A low-nitrogen ammonia coal stable combustion swirl burner

Abstract

A low-NOx ammonia-coal stable combustion swirl burner relates to the field of clean combustion of coal with low carbon and low NOx. This invention addresses the problems of ammonia slip and high NOx emissions in existing ammonia-coal co-combustion technologies. In this invention, a primary air / pulverized coal duct is fitted onto a central NH3 duct, forming a primary air channel between them. An outer NH3 duct is fitted onto the primary air / pulverized coal duct, forming an NH3 channel between them. An inner secondary air duct is fitted onto the outer NH3 duct, forming an inner secondary air channel between them. An outer secondary air duct is fitted onto the inner secondary air duct, forming an outer secondary air channel between them. Tangential and axial blades are respectively installed in the inner and outer secondary air channels. This invention is used for pulverized coal swirl combustion.

Description

Technical Field

[0001] This invention relates to a burner, specifically a low-NOx ammonia coal stable combustion swirl burner, belonging to the field of low-carbon and low-NOx clean combustion of coal. Background Technology

[0002] Ammonia, as an excellent carbon-free fuel, has attracted widespread attention for its blending with coal. However, the application of ammonia-coated coal combustion also presents technical challenges. First, the laminar combustion rate of NH3 is much slower than other gaseous fuels (such as H2, CH4, and syngas), indicating poor combustion characteristics. NH3 requires higher activation energy for ignition, while the heat released during combustion is relatively low. Second, NOx emissions are another major challenge in NH3 combustion. The mass fraction of nitrogen in NH3 molecules exceeds 82%, which can lead to the formation of large amounts of fuel-type nitrogen oxides. Therefore, to achieve the engineering application of ammonia-coal co-combustion in power plant boilers, it is essential to fully understand the combustion and NOx emission characteristics of NH3 and to conduct targeted research on combustion enhancement and NOx control measures.

[0003] As a fundamental regulating energy source, coal-fired power plays a crucial role in load flexibility regulation. Therefore, in order to enable ammonia-coal co-firing in coal-fired boilers without major modifications, it is necessary to develop low-carbon, low-NOx swirl combustion technology based on ammonia-coal co-firing, suitable for flexible peak-shaving processes.

[0004] Research on ammonia as a low-carbon fuel is still in its early stages globally. In coal-ammonia co-combustion processes, incomplete combustion of ammonia leads to its escape from the boiler outlet, releasing ammonia into the environment. Furthermore, ammonia contains 82% nitrogen, resulting in NOx emissions in the thousands of ppm range. The NOx generated during combustion is highly sensitive to atmospheric conditions, contributing to high NOx emissions. The problems of ammonia escape and high NOx emissions associated with ammonia-coal co-combustion technology remain unresolved.

[0005] In summary, existing ammonia-coal co-firing technology suffers from problems such as ammonia slip and high NOx emissions. Summary of the Invention

[0006] The purpose of this invention is to address the problems of ammonia slip and high NOx emissions in existing ammonia-coal co-fired technologies. Therefore, it provides a low-NOx ammonia-coal stable combustion swirl burner, which is a low-carbon, low-NOx swirl combustion technology suitable for flexible peak-shaving processes in ammonia-coal co-fired combustion.

[0007] The technical solution of this invention is as follows: A low-nitrogen ammonia coal stable combustion swirl burner includes a central NH3 pipe through which NH3 is introduced. It also includes a primary air / pulverized coal pipe, an outer NH3 pipe, an inner secondary air pipe, an outer secondary air pipe, tangential blades, and a second axial blade. The primary air / pulverized coal pipe is fitted onto the central NH3 pipe, forming a primary air channel between them. The outer NH3 pipe is fitted onto the primary air / pulverized coal pipe, forming an NH3 channel between them. The inner secondary air pipe is fitted onto the outer NH3 pipe, forming an inner secondary air channel between them. The outer secondary air pipe is fitted onto the inner secondary air pipe, forming an outer secondary air channel between them. The tangential blades and the second axial blade are respectively installed on the inner and outer secondary air channels. The inner sides of the primary air / pulverized coal pipe and the outer NH3 pipe are provided with a tapering structure, achieving sequential ignition and staged combustion through outer ammonia, middle coal, and central ammonia.

[0008] Furthermore, the closing angle of the primary air pulverized coal pipeline is the same as the closing angle of the outer NH3 pipeline.

[0009] Furthermore, the outer NH3 pipe includes a pipe body, a third pipe body, a first adjustable baffle, and a second adjustable baffle. Multiple openings are evenly distributed on the outer circumference of the pipe body. The first adjustable baffle is installed on the inner end face of the pipe body and is parallel to the closing point of the primary air pulverized coal pipe. The second adjustable baffle is installed on the outer end face of the opening. The third pipe body is fitted onto the pipe body, and a reflux annular cavity is formed between the third pipe body and the pipe body.

[0010] Preferably, both the first adjustable baffle and the second adjustable baffle are annular baffles.

[0011] Preferably, the cross-sectional shape of the first adjustable baffle is a right triangle, and the cross-sectional shape of the second adjustable baffle is a rectangle.

[0012] Furthermore, it also includes a reflux generator, which is installed on the right end face of the tube body.

[0013] Furthermore, the diameter of the opening side of the internal and external secondary air ducts gradually increases.

[0014] Furthermore, a gap is left between the main tube and the third tube.

[0015] Preferably, the tangential blade and the second axial blade are mounted on the same radial plane.

[0016] Furthermore, the area formed between the outer side of the first adjustable baffle and the inner wall of the pipe is a low-pressure zone.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. This invention uses NH3 fuel blended with coal for combustion, which can effectively reduce CO2 emissions. The utilization of ammonia fuel is of great value in promoting the development of low-carbon energy. As a form of chemical energy storage, it can absorb surplus intermittent renewable energy sources such as wind and solar power, promoting the development and utilization of renewable energy. As a chemical fuel with high energy density, it is easy to store and transport, which can promote the realization of large-scale, long-term storage and long-distance, cross-regional transportation of renewable energy. The knowledge, technology and facilities for storage, transportation and disposal are mature and applicable to different application scenarios.

[0019] 2. The low-NOx ammonia-coal co-combustion technology provided by this invention uses a staged combustion method of sequential ignition of outer layer ammonia → middle layer coal → central ammonia, which elongates the flame, avoids local high-temperature zones, and reduces the NOx formation rate.

[0020] 3. The enhanced stable combustion and low NOx ammonia-coal co-combustion technology organization method provided by the present invention can achieve high-efficiency, low-NOx, and stable operation with a large proportion of ammonia by establishing a combustion organization mechanism with controllable high-temperature flue gas recirculation, staged combustion of outer layer ammonia-middle layer coal-center ammonia, and multi-field synergy.

[0021] 4. The device system provided by this invention, through the setting of a contraction structure, forms a high-speed jet of primary air and outer NH3 channel inside the burner, creating a low-pressure zone at the root of the jet. Under the action of pressure difference, the high-temperature flue gas at the burner outlet flows through the recirculation annulus to the root of the outer NH3 channel. The high-temperature recirculation, under the entrainment of the high-speed jet of outer NH3, mixes with it and begins to heat the outer NH3 gas flow. After the outer NH3 gas flow is heated to above the ignition point (650°C), oxygen is supplied by the inner primary air, and stable combustion begins. The recirculation power of the high-temperature flue gas is provided by the high-speed jet under the action of the contraction structure, thus its self-heating and stable combustion capability is outstanding.

[0022] 5. The central and outer NH3 channels provided by this invention allow for flexible control of the NH3 flow rate in each channel. Stable combustion can be maintained under different load conditions by adjusting the NH3 flow rate in the central and outer NH3 channels. This enables stable co-combustion of low-NOx ammonia coal under flexible peak-shaving operation.

[0023] 6. The movable slider provided by the present invention can flexibly control the flow rate of the outer layer of NH3 and the flow rate in the reflux chamber by moving the slider, so as to ensure stable co-firing of low NOx ammonia coal under flexible peak-shaving operation.

[0024] 7. The ammonia-coal co-combustion technology provided by this invention can achieve low NOx emissions from ammonia-coal co-combustion, avoiding the high cost of redesigning and installing a new combustion system.

[0025] 8. The device system provided by this invention will solve the problem of stable combustion and efficient burnout with ammonia in large proportions, which has not yet been achieved in current industrial applications. The shape memory alloy used for the tangential and axial blades in the inner and outer secondary channels has advantages such as shape memory effect, superelasticity, good corrosion resistance, and mechanical properties. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall structure of the low-nitrogen ammonia coal stable combustion swirl burner of the present invention.

[0027] Figure 2 yes Figure 1 Sectional view along AA.

[0028] Figure 3 This is a schematic diagram of the combustion organization method of the present invention. Detailed Implementation

[0029] Specific implementation method one: Combining Figures 1 to 2 This embodiment describes a central NH3 duct 1 through which NH3 is introduced. It also includes a primary air / pulverized coal duct 2, an outer NH3 duct 3, an inner secondary air duct 4, an outer secondary air duct 5, tangential blades 6, and a second axial blade 7.

[0030] A primary air pulverized coal pipe 2 is fitted onto the central NH3 pipe 1, forming a primary air channel between the primary air pulverized coal pipe 2 and the central NH3 pipe 1. An outer NH3 pipe 3 is fitted onto the primary air pulverized coal pipe 2, forming an NH3 channel between the outer NH3 pipe 3 and the primary air pulverized coal pipe 2. An inner secondary air pipe 4 is fitted onto the outer NH3 pipe 3, forming an inner secondary air channel between the inner secondary air pipe 4 and the outer NH3 pipe 3. An outer secondary air pipe 5 is fitted onto the inner secondary air pipe 4, forming an outer secondary air channel between the outer secondary air pipe 5 and the inner secondary air pipe 4. A tangential blade 6 and a second axial blade 7 are respectively installed on the inner secondary air channel and the outer secondary air channel.

[0031] The inner sides of the primary air pulverized coal pipeline 2 and the outer NH3 pipeline 3 are equipped with a tapering structure 9, which enables sequential ignition and staged combustion through the outer layer ammonia, the middle layer coal and the center ammonia.

[0032] This invention proposes a novel approach to enhance stable combustion and reduce NOx emissions through ammonia-coal co-combustion, aiming to achieve clean combustion with high NH3 blending ratios. The invention discloses a low-carbon, low-NOx swirl combustion technology based on ammonia-coal co-combustion, suitable for flexible peak-shaving processes.

[0033] The process flow of this invention involves the primary air and outer NH3 channel forming a high-speed jet inside the burner through a constriction structure, creating a low-pressure zone at the jet root. Under the pressure difference, the high-temperature flue gas from the burner outlet flows through the recirculation annular cavity to the root of the outer NH3 channel. The high-temperature recirculation, under the influence of the high-speed outer NH3 jet, mixes with the NH3, initiating the heating of the outer NH3 gas flow. After the outer NH3 gas flow is heated to above its ignition point (650°C), oxygen is supplied from the inner primary air, initiating stable combustion. The outer NH3 gas flow continuously mixes with the primary air-coal mixture. Under the exothermic combustion of the outer NH3, the mixed gas flow heats up and ultimately ignites the pulverized coal in the primary air. The primary air (coal mixture) flow is then drawn in by the high-speed central NH3 gas flow, causing the primary air (coal mixture) to diffuse and mix with the central NH3 gas flow, ultimately igniting the central NH3.

[0034] Specific Implementation Method Two: Combining Figures 1 to 2 In this embodiment, the closing angle of the primary air pulverized coal pipeline 2 is the same as the closing angle of the outer NH3 pipeline 3.

[0035] This configuration ensures that the primary air and outer NH3 channels form a high-speed jet inside the burner through the constriction structure, creating a low-pressure zone at the jet root. Other components and connections are the same as in Specific Implementation Method 1.

[0036] Specific implementation method three: Combining Figures 1 to 2 This embodiment describes an outer NH3 pipe 3 comprising a pipe body 3-3, a third pipe body 3-5, a first adjustable baffle 3-1, and a second adjustable baffle 3-2.

[0037] Multiple openings 3-4 are evenly distributed on the outer circumference of the pipe body 3-3. The first adjustable baffle 3-1 is installed on the inner end face of the pipe body 3-3 and is parallel to the closing end of the primary air pulverized coal pipeline 2. The second adjustable baffle 3-2 is installed on the outer end face of the opening 3-4. The third pipe body 3-5 is fitted onto the pipe body 3-3, and a return flow annular cavity 8 is formed between the third pipe body 3-5 and the pipe body 3-3.

[0038] With this configuration, the radial velocity of the outer NH3 airflow can be flexibly adjusted via the first adjustable baffle 3-1 to create a reasonable mixing pattern of outer ammonia → middle coal → central ammonia airflow. The high-temperature reflux flow to the root of the outer NH3 channel can be flexibly adjusted via the second adjustable baffle 3-2 to create a suitable temperature in the outer NH3 combustion zone, preventing excessively high or low temperatures. Other components and connections are the same as in Specific Implementation Method Two.

[0039] Specific implementation method four: Combination Figures 1 to 2 In this embodiment, both the first adjustable baffle 3-1 and the second adjustable baffle 3-2 are annular baffles.

[0040] This configuration ensures a tight fit with the reflux ring cavity 8, resulting in excellent sealing. Other components and connections are the same as in specific implementation method three.

[0041] Specific Implementation Method Five: Combining Figures 1 to 2 In this embodiment, the first adjustable baffle 3-1 has a right-angled triangle cross-sectional shape, and the second adjustable baffle 3-2 has a rectangular cross-sectional shape.

[0042] This configuration forces the outer NH3 airflow to change direction after passing through the contraction structure, creating radial velocity that promotes mixing and ignition with the central pulverized coal airflow. It also facilitates sliding within the return annular cavity 8, allowing adjustment of the covering area of ​​the openings 3-4. Other components and connections are identical to any one of the specific embodiments one through four.

[0043] Specific Implementation Method Six: Combination Figures 1 to 2 This embodiment further includes a reflux generator 10, which is installed on the right end face of the pipe body 3-3. This arrangement facilitates the provision of space for a negative pressure zone, promoting the recirculation of high-temperature flue gas. Other components and connections are the same as in any of the specific embodiments one through five.

[0044] Specific implementation method seven: Combination Figures 1 to 2 In this embodiment, the opening diameters of the inner secondary air duct 4 and the outer secondary air duct 5 gradually increase. This arrangement enables the formation of a stable vortex during combustion, helping to maintain flame stability. Other components and connections are the same as in any of embodiments one through six.

[0045] Specific implementation method eight: Combination Figures 1 to 2 This embodiment describes a method in which multiple fixed support blocks 11 are provided between the third tube 3-5 and the tube 3-3.

[0046] This arrangement facilitates support between the third tube 3-5 and the tube 3-3. The number of fixed support blocks 11 is preferably four or six, and the multiple fixed support blocks 11 are installed in a circular array. Other components and connections are the same as in any of the specific embodiments one to seven.

[0047] Specific Implementation Method Nine: Combining Figures 1 to 2 In this embodiment, the tangential blade 6 and the second axial blade 7 are mounted on the same radial plane. This arrangement allows for adjustment of the swirling intensity of the airflow at the channel outlet by adjusting the blade angle. Other components and connections are the same as in any of the specific embodiments one through eight.

[0048] Specific Implementation Method Ten: Combining Figures 1 to 2In this embodiment, the area formed between the outer side of the first adjustable baffle 3-1 and the inner wall of the tube 3-3 is a low-pressure zone. With this configuration, under the influence of pressure difference, the high-temperature flue gas from the burner outlet flows through the reflux annular cavity to the root of the outer NH3 channel. Other components and connections are the same as in any of embodiments one through nine.

[0049] Combination Figures 1 to 3 Explanation of the working principle of this invention:

[0050] The working principle of the entire combustion technology is as follows: Figure 1 As shown, the combustion organization method is as follows Figures 2-3 As shown, the working principle of a low-carbon, low-NOx swirl combustion technology based on ammonia-coal co-combustion, suitable for flexible peak-shaving processes, is as follows: A constricted-mouth structure is used to create a high-speed jet of primary air and outer NH3 within the burner, forming a low-pressure zone at the jet root. Under the pressure difference, the high-temperature flue gas from the burner outlet flows through the recirculation annulus to the root of the outer NH3 channel. The high-temperature recirculation, under the influence of the high-speed NH3 jet, mixes with the outer NH3 gas flow, initiating heating of the outer NH3 gas flow. After the outer NH3 gas flow is heated to above the ignition point (650℃), oxygen is supplied by the inner primary air, and stable combustion begins. The recirculation power of the high-temperature flue gas is provided by the high-speed jet under the constricted-mouth structure, independent of the overall combustion conditions in the furnace; therefore, its self-heating and stable combustion capabilities are outstanding. Subsequently:

[0051] (1) The outer layer NH3 gas flow and the primary air-coal gas flow are continuously mixed. Under the exothermic effect of the combustion of the outer layer NH3, the mixed gas flow heats up and eventually ignites the coal powder in the primary air. The primary air (coal powder) gas flow is then attracted by the high-speed central NH3 gas flow, and the primary air (coal powder) and the central NH3 gas flow diffuse and mix, eventually igniting the central NH3. The gradual mixed combustion principle of staged heating (ignition) from outer layer ammonia → middle layer coal → central ammonia under this technology further enhances its stable combustion capability.

[0052] (2) Low NOx formation principle

[0053] Localized high-temperature flames and oxygen-rich but lean combustion conditions are the main factors contributing to NOx formation. The principle behind this low-NOx formation technology is as follows:

[0054] 1) The high-temperature flue gas flowing to the root of the outer NH3 channel through the reflux annular cavity has a low oxygen content. After the high-temperature flue gas mixes with the outer NH3 and primary air, the oxygen content in the high-temperature zone of the outer NH3 flame is further reduced.

[0055] 2) The primary air volume is designed to be 20-30% of the air required for fuel combustion. The volatiles (CO, H2, CH4 and other combustible gases) formed after the pyrolysis of pulverized coal in the primary air will compete with NH3 for oxygen, inhibiting the rate of NH3 oxidation to NOx.

[0056] 3) The staged combustion method, in which outer ammonia → middle coal → central ammonia are ignited sequentially, elongates the flame, avoids local high-temperature zones, and reduces the NOx formation rate;

[0057] 4) A central recirculation is formed in the outlet zone of the swirl burner. The recirculation zone contains a high content of reducing gases such as CO. Under a reducing atmosphere, the NOx that has been generated will be gradually reduced to N2.

[0058] (3) Flexible control principle of variable load (ammonia dosage)

[0059] Dividing the NH3 channel into a central and outer NH3 channel allows for flexible control of the NH3 flow rate in each channel. Under high-load (high ammonia blending) operating conditions, the NH3 flow rate in the central channel is reduced to prevent excessive central jet flow, which could cause the NH3 gas flow to penetrate the central recirculation zone under the reducing atmosphere at the burner outlet. Under low-load (low ammonia blending) operating conditions, the flow rate in the outer NH3 channel can be appropriately increased to ensure a suitable amount of high-temperature recirculation flue gas and maintain stable combustion.

[0060] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-nitrogen ammonia coal stable combustion swirl burner, comprising a central NH3 pipe (1), wherein NH3 is introduced into the central NH3 pipe (1), characterized in that: It also includes a primary air pulverized coal duct (2), an outer NH3 duct (3), an inner secondary air duct (4), an outer secondary air duct (5), tangential blades (6), and a second axial blade (7); The primary air pulverized coal pipe (2) is fitted onto the central NH3 pipe (1), forming a primary air channel between the primary air pulverized coal pipe (2) and the central NH3 pipe (1). The outer NH3 pipe (3) is fitted onto the primary air pulverized coal pipe (2), forming an NH3 channel between the outer NH3 pipe (3) and the primary air pulverized coal pipe (2). The inner secondary air pipe (4) is fitted onto the outer NH3 pipe (3), forming an inner secondary air channel between the inner secondary air pipe (4) and the outer NH3 pipe (3). The outer secondary air pipe (5) is fitted onto the inner secondary air pipe (4), forming an outer secondary air channel between the outer secondary air pipe (5) and the inner secondary air pipe (4). The tangential blade (6) and the second axial blade (7) are respectively installed on the inner secondary air channel and the outer secondary air channel. The inner sides of the primary air pulverized coal pipeline (2) and the outer NH3 pipeline (3) are provided with a constriction structure (9), which realizes sequential ignition and staged combustion through the outer layer ammonia, the middle layer coal and the center ammonia; The closing angle of the primary air pulverized coal pipeline (2) is the same as the closing angle of the outer NH3 pipeline (3); The outer NH3 pipe (3) includes a pipe body (3-3), a third pipe body (3-5), a first adjustable baffle (3-1), and a second adjustable baffle (3-2). Multiple openings (3-4) are evenly distributed on the outer circumference of the pipe body (3-3). The first adjustable baffle (3-1) is installed on the inner end face of the pipe body (3-3) and is parallel to the closing end of the primary air pulverized coal pipe (2). The second adjustable baffle (3-2) is installed on the outer end face of the opening (3-4). The third pipe body (3-5) is fitted on the pipe body (3-3), and a return flow annular cavity (8) is formed between the third pipe body (3-5) and the pipe body (3-3).

2. The low-nitrogen ammonia coal stable combustion swirl burner according to claim 1, characterized in that: Both the first adjustable baffle (3-1) and the second adjustable baffle (3-2) are annular baffles.

3. The low-nitrogen ammonia coal stable combustion swirl burner according to claim 2, characterized in that: The cross-sectional shape of the first adjustable baffle (3-1) is a right triangle, and the cross-sectional shape of the second adjustable baffle (3-2) is a rectangle.

4. A low-nitrogen ammonia coal stable combustion swirl burner according to claim 3, characterized in that: It also includes a reflux generator (10), which is installed on the right end face of the tube body (3-3).

5. A low-nitrogen ammonia coal stable combustion swirl burner according to claim 4, characterized in that: The diameter of the opening side of the internal secondary air duct (4) and the external secondary air duct (5) gradually increases.

6. A low-nitrogen ammonia coal stable combustion swirl burner according to claim 5, characterized in that: A gap is left between the tube body (3-3) and the third tube body (3-5).

7. A low-nitrogen ammonia coal stable combustion swirl burner according to claim 6, characterized in that: The tangential blade (6) and the second axial blade (7) are mounted on the same radial plane.

8. A low-nitrogen ammonia coal stable combustion swirl burner according to claim 7, characterized in that: The area formed between the outer side of the first adjustable baffle (3-1) and the inner wall of the pipe body (3-3) is a low-pressure area.

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