A multi-stage ammonia burner utilizing mild combustion

Abstract

A kind of multistage ammonia gas burner using MILD combustion, including primary combustion structure, tangential air intake structure and secondary combustion structure;Primary combustion structure includes primary ammonia gas intake pipeline, primary ammonia gas intake pipeline is communicated with primary combustion chamber, primary ammonia gas intake pipeline outside is provided with flame stabilizer, the front end surface of flame stabilizer is connected with wind shield, primary combustion chamber is located in the inside of wind shield, realizes MILD combustion;Tangential air intake structure includes air intake pipeline and hydrogen gas intake pipeline, both are connected to the side wall of primary ammonia gas intake pipeline, air and hydrogen are sent into primary ammonia gas intake pipeline and form swirl;Secondary combustion structure includes secondary air blower and secondary ammonia gas intake pipeline, the front end of secondary ammonia gas intake pipeline extends into secondary combustion chamber, secondary combustion chamber is located at the front end of primary combustion chamber and is communicated with primary combustion chamber, secondary air blower generates secondary air and is sent into secondary combustion chamber.The present application can improve combustion efficiency, reduce nitrogen oxides emission.

Description

Technical Field

[0001] This invention belongs to the field of burner technology, and specifically relates to a multi-stage ammonia burner utilizing MILD combustion. Background Technology

[0002] Ammonia contains no carbon and boasts advantages such as high hydrogen density, low production costs, and readily available infrastructure, making it a widely recognized renewable fuel. However, the unstable flame during ammonia combustion and the high emissions of nitrogen oxides hinder its application.

[0003] MILD combustion is a mild combustion mode under low oxygen dilution conditions, characterized by: low reaction rate, low local heat release, uniform heat flow distribution, low peak combustion temperature, extremely low noise, extremely low generation of pollutants such as NOx and CO, increased overall furnace temperature, and enhanced radiative heat transfer.

[0004] Existing ammonia burner technologies include staged combustion, multi-stage swirl, hydrogen incorporation, and flue gas recirculation, among other low-NOx combustion technologies. However, current ammonia burners generally suffer from the following technical problems during use: fuel is rapidly ignited by the high-temperature air and flue gas after injection, resulting in excessively high temperatures near the combustion chamber, leading to excessively high temperatures near the swirl blades and intake pipes. Under the influence of high temperatures and air, the strength of the workpiece is severely reduced, and its service life is significantly shortened. Furthermore, the fuel and air are not mixed evenly, resulting in incomplete combustion and low combustion efficiency. Under different loads, the combustion conditions in the furnace change, causing significant variations in NOx formation. Therefore, existing burners cannot be used for ammonia combustion utilization. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a multi-stage ammonia burner that utilizes MILD combustion to improve combustion efficiency and reduce nitrogen oxide emissions; furthermore, by using this burner, the gas ignition speed is fast, the flame is stable, and the probability of backfire and flameout is reduced.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A multi-stage ammonia burner utilizing MILD combustion is characterized by comprising a primary combustion structure, a tangential air intake structure, and a secondary combustion structure;

[0008] The primary combustion structure includes a primary ammonia gas inlet pipe, which is connected to the primary combustion chamber. A flame stabilizer is installed outside the primary ammonia gas inlet pipe, and a wind shield is connected to the front end of the flame stabilizer. The primary combustion chamber is located inside the wind shield to achieve MILD combustion.

[0009] The tangential air intake structure includes an air intake pipe and a hydrogen intake pipe, which are connected to the side wall of the primary ammonia intake pipe, and air and hydrogen are introduced into the primary ammonia intake pipe to form a swirling flow.

[0010] The secondary combustion structure includes a secondary air blower and a secondary ammonia inlet pipe. The front end of the secondary ammonia inlet pipe extends into the secondary combustion chamber. The secondary combustion chamber is located in front of the primary combustion chamber and is connected to the primary combustion chamber. The secondary air blower generates secondary air and sends it into the secondary combustion chamber.

[0011] In one embodiment, the front end of the primary ammonia inlet pipe is connected to the rear end of the nozzle, the front end of the nozzle is equipped with a nozzle located in the primary combustion chamber along the fuel flow direction, and the nozzle has a tapering shape.

[0012] In one embodiment, the nozzle has a plurality of injection holes arranged in layers along the axial direction of the primary ammonia inlet pipe, forming an angle with the axial direction, and the lowest layer of injection holes is located at the bottom of the nozzle and on the axial direction.

[0013] In one embodiment, the connection points of the air intake pipe and the hydrogen intake pipe with the primary ammonia intake pipe are located in the same circumference, and both the air intake pipe and the hydrogen intake pipe are arranged axially inclined.

[0014] In one embodiment, a swirl impeller is provided between the outer wall of the front end of the wind shield and the inner wall of the burner housing, and the secondary air is formed into swirling air by the swirl impeller and sent into the secondary combustion chamber.

[0015] In one embodiment, the secondary combustion chamber has a gradually widening shape in front of the swirl impeller.

[0016] In one embodiment, the swirl impeller has multiple blades with tilted angles evenly arranged, and secondary air is sent into the secondary combustion chamber through the swirl impeller to form a primary swirl zone.

[0017] In one embodiment, there are multiple secondary ammonia inlet pipes, which are evenly distributed outside the primary ammonia inlet pipe. Each secondary ammonia inlet pipe passes through the flame stabilizer and is arranged symmetrically about the axis.

[0018] In one embodiment, the secondary ammonia inlet pipe adopts a direct nozzle, with the nozzle curving inward at an angle to the axial direction to form a secondary vortex zone.

[0019] In one embodiment, the secondary ammonia inlet pipe is connected to a groove on an axially fixed pipe via a baffle, and the position and length of the secondary ammonia inlet pipe in the secondary combustion chamber are adjusted by moving the baffle at a position on the fixed pipe.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. The burner is a staged burner, which can promote the mixing of gas and air, promote gas combustion, and make the heat load in the combustion chamber more uniform, thereby reducing nitrogen oxide emissions.

[0022] 2. The combustion device incorporates flue gas recirculation technology. After the flue gas is ejected through the nozzle, it flows back to the primary combustion chamber under pressure, which can reduce the gas concentration and achieve MILD combustion, thereby reducing nitrogen oxide emissions.

[0023] 3. A moving device has been introduced into the intake pipe, which can adjust the position of the combustion zone according to changes in airflow, thereby improving combustion efficiency. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the present invention.

[0025] Figure 2 This is a schematic diagram of the combination of the first-stage combustion structure and the tangential air intake structure of the present invention.

[0026] Figure 3 This is a schematic diagram of the structure of the secondary ammonia gas inlet pipe on the flame stabilizer plate of the present invention.

[0027] Figure 4 This is a schematic diagram of the structure of the fixed pipe of the present invention. Detailed Implementation

[0028] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings and examples.

[0029] like Figure 1 and Figure 2 As shown, this invention is a multi-stage ammonia burner utilizing MILD combustion, comprising a primary combustion structure, a tangential air intake structure, and a secondary combustion structure, or it may consist only of a primary combustion structure, a tangential air intake structure, and a secondary combustion structure. The aforementioned structures can be arranged within the burner housing 6.

[0030] In this invention, the flow direction of fuel or air is used as the reference direction, and the flow direction is defined as "from back to front". In this invention, the axial direction refers to the axial direction of the burner, which is parallel to or consistent with the main flow direction of the fuel.

[0031] The front end of the multi-stage swirl burner of this invention is connected to the combustion chamber, while the rear end is equipped with an air inlet device and a gas valve group.

[0032] In this invention, the primary combustion structure mainly includes a primary ammonia inlet pipe 1, which is connected to a primary combustion chamber 7. A flame stabilizer 10 is installed outside the primary ammonia inlet pipe 1, and a cylindrical wind shield 5 is connected to the front end of the flame stabilizer 10. The primary combustion chamber 7 is located inside the wind shield 5. The wind shield 5 isolates air, creating a negative pressure zone during combustion, which helps to generate backflow and draw back some of the combustion flue gas. The drawn-back flue gas mixes with the fuel, reducing the oxygen concentration and forming diffuse combustion, achieving MILD combustion, slowing down the combustion reaction, lowering the flame temperature, making the combustion temperature distribution more uniform, and reducing nitrogen oxide emissions. Simultaneously, it provides heat to the secondary combustion chamber 14, achieving ignition. Clearly, an ignition device for igniting the combustion gas is installed inside the primary combustion chamber 7.

[0033] The tangential air intake structure mainly includes an air intake pipe 2 and a hydrogen intake pipe 13. The air intake pipe 2 and the hydrogen intake pipe 13 are connected to the side wall of the primary ammonia intake pipe 1, and air and hydrogen are introduced into the primary ammonia intake pipe 1 to form a swirling flow. Obviously, the connection is best tangential.

[0034] The secondary combustion structure mainly includes a secondary air blower 8 and a secondary ammonia inlet pipe 9. The front end of the secondary ammonia inlet pipe 9 extends into the secondary combustion chamber 14. The secondary combustion chamber 14 is located in front of and connected to the primary combustion chamber 7. The secondary air blower 8 generates secondary air and sends it into the secondary combustion chamber 14. Obviously, the primary combustion chamber 7 and the secondary combustion chamber 14 can be two parts of a single integrated area.

[0035] In one specific structure of the present invention, the primary combustion structure further includes a nozzle 3, a spray nozzle 4, etc. The front end of the primary ammonia inlet pipe 1 is connected to the rear end of the nozzle 3. Furthermore, the nozzle 3 has a tapering shape along the fuel flow direction. By changing its cross-section and reducing pressure, the ammonia-primary air mixture is accelerated to achieve a high-speed jet. The spray nozzle 4 is installed at the front end of the nozzle 3. Obviously, the spray nozzle 4 is located inside the primary combustion chamber 7 and is used to input a high-speed airflow into the primary combustion chamber 7.

[0036] For example, the nozzle 4 has multiple injection holes, which are arranged in layers along the axial direction of the primary ammonia inlet pipe 1 and at an angle to the axial direction. The bottom layer of injection holes is located at the bottom of the nozzle 4 and preferably on the axial direction. Each injection hole is used to inject an ammonia-air mixture into the primary combustion chamber 7. The nozzle 4 can also control the amount of gas released, ensure a certain velocity of the jet, and form multiple combustion points, making the combustion in the primary combustion chamber 7 more uniform and stable, thereby improving combustion efficiency; it can also prevent flame backflow.

[0037] In one specific structure of the present invention, the number of air intake pipes 2 and hydrogen intake pipes 13 is set as needed. Figure 2In the embodiment shown, there are three air intake pipes 2 and one hydrogen intake pipe 13. The connection points of the air intake pipes 2 and the hydrogen intake pipe 13 with the primary ammonia intake pipe 1 are in the same circumferential direction. Both the air intake pipes 2 and the hydrogen intake pipe 13 are arranged axially inclined to deliver air and hydrogen in a tangential manner as much as possible, so as to mix with the ammonia in the primary ammonia intake pipe 1 to form a swirling flow.

[0038] In one specific structure of the present invention, a swirl impeller 11 is disposed between the outer wall near the front end of the wind shield 5 and the inner wall of the burner housing 6. Secondary air passes through the swirl impeller 11 to form swirling air, which is then sent into the secondary combustion chamber 14. For example, in the present invention, the secondary combustion chamber 14 has a gradually widening shape in front of the swirl impeller 11, i.e., a diffuser. After entering the secondary combustion chamber 14, the secondary air diffuses rapidly.

[0039] Specifically, the swirl impeller 11 has multiple blades with inclined angles evenly arranged. Air is drawn in by the secondary air blower 8, and the swirl impeller 11 gives the air a rotational force, causing the air to enter in a spiral shape, forming a primary swirl zone at the secondary air outlet.

[0040] The secondary ammonia inlet pipe 9 of this invention adopts a direct-nozzle structure, with the nozzle converging inwards to form a certain angle with both the axial and radial directions, providing a radial force to the ammonia gas. This creates a secondary swirling zone at the secondary ammonia outlet, where the swirling secondary air and swirling secondary ammonia gas mix and burn. The secondary swirling zone should be roughly located in the initial section of the primary MILD combustion zone to achieve stable combustion at a high flow rate, prevent flame backflow, and ensure safety. For example, there are multiple secondary ammonia inlet pipes 9, evenly distributed circumferentially around the outside of the primary ammonia inlet pipe 1. Each secondary ammonia inlet pipe 9 passes through the flame stabilizer 10 and is arranged symmetrically about the axis, as shown below. Figure 3 As shown.

[0041] In one specific structure of the present invention, to facilitate combustion adjustment, the secondary ammonia inlet pipe 9 is connected to a groove on the axially fixed pipe 12 via a baffle. The position and length of the secondary ammonia inlet pipe 9 in the secondary combustion chamber 14 are adjusted by moving the baffle at its position on the fixed pipe 12. The structure of the fixed pipe 12 is as follows: Figure 4 As shown, grooves of different depths are provided on it, and there are symmetrical baffles protruding on the outer wall of each secondary ammonia gas inlet pipe 9. By matching the baffles with grooves of different depths, the position of the secondary ammonia gas inlet pipe 9 in the secondary combustion chamber 14 can be adjusted, thereby realizing the movement of the combustion zone with the gas flow.

[0042] In the above burner, the primary combustion zone and the secondary combustion zone work together to achieve stable MILD combustion, reduce the occurrence of local high temperatures, avoid flame backflow, reduce pollutant emissions, and effectively improve gas efficiency.

[0043] The above embodiments are merely illustrative of the present invention and are not intended to limit the invention. Any changes or modifications to the above embodiments based on the technical essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A multi-stage ammonia burner utilizing MILD combustion, characterized in that, It includes a primary combustion structure, a tangential intake structure, and a secondary combustion structure; The primary combustion structure includes a primary ammonia gas inlet pipe (1), which is connected to the primary combustion chamber (7). A flame stabilizer plate (10) is installed outside the primary ammonia gas inlet pipe (1), and the front end of the flame stabilizer plate (10) is connected to a wind shield (5). The primary combustion chamber (7) is located inside the wind shield (5) to achieve MILD combustion. The tangential air intake structure includes an air intake pipe (2) and a hydrogen intake pipe (13). The air intake pipe (2) and the hydrogen intake pipe (13) are connected to the side wall of the primary ammonia intake pipe (1) to introduce air and hydrogen into the primary ammonia intake pipe (1) and form a swirling flow. The secondary combustion structure includes a secondary air blower (8) and a secondary ammonia gas inlet pipe (9). The front end of the secondary ammonia gas inlet pipe (9) extends into the secondary combustion chamber (14). The secondary combustion chamber (14) is located at the front end of the primary combustion chamber (7) and is connected to the primary combustion chamber (7). The secondary air blower (8) generates secondary air and sends it into the secondary combustion chamber (14).

2. The multi-stage ammonia burner utilizing MILD combustion according to claim 1, characterized in that, The front end of the primary ammonia inlet pipe (1) is connected to the rear end of the nozzle (3). A nozzle (4) is installed at the front end of the nozzle (3). The nozzle (4) is located in the primary combustion chamber (7) along the fuel flow direction. The nozzle (3) has a tapering shape.

3. The multi-stage ammonia burner utilizing MILD combustion according to claim 2, characterized in that, The nozzle (4) has multiple injection holes arranged in layers along the axial direction of the primary ammonia gas inlet pipe (1), with an angle to the axial direction, and the lowest layer of injection holes is located at the bottom of the nozzle (4) and on the axial direction.

4. The multi-stage ammonia burner utilizing MILD combustion according to claim 1, characterized in that, The connection points of the air intake pipe (2) and the hydrogen intake pipe (13) with the primary ammonia intake pipe (1) are located in the same circumference, and the air intake pipe (2) and the hydrogen intake pipe (13) are both arranged with axial inclination.

5. The multi-stage ammonia burner utilizing MILD combustion according to claim 1, characterized in that, A swirl impeller (11) is provided between the outer wall of the front end of the wind shield (5) and the inner wall of the burner housing (6). The secondary air is formed into swirling air by the swirl impeller (11) and sent into the secondary combustion chamber (14).

6. The multi-stage ammonia burner utilizing MILD combustion according to claim 5, characterized in that, The secondary combustion chamber (14) is gradually widening in front of the swirl impeller (11).

7. The multi-stage ammonia burner utilizing MILD combustion according to claim 5, characterized in that, The swirl impeller (11) has multiple blades with inclined angles evenly arranged. Secondary air is sent into the secondary combustion chamber (14) through the swirl impeller (11) to form a primary swirl zone.

8. The multi-stage ammonia burner utilizing MILD combustion according to claim 1, characterized in that, There are multiple secondary ammonia inlet pipes (9), which are evenly distributed on the outside of the primary ammonia inlet pipe (1). Each secondary ammonia inlet pipe (9) passes through the flame stabilizer plate (10) and is arranged symmetrically about the axis.

9. The multi-stage ammonia burner utilizing MILD combustion according to claim 1 or 8, characterized in that, The secondary ammonia inlet pipe (9) adopts a direct nozzle, and the nozzle converges inward to form an angle with the axial direction, forming a secondary vortex zone.

10. The multi-stage ammonia burner utilizing MILD combustion according to claim 1, characterized in that, The secondary ammonia inlet pipe (9) is connected to the groove on the axial fixed pipe (12) by a baffle. The position and length of the secondary ammonia inlet pipe (9) in the secondary combustion chamber (14) can be adjusted by moving the baffle on the fixed pipe (12).

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