a secondary air duct, a cyclone, an air distributor, an igniter, and a flame arrester. The cyclone is installed at the rear of the intersection of the reaction gas duct and the exhaust gas duct, and the air distributor is installed at the intersection of the reaction gas duct and the secondary air duct. A flame arrester and an igniter are installed at the front and rear of the combustion duct inlet, respectively. A flame arrester is installed at each end of the secondary air duct outlet. After exhaust gas recirculation for preheating, a small portion of the reaction gas is fed into the combustion duct by the air distributor. Ignition by the igniter forms a stable, stagnant flame, which then ignites a large amount of mixed gas from the secondary air duct. This invention addresses the difficulty of stable ammonia ignition and combustion. Furthermore, the invention has a simple structure, is easy to manufacture, and has strong component adaptability, promoting the energy utilization of ammonia.

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] Ammonia is currently attracting widespread attention as a zero-carbon fuel. However, its high ignition energy and low laminar combustion velocity hinder its potential energy utilization. To ensure stable ignition and combustion, ammonia is often blended with highly reactive gases (such as hydrogen) to improve its combustion characteristics.

[0003] The higher the temperature of the reaction gases, the easier it is to react. Preheating the reaction mixture significantly increases the probability of stable ignition and combustion. Note that the exhaust gases at the combustion chamber outlet are at a relatively high temperature and contain a large amount of usable heat energy, which 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 includes 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;

[0008] The combustion duct is a U-shaped symmetrical U-shaped duct with both ends open, 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 both ends open, and the end of the secondary air duct is bent inward. The secondary air duct is arranged on the periphery of the combustion duct;

[0009] 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);

[0010] The cyclone is arranged between the starting point m and the middle point q in the reaction gas pipeline, the air separator 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;

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] In the above technical solution, the exhaust gas pipe is connected to the combustion chamber outlet, 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.

[0016] In the above technical solution, the cyclone includes blades that are 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.

[0017] In the above technical solution, the air separator sends 10-30% of the volume of the uniform mixed gas flow into the combustion duct, and sends the remaining uniform mixed gas flow into the secondary air duct.

[0018] In the above technical solution, the flame arrester includes a main body and a channel arranged on the main body and passing through in the radial direction, and the diameter of the channel is smaller than the quenching distance of the flame.

[0019] Beneficial effects:

[0020] This invention proposes a staged ammonia-assisted burner that utilizes exhaust gas recirculation and preheating. The burner 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. During operation, after exhaust gas recirculation and preheating, a small portion of the reaction gas is fed into the combustion pipeline by the air distributor. Ignition by the igniter forms a stable, stagnant flame, which then ignites a large amount of mixed gas from the secondary air pipeline. This invention addresses the difficulty of stable ammonia ignition and combustion. Furthermore, it boasts a simple structure, ease of manufacture, and strong component adaptability, promoting the energy utilization of ammonia. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic structural diagram of a staged ammonia-assisted burner using exhaust gas recirculation preheating according to the present invention;

[0022] Figure 2 It is a structural schematic diagram of the flame arrester in the present invention;

[0023] Figure 3 It is a structural schematic diagram of the igniter in the present invention.

[0024] In the figure: 1 is the reaction gas pipeline, 2 is the exhaust gas pipeline, 3 is the cyclone, 4 is the air distributor, 5 is the combustion pipeline flame arrester, 6 is the igniter, 7 is the combustion pipeline, 8 is the secondary air pipeline, 9 is the first secondary air pipeline flame arrester, 10 is the second secondary air pipeline flame arrester, 11 is the main body, 12 is the channel, 13 is the main body cylinder, and 14 is the discharge port. DETAILED DESCRIPTION

[0025] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying 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 making creative efforts shall fall within the scope of protection of the present invention.

[0026] Example

[0027] A staged ammonia-assisted burner using exhaust gas recirculation preheating comprises 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;

[0028] The combustion duct 7 is a U-shaped symmetrical U-shaped duct with both ends open, and the end of the duct is bent inward. The secondary air duct 8 has the same shape as the combustion duct 7 but is larger in size. The secondary air duct 8 is also a U-shaped symmetrical U-shaped duct with both ends open, and the end of the duct is bent inward. The secondary air duct 8 is arranged on the outer periphery of the combustion duct 7.

[0029] 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;

[0030] The cyclone 3 is arranged between points m and q in the reaction gas pipeline 1, the air separator 4 is arranged at point q in the reaction gas pipeline 1, and the igniter 6 is arranged at point p in the combustion pipeline 7;

[0031] 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.

[0032] 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. This ensures that there is sufficient hydrogen to improve the combustion characteristics of ammonia (increase the laminar combustion speed and reduce the ignition delay time) without generating excessive nitrogen oxides.

[0033] 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 backfire and burning of burner components, flame arresters are installed at the front of the combustion pipe inlet and at both ends of the secondary air duct 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 its flame arresting is as follows: the flame arrester is made of refractory material and contains many small channels 12, which allow the mixed gas to flow, but the backfired 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.

[0034] like Figure 3As shown, this embodiment provides a staged ammonia-assisted burner using exhaust gas recirculation preheating. A mixed gas with a volume fraction of 10-30% enters a combustion pipe 7, the diameter of which is adjusted to the quenching distance of the mixed gas. Upon discharge from an igniter 6, which includes a main cylindrical body 13 and three discharge ports 14 evenly distributed on the main cylindrical body 13, the mixed gas ignites, forming a weak but stable stagnant flow flame. After full development, the flame ejects from both ends of the outlet of the combustion pipe 7 and converges into a medium-sized flame. The outer flame portion of the flame ignites the mixed gas from the secondary air duct 8, ultimately forming a large, stable flame.

[0035] The working principle of a staged ammonia-assisted burner using exhaust gas recirculation preheating is as follows:

[0036] 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. After full development, the flame is ejected from both ends of the combustion pipeline outlet. The two small flames merge to form a medium-sized flame. The outer flame part with the highest temperature of the medium flame 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 difficulties of ammonia in ignition and combustion are significantly alleviated.

[0037] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily 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 is not intended to be limited to the embodiments shown herein, but is intended to be accorded 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 by: 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 both ends open, 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 both ends open, and the end of the secondary air duct is bent inward. 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 separator 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, characterized in that: The distance between the intersection A of the extension lines of the ends of the pipes on both sides of the combustion pipe and the intersection B of the extension lines of the ends of the pipes 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, 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 with exhaust gas recirculation preheating according to claim 1, characterized in that: 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.

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

6. The staged ammonia-assisted burner using exhaust gas recirculation preheating according to claim 1, characterized in that: The cyclone includes blades that 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, characterized in that: The air distributor sends 10-30% of the volume of the uniform mixed gas flow into the combustion pipe, and sends the remaining uniform mixed gas flow into the secondary air pipe.

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

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